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MINING  AND  SCIENTIFIC  PRESS 


STAND AED    METHODS 

_~ 

OF 

CHEMICAL  ANALYSIS 

A  MANUAL  OF  ANALYTICAL  METHODS  AND 

GENERAL  REFERENCE  FOR  THE 

ANALYTICAL  CHEMIST  AND  FOR 

THE  ADVANCED  STUDENT 

EDITED  BY 

WILFRED  W.  SCOTT 

Industrial  Research  and  Chemical  Engineering,  General  Chemical 
Company;  Formerly  Chief  Chemistt  Baldwin  Locomotive  Works. 
Author  of  "Qualitative  Chemical  Analysis;  A  Laboratory  Guide." 

IN  COLLABORATION  WITH 

H.  A.  BAKER  D.  K.  FRENCH  R.  K.  MEADE 

L.  E.  BARTON  H.  A.  GARDNER  J.  C.  OLSEN 

F.  G.  BREYER  A.  H  .GILL  R.  S.  OWENS 

B.  S.  CLARK  F.  E.  HALE  W.  L.  SAVELL 

W.  G.  DERBY  R.  E.  HICKMAN  J.  A.  8CHAEFFER 

W.  F.  DOERFLINGER  W.  B.  HICKS 

142  ILLUSTRATIONS  AND  3   COLORED  PLATES 


SECOND   EDITION,  REVISED 
SIXTH  THOUSAND 


f  Phnrmaoy 


NEW  YORK 

D.  VAN  NOSTRAND   COMPANY 

EIGHT  WARREN  STREET 
1920 


Copyright.  1917.  by 
D.  VAN  NOSTRAND  COMPAN\ 


Printed  in  the  United  States  of  America 


THIS  BOOK  IS  AFFECTIONATELY  DEDICATED 
TO  MY  FATHER, 

^tvtt,  P 


421SS 


«     PREFACE  TO   FIRST  EDITION 

THIS  book  is  a  compilation  of  carefully  selected  methods  of 
technical  analysis  that  have  proven  of  practical  value  to  the 
professional  chemist.  The  subjects  have  been  presented  with 
sufficient  detail  to  enable  one  with  an  elementary  knowledge  of 
analytical  processes  to  follow  the  directions;  on  the  other  hand, 
lengthy  exposition,  theoretical  dissertation  and  experimental  data 
are  purposely  avoided,  in  order  to  include  a  large  amount  of  in- 
formation in  a  compact,  accessible  form.  References  to  original 
papers  are  given  when  deemed  advisable. 

For  methodical  arrangement  the  material  is  grouped  under 
three  major  divisions — Part  I.  Quantitative  determination  of  the 
elements.  Part  II.  Special  subjects.  Part  III.  Tables  of  infor- 
mation. 

In  the  first  division  the  elements  are  generally  taken  up  in 
their  alphabetical  order,  each  chapter  being  fairly  complete  in 
itself,  cross-references  being  given  to  certain  details  included 
elsewhere  to  avoid  repetition.  For  example,  the  complete  di- 
rections for  separation  of  the  halogens  are  given  in  the  chapter 
on  chlorine,  and  references  to  these  details  are  given  in  the  chap- 
ters dealing  with  the  other  members  of  this  group.  Occasionally 
it  has  been  deemed  advisable  to  place  several  related  elements 
together  in  the  same  chapter. 

Each  chapter  on  the  elements  is  generally  arranged  according 
to  the  following  outline: 

Physical  Properties.  Atomic  weight;  specific  gravity;  melting- 
point;  boiling-point;  oxides. 

Detection.  Characteristic  reactions  leading  to  the  recognition 
of  the  element. 

Estimation.  The  subject  is  introduced  with  such  information 
as  is  useful  to  the  analyst. 

Preparation  and  Solution  of  the  Samples.  Here  directions  are 
given  for  the  preparation  and  decomposition  of  characteristic 


vi  PREFACE 

materials  in  which  the  element  occurs.  Recommendations  to  the 
best  procedures  are  included  to  assist  the  analyst  in  his  choice. 

Separations.  This  section  is  devoted  to  procedures  for  the 
removal  of  substances,  commonly  occurring  with  the  element, 
that  may  interfere  with  its  estimation.  In  the  absence  of  such 
substances,  or  in  case  methods  are  to  be  followed  by  which  a  direct 
estimation  of  the  element  may  be  made  in  the  presence  of  these 
substances,  this  section  on  separations  may  be  omitted  in  the 
course  of  analysis.  Here  the  discretion  of  the  chemist  is  necessary, 
and  some  knowledge  of  the  substance  examined  essential. 

Methods.  The  procedures  are  grouped  under  gravimetric  and 
volumetric  methods.  Several  processes  are  generally  given  to 
afford  the  opportunity  of  selection  for  particular  cases  and  for 
economical  reasons  where  special  reagents  may  not  be  available. 

In  many  of  the  chapters  methods  for  determining  traces  of 
the  element  are  given,  and  the  subjects  are  concluded  by  typical 
examples  of  complete  analysis  of  substances  containing  the  elements. 

The  titles  to  the  procedures  generally  give  a  clue  to  the  processes. 
Names  of  originators  are  occasionally  retained  where  common 
usage  makes  the  methods  generally  known  by  these. 

Although  the  combined  acid  radicals  are  taken  up  with  the 
elements  to  which  they  may  be  assigned,  a  chapter  is  devoted  to 
the  more  important  of  the  acids  in  their  free  state,  and  is  placed 
with  the  other  special  subjects  in  the  second  division  of  the  book. 
Here  are  found  chapters  on  water,  paint,  oil,  alloys,  coal,  cement, 
gas,  and  such  subjects  as  are  best  classed  in  sections  apart  from 
simple  substances  dealt  with  in  the  first  portion  of  the  work. 

The  last  portion  of  the  book  is  devoted  to  tables  of  the  more 
important  arithmetical  operations.  These  are  designed  to  assist 
the  analyst  to  greater  accuracy  of  calculations,  as  well  as  to  relieve 
him  of  needless  expenditure  of  time  and  energy. 

The  material  herein  included  has  been  carefully  selected,  an 
effort  having  been  made  to  obtain  the  more  trustworthy  method? 
that  will  meet  the  general  needs  of  technical  chemists.  For  guid- 
ance in  making  certain  selections  and  for  information  of  value  to  our 
work,  we  are  indebted  to  the  standard  works  of  K.  M.  Fresenius, 
F.  A.  Gooch,  E.  P.  Treadwell  and  W.  T.  Hall,  A.  H.  Low,  J.  W. 
Mellor,  J.  C.  Olsen,  F.  A.  Sutton,  E.  Thorpe  and  others,  as  well  as 


PREFACE  vii 

» 

to  the  current  chemical  literature.  All  unpublished  procedures 
appearing  in  our  book  have  undergone  thorough  test  and  have 
proven  worthy  of  a  place  among  standard  methods.  The  col- 
laborators are  aware  of  the  limitations  of  analytical  processes  and 
will  gladly  welcome  criticism  of  the  procedures,  and  suggestions 
that  will  enable  us  to  improve  the  work. 

The  editor  wishes  to  acknowledge  his  indebtedness  to .  those 
cooperating  with  him  in  the  compilation  of  this  volume.  The  names 
of  these  appear  in  the  table  of  contents,  as  well  as  on  the  title 
pages  of  their  respective  chapters.  For  useful  suggestions  and 
information  of  value  to  this  work,  or  for  assistance  in  reviewing 
manuscript  or  proof  we  express  our  appreciation  of  Dr.  F.  A. 
Gooch,  Mr.  W.  C.  Ferguson,  Mr.  W.  S.  Allen,  Dr.  Allen  Rogers, 
Mr.  L.  E.  Barton,  Mr.  T.  T.  Gray,  Mr.  W.  G.  Derby,  Mr.  A.  W. 
Betts,  Mr.  N.  F.  Harriman,  Dr.  E.  Bedtel,  Mr.  W.  F.  Doer- 
flinger,  Mr.  J.  M.  Cratty,  Mr.  B.  S.  Clark  and  others,  mention  of 
whom  is  made  in  the  text.  We  would  make  special  mention  of 
Dr.  John  C.  Olsen  for  his  review  of  the  entire  manuscript  and 
ior  many  valuable  suggestions,  which  are  incorporated  in  the 
work.  We  wish  to  express  our  high  appreciation  of  Dr.  Frank 
E.  Hale  for  his  invaluable  assistance  in  reviewing  proof  and  for 
his  contributions. 

A  list  of  the  majority  of  publications  consulted  is  given  in 
alphabetical  order  in  the  appendix  of  this  volume.  Reference  to 
these  authorities  will  be  found  throughout  the  book. 

W.  W.  SCOTT. 

NEW  YORK  CITY, 
January,  1917. 


PREFACE  TO   SECOND   EDITION 

THE  demand  for  a  second  edition  of  Standard  Methods  of 
Chemical  Analysis  within  six  months  of  the  issue  of  the  first  has 
made  it  impractical  to  attempt  any  drastic  revision  of  the  work. 
A  few  errors  appearing  in  the  first  edition  have  been  corrected  and 
some  changes  made  in  descriptive  portions  of  certain  methods. 
Several  useful  tables  have  been  added  to  the  data  in  Part  III. 

The  Editor  trusts  that  the  book  wi.l  continue  to  find  favor  with 
those  desiring  reliable  information  in  the  field  of  its  survey. 

WILFRED  W.  SCOTT. 
GRANTWOOD,  N.  J., 
September,  1917. 


PREFACE  TO  SECOND  EDITION,  REVISED 


THE  approval  of  the  chemical  fraternity  of  the  selection  and 
arrangement  of  the  material  in  this  volume  is  exceedingly  gratifying  to 
the  contributors.  In  this  edition  a  few  slight  changes  and  additions 
have  been  made,  notably  in  the  chapters  on  Cement,  Acids,  and  Alloys. 
The  Editor  wishes  to  express  his  indebtedness  to  those  who  have  kindly 
called  his  attention  to  misprints  in  the  second  edition.  He  would  speci- 
ally mention  Mr.  L.  E.  Salas  for  his  careful  review  of  the  entire  work 
and  his  many  helpful  suggestions,  and  Mr.  W.  B.  Price  for  his  revision 
of  the  chapter  on  Alloys. 

W.  W.  SCOTT. 

GRANTWOOD,  N.  J., 
June,  1918. 


vffi 


CONTENTS 

PART  I 

ALUMINUM 
WILFRED  W.  SCOTT,  M.  A. 

Research  Chemist,  General  Chemical  Company,  Formerly  Chief  Chemist,  Baldwin 
Locomotive  Works;  Professor  of  Chemistry,  Morningside  College.  Author  of 
"  Qualitative  Chemical  Analysis;  a  Laboratory  Guide." 

Detection — with  ammonium  hydroxide,  with  sodium  thiosulphate,  3.  Estima- 
tion, 3.  Preparation  and  solution  of  the  sample — general  procedure  for  ores,  sulphide 
ores,  carbonate  fusion,  bisulphate  fusion,  extraction  of  aluminum-bearing  ores  for 
commercial  valuation,  metallic  aluminum  and  its  alloys,  3-5.  Separation  of  aluminum 
from — silica,  iron,  phosphoric  acid,  chromium,  manganese,  cobalt,  nickel,  zinc,  alkaline 
earths,  alkalies,  titanium,  uranium,  glucinum,  5,  6.  Gravimetric  methods — deter- 
mination of  aluminum  by  hydrolysis  with  ammonium  hydroxide;  hydrolysis  with 
sodium  thiosulphate;  precipitation  as  phosphate;  precipitation  as  aluminum  chloride 
10.  Volumetric  methods — determination  of  combined  alumina  by  alkali  titration; 
free  alumina  or  free  acid  in  aluminum  salts — potassium  fluoride  method,  11-13.  Min- 
ute amounts  of  aluminum  by  Atack's  Alizarine  S  method,  14.  Bauxite  analysis, 
14,  15.  Aluminum  in  iron  and  steel,  16.  Analysis  of  metallic  aluminum,  standard 
method  of  the  Aluminum  Company  of  America,  17,  18. 

ANTIMONY 

WILFRED  W.  SCOTT 

Detection — as  sulphide,  by  hydrolysis,  in  minerals,  traces;  distinction  between 
antimonous  and  antimonic  salts,  18.  Estimation,  19.  Preparation  and  solution  of 
the  sample — sulphide  ores,  low  grade  oxides,  speisses,  slags,  mattes,  alloys,  hard  lead 
rubber  goods,  19-21.  Separations  of  antimony  from — members  of  subsequent  groups; 
from  mercury,  copper,  bismuth,  cadmium,  lead,  arsenic  and  tin,  21-23.  Gravimetric 
methods — determination  as  antimony  trisulphide;  as  metal  by  electrolysis,  23,  24. 
Antimony  in  solder  and  in  alloys  with  tin  and  lead,  25.  Volumetric  methods — de- 
termination with  potassium  bromate;  with  potassium  iodide;  by  oxidation  with 
iodine;  permanganate  method;  indirect  evolution  method,  25-28.  Determination 
of  small  amounts  of  antimony,  28. 

ARSENIC 

WILFRED  W.  SCOTT 

Detection — with  hydrogen  sulphide,  volatility  of  arsenous  chloride,  traces;  distinc- 
tion between  arsenates  and  arsenites,  30.  Estimation,  30.  Preparation  and  solution  of 
the  sample — pyrites  ore,  arseno-pyrites,  arsenous  oxide,  arsenic  acid,  alkali  arsenates; 
arsenic  in  sulphuric  acid,  in  hydrochloric  acid,  in  organic  matter;  lead  arsenate; 

ix 


x  CONTENTS 

zinc  arsenite;  water  soluble  arsenic  in  insecticides;  arsenic  in  mispickel;  in  iron;  in 
copper,  30-33.  Separations — isolation  of  arsenic  by  distillation;  separation  as  sul- 
phide from  antimony  and  tin,  etc.,  33-36.  Gravimetric  methods — determination  as 
trisulphide;  as  magnesium  pyroarsenate,  36.  Volumetric  methods — by  oxidation 
with  standard  iodine;  by  precipitation  as  silver  arsenate,  39,  40.  Small  amounts  of 
arsenic  by  the  Gutzeit  method — in  sulphuric,  hydrochloric,  and  nitric  acids;  in  iron, 
pyrites,  cinders,  bauxite,  phosphates,  phosphoric  acid,  salts,  baking  powder,  organic 
matter,  canned  goods,  meats,  etc.,  standard  method  of  the  General  Chemical  Com- 
pany, 40-47.  Analysis  of  commercial  arsenic  (As20a),  47-49. 

BARIUM 

WILFRED  W.  SCOTT 

Detection — as  barium  chromate,  with  calcium  sulphate  or  strontium  sulphate, 
by  precipitation  as  fluosilicate,  flame  test,  spectrum,  50.  Preparation  and  solution 
of  the  sample — ores,  sulphates,  sulphides,  carbonates;  salts  soluble  in  water;  organic 
matter;  insoluble  residue,  50,  51.  Separations — the  alkaline  earths;  introductory, 
sources  of  loss,  preliminary  tests;  separation  from  members  of  previous  groups;  separa- 
tion of  the  alkaline  earths  from  magnesium  and  the  alkalies  by  the  oxalate  and  sul- 
phate methods;  separation  of  the  alkaline  earths  from  each  other,  51-56.  Gravi- 
metric methods — determination  as  chromate;  as  sulphate,  56-58.  Volumetric  methods 
— titration  of  the  barium  salt  solution  with  dichromate;  reduction  with  ferrous  salt 
and  titration  with  permanganate;  potassium  iodide  method;  acid  titration  of  the 
carbonate,  59,  60.  Analysis  of  barytes  and  witherite;  commercial  valuation  of  the  ores, 
59-61. 

BISMUTH 

WILFRED  W.  SCOTT 

Detection — as  bismuth  oxychloride,  and  by  reduction,  62.  Estimation,  62.  Prep- 
aration and  solution  of  the  sample — ores,  cinders;  alloys,  bearing  metal,  lead  bullion 
and  refined  lead,  62,  63.  Separations  from — members  of  the  ammonium  hydroxide, 
sulphide  and  carbonate  groups  and  from  the  alkalies;  separation  from  arsenic,  anti- 
mony, tin,  molybdenum,  tellurium  and  selenium;  mercury,  lead,  copper  and  cadmium, 
64,  65.  Gravimetric  methods — by  precipitation  and  determination  as  the  basic 
chloride,  BiOCl;  as  the  oxide,  Bi203,  (a)  by  precipitation  as  the  basic  nitrate,  (6)  sub- 
carbonate,  (c)  hydroxide,  determination  as  bismuth  sulphide,  Bi2S3;  as  metallic  bis- 
muth by  reduction  with  potassium  cyanide;  by  deposition  of  the  metal  electrolytically, 
65-68.  Volumetric  methods — by  titration  of  the  oxalate  with  permanganate;  cin- 
chonine  potassium  iodide  colorimetric  method;  bismuth  iodide  colon' metric  com- 
parison, 68-70. 

BORON 
WILFRED  W.  SCOTT 

Detection — flame  test,  borax  bead  and  turmeric  tests,  71.  Estimation,  71.  Prep- 
aration and  solution  of  the  sample — boric  acid  in  silicates  and  enamels;  boronatro- 
calcite,  borocalcite,  boracite,  calcium  borate;  borax  and  boric  acid;  boric  acid  in  min- 
eral water;  in  carbonates;  in  foods — milk,  butter,  meat,  etc.,  72,  73.  Gravimetric 
methods — distillation  of  methyl  borate  and  fixation  with  lime,  74,  75.  Volumetric 
methods — titration  of  boric  acid  in  presence  of  mannitol  or  glycerole  in  evaluation  of 
borax  or  boric  acid.  Robin's  test  for  traces,  76,  77. 


CONTENTS  xi 

BROMINE 

WILFRED  W.  SCOTT 

Detection— by  silver  nitrate,  by  absorption  in  carbon  tetrachloride  or  disulphide, 
by  magfenta  test,  bromates,  78.  Estimation,  79.  Preparation  and  solution  of  the  sam- 
ple—bromides, bromine  in  organic  matter,  79.  Separation  of  bromine  from  the  heavy 
metals,  from  silver,  cyanides,  chlorine  and  iodine,  79,  80.  Gravimetric  methods- 
precipitation  as  silver  bromides,  (1)  hydrobromic  acid  and  bromides  of  the  alkaline 
earths  and  alkalies.  (2)  treatment  in  presence  of  heavy  metals,  80.  Volumetric 
methods— determination  of  free  bromine  with  potassium  iodide;  soluble  bromides 
by  chlorine  method,  Volhard's  method;  traces  of  bromine,  80-82.  Arsenous  acid 
method  for  bromates,  82.  Analysis  of  crude  potassium  bromide  and  commercial 
bromine,  82,  83. 

CADMIUM 

WILFRED  W.  SCOTT 

Detection — as  cadmium  sulphide,  blowpipe  test  for,  84.  Estimation,  84.  Prep- 
aration and  solution  of  the  sample — sulphides,  treatment  in  presence  of  lead,  car- 
bonates, alloys,  84,  85.  Separations  from— silica,  ammonium  sulphide  group,  alkaline 
earths  and  alkalies,  separation  from  lead,  bismuth,  mercury,  copper,  arsenic,  anti- 
mony and  tin,  85,  86.  Gravimetric  methods — determination  as  sulphate;  electro- 
lytic method,  86,  87.  Volumetric  determination  by  titration  with  standard  iodine 
solution,  87. 

CALCIUM 

WILFRED  W.  SCOTT 

Detection — as  oxalate,  flame  test,  spectrum  of  calcium,  88.  Estimation  and 
occurrence,  88.  Preparation  and  solution  of  the  sample — limestone,  dolomite,  mag- 
nesite,  cement,  lime,  gypsum,  Plaster  of  Paris,  sulphates,  silicates,  chlorides,  nitrates 
and  other  water  soluble  salts,  sulphides,  pyrites  ore,  89.  Separation  of  calcium  from — 
silica,  iron,  alumina,  copper,  nickel,  cobalt,  manganese,  zinc,  barium,  strontium  and 
the  alkalies,  treatment  in  presence  of  phosphates  of  iron  and  aluminum,  89,  90.  Gravi- 
metric methods — precipitation  as  calcium  oxalate;  other  methods,  91-92.  Volumetric 
method  by  titration  of  the  oxalate  with  standard  potassium  permanganate  solution,  93. 


CARBON 

WILFRED  W.  SCOTT 

Detection — element,  carbon  dioxide  in  carbonates  and  in  gas,  free  carbonic  acid 
in  water,  distinction  between  carbonates  and  bicarbonates,  carbon  monoxide,  93. 
Estimation,  94.  Preparation  of  the  sample — iron,  steel  and  alloys;  organic  matter; 
carbonates  and  bicarbonates,  94.  Separation  of  carbon  from  other  substances;  separa- 
tion from  iron  by  the  cupric  potassium  chloride  method,  94,  95.  Gravimetric  method — 
combustion  furnaces,  types  of  absorption  apparatus,  general  procedure  for  determin- 
ing carbon  by  combustion,  95-99,  100.  Graphitic  carbon  in  iron  and  steel,  99,  100. 
Combined  carbon,  100,  101.  Determination  of  carbon  in  organic  substances— organic 
matter  free  of  nitrogen,  halogens,  sulphur  and  the  metals,  101;  carbon  and  hydrogen 


xii  CONTENTS 

in  nitrogenous  substances,  102;  organic  substances  containing  halogens,  102;  wet 
combustion  process,  102,  103.  Determination  of  carbon  dioxide  in  carbonates — 
gravimetric,  103-107.  Residual  and  available  carbon  dioxide  in  baking  powder,  105- 
106.  Determination  of  carbon  dioxide  by  measuring  the  gas,  105  (107,  reference). 
Determination  by  loss  of  weight,  106.  Volumetric  methods,  total  carbon  by  barium 
hydroxide  absorption,  107.  Direct  colorimetric  method  for  determining  carbon  in 
iron  and  steel,  108-110.  Analysis  of  graphite,  110.  Volumetric  determination  of 
hydrocyanic  acid  in  soluble  cyanides,  110,  111. 

CERIUM  AND  OTHER  RARE  EARTHS 

R.  STUART  OWENS 
Research  Chemist,  New  York  City 

Members  of  the  rare  earth  group — atomic  weights,  specific  gravities,  melting- 
points,  oxides.  Detection  of  cerium,  lanthanum,  praseodymium,  neodymium,  scan- 
dium, ytterbium  and  erbium,  112,  113.  Estimation — occurrence,  113.  Preparation 
and  solution  of  the  sample,  114.  Separations — rare  earths  from  iron,  aluminum, 
thorium,  calcium,  magnesium;  separation  of  scandium  from  yttrium,  yttrium  group, 
separation  of  praseodymium,  neodymium,  lanthanum  and  samarium  from  each  other, 
114,  115.  Gravimetric  estimations,  115.  Volumetric  method  for  the  determination 
of  cerium.  Determination  of  cerium  in  Welsbach  mantles,  colorimetric  method,  116. 
Separation  of  the  rare  earth  oxalates  (outline  table),  117. 

CHLORINE 

WILFRED  W.  SCOTT 
Research  Chemis!,  General  Chemical  Company 

WM.    F.    DOERFLINGER 

Chief  Chemist,  Perry-Austin  Manufacturing  Company 

Detection — free  chlorine,  chlorides  by  silver  nitrate  test,  free  hydrochloric  acid, 
detection  of  chlorine  in  presence  of  cyanate,  cyanide,  thiocyanate,  bromide,  iodide, 
chlorate.  Test  for  hypochlorite,  chlorite,  chlorate,  perchlorate,  118,  119.  Estimation 
— occurrence,  119.  Preparation  and  solution  of  the  sample — water-soluble  chlorides, 
water- insoluble  chlorides,  silver  chloride,  chlorine  in  rocks,  free  chlorine,  chlorine  in 
ores  and  cinders,  119,  120.  Determination  of  halogens  in  organic  compounds — Carius 
method,  121;  lime  method,  122;  sodium  peroxide  method,  122.  Separations — chlorine 
and  the  halides  from  the  heavy  metals,  the  halides  from  silver  and  stiver  cyanide; 
separation  of  the  halides  from  one  another,  chlorine  from  iodine,  and  from  bromine 
and  iodine,  123,  124.  Gravimetric  method — determination  of  chloride  by  precipita- 
tion as  silver  salt,  124.  Volumetric  methods — silver  thiocyanate  ferric  alum  method 
of  Volhard,  silver  chromate  method  of  Mohr,  volumetric  method  for  determination  of 
free  chlorine,  125-127.  Determination  of  hypochlorous  acid  in  presence  of  chlorine, 
127.  Gravimetric  method  for  determination  of  chloric  acid,  128.  Gravimetric  deter- 
mination of  perchloric  acid,  128.  Determination  of  chlorates  and  perchlorates  in 
presence  of  one  another,  129.  Determination  of  hydrochloric,  chloric,  and  per- 
chloric acids  in  presence  of  one  another,  129.  Estimation  of  chlorine,  bromine  and 
iodine  in  presence  of  each  other,  130.  Evaluation  of  bleaching  powder,  chloride  of 
lime,  for  available  chlorine,  130. 


CONTENTS  xiii 

CHROMIUM 

WILFRED  W.  SCOTT 

Detection — test  with  barium  salt,  hydrogen  peroxide,  reducing  agents,  ether, 
diphenyl  carbazide,  132.  Estimation,  132.  Preparation  and  solution  of  the  sample- 
general  procedures  for  decomposition  of  refractory  materials,  special  procedures— high 
silica  ores,  chrome  iron  ores,  iron  and  steel,  133,  134.  Separations — chromium  from 
iron  and  aluminum,  134.  Gravimetric  methods — precipitation  of  chromic  hydroxide 
and  ignition  to  Cr2O3,  determination  as  barium  chromate,  135,  136.  Volumetric 
methods — potassium  iodide  method,  procedure  by  reduction  with  ferrous  salts,  137-138. 
Determination  of  small  amounts  of  chromium,  138. 

COBALT 

W.  L.  SAVELL,  Ph.D. 

Research  Chemist,  Doloro  Mining  and  Reduction  Company 

Detection — general  procedure,  potassium  sulphocyanate,  potassium  nitrite,  140. 
Estimation,  141.  Preparation  and  solution  of  the  sample — general  procedure  for 
ores,  cobalt  oxides,  metallic  cobalt,  nickel  and  cobalt  alloys,  141.  Separations — 
ammonium  sulphide  group  from  hydrogen  sulphide,  ammonium  sulphide  group  from 
the  alkalies,  cobalt  and  nickel  from  manganese,  cobalt  from  nickel,  cobalt  from  zinc, 
142.  Gravimetric  methods — precipitation  of  cobalt  with  potassium  nitrite,  nitroso- 
beta-naphthol  method,  electrolytic  deposition  of  metallic  cobalt,  143-145.  Deter- 
mination of  cobalt  in  cobalt  oxide,  145.  Cobalt  in  the  commercial  metal  and  in  ferro- 
cobalt,  146.  Cobalt  in  metallic  nickel,  146.  Cobalt  in  ores  and  in  enamels,  147. 
Determination  of  cobalt  in  steel,  148. 

COPPER 

WILFRED  W.  SCOTT 
Research  Chemist,  General  Chemical  Company 

WALLACE  G.  DERBY 

Research  Chemist,  Nichols  Copper  Company 

Detection — general  procedure,  flame  test,  wet  tests,  hydrogen  sulphide  test,  other 
methods,  149.  Estimation — occurrence,  149.  Preparation  and  solution  of  the  sam- 
ple— solubilities,  decomposition  of  copper  ores,  sulphide  ores,  copper  pyrites,  copper 
glance,  iron  pyrites,  matte,  oxidized  ores,  oxides,  treatment  of  matte  slag,  metals, 
iron  ores  and  iron  ore  briquettes,  steel,  cast  iron  and  alloy  steels,  150-153.  Separa- 
tions— precipitation  of  copper  as  sulphocyanate,  separation  of  copper  by  precipitation 
in  metallic  form  by  a  more  positive  element,  separation  from  members  of  the  am- 
monium sulphide  and  subsequent  groups;  removal  of  silver,  removal  of  bismuth,  lead, 
mercury,  arsenic,  antimony  and  tin;  separation  from  cadmium,  153-155.  Gravi- 
metric methods — Deposition  of  metallic  copper  by  electrolysis — introduction.  Rapid 
methods — solenoid  method  of  Heath,  deposition  from  nitric  acid  solution,  deposition 
form  ammoniacal  solution.  Slow  methods — electrolytic  determination  of  copper  in 
blister  copper,  standard  procedure  of  Nichols  Copper  Compa:  y,  large  portion  and 
small  portion  methods,  traces  of  copper  in  the  electrolyte,  notes  and  precautions  for 
the  electrolytic  deposition  of  copper,  155-162.  Other  methods— determination  as 
cuprous  sulphocyanate,  determination  as  copper  oxide,  162.  Volumetric  methods 


xiv  CONTENTS 

for  determining  copper — potassium  iodide  method,  potassium  cyanide  method, 
163-165.  Colorimetric  determination  of  small  amounts  of  copper — potassium  ethyl 
xanthate  method,  ferrocyanide  method,  ammonia  method,  hydrogen  sulphide  method, 
165-167.  Determination  of  impurities  in  blister  copper — bismuth,  iron,  lead,  zinc, 
nickel,  cobalt,  arsenic,  antimony,  selenium,  tellurium,  oxygen,  sulphur,  phosphorus, 
167-173.  Determination  of  copper  in  refined  copper,  173.  Chlorine  in  cement 
copper  and  copper  ores,  174.  Copper  in  blue  vitriol,  175.  Copper  and  lead  deter- 
mination in  brass,  175. 

FLUORINE 

WILFRED  W.  SCOTT 

Detection — etching  test,  hanging  drop  test,  black  filter  paper  test,  176-178.  Esti- 
mation— occurrence,  178.  Preparation  and  solution  of  the  sample — solubilities,  or- 
ganic substances,  silicious  ores  and  slags,  calcium  fluoride,  soluble  fluorides,  hydro- 
fluoric acid,  fluorspar,  178,  179.  Separations — removal  of  silicic  acid  from  fluorides, 
separation  of  hydrofluoric  and  phosphoric  acids,  separation  of  hydrofluoric  from 
hydrochloric  and  boric  acids,  179,  180.  Gravimetric  methods — precipitation  as 
calcium  fluoride,  as  lead  chlorofluoride,  180,  181.  Volumetric  methods — Offerman's 
method,  ferric  chloride  method,  Steiger  and  Merwin  colorimetric  method,  182-186. 
Valuation  of  fluorspar,  standard  method  of  the  Fairview  Fluorspar  and  Lead  Com- 
pany, 186.  Analysis  of  sodium  fluoride,  187.  Determination  of  traces  of  fluo- 
rine, 188. 

GLUCINUM    (BERYLLIUM) 

WILFRED  W.  SCOTT 

Detection,  189.  Estimation — occurrence,  189.  Separations — removal  of  silica 
and  of  the  hydrogen  sulphide  group,  separation  of  glucinum  from  iron,  manganese, 
zirconium,  yttrium,  aluminum,  chromium,  iron,  190.  Gravimetric  determination  of 
glucinum,  190,  191. 

GOLD 

WALLACE  G.  DERBY,  M.S. 
Research  Chemist,  Nichols  Copper  Company 

Detection  of  gold  in  alloys,  test  for  gold  in  minerals,  benzidine  acetate  tests,  phenyl- 
hydrazine  acetate  test,  192, 193.  Estimation — solubility,  193.  Gravimetric  methods — 
wet  gold  assay  of  minerals,  electrolytic  method,  194.  Volumetric  methods — per- 
manganate and  iodide  methods,  195,  196.  Colorimetric  methods — procedures  of 
Prister,  Cassel,  Moir,  197,  198.  Preparation  of  proof  gold,  198. 

IODINE 

WILFRED  W.  SCOTT 

Detection— element,  free  iodine  characteristics,  iodide,  iodate,  200.  Estimation — 
occurrence,  200.  Preparation  and  solution  of  the  sample,  iodides  of  silver,  copper, 
mercury,  lead,  etc.,  iodates,  free  iodine  (commercial  crystals),  iodine  or  iodides  in  water, 
organic  substances,  mineral  phosphates,  200,  201.  Separations — iodine  from  heavy 
metals,  from  bromine  or  from  chlorine,  separation  from  chlorine  and  bromine — palla- 
dous  iodide  method,  202,  203.  Gravimetric  methods — precipitation  of  silver  iodide, 


CONTENTS 


xv 

determination  as  palladous  iodide,  203.  Volumetric  methods — hydriodic  acid  and 
iodides  by  thiosulphate  or  by  arsenite  titration,  decomposition  by  ferric  salts,  decom- 
position with  potassium  iodate,  nitrous  acid  method  of  Fresenius,  hydrogen  peroxide- 
phosphoric  acid  method,  chlorine  method  of  Mohr,  Volhard's  method,  203-207. 
Determination  of  iodates,  periodates,  and  iodates  with  periodates  in  a  mixture,  208, 209. 

IRON 

WILFRED  W.  SCOTT 

Detection — ferric  iron,  hydrochloric  acid  solution,  sulphocyanate,  ferrocyanide, 
salicylic  acid,  sodium  peroxide  tests;  distinction  between  ferrous  and  ferric  salts,  210, 
Estimation — occurrence,  210.  Preparation  and  solution  of  the  sample — solubilities' 
soluble  iron  salts,  sulphide  and  oxide  ores,  iron  ore  briquettes,  silicates,  iron  and  steel, 
211,  212.  Gravimetric  methods — determination  as  oxide,  Fe2O3;  Cupferron  method, 
213,  214.  Volumetric  methods — general  considerations,  by  oxidation,  the  iron  having 
been  reduced — titration  with  potassium  dichromate,  potassium  permanganate,  Jones 
reductor  method,  214-221.  Stannous  chloride  method  for  determining  ferric  iron, 
221.  Colorimetric  methods  for  determining  small  amounts  of  iron — with  sul- 
phocyanate, with  salicylic  acid,  222,  223.  Technical  analysis  of  iron  and  steel — 
with  specifications  of  Baldwin  Locomotive  Works.  Introduction;  preparation  of 
the  sample,  combined  or  carbide  carbon-colorimetric  method,  specifications  for 
combined  carbon;  total  carbon  by  combustion;  graphite  in  iron;  manganese  by 
persulphate  method,  lead  oxide  procedure  of  Deshey,  method  by  U.  S.  Bureau  of 
Standards — manganese  by  the  Bismuth  ate  method;  specifications  for  manganese; 
determination  of  phosphorus  by  the  alkalimetric  and  molybdate  methods;  specifica- 
tions for  phosphorus;  determination  of  sulphur  by  the  evolution  method;  method  by 
the  U.  S.  Bureau  of  Standards;  specifications  for  sulphur  in  iron  and  steel;  determi- 
nation of  silicon,  rapid  foundry  method,  method  by  the  U.  S.  Bureau  of  Standards ;( 
specifications  for  silicon  in  iron  and  steel,  223-232. 

LEAD 

WILFRED  W.  SCOTT 

Detection — hydrochloric  acid  test,  hydrogen  sulphide  test,  confirmation  of  tests, 
233.  Estimation — occurrence,  233.  Preparation  and  solution  of  the  sample — sol- 
ubilities, decomposition  of  ores,  minerals  of  lead,  iron  pyrites,  alloys,  234.  Separations 
— isolation  of  lead  as  sulphate,  separation  from  barium,  isolation  as  lead  chloride, 
ammonium  acetate  extraction  of  lead  from  the  impure  sulphate,  235.  Gravimetric 
methods — determination  of  lead  as  sulphate,  as  chromate,  as  molybdate,  electrolytic 
determination  as  peroxide,  PbO2,  236-238.  Volumetric  methods— ferrocyanide  method, 
molybdate  method,  238-240.  Determination  of  small  amounts  of  lead— gravimetric 
methods — by  ammonium  acetate  extraction,  by  occlusion  with  iron  hydroxide,  Seeker- 
Clayton  method  modified;  colorimetric  estimation,  241-247.  Analysis  of  metallic 
lead,  method  of  the  National  Lead  Company,  modified,  248-252. 

MAGNESIUM 
WILFRED  W.  SCOTT 

Detection — general  procedure,  test  with  baryta  or  lime  water,  253.  Estimation — 
occurrence,  253.  Preparation  and  solution  of  the  sample— solubilities,  general  pro- 


XVI 


CONTENTS 


cedure  for  ores,  254.  Separations — removal  of  members  of  the  hydrogen  sulphide 
group,  ammonium  sulphide  group,  separation  from  the  alkaline  earths,  254.  Gravi- 
metric determination  by  precipitation  as  ammonium  magnesium  phosphate,  255. 
Volumetric  determination  by  titration  of  ammonium  magnesium  phosphate  with  stand- 
ard acid,  256. 

MANGANESE 
WILFRED  W.  SCOTT 

Detection — general  procedure,  manganese  in  soils,  minerals,  vegetables,  etc., 
borax  test,  sodium  carbonate  and  nitrate  tests,  257.  Estimation — occurrence,  257. 
Preparation  and  solution  of  the  sample — solubilities,  decomposition  of  ores,  sulphides, 
slags,  iron  ores,  alloys,  manganese  bronze,  ferro-titanium  alloy,  ferro-chromium, 
metallic  chromium,  ferro-aluminum,  vanadium  alloys,  molybdenum  alloys,  tungsten 
alloys,  silicon  alloys,  iron,  steel  and  pig  iron,  258,  259.  Separations — removal  of  the 
members  of  the  hydrogen  sulphide  group,  separation  of  manganese  from  the  alkaline 
earths  and  the  alkalies,  from  nickel  and  cobalt;  basic  acetate  method  for  removal  of 
iron  and  aluminum;  isolation  of  manganese  as  the  dioxide,  MnO2,  260-262.  Gravi- 
metric method — determination  as  manganese  pyrophosphate,  262.  Volumetric 
methods — bismuthate  method,  procedure  of  Volhard,  ammonium  persulphate  colori- 
metric  method,  oxidation  of  manganese  with  oxides  of  lead,  263-268.  Analysis  of 
spiegel  iron  for  manganese,  268. 

MERCURY 

WILFRED  W.  SCOTT 

Detection — general  procedures,  270.  Estimation — occurrence,  270.  Preparation 
and  solution  of  the  sample — solubilities,  decomposition  of  ores,  270,  271.  Separations 
— removal  of  mercury  in  presence  of  members  of  the  ammonium  sulphide,  ammo- 
nium carbonate  and  soluble  groups;  separation  of  mercury  from  arsenic,  antimony, 
tin,  lead,  bismuth,  copper,  cadmium,  selenium,  tellurium,  organic  substances,  271. 
Gravimetric  methods — precipitation  as  sulphide,  determination  by  electrolysis,  Hollo- 
way- Eschka  process,  272-274.  Volumetric  process  by  Seamon's  method,  274. 

MOLYBDENUM 

WILFRED  W.  SCOTT 

Detection — general  procedure,  sodium  thiosulphate  test,  sulphur  dioxide  test, 
phosphate  test,  detection  in  minerals,  characteristics  of  molybdenite,  275.  Estima- 
tion— occurrence,  275.  Preparation  and  solution  of  the  sample — solubilities,  decom- 
position of  ores,  steel  and  iron,  276.  Separations— molybdenum  from  iron  in  presence 
of  large  amounts  of  iron,  separation  from  the  alkalies,  alkaline  earths,  lead,  copper, 
cadmium,  bismuth,  vanadium,  arsenic,  phosphoric  acid,  titanium  and  tungsten,  276, 
277.  Gravimetric  methods — precipitation  as  lead  molybdate,  determination  as  oxide, 
MoOi  after  precipitating  with  mercurous  oxide,  determination  as  sulphide,  278,  279. 
Volumetric  methods — iodometric  reduction  method,  estimation  by  reduction  with 
Jones  reductor  and  subsequent  permanganate  titration,  determination  of  molybdenum 
and  vanadium  in  a  mixture  of  the  two,  280-282. 


CONTENTS 


xvn 


NICKEL 

W.  L.  SAVELL,  Ph.D. 
Research  Chemist,  Doloro  Mining  and  Reduction  Company 

Detection — general  procedure,  dimethylglyoxime  test,  alpha  benzildioxime  test, 
283.  Estimation,  284.  Preparation  and  solution  of  the  sample,  solubilities,  general 
procedure  for  decomposing  ores,  fusion  methods,  solution  of  metallic  nickel  and  its 
alloys,  284,  285.  Separations — ammonium  sulphide  group  from  hydrogen  sulphide 
and  from  the  alkaline  earths  and  alkalies;  separation  of  nickel  from  cobalt,  manganese, 
zinc,  iron,  aluminum,  chromium,  285,  286.  Gravimetric  methods — precipitation  of 
nickel  by  alpha  benzildioxime,  precipitation  by  dimethylglyoxime,  electrolytic  deposi- 
tion of  nickel,  nickel  in  metallic  nickel,  in  cobalt  and  cobalt  oxide,  286-290.  Volu- 
metric determination  of  nickel  in  alloys,  determination  in  nickel-plating  solutions,  290. 

NITROGEN 

WILFRED  W.  SCOTT 

Detection— organic  nitrogen,  nitrogen  in  gas  mixtures.  Ammonia,  free  and  com- 
bined, tests  for.  Nitric  acid — ferrous  sulphate  test,  diphenylamine  test,  copper  test, 
phenolsulphonic  acid  test.  Detection  of  nitrous  acid — by  acetic  acid,  by  potassium 
permanganate,  291,292.  Estimation — occurrence,  composition  of  air;  free  nitrogen, 
total  nitrogen,  combined  nitrogen,  292,  293.  Preparation  of  the  sample — organic 
substances — method  in  absence  of  nitrates,  method  in  presence  of  nitrates;  soils — 
available  nitrate,  ammonium  salts,  nitrates,  nitrites,  mixtures  of  ammonium  salts, 
nitrates  and  nitrites;  nitric  acid  in  mixed  acid,  293-295.  Separations — ammonia, 
nitric  acid,  removal  of  nitrous,  chromic,  hydrobromic  and  hydriodic  acids,  295,  296, 
Procedures  for  the  determination  of  combined  nitrogen — ammonia — gravimetric  deter- 
mination of  ammonia  by  precipitation  as  ammonium  platinochloride,  296.  Volu- 
metric methods — analysis  of  aqua  ammonia,  combined  ammonia  in  ammonium  salts; 
analysis  of  ammoniacal  liquor — ammonia,  carbon  dioxide,  hydrochloric  acid,  hydro- 
gen sulphide,  sulphuric  acid;  determination  of  traces  of  ammonia  (ref.),  296-299. 
Nitric  acid — gravimetric  determination  by  precipitation  as  nitron  nitrate,  299.  Volu- 
metric methods — direct  estimation  of  nitrates  by  reduction  to  ammonia  by  the  Allen- 
Devarda  method,  300.  Analysis  of  nitrate  of  soda — moisture,  insoluble  matter,  sodium 
sulphate,  iron,  alumina,  lime,  magnesia,  sodium  chloride  and  carbonates,  303,  304. 
Nitric  nitrogen  in  soil  extracts  by  Vamari-Mitscherlich-Devarda  method,  304.  De- 
termination of  nitrogen  of  nitrates  and  nitrites  by  means  of  the  'nitrometer — general 
procedure,  DuPont  nitrometer  method,  305-309.  Determination  of  nitric  acid  in 
oleum  by  DuPont  nitrometer  method,  309.  Combined  nitric  acid  (reference  to  ferrous 
sulphate  method),  209. 

PHOSPHORUS 

WILFRED  W.  SCOTT 

Detection — element,  acids — hypophosphorous,  phosphorous,  orthophosphoric, 
metaphosphoric,  pyrophosphoric,  comparative  table,  310,  311.  Estimation — occur- 
rence, typical  ores,  311.  Preparation  and  solution  of  the  sample — iron  ores,  phosphate 
rocks,  minerals,  iron  and  steel,  ores  with  titanium,  soluble  phosphates,  baking  powder, 
etc.  Precipitation  of  ammonium  phosphomolybdate,  312-314.  Gravimetric  methods 
— direct  weighing  of  ammonium  phosphomolybdate,  determination  as  magnesium 


xviii  CONTENTS 

pyrophosphate;  direct  precipitation  of  magnesium  ammonium  phosphate,  314-316. 
Volumetric  methods — by  titration  with  an  alkali,  by  titration  of  the  reduced  molyb- 
date  with  potassium  permanganate,  316-318.  Phosphate  rock  analysis— (tentative 
methods  of  the  committee  on  standard  methods),  sampling  and  determination  of  mois- 
ture, phosphoric  acid,  iron  and  aluminum  phosphates,  iron,  319-323. 

PLATINUM 

REGINALD  E.  HICKMAN 
Chief  Chemist,  J.  Bishop  and  Company  Platinum  Works 

Detection — general  characteristics,  tests  with  potassium  iodide,  hydrogen  sulphide, 
ammonium  chloride,  potassium  chloride,  ferrous  sulphate,  stannous  chloride,  oxalic 
acid,  sodium  hydroxide  with  glycerine,  formic  acid,  etc.,  324,  325.  Estimation — 
characteristic  substances  containing  platinum,  325.  Preparation  and  solution  of  the 
sample — solubilities,  decomposition  of  ores,  platinum  scrap,  substances  containing 
small  amounts  of  platinum,  325-327.  Separations — platinum  from  gold,  from  iridium, 
palladium,  ruthenium,  rhodium,  osmium,  327,  328.  Gravimetric  methods — weighing 
as  metallic  platinum,  weighing  as  a  salt,  electrolytic  method,  328,  329. 

RARER  ELEMENTS   OF  THE  ALLIED   PLATINUM   METALS 

REGINALD  E.  HICKMAN 

IRIDIUM. — Detection — tests  with  caustic  alkalies,  potassium  chloride,  ammonium 
chloride,  hydrogen  sulphide,  metallic  zinc,  formic  and  sulphurous  acids,  330.  Estima- 
otin.  Preparation  and  solution  of  the  sample,  330.  Separations — iridium  from  plat- 
inum, 331.  Gravimetric  methods,  reduction  with  zinc,  ignition  of  the  ammonium 
salt,  insoluble  residue,  331,  332. 

PALLADIUM. — Detection — tests  with  alkalies,  ammonia,  mercuric  cyanide,  potassium 
iodide,  hydrogen  sulphide,  etc.,  332,  333.  Estimation — Preparation  and  solution 
of  the  sample.  Separations — palladium  from  platinum  and  iridium,  from  silver  and 
gold,  332,  333.  Gravimetric  methods,  333,  334. 

RUTHENIUM. — Detection — potassium  hydroxide,  hydrogen  sulphide,  ammonium 
sulphide,  metallic  zinc,  334.  Estimation — Preparation  and  solution  of  the  sample. 
Separations — ruthenium  from  platinum,  from  iridium,  from  rhodium,  334,  335.  Gravi- 
metric methods,  335. 

RHODIUM. — Detection — tests  with  hydrogen  sulphide,  potassium  hydroxide,  am- 
monium hydroxide,  potassium  nitrite,  reducing  agents,  336.  Estimation — Prepara- 
tion and  solution  of  the  sample.  Separations — rhodium  from  platinum,  from  iridium, 
from  ruthenium,  336,  337.  Gravimetric  methods,  337. 

OSMIUM. — Detection — characteristics,  tests  with  hydrogen  sulphide,  potassium 
hydroxide,  ammonium  hydroxide,  reducing  agents,  337,  338.  Estimation — Prepara- 
tion and  solution  of  the  sample.  Gravimetric  methods,  338. 

Analysis  of  Platinum  Ores,  339.     Assay  Methods  for  Platinum  Ores,  340. 

POTASSIUM,   SODIUM  AND    OTHER  ALKALIES 

W.  B.  HICKS,  Ph.D. 
Assistant  Chemist,  U.  S.  Geological  Survey 

Detection — Sodium,  341;  lithium,  342;  rubidium  and  caesium,  342;  potassium,  341. 
Estimation,  343.  Solution  of  the  sample — procedure  for  rocks  and  other  insoluble 


CONTENTS  xix 

mineral  products,  procedure  for  soils,  fertilizers,  organic  compounds,  ashes  of  plants, 
saline  residues,  soluble  salts  and  brines,  343,  344.  Separations — alkali  metals  from  other 
constituents — hydrogen  sulphide  and  ammonium  sulphide  groups  of  metals;  separa- 
tion from  silica;  from  iron,  alumina,  chromium,  titanium,  uranium,  phosphoric  acid; 
separation  from  sulphates;  from  barium,  calcium,  strontium;  separation  from  iron, 
alumina,  chromium,  barium,  calcium,  strontium,  phosphates,  sulphates,  etc.,  in  one 
operation;  separation  from  boric  acid;  separation  from  magnesium— mercuric  oxide 
method,  barium  hydroxide  method,  ammonium  phosphate  method;  separation  of  the 
alkali  metals  from  one  another — separation  of  sodium  from  potassium;  lithium  from 
sodium  and  potassium;  lithium  and  sodium  from  potassium,  rubidium  and  caesium, 
344-347.  Methods  for  the  determination  of  sodium — as  sodium  chloride,  as  sodium 
sulphate,  difference  method,  348,  349.  Methods  for  the  determination  of  potassium — 
as  chloroplatinate,  modified  chloroplatinate  method,  Lindo-Gladding  method,  per- 
chlorate  method,  other  methods,  349-352.  Determination  of  sodium  and  potassium 
by  indirect  method.  Determination  of  magnesium,  sodium  and  potassium  in  presence 
of  one  another,  352.  Methods  for  determining  lithium — determination  as  lithium 
chloride,  as  lithium  sulphate,  Gooch  method,  Rammelsberg  method,  spectroscopic 
method,  353,  354.  Determination  of  sodium,  potassium,  and  lithium  in  the  presence 
of  one  another.  Determination  of  the  alkalies  in  silicates  by  J.  Lawrence  Smith 
method,  355.  Hydrofluoric  method,  356.  Determination  of  the  alkalies  in  alunite, 
356.  Volumetric  methods,  357. 

SELENIUM   AND   TELLURIUM 

WILFRED  W.  SCOTT 

Detection — general  procedure;  detection  of  selenium — tests  with  sulphuric  and 
hydrochloric  acids,  barium  chloride,  hydrogen  sulphide,  detection  of  tellurium — fusion 
test,  tests  with  hydrogen  sulphide,  potassium  iodide  and  reducing  agents,  358,  359. 
Estimation — occurrence  of  selenium  and  tellurium,  359.  Preparation  and  solution,  of 
the  sample,  selenium  and  tellurium  solubilities,  decomposition  of  ores,  360.  Separa- 
tions— selenium  and  tellurium  from  the  iron  and  zinc  group  metals,  from  alkalies  and 
alkaline  earths,  from  cadmium,  copper  and  bismuth,  separation  from  silver  and  gold, 
separation  of  selenium  from  tellurium  by  direct  precipitation  and  by  distillation 
methods,  260-262.  Estimation  of  the  two  elements  by  the  distillation  separation, 
362,  363.  Gravimetric  methods — determination  of  selenium  by  precipitation  with 
sulphur  dioxide,  potassium  iodide  reduction  method,  precipitation  of  tellurium  by 
sulphur  dioxide,  determination  as  tellurium  dioxide,  264,  265.  Volumetric  methods — 
iodometric  method  for  selenic  and  telluric  acids,  265. 

SILICON 

WILFRED  W.  SCOTT 

Detection,  367.  Estimation — occurrence — solubilities,  367,  368.  Preparation  and 
solution  of  the  sample — general  considerations,  preparation  of  the  substance  for  decom- 
position, general  procedure  for  decomposing  the  material,  silicates  not  decomposed  by 
acids— carbonate  fusion,  fluorides;  special  procedures  for  decomposing  the  sample— 
ferrosilicons,  steels  containing  tungsten,  chromium,  vanadium  and  molybdenum; 
silicon  carbide,  carborundum;  sulphides,  iron  pyrites,  slags  and  roasted  ores,  368-371. 
Procedure  for  determination  of  silicon  and  silica,  372.  Analysis  of  silicate  of  soda, 
373.  Analysis  of  sand,  commercial  valuation,  374. 


xx  CONTENTS 

SILVER 
WALLACE  G.  DERBY 

Research  Chemist,  Nichols  Copper  Company 

Detection — wet  method,  silver  chloride,  characteristics,  sundry  tests,  375,  376. 
Estimation — preliminary  considerations,  solubility,  furnace  methods,  376.  Gravi- 
metric methods — determination  as  silver  chloride,  as  cyanide,  electrolytic  method, 
376,  377.  Volumetric  methods — thiocyanate  procedure  of  Volhard,  Gay-Lussac 
method,  combination  methods,  Denige's  cyanide  method,  miscellaneous  volumetric 
methods,  nephelometric  method,  378-384.  Preparation  of  pure  silver,  384. 

STRONTIUM 

WILFRED  W.  SCOTT 

Detection — sodium  sulphate  test,  flame  test,  spectra,  387.  Estimation — occurrence 
and  uses,  387.  Preparation  and  solution  of  the  sample — solubilities,  388.  Separations 
— strontium  from  magnesium,  alkalies,  calcium  and  barium,  388.  Gravimetric  methods 
— determination  as  sulphate,  carbonate,  oxide,  389.  Volumetric  methods — alkali- 
metric,  indirect  method — chloride  titration  with  silver  nitrate,  389,  390. 

SULPHUR 

WILFRED  W.  SCOTT 

Detection — element;  sulphides,  sulphates,  sulphites;  thiosulphates,  391.  Esti- 
mation— occurrence — element,  sulphur  dioxide,  hydrogen  sulphide,  sulphide  ores, 
sulphate  ores.  Preliminary  considerations,  392.  Preparation  and  solution  of  the 
sample — solubilities — element,  sulphide,  sulphate,  thiosulphate,  sulphite;  decompo- 
sition of  sulphur  ores;  sulphur  in  coal  by  Eschka's  method;  sulphur  in  rocks,  silicates 
and  insoluble  sulphates,  barium  and  lead  sulphates,  292-294.  Separations — sub- 
stances containing  iron,  separation  of  sulphur  from  metais  forming  an  insoluble 
sulphate,  nitrates  and  chlorates,  silica,  ammonium  and  alkali  salts,  394,  395.  Gravi- 
metric determination  of  sulphur — precipitation  as  barium  sulphate,  general  con- 
siderations, precipitation  from  hot  solutions,  precipitation  from  cold  solutions — 
large  volume,  standard  method  of  the  General  Chemical  Company,  395-398. 
Evolution  method  for  sulphur  in  steel,  ores,  cinders,  sulphides  and  metallurgical 
products,  398.  Combustion  method  for  evaluation  of  sulphide  ores,  402. 
Volumetric  methods  for  determining  soluble  sulphates — determination  of  sulphur 
by  Wildenstein's  method  and  by  Hinman's  method,  Benzidine  hydrochloride 
method,  403-405.  Determination  of  persulphates — ferrous  sulphate  and  oxalic  acid 
methods,  406.  Determination  of  sulphur  in  combination  as  sulphides,  sulphites, 
bisulphites,  metabisulphites,  thiosulphates,  sulphates — available  hydrogen  sulphide 
in  materials  high  in  sulphide  sulphur — iron  sulphide,  sodium  sulphide,  etc. ;  hydrogen 
sulphide  and  soluble  sulphides;  sulphide  and  sulphydrate  in  presence  of  each  other; 
thiosulphate  in  presence  of  sulphide  and  sulphydrate;  sulphates  and  sulphides  in  pres- 
ence of  one  another;  sulphur  in  thiocyanic  acid  and  its  salts;  sulphurous  acid  free, 
or  combined  in  sulphites,  acid  sulphites,  metabisulphites  and  thiosulphates — gravi- 
metric method  by  oxidation  to  sulphate  and  precipitation  as  barium  sulphate,  volu- 
metric methods — iodine  titration,  acidimetric  and  alkalimetric  methods;  determination 


CONTENTS  xxi 

of  sulphites,  metabisulphites,  thiosulphates,  sulphates,  chlorides,  and  carbonates  in 
presence  of  one  another,  407-413.  Determination  of  free  sulphur  in  a  mixture,  414. 
Evaluation  of  spent  oxide  for  total,  residual  and  available  sulphur,  414.  Analysis  of 
brimstone,  moisture,  available  sulphur,  ash,  arsenic  and  chlorine,  415. 

THORIUM 

R.  STUART  OWENS 
Research  Chemist,  New  York  City 

Detection,  316.  Estimation — occurrence,  416.  Preparation  and  solution  of  the 
sample — silicates;  phosphates  (monazite).  1.  By  fusion  with  potassium  acid  sulphate; 
2.  Sulphuric  acid  extraction;  oxides,  416,  417.  Separations  from  other  elements,  417. 
Gravimetric  method  for  determining  thorium,  417.  Minute  amounts  of  thorium  by 
Jolly's  method,  418. 

TIN 

H.  A.  BAKER 

Chief  Chemist,  American  Can  Company 

B.  S.  CLARK 
First  Assistant  Chemist,  American  Can  Company 

Detection  of  tin,  419.  Estimation— preparation  of  the  sample,  opening  up  tin 
ores — the  cyanide  process,  sodium  carbonate  method,  other  methods — fusion  with 
sodium  hydrate,  reduction  by  means  of  hydrogen,  fusion  with  sodium  peroxide,  419- 

421.  Separations — general  procedure,  separation  of  tin  from  lead,  copper,  antimony, 
phosphorus,  iron  and  alumina,  tungstic  acid,  421,  422.     Gravimetric  methods — de- 
termination of  tin  or  the  oxides  of  tin  by  hydrolysis,  determination  of  tin  as  sulphide, 

422,  423.     Bichloride  of  tin — stannic  acid  method — hot  water  precipitation;    Acker 
process  method;    determination  as  sulphide,  424-426.     Volumetric  determination  of 
tin — Lenssen's  iodine  method  as  modified  by  Baker,  standard  method  of  the  American 
Can  Company,  426.     Electrolytic  determination  of  tin,  430.     Estimation  of  tin  in 
canned  food  products,  430. 

TITANIUM 

WILFRED  W.  SCOTT 
Research  Chemist,  General  Chemical  Company 

L.  E.  BARTON 
Chief  Chemist,  Titanium  Alloy  Manufacturing  Company 

Detection— tests  with  hydrogen  peroxide,  morphine,  zinc,  sulphur  dioxide  and 
by  fusion  with  microcosmic  salt,  432.  Estimation — occurrence  and  application,  433. 
Preparation  and  solution  of  the  sample — element,  oxides,  salts  of  titanium — general 
considerations — solution  of  steel,  alloys,  ores,  titaniferous  slags,  433,  434.  Separations 
—titanium  from  the  alkaline  earths,  etc.;  separation  from  copper,  zinc,  aluminum, 
iron,  manganese,  nickel,  cobalt,  434,  435.  Gravimetric  methods— modified  procedure 
of  Gooch,  435.  Determination  of  titanium  in  ferro-carbon  titanium,  436.  Volumetric 
methods — reduction  of  titanic  solution,  addition  of  ferric  salt  and  titration  of  reduced 
iron  with  permanganate;  reduction  of  titanic  salt  and  titration  with  ferric  salt,  437-439. 


xxii  CONTENTS 

Colorimetric  determination  of  titanium  with  hydrogen  peroxide;  colorimetric  deter- 
mination in  steel  treated  in  ferro-carbon  titanium,  (a)  determination  of  titanium 
insoluble  in  hydrochloric  acid,  (6)  determination  of  titanium  soluble  in  hydrochloric 
acid,  (c)  total  titanium;  determination  in  presence  of  interfering  elements;  colori- 
metric determination  of  titanium  with  thymol  solution.  Analysis  of  titaniferous 
ores— determination  of  titanium,  silica,  alumina,  phosphorus.  Standard  methods  of 
the  Titanium  Alloy  Manufacturing  Company,  439-447. 

TUNGSTEN,   TANTALUM   AND    COLUMBIUM 

WILFRED  W.  SCOTT 

TUNGSTEN. — Detection — minerals,  iron,  steel  and  alloys,  448.  Estimation — 
occurrence  and  uses,  449.  Solution  of  the  sample — solubilities,  decomposition  of  ores, 
acids,  minerals,  steel  and  alloys,  steel  containing  a  high  percentage  of  tungsten,  ferro- 
tungsten  alloys,  tungsten  bronzes,  449-451.  Separations — tungsten  from  silica, 
separation  of  tungsten  from  tin,  antimony  by  Talbot's  process,  separation  from  arsenic 
and  phosphorus,  separation  from  molybdenum  by  Hommel's  process,  volatilization  of 
molybdenum  with  dry  hydrochloric  acid  gas  by  Pechard's  process;  separation  from 
vanadium,  titanium,  iron,  451-453.  Gravimetric  procedures — precipitation  of  tung- 
stic  acid,  precipitation  as  mercurous  tungstate  by  Berzelius'  process,  453,  454.  Volu- 
metric method,  454. 

TANTALUM  AND  COLUMBIUM. — Detection,  455.  Estimation — occurrence,  applica- 
tion, 455.  Solution  of  the  sample — general  procedure,  tantaliferous  minerals,  456. 
Separations — isolation  of  columbium  and  tantalum  oxides;  removal  of  tin,  antimony, 
tungsten  and  silica,  456,  457.  Determination  of  columbium  and  tantalum,  457. 

URANIUM 

WILFRED  W.  SCOTT 

Detection — general  procedure — uranous  salts,  uranyl  salts,  458.  Estimation — 
occurrence,  industrial  application,  458.  Preparation  and  solution  of  the  sample — 
solubilities — element,  oxide,  -salts;  solution  of  ores,  459.  Separations — uranium 
from  copper,  lead,  bismuth,  arsenic,  antimony,  and  other  members  of  the  hydrogen 
sulphide  group;  separation  of  uranium  from  iron  and  from  elements  having  water 
insoluble  carbonates;  separation  from  vanadium,  459,  460.  Gravimetric  determina- 
tion of  uranium  as  the  oxide,  U3O8,  461.  Volumetric  determination  of  uranium  by 
reduction  and  subsequent  oxidation,  461. 

VANADIUM 

WILFRED  W.  SCOTT 

Detection — tests  with  sulphide,  reducing  agents,  hydrogen  peroxide,  ammonium 
chloride,  distinction  from  chromium,  detection  in  steel,  463,  464.  Estimation — 
occurrence  and  industrial  application,  464.  Preparation  and  solution  of  the  sample — 
solubility  of  the  element,  its  oxides  and  salts;  general  procedure  for  decomposition  of 
ores  of  vanadium,  ores  high  in  silica,  products  low  in  silica,  iron,  steel  and  alloys,  465, 
466.  Separations — general  procedure,  removal  of  arsenic,  molybdenum,  phosphoric 
acid,  separation  of  vanadium  from  chromium,  466,  467.  Gravimetric  methods — deter- 
mination of  vanadium  by  precipitation  with  mercurous  nitrate;  by  precipitation  with 


CONTENTS 


XXlll 


lead  acetate,  467,  468.  Volumetric  methods— reduction  to  vanadyl  condition  and 
oxidation  with  potassium  permanganate,  reduction  with  zinc  followed  by  perman- 
ganate titration;  determination  of  vanadium  in  steel;  determination  of  molybdenum 
and  vanadium  in  presence  of  one  another;  determination  of  vanadium,  arsenic  or 
antimony  in  presence  of  one  another  by  Edgar's  method;  determination  of  vanadium 
and  iron  in  presence  of  one  another;  iodometric  method  for  estimation  of  chromic 
and  vanadic  acids  in  presence  of  one  another;  determination  of  vanadium  in  ferro- 
vanadium,  methods  of  the  Vanadium  Company  of  America — general  procedure,  vana- 
dium in  ores;  in  steel;  in  steel  containing  chromium;  in  cupro- vanadium;  in  brasses 
and  bronzes,  469-476. 

ZINC 

F.  G.  BBEYER,  M.A. 
Chief  of  the  Testing  Department,  New  Jersey  Zinc  Company  (of  Pa.) 

Detection  of  zinc,  477.  Estimation,  477.  Preparation  of  the  sample — moisture 
determination  in  the  pulp,  478.  Separations — from  silica,  cadmium,  arsenic, 
antimony,  bismuth,  copper,  iron,  alumina,  manganese,  nickel  and  cobalt,  478, 
479.  Methods  of  analysis — Gravimetric  methods — weighing  as  the  oxide,  electrolytic 
procedure,  479.  Volumetric  methods — ferrocyanide  titration  of  the  acid  Solution, 
separating  iron,  aluminum  and  manganese  with  ammonia  and  bromine;  titration 
of  the  alkaline  solution — procedure  for  common  ores;  procedure  for  copper-bearing  ores) 
procedure  for  material  containing  cadmium;  for  material  containing  carbonaceous 
matter;  procedure  for  material  containing  metallics;  general  notes,  480-483.  Standard 
method  of  the  New  Jersey  Zinc  Company — titration  in  acid  solution — separating  of 
zinc  as  sulphide;  standardization  of  the  ferrocyanide  solution;  procedure  with  material 
containing  insoluble  zinc;  discussion  on  separating  zinc  as  zinc  sulphide  and  titrating 
in  acid  solution,  483-487.  Determination  of  small  amounts  of  zinc,  487.  Special 
methods — determination  of  metallic  zinc  in  zinc  dust,  487.  Determination  of  impurities 
in  spelter-lead  by  electrolytic  and  "  lead  acid  "  methods;  iron  by  colorimetric  and  hydro- 
gen sulphide  methods;  cadmium  by  sulphide  and  electrolytic  method,  489-492. 
Determination  of  impurities  in  zinc  oxide  (reference) ;  general  references,  492,  493. 

ZIRCONIUM 

R.  STUART  OWENS 
Research  Chemist,  New  York  City 

Detection,  494.  Estimation,  494.  Preparation  and  solution  of  the  sample — 
materials  containing  a  large  amount  of  silica,  general  method  for  minerals,  oxides,  etc., 
other  methods,  494,  495.  Separations — from  iron,  titanium,  thorium,  carium,  the 
iron  group,  495.  Gravimetric  methods  for  the  determination  of  zirconium— salts  of 
zirconium,  minerals  and  silicates;  determination  as  phosphate;  determination  as 
zirconium  oxide;  determination  as  oxide  in  presence  of  iron,  496. 


xxiv  CONTENTS 


PART  II 

SPECIAL  SUBJECTS 
ACIDS 

WILFRED  W.  SCOTT 

Indicators — classification  and  special  uses  of,  499-501.  Ultimate  standards — 
preparation  of  pure  sodium  carbonate,  501.  Preparation  of  standard  acids — sulphuric 
acid,  hydrochloric  acid,  benzoic  acid,  standard  caustic  solution,  502-504.  Standard 
burettes,  505.  Methods  of  weighing  acids — dilute  acids  non-volatile  under  ordinary 
conditions;  weighing  of  strong  acids,  fuming  or  volatile  under  ordinary  conditions; 
Lunge-Ray  pipette,  Dely  weighing  tube,  snake  weighing  tube,  Blay-Burkhard  grad- 
uated weighing  burette,  506,  508.  Titration  of  acids  and  alkalies,  508.  Analysis 
of  muriatic  acid — total  acidity  and  hydrochloric  acid.  Impurities  in  commercial 
hydrochloric  acid — free  chlorine,  nitric  acid  or  nitrates;  sulphuric  acids  and  sulphates, 
arsenic,  barium  chloride,  silica  and  total  solids,  509,  510.  Analysis  of  hydrofluoric 
acid — total  acidity,  hydrofluosilicic  acid,  sulphuric  acid,  sulphurous  acid,  calculation 
of  results,  510-512.  Complete  analysis  of  nitric  acid — total  acidity,  sulphuric  acid 
hydrochloric  acid,  lower  oxides,  nitric  acid,  iodine,  free  chlorine,  total  non-volatile 
solids,  512-514.  Ferrous  sulphate  method  for  the  direct  determination  of  nitric  acid- 
standardization  of  the  reagents;  general  procedure  for  nitric  in  sulphuric  acid;  evalua- 
tion of  nitric  acid  or  nitrates;  determination  of  nitric  acid  in  oleum  or  mixed  acids; 
determination  of  nitric  acid  in  arsenic  and  in  phosphoric  acids,  515-520.  Determina- 
tion of  nitrous  acid  or  nitrite  by  the  permanganate  method,  520.  The  analysis  of 
oleum  or  fuming  sulphuric  acid  and  of  mixed  acid — total  acids,  lower  oxides,  sulphuric 
acid  and  free  sulphuric  anhydride,  nitric  acid,  calculating  of  results,  522-526.  Analysis 
of  acetic  acid — impurities  in  acetic  acid,  formic  acid,  furfurol,  acetone,  sulphuric  acid, 
sulphurous  acid,  hydrochloric  acid,  metals  in  acetic  acid,  527-529.  Acetates,  529. 
Citric  acid,  530.  Volumetric  estimation  of  free  acid  in  presence  of  iron  salts,  530. 
Estimation  of  carbonates  and  hydrates  of  potassium  and  sodium  when  together  in 
solution,  531. 

WATER   ANALYSIS 

D.  K.  FRENCH 
Director  of  the  Laboratory,  Dearborn  Chemical  Company 

General  considerations,  533.  Sanitary  analysis — organic  nitrogen;  chloride; 
oxygen  consumed;  physical  test — turbidity,  color,  odor— hot  or  cold;  taste,  534-535. 
Chemical  tests — free  ammonia,  albuminoid  ammonia,  organic  nitrogen;  nitrogen  as 
nitrite;  nitrogen  as  nitrate  by  phenolsulphonic  acid  method  and  by  aluminum  reduc- 
tion; oxygen  consumed;  chlorine  as  chlorides;  total  solid  residue,  536-542.  Inter- 
pretation of  results,  543.  Mineral  analysis — general  considerations,  outline  of  pro- 
cedure, silica,  manganese  and  phosphoric  acid;  iron  and  alumina  gravimetric;  iron 
colorimetric,  ferrous  iron  colorimetric;  phosphates,  calcium,  magnesium,  manganese — 
Knorre's  persulphate  method,  sodium  bismuthate  method  for  manganese;  sulphates — 
benzidine  method;  sodium  and  potassium;  alkalinity,  acidity,  free  carbonic  acid; 
chlorine;  nitrates;  ammonia  and  its  compounds;  total  mineral  residue;  hydrogen 
sulphide;  oil;  dissolved  oxygen  by  Winkler's  method,  545-557.  Methods  for  deter- 


CONTENTS  xxv 

mining  small  amounts  of  lead,  zinc,  copper  and  tin,  557.  Hardness,  preparation  of 
solutions,  magnesium  chloride,  calcium  sulphate;  lime  and  soda  value,  558-561. 
Methods  of  reporting  and  interpretation,  562.  Water  softening,  foaming  and  prim- 
ing, corrosion,  scale,  irrigating  waters,  hypothetical  combinations,  563-565.  Field 
assay  of  water,  565. 

FIXED   OILS,  FATS   AND  WAXES 

AUGUSTUS  H.  GILL,  PH.D. 
Professor  of  Technical  Analysis,  Massachusetts  Institute  of  Technology 

Introductory.  Examination  of  an  unknown  oil,  566.  Petroleum  products — 
Burning  oils;  flash  test,  determination  by  the  New  York  State  Board  of  Health  tester; 
fire  test;  specific  gravity,  (a)  by  the  hydrometer,  (6)  by  the  Westphal  balance;  dis- 
tillation test,  Engler's  method;  determination  of  sulphur;  detection  of  acidity;  sul- 
phuric acid  test;  mineral  salts;  determination  of  water;  color,  567-572.  Lubricating 
oils;  viscosity,  Engler  apparatus,  Saybolt  Universal  viscosimeter,  absolute  viscosity; 
specific  gravity;  evaporation  test;  cold  test;  flash  point;  fire  test;  detection  of 
soap;  caoutchouc;  tests  for  fatty  oils;  gumming  test;  carbon  residue  test, 
Gray's  method;  gasoline  test;  microscopical  test;  friction^tests,  572-580.  Animal 
and  vegetable  oils — specific  gravity;  refractive  index;  Valenta  test,  elaidin  test; 
Maumene*  test;  iodine  number;  Hanus's  method,  Hiibl's  method;  oxidized  oils,  iodine 
number;  bromine  number;  saponification  value;  detection  of  unsaponifiable  oils, 
from  saponification  number,  by  gravimetric  methods;  identification  of  the  unsaponi- 
fiable matter;  test  for  animal  or  vegetable  oils;  tests  for  antifluorescents;  acetyl 
value,  580-591.  Special  tests  for  certain  oils — Bechi's  test  for  cotton-seed  oil;  Hal- 
pen's  test  for  cotton-seed  oil;  hexabromide  test  for  linseed  oil;  Renard's  test  for  pea- 
nut oil;  Bach's  test  for  rapeseed  oil;  Liebermann-Storch  test  for  rosin  oil;  Baudouin's 
or  Camoin's  test  for  sesame"  oil;  free  acid  test;  spontaneous  combustion  test,  Mackey's 
apparatus;  drying  test  upon  glass;  titer  test,  591-599.  Edible  fats — butter,  examina- 
tion of  the  fat;  preservatives,  color;  lard,  water,  599-600.  Hardened  oils,  600.  Waxes, 
601.  Miscellaneous  oils  and  lubricants — general  description,  drying,  semidrying  and 
non-drying  oils,  601-602.  Tables — properties  of  some  mineral  oils;  characteristics 
of  the  fatty  acids  from  some  oils;  characteristics  of  some  oils;  characteristics  of  some 
waxes,  601-607.  Reagents,  607,  608. 

ANALYSIS  OF  PAINTS 

HENRY  A.  GARDNER 
Assistant  Director,  The  Institute  of  Industrial  Research,  Washington,  D.  C. 

JOHN  A.  SCHAEFFER,  PH.D. 
Chief  Chemist,  Eagle-Picher  Lead  Company,  Joplin,  Mo. 

Introductory,  609.  Analysis  of  paint  vehicles — composition  of  liquid  part;  per- 
centage of  liquid  by  ignition  method;  percentage  of  liquid  by  extraction  methods; 
separation  of  vehicle  components,  water,  direct  distillation  of  volatiles;  detection  of 
resinates;  detection  of  various  oils,  610-612.  Analysis  of  paint  oils— iodine  number; 
analysis  of  Chinese  wood  oil  (tung  oil),  specific  gravity,  acid  number,  saponification 
number,  unsaponifiable  matter,  refractive  index,  iodine  number  (Hiibl),  heating 
test  (Browne's  method),  iodine  jelly  test;  standards  of  Chinese  wood  oil,  A.  S.  T.  M.; 


xxvi  CONTENTS 

constants  of  various  oils,  comparative  tables;  examination  of  turpentine — color,  specific 
gravity,  refractive  index,  distillation,  polymerization;  standards  for  turpentine, 
A.  S.  T.  M.,  612-618.  Analysis  of  varnish — flash  point,  acid  number,  ash,  solvent, 
fixed  oils  and  resins,  separations'of  polymerized  oils  and  resins,  618-620.  Other  mate- 
rials, 620.  The  analysis  of  paint  pigments;  classification  of  pigments,  621.  Analysis 
of  white  pigments — sublimed  white  lead,  volumetric  determination  of  lead,  volumetric 
determination  of  zinc,  total  sulphate;  corroded  white  lead,  total  lead  (gravimetric), 
total  lead  (volumetric),  carbon  dioxide,  acetic  acid,  metallic  lead;  zinc  lead  and  leaded 
zinc — moisture,  lead,  zinc,  total  soluble  sulphates  (in  absence  of  BaS04),  total 
soluble  sulphates  (in  presence  of  BaS04),  soluble  zinc  sulphate,  sulphur  dioxide,  cal- 
culations; zinc  oxide — moisture,  carbon  dioxide,  insoluble  matter,  sulphuric  anhydride, 
total  S  as  S03;  lead  oxide,  gravimetric  method,  electrolytic  method,  chlorine,  ferric 
oxide,  manganese  oxide,  arsenous  oxide,  S0>  equivalent,  zinc  oxide;  lithopone — 
moisture,  barium  sulphate,  total  zinc,  zinc  sulphide,  soluble  salts;  silex — moisture,  loss 
on  ignition,  insoluble  matter,  carbon  dioxide;  whiting — Paris  white — moisture,  loss 
on  ignition,  calcium,  magnesium,  carbon  dioxide,  sulphates;  barytes  and  blanc 
fixe — moisture,  loss  on  ignition,  barium  ralphate,  soluble  sulphates,  carbon  dioxide; 
analysis  of  a  composite  white  paint — insoluble  residue,  total  lead,  alumina  and  iron 
oxide,  zinc,  calcium  and  magnesium,  sulphate,  sulphide,  carbon  dioxide,  calculations, 
622-634.  Red  and  brown  pigments — red  lead  and  orange  mineral— moisture,  organic 
color,  total  lead  and  insoluble  residue,  lead  peroxide  (PbO2)  and  true  red  lead  (Pb304), 
calculation;  vermilion — characteristics  of;  iron  oxides,  634,  637.  Blue  pigments — 
ultramarine  blue — moisture,  silica,  aluminum  oxide,  sodium  oxide,  total  sulphur,  sul- 
phur present  as  sulphate;  Prussian  blue — moisture,  nitrogen,  iron  and  aluminum  oxides, 
sulphuric  acid,  commercial  analysis;  sublimed  blue  lead — total  lead,  total  sulphur, 
lead  sulphate,  lead  sulphite,  lead  sulphide,  lead  carbonate,  lead  oxide,  zinc  oxide,  carbon 
and  volatile  matter,  637-639.  Yellow  and  orange  pigments — chrome  yellow,  mois- 
ture, insoluble  residue,  lead,  chromium,  zinc,  calcium  and  magnesium,  sulphuric  acid, 
calculations,  639.  Green  pigments,  chrome  green — moisture,  insoluble  residue,  lead, 
iron,  alumina  and  chromium,  calcium  and  magnesium,  sulphuric  acid,  nitrogen,  cal- 
culation, 639,  640.  Black  pigments — moisture,  oil,  carbon,  ash,  analysis  of  ash,  640- 
641.  Complex  compounds — hydroferrocyanic  and  hydroferricyanic  acids,  641. 

CEMENTS 

RICHARD  K.  MEADE,  M.S. 
Chemical,  Mechanical  and  Industrial  Engineer,  Baltimore,  Md. 

Analysis  and  testing  of  cements — introductory,  642.  Physical  testing — fineness, 
specific  gravity,  normal  consistency,  table — percentage  of  water  for  standard  sand 
mortar,  setting  time,  soundness  or  consistency  of  volume,  tensile  strength,  notes, 
apparatus  for  testing  of  cement,  642-649.  Standard  method  for  chemical  analysis  of 
Portland  cement — solution,  silica,  alumina  and  iron,  lime,  magnesia,  alkalies,  anhydrous 
sulphuric  acid,  total  sulphur,  loss  on  ignition,  insoluble  residue,  650,  653.  Rapid 
method  for  chemical  analysis  of  Portland  cement,  653.  Rapid  method  for  checking 
the  percentage  of  calcium  carbonate  in  cement  mixture,  standard  alkali,  standard  acid, 
standard  sample,  standardizing  the  acid,  determination,  656-658.  Analysis  of  lime- 
tone,  cement  rock,  lime,  Rosendale  cement,  etc.,  658. 


CONTENTS  xxvii 

ANALYSIS  OF  ALLOYS 

JOHN  C.  OLSEN,  PH.D. 
Professor  in  Charge  of  the  Department  of  Chemistry,  Cooper  Union,  New  York  City 

Introduction — difficulty  of  complete  separation  of  elements,  limit  of  accuracy  in 
analysis,  659.  Analysis  of  type  metal— solution  of  the  alloy,  lead,  copper  and  iron, 
separation  of  antimony  and  tin,  determination  of  antimony,  tin  and  arsenic,  659-661. 
Analysis  of  soft  solder — solution  of  the  alloy,  determination  of  tin,  lead,  arsenic, 
antimony,  iron,  zinc,  661-663.  Analysis  of  Rose's  metal — decomposition  of]  material, 
determination  of  lead,  bismuth,  copper,  663.  Analysis  of  Wood's  metal — decomposi- 
tion of  the  material,  determination  of  lead,  bismuth,  cadmium,  arsenic,  tin,  separation 
of  copper  and  cadmium,  determination  of  copper,  separation  and  estimation  of  iron 
and  zinc,  664,  665.  Analysis  of  Britannia  metal — decomposition  of  the  alloy  by  means 
of  chlorine,  determination  of  lead,  copper,  iron,  bismuth,  separation  of  tin  from  arsenic 
and  antimony,  determination  of  tin,  arsenic  and  antimony,  666,  667.  Analysis  of 
brass  or  bronze — solution  of  the  alloy,  determination  of  tin,  arsenic,  antimony,  lead, 
copper,  iron,  zinc,  667-669.  Analysis  of  German  silver — decomposition  of  the  mate- 
rial, determination  of  zinc,  iron  and  nickel,  668.  Analysis  of  manganese  and  phos- 
phorous bronze — solution  of  the  alloy,  determination  of  lead,  copper,  zinc,  iron,  man- 
ganese, phosphorus,  670,  671. 

METHODS  FOR  ANALYSIS  OF  COAL 

FRANK  E.  HALE,  PH.D. 

Director  of  Laboratories,  Department  of  Water  Supply,  Gas  and  Electricity,  New  York  City. 
Sampling;  preparation  of  the  sample  for  analysis,  672-674.  Methods  of  analysis 
— moisture,  ash,  volatile  combustible  matter,  volatile  sulphur,  turbidimetric  sulphur 
table,  fixed  carbon,  calorific  value,  calculation  of  B.t.u.,  standardization  of  the  calo- 
rimeter, 674-683.  Determination  of  fusibility  of  coal  ash,  684.  References,  685. 

GAS  ANALYSIS 

AUGUSTUS  H.  GILL,  PH.D. 
Professor  of  Technical  Analysis,  Massachusetts  Institute  of  Technology 

Sampling— tubes,  pumps,  containers  for  samples,  687-689.  Measurement  of 
gas  in  large  quantities— wet  and  dry  meters,  Pitot  tube  or  Davis  anemometer,  rotam- 
eter  or  Thorpe  gauge,  capometer,  Thomas  electric  meter,  orifice  meter,  anemometer, 
689-692.  Measurement  of  gas  in  small  quantities— gas  burettes,  Hempel  Orsat 
and  Elliot  burette,  separatory  funnel  and  graduate,  692.  Absorption  apparatus, 
tubes  and  pipettes,  693.  Examination  of  the  gases— detection  and  determination 
of  the  various  gases,  tables,  694-697.  Analysis  of  gaseous  mixtures— analysis  by  means 
of  the  Orsat  apparatus,  determination  of  carbon  dioxide,  oxygen,  carbon  monoxide, 
hydrocarbons,  notes  on  manipulation;  Elliot  apparatus,  determination  of  carbon 
dioxide,  oxygen,  carbon  monoxide,  notes;  Hempel  apparatus,  determination  of  oxygen 
in  air— (1)  by  phosphorus,  (2)  by  pyrogallate  of  potassium,  (3)  by  explosion  with 
hydrogen;  analysis  of  illuminating  gas— carbon  dioxide,  illuminants,  oxgyen,  carbonic 
oxide,  methane  and  hydrogen,  (a)  Hinman's  method,  (6)  Hempel's  method;  nitrogen, 
notes,  697-707.  Applications  of  gas  analysis  and  interpretation  of  results— I.  Chimney 


xxviii  CONTENTS 

and  flue  gases — carbonic  acid  indicators,  determination  of  temperature,  composition 
of  the  coal,  tables,  smoke,  708-711.  II.  Producer  and  fuel  gases,  blast-furnace  gas — 
analysis,  dust  in,  711-712.  III.  Illuminating  gas,  candle-power,  calorific  power,  sulphur, 
H2S,  ammonia,  naphthalene,  carbon  dioxide,  specific  gravity,  tar,  712-720.  IV.  Sul- 
phuric acid  gases — (a)  burner  gases — sulphur  dioxide  in  inlet  and  exit  gases,  Reich 
method  for  SO2,  absorption  of  SO2  in  chromic  acid  solution;  (6)  nitrogen  oxides,  720- 
726.  V.  Mine  gases,  726.  VI.  Electrolytic  gases,  727.  VII.  Acetylene,  727.  Atmos- 
spheric  air  moisture,  carbon  dioxide,  ozone,  carbon  monoxide,  bacteria,  728-730. 
Determination  of  moisture  in  gases,  731.  Determination  of  nitrogen  by  the  nitrometer, 
732.  Reagents  and  tables,  734-738. 

ASSAYING 
WALLACE  G.  DERBY,  M.S. 

Research  Chemist,  Nichols  Copper  Company 

Sample,  the  unit  of  weight,  general  survey  of  the  subject  of  sampling,  739. 
Furnace  operations;  consequent  to  the  furnace  operations;  preliminary  to  the  furnace 
operations;  silver  and  gold  retained  in  the  slag;  silver  and  gold  retained  in  the  cupel; 
corrected  assay;  determination  of  gold;  determination  of  silver;  influence  of  quantity 
of  sample,  741.  Roasting,  incineration,  743.  Crucible  method  of  fusion,  744.  Scori- 
fication  method  of  fusion,  755.  Cupellation,  759.  Parting,  766.  Combination  meth- 
ods, 769.  Determination  of  gold  in  cyanide  solution,  773. 

PART  III 
TABLES  AND  USEFUL  DATA 

I.  International  atomic  weights,  779.  II.  Melting-points  of  chemical  elements, 
780.  III.  Temperature  standards,  780.  IV.  Electromotive  arrangement  of  the  ele- 
ments, 781.  SPECIFIC  GRAVITY  TABLES  OF  THE  ACIDS  AND  ALKALIES,  782-799. 
V.  Hydrochloric  acid — Ferguson,  782.  VI.  Hydrochloric  acid — Lunge  and  March- 
lewski,  784.  Constant  boiling-points,  784.  VII.  Nitric  acid,  Ferguson,  785.  VIII. 
Nitric  acid,  Lunge  and  Rey,  787.  IX.  Phosphoric  acid — Hager,  789.  X.  Sul- 
phuric acid— Ferguson  and  Talbot,  790.  XI.  Sulphuric  acid—Bishop,  794.  XII. 
Acetic  acid — Oudemans,  795.  XIII.  Melting-points  of  acetic  acid — Rudorff,  795. 
XIV.  Aqua  ammonia— Ferguson,  796.  XV.  Sodium  hydroxide — Lunge,  798.  XVI. 
Vapor  tension  of  water  in  milligrams  of  mercury,  from  —2°  to  +36°  C. — Regnault, 
Broch  and  Weibe,  800.  XVII.  Useful  data  of  the  more  important  inorganic  com- 
pounds—Meiklejohn,  801.  XVIII.  Conversion  factors— Scott  and  Clark,  804.  XIX. 
Comparison  of  centigrade  and  Fahrenheit  scale,  818.  XX.  Relation  of  Baume" 
degrees  to  specific  gravity  and  the  weight  of  one  U.  S.  gallon  at  60°  F.,  819.  XXI. 
Comparison  of  customary  units  of  weight  and  measure  with  the  metric  system, 
820.  XXII.  Table  of  constants  for  certain  gases  and  vapors,  822.  XXIII.  Solu- 
bility table,  824.  TABLES  OF  QUALITATIVE  TESTS,  825-855:  XXIV.  Blowpipe  and 
flame  tests  of  solids,  827-829.  XXV.  Separation  of  the  bases— Analysis  of  the  solu- 
tion, 830,  831.  XXVI.  Tests  for  acids,  832.  XXVII.  Tables  of  reactions  of  the 
bases,  834-847.  XXVIII.  Tables  of  reactions  of  the  acids,  848-855.  General  refer- 
ences, 856.  Index,  861-898. 

APPENDIX 
ANALYSIS  OF  BRASS— DETERMINATION   OF  ARSENIC  AND  CADMIUM  858 


LIST  OF  ILLUSTRATIONS 

na* 

1 .  Apparatus  for  Distillation  of  Arsenous  Acid 34 

2.  Urbasch's  Hydrogen  Sulphide  Generator 37 

3.  Scott's  Hydrogen  Sulphide  Generator 38 

4.  Banks'  Hydrogen  Sulphide  Generator 39 

5.  Purification  of  Hydrochloric  Acid 41 

6.  Gutzeit  Apparatus  for  Arsenic  Determination 46 

7.  Purification  of  Carbon  Disulphide 67 

8.  Distillation  of  Methyl  Borate 74 

9.  Test  for  Carbonate 93 

10.  Chilled  Steel  Mortar 94 

11.  Geissler  Bulb 96 

12.  Liebig  Bulb 96 

13.  Gerhardt  Bulb 96 

14.  Vanier  Bulb 96 

15.  Fleming's  Apparatus  for  Determination  of  Carbon  by  Combustion 97 

16.  Fleming's  Absorption  Apparatus 98 

17.  Boat  and  Holder  for  Carbon 100 

18.  Shinier  Combustion  Apparatus 100 

19.  Diagrammatic  Sketch  of  Combustion  Tube 101 

20.  Apparatus  for  Determining  Carbon  Dioxide 104 

21.  Shroetter's  Alkalimeter 106 

22.  Mohr's  Alkalimeter 106 

23.  24.  Hot  Water  Racks  for  Test  Tubes;  Color  Carbon  Determination 108 

25.  Carbon  Tubes 109 

26.  Color  Comparitor  or  Camera 109 

27.  Terminal  Case  Showing  Battery  of  Electrodes 155 

28.  Solenoid  for  Rotation  of  Electrolyte 157 

29.  Riffle  Sampler 159 

30.  Constant  Temperature  Bath  and  Dividing  Pipette 160 

31.  Hydrometer  Jar  for  Electrolysis  of  Copper 160 

32.  Special  Beaker  for  Electrolysis  of  Copper 173 

32a.  Combustion  Furnace,  Hinged  Type 174 

33.  Etching  Test  for  Fluorine 176 

34.  Hanging  Drop  Test  for  Fluorine 177 

35.  Black  Filter  Paper  Test  for  Fluorine 177 

36.  Adolph's  Apparatus  for  Determining  Fluorine 182 

37.  Steiger-Merwin  Fluorine-Titanium  Chart 185 

38.  Merwin's  Chart  on  Ratio  of  Depth  of  Color 185 

39.  Apparatus  for  Determining  Iodine  in  Iodide 

40.  49.  Jones'  Reductor 220,  281 

41.  Apparatus  for  Stannous  Chloride  Titration  of  Iron 221 

42.  Dividing  Pipette 223 

xxix 


xxx  LIST   OF  ILLUSTRATIONS 

• 

FIQ.  PAGE 

43.  Hurley's  Colorimeter 245 

44.  Cooper  Hewitt's  Mercury  Light 247 

45.  Bell  Jar  Vacuum  Filtering  Apparatus 265 

46.  Automatic  Measuring  Pipette 265 

47.  Sulphur  Extraction  Apparatus 272 

48.  Hollo way-Eschka  Apparatus  for  Determining  Mercury 273 

50.  Apparatus  for  Determining  Nitrogen,  Kjeldahl  Method 294 

51.  Devarda's  Apparatus  Modified  by  Allen 301 

52.  Weighing  Bottle  and  Dropper 302 

53.  Mitscherlich's  Apparatus,  Nitrogen  in  Soils 305 

54.  Nitrometer 307 

55.  Du  Font's  Nitrometer 307 

55a.  Becker  Chain  Balance 323 

56.  J.  Lawrence  Smith  Apparatus 355 

57.  Apparatus  for  Separation  of  Selenium  and  Tellurium. 362 

58.  Lead  Cup  for  Silica  Test 367 

59.  Apparatus  for  Determining  Silver,  Gay-Lussac  Method 381 

60.  Evaporation  in  Sulphur  Determination 397 

61.  62.  Apparatus  for  Precipitating  Sulphur 397 

63.  Apparatus  for  Filtering  Barium  Sulphate 398 

64.  Scott's  Apparatus  for  Determining  Sulphur  in  Iron  and  Steel 399 

65.  Arrangement  for  Protecting  the  Crucible  from  the  Flame 101 

66.  Sanders'  Extraction  Apparatus 414 

67.  Seller's  Apparatus  for  Determining  Tin 428 

68.  Seller's  Apparatus,  Diagrammatic  Sketch 429 

69.  70.  Colorimeter 440,  442 

71.  Voit  Flask  and  Distillation  Apparatus 473 

72,  73,  74.  Apparatus  for  Determining  Zinc 488 

75.  Arrangement  for  Heating  Sodium  Bicarbonate 501 

76,  77,  78.  Charts  Showing  Specific  Gravity  and  Boiling-points  of  Sulphuric 

Acid  of  Varying  Concentration 502 

79.  Standard  Burette 505 

80.  Lunge-Ray  Pipette 506 

81.  Dely  Weighing  Tube  in  Operation 507 

82.  Snake  Tube 507 

83.  Blay-Burkhard  Graduated  Weighing  Burette 508 

84.  Method  for  Rapid  Evaporation  of  Liquids 522 

85.  Apparatus  for  Determining  Ammonia  in  Water 536 

86.  New  York  Tester 587 

87.  Westphal  Balance 569 

88.  Engler  Viscosimeter 573 

89.  Saybolt  Viscosimeter 573 

90.  Cleveland  Cup 577 

91.  Gray's  Distillation  Flask 579 

92.  Refractometer 581 

92a.  Mackay's  Apparatus 596 

93.  Le  Chatelier's  Specific  Gravity  Apparatus 643 

94.  Vicat  Needle 644 

95.  Gilmore  Needles..  .  645 


LIST   OF   ILLUSTRATIONS  xxxi 

FIG>  PAQB 

96.  Pat  for  Determining  Setting  Time  and  Soundness  in  Cement 646 

97.  Appearance  in  Pats  Made  from  Sound  and  Unsound  Cement  after  Steaming  646 

98.  Details  for  Briquette 647 

99.  Details  for  Gang  Mold 647 

100.  Fairbanks'  Cement  Testing  Machine 648 

101.  Riehle  Automatic  Cement  Testing  Machine 649 

102.  Apparatus  for  Determining  Calcium  Carbonate  with  Acid  and  Alkali 657 

103.  Quartering  Coal,  Ball  Mill  for  Pulverizing,  and  Suction  Ventilator 673 

104.  V.  C.  M.  Apparatus 675 

105.  Atwater  Bomb  and  Calorimeter 679 

106.  Oxygen  Cylinders  for  Calorimeter 680 

107.  Haskins'  Electric  Furnace,  Optical  Pyrometer  Outfit 684 

108.  Sampling  Tube  for  Gas 687 

109.  110,  111.  Pumps 688 

112.  Container  for  Gas  Sample 689 

113.  Pitot  Tube 690 

114.  Rotameter 691 

115.  Capometer 691 

116.  Friedrichs'  Spiral  Gas  Washing  Bottle 693 

117.  Varentrapp  and  Will  Bulbs 693 

118.  Wolf  Absorption  Bulb 693 

119.  Winkler's  Spiral 693 

120.  Orsat  Apparatus 697 

121.  Elliott's  Apparatus 700 

122.  Hempel's  Apparatus 702 

123.  Hempel's  Combustion  Apparatus 703 

124.  125,  126.  Junker's  Calorimeter 713,  714 

127.  Apparatus  for  Determining  Sulphur  in  Gas 716 

128.  RudorfTs  Apparatus  for  CO2  in  Gas 719 

129.  Specific  Gravity  Apparatus  for  Gas 719 

130.  Reich  Apparatus  for  S02  in  Contact  Gas 721 

131.  Briggs-Scott  Modified  Orsat  Apparatus  for  SO2  in  Contact  Gas 723 

132.  Hesse's  Apparatus  for  CO2  in  Air 728 

133.  Absorption  Spectrum  Chart,  CO2  Determination 730 

134.  Phosphorus  Pentoxide  Bulb  for  Water  Vapor  in  Gas 731 

135.  Apparatus  for  Determining  Gasoline  Vapor  in  Gas 731 

136.  Nitrometer 732 

137.  Bunte's  Chart 738 

138.  Chart  Showing  Influence  of  Quantity  of  Gold  or  Silver  in  Assaying 743 

139.  Assay  Furnace 744 

140.  Assaying  Outfit 755 

141.  Chart  Showing  Cupellation  Loss 764 

142.  Assay  Balances 767 

PLATE     I.  Arsenic  Stains,  Gutzeit  Method Facing  page    46 

PLATE    II.  Emissions  Spectra Facing  page    53 

PLATE  III.  Diffraction  Grating  Spectrum  and  Prismatic  Spectrum Facing  page  341 


PART  I 

TECHNICAL    METHODS  FOR    THE  DETECTION   AND 

DETERMINATION  OF  THE  MORE  IMPORTANT 

ELEMENTS 


ALUMINUM  i 

WILFRED  W.  SCOTT 
Al,  at.wt.  27.1;  sp.gr.  2.583;  m.p.  658.7°;  b.p.  2200°;  oxide  A12O,. 

DETECTION 

The  sample  is  brought  into  solution  according  to  one  of  the  procedures  out- 
lined under  "  Preparation  and  Solution  of  the  Sample."  Silica  is  removed  by 
taking  the  solution  to  dryness,  boiling  the  residue  with  hydrochloric  acid  and 
filtering.  The  members  of  the  hydrogen  sulphide  group  are  removed  as  usual 
with  H2S,  the  filtrate  boiled  to  expel  the  excess  of  H2S,  iron  oxidized  with  nitric 
acid,  and  aluminum,  iron  and  chromium  precipitated  as  hydroxides  by  addition 
of  ammonium  hydroxide  in  presence  of  ammonium  chloride.  On  treating  the 
precipitate  with  sodium  peroxide,  aluminum  and  chromium  hydroxides  dissolve, 
whereas  ferric  hydroxide  remains  insoluble.  Aluminum  hydroxide  is  precipi- 
tated by  acidifying  the  alkaline  solution  with  hydrochloric  or  nitric  acid,  and 
neutralizing  with  ammonia;  chromium  remains  in  solution. 

The  white  gelatinous  precipitate  of  aluminum  hydroxide  may  be  confirmed 
by  adding  a  drop  of  cobalt  nitrate  solution  and  burning  the  filter.  The 
residue  will  be  colored  blue  by  the  resulting  aluminum  cobalt  compound. 

Sodium  thiosulphate,  Na2S203,  added  to  a  neutral  or  slightly  acid  solution, 
containing  aluminum,  precipitates  aluminum  hydroxide,  upon  boiling  the  solu- 
tion. Sodium  sulphite,  or  ammonium  chloride  added  in  large  excess,  will  also 
cause  this  precipitation. 

ESTIMATION 

The  determination  of  aluminum,  in  terms  of  alumina,  A1203,  is  required  in 
the  evaluation  of  aluminum  ores,  bauxite,  A120(OH)4;  diaspore,  AIO(OH);  alunite, 
K.O.SAlaOs^SOa.GHjO,  etc.  It  is  determined  in  the  analysis  of  feldspar,  hal- 
loysite,  clays,  granite,  gneiss,  porphyry,  mica  schist,  slate,  obsidian  or  pumice 
stone,  cryolite,  limestone,  and  in  the  complete  analysis  of  a  large  number  of 
mineral  substances.  The  estimation  of  alumina  is  required  in  the  analysis  of 
cements,  plaster,  ceramic  materials,  aluminum  salts,  and  is  especially  important 
in  the  control  of  processes  in  the  manufacture  of  aluminum  products.  As  a 
metal  it  is  determined  in  commercial  aluminum,  and  its  alloys. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  substances  containing  aluminum  it  will  be  recalled  that  alumina, 
although  ordinarily  soluble  in  acids,  is  very  difficult  to  dissolve  when  it  is  highly 
heated.  It  may  be  best  dissolved,  in  this  case,  by  fusion  with  sodium  carbonate 
or  with  acid  potassium  sulphate,  followed  by  an  acid  extraction.  The  metal  is 
scarcely  acted  upon  by  nitric  acid,  but  is  readily  soluble  in  the  halogen  acids  and 
in  hot  concentrated  sulphuric  acids. 

General  Procedure  for  Ores.  One  gram  of  the  finely  powdered  ore, 
taken  from  a  representative  sample,  is  placed  in  a  platinum  dish,  5  cc.  of  con- 

1Also  spelled  Aluminium. 
3 


4  ALUMINUM 

centrated  sulphuric  acid  are  added,  followed  by  about  20  cc.  of  strong  hydro- 
fluoric acid.  The  mixture  is  evaporated  over  a  steam  bath  as  far  as  possible 
and  then  taken  to  S03  fumes  on  the  hot  plate  (Hood).  Upon  cooling,  a  little 
dilute  hydrochloric  acid  is  added  and  the  mixture  warmed.  The  solution  is 
diluted  with  distilled  water  and  filtered  if  any  residue  remains. 

The  insoluble  residue  remaining  on  the  filter  may  be  brought  into  solution 
by  fusing  the  ignited  residue  with  sodium  carbonate  or  acid  potassium  sulphate. 
If  barium  is  present  sodium  carbonate  fusion  is  made  and  the  melt  extracted 
with  water  to  remove  the  sodium  sulphate.  The  residual  carbonates  may  now  be 
dissolved  with  hydrochloric  acid. 

SULPHIDE  ORES  should  be  oxidized  with  nitric  acid  and  bromine  according 
to  the  general  procedure  for  decomposing  pyrites  in  the  determination  of 
sulphur. 

The  solution  of  the  sample  having  been  effected,  aluminum  is  separated  from 
elements  that  interfere  in  its  estimation.  Directions  for  the  removal  of  these 
substances  are  given  under  "  Separations."  The  element  is  now  in  solution  in 
such  form  that  it  may  be  determined  gravimetrically  or  volumetrically. 

Fusion  Method.  Sodium  Carbonate.  The  air-dried  material,  ground  to  a 
fine  powder,  is  placed  in  a  glass-stoppered  bottle.  If  the  determination  is  to  be 
made  on  the  dry  basis,  moisture  is  driven  out  by  placing  the  material  in  the  hot  air 
or  steam  oven  for  an  hour  (100  to  110°  C.).  One  gram  sample,  placed  in  a  large 
platinum  crucible,  is  mixed  with  4  to  5  grams  of  anhydrous  sodium  carbonate 
and  the  material  heated  to  fusion,  the  heating  being  continued  until  the  molten 
mass  appears  clear.  The  liquid  mass  may  be  poured  on  a  large  platinum  crucible 
lid,  or  if  preferred,  allowed  to  cool  in  the  crucible,  a  platinum  prod  being  held  in  the 
fusion  until  it  solidifies.  By  gently  heating  the  crucible  over  a  flame  the  fusion 
loosens  from  the  sides  and  may  be  lifted  out  on  the  prod.  In  either  case  the 
cooled  mass  is  dissolved  by  placing  it,  together  with  the  crucible  in  which  the  fusion 
was  made,  in  a  casserole,  and  treating  with  hydrochloric  acid,  the  casserole  being 
covered  with  a  clock  glass  during  the  reaction. 

Silica  is  removed  by  evaporating  the  solution  to  dryness  on  the  water  or  steam 
bath  and  drying  in  the  oven  at  110°  C.  for  an  hour  or  more.  The  residue  is 
extracted  with  hot  dilute  hydrochloric  acid  and  silica  filtered  off. 

If  the  solution  is  cloudy  upon  treatment  of  the  fusion  with  acid,  it  indi- 
cates either  the  presence  of  barium  sulphate  or  incomplete  decomposition  of 
the  sample.  In  the  latter  case  the  residue  is  gritty  and  the  fusion  of  this 
material  should  be  repeated. 

Fusion  with  Potassium  Bisulphate.  This  procedure  is  recommended  for 
the  decomposition  of  commercial  alumina  or  calcined  A1203.  The  procedure  is 
similar  to  the  sodium  carbonate  fusion  with  the  exception  that  less  heat  is  required. 
A  silica  dish  may  be  used,  if  desired,  in  place  of  platinum. 

Extraction  of  Ores  of  Aluminum  for  Their  Commercial  Valuation.  The 
available  alumina  in  bauxite,  alunite,  clays  and  aluminum-bearing  materials 
may  be  approximately  ascertained  by  digesting  5  grams  of  the  pulverized  sample 
with  45  cc.  of  5  N.  H2S04  for  three  hours  in  a  Kjeldahl  flask  with  reflux  con- 
denser, the  heat  being  so  regulated  l  that  the  drip  from  the  condenser  amounts 
to  5  to  8  drops  per  minute.  The  solution  filtered  hot,  together  with  the  wash- 
ings of  the  residue  is  diluted  to  1000  cc.  Aliquot  portions  of  this  solution 

1  Method  for  controlling  temperature  by  observing  condensation  suggested  by 
W.  S.  Allen. 


ALUMINUM  5 

are  taken  for  determination  of  the  desired  soluble  constituents,  according 
to  the  procedures  outlined  under  bauxite  analysis  in  the  latter  portion  of  the 
chapter. 

Solution  of  Metallic  Aluminum  and  its  Alloys.  The  metal  may  be  dis- 
solved in  .dilute  hydrochloric  acid,  1:1,  or  in  a  solution  of  sodium  hydroxide 
or  potassium  hydroxide. 

Alloys  of  aluminum  are  best  brought  into  solution  with  a  mixture  of  hydro- 
chloric and  nitric  acids. 

SEPARATIONS 

General  Considerations.  In  the  usual  course  of  analysis,  aluminum  is 
in  solution  as  a  sulphate  or  as  a  chloride,  silica  having  been  removed  by  dehy- 
dration, as  described  under  " Preparation  and  Solution  of  the  Sample."  The 
following  interfering  elements  may  be  present  in  the  solution:  iron,  manganese, 
arsenic,  antimony,  titanium,  phosphoric  acid,  and  more  rarely  chromium  and 
zirconium.  In  alloys  of  aluminum  other  elements  may  be  added  to  this  list. 
The  separation  more  commonly  required  is  from  iron,  aluminum  and  iron 
being  precipitated  together  as  the  hydroxides.  In  usual  practice  the  two  are 
weighed  together  as  Fe203  and  A1203,  after  ignition  to  this  form,  and  iron  then 
determined,  either  on  a  separate  portion  of  the  sample,  or  by  solution  of  the 
precipitate  by  fusion  with  sodium  carbonate  or  potassium  bisulphate  and  sub- 
sequent extraction  with  hydrochloric  acid.  The  following  procedures  of  sep- 
arations are  given  for  special  cases  less  commonly  required  in  analysis.  The 
chemist  should  be  familiar  with  the  substance  with  which  he  is  working  and 
have  a  general  idea  of  its  composition  in  order  to  be  able  to  choose  the 
correct  procedure  for  estimation  of  the  aluminum  content.  In  ores  and  mate- 
rials to  be  used  for  production  of  aluminum  compounds  the  results  are  reported 
in  terms  of  the  oxide-alumina,  A1203,  in  alloys  as  the  element,  Al. 

Removal  of  Silica.  This  compound  has  already  been  considered  under 
'Preparation  and  Solution  of  the  Sample,"  Si02  being  removed  by  taking  the 
solution  to  dryness,  dehydrating  the  oxide  by  additional  heating  in  the  oven, 
followed  by  extraction  of  the  soluble  constituents  with  dilute  hydrochloric  acid 
and  filtration.  Under  the  first  procedure  for  solution  of  the  ore  by  sulphuric  and 
hydrofluoric  acids  silica  is  expelled  as  gaseous  SiF4. 

Separation  from  Iron.  1.  Aluminum  hydroxide  is  precipitated  by  the 
addition  of  a  salt  of  a  weak  acid  to  its  neutral  or  slightly  acid  solution,  iron 
remaining  in  solution.  Details  of  the  procedure  for  precipitation  of  aluminum 
hydroxide  by  means  of  sodium  thiosulphate  are  given  under  "Gravimetric 
Methods  for  Determination  of  Aluminum,"  page  9. 

2.  Aluminum  chloride  is  precipitated  from  a  concentrated  solution  of  hydro- 
chloric acid  and  ether  saturated  with  HC1  gas.  Details  of  the  procedure  are 
given  under  the  gravimetric  methods  for  aluminum,  page  10. 

NOTE.  The  following  additional  procedures  for  separation  of  iron  and  alumina 
have  been  suggested: 

(a)  Precipitation  of  iron  as  FeS  in  presence   of   organic  acids,   citric,  tartanc, 
salicylic,  etc.,  aluminum  remaining  in  solution. 

(b)  Precipitating  iron  by  adding  sodium  peroxide  to  a  cold  neutral  solution  of 
the  elements  until  the  precipitate  first  formed  dissolves,  then  decomposing  the  sodium 
ferrate  by  boiling,  Fe(OH)3  precipitates,  Al  remaining  in  solution.     (Glaser,  J.  S.  C.  L, 
1897,  936.) 


6  ALUMINUM 

(c)  The  neutral  solution  of  the  elements  is  boiled  with  freshly  precipitated  MnO2, 
which  causes  the    precipitation  of   iron   as  Fe(OH)3,   while  aluminum  remains    in 
solution,  (chromium  also  passes  into  the  filtrate). 

(d)  Precipitation  of  iron  from  acid  solutions  by  means  of  amino-nitrosophenyl- 
hydroxylamine,  (cupferron),  aluminum  remaining  in  solution.     (O.  Baudisch,  Chem. 
Ztg.,  33,  1298,  1905.     Ibid.,  35,  913,  1911;    O.  Baudisch  and  V.  L.  King,  J.  I.  E.  C., 
3,627,  1911). 

(e)  Precipitation  of  aluminum   (together  with  phosphoric  acid,   if  present),  by 
phenylhydrazine,  added  to  the  reduced,   weakly  acid  or  neutral  solutions.     Iron, 
cobalt,  nickel,  calcium,  and  magnesium  remain  in  solution.     (Hess  and  Campbell, 
C.  N.,  Ixxxi,  158.     Engles,  J.  S.  C.  I.,  1898,  796.) 

(/)  Electrolytic  separation  of  iron  by  amalgamation  with  mercury  cathode  and 
determining  aluminum  in  the  solution.  (Kretzschmar,  J.  S.  C.  I.,  1890,  1064; 
Kolin  and  Woodgate,  J.  S.  C.  L,  1889,  260.) 

Phosphoric  Acid.  In  presence  of  phosphoric  acid,  the  phosphates  of  iron 
and  alumina  together  with  the  phosphates  of  the  other  elements  of  the  group 
and  those  of  the  alkaline  earths  will  be  precipitated  upon  making  the  solution 
alkaline  with  ammonia.  Should  iron  and  alumina  be  the  only  elements  of  these 
two  groups  present  in  the  solution,  they  may  be  precipitated  together  as  phos- 
phates, iron  determined  by  titration  and  calculated  to  the  phosphate  salt, 
and  alumina  obtained  by  difference.  Occasionally,  however,  it  is  necessary  to 
remove  phosphoric  acid. 

Removal  of  Phosphoric  Acid.  The  material  is  fused  with  about  six  times 
its  weight  of  a  mixture  of  4  parts  Na2C03  and  1  part  Si02  (silex),  and  the 
melt  extracted  with  water  containing  ammonium  carbonate.  Iron  and  aluminum 
remain  on  the  filter,  upon  filtration,  while  sodium  phosphate  passes  into  solu- 
tion. Both  the  precipitate  and  filtrate  contain  silica.  The  precipitate  of  iron 
and  alumina  is  dissolved  in  hydrochloric  acid  and  taken  to  dryness,  the 
residue  dehydrated  as  usual,  then  treated  with  dilute  hydrochloric  acid  and 
silica  filtered  off.  The  solution  contains  iron  and  aluminum  in  form  of  chlorides. 

Separation  of  Aluminum  from  Chromium.  The  solution  is  made  strongly 
alkaline  with  sodium  or  potassium  hydroxides  and  chromium  oxidized  by 
passing  in  chlorine  gas  or  by  adding  bromine.  The  solution  is  now  acidified 
with  nitric  acid  and  aluminum  hydroxide  precipitated  by  addition  of  ammo- 
nium hydroxide,  chromium  remaining  in  solution  as  a  chromate. 

Separation  of  Aluminum  from  Manganese,  Cobalt,  Nickel,  Zinc,  the 
Alkaline  Earths,  and  Alkalies.  Iron  and  aluminum  are  precipitated  as  basic 
acetates,  the  other  elements  passing  into  solution.  Details  of  the  procedure 
are  given  under  the  basic  acetate  method  on  page  2CO. 

In  absence  of  phosphates,  these  elements  do  not  interfere  in  the  determi- 
nation of  aluminum  by  precipitation  as  the  hydroxide. 

Separation  of  Aluminum  from  Titanium.  Details  of  the  procedure  are 
given  under  "Titanium." 

Separation  of  Aluminum  from  Uranium.  Aluminum  is  precipitated  as 
a  carbonate  in  presence  of  a  large  amount  of  ammonium  salts  by  addition  of 
a  large  excess  of  ammonium  carbonate  and  ammonium  sulphide,  while  uranium 
remains  in  solution  as  the  complex  compound  U03(C03)3(NH4)4. 

Separation  from  Glucinum.  Aluminum  is  soluble  in  the  fixed  alkalies  and 
remains  in  solution  on  boiling;  glucinum  also  dissolves,  but  is  precipitated  on 
boiling.  Glucinum  is  soluble  in  an  excess  of  ammonium  carbonate,  aluminum 
is  not. 

For  additional  separations  see  chapter  on  element  in  question. 


ALUMINUM  7 

GRAVIMETRIC    METHODS    FOR    THE    DETERMINATION 

OF  ALUMINUM 

There  are  two  general  procedures  for  the  gravimetric  determination  of 
aluminum.  A.  Direct  determination,  when  it  is  possible  to  precipitate  the 
hydroxide  or  phosphate  of  the  element,  free  from  impurities.  B.  Indirect  deter- 
mination when  the  element  is  precipitated  and  weighed  along  with  iron,  the 
latter  then  determined  by  titration  and  aluminum  estimated  by  difference. 

Determination    by  Hydrolysis   of  an  Aluminum  Salt  with  Am- 
monium Hydroxide 

Principle.  The  method  depends  upon  the  hydrolysis  of  a  soluble  salt  of  alumi- 
num by  neutralizing  the  free  and  combined  acid  with  ammonia.  This  hydrolysis 
takes  place  in  presence  of  ammonium  chloride,  which  prevents  the  precipitation 
of  magnesium  hydroxide  by  NH4OH,  the  common  ion,  NH4+,  repressing  the 
ionization  of  the  base,  NH4OH.  (See  Notes.)  The  direct  determination 
of  aluminum  by  this  procedure  excludes  the  presence  of  elements  undergoing 
hydrolysis  with  similar  conditions.  Iron,  chromium,  titanium,  zirconium,  thal- 
lium, cerium  interfere.  In  their  presence  a  separation  must  be  made. 

Reaction.     A1C13+3NH4OH  =  A1(OH),+3NH4C1. 

If  phosphoric  acid  is  present  in  the  solution  aluminum  will  be  precipitated 
as  the  phosphate,  A1P04. 

Procedure.  To  the  solution,  containing  aluminum,  free  from  phosphoric 
acid  and  the  elements  precipitated  by  ammonium  hydroxide,  are  added  10  cc. 
of  ammonium  chloride  (10%)  and  5  cc.  of  concentrated  nitric  acid.  The 
solution  is  diluted  to  about  150  cc.  and  heated  to  boiling.  Upon  cooling  slightly, 
carbonate-free  ammonium  hydroxide  is  added  slowly  from  a  burette  until  a 
slight  permanent  precipitate  forms,  and  then  drop  by  drop  until  the  solution 
reacts  alkaline  to  litmus  paper  and  the  odor  of  ammonia  is  faintly  perceptible. 
The  precipitate  is  allowed  to  settle  on  the  water  bath  for  a  few  minutes,  then 
filtered  hot  and  washed  first  several  times  by  decantation  and  finally  on  the 
filter  with  a  hob  solution  of  ammonium  nitrate.  (Twenty  cc.  strong  nitric 
acid  diluted  and  neutralized  with  ammonium  hydroxide  and  made  to  1000  cc.) 

The  precipitate  is  purified,  if  other  members  of  the  ammonium  ^sulphide 
group  and  following  groups  are  present,  as  the  gelatinous  precipitate  is  apt  to 
occlude  some  of  these.  This  is  accomplished  by  dissolving  the  precipitate  in 
a  small  amount  of  hot,  dilute  hydrochloric  acid,  1  :  1,  the  solution  being  caught 
in  the  beaker  in  which  the  first  precipitation  was  made.  The  precipitation  of 
the  hydroxide  is  repeated  exactly  as  is  stated  above.  The  precipitate,  washed 
free  of  chlorides  (AgN03  test),  is  drained  of  water  and  placed  together  with 
the  filter  paper  in  a  platinum  crucible. 

The  ignition  of  the  precipitate  is  conducted  slowly  at  first  until  the  paper 
is  thoroughly  charred,  the  heat  is  now  increased  to  the  full  power  of  the^Meker 
blast,  the  crucible  being  covered  to  prevent  mechanical  loss.  Blasting  for 
thirty  minutes  is  generally  sufficient  to  dehydrate  the  oxide,  A1203.  It  is  advis- 
able, however,  to  repeat  the  heating  until  the  weight  becomes  constant.  The 
residue  is  weighed  as  A1208. 

A1203X0.5303=A1. 


8  ALUMINUM 

NOTES.  Ammonia  should  be  free  from  carbonates.  Upon  long  standing  with 
frequent  exposure  to  air  the  ammonia  takes  up  CO2,  forming  carbonate  of  ammonia. 
Freshly  distilled  ammonia  will  be  pure,  the  carbonate  being  precipitated  by  addition 
of  lime  in  the  distilling  flask.  Ammonia  is  best  kept  in  a  ceresine  or  paraffine 
bottle.  It  will  then  remain  free  from  silica,  which  it  invariably  contains  when  con- 
fined in  glass  bottles. 

Long  heating  of  the  mixture  containing  the  aluminum  precipitate  is  objectionable. 

1.  The  solution  is  apt  to  become  acid  owing  to  the  decomposition  of  ammonium 
salts  and  the  volatilization  of  ammonia. 

2.  The  precipitate  will  become  slimy  and  will  be  difficult  to  wash  and  filter. 
It  is  preferaole  to  redissolve  and  again  precipitate  if  this  condition  occurs. 

3.  The  COj  of  the  air  is  apt  to  be  absorbed  by  the  solution,  causing  the  precip- 
itation of  calcium  carbonate,  etc.,  should  the  solution  be  exposed  for  any  length 
of  time. 

4.  Silica  from  the  beaker  will  contaminate  the  precipitate. 

Hence  it  is  advisable  to  filter  as  soon  as  possible  after  making  the  precipitation 
of  Al(OH),. 

5.  and  S.  No.  589,  black  band  filter  paper  filters  well  and  may  be  used  to  ad- 
vantage with  precipitates  of  the  nature  of  aluminum  hydroxide.     B.  and  A.  No.  B. 
filter  is  also  good. 

Washing  the  precipitate  with  ammonium  nitrate  prevents  the  aluminum  from 
passing  through  the  filter  and  keeps  it  from  packing.  It  favors  the  formation  of 
the  insoluble  hydrogel  form  of  the  hydrate  while  preventing  the  formation  of  the 
soluble  hydrosol.  Ammonium  chloride  may  be  used  in  place  of  nitrate.1 

Aluminum  hydroxide  is  soluble  in  acids  and  alkalies.  The  ignited  oxide, 
Aljpi,  is  insoluble  in  acetic  acid  but  is  soluble  in  mineral  acids  and  the  fixed  alkalies, 
It  is  rendered  very  difficultly  soluble  in  acids  by  strong  ignition,  generally  requiring 
fusion  with  sodium  carbonate  or  potassium  bisulphate  with  subsequent  acid  treat- 
ment to  effect  solution. 

AljO,,  m.w.,  102.2;  sp.gr.,  3.73  to  3.99;  m.p.,  2020°  C. 

A  yellow  or  reddish  precipitate  indicates  the  presence  of  iron,  an  element 
frequently  present  with  aluminum.  Should  this  be  the  case,  iron  must  be  deter- 
mined, either  in  a  separate  portion  of  the  sample,  or  in  the  residue  obtained  by  the 
procedure  outlined.  The  amount  of  Fe2Oi  is  subtracted  from  the  total  residue, 
and  AljOi  obtained  by  difference. 

If  phosphoric  acid  is  present  the  phosphate  of  alumina  will  precipitate  together 
with  the  phosphates  of  elements  insoluble  in  alkaline  solutions.  Should  phosphoric 
acid  be  present  either  its  removal  is  essential,  or  the  phosphate  method  for  alumina 
should  be  followed. 

Fluorides  hinder  the  precipitation  of  aluminum.2  Evaporation  to  dry  ness  and 
heating  the  residue  to  redness  will  transform  fluorides  to  oxides  and  overcome  this 
difficulty. 

Sulphates  tends  to  hold  up  aluminum  from  precipitation  and  a  certain  amount  of 
sulphuric  acid  is  occluded  by  the  aluminum  hydroxide  precipitate.  Magnesium  is 
more  apt  to  precipitate  with  alumina  in  presence  of  sulphates.3  Ammonium  chloride 
greatly  lessens  this  difficulty. 

Traces  of  alumina  may  be  recovered  from  the  filtrate  by  evaporation  to  dryness, 
ignition  and  resolution  with  HC1.  The  A1(OH)»  is  now  precipitated  with  NH4OH. 

Since  alumina  absorbs  moisture  from  the  air,  the  crucible  containing  this  compound 
should  be  kept  covered  in  a  desiccator  until  weighed. 

Ammonium  hydroxide,  in  presence  of  sufficient  NH4C1,  will  not  precipitate  Mg(OH)2, 
since  the  addition  of  NH4C1  increases  the  ammonium  ions  in  the  solution  and,  by  the 
common  ion  effect,  represses  the  hydroxyl  ions  of  the  base,  NH4OH,  so  that  there  are 
insufficient  hydroxyl  ions  for  the  solubility  product  of  Mg(  OH)2  to  be  exceeded;  there- 
fore magnesium  remains  in  solution.  A  discussion  of  the  theory  of  solubility  product 
and  law  of  mass  action  may  be  found  in  the  author's  work  on  Qualitative  Chemical 
Analysis,  published  by  D.  Van  Nostrand  Co.  Reference  is  also  made  to  Vol.  I  of  The 
Elements  of  Qualitative  Chemical  Analysis,  by  Julius  Stieglitz,  publ.  by  the  Century  Co. 

1  W.  Blum,  Jour.  Am.  Chem.  Soc.,  38,  7,  1282,  1916.    C.  F.  Sidener  and  Earl  Petti- 
john,  Jour.  Ind.  Eng.  Chem.,  8,  8,  714,  Aug.,  1916. 

2  E.  P.  Veitch,  Jour.  Am.  Chem.  Soc.,  22,  246,  1900.    W.  R.  Bloor,  ibid.,  29,  1603 
1907.    L.  P.  Curtman  and  H.  Dubin,  ibid.,  34,  1485,  1912. 


ALUMINUM  9 

Determination  of  Aluminum  by  Hydrolysis,  Neutralizing  the 
Mineral  Acid  by  Addition  of  a  Salt  of  a  Weak  Acid. 
Sodium  Thiosulphate  Method  1 

4 

If  a  salt  of  a  weak  acid  and  strong  base  is  added  to  a  neutral  or  slightly  acid 
solution  of  an  ^  aluminum  salt  containing  a  mineral  acid,  transposition  takea 
place  and  aluminum  is  hydrolyzed. 

Reaction.    2AlCl3+3Na2S203+3H2O  =2Al(OH)3+6NaCl+3S02+3S. 

Procedure.  If  the  solution  is  acid,  dilute  ammonia  is  added  until  a  pre- 
cipitate forms  that  dissolves  with  difficulty,  but  not  enough  ammonium  hydroxide 
to  cause  a  permanent  precipitation.  The  solution  is  diluted  so  that  it  con- 
tains about  0.1  g.  Al  per  200  cc.,  then  an  excess  of  sodium  thiosulphate  is  added, 
and  the  solution  is  boiled  free  of  S02.  A1(OH)3  precipitates  along  with  free 
sulphur.  If  iron  is  absent  it  is  advisable  to  add  a  few  drops  of  ammonium 
hydroxide  until  the  solution  has  a  slight  odor  of  ammonia.  The  mixture  again 
boiled  is  filtered  and  the  residue  of  A1(OH)3  and  sulphur  washed  with  hot  water 
containing  ammonium  chloride  or  nitrate.  The  precipitate  is  dried,  separated 
from  the  filter,  the  latter  ignited  and  the  ash  added  to  the  main  precipitate. 
Alumina  is  now  determined  by  blasting  to  constant  weight,  the  residue  being 
weighed  as  A1303. 

NOTES.  The  above  method  may  be  employed  for  separation  of  aluminum  from 
iron,  the  addition  of  ammonia,  following  the  neutralization  of  the  mineral  acid  by 
thiosulphate  being  omitted.  The  precipitation  of  A1(OH)3  by  this  procedure  gives 
a  more  dense  and  better  filtering  precipitate  than  does  ammonia  alone. 

NOTE.  G.  Wynkoop  suggests  the  use  of  sodium  nitrite  as  the  salt  of  a  weak  acid 
for  neutralizing  the  mineral  acid.2 

Reaction.     2A1C13 +6HOH  =  2A1(OH)3 +6HC1    and 

6HCl+6NaNO2  =  6NaCl+3H2O+3NO-f3NO2. 

Precipitation   of  Aluminum  as  a  Phosphate 

Principle.  This  procedure,  developed  by  Carnot,3  is  of  special  value  in 
determination  of  aluminum  in  iron  and  steel.  It  is  founded  on  the  reaction  that 
aluminum  is  precipitated  as  the  neutral  phosphate,  from  a  boiling  solution  faintly 
acid  with  acetic  acid.  Iron,  reduced  to  the  ferrous  condition  by  addition  of 
sodium  hyposulphite,  does  not  interfere. 

Procedure.  A  sample  of  10  grams  of  iron  or  steel,  in  a  platinum  dish,  covered 
with  a  piece  of  platinum  foil,  is  dissolved  by  addition  of  hydrochloric  acid. 
The  solution  is  diluted  to  about  100  cc.  and  filtered  into  a  flask,  the  residue  of 
carbon,  silica,  etc.,  is  washed  thoroughly  and  the  filtrate  is  neutralized  by 
addition  of  ammonium  hydroxide  and  ammonium  carbonate;  no  permanent 
precipitate  should  form.  A  little  sodium  hyposulphite  is  added,  and  when 
the  liquid,  at  first  violet,  becomes  colorless,  2  or  3  cc.  of  a  saturated  solu- 

1  Method  by  Chancel,  Compt.  rend.  (1858),  46,  987. 

2  J.  Am.  Ch.  Soc.,  19,  434  (1897).     The  method  may  be  found  in  Treadwell  and 
Hall  "  Quantitative  Analysis,"  4th  ed.,  p.  85. 

3  A.  Carnot,  Moniteur  Scientifique,  1891,  p.  14. 


10  ALUMINUM 

tion  of  sodium  phosphate  and  5  or  6  grams  of  sodium  acetate,  dissolved  in  a 
little  water,  are  added.  The  solution  is  boiled  until  free  of  sulphurous  acid  odor 
(about  three-quarters  of  an  hour).  The  solution  is  filtered  off  from  the  pre- 
cipitated aluminum  phosphate  (mixed  with  a  little  silica  and  ferric  phosphate) 
and  washed  with  boiling  water.  The  precipitate  on  the  filter  is  treated  with  hot 
dilute  hydrochloric  acid  the  filtrate  caught  in  a  platinum  dish,  and  then  evap- 
orated to  dryness  and  heated  at  110°  C.  for  an  hour  to  dehydrate  silica.  The 
residue  is  taken  up  with  dilute  hydrochloric  acid  and  the  solution  filtered  free 
of  silica.  Upon  dilution  to  about  100  cc.  with  cold  water,  the  solution  is  neu- 
tralized as  before,  a  little  hyposulphite  is  added  to  the  cold  solution  and  then 
a  mixture  of  2  grams  of  sodium  hyposulphite  and  2  grams  of  sodium  acetate. 
The  material  is  boiled  for  half  an  hour  or  more,  filtered  and  the  aluminum  phos- 
phate residue  washed  with  hot  water,  then  dried,  ignited  and  weighed  as  aluminum 
phosphate.  The  residue  contains  22.19%  Al. 

A1P04X0.2219  =  Al.    A1P04X0.4185  =  A1203. 

NOTE.     Properties  of  A1PO4,  m.w.,  122.14;  sp.gr.,  2.59;  infusible,  insoluble,  in  IlaO 
and  in  HXI^HsC^,  soluble  in  mineral  acids  and  in  alkalies;  white,  amorphous  salt. 


Precipitation  of  Aluminum  as  Aluminum  Chloride1 

Principle.  Gooch  and  Havens  found  that  aluminum  chloride  is  practically 
insoluble  in  a  mixture  of  concentrated  hydrochloric  acid  and  ether  saturated  with 
HC1  gas,  5  parts  of  A1C13.6H20  equivalent  to  1  part  of  A1203  dissolving  in  125,000 
parts  of  the  mixture.  The  method  serves  for  a  separation  of  aluminum  from 
iron,  berillium,  zinc,  copper,  mercury  and  bismuth,  the  chlorides  of  these  ele- 
ments being  soluble  under  the  above  conditions.  Barium,  however,  is  precipi- 
tated as  a  chloride  with  aluminum,  if  it  is  present  in  the  solution. 

Procedure.  To  the  concentrated  aqueous  solution  of  aluminum  is  added 
a  convenient  volume  of  strong  hydrochloric  acid  (15  to  25  cc.)  and  an  equal 
volume  of  ether.  The  mixture  is  best  placed  in  a  large  platinum  crucible, 
which  is  kept  cool  in  running  water.  HC1  gas  is  passed  into  the  solution  to 
saturation.  The  precipitated  chloride  of  aluminum  is  filtered  upon  asbestos 
in  a  weighed  Gooch  crucible  and  then  washed  with  a  mixture  of  ether  and  water 
1:1,  saturated  with  HC1  gas.  The  precipitate  is  dried  for  half  an  hour  at  150° 
C.,  then  covered  with  a  layer  of  C.P.  mercuric  oxide  (1  gram)  and  heated  at  first, 
gently  over  a  low  flame  (hood)  and  then  blasted  to  constant  weight.  The 
residue  is  weighed  as  A1208. 

NOTES.  HC1  gas  is  generated  by  dropping  strong  sulphuric  acid  into  concen- 
trated hydrochloric  acid  according  to  the  procedure  described  under  the  determina- 
tion of  arsenic  by  volatilization  as  arsenious  chloride.  The  gas  may  be  produced 
in  a  Kipp  generator  by  the  action  of  concentrated  sulphuric  acid  on  ammonium 
chloride. 

The  filtrate  from  aluminum  contains  iron,  berillium,  copper,  zinc,  etc.,  if  these 
are  present  in  the  original  solution.  If  much  iron  is  present  it  is  necessary  to  increase 
the  amount  of  ether  to  prevent  precipitation  of  the  ferric  salt. 

1  F.  A.  Gooch  and  F.  S.  Havens,  Am.  Jour.  Sci.  (4),  11,  416.  F.  A.  Gooch  "  Methods 
in  Chemical  Analysis." 


ALUMINUM  11 


VOLUMETRIC    METHODS    FOR    THE    DETERMINATION    OF 

ALUMINUM 

Volumetric  Determination  of  Combined  Alumina  in  Aluminum 
Sulphate  and  Aluminum  Salts 

Introduction.  Aluminum  salts  dissociate  in  hot  solutions  and  react  acid  to 
phenolphthalein  indicator;  the  acid  readily  combines  with  fixed  alkalies,  forming 
the  neutral  alkali  salt.  The  end  point  of  the  reaction  is  indicated  by  the  pink 
color  produced  upon  phenolphthalein  by  the  excess  of  alkali.  From  the  amount 
of  caustic  required  the  percentage  of  combined  A1203  may  be  calculated.  The 
following  reaction  takes  place : 

Al2(S04)3+6NaOH=2Al(OH)3+3Na2SO4. 

Procedure.  The  factor  weight,1  3.4067  grams,  is  dissolved  in  a  4-in.  casserole 
with  100  cc.  of  distilled  water,  1  cc.  of  phenolphthalein  indicator  added,  and 
the  sample  titrated  boiling  hot 2  with  N/2  NaOH,  added  from  a  chamber  burette, 
graduated  from  50  to  100  cc.  in  tenths  of  a  cc.1  The  solution  is  kept  boiling 
during  the  titration  and  is  constantly  stirred.  Towards  the  end  of  the  reaction 
the  alkali  is  added  cautiously  drop  by  drop  until  a  permanent  pink  color  is 
obtained. 

Cc.  of  NaOH  required  divided  by  4  =per  cent  combined  A1203.3 

Combined  Al203+free  A1203  = total  A1203. 

NOTES.  If  iron  is  present  a  correction  must  be  made  for  it  after  determining  the 
ferrous  and  ferric  forms  as  given  below. 

The  amount  of  phenolphthalein  indicator  used  should  be  the  same  in  each  deter- 
mination. An  excess  of  indicator  causes  low  results.  It  has  been  noted  in  case  of 
alums  where  iron  does  not  interfere  that  best  results  are  obtained  with  three  or  four 
drops  of  phenolphthalein  solution.  Iron  tends  to  mask  the  end  point,  hence  a  larger 
amount  of  indicator  is  necessary  if  this  is  present. 

Correction  for  Iron  if  Present.  Since  iron  salts  will  also  dissociate  and 
titrate  with  aluminum  salts,  by  this  method  a  correction  has  to  be  made  for  iron 
if  present.  Total  A1203  in  presence  of  iron  = 

combined  Al203-(FeOX.47+Fe203X.64)+basic  Al203+an  additive  factor. 
The  additive  factor  is  obtained  by  subtracting 

(Combined  Al203+basic  A1203)  -(FeOX.47+Fe203X.64)  volumetric, 
from  total  A1203  obtained  by  gravimetric  analysis  of  an  average  sample. 


1  Large  samples  must  be  taken  for  salts  containing  less  than  13  per  cent  A12O3  if 
the  chamber  burette  is  to  be  used.    E.g.,  potash  alum  twice  this  amount  is  advisable. 

2  Otto  Schmatolla,  Berichte,  xxxviii,  No.  4.    C.  N.,  91-2375-236  (1905). 

3  If  free  acid  is  present  (see  next  method),  the  equivalent  volume  in  terms  of  2  JN 
acid  must  be  deducted  from  the  total  titration  for  combined  alumina  before  dividing 
by  4. 


12  ALUMINUM 

Ferrous  Iron,  Ferric  Iron,  and  Total  Iro*_  A  five-gram  sample  is  dis- 
solved in  water  and  the  iron  oxidized  with  a  few  drops  of  strong  potassium 
permanganate  solution;  the  solution  should  be  pink;  the  excess  of  permanganate 
is  destroyed  by  a  drop  or  so  of  normal  oxalic  acid  solution  and  the  total  iron 
determined  by  stannous  chloride  solution  method  for  iron.  On  a  separate 
sample  ferric  iron  is  determined.  Ten  grams  of  the  sample  are  dissolved  in  an 
Erlenmeyer  flask  by  boiling  with  hydrochloric  acid,  2  :  1,  in  an  atmosphere  of 
COj  to  prevent  oxidation,  and  the  iron  titrated  with  standard  stannous  chloride. 
The  difference  between  total  iron  as  Fe203  and  ferric  oxide  =  ferrous  iron  in  terms 
of  Fe20i.  This  multiplied  by  .9  =  FeO. 

Combined  Sulphuric  Acid 

Provided  no  free  acid  is  present,  the  per  cent  combined  sulphuric  acid  in 
aluminum  sulphate  is  obtained  by  multiplying  the  cc.  caustic  titration  for  total 
alumina  by  0.72. 

In  case  free  acid  is  present,  the  per  cent  free  acid  deducted  from  total  acid 
found  by  titration  gives  combined  acid. 

Sulphuric  acid  combined  with  the  fixed  alkalies  is  not  titrated. 

Determination  of   Free  Alumina  or  Free  Acid  by  the  Potassium 

Fluoride  Method 

Introduction.  The  method  suggested  by  T.  J.  I.  Craig  (J.  S.  C.  I.  30, 
185),  has  been  modified  by  the  author,1  after  a  personal  investigation  of  the 
details  involved.  In  this  modified  form  it  has  been  used  successfully  as  a  rapid 
works  method.  Frequent  gravimetric  checks  on  a  large  number  of  determi- 
nations have  shown  it  to  be  accurate. 

The  procedure  is  based  upon  the  fact  that  an  excess  of  neutral  potassium 
fluoride  decomposes  aluminum  salts,  forming  two  stable  compounds,  which  react 
neutral  to  phenolphthalein,  while  the  free  acid  remains  unaltered,  the  fol- 
lowing reaction  taking  place: 


The  precipitate  A1F33KF  is  insoluble  in  an  excess  of  the  potassium  fluoride 
reagent  and  is  not  appreciably  attacked  by  acids  or  alkalies.  Although 
theoretically  about  7  parts  by  weight  of  potassium  fluoride  is  sufficient  to  com- 
bine with  1  part  of  aluminum  sulphate,  in  practice  it  is  advisable  to  use  twice 
this  amount. 

Reagents  Required.  Half  Normal  solutions  of  sulphuric  acid  and  potassium 
hydroxide,  (sodium  hydroxide  may  be  used.) 

Phenolphthalein  indicator,  0.1%  alcoholic  solution. 

Potassium  fluoride  solution;  made  by  dissolving  1000  grams  of  potassium  fluoride 
in  about  1200  cc.  of  hot,  CO2-free  water,  then  neutralizing  the  solution  with  hydro- 
fluoric acid  or  potassium  hydroxide  as  the  reagent  may  require,  using  5  cc.  of  phenol- 
phthalein as  indicator.  Dilute  sulphuric  acid  may  be  used  in  place  of  hydrofluoric 
acid  in  the  final  acid  adjustment  to  get  a  neutral  product.  One  cc.  of  the  solution 
in  10  cc.  of  CO2-free  water  should  appear  a  faint  pink.  The  concentrated  mix  is 
filtered  if  necessary  and  then  diluted  to  2000  cc.  with  CO2-free  water.  The  gravity 
will  now  be  approximately  1.32  or  about  35°  Be*.  One  cc.  contains  0.5  g.  potassium 
fluoride. 

*  W.  W.  Scott. 


ALUMINUM  13 


Method  of  Procedure 

Solids.  3.4067  g.  of  the  finely  ground  sample,  or  an  equivalent  amount  in 
solution  (100  cc.  of  sample  containing  34.067  g.  per  liter),  are  taken  for  analysis 
The  powder  is  dissolved  by  boiling  with  100  cc.  of  distilled  water  in  a4-in- 
casserole  with  clock  glass  cover.  To  the  hot  solution  10  cc.  of  N/2  H2S04  are  added, 
and  after  cooling  to  room  temperature,  20°  C.,  18  to  20  cc.  of  the  potassium 
fluoride  reagent  are  added  and  0.5  cc.  of  phenolphthalein.  The  solution  is  now 
titrated  with  N/2  KOH,  added  drop  by  drop  until  a  delicate  pink  color,  per- 
sisting for  one  minute,  is  obtained.  This  titration  shows  whether  the  product 
is  basic  or  acid. 

Basic  Alumina.  This  is  indicated  when  the  alkali  back-titration  is  less 
than  the  amount  of  acid  added.  Free  A1203  =  (cc.  H2S04 -cc.  KOH)  -i-4. 

Free  Acid.  In  case  the  back-titration  of  the  alkali  is  greater  than  the  cc.  of 
acid  added,  free  acid  is  present.  Free  acid  =  (cc.  KOH  -cc.  H2S04)  X0.72. 

Liquors.  In  works  control  it  is  necessary  to  test  the  concentrated  liquors 
to  ascertain  whether  these  are  basic  or  acidic.  The  Be*,  or  sp.gr.  of  the  solu- 
tion having  been  taken,  5  cc.  is  diluted  to  100  cc.  with  distilled,  C02-free  water. 
If  H2S  is  present,  it  is  expelled  by  boiling  the  solution,  which  should  be  acid,  10 
cc.  of  N/2  H2S04  is  added,  the  solution  cooled,  and  KF  and  phenolphthalein 
added  and  the  titration  made  as  in  case  of  solids. 

If  basic  (cc.  H2S04-cc.  KOH)  X (.0245 X. 3473 X 100) -f-  (5 Xsp.gr.)  =A1203. 

If  acid  (cc.  KOH  -cc.  H2S04X2.45)  -J- wt.  of  sample  =per  cent  free  acid  (H2S04). 

If  neutral,  the  back  titration  of  the  alkali  is  the  same  as  the  cc.  acid 
added. 

NOTES.  CO2-free  water  must  always  be  used  when  phenolphthalein  indicator  is 
necessary.  This  may  be  obtained  by  boiling  distilled  water  for  several  minutes  to 
expel  GO2.  This  reagent  is  very  sensitive  to  carbonic  acid. 

If  the  sample  does  not  dissolve  clear,  a  prolonged  digestion  with  previous  addi- 
tion of  the  required  amount  of  standard  acid,  10  cc.,  is  advisable.  This  is  best 
accomplished  in  an  Earlnmeyer  flask  with  a  return  condenser. 

Darkening  of  the  solution  during  the  back  titration  with  the  alkali,  indicates  that 
an  insufficient  amount  of  fluoride  has  been  added.  If  this  is  the  case  it  will  be  necessary 
to  make  a  fresh  determination. 

The  fluoride  method  has  the  following  advantages.  Determinations  may  be  made 
by  gas  or  electric  light.  The  end  point  is  easily  detected.  No  neutral  standard  is  nec- 
essary as  in  case  of  the  tint  method. 

Ammonium  salts,  if  present,  must  be  expelled  by  boiling  the  sample  with  an  excess 
of  standard  KOH  and  this  excess  determined. 

3.4067  =  2.45225  X- 3473X4  (i.e.  gms.H2SO4per  100  cc.  N/2  acid  multiplied  by  4  times 
factor  to  equivalent  A12O3).  Derived  directly  from  mol.  wt.  of  A12O3  =  (.1022X100X4) 
-T-  (6X2).  0.72  =  2.8792  -=-4  (i.e.  factor  A12O3  to  H2SO4+4). 

The  main  details  of  the  above  volumetric  procedures  were  worked  out  at  the  Laurel 
Hill  Laboratory,  General  Chemical  Company,  and  are  published  by  courtesy  of  this 
company. 

The  author  is  indebted  to  Mr.  W.  S.  Allen  for  his  criticism/and  valuable  suggestions 
in  the  volumetric  procedures  for  determining  alumina.3 


14  ALUMINUM 

Detection  and  Colorimetric  Estimation   of  Minute  Amounts  of 
Aluminum  with  Alizarin  S. — Atack's  Method  1 

The  reagent  used  is  a  0.1%  filtered  solution  of  commercial  alizarin  S,  the 
sodium  salt  of  alizarin  monosulphonic  acid  (yellow  with  acids,  purple  with 
alkalies). 

Test.  To  5  cc.  of  the  neutral  or  acid  solution  under  examination  is  added 
1  cc.  of  the  reagent,  and  then  ammonia  until  the  solution  is  alkaline,  as  shown 
by  the  purple  color.  The  solution  is  boiled  for  a  few  moments,  allowed  to 
cool,  and  then  acidified  with  dilute  acetic  acid,  when  red  coloration  or  pre- 
cipitate remaining  is  conclusive  evidence  of  the  presence  of  aluminum.  The 
red  calcium,  strontium,  barium,  zinc  and  magnesium  salts,  and  salts  of  other 
metals  later  than  Group  II  are  readily  soluble  in  cold  dilute  acetic  acid,  and  do 
not  interefere  with  the  coloration. 

Phosphates  or  chromium  do  not  interfere  and  comparatively  large  amounts 
of  iron  may  be  present  (0.003  milligram  Al  in  presence  of  1  milligram  ferric  iron, 
10  milligrams  chromium  salt).  In  presence  of  greater  quantities  of  iron  citric 
acid  is  added  to  keep  this  in  solution. 

Delicacy  of  the  Test.  One  part  of  aluminum  may  be  detected  in  10  million 
parts  of  water. 

Quantitative  Estimation,  Colorimetric 

Procedure.  The  original  solution  (5  to  20  cc.)  is  acidified  with  hydro- 
chloric or  sulphuric  acid.  Ten  cc.  of  glycerin  and  5  cc.  of  a  .1%  solution  of 
alizarin  S  are  added,  the  solution  made  up  to  about  40  cc.  with  water  (in  pres- 
ence of  much  iron  or  chromium  citric  acid  is  added  to  form  the  double  citrates) 
and  then  rendered  slightly  ammoniacal.  After  standing  for  five  minutes,  the 
cold  solution  is  acidified  with  dilute  acetic  acid,  the  alizarin  S  acting  as  indicator 
(red  coloration)  until  no  further  change  in  the  coloration  occurs.  The  liquid 
is  then  made  up  to  50  cc.  and  compared  with  a  standard.  Suitable  amounts 
of  aluminum  for  estimation  are  0.005  to  0.05  milligrams,  the  solution  under 
examination  being  suitably  diluted  if  necessary. 

BAUXITE  ANALYSIS2 

Characteristic  bauxites H2O  SiO2  Fe20s  A12O3  TiO2 

Arkansas 6.4%  1.43%  87.3%  3.99% 

Georgia 36%  9-15  1-14  42-62  1.8-2.3 

Tennessee 27 . 6  18 . 4  4.1  49 . 9 

Sampling.  The  bauxite  received  in  cars  is  sampled  during  the  unloading 
according  to  the  standard  procedure  for  ores.  If  the  sample  is  a  composite 
aliquot  parts  of  the  total  weights  are  taken  and  mixed,  e.g.,  suppose  three  cars 
contained  respectively  23,000,  32,500,  and  26,340  pounds,  then  the  aliquots 

1  F.  W.  Atack,  Jour.  Soc.  Chem. Ind.;  34, 936  (1915);  C.  A.  9;  23;  3186  (1915). 

2  Bauxite  is  the  only  ore  of  aluminum  of  commercial  importance.     Pure  alumina, 
corundum,  is  too  valuable  for  commercial  use.     Clay,  the  most  abundant  of  alumina- 
bearing  substances,  may  eventually  be  used  as  a  source  for  aluminum,  but,  by  the 
present  methods  of  extraction,  the  alumina  from  clay  is  not  commercially  available. 


ALUMINUM  15 

would  be  23,  32.5  and  26.34  pounds,  which  mixed,  would  make  a  representa- 
tive sample  of  the  shipment.  The  ore  is  broken  down,  quartered,  ground  down 
and  again  quartered.  The  moisture  is  determined  on  1000  grams,  dried  in 
the  oven  at  100°  C.  for  one  hour,  the  sample  being  spread  out  on  a  sheet  of 
manilla  paper.  The  dried  sample  is  placed  in  a  large  bottle  for  analysis. 

Procedure  for  Evaluation  of  the  Ore.  A  method  for  obtaining  in  solution 
the  available  alumina  and  soluble  constituents  of  bauxite  has  been  given  under 
Preparation  and  Solution  of  the  Sample. 

Insoluble  Residue.  The  residue  on  the  filter  paper  is  ignited  in  a  plat- 
inum dish  over  a  low  flame  until  the  paper  chars,  and  then  over  a  good  Meker 
blast  for  15  to  20  minutes. 

Weight  of  the  residue  X  20  =per  cent  insoluble  residue. 

Soluble  Alumina.  100  cc.  of  the  above  solution  (0.5  g.)  is  diluted  with  an 
equal  volume  of  water,  10  cc.  of  hydrochloric  and  2  cc.  of  nitric  acids  added 
and  the  solution  boiled.  Iron  and  alumina  are  now  precipitated  and  deter- 
mined in  the  usual  way. 

Soluble  Iron.  200  cc.  of  the  solution  (1.0  g.),  is  oxidized  by  adding  a 
few  crystals  of  potassium  chlorate  and  the  solution  taken  to  dryness.  The 
residue  is  taken  up  with  10  to  15  cc.  of  concentrated  hydrochloric  acid  and  again 
evaporated  to  dryness  to  expel  chlorine.  Then  taken  up  with  25  cc.  hydro- 
chloric acid  and  the  iron  determined  by  titration.  The  stannous  chloride  method 
is  used  for  samples  containing  less  than  5%  iron  and  the  dichromate  method 
for  ores  containing  over  5%. 

Determination  of  Total  Silica,  Titanium  Oxide,  Ferric  Oxide  and  Alumina 

The  method  by  the  Aluminum  Company  of  America  is  to  digest  1  gram  of 
the  dried  bauxite  in  90  cc.  of  an  acid  mixture  containing  12  parts  of  dilute  sul- 
phuric acid,  1  I  3,  together  with  6  parts  of  strong  hydrochloric  acid  and  2  parts 
of  nitric  by  volume,  to  this  are  added  10  cc.  of  concentrated  sulphuric  acid. 
The  mixture  is  heated  until  sulphuric  acid  fumes  are  evolved,  then  diluted  with 
water  and  filtered. 

Silica.  The  residue  is  ignited  and  the  ash  fused  with  potassium  bisulphate. 
The  cooled  fusion  is  taken  up  with  5  cc.  sulphuric  acid  and  20  cc.  of  water  and 
digested  until  only  a  white  residue  remains.  This  filtered  off,  washed  and 
ignited  =  Si02. 

Titanium  Oxide.  This  is  best  determined  colorometrically  on  a  0.1  gram 
sample  according  to  the  procedure  outlined  in  the  chapter  on  Titanium. 

Iron  and  Alumina.  These  are  determined  by  the  usual  procedure; — oxida- 
tion with  potassium  chlorate,  precipitation  with  ammonium  hydroxide  and 
ignition.  Iron  may  be  determined  in  a  separate  sample  (100  cc.  =0.5  g.) 
by  titration.  A1203  =  difference  between  weighed  oxides  and  Fe203,  after  sub- 
tracting Ti02  if  present. 


16  ALUMINUM 


DETERMINATION  OF  ALUMINUM   IN    IRON  AND  STEEL1 

The  method  is  especially  adapted  for  determination  of  aluminum  in  iron  and 
steel,  but  may  be  extended  to  iron  ores  and  materials  high  in  iron. 

Procedure.  Solution.  Ten  grams  of  iron  or  steel  are  dissolved  by  adding 
about  50  cc.  of  hot  hydrochloric  acid,  1:1,  preferably  in  a  platinum  dish,  covered 
with  a  platinum  foil. 

Precipitation.  When  the  solution  of  iron  is  complete,  it  is  diluted  to 
about  100  cc.  and  filtered  free  of  carbon,  silica,  etc.  Two  grams  of  sodium  phos- 
phate are  added  and  the  solution  neutralized  with  ammonium  hydroxide  or 
carbonate,  then  cleared  by  hydrochloric  acid  with  about  1  cc.  excess.  Twenty 
cc.  of  acetic  acid  are  now  added  and  the  solution  diluted  to  300  to  400  cc.  with 
hot  water  and,  on  boiling,  10  grams  of  sodium  thiosulphate  added.  The  solu- 
tion is  boiled  free  of  sulphurous  acid,  (no  odor  of  S02)  about  20  to  30  minutes 
being  necessary.  The  phosphate  is  filtered  off  and  washed  with  hot  water.  It 
is  again  dissolved  in  a  little  hydrochloric  acid  and  aluminum  reprecipitated  by 
neutralizing  with  ammonium  hydroxide  and  adding  about  1  gram  of  sodium 
phosphate  together  with  10  grams  of  sodium  thiosulphate,  following  the  above 
procedure.  The  precipitate  will  now  be  free  of  iron. 

Ignition  and  Calculation.  The  precipitate  and  filter  are  ignited  wet, 
first  over  a  low  flame,  then  gradually  increasing  the  heat  to  full  blast  of  a 
Meker  burner.  The  residue  contains  22.19%  Al  or  41.85%  of  A120,. 

Factor  A1P04  to  Al  =  .2219. 

Factor  A1P04  to  A1203  =  .4185. 

NOTES.  Interfering  substances.  Copper  may  be  removed  by  H2S.  Other  mem- 
bers of  this  group  will  also  be  eliminated. 

Manganese  and  nickel  are  eliminated  together  with  small  amounts  of  iron  at  the 
second  precipitation. 

Titanium  may  be  estimation  colorimetrically  or  separated  from  alumina. 

Vanadium,  if  present,  may  be  separated  according  to  directions  given  in  the  chapter 
on  Vanadium. 

Chromium  is  eliminated  by  fusion  of  the  mixed  phosphates  with  Na2C08,  extrac- 
tion with  water,  and  precipitation  of  aluminum  phosphate  by  adding  ammonium 
acetate  and  sodium  phosphate.  Chromium  remains  in  solution. 

ANALYSIS  OF  METALLIC  ALUMINUM2 
Determination  of  Silicon 

Acid  Mixture:    400  cc.  cone,  nitric  acid.     1200  cc.  cone,  hydrochloric  acid. 
600  cc.  cone,  sulphuric  acid.     1800  cc.  water. 

Fusion   Method 

Dissolve  1  gram  of  well  mixed  drillings  in  35  cc.  of  acid  mixture  using  a 
4^-inch  porcelain  dish  with  a  5-inch  cover  glass.  When  the  drillings  are  com- 
pletely dissolved,  evaporate  the  solution  not  only  to  fuming  but  to  complete 

1  Arnold  and  Ibbotson,  "Steel  Works  Materials."      Stillman,  "Engineering  Chem- 
istry."    "A  Rapid  Method  for  the  Determination  of  Aluminum  in  Iron  and  Steel," 
C.  N.,  61.  313.      "On  the  Determination  of  Minute  Quantities  of  Al  in  Iron  and 
Steel,"  J.  E.  Stead,  J.  S.  C.  I.,  1889,  956. 

2  Standard  Method  of  Analysis  of  the  Aluminum  Company  of  America.     By 
courtesy  of  Mr.  E.  Blough,  Chief  Chemist. 


ALUMINUM  17 

dryness,  and  bake.  This  insures  the  freedom  of  the  solution  from  hydrochloric 
and  nitric  acids,  and  the  complete  dehydration  of  the  silica.  Take  up  the 
residue  with  10  cc.  25  per  cent  sulphuric  acid  and  about  100  cc.  of  water;  boil 
to  complete  solution  of  the  sulphate,  filter,  wash  well  and  ignite.  Fuse  the 
residue  with  eight  to  ten  times  its  weight  of  sodium  carbonate  and  take  up  the 
fused  mass  in  a  porcelain  dish  with  sulphuric  acid  (1  I  1).  Evaporate  the 
resulting  solution  until  copious  fumes  are  evolved,  which  will  cause  the  separa- 
tion of  the  silica;  dilute  carefully,  boil,  filter,  wash  well  and  ignite  in  a  platinum 
crucible  and  weigh.  Treat  the  ash  with  hydrofluoric  acid  and  a  few  drops  of 
sulphuric  acid;  carefully  ignite  and  weigh.  The  difference  in  the  two  weights 
obtained  above  represents  the  silicon  as  silica. 

Calculate  the  silica  to  silicon  by  the  factor  0.4693. 

Graphitic  Silicon 

Aluminum,  sometimes  if  not  always,  contains  some  silicon  in  the  graphitic 
state;  this  graphitic  silicon  does  not  oxidize  to  Si02  on  ignition  and  is  not 
volatile  with  HF,  which  two  characteristics  distinguish  it  from  amorphous  silicon. 

To  determine  graphitic  silicon  the  mixture  of  Si  and  Si02  obtained  as  in  the 
solution  method  is  treated  in  a  weighed  platinum  crucible  with  2-3  drops  of 
H.S04  and  2-3  cc.  HF. 

The  brown  residue  of  Si  remaining  is  strongly  ignited  and  weighed;  the 
silicon  remaining  is  that  which  was  in  the  metal  in  the  graphitic  state. 

Determination  of  Iron 

Permanganate  Method 

Cool  the  filtrate  obtained  from  solution  of  the  sample  in  acid  mixture 
(see  page  16)  and  reduce  the  iron  present  by  passing  the  solution  through  a  Jones 
reductor.  Titrate  immediately  with  a  solution  of  potassium  permanganate  of 
such  strength  that  1  cc.  equals  0.0010  gram  iron. 

In  all  cases  the  precautions  given  for  use  of  the  Jones  reductor  should  be 
observed,  and  explicit  directions  given  in  the  chapter  on  Iron,  carefully  followed. 
A  blank  determination  is  made  by  carrying  out  a  regular  iron  determination 
with  the  metal  sample  omitted.  The  amount  of  potassium  permanganate  re- 
quired to  give  the  blank  a  distinct  color  is  subtracted  from  the  amount  re- 
quired to  give  the  same  color  to  each  reduced  solution. 

The  author  acknowledges  his  indebtedness  to  Mr.  W.  S.  Allen,  Mr.  J.  P.  Kelly  and 
Dr.  F.  E.  Hale  for  review  and  criticism  of  the  subject. 


ANTIMONY 

WILFRED  W.  SCOTT 

Sbivt.wt.  ±20.2;    sp.gr.  6.631;     m.p.  630°C2;  b.p.  1440°C1;    oxides,  SbaO,, 

Sb;O4,  Sb2O6. 

DETECTION 

Hydrogen  Sulphide  precipitates  the  orange-colored  sulphide  of  antimony 
from  fairly  strong  hydrochloric  acid  solutions  (1  :  4)  in  which  several  mem- 
bers of  the  group  remain  dissolved.  Arsenic  is  also  precipitated.  The  latter 
may  be  removed  by  boiling  the  solution  containing  the  trichloride,  AsCl3  being 
volatile. 

If  antimony  is  already  present  as  a  sulphide,  together  with  other  elements 
of  the  hydrogen  sulphide  group,  it  may  be  dissolved  out  by  treating  the 
precipitate  with  sodium  hydroxide,  potassium  hydroxide,  sodium  sulphide, 
ammonium  polysulphide  in  solution.  Antimony  sulphide  is  reprecipitated 
upon  acidifying  the  filtrate.  Arsenic  and  tin  will  also  be  precipitated  with 
antimony  if  they  are  present  in  the  original  precipitate.  Should  a  separation 
be  necessary,  the  precipitate  is  dissolved  with  hot  concentrated  hydrochloric 
acid,  with  the  addition  of  crystals  of  potassium  chlorate,  from  time  to  time, 
until  the  sulphides  dissolve.  The  solution  is  placed  in  a  Marsh  apparatus,  pure 
zinc  added  and  the  evolved  gases  passed  into  a  neutral  solution  of  silver  nitrate. 
The  black  precipitate  of  silver  antimonide  and  metallic  silver  are  filtered  off, 
washed  free  of  arsenous  acid,  and  the  antimonide  dissolved  in  strong  hydro- 
chloric acid  (silver  remains  insoluble).  The  orange-colored  antimony  sulphide 
may  now  be  precipitated  by  diluting  the  solution  with  water  and  passing  in 
H2S  gas  to  saturation. 

Minerals  which  contain  antimony,  when  heated  alone  or  with  3  to  4  parts 
of  fusion  mixture  (K2C03  and  Na2C03),  on  charcoal,  yield  dense  white  fumes, 
a  portion  of  the  oxide  remaining  as  a  white  incrustation  on  the  charcoal.  A 
drop  of  ammonium  sulphide  placed  upon  this  sublimate  gives  a  deep  orange  stain. 

Hydrolysis.  Most  of  the  inorganic  antimony  salts  are  decomposed  by 
water,  forming  insoluble  basic  salts,  which  in  turn  break  down  to  the  oxide  of 
antimony  and  free  acid.  An  excess  of  tartaric  acid  prevents  this  precipitation. 

Traces  of  Antimony.  Nascent  hydrogen  liberated  by  the  action  of  zinc 
and  hydrochloric  or  sulphuric  acid  reacts  upon  antimony  compounds  with  the 
formation  of  stibine.  This  gas  produces  a  black  stain  on  mercuric  chloride  or 
silver  nitrate  paper.  Details  of  the  procedure  are  given  under  the  quantita- 
tive method  for  determining  minute  amounts  of  antimony. 

Distinction  between  Antimonous  and  Antimonic  Salts. 

Chromates  form  with  antimonous  salts  green  chromic  salts  and  antimonic  salts. 

Potassium  Iodide  reduces  antimonic  salts,  free  iodine  being  liberated. 

1  Van  Nostrand's  Chem.  Annual,  Olsen,  3d  Ed. 
1  Cir.  35,  U.  S.  Bureau  of  Standards. 
18 


ANTIMONY  19 


ESTIMATION 

The  determination  of  antimony  is  required  in  the  evaluation  of  antimony 
ores — stibnite,  Sb2S3;  valentinite,  Sb203,  etc.  It  is  generally  required  in  the 
complete  analysis  of  minerals  of  nickel,  lead,  copper,  silver,  in  which  antimony 
generally  occurs  as  a  sulphide.  The  determination  is  required  in  the  analysis 
of  Britannia  metal,  bearing  and  antifriction  metals,  type  metal  and  hard  lead* 
in  the  analysis  of  certain  mordants,  antimony  salts,  vulcanized  rubber,  etc.  It 
is  looked  for  as  an  undesirable  impurity  in  certain  food  products. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  the  substance  containing  antimony  it  must  be  remembered 
that  metallic  antimony  is  practically  insoluble  in  cold  dilute  hydrochloric,  nitric 
or  sulphuric  acid  and  the  oxides,  Sb203  or  Sb205,  are  precipitated  in  strong  nitric 
acid.  The  element,  however,  is  readily  soluble  in  hydrochloric  acid  contain- 
ing an  oxidizing  agent,  such  as  nitric  acid,  potassium  chlorate,  chlorine,  bromine, 
etc.  The  oxides  of  antimony  are  soluble  in  hydrochloric  acid  and  the  caustic 
alkalies. 

Solution  of  Sulphide  Ores,  Low-grade  Oxides,  etc.1 

0.5  to  1  gram  of  the  finely  ground  ore,  placed  in  a  Kjeldahl  flask,  is 
mixed  with  5  to  7  grams  of  ammonium  sulphate,  1  gram  of  potassium  sul- 
phate, and  10  cc.  of  strong  sulphuric  acid.  About  0.5  gram  of  tartaric  acid, 
or  a  piece  of  filter  paper,  is  added  to  reduce  arsenic  and  antimony  and  the  mixture 
heated,  gradually  at  first,  and  then  with  the  full  Bunsen  flame.  The  heating 
is  continued  until  the  carbon  is  completely  oxidized  and  most  of  the  free  acid 
driven  off,  leaving  a  clean  fusion  from  which  ammonium  sulphate  is  volatilizing. 
The  melt  is  now  cooled  over  the  bottom  and  sides  of  the  flask  by  gently  rotating 
during  the  cooling. 

About  50  cc.  of  dilute  hydrochloric  acid  (1:1)  are  added  and  the  melt  dis- 
solved by  warming  gently.  The  contents  of  the  Kjeldahl  flask  are  transferred 
to  an  Erlenmeyer  flask,  the  Kjeldahl  being  rinsed  out  with  25  cc.  of  strong 
hydrochloric  acid.  Arsenic  sulphide  may  now  be  precipitated  with  H2S  from 
the  strongly  acid  solution,  whereas  antimony,  etc.,  remain  in  solution.  The 
sulphide  is  filtered  off  through  a  double  filter,  that  has  been  moistened  with 
hydrochloric  acid  (2:1),  a  platinum  cone  supporting  the  filter  to  prevent  its 
breaking.  The  flask  is  rinsed  out  with  hydrochloric  acid  (2:1).  The  pre- 
cipitate is  washed  at  least  six  times  with  the  acid.  Antimony  passes  into  the 
filtrate  together  with  other  elements  of  the  ore. 

The  filtrate  is  diluted  with  double  its  volume  of  warm  water  and  then  is 
saturated  with  hydrogen  sulphide.  Antimony  sulphide,  together  with  other 
elements  of  the  Hydrogen  Sulphide  Group,  will  precipitate.  These  are  washed 
with  hydrogen  sulphide  water.  Antimony  sulphide  may  now  be  dissolved  by 
addition  of  sodium  sulphide  and  caustic  solution  (separation  from  Cu,  Pb,  Cd, 
Bi,  etc.)  (5  to  10  cc.  of  a  mix  of  60  grams  Na2S  with  40  grams  of  NaOH 
diluted  to  1000  cc.). 

1  Method  of  A.  H.  Low  modified. 


20  ANTIMONY 

The  solution  containing  the  antimony  is  treated  with  about  2  grams  of 
potassium  sulphate  and  10  cc.  of  strong  sulphuric  acid  and  heated  as  before, 
to  destroy  liberated  sulphur  and  expel  most  of  the  free  acid.  The  melt  is  dis- 
solved in  hydrochloric  acid,  and  the  antimony  titrated  according  to  one  of  the 
volumetric  procedures  given  under  "  Volumetric  Methods." 

NOTE.  An  insoluble  residue  remaining  from  the  acid  extraction  of  the  first  melt 
may  be  dissolved  by  fusion  with  sodium  hydroxide  and  extraction  of  the  melt  with  hot 
water.  If  a  precipitate  forms  when  this  alkaline  solution  is  acidified  with  hydrochloric 
acid,  the  presence  of  barium  sulphate  is  indicated. 

Decomposition  of  the  Ores  by  Fusion  with  Sodium  Hydroxide. 

Oxides.  0.5  to  1  gram  of  the  powdered  ore  is  mixed  with  about  10 
grams  of  sodium  hydroxide  and  placed  in  a  thin-walled  iron  crucible  of  60  cc. 
capacity.  It  is  advisable  to  fuse  a  portion  of  the  alkali  hydroxide  in  the  cru- 
cible with  a  pinch  of  potassium  nitrate  and  then  add  the  ore  mixed  with  the 
remainder  of  the  sodium  hydroxide.  The  covered  crucible  is  heated  until  the 
fusion  becomes  homogeneous.  The  melt  is  poured  out  on  a  large  nickel  crucible 
cover  or  shallow  dish.  On  cooling,  the  cake  is  detached  and  placed  in  a  cas- 
serole containing  water,  any  adhering  cake  on  the  cover,  or  melt  remaining  in 
the  iron  crucible,  being  dissolved  with  dilute  hydrochloric  acid  and  added  to 
the  sample  in  the  casserole.  About  30  to  40  cc.  of  strong  hydrochloric  acid  are 
now  added  and  the  mixture  heated  (casserole  covered)  until  the  melt  has  dis- 
solved. Two  to  3  grams  of  tartaric  acid  having  been  added  to  keep  anti- 
mony dissolved,  the  solution  is  diluted  to  about  300  cc.,  and  antimony  is  then 
precipitated  as  the  sulphide  with  hydrogen  sulphide.  The  treatment  of  the 
precipitate  at  this  stage  has  been  given  in  the  " Solution  of  Sulphide  Ores." 

Sulphides.  Howard  and  Harrison  l  recommend  the  following  procedure 
for  fusion  of  sulphide  ores  with  caustic:  0.5  gram  of  the  powdered  ore  is  fused 
with  a  mixture  of  8  grams  of  sodium  carbonate  and  sodium  peroxide,  1:1, 
in  a  nickel  crucible.  The  cooled  melt  is  dissolved  with  sufficient  hydrochloric 
acid  to  neutralize  the  alkali  and  about  15  cc.  of  strong  acid  added  in  excess. 
The  solution  is  diluted  to  250  cc.,  antimony  being  kept  in  solution  by  addition 
of  potassium  chlorate.  An  aliquot  portion  of  the  solution  is  taken,  antimony 
reduced  by  metabisulphite  and  titrated  with  iodine. 

Treatment  of  Speisses,  Slags,  Mattes,  etc.2  0.5  to  2  grams  of  the 
sample  is  treated  with  10  to  15  cc.  of  strong  nitric  acid  and  the  mixture  taken 
to  dry  ness.  Fifteen  cc.  of  strong  hydrochloric  acid  are  added  and  the  sample 
transferred  to  a  350-cc.  flask,  additional  hydrochloric  acid  being  used  to  wash 
out  the  beaker.  Arsenic  is  precipitated  from  the  strong  acid  solution  as  the 
sulphide,  and  antimony  determined  in  the  filtrate. 

Solution  of  Alloys.  Alloys  are  generally  decomposed  by  treatment  with 
mixtures  of  hydrochloric  acid  together  with  an  oxidizing  agent — nitric  acid, 
potassium  chlorate,  bromine,  etc.  The  subject  is  taken  up  in  detail  in  the  chapter 
on  alloys. 

The  alloy  drillings  are  treated  with  strong  hydrochloric  acid,  a  little  bro- 
mine added,  and  the  mixture  heated  until  the  alloy  dissolves,  additional  bromine 
being  added  from  time  to  time  if  necessary.  The  excess  bromine  is  removed 
by  heating  gently  to  boiling.  The  higher  oxides  are  reduced  by  addition  of 

1  Phar.  Jour.,  1909,  83,  147. 

2  H.  E.  Hooper's  method. 


ANTIMONY  21 

sodium  metabisulphite  and  the  sulphides  precipitated,  as  usual,  with  hydrogen 
sulphide.  Arsenic  may  now  be  volatilized  by  boiling,  and  antimony  titrated 
with  iodine  or  potassium  bromate. 

Alloys  of  Antimony,  Lead  and  Tin.  0.5  to  1  gram  of  the  finely  divided 
alloy  is  warmed  with  100  cc.  of  strong  hydrochloric  acid  until  the  action  sub- 
sides. Solid  iodine  is  now  added,  in  small  quantities  at  a  time,  until  the  alloy 
completely  dissolves.  The  excess  of  iodine  is  now  removed  by  boiling  and  the 
small  amount  of  free  iodine  remaining  neutralized  with  a  few  drops  of  a  weak 
solution  of  sodium  thiosulphate.  Although  tin  is  oxidized  to  the  higher  state, 
antimony  is  not  oxidized  by  iodine  in  acid  solution  beyond  the  trivalent  form. 
The  solution  may  now  be  titrated  with  standard  iodine  in  presence  of  an  excess 
of  sodium  bicarbonate  according  to  the  procedure  given  under  the  volumetric 
methods. 

Hard  Lead.  The  method  of  solution  and  titration  are  given  under  "  Potas- 
sium Bromate  Method  for  Determining  Antimony." 

Antimony  in  Rubber  Goods.1  Three  grams  of  the  finely  rasped  rubber 
are  treated  in  a  Kjeldahl  flask  with  40  to  45  cc.  of  strong  sulphuric  acid.  A 
small  quantity  of  mercury  or  mercury  salt  is  added,  together  with  a  small  piece 
of  paraffine  wax.  The  mixture  is  heated  until  che  rubber  is  dissolved  and  the 
black  liquid  begins  to  clear.  Two  to  4  grams  of  potassium  sulphate  are  then 
added  and  the  heating  continued  until  a  colorless  or  pale  yellow  liquid  is  obtained. 
After  cooling,  1  to  2  grams  of  potassium  metabisulphite  are  added  and  an  excess 
of  tartaric  acid.  The  liquid  is  diluted  sufficiently  to  prevent  the  charring  of 
the  tartaric  acid  and  boiled  until  the  odor  of  sulphurous  acid  has  disappeared. 
A  few  cc.  of  dilute  hydrochloric  acid  are  added,  the  liquid  diluted  to  200  cc., 
filtered  through  a  dry  filter,  and  195  cc.  titrated  either  with  iodine  or  with 
potassium  bromate  (the  latter  in  acid  solution),  as  described  under  the  volu- 
metric procedures. 

SEPARATIONS 

Separation  of  Antimony  (together  with  Members  of  the  Hydrogen  Sul- 
phide Group),  from  Iron,  Chromium,  Aluminum,  Cobalt,  Nickel,  Manganese, 
Zinc,  the  Alkaline  Earths,  and  Alkalies.  The  acid  solution  of  the  elements 
is  saturated  with  hydrogen  sulphide,  the  elements  of  the  Hydrogen  Sulphide 
Group  are  precipitated  as  sulphides,  the  other  elements  remaining  in  solution. 
Antimony  sulphide  may  be  precipitated  from  an  hydrochloric  acid  solution  con- 
taining 15  cc.  of  strong  acid  per  100  cc.  of  solution;  lead  and  cadmium  are 
incompletely  precipitated. 

Separation  of  Antimony  (together  with  Arsenic  and  Tin),  from  Mer- 
cury, Copper,  Bismuth,  Cadmium  and  Lead.  The  sulphides  of  antimony, 
arsenic,  and  tin  are  soluble  in  a  mixture  of  sodium  hydroxide  and  sodium  sul- 
phide, the  soluble  sulpho  salts  being  formed,  mercury,  copper,  bismuth,  cadmium, 
and  lead  remaining  as  insoluble  sulphides.  The  following  procedure  may  be 
used  for  alloys  free  from  members  of  other  groups.  The  acid  solution  is  treated 
with  3  to  5  grams  of  tartaric  acid  and  diluted  slightly  (more  tartaric  acid  being 
added  if  the  solution  becomes  turbid),  then  poured  into  300  cc.  of  a  fixture  of 
sodium  sulphide  and  sodium  hydroxide  (150  cc.  of  the  mix  described  under 

1 W.  Schmitz,  Chem.  Zentralbl.,  1911,  ii,  1710.    Analyst,  1912,  p.  64. 


22  ANTIMONY 

"Solution  of  Sulphide  Ores"  diluted  to  300  cc.).  The  mixture  is  warmed  and 
the  insoluble  sulphides  allowed  to  settle  out.  The  solution  is  filtered  free  of 
the  precipitate  and  the  latter  washed.  The  filtrate  is  acidified  with  hydro- 
chloric or  sulphuric  acid  and  saturated  with  hydrogen  sulphide.  The  sul- 
phides of  arsenic,  antimony  and  tin  are  now  filtered  off  and  treated  as  described 
later. 

Separation  of  Arsenic,  Antimony,  and  Tin.  The  sulphides  may  be  dis- 
solved in  concentrated  hydrochloric  acid  by  addition  of  potassium  chlorate  to 
oxidize  the  sulphur  to  sulphuric  acid.  This  oxidation  may  be  effected  in  the 
alkaline  solution  of  the  sulpho  salts  by  addition  of  30%  hydrogen  peroxide 
in  small  portions  until  the  yellow  solution  is  completely  decolorized  and  then 
1  to  2  cc.  in  excess,  the  solution  then  boiled  to  completely  oxidize  the  sul- 
phides to  sulphates  and  to  remove  the  excess  of  peroxide.  The  solution  is 
then  acidified,  the  precipitation  of  the  sulphides  and  the  subsequent  filtration 
and  resolution  being  avoided. 

Removal  of  Arsenic.  This  may  be  accomplished  by  volatilizing  arsenic  as 
arsenic  trichloride  in  a  strong  hydrochloric  solution  by  boiling.  If  arsenic  is 
to  be  determined  the  procedure  given  under  the  chapter  on  arsenic  is  followed, 
the  arsenic  being  distilled  in  a  current  of  hydrochloric  acid  gas.  If  arsenic 
is  not  desired  it  may  be  expelled  by  reducing  the  solution  with  sodium  meta- 
bisulphite  or  potassium  iodide  and  boiling.  Antimony  and  tin  remain  in  the 
concentrated  acid  solution. 

The  separation  of  arsenic  from  antimony  and  tin  may  be  effected  by  removal 
of  the  former  in  a  strong  hydrochloric  acid  solution  as  described  under  the  section 
"Preparation  and  Solution  of  the  Sample,"  arsenic  being  precipitated  by  hydrogen 
sulphide,  whereas  antimony  and  tin  remain  in  solution. 

Separation  of  Antimony  from  Tin.  Upon  the  removal  of  arsenic,  anti- 
mony may  be  determined  directly  in  the  presence  of  tin  by  one  of  the  volu- 
metric methods  given  later.  If  a  gravimetric  separation  is  desired,  it  may 
be  made  according  to  a  modification  of  Clark's  method,  1  which  depends  upon  the 
fact  that  antimony  is  completely  precipitated  from  a  solution  containing  oxalic 
acid,  by  hydrogen  sulphide,  whereas  tin  is  not.  The  tin  must  be  in  the  stannic 
form,  otherwise  the  insoluble  crystalline  stannous  oxalate  will  form. 

If  the  mixture  is  acid,  it  is  neutralized  with  caustic  and  twenty  times  the 
weight  of  the  Sn  and  Sb  present  added  in  excess,  e.g.,  2  grams  potassium 
hydroxide  in  excess  for  every  0.1  gram  of  tin  and  antimony  present  in  the  solu- 
tion. About  ten  times  as  much  of  tartaric  acid  is  now  added  as  the  maximum 
weight  of  the  two  metals,  followed  by  30%  hydrogen  peroxide  to  oxidize  the 
tin.  The  excess  of  peroxide  is  removed  by  boiling.  To  the  slightly  cooled 
solution  a  hot  solution  of  pure  oxalic  acid  is  added,  5  grams  of  oxalic  acid  for 
each  0.1  gram  of  the  mixed  elements.  C02+02  are  evolved.  The  solution 
is  boiled  for  about  ten  minutes  and  the  volume  made  up  to  about  100  cc. 
Hydrogen  sulphide  is  rapidly  passed  into  the  boiling  solution  until  a  change 
from  a  white  turbidity  to  an  orange  color  takes  place  and  antimony  begins 
to  precipitate.  The  passage  of  the  gas  is  continued  for  fifteen  minutes,  the 
solution  diluted  with  hot  water  to  a  volume  of  250  cc.  and  hydrogen  sulphide 
passed  into  the  boiling  solution  for  another  fifteen  minutes.  The  flame  is  now 
removed  and  the  H2S  "  gasing  "  continued  for  ten  minutes  longer.  The  pre- 
cipitated antimony  pentasulphide  is  filtered  off  in  a  weighed  Gooch  crucible. 
1  The  Original  procedure  may  be  found  in  Chem.  News,  Vol.  XXI,  p.  124. 


ANTIMONY  23 

It  may  be  determined  gravimetrically  as  Sb2S3,  according  to  the  procedure 
given  later,  by  washing  with  1%  oxalic  acid  and  dilute  acetic  acid,  by  decan- 
tation,  the  solutions  being  hot  and  saturated  with  hydrogen  sulphide.  The 
precipitate  washed  into  the  crucible  is  dried  in  a  current  of  C02  at  a  heat  of 
280  to  300°  and  weighed  as  Sb2S3. 

Tin  may  be  determined  electrolytically  in  the  nitrate  evaporated  to  about 
150  cc.,  the  oxalic  acid  being  nearly  neutralized  with  ammonia.  See  Electro- 
lytic Determination  of  Tin. 

Antimony  may  be  separated  from  tin  in  a  hot  hydrochloric  acid  solution 
by  addition  of  pure  iron.  The  iron  and  tin  sulphides  are  dissolved  in  concentrated 
hydrochloric  acid  plus  a  few  crystals  of  potassium  chlorate.  The  solution 
should  contain  about  10%  hydrochloric  acid,  more  hydrochloric  acid  being  added 
as  the  iron  dissolves.  Antimony  is  precipitated  as  a  metal. 


GRAVIMETRIC  METHODS  FOR  THE  DETERMINATION  OF 

ANTIMONY 

The  accuracy  and  rapidity  of  volumetric  methods  for  the  determination 
of  antimony  leave  little  to  be  desired  in  the  estimation  of  this  element,  so  that 
the  more  tedious  gravimetric  methods  are  less  frequently  used.  The  following 
procedures  are  given  in  view  of  possible  utility  in  certain  analyses. 

Determination  of  Antimony  as  the  Trisulphide,  Sb2Ss 1 

Although  hydrogen  sulphide  passed  into  a  cold  solution  tends  to  precip- 
itate Sb2S5,  in  hot  strongly  acid  solutions,  the  lower  sulphide,  Sb2S3,  tends  to 
form.  The  higher  sulphide  is  decomposed  at  230°  C.  with  formation  of  Sb2S3 
and  the  volatilization  of  sulphur.  A  temperature2  of  280  to  300°  is  even  more 
favorable  for  this  transformation.  The  method  takes  advantage  of  these  con- 
ditions for  formation  of  antimony  trisulphide,  in  which  form  it  is  weighed. 

Procedure.  The  solution  of  antimony,  free  from  arsenic,  is  treated  in  an 
Erlenmeyer  flask  with  strong  hydrochloric  acid  until  the  solution  contains  about 
20%  of  the  concentrated  acid.  The  mixture  is  heated  to  boiling  and  a  slow 
current  of  hydrogen  sulphide  is  passed  into  the  hot  solution  until  the  precipitate 
passes  from  a  yellow  color  through  an  orange  and  finally  becomes  a  dark  red 
to  black  color.  The  flask  is  agitated  gently  to  coagulate  the  precipitate,  which 
settles  in  a  crystalline  form.  The  solution  is  diluted  with  an  equal  volume  of 
water,  washing  down  the  walls  of  the  flask.  A  slight  turbidity  is  generally 
seen,  due  to  precipitation  of  a  small  amount  of  antimony  that  remains  in  Solu- 
tion in  a  strong  acid  solution.  H2S  is  now  passed  into  the  diluted  solution 
until  it  becomes  clear,  thirty-five  to  forty  minutes  are  usually  sufficient  to  pre- 
cipitate all  of  the  antimony.  The  precipitate  is  transferred  to  a  weighed  Gooch 
crucible,  washed  with  small  portions  of  water  containing  hydrogen  sulphide, 
and  finally  with  pure  water. 

It  is  a  common  practice,  at  this  juncture,  to  wash  the  precipitate  with  car- 
bon disulphide  or  carbon  tetrachloride  to  remove  precipitated  sulphur.  Alcohol 
is  now  used,  followed  by  ether,  and  the  precipitate  sucked  dry. 

1  Method  of  Vortmann  and  Metzel  modified. 

2  Paul,  Z.  anal.  Chem.  31,  540  (1892). 


24  ANTIMONY 

The  Gooch  crucible  is  placed  in  a  large  combustion  tube  and  heated  in  a 
current  of  dry,  pure  C02  at  130°  C.  for  an  hour.  The  temperature  is  now 
raised  to  280  to  300°  C.  and  the  heating  continued  for  two  hours.  The  residue 
will  consist  of  pure  Sb2S3. 

Sb2S,X0.7l42=Sb,  or  Sb2S3X 0.8568  =Sb203. 

NOTES.  Antimony  may  be  determined  by  oxidation  of  the  sulphide  precipitate 
by  means  of  fuming  nitric  acid.  The  mixture  evaporated  to  dryness  is  ignited  and 
the  residue  weighed  as  Sb2O4.  The  temperature  of  the  ignition  should  be  between 
750  to  800°  C.  The  volatile  trioxide  forms  at  a  little  above  950°.  The  procedure 
requires  greater  care  than  the  sulphide  method  and  possesses  no  advantages. 

Pure  carbon  dioxide  may  be  obtained  from  limestone  placed  in  a  Kipp  generator. 
The  gas  is  dried  by  passing  it  through  strong  sulphuric  acid.  It  should  be  free  from 
oxygen  of  the  air.  It  is  advisable  to  sweep  out  the  air  from  the  generator  before 
attaching  it  to  the  combustion  train.  The  air  in  the  tube  is  swept  out  with  carbon 
dioxide  before  heating  the  sample. 

Property  of  Sb2S3,  m.w.,  336.61;  sp.gr.,  4.65;  fusible  and  volatile;  solubility, 
0.000175  gram  per  100  cc.  H2O;  decomposed  by  hot  H2O;  soluble  in  alkalies,  NH4HS, 
KaS,  cone.  HC1. 

Electrolytic  Determination  of  Antimony  1 

The  chief  condition  for  the  success  of  the  electrolytic  deposition  of  antimony 
in  metallic  form  is  the  absence  of  polysulphides,  since  these  substances  prevent 
the  element  from  being  deposited,  2Sb+3Na2S2=2Na3SbS3.  The  formation 
of  polysulphides  may  be  prevented  during  electrolysis  by  addition  of  potassium 
cyanide  to  the  solution,2  Na2S2+KCN  =Na2S+KCNS. 

The  results  of  this  method,  according  to  F.  Henz,3  are  invariably  1.5  to 
2%  too  high  of  the  total  antimony  present  in  the  solution.  Tread  well  and 
Hall  recommend  subtraction  of  a  constant  factor  of  1.6%  of  the  weight  of  the 
antimony  deposited.  The  sample  for  analysis  should  contain  not  over  0.2  gram 
antimony. 

Procedure.  Antimony  precipitated  as  the  sulphide  is  washed  and  then 
dissolved  off  the  filter  by  pouring  pure  sodium  sulphide  solution  (sp.gr.  1.14) 
over  the  precipitate,  the  solution  being  caught  in  a  weighed  platinum  dish, 
with  unpolished  inner  surface.  The  total  volume  of  the  solution  should  be 
not  over  80  cc.  (if  less  than  this,  additional  Na2S  solution  is  added  to  make 
up  to  80  cc.).  Sixty  cc.  of  water  followed  by  2  to  3  grams  of  potassium  cyanide 
(C.P.)  are  added  and  the  cyanide  dissolved  by  stirring  with  the  rotating  anode. 
The  solution  heated  to  60  to  70°  is  electrolyzed  with  a  current  of  1  to  1.5  amperes, 
E.M.F.  =2  to  3  volts.  Two  hours  are  generally  sufficient  to  deposit  all  the 
antimony.  The  light-gray  deposit  adheres  firmly  upon  the  cathode.  With- 
out breaking  the  current  the  solution  is  siphoned  off,  while  fresh  water  is 
being  added,  until  the  current  ceases  to  flow  through  the  liquid.  The  cathode 
is  washed  thoroughly  with  water,  followed  by  alcohol  and  ether  and  then  dried 
at  about  80°,  cooled  in  a  desiccator  and  weighed. 

The  antimony  deposits  may  be  removed  by  heating  with  a  solution  of  alkali 

1  Method  first  proposed  by  Parrodi  and  Mascazzini,  Z.  anal.  Chem.,  18,  587 
(1879),  modified  by  Luckow,  Z.  anal.  Chem.,  19,  13  (1880),  and  later  improved 
by  Classen  and  Reiss,  Berichte,  14,  1629  (1881);  17,  2474  (1884);  18,  408  (1885); 
27,  2074  (1894).  2Treadwell  and  Hall,  Analytical  Chemistry.  »Z.  anorg.  Chem., 
37,  31  (1903). 


ANTIMONY  25 

polysulphide^or  by  a  mixture  of  equal  parts  of  saturated  solution  of  tartaric 
acid  and  nitric  acid. 

VOLUMETRIC   METHODS 
Potassium  Bromate  Method  for  Determining  Antimony1 

Outline.  This  method  is  of  special  value  in  determining  antimony  in  hard 
lead  and  alloys.  It  was  first  suggested  by  Gyory  and  later  modified  by  Siedler, 
Nissensen  and  Rowell.2  The  process  is  based  upon  the  oxidation  of  antimony 
from  the  trivalent  to  the  pentavalent  form  by  potassium  bromate,  the  follow- 
ing reaction  taking  place: 

KBr03+3SbCl3+6HCl  =  3SbCl5+KBr+3H20. 

Standard  Solutions. 

Antimony  Chloride  Solution.  Six  grams  of  the  C.  P.  pulverized  metal  are 
dissolved  in  500  cc.  of  concentrated  hydrochloric  acid  together  with  100  cc. 
saturated  bromine  solution,  more  acid  and  bromine  added  if  necessary  to  effect 
solution.  After  expelling  the  bromine  by  boiling,  about  200  cc.  concentrated 
hydrochloric  acid  are  added  and  the  whole  made  up  to  one  liter.  Fifty  cc. 
=0.3  gram  antimony. 

N/10  Potassium  Bromate  Solution.  2.82  grams  of  C.  P.  salt  are  dissolved 
in  water  and  made  up  to  1  liter.  Theoretically  2.7852  grams  are  required,  but 
the  salt  invariably  contains  potassium  bromide  as  an  impurity.  The  solution 
is  standardized  against  50  cc.  of  the  antimony  chloride  solution,  which  has 
been  reduced  with  sodium  sulphite  according  to  the  standard  scheme.  One 
cc.  of  N/10  KBr03  =0.006  gram  Sb. 

Methyl  Orange.  0.1  gram  M.  0.  per  100  cc.  of  distilled  water.  The  indi- 
cator should  be  free  from  sediment. 

Saturated  Bromine  Solution.  500  cc.  concentrated  hydrochloric  acid  satu- 
rated with  70  cc.  of  bromine. 

Procedure.  Solution.  One  gram  of  the  finely  divided  alloy  is  brushed 
into  a  500-cc.  beaker,  100  cc.  of  concentrated  hydrochloric  acid  and  20  cc.  of 
saturated  bromine  solution  are  added.  The  beaker  is  covered  and  placed  on 
the  steam  bath  until  the  metal  dissolves.  It  may  be  necessary  to  add  more 
bromine  and  acid  to  effect  complete  solution.  In  case  the  oxides  of  antimony 
and  tin  separate  out  and  do  not  redissolve,  fusion  with  sodium  hydroxide  may 
be  necessary.  Bromine  is  now  expelled  by  boiling  the  solution  down  to  about 
40  cc. 

Reduction.  One  hundred  cc.  of  concentrated  hydrochloric  acid  and  10  cc. 
of  a  fresh  saturated  solution  of  Na2S03  are  added  and  the  solution  boiled  down 
to  40  cc.,  on  a  sand  bath,  to  expel  arsenic  and  the  excess  of  normal  sodium  sul- 
phite. Samples  high  in  arsenic  may  require  a  repetition  of  the  reduction. 

Titration.  The  cover  and  sides  of  the  beaker  are  rinsed  down  with  20  cc. 
of  hydrochloric  acid  (sp.gr.  1.2)  followed  by  a  few  cc.  of  hot  water  and  the 
solution  heated  to  boiling  on  a  sand  bath.  The  standard  (bromate  solution 
is  now  run  into  the  hot  solution  of  antimony  to  within  2  to  3  cc.  of  the  end- 

1S.  Gyory,  Zeit.  Anal.  Chem.,  32,  415  (1893).  J.  B.  Duncan,  Chem.  News,  95, 
49  (1907). 

2  H.  W.  Rowell,  Jour.  Soc.  Chem.  Ind.,  XXV,  1181. 


26  ANTIMONY 

point,  this  having  been  determined  in  a  preliminary  run  with  methyl  orange 
added  in  the  beginning,  4  drops  of  methyl  orange  are  added  and  the  titration 
completed  cautiously  until  the  color  of  the  indicator  is  destroyed.  If  iron 
or  copper  is  present  the  final  product  will  appear  yellow.  Since  the  end-reaction 
is  slow  the  last  portion  of  the  reagent  should  be  added  drop  by  drop  with  con- 
stant stirring. 

1  cc.  N/10  KBrOa  =0.006  gram  Sb. 

NOTES.  Since  antimony  chloride  begins  to  volatilize  at  195°  C.  and  boils  at  220°  C. 
it  is  advisable  not  to  carry  the  concentration  too  far  while  expelling  arsenic. 

Lead,  copper,  zinc,  tin,  silver,  chromium,  and  sulphuric  acid  have  no  effect  upon 
the  determination,  but  large  quantities  of  calcium,  magnesium,  and  ammonium 
salts  tend  to  make  the  results  high.  Low1  found  that  copper  produced  high  results, 
approximately  .012%  too  high  for  every  0.1%  of  copper  present.  The  author  (W.W.S.) 
finds,  however,  that  with  the  procedure  given  above,  amounts  of  copper  as  high  as 
15%  produced  no  difficulty  beyond  a  yellow  coloration  of  the  solution.  With  larger 
amounts  of  copper,  the  end-point  became  difficult  to  detect  owing  to  the  depth  of 
this  yellow  color,  so  that  in  case  of  brass  and  copper  alloys,  the  method  must  be 
modified  by  a  procedure  for  removal  of  the  copper.  Lead  up  to  95%  caused  no 
difficulty.  Iron,  in  amounts  such  as  are  commonly  met  in  alloys  of  lead,  does  not 
interfere. 

During  the  course  of  analysis  antimony  may  be  isolated  as  the  sulphide;  this  is 
dissolved  in  strong  hydrochloric  acid,  and  reduced  and  concentrated  to  expel  arsenic 
that  may  be  present  as  a  contamination,  and  the  resulting  solution  titrated  with 
potassium  bromate  as  directed  above. 

Sources  of  Error,  (a)  Imperfect  volatilization  of  arsenic.  (6)  Incomplete  expul- 
sion of  SO2.  (c)  Over-titration  if  insufficient  hydrochloric  acid  is  present. 

No  loss  of  antimony  occurs  at  temperatures  below  120°  C. 

Potassium  Iodide  Method  for  Determining  Antimony 

Procedure.  To  1  gram  of  fine  sawings  or  filings  in  a  16-oz.  Erlenmeyer  flask 
add  60  cc.  of  concentrated  hydrochloric  acid  and  heat  on  an  asbestos  board  or  on 
the  water  bath  just  below  boiling.  When  hydrogen  is  no  longer  evolved,  decant 
the  liquor  and  wash  twice  with  concentrated  hydrochloric  acid,  retaining  the 
antimony  in  the  flask.  Now  dissolve  the  antimony  by  adding  15  cc.  of  con- 
centrated hydrochloric  acid  and  solid  potassium  chlorate,  a  few  crystals  at  a  time, 
until  the  antimony  is  in  solution,  the  liquid  being  kept  hot.  Expel  chlorine 
by  boiling,  add  50  cc.  of  concentrated  hydrochloric  acid  and  again  bring 
to  boiling.  Cool  and  add  20  cc.  of  20%  potassium  iodide  solution  and  1  cc.  of 
carbon  disulphide  or  tetrachloride.  Titrate  the  liberated  iodine  with  tenth-normal 
sodium  thiosulphate.  The  brown  color  will  gradually  disappear  from  the  solu- 
tion and  the  last  traces  of  free  iodine  will  be  collected  in  carbon  disulphide  or 
carbon  tetrachloride,  giving  a  pink  color.  When  this  pink  color  disappears  the 
end-point  has  been  reached. 

One  cc.  N/10  Na2S203  =  .006  gram  of  Sb. 

Na2S203  is  standardized  against  .3  gram  antimony  as  in  case  of  Potassium 
Bromate  Method,  the  above  procedure,  however,  being  followed.  Antimony 
must  be  free  from  copper  and  arsenic. 

NOTES.  The  following  reversible  reaction  is  of  interest:  "R"  representing  a  tri- 
valent  metal  with  oxidation  to  pentavalent  form. 

R2O,+2I2+2H2O  =  RjO6+4HI. 

The  reaction  goes  to  the  right  when  an  alkali  is  present  to  neutralize  the  free 
acid  formed;]  e.g.,  Mojhr's  process  for  determining  arsenic  by  titration  of  the  lower 
1  A.  H.  Low,  "Technical  Methods  of  Ore  Analysis." 


ANTIMONY  27 

oxide  with  iodine  in  presence  of  sodium  bicarbonate.  The  reaction  goes  to  the  left 
in  presence  of  strong  acid;  e.g.,  Weller's  process  for  the  determination  of  antimony 
in  an  acid  solution. 

The  solution  should  not  contain  more  than  i  of  its  volume  of  hydrochloric  acid 
(sp.gr.  1.16),  since  too  much  hydrochloric  acid  gives  high  results,  owing  to  the  action 
of  hydrochloric  acid  on  potassium  iodide.  Too  little  acid  leads  to  the  separation 
of  basic  iodides  and  chlorides  of  antimony.  The  solution  is  best  boiled  down  to 
20%  hydrochloric  acid  (above  strength). 

Stannous  chloride  may  be  used  in  place  of  thio-sulphate  in  titration  of  iodine. 


SbCl5+2KI  =  SbCl3+2KCl+I2     and     I2+SnCl2+2HCl  = 
Determination  of  Antimony  by  Oxidation  with  Iodine 

The  procedure  originated  by  Mohr  and  modified  by  Clark,  depends  upon 
the  reaction  Sb203+2I2+2H20  =Sb2p5+4HI. 

The  reaction  takes  place  when  iodine  is  added  to  a  solution  of  antimonous 
salt  in  presence  of  an  excess  of  alkali  bicarbonate.  In  an  acid  solution  oxida- 
tion with  iodine  does  not  go  beyond  Sb203. 

Procedure.  Solution.  The  sample  is  brought  into  solution  by  one  of  the 
procedures  given  under  ''Preparation  and  Solution  of  the  Sample."  Alloys 
of  antimony,  lead,  and  tin  are  treated  according  to  directions  given  for  this 
combination. 

Titration.  To  the  hydrochloric  acid  solution  of  antimony  is  added  tar- 
taric  acid  or  Rochelle  salts,  the  excess  of  the  acid  neutralized  with  sodium  car- 
bonate, the  solution  made  barely  acid  with  hydrochloric  acid  and  a  saturated 
solution  of  sodium  bicarbonate  added  in  the  proportion  of  10  cc.  bicarbonate 
solution  for  each  0.1  gram  of  Sb203.  Starch  is  added  as  an  indicator  and  the 
solution  titrated  with  N/10  iodine. 

1  cc.  N/10  iodine  =0.006  gram  Sb. 

NOTE.     The  titration  should  be  made  immediately  upon  addition  of  the  sodium 

salts. 

Antimony  in  Solder  Metal  and  Alloys  with  Tin  and  Lead  1 

Procedure.  Dissolve  2  grams  of  the  sample  of  alloy  in  concentrated  hy- 
drochloric acid.  When  the  metal  is  all  in  solution,  add  crystals  of  iodine  until 
the  solution  is  thoroughly  permeated.  The  color  at  this  point  should  be  a 
deep  purple.  Boil  until  all  of  the  iodine  fumes  have  been  driven  out.  The 
metallic  antimony  which  did  not  go  into  solution  in  the  hydrochloric  acid  should 
now  be  all  dissolved.  If  it  is  not,  add  more  iodine  until  the  solution  is  com- 
plete. When  all  is  in  solution  and  the  color  changes  to  a  straw  yellow,  cool,  add 
a  few  cc.  of  starch  solution.  If  a  blue  color  appears,  due  to  an  excess  of  iodine, 
run  in  N/10  sodium  thiosulphate  solution  until  colorless.  In  case  there  is  no 
blue  color  developed,  add  N/10  iodine  until  a  faint  blue  appears.  Now  add 
50  cc.  of  a  saturated  solution  of  Rochelle  salts.  Make  alkaline  to  litmus  by 
adding  25%  sodium  hydrate  solution.  Then  make  slightly  acid  with  HC1 
and  finally  alkaline  with  sodium  bicarbonate.  Cool  and  titrate  with  N/10 
iodine. 

NOTE.  "The  method  gives  very  good  results.  I  have  checked  it  up  when  there 
was  one-tenth  of  a  gram  known  antimony  present  and  the  results  were  within  a 
reasonable  limit  of  accuracy."  [ 

1  Method  communicated  to  author  by  Mr.  B.  S.  Clark. 


28  ANTIMONY 

Other  Procedures 
Permanganate  Method 

Antimonous  salts  may  be  titrated  with  standard  potassium  permanganate. 
The  iron  value  for  the  permanganate  multiplied  by  1.075  or  the  oxalic  acid 
(C2H2(V2H20)  value  multiplied  by  0.9532,  will  give  the  antimony  value.1 

Indirect  Evolution  Method 

The  method  depends  upon  the  evolution  of  H2S  from  the  sulphides  of  anti- 
mony decomposed  by  strong  hydrochloric  acid,  the  amount  of  hydrogen  sul- 
phide being  the  same  for  either  Sb2S3  or  Sb2S5,  the  following  reactions  taking 
place: 

1.  Sb2S3+6HCl  =  2SbCl3+3H2S. 

2.  Sb2S6+6HCl=2SbCl3+S2+3H2S. 

The  details  of  the  method  are  practically  the  same  as  determination  of 
sulphur  by  the  evolution  method  in  the  analysis  of  iron  and  steel.  See  Chapter 
on  Sulphur.  The  antimony  sulphide  precipitate  is  placed  in  the  evolution 
flask,  strong  hydrochloric  acid  added  with  an  equal  volume  of  water  and  the 
evolved  hydrogen  sulphide  absorbed  in  an  ammoniacal  solution  of  cadmium 
chloride.  The  precipitated  cadmium  sulphide  is  then  titrated  with  iodine  in 
an  acid  solution. 

One  cc.  N/10  1=0.001604  gram  S,  since  3S=2Sb,  therefore  Sb  =8X2.499, 
hence,  1  cc.  N/10  1=0.00401  gram  Sb. 

Preparation  of  Standard  Iodine  Solution.  An  approximate  tenth  normal  solu- 
tion is  made  by  dissolving  12.7  grams  of  commercial  iodine,  roughly  weighed  on 
a  watch-glass,  in  200  cc.  of  water  containing  about  25  grams  of  potassium  iodide, 
solution  being  effected  in  a  graduated  liter  flask.  After  making  up  to  1000  cc. 
with  distilled  water,  the  reagent  is  transferred  to  a  dark-colored  bottle,  to  protect 
it  from  light.  It  is  advisable  to  make  up  5  to  10  liters  at  a  time  for  laboratories 
where  the  solution  is  in  constant  demand.  After  standing  several  hours,  the 
reagent  is  standardized  by  running  a  portion  from  a  burette  into  100  cc.  of  tenth 
normal  arsenous  acid  (see  page  204)  until  a  faint  yellow  color  is  perceptible.  In 
presence  of  starch  indicator  a  faint  blue  color  is  obtained. 

100  divided  by  the  cc.  of  iodine  required  gives  the  factor  for  a  N/10  solution. 

Example.  If  98.5  cc.  of  iodine  are  required,  100-^98.5  =  1.0152  N/10  or 
.10152  normal. 

Tenth  normal  arsenous  acid  solution  contains  4.953  grams  of  As2O3,  per  liter,  dis- 
solved in  sodium  hydroxide  and  made  up  according  to  directions  given  on  page  204. 
The  oxide  is  seldom  pure,  so  that  allowance  must  be  made  for  impurities.  For  example, 
the  acid  containing  99.56  per  cent  As2O3  would  require  4.953  -5-. 9956  =  4.97  grams  per 
liter  of  solution. 

Commercial  iodine  may  contain  chlorine,  bromine,  cyanogen  and  water.  It  may  be 
purified  by  repeated  sublimation  ("  Analytical  Chemistry,"  Treadwell  and  Hall,  IV 
Ed.,  page  646,  or  "A  Treatise  on  Quantitative  Inorganic  Analysis"  (1913),  by  J.  W. 
Mellor,  page  288).  There  is  no  advantage  in  taking  the  theoretical  amount  of  purified 
iodine,  however,  since  the  reagent  changes  in  strength  on  standing. 

Potassium  iodide  augments  solution  of  iodine,  which  is  sparingly  soluble  in  water. 

The  iodine  may  be  standardized  by  titrating  a  definite  volume  with  N/10  sodium 
thiosulphate.  See  page  204. 

1  Technical  Methods  of  Ore  Analysis,  by  A.  H.  Low. 


ANTIMONY  29 

Determination  of  Small  Amounts  of  Antimony1 

The  determination  depends  upon  the  fact  that  when  antimony  compounds 
are  acted  upon  in  acid  solution  by  nascent  hydrogen  the  gas  stibine  is  evolved, 
which  forms  a  black  compound  with  silver  nitrate.  The  method  is  very  similar 
to  Allen,  and  Palmer's  modification  of  the  Gutzeit  procedure  for  arsenic,  dif- 
fering, however,  in  the  facts  that  heating  is  necessary  to  evolve  completely 
the  stibine,  the  presence  of  iron  is  not  required,  and  stannous  chloride  is  not 
used. 

Procedure.  The  material  is  brought  into  solution  with  water,  or  by  treat- 
ment with  hydrochloric  acid,  or  hydrochloric  acid  and  an  oxidizing  agent  (KC103  or 
Br)  with  subsequent  evaporation  to  dryness  on  the  steam  plate  or  water  bath,  or 
by  fusion  with  sodium  carbonate  followed  by  acid  extraction.  If  arsenic  is  present, 
the  solution,  contained  in  a  distillation  flask,  is  reduced  with  ferrous  sulphate  or 
chloride  and  arsenic  distilled  off  in  a  current  of  HC1  gas,  according  to  the  proced- 
ure outlined  under  Arsenic.  The  volume  of  the  solution  is  reduced  from 
about  200  cc.  to  50-60  cc.2  Antimony  is  now  isolated  by  continuing  the  distilla- 
tion with  addition  of  zinc  chloride  to  raise  the  boiling-point  of  the  solution. 
Thirty  cc.  of  a  saturated  solution  of  zinc  chloride  are  added  to  the  liquor  in  the 
flask  and  antimony  distilled,  hydrochloric  acid  (sp.gr.  1.2)  being  added  through 
a  separatory  funnel,  drop  by  drop,  to  replace  the  solution  evaporated.  The  first 
fifty  cc.  of  the  distillate  will  contain  all  the  antimony,  present  in  small  amount. 
The  excess  of  acid  is  carefully  neutralized  with  sodium  carbonate,  leaving  the 
solution  slightly  acid.  The  mixture  is  placed  in  the  modified  Gutzeit  apparatus, 
pure  zinc  shot  added,  and  the  apparatus  connected  up  as  described  for  deter- 
mining traces  of  arsenic,  Fig.  2.  In  place  of  the  mercuric  chloride,  silver 
nitrate  paper  is  used  for  obtaining  the  stain,  as  this  reagent  is  more  sensi- 
tive to  stibine.  The  apparatus  is  placed  in  warm  water  (about  60°  C.)  for 
two  hours.  The  silver  nitrate  paper  is  then  removed,  immersed  in  10%  solu- 
tion of  sodium  thiosulphate  to  fix  the  stain  and  washed  with  distilled  water 
to  remove  the  silver  nitrate.  The  paper  is  then  dried  and  compared  with  a 
standard  set  of  stains  made  by  placing  known  amounts  of  antimony  in  solu- 
tions of  like  material  examined,  and  proceeding  according  to  the  outline  given. 

NOTES.  Potassium  antimonyl  tartrate  may  be  taken  for  the  standard  antimony 
solution.  0.2765  gram  of  the  salt  is  diluted  to  a  liter  and  10  cc.  of  this  stock  solution  is 
diluted  to  1  liter.  10  cc.  of  this  final  solution  is  equivalent  to  0.01  milligram  of  anti- 
mony. Stains  representing  0.005  to  0.05  milligram  antimony  are  suited  for  the  test. 

Silver  nitrate  paper.  This  is  made  by  dipping  sheets  of  filter  paper  in  a  0.4% 
solution  of  silver  nitrate,  running  through  the  mangle  to  remove  the  excess  of  silver 
nitrate,  drying  and  cutting  into  strips  according  to  the  procedure  recommended  for 
the  paper  used  in  the  Gutzeit  method  for  arsenic. 

Blank  runs  should  be  made  with  the  reagents  and  the  blanks  deducted  from  the 
stains  obtained  in  the  regular  tests.  If  possible,  arsenic  and  antimony-free  reagents 
should  be  used. 

The  author  is  indebted  to  Mr.  J.  P.  Kelly  for  his  review  and  criticism  of  this  chapter. 

1  Method  suggested  by  C.  R.  Sanger,  communicated  to  the  author  by  Mr.  J.  P.  Kelly. 

2  During  the  removal  of  arsenic  the  temperature  of  the  solution  should  not  rise 
above  125°  C.,  since  a  loss  of  antimony  occurs  above  this  point.   It  is  advisable?  there- 
fore, to  place  a  thermometer  in  the  flask,  and  observe  the  temperature  during  the 
distillation. 


ARSENIC 

WILFRED  W.  SCOTT 


m.P. 


Oxides,  As2O3, 

DETECTION 

Hydrogen  sulphide  precipitates  the  yellow  sulphide  of  arsenic,  As2S3,  when 
passed  into  its  solution  made  strongly  acid  with  hydrochloric  acid.  If  the 
solution  contains  more  than  25%  hydrochloric  acid,  (sp.gr.  1.126)  the  other 
members  of  the  hydrogen  sulphide  group  do  not  interfere,  as  they  are  not 
precipitated  from  strong  acid  solutions  by  hydrogen  sulphide.  Arsenic  sulphide 
is  soluble  in  alkaline  carbonates.  (Antimony  sulphide,  Sb2S3,  reddish  yellow, 
is  insoluble  in  alkaline  carbonates.) 

Volatility  of  the  chloride,  AsCl3,  is  a  means  of  separation  and  distinction 
of  arsenic.  Details  of  the  procedure  are  given  under  "Separations."  The 
distillate  may  be  tested  for  arsenic  as  directed  above. 

Traces  of  arsenic  may  be  detected  by  either  the  Gutzeit  or  Marsh  test 
for  arsenic.  Directions  for  the  Gutzeit  test  are  given  at  the  close  of  the  vol- 
umetric procedures. 

Distinction  between  Arsenates  and  Arsenites.  Magnesia-  mixture  pre- 
cipitates white,  MgNH4As04,  when  added  to  ammoniacal  solutions  containing 
arsenates,  but  it  produces  no  precipitate  with  arsenites. 

Red  silver  arsenate  and  yellow  silver  arsenite  are  precipitated  from  neutral 
solutions  by  ammoniacal  silver  nitrate.  An  arsenate  gives  a  yellow  precipitate 
with  ammonium  molybdate  solution. 

ESTIMATION 

The  determination  of  arsenic  is  required  in  the  valuation  of  native  arsenic, 
white  arsenic,  As.03;  ores  of  arsenic—  orpiment,  As2S3;  realgar,  As2S2;  pyrar- 
gyrite,  As3Sb3;  arsenopyrite,  or  mispickel,  FeSAs;  cobaltite  or  cobalt  glance, 
C.oSAs;  smaltite,  CoAs2;  niccolite.  NiAs.  The  substance  is  estimated  in 
copper  ores,  in  speiss,  regulus;  in  iron  precipitates  (basic  arsenate).  It  is 
determined  in  paint  pigments,  Scheel's  green,  etc.  The  element  is  determined 
in  shot  alloy  and  in  many  metals.  It  is  estimated  in  germicides,  disinfectants, 
and  insecticides  —  Paris  green,  lead  arsenate,  zinc  arsenite.  Traces  are  looked 
for  in  food  products  and  in  substances  where  its  presence  is  not  desired. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  arsenic  compounds  it  will  be  recalled  that  the  oxide,  As203, 

is  not  readily   acted  upon  by   dilute  acids  —  hydrochloric  or  sulphuric.    The 

compound  is  soluble,  however,  in  alkaline  hydroxides  and  carbonates.     Nitric 

*Van  Nostrand's  Chem.  Annual—  Olsen—  3d  Ed. 

30 


ARSENIC  31 

acid  oxidizes  As203  to  the  higher  oxide,  As205,  which  is  soluble  in  water.  The 
sulphides  As2S3  and  As2S6  are  practically  insoluble  in  hydrochloric  or  sulphuric 
acids,  but  are  dissolved  by  the  fixed  alkalies  and  alkali  sulphides.  All  arsenites, 
with  the  exception  of  the  alkali  arsenites,  require  acids  to  effect  solution. 

Pyrites  Ore  and  Arseno-pyrites.  The  amount  of  the  sample  may  vary 
from  1  to  20  grams,1  according  to  the  arsenic  content.  The  finely  ground  sample 
in  a  large  casserole  is  oxidized  by  adding  10  to  50  cc.  of  bromine  solution  (75 
cc.  KBr+50  cc.  liquid  Br+450  cc.  H20)  covering  and  allowing  to  stand  for 
fifteen  minutes,  then  20  to  50  cc.  of  strong  nitric  acid  are  added  in  three  or 
four  portions,  allowing  the  action  to  subside  upon  each  addition.  The  glass 
cover  is  raised  by  means  of  riders,  and  the  sample  evaporated  to  dryness  on 
the  steam  bath;  10  to  25  cc.  of  hydrochloric  acid  are  now  added  and  the  sample 
again  taken  to  dryness.  Again  10  to  25  cc.  of  hydrochloric  acid  are  added 
and  the  sample  taken  to  dryness.  Finally  25  cc.  of  hydrochloric  acid  and  75 
cc.  of  water  are  added,  and  the  mixture  digested  over  a  low  flame  until  all  the 
gangue,  except  the  silica,  is  dissolved.  The  solution  is  now  examined  for  arsenic 
by  distillation  of  the  arsenic  after  reduction,  the  distillate  being  titrated  with 
standard  iodine  solution  according  to  directions  given  later. 

Arsenous  Oxide.  The  sample  may  be  dissolved  in  caustic  soda,  the  solution 
neutralized  with  hydrochloric  acid,  and  the  resulting  sample  titrated  with  iodine. 

Arsenic  Acid,  Alkali  Arsenates,  etc.  The  sample  is  dissolved  in  20  to  25 
cc.  of  dilute  sulphuric  acid,  1  :  1,  in  an  Erlenmeyer  flask,  and  reduced  by 
addition  of  3  to  5  grams  of  potassium  iodide,  the  action  being  hastened  by  placing 
the  mixture  on  a  steam  bath.  The  iodine  liberated  is  exactly  neutralized  with 
thiosulphate  and  the  arsenous  acid  titrated  with  iodine  according  to  the  pro- 
cedure given  later.  If  a  N/10  iodine  solution  is  to  be  used,  the  sample  should 
not  contain  over  .37  gram  arsenic.  A  10-gram  sample  may  be  taken,  made 
up  to  a  definite  volume  and  aliquot  parts  taken  for  analysis. 

Arsenic  in  Sulphuric  Acid.  Arsenous  acid  may  be  titrated  directly  with 
iodine  in  a  20-  to  50-gram  sample,  which  has  been  diluted  to  200  to  300  cc. 
with  water  and  nearly  neutralized  with  ammonium  hydroxide  and  then  an  excess 
of  sodium  acid  carbonate  added,  followed  by  the  iodine  titration.2 

Arsenic  Acid  in  Sulphuric  Acid.  Twenty-five  cc.  of  the  acid  containing 
about  0.1%  arsenic  or  a  larger  volume  in  case  the  percentage  of  arsenic  is  less 
than  0.1%  As203  (the  sp.gr.  of  the  acid  being  known)  are  measured  out  into  a 
short-necked  Kjeldahl  flask.  About  half  a  gram  of  tartaric  acid  and  2  grams  of 
fused,  arsenic-free  potassium  bisulphate  are  added  and  the  acid  heated  over 
a  low  flame  until  the  liberated  carbon  is  completely  oxidized  and  the  acid  again 
becomes  clear,  e.g.,  a  pale  straw  color.  It  is  not  advisable  to  heat  to  violent 
fuming,  as  a  loss  of  arsenic  is  then  apt  to  occur.  The  cooled  acid  is  poured 
into  about  300  cc.  of  water,  the  excess  acid  nearly  neutralized  with  ammonia, 
bicarbonate  of  soda  added  in  excess  and  the  arsenous  acid  titrated  with  standard 
iodine.  Total  arsenic  as  As203  minus  arsenous  arsenic  as  As203=  arsenic  arsenic 
in  terms  of  As203.  This  result  multiplied  by  1.1616  =As206. 

Arsenic  in  Hydrochloric  Acid.  The  arsenic  in  20  to  100  cc.  sample  is 
reduced  by  ferrous  chloride,  the  arsenic  distilled  according  to  directions  given 
later,  and  the  distillate  titrated  with  iodine. 

1  0.1%  arsenic  determined  on  a  20-gram  sample. 

2  SO2  should  be  expelled  by  heat  or  by  a  current  of  air  before  treating  with  the 
alkali. 


32  ARSENIC 

Arsenic  in  Organic  Matter.1  0.2  to  0.5  gram  of  the  sample  finely  powdered 
is  oxidized  by  mixing  with  10  to  15  grams  of  sodium  carbonate  and  sodium 
peroxide,  1  :  1,  in  a  nickel  crucible,  a  portion  of  the  fusion  mixture  being  spread 
over  the  charge.  After  heating  gently  for  fifteen  minutes,  the  fusion  is  com- 
pleted by  heating  to  dull  redness  for  five  minutes  longer.  The  contents  of 
the  crucible  are  rinsed  into  an  Erlenmeyer  flask  after  extraction  with  water, 
and  the  solution  made  acid  with  dilute  sulphuric  acid,  1:1.  The  mixture 
is  boiled  down  to  100  cc.,  1  to  2  grams  of  potassium  iodide  added  and  the  solu- 
tion further  concentrated  to  about  40  cc.  Iodine  is  reduced  with  sulphurous 
acid  or  thiosulphate,  the  solution  diluted  with  hot  water  and  saturated  with 
hydrogen  sulphide.  Arsenous  sulphide  is  filtered  off,  washed,  dissolved  in  15 
to  20  cc.  of  half -normal  sodium  hydroxide  and  30  cc.  of  hydrogen  peroxide  (30%) 
solution  added,  and  the  solution  boiled.  About  12  cc.  of  dilute  sulphuric  acid, 
1  :  1,  are  added,  together  with  1  to  2  grams  of  potassium  iodide,  the  solution 
concentrated  to  40  cc.  and  free  iodione  reduced  with  thiosulphate  as  before. 
Arsenic  is  now  titrated,  with  standard  iodine,  upon  neutralization  of  the  free  acid 
with  sodium  hydroxide  and  sodium  acid  carbonate. 

Lead  Arsenate.  Ten  grams  of  the  thoroughly  mixed  paste  or  5  grams  of 
the  powder  are  dissolved  by  treating  with  25  cc.  of  10%  hot  sodium  hydrox- 
ide solution,  and  diluted  to  250  cc.  An  aliquot  part,  50  cc.  (=2  grams  paste 
and  1  gram  powder)  is  placed  in  an  Erlenmeyer  flask  and  20  cc.  of  dilute 
sulphuric  acid,  1:1,  added,  and  the  solution  diluted  to  150  cc.  About  3  grams 
of  solid  potassium  iodide  are  added  and  the  solution  boiled  down  to  about 
50  cc.  (but  not  to  fumes).  The  liquor  will  be  colored  yellow  by  free  iodine. 
Tenth  normal  sodium  thiosulphate  is  added  drop  by  drop  until  the  free  iodine 
is  neutralized  (solution  loses  its  yellow  color),  it  is  now  diluted  to  about  250 
cc.  and  the  free  acid  neutralized  by  ammonium  hydroxide  (methyl  orange 
indicator),  then  made  slightly  acid  with  dilute  sulphuric  acid,  and  an  excess 
of  bicarbonate  of  soda  added.  The  arsenic  is  titrated  with  standard  iodine. 

The  arsenic  may  be  reduced  by  placing  the  50-cc.  sample  in  a  Kjeldahl 
flask,  adding  25  cc.  of  strong  sulphuric  acid  (1.84  sp.gr.),  £  gram  tartaric  acid 
and  2  grams  acid  potassium  sulphate,  KHS04,  and  digesting  over  a  strong  flame 
until  the  organic  matter  is  destroyed  and  the  solution  is  a  pale  yellow  color. 
The  cooled  acid  is  diluted  and  neutralized,  etc.,  as  directed  above. 

Water-soluble  Arsenic  in  Insecticides.  Rapid  Works  Test.  Two  grams 
of  the  paste  is  digested  with  1000  cc.  of  water  at  90°  C.  for  five  minutes,  in 
a  graduated  1000-cc.  flask.  An  aliquot  portion  is  filtered  and  the  arsenic 
determined  by  the  Gutzeit  method. 

Water-soluble  arsenite  may  be  titrated  directly  with  iodine  in  presence 
of  sodium  bicarbonate. 

Zinc  Arsenite.  About  5  grams  of  powder  or  10  grams  of  paste  are  taken 
and  dissolved  in  a  warm  solution  containing  300  cc.  of  water  and  25  cc.  of 
strong  hydrochloric  acid.  The  cooled  solution  is  diluted  to  500  cc.  and  100-cc. 
portions  taken  for  analysis.  The  acid  is  partly  neutralized  with  ammonium 
hydroxide  and  50  cc.  of  a  saturated  solution  of  ammonium  oxalate  added 
(to  prevent  precipitation  of  the  zinc  as  ZnC08),  and  an  excess  of  sodium 
bicarbonate,  NaHC03.  Arsenic  is  now  titrated  with  iodine  as  directed  later. 

Soluble  Arsenic  in  Zinc  Arsenite.     One  gram  sample  is  rubbed  into  an 

1  Little,  Cahan,  and  Morgan,  Jour.  Chera.  Soc.,  95,  1477  (1909). 


ARSENIC  33 

» 

emulsion  with  several  portions  of  water  until  the  whole  is  in  suspension.  The 
cloudy  liquor  is  diluted  to  1000  cc.  and  a  portion  filtered  through  a  ^-in. 
asbestos  mat  on  a  perforated  plate,  the  asbestos  being  covered  with  a  layer 
of  filter  paper.  The  first  50  cc.  are  rejected.  One  hundred  cc.  of  the  clear 
filtrate  (=0.1  gram)  is  treated  with  10  cc.  of  strong  sulphuric  acid,  0.05  gram, 
FeaOs  (use  ferric  ammonium  sulphate)  and  |  cc.  of  80%  stannous  chloride  solution 
and  heated  until  colorless.  Arsenic  is  now  determined  by  the  Gutzeit  method, 
using  the  larger-sized  apparatus. 

Arsenic  in  Mispickel.  One  gram  of  the  finely  powdered  mineral  is  fused 
in  a  nickel  crucible  with  about  10  grams  of  a  mixture  of  potassium  carbonate 
and  nitric  acid,  1  :  I,1  and  the  melt  extracted  with  hot  water.  Two  hundred  cc. 
of  a  saturated  solution  of  S02  is  added  to  the  filtrate  to  reduce  the  arsenic, 
the  excess  of  S02  then  expelled  by  boiling,  the  solution  diluted  with  dilute 
sulphuric  acid,  and  arsenic  determined  in  the  filtrate. 

Arsenic  in  Steel,  Iron,  Pig  Iron,  etc.  One  to  50  grams  of  steel,  etc.,  may 
be  treated  according  to  the  scheme  for  pyrites.  If  a  large  sample  is  taken, 
it  is  advisable  to  treat  it  in  a  500-cc.  flask,  connected  with  a  second  flask 
containing  bromine,  to  guard  against  loss  of  arsenic  by  volatilization.  When 
the  sample  has  dissolved  it  is  taken  to  dryness  (the  bromine  in  the  second  flask 
being  combined  with  it)  and  treated  as  directed  in  pyrites.  Arsenic  chloride, 
AsCl5,  is  transferred  to  the  distilling  flask  with  strong  hydrochloric  acid,  and 
arsenic  separated  from  the  iron  by  volatilization  of  reduced  chloride  accord- 
ing  to  the  procedure  given  below. 

Arsenic  in  Copper.  Arsenic  is  precipitated  with  iron  by  the  basic  acetate 
method,  and  thus  freed  from  copper.  Details  of  procedure  are  given  under  the 
determination  of  impurities  in  copper  in  the  chapter  on  the  subject. 

SEPARATIONS 
Isolation  of  Arsenic  by  Distillation  as  Arsenous  Chloride  2 

By  this  method  arsenic  may  be  separated  from  antimony,  tin,  and  from 
other  heavy  metals.  It  is  of  special  value  in  the  direct  determination  of  arsenic 
in  iron  ores,  copper  ores,  and  like  products  and  has  a  wide  application.  The 
procedure  depends  upon  the  volatility  of  arsenous  chloride  at  temperatures  lower 
than  the  other  heavy  metals.  In  a  current  of  HC1  gas,  arsenous  chloride  begins 
to  volatilize  below  108°  C.,  and  is  actively  volatile  at  120°  C.;  antimony 
starts  to  volatilize  at  125°  C.,  but  is  not  actively  volatile  until  a  temperature 
of  180°  has  been  reached.  The  boiling-point  of  arsenous  chloride,  AsCl3, 
is  130.2°;  antimony  trichloride,  SbCl3,  is  223.5°;  and  that  of  stannous  chloride, 
SnCl2,  is  over  603°;  other  chlorides  having  still  higher  boiling-points.  Tin  in 
its  higher  form,  SnCl4,  is  readily  volatile,  boiling-point  is  114°  C.,  so  that  it  is 
necessary  to  have  it  in  its  divalent  form  to  effect  a  separation  from  arsenic. 
When  heavy  metals  are  present  in  the  residue  remaining  from  the  arsenic  dis- 
tillate, or  when  zinc  chloride  is  added  to  raise  the  boiling-point,  antimony 

1  The  ore  may  be  brought  into  solution  by  fusion  with  a  mixture  of  sodium  car- 
bonate, potassium  nitrate  and  zinc  oxide,  1:1:2.     The  fusion  being  made  in  a  platinum 
dish.     The  potassium  iodide  procedure  may  be  followed  for  reduction  of  arsenic,     (bee 
Lead  Arsenate.) 

2  J.  E.  Stead's  Method.     R.  C.  Roark  and  C.  C.  McDonnell,  Jour.  Ind.  Eng.  Chem., 
VIII,  4,  327  (1916). 


34 


ARSENIC 


may  also  be  separated  by  distillation  by  carrying  the  solution  to  near  dryness, 
adding  concentrated  HC1  by  means  of  a  separatory  funnel,  drop  by  drop,  during 
further  distillation  of  the  concentrate.  Arsenic  may  be  determined  in  the 
distillate  (first  portions)  either  gravimetric  ally  or  volumetrically. 

Procedure.  If  arsenic  is  present  as  arsenic  chloride,  as  prepared  in  the 
method  for  solution  of  iron  ores,  the  sample  may  be  transferred  directly  to 
the  distillation  flask  by  means  of  concentrated,  arsenic-free  hydrochloric  acid. 
If  a  preliminary  separation  of  other  metals  has  been  made  and  arsenic  is 
present  (along  with  antimony  and  tin)  as  a  sulphide,  it  is  oxidized  by  addition 
of  concentrated  HC1  and  sufficient  potassium  chlorate  to  cause  solution  and 
oxidation  of  free  sulphur,  and  the  chlorate  decomposed  by  evaporation  to 


FIG.  1. — Apparatus  for  the  Distillation  of  Arsenous  Acid. 

dryness;  or  if  preferred,  by  evaporation  of  the  alkaline  solution  to  dryness, 
oxidation  with  fuming  nitric  and  re-evaporation  to  dryness  to  expel  the  nitric 
acid.  The  residue  is  taken  up  with  hydrochloric  acid  and  washed  into  the 
flask  with  strong  hydrochloric  acid  as  directed  above. 

Distillation.  The  sample,  in  a  half-liter  distilling  flask  (Fig.  I,  5  ) 
made  up  to  about  150  cc.  with  concentrated  hydrochloric  acid  and  about 
5  grams  of  cuprous  chloride,  Cu2Cl2,  are  added.  The  apparatus  is  connected  up 
as  shown  in  the  illustration,  Fig.  1.  The  end  of  the  condenser  dips  into  400 
cc.  of  cold  water  in  a  large  beaker  (1  liter)  or  flask  ("4").  The  solution  11 
cooled  by  placing  it  in  ice-water  or  cold  running  water.  The  sample  is  satu- 
rated with  dry  hydrogen  chloride  gas  generated  by  dropping  concentrated 
sulphuric  acid  into  strong  hydrochloric  acid  ("3")  and  passing  the  gas  through 


ARSENIC  35 

sulphuric  acid  ("1")  (sp.gr.  1.84)  as  shown  in  cut.  When  the  point  of  satu- 
ration is  reached  the  gas  begins  to  bubble  through  the  solution  instead  of 
being  absorbed  by  it.  When  this  occurs,  heat  is  applied  and  the  solution  brought 
to  boiling,  the  current  of  HC1  gas  being  continued.  At  a  temperature  of  108 
to  110°4C.  the  first  100  cc.  will  contain  practically  all  of  the  arsenic.  About 
two-thirds  of  the  solution  is  distilled  off.  It  is  advisable  to  add  more  hydro- 
chloric acid  to  the  residue  in  the  flask,  together  with  cuprous  chloride,  and  repeat 
the  distillation  into  a  fresh  lot  of  water.  This  may  be  done  during  the  esti' 
mation  of  arsenic  in  the  first  distillate. 

Arsenic  may  be  determined  in  the  distillates  either  gravimetrically  or  volv- 
metrically.  The  volumetric  procedures  for  arsenic,  in  this  isolated  form,  are 
generally  to  be  preferred,  since  they  are  both  rapid  and  accurate.  For  amounts 
over  0.5%  arsenic,  the  iodine  method  is  recommended,  for  smaller  amounts 
(arsenic  in  crude  copper),  precipitation  with  silver  nitrate  and  titration  of  the 
silver  salt  is  best.  Exceedingly  small  amounts  are  best  determined  by  tha 
Gutzeit  method,  page  40. 

Commercial  hydrochloric  acid  invariably  contains  arsenic,  so  this  must  be 
purified  by  redistillation  in  presence  of  an  oxidizing  agent  to  oxidize  the  arsenic 
to  the  non-volatile  arsenic  pentachloride,  AsCl5,  form,  (Fig.  5)  or  by  treatment 
with  H2S  and  filtration.  A  blank  run  should  be  made  on  the  reagents  used, 
especially  when  traces  of  arsenic  are  to  be  determined. 


Separation  of  Arsenic  from  Antimony  and  Tin  by  Precipitation 
as  Sulphide  in  a  Strong  Hydrochloric  Acid  Solution 

This  procedure  for  isolation  of  arsenic  depends  upon  the  insolubility  of  the 
sulphide  of  arsenic  in  strong  hydrochloric  acid,  whereas  that  of  antimony  dissolves. 
The  sulphide  of  tin  is  also  soluble. 

Procedure.  The  metals  present  in  their  lower  conditions  of  oxidation  are 
precipitated  as  sulphides  in  presence  of  dilute  hydrochloric  acid  (5%  solution) 
to  free  them  from  subsequent  groups  (Fe,  Al,  Ca,  etc.).  The  soluble  members 
of  the  hydrogen  sulphide  group  are  now  dissolved  and  separated  from  copper, 
lead,  etc.,  by  caustic  as  follows:  The  greater  part  of  the  washed  precipitate  is 
transferred  to  a  small  casserole,  that  remaining  on  the  filter  paper  is  dissolved 
off  by  adding  to  it  a  little  hot  dilute  potash  solution,  catching  the  filtrate  in  the 
casserole.  About  5  grams  weight  of  solid  potassium  hydroxide  or  sodium  hydroxide 
is  added  to  the  precipitate.  Arsenic,  antimony,  and  tin  sulphides  dissolve.  The 
solution  is  filtered  if  a  residue  remains,  and  the  filter  washed.  This  preliminary 
treatment  is  omitted  if  alkaline  earths  and  alkalies  are  the  only  contaminating 
elements  present. 

The  casserole  containing  the  sample  is  covered  and  placed  on  a  cteam  bath. 
Chlorine  is  now  conducted  into  the  warm  solution  for  an  hour,  whereby  the  alkali 
is  decomposed  and  antimony  and  arsenic  oxidized  to  their  higher  state.  Sufficient 
hydrochloric  acid  is  added  to  decompose  the  chlorate  formed,  and  the  uncovered 
solution  evaporated  to  half  its  volume.  An  equal  volume  of  hydrochloric  acid  is 
added  and  the  evaporation  repeated,  to  expel  the  last  trace  of  chlorine.  The  acid 
solution  is  washed  into  an  Erlenmeyer  flask,  cooled  by  ice  to  0°  C.  and  two  volumes 
of  cooled,  concentrated,  hydrochloric  acid  added.  H2S  gas  is  rapidly  passes  into 


36  ARSENIC 

this  solution  for  an  hour  and  a  half.  The  flask  is  now  stoppered  and  placed  in 
boiling  water  for  an  hour.  The  yellow  arsenic  sulphide,  As2S6,  is  filtered  through 
a  weighed  Gooch  crucible,  washed  with  hydrochloric  acid,  2:1,  until  free  from 
antimony,  i.e.,  the  washing  upon  dilution  remains  clear.  The  residue  is  now 
washed  with  water,  followed  by  alcohol,  and  may  be  dried  and  weighed  as  As2S8, 
or  determined  volumetrically.  Antimony  and  tin  are  determined  in  the  filtrate. 
McCay  recommends  washing  As2S5  with  alcohol,  CS2  and  finally  alcohol.1 

The  sulphide  may  be  dissolved  in  concentrated  sulphuric  acid  by  heating 
to  sulphuric  acid  fumes  and  until  the  solution  becomes  clear.  No  arsenic  is  lost, 
provided  the  heating  is  not  unduly  prolonged.  Fifteen  to  twenty-five  minutes 
is  generally  sufficient  to  dissolve  the  sulphide  and  expel  S02,  etc.  The  acid  may 
be  neutralized  with  ammonia  or  caustic,  made  again  barely  acid  and  then  alkaline 
with  bicarbonate  of  soda,  and  arsenous  acid  titrated  with  iodine.2 


GRAVIMETRIC   METHODS   FOR  DETERMINATION  OF 

ARSENIC 

As  in  the  case  of  antimony,  the  accuracy  and  rapidity  of  the  volumetric 
methods  for  the  determination  of  arsenic  make  these  generally  preferable  to 
the  more  tedious  gravimetric  methods.  The  following  methods,  however,  are 
of  value  in  certain  analytical  procedures. 

Determination  of  Arsenic  as  the  Trisulphide,  As2$3 

Arsenic  acid  and  arsenates  should  be  reduced  to  the  arsenous  form  before 
precipitation  as  the  sulphide.  The  procedure  is  especially  adapted  to  the 
isolation  of  arsenic  from  other  elements,  when  this  substance  is  present  in  the 
solution  in  appreciable  quantities,  advantage  being  taken  of  the  extreme  dif- 
ficulty with  which  arsenous  sulphide,  As2S3,  dissolves  in  hydrochloric  acid 
solution. 

Procedure.  The  solution  containing  arsenic  in  the  arsenious  form  is  made 
strongly  acid  with  hydrochloric  acid  and  hydrogen  sulphide  passed  into  the 
cold  solution  to  complete  saturation.  The  hydrogen  sulphide  pressure  generator 
is  recommended  for  this  treatment.  Figs.  3  and  4.  The  precipitate  is  filtered 
into  a  weighed  Gooch  crucible  (previously  dried  at  105°  C.),  the  compound 
dried  at  105°  C.  to  constant  weight  and  weighed  as  As2S3. 

Factors.    As2S3  X  0.6091  =  grams  As. 

As2S3  X 0.8042  =  grams  As203. 
As203Xl.l616=grams  As206. 
As206Xl.3134  =grams  H3As04-£H20. 
ASaSsX  1.2606  =  grams  As2S6. 

NOTE.  Arsenic  may  also  be  determined  as  arsenic  sulphide  by  passing  a  rapid 
stream  of  H2S  into  a  cooled  solution  of  arsenic  acid  containing  at  least  two  parts  of 
concentrated  hydrochloric  acid  for  each  part  of  water  present  in  the  solution. 

1  Le  Roy  W.  McCay,  Chem.  News,  66,  262  (1887). 

2  J.  and  H.  S.  Pattinson,  Jour.  Soc.  Chem.  Ind.,  1898,  p.  211. 


ARSENIC 


37 


Determination  of  Arsenic  as  Magnesium  Pyroarsenate 


The  method  worked  out  by  Levol  depends  upon  the  precipitation  of  arsenic 
as  MgNH4As04-6H20,  when  magnesia  mixture  is  added  to  an  ammoniacal 
solution, of  the  arsenate.  ^  Although  600  parts  of  water  dissolve  1  part  of  the  salt, 
it  is  practically  insoluble  in  a  2^  per  cent  ammonia  solution,  1  part  of  the  anhydrous 
salt  requiring  24,558  parts  of  the  ammonia  water  according  to  Virgili  i  The 
compound  loses  5|  molecules  of  water  at  102°  C.  and  all  of  the  water  when 


I    :>_ 


FIG.  2. — Urbasch's  Hydrogen  Sulphide  Generator. 

The  apparatus  designed  by  Urbasch  (Chem.  Zeit.  (1910)  34,  1040.  The  Analyst  (1910)  35,  558), 
shown  in  Fig.  2,  enables  a  constant  supply  of  gas  and  its  saturated  aqueous  solution  to  be  obtained. 
1  he  bottle  IV  is  charged  with  hydrochloric  acid,  and  iron  sulphide  is  placed  in  III.  The  hydrogen 
sulphide  is  passed  through  the  water  in  II  until  a  saturated  solution  is  obtained.  Water  is  placed 
in  I  and  II.  If  gas  is  required  the  taps  A  and  B  are  opened  and  H2S  drawn  from  A.  Hydrogen 
sulphide  water  is  obtained  by  opening  the  pinch  cock  C  of  the  burette,  the  liquid  drawn  off  being 
simultaneously  replaced  from  the  vessel  II.  The  container  is  made  of  dark-colored  glass  to  protect 
the  hydrogen  sulphide  water  from  light.  Water  may  be  drawn  into  II,  when  required  by  opening 
the  pinch  cock  leading  to  the  bottle  I. 


strongly  ignited,  forming  in  presence  of  oxygen  the  stable  magnesium  pyro- 
arsenate,  Mg2As207,  in  which  form  arsenic  is  determined. 

Procedure.  The  solution  containing  the  arsenic,  in  the  form  of  arsenate, 
and  having  a  volume  not  exceeding  100  cc.  per  0.1  gram  arsenic  present,  is  treated 
with  5  cc.  of  concentrated  hydrochloric  acid,  added,  with  constant  stirring, 
drop  by  drop.  Ten  cc.  of  magnesia  mixture  are  added  (Reagent  =55  grams 
MgCla+70  grams  NH4C1+650  cc.  H20  and  made  up  to  1000  cc.  with  NH4OH, 
sp.gr.  0.96),  for  each  0.1  gram  of  arsenic  present.  Ammonia  solution  (sp.gr.  0.96) 
is  added  from  a  burette,  with  stirring,  until  the  mixture  is  neutralized  (a  red 
color  imparted  to  the  solution  in  presence  of  phenolphthalein  indicator),  and 
1  Average  of  three  results.  J.  F.  Virgili,  Z.  anal.  Chem.,  44,  504  (1905). 


38 


ARSENIC 


then  ammonia  added  in  excess  equal  to  one-third  the  volume  of  the  neutralized 
solution.  The  precipitate  is  allowed  to  settle  at  least  twelve  hours  and  is  then 
filtered  into  a  weighed  Gooch  crucible  and  washed  with  2.5%  ammonia  until 
free  from  chloride.  After  draining  as  completely  as  possible  by  suction  the 


Stopcock 


Mercury  Valve 

ard  Pressure 

Gauge 


FIG.  3. — Scott's  Hydrogen  Sulphide  Generator. 

Fig.  3  shows  a  convenient  form  of  a  generator  for  obtaining  hydrogen  sulphide  gas  under  pres- 
sure. The  apparatus  is  the  writer's  modification  of  the  Banks'  generator  shown  in  Fig.  4,  and  is 
designed  for  large  quantities  of  hydrogen  sulphide  gas.  The  cylinder  A  A' is  constricted,  as  shown,  to 
support  perforated  lead  disk  G,  upon  which  rests  the  iron  sulphide.  The  lower  end  of  the  cham- 
ber is  closed  to  catch  small  particles  of  FeS  that  may  be  carried  through  the  perforations  of  the 
disk.  Small  openings  admit  the  acid  to  A'.  The  level  of  the  acid  is  below  the  disk  G,  so  that  the 
acid  only  comes  in  contact  with  the  sulphide  when  pressure  is  applied  by  means  of  the  rubber  bulb 
E,  the  stopcock  S1  being  open  and  5s  closed.  The  mercury  gauge  C  is  adjusted  to  blow  out  at  a 
given  pressure,  to  prevent  accident,  the  bulb  D  preventing  the  mercury  from  being  blown  out  of  the 
apparatus.  A  small  opening  in  £>  allows  the  escape  of  the  gas.  When  the  apparatus  is  in  opera- 
tion, H  is  connected  to  an  empty  heavy-walled  bottle,  which  in  turn  is  attached  with  glass  tube 
connection  to  the  pressure  flask  in  which  the  precipitation  of  the  sulphide  is  made,  the  flask  being 
closed  to  the  outside  air.  By  pressure  on  the  rubber  bulb  E,  acid  is  forced  into  the  chamber  A' 
past  the  disk  into  the  sulphide  in  A.  The  entire  system  will  now  be  under  the  pressure  indicated  by 
the  gauge  C-  The  pressure  is  released  by  opening  the  stopcock  <S2  and  the  flask  containing  the  pre- 
cipitate then  disconnected.  The  reservoir  is  des  gned  to  hold  about  two  liters  of  acid,  and  th^ 
cylinder  containing  the  sulphide  is  of  sufficient  capacity  to  hold  over  one  pound  of  FeS,  so  that  the 
apparatus  will  deliver  a  large  quantity  of  hydrogen  sulphide. 

precipitate  is  dried  at  100°  and  then  heated  to  a  dull  red  heat  (400  to  500°  C.), 
preferably  in  an  electric  oven,  until  free  of  ammonia.  The  temperature  is  then 
raised  to  a  bright  red  heat  (800  to  900°  C.)  for  about  ten  minutes,  the  crucible 
then  cooled  in  a  desiccator  and  the  residue  weighed  as  Mg2As207. 

Factors,    MgzAsA X 0.4827  =  As,   or    X0.6373=As20,,    or    X0.7403=As206, 
or  X0.7925=As2S,. 


ARSENIC 


39 


NOTES.  In  place  of  an  electric  furnace  the  Gooch  crucible  may  oe  placed  in 
a  larger  non-perforated  crucible,  the  bottom  of  the  Gooch  being  2-3  mm.  above  the 
bottom  of  the  outer  crucible.  The  product  may  now  be  heated  in  presence  of  a 
current  of  oxygen  passed  through  a  perforation  in  the  covering  lid  of  the  Gooch  or 


Glass 
Pressure 
Bulb 


Special  Rubber  Stopper 


-Glass  Tube  Containing 
the  FeS 


^&OA  ^..--Dilute  Acid  (HiS04) 


-Perforated 
Circular 
Porcelain  Plate 
"Witt  Plate" 


s,  5  'and  s  "«  Screw 
6 top  Cocks  A  ftached 
to  Connecting  Rubber 
Tubing. 


Flask  in  which  the 
Precipitation  under 
Pressure  takes 
Place 


FIG.  4. — Banks'  Hydrogen  Sulphide  Generator. 

Fig.  4  shows  a  simple  and  effective  pressure  generator,  designed  by  Banks.  The  operation  of 
this  small  generator  (200  cc.  capacity)  is  similar  to  the  apparatus,  Fig  3.  It  is  especially  adapted 
for  laboratory  work,  where  individual  apparatus  is  desired  for  students  in  qualitative  and  quantita- 
tive analysis. 

in  place  of  the  oxygen,  a  thin  layer  of  powdered  NH4NO3  may  be  placed  on  the 
arsenate  residue  and  the  heat  gradually  applied  until  the  outer  crucible  attains  a 
light  red  glow. 

VOLUMETRIC  METHODS   FOR  THE  DETERMINATION  OF 

ARSENIC 

Oxidation  of  the  Arsenous  Acid  with  Standard  Iodine 1 

This  procedure  is  applicable  for  the  determination  of  arsenic  in  acids,  after 
reduction  of  arsenic  to  its  arsenous  form,  for  valuation  of  arsenic  in  the  tri- 
oxide,  for  determination  of  arsenic  isolated  by  distillation  as  arsenous  chloride, 
for  arsenic  in  arsenites  and  reduced  arsenates  in  insecticides,  etc.  The  method 
depends  upon  the  reaction— As203+2H20-f  2I2=As205+4HI.  The  liberated 
hydriodic  acid  is  neutralized  by  sodium  bicarbonate.  The  trace  of  excess 
iodine  is  detected  by  means  of  starch,  a  blue  color  being  produced. 

Procedure.  If  the  solution  is  acid,  it  is  neutralized  by  sodium  or  potassium 
hydroxide  or  carbonate  (phenolphthalein  indicator)  then  made  slightly  acid.  If 
the  solution  is  alkaline,  it  is  made  slightly  acid.  Two  to  3  grams  of  sodium 
bicarbonate  are  added  together  with  starch  indicator  and  the  solution  titrated 
with  tenth  normal  iodine  solution,  the  iodine  being  added  cautiously  from  a 
burette  until  a  permanent  blue  color  develops. 

1  Mohr's  Method. 


40  ARSENIC 

One  cc.  N/10  iodine  =0.00375  gram  As,  or  0.004948  gram  As203. 
AsaOsX  1.1616       =As208.    AsX  1.3201  =As203  or  X  1.5336  =  As206. 
As203X  0.7575=  As. 

Volumetric  Determination  of  Arsenic  by  Precipitation  as  Silver 

Arsenate 

Bennett's  modification  of  Pearce's  method,  combining  Volhard's,  depends 
upon  precipitation  of  arsenic,  from  a  solution  neutralized  with  acetic,  by  addition 
of  neutral  silver  nitrate  solution;  the  silver  arsenate  is  dissolved  in  nitric  acid, 
and  the  silver  titrated  with  standard  thiocyanate. 

Procedure.  0.5  gram,  or  less,  of  the  finely  powdered  substance  is  fused 
with  3  to  5  grams  of  a  mixture  of  sodium  carbonate  and  potassium  nitrate  (1:1) 
about  one-third  being  used  on  top  of  the  charge.  The  cooled  mass  is  extracted 
with  boiling  water  and  filtered.  The  filtrate,  containing  the  alkali  arsenate, 
is  strongly  acidified  with  acetic  acid,  boiled  to  expel  the  carbon  dioxide, 
then  cooled  and  treated  with  sufficient  sodium  hydroxide  solution  to  give  an 
alkaline  reaction  to  phenolphthalein  indicator.  The  purple  red  color  is  now 
discharged  from  the  solution  by  addition  of  acetic  acid.  A  slight  excess  of 
neutral  silver  nitrate  is  vigorously  stirred  in  and  the  precipitate  allowed  to  settle 
in  the  dark.  The  supernatant  liquid  is  poured  off  through  a  filter  and  the 
precipitate  washed  by  decantation  with  cold  distilled  water,  then  thrown  on  the 
filter  and  washed  free  of  silver  nitrate  solution.  The  funnel  is  filled  with  water 
and  20  cc.  of  strong  nitric  acid  added.  The  dissolved  silver  arsenate  is  caught 
in  the  original  beaker  in  which  the  precipitation  was  made,  the  residue  on  the 
filter  washed  thoroughly  with  cold  water  and  the  filtrate  and  washings  made 
up  to  100  cc.  The  silver  is  now  titrated  by  addition  of  standard  ammonium 
or  potassium  thiocyanate,  until  a  faint  red  color  is  evident,  using  ferric  ammonium 
alum  indicator,  according  to  the  procedure  described  for  determination  of  silver. 
(See  Chlorine  and  Silver  Chapters.) 

One  cc.  N/10  thiocyanate  =0.010788  gram  Ag. 
Factor.    AgX0.2316=As. 

NOTE.  The  silver  arsenate  salt  is  nearly  six  times  the  weight  of  arsenic,  so 
that  very  small  amounts  of  arsenic  may  be  determined  by  the  procedure,  hence 
it  is  not  necessary  to  use  over  0.5  gram  of  the  material.  For  traces  of  arsenic  the 
Gutzeit  method,  following,  should  be  used. 

DETERMINATION   OF  SMALL  AMOUNTS   OF  ARSENIC 
Modified  Gutzeit  Method  J 

The  following  procedure  furnishes  a  rapid  and  accurate  method  for  deter- 
mination of  exceedingly  small  amounts  of  arsenic  ranging  from  0.001  milli- 
gram to  0.5  milligram  As206.  It  is  more  sensitive  and  less  tedious  than  the 
Marsh  test.  The  details,  given  below  with  slight  modifications,  have  been 
carefully  worked  out  in  the  laboratories  of  the  General  Chemical  Company  l 
and  have  proved  exceedingly  valuable  in  estimating  small  amounts  of  arsenic 
in  acids,  bases,  salts,  soluble  arsenic  in  lead  arsenate  and  zinc  arsenite  and  other 
insecticides,  traces  of  arsenic  in  food  products,  baking  powders,  canned  goods,  etc. 

1  Modification  of  the  method  of  W.  S.  Allen  and  R.  M.  Palmer.  By  courtesy  of 
the  General  Chemical  Company. 


ARSENIC  41 

The  method  depends  upon  the  evolution  of  arsine  by  the  action  of  hydrogen 
on  arsenic  compounds  under  the  catalytic  action  of  zinc,  the  reaction  taking 
place  either  in  alkaline  or  acid  solutions.  The  evolved  arsine  reacts  with  mer- 
curic chloride,  forming  a  colored  compound.  From  the  length  and  intensity 
of  the  -color  stain  the  amount  of  arsenic  is  estimated  by  comparison  with 
standard  stains. 

Arsine  is  evolved  from  an  acid  solution  under  definite  conditions  of  acidity, 
amount  of  zinc  used,  temperature,  strength  of  solution  of  mercuric  chloride 
used  in  sensitizing  the  test-paper,  size  of  apparatus,  volume  of  solution,  amount 
of  iron  accelerator,  and  of  stannous  chloride  reducer,  etc.,  conditions  which 
have  proven,  by  extended  tests,  to  be  most  efficient.  These  conditions  must 
be  adhered  to  for  reliable  results.  For  example,  variation  of  acidity  and  the 
amount  of  zinc  will  produce  stains  of  variable  length  and  intensity  with  equal 
amounts  of  arsenic,  the  stain  being  longer  and  less  intense  with  the  more  rapid 
evolution  of  the  gas.  Likewise  the  greater  the  concentration  of  mercuric 
chloride  on  the  sensitized  paper,  the  shorter  the  length  of  the  stain  and  the 
deeper  its  color. 

Special  Reagents.  Standard  Arsenic  Solution.  One  gram  of  resublimed 
arsenous  acid,  As203,  is  dissolved  in  25  cc.  of  20%  sodium  hydroxide  solution 
(arsenic-free)  and  neutralized  with  dilute  sulphuric  acid.  This  is  diluted  with 
fresh  distilled  water,  to  which  10  cc.  of  95%  H2S04  has  been  added,  to  a 
volume  of  1000  cc.  Ten  cc.  of  this  solution  is  again  diluted  to  a  liter  with  dis- 
tilled water  containing  acid.  Finally  100  cc.  of  the  latter  solution  is  diluted 
to  a  liter  with  distilled  water  containing  acid.  One  cc.  of  the  final  solution 
contains  0.001  milligram  As203. 

Standard  Stains.  Two  sets  of  stains  are  made,  one  for  the  small  apparatus 
for  determining  amounts  of  As203  ranging  from  0.001  to  0.02  milligram,  and  a 
second  set  for  the  larger-sized  apparatus  for  determining  0.02  to  0.5  milligram 
As203.  Stains  made  by  As203  in  the  following  amounts  are  convenient  for  the 
standard  sets;  e.g.,  small  apparatus,  0.001,  0.002,  0.004,  0.006,  0.01,  0.15,  0.02 
milligram  As203.  Large  apparatus,  0.02,  0.05,  0.1,  0.2,  0.3,  0.4,  0.5  milligram 
As203. 

In  making  the  stain  the  requisite  amount  of  standard  reagent,  As203  solution, 
is  placed  in  the  Gutzeit  bottle  with  the  amounts  of  reagents  prescribed  for  the 
regular  tests  and  the  run  made  exactly  as  prescribed  in  the  regular  procedure. 

Preservation  of  the  Stains.  The  strips  of  sensitized  paper  with  the  arsenic 
stain  are  dipped  in  molten  paraffine  (free  from  water),  and  mounted  on  a  sheet 
of  white  paper,  folded  back  to  form  a  cylinder.  The  tube  is  placed  in  a 
glass  test-tube  containing  phosphorus  pentoxide,  which  is  then  closed  u^ 
a  stopper.  It  is  important  to  keep  the  stained  strip  dry,  otherwise  the 
stain  soon  fades,  hence  the  paper  on  which  the  strips  are  mounted  and  the 
glass  test-tube,  etc.,  must  be  perfectly  dry.  It  is  advisable  to  keep  the  standard 
in  a  hydrometer  case,  while  not  in  use,  as  light  will  gradually  fade  the  color. 

Sensitized  Mercuric  Chloride  (or  Bromide)  Paper.  20 X  20  in.  Swedish  Filter 
Paper  No.  0  is  cut  into  four  equal  squares.  For  use  in  the  large  Gutzeit  appa- 
ratus the  paper  is  dipped  into  a  3.25%  solution  of  mercuric  chloride  (mercuric 
bromide  may  be  used  in  place  of  the  chloride)  or  if  it  is  to  be  used  in  the  small 
Gutzeit  apparatus  it  is  dipped  into  a  0.35%  mercuric  chloride  solution.  (The 
weaker  the  solution,  the  longer  and  less  intense  will  be  the  stain.)  The  paper 
should  be  of  uniform  thickness,  otherwise  there  will  be  an  irregularity  in  length  of 


42 


ARSENIC 


stain  for  the  same  amounts  of  arsenic.  (The  thicker  the  paper  the  shorter 
the  stain.  The  paper  is  hung  up  and  dried  in  the  air,  free  from  gas  fumes, 
H2S  being  particularly  undesirable.)  When  dry,  half  an  inch  of  the  outer 
edge  is  trimmed  off  (since  this  is  apt  to  contain  more  of  the  reagent), 
and  the  paper  cut  into  strips.  The  paper  with  more  concentrated  reagent 
is  cut  into  strips  13  cm.  by  5  mm.  and  that  with  0.5%  mercuric  chloride 
into  strips  7  cm.  by  4  mm.  The  paper  is  preserved  in  bottles  with  tight-fitting 


FIG.  5. — Purification  of  Hydrochloric  Acid. 

stoppers.  Standards  should  be  made  with  each  batch  of  paper.  Paper  with 
a  white  deposit  of  HgCl2  should  not  be  used. 

Ferric  Ammonium  Alum.  Eighty-four  grams  of  the  alum  with  10  cc.  of 
mixed  acid  is  dissolved  and  made  up  to  a  liter.  Ten  cc.  of  this  solution  con- 
tains approximately  0.5  gram  Fe208. 

Lead  Acetate.  One  per  cent  solution  with  sufficient  acetic  acid  to  clear 
the  solution. 

Zinc.  Arsenic-free  zinc  shot,  3  to  6-in.  mesh.  The  zinc  is  treated  with  C.  P. 
hydrochloric  acid,  until  the  surface  of  the  zinc  becomes  clean  and  dull.  It  is 


ARSENIC  43 

then  washed,  and  kept,  in  a  casserole,  covered  with  distilled  water,  a  clock-glass 
keeping  out  the  dust. 

Mixed  Acid.  One  volume  of  arsenic-free  H2S04  is  diluted  with  four  vol- 
umes of  pure  water  and  to  this  are  added  10  grams  of  NaCl  per  each  100  cc  of 
solution.-* 

Stannous  Chloride.  Eighty  grams  of  stannous  chloride  dissolved  in  100  cc. 
of  water  containing  5  cc.  arsenic-free  hydrochloric  acid  (1.2  sp.gr.). 

Arsenic-free  Hydrochloric  Acid.  The  commercial  acid  is  treated  with  potas- 
sium chlorate  to  oxidize  the  arsenic  to  its  higher  form  and  the  acid  distilled. 
The  distilling  apparatus  may  be  arranged  so  that  a  constant  distillation  takes 
place,  acid  from  a  large  container  dropping  slowly  into  a  retort  containing 
potassium  chlorate,  fresh  hydrochloric  acid  being  supplied  as  rapidly  as  the 
acid  distills.  See  Fig.  5  on  page  42. 

Lead  Acetate  Test  Paper  for  Removal  of  H2S.  Large  sheets  of  qualitative 
filter  paper  are  soaked  in  a  dilute  solution  of  lead  acetate  and  dried.  The  paper 
is  cut  into  strips  7X5  cm. 

Blanks  should  be  run  on  all  reagents  used  for  this  work.  The  reagents  are 
arsenic-free  if  no  stain  is  produced  on  mercuric  chloride  paper  after  forty-five 
minutes'  test. 

Special  Apparatus.  The  illustration,  Fig.  6  (page  46),  shows  the 
Gutzeit  apparatus  connected  up,  ready  for  the  test.  The  dimensions  on  the 
left-hand  side  are  for  the  small  apparatus  and  those  on  the  right  for  the  large 
form.  Rubber  stoppers  connect  the  tubes  to  the  bottle.  The  apparatus  con- 
sists of  a  wide-mouth  2-oz.  or  8-oz.  bottle  according  to  whether  the  small  or 
large  apparatus  is  desired,  a  glass  tube  (see  Fig.  6)  containing  dry  lead  acetate 
paper  and  moist  glass  wool  for  removal  of  traces  of  hydrogen  sulphide  and  a 
small-bore  tube  containing  the  strip  of  mercuric  chloride  paper. 

Preparation  of  the  Sample 

The  initial  treatment  of  the  sample  is  of  vital  importance  to  the  Gutzeit 
Method  for  determining  traces  of  arsenic.  The  following  procedures  cover 
the  more  important  materials  or  substances  in  which  the  chemist  will  be  called 
upon  to  determine  minute  amounts  of  arsenic. 

Traces  of  Arsenic  in  Acids.  The  acid  placed  in  the  Gutzeit  apparatus 
should  be  equivalent  to  4.2  grams  of  sulphuric  acid  or  3.1  grams  of  hydrochloric 
acid  and  should  contain  0.05  to  0.1  gram  Fe203  equivalent.  If  large  samples 
are  required  for  obtaining  the  test  it  is  necessary  either  to  expel  a  portion  of 
the  acid  in  order  to  obtain  the  above  acidity  or  to  make  standard  stains  under 
similar  conditions  of  acidity.  It  must  be  remembered  that  arsenous  chloride 
is  readily  volatile,  whereas  the  arsenic  chloride  is  not,  hence  it  is  necessary  to 
oxidize  arsenic  before  attempting  to  expel  acids.  If  nitric  acid  or  bromine  or 
chlorine  (chlorate)  be  added  for  this  purpose,  it  must  be  expelled  before  attempting 
the  Gutzeit  test.  Nitric  acid  may  be  expelled  by  adding  sulphuric  acid  and 
taking  to  S03  fumes.  Free  chlorine,  bromine,  or  iodine  will  volatilize  on 
warming  the  solution.  Chlorine  in  a  chlorate  is  expelled  by  taking  the  sample 
to  near  dryness  in  presence  of  free  acid.  Sulphurous  acid  or  hydrogen  sul- 
phide, if  present,  should  be  expelled  by  boiling  the  solution,  then  making  faintly 
pink  with  KMn04  and  destroying  the  excess  with  a  drop  or  so  of  oxalic  acid. 
S02  is  reduced  by  zinc  and  hydrogen  to  H2S,  which  forms  black  HgS  with 


44  ARSENIC 

mercuric  chloride,  hence  removal  of  S02  and  H2S  are  necessary  before  running 
the  test. 

Sulphuric  Acid.  With  amounts  of  arsenic  exceeding  0.00005%  As203,  5  to 
10  grams  of  acid,  according  to  its  strength,  are  taken  for  analysis  and  diluted  to 
15  or  20  cc.  If  H2S  or  S02  are  present,  expel  by  boiling  for  fifteen  or  twenty 
minutes.  Prolonged  fuming  of  strong  acid  should  be  avoided  by  previously  dilut- 
ing the  acid  with  sufficient  water.  In  mixed  acid  containing  nitric  acid  the 
sample  is  taken  to  S03  fumes  to  expel  nitric  acid.  The  procedure  given  later  for 
the  regular  determination  is  now  followed. 

For  estimating  very  minute  amounts  of  arsenic,  0.000005  to  0.00005%  As203, 
it  is  necessary  to  take  a  25-  to  50-gram  sample  for  analysis.  The  acid  is  treated 
as  directed  above  for  removal  of  H2S  or  S02  or  nitric  acid  and  diluted  in  the 
Gutzeit  apparatus  to  at  least  130  cc.,  using  the  large  apparatus.  Upon  the 
addition  of  iron  and  stannous  chloride  as  directed  in  the  procedure  described  on 
page  46  for  large  Gutzeit  test.  The  stains  are  compared  with  standard  stains 
produced  by  known  amounts  of  arsenic  added  to  50-gram  portions  of  arsenic- 
free  sulphuric  acid  of  strength  equal  to  that  of  the  sample.  The  stains  are  longer 
and  less  intense  than  those  produced  by  less  acid. 

Hydrochloric  Acid.  Twenty  cc.  is  taken  for  analysis  (sp.gr.  being  known); 
the  sample  should  contain  an  acid  equivalent  of  about  3.1  grams  of  hydrochloric 
acid.  Chlorine  is  expelled  by  bubbling  air  through  the  acid  before  taking  a 
sample.  The  procedure  is  given  for  further  treatment  of  the  sample  following 
the  section  on  preparation  of  the  sample. 

Nitric  Acid.  One  hundred  cc.  of  the  acid  (sp.gr.  being  known)  is  evap- 
orated with  5  cc.  of  concentrated  sulphuric  acid  to  S03  fumes,  to  expel  nitric 
acid.  Arsenic  is  determined  in  the  residue  by  the  standard  procedure. 

Iron  Ores,  Pyrites,  Burnt  Pyrites,  Cinders,  etc.  One  gram  of  the  finely 
ground  ore  is  oxidized  by  treating  with  5  cc.  of  a  mixture  of  2  parts  liquid 
bromine  and  3  parts  of  carbon  tetrachloride.  After  fifteen  minutes,  10  cc.  of 
concentrated  nitric  acid  are  added  and  the  mixture  taken  to  dryness.  Five  cc. 
of  concentrated  sulphuric  acid  (95%)  are  added  and  the  mixture  taken  to  S03 
fumes  to  expel  the  nitric  acid.  The  cooled  sample  is  taken  up  with  50  cc.  of 
water  and  digested  until  all  of  the  iron  sulphate  has  dissolved;  it  is  now  washed 
into  a  100-cc.  flask,  made  to  volume,  and  arsenic  determined  in  an  aliquot  portion 
in  the  usual  way,  given  later.  Insoluble  Fe203,  briquettes,  etc.,  is  best  dis- 
solved by  fusion  with  potassium  bisulphate,  KHS04.  The  fused  mass  is  dis- 
solved in  warm  dilute  hydrochloric  acid,  and  then  washed  into  the  Gutzeit 
bottle. 

Alumina  Ores.  Bauxite.  One  gram  of  bauxite  is  treated  with  one  part 
of  concentrated  nitric  acid  and  6  parts  of  concentrated  hydrochloric  acid,  and 
taken  to  dryness  on  the  water  bath.  The  residue  is  taken  up  with  an  equiv- 
alent of  4.7  grams  of  hydrochloric  acid  or  6.3  grams  of  sulphuric  acid  in  a 
volume  of  25  cc.  and  the  mix  heated  until  the  material  has  dissolved.  The 
sample  is  diluted  to  exactly  100  cc.  and  arsenic  determined  on  an  aliquot 
portion. 

Phosphates,  Phosphoric  Acid.  Arsenic,  in  phosphoric  acid,  combined  or 
free,  cannot  be  determined  in  the  usual  way,  as  P2O6  has  a  retarding  effect 
upon  the  evolution  of  arsine,  so  that  the  results  are  invariably  low,  and  small 
amounts  of  arsenic  escaping  detection.  Arsenic,  however,  may  be  volatilized  from 
phosphates  and  phosphoric  acid,  as  arsenous  chloride,  AsCl3,  in  a  current  of 


ARSENIC 


45 


hydrogen  chloride  by  heating  to  boiling.  One  gram  or  more  of  the  phosphate 
is  placed  in  a  small  distilling  flask,  connected  directly  to  a  6-in.  coil  condenser 
dipping  into  the  Gutzeit  bottle,  containing  20  to  30  cc.  of  cold  distilled  water 
A  second  bottle  connected  in  series  may  be  attached  for  safeguarding  loss  (this 
seldom  Qccurs).  Fifty  cc.  of  concentrated  hydrochloric  acid  are  added  to  the 
sample  and  5  grams  of  cuprous,  chloride.  Arsenic  is  distilled  into  the  Gutzeit 
bottle  by  heating  the  solution  to  boiling  and  passing  a  current  of  air  through 
strong  hydrochloric  acid  into  the  distilling  flask  by  applying  suction  at  the  re- 
ceiving end  of  the  system.  All  of  the  arsenic  will  be  found  in  the  first  10  or  15 
cc.  of  the  distillate.  Arsenic  may  now  be  evolved  after  addition  of  iron,  stannous 
chloride  and  zinc,  as  directed  in  the  procedure. 

Salts,  Sodium  Chloride,  Magnesium  Sulphate,  etc.  One-gram  samples 
are  taken  and  dissolved  in  a  little  water  and  an  equivalent  of  6.3  grains 
of  sulphuric  acid  added.  The  solution  of  iron  and  stannous  chloride  having 
been  added,  the  run  is  made  with  5  cc.  of  zinc  shot,  placed  in  the  Gutzeit 
bottle. 

Baking  Powder,  Other  than  Phosphate  Baking  Powder.  A  10-gram 
sample  is  heated  with  10  cc.  hydrochloric  acid,  10  cc.  of  ferric  ammonium  alum 
and  30  cc.  of  distilled  water,  until  the  starch  hydrolyzes.  0.5  cc.  of  stannous 
chloride  is  added  to  the  hot  solution  and  the  mixture  washed  into  the  Gutzeit 
apparatus.  The  required  amount  of  zinc  is  added  and  the  arsenic  determined  as 
usual. 

Phosphate  Baking  Powders.  Ten  grams  of  the  material  mixed  to  a  paste 
with  about  50  cc.  of  hydrochloric  acid  are  transferred  to  a  small  distilling  flask 
with  a  few*,  cc.  of  HC1.  A  tube,  connected  to  a  bottle  of  strong  hydrochloric 
acid,  passes  into  the  mixture  in  the  flask  through  a  ground  glass  stopper.  The 
flask  is  attached  to  a  tube,  which  dips  into  water  in  a  Gutzeit  bottle.  Two 
grams  of  cuprous  chloride  are  added,  the  apparatus  made  tight  and  the  flask 
immersed  in  boiling  hot  water.  By  aspirating  air  through  the  system  into  the 
Gutzeit  bottle,  which  is  water  cooled,  arsenic  distills  into  the  bottle  and  may  be 
determined  by  the  procedure  outlined. 

Arsenic  in  Organic  Matter,  Canned  Goods,  Meat,  etc.  The  finely  chopped, 
well-mixed  sample  is  placed  in  a  large  flask  and  enough  water  added  to  pro- 
duce a  fluid  mass.  An  equal  quantity  of  concentrated  hydrochloric  acid  and 
1  to  2  grams  of  potassium  chlorate  are  added.  The  flask  is  shaken  to  mix  the 
material  and  it  is  then  placed  on  the  steam  bath.  Upon  becoming  hot,  nascent 
chlorine  is  evolved  and  vigorously  attacks  the  organic  matter.  Half-gram 
portions  of  potassium  chlorate  are  added  at  five-minute  intervals,  shaking  the 
flask  frequently.  When  the  organic  material  has  decomposed  and  the  solution 
becomes  a  pale  yellow  color,  the  mass  is  diluted  with  water  and  filtered.  Arsenic 
will  be  found  in  the  filtrate.  A  white,  amorphous  substance  generally  remains 
on  the  filter,  when  cadaver  is  being  examined.  The  filtrate  is  diluted  to  a 
given  volume  and  an  aliquot  portion  taken  for  analysis.  This  is  evaporated  to 
near  dryness  to  expel  excess  of  acid  and  decompose  chlorates.  An  equivalent 
of  4.7  grams  of  hydrochloric  acid  is  added  (three  times  this  amount  for  the 
large  apparatus),  the  volume  of  the  solution  made  to  about  30  cc.,  10  cc.  of  ferric 
ammonium  alum  and  0.5  cc.  of  stannous  chloride  added,  and  the  solution  poured 
into  the  Gutzeit  apparatus  for  the  test  as  given  below. 


46 


ARSENIC 


1  Large  Apparatus- 

.16  cm.  long  X 
\y  7.5 mm.  Bore 
T"  Constricted 
12cm.  from 
J|     Upper  End 


.-6cm.  x  1.5  cm 


Procedure  for  Making  the  Test 

For  amounts  of  arsenic  varying  from  0.001  milligram  to  0.02  milligram  As203, 
the  small  apparatus  is  used.  The  volume  of  the  solution  should  be  50  cc.  It 
should  contain  an  equivalent  of  4.2  to  6.3  grams  sulphuric  acid  and  should  have 

about  0.1  gram  equivalent  of  Fe203  reduced  by  0.5 
cc.  of  stannous  chloride  solution.  Arsine  is  gen- 
erated by  adding  one  5-cc.  crucible  of  arsenic-free 
zinc  shot,  \  to  |-inch  mesh.  Temperature  75  to 
80°  F. 

For  amounts  ranging  from  0.02  to  0.5  milli- 
gram AS203,1  the  large  apparatus  is  used.  The 
volume  of  the  solution  should  be  about  200  cc. 
and  should  contain  an  equivalent  of  18.5  grams 
of  sulphuric  acid  and  should  have  0.1  gram  equiva- 
lent of  Fe203,  reduced  by  0.5  cc.  stannous  chloride 
solution.  Arsine  is  generated  by  adding  one  12-cc. 
crucible  of  zinc  shot  Q  to  £-inch  mesh.)  The  tem- 
perature should  be  105°  F.  The  sample  taken 
should  be  of  such  size  that  a  stain  is  obtained 
equivalent  to  that  given  by  0.1  to  0.5  milligram 
As203. 

Lead  acetate  paper  is  placed  in  the  lower  por- 
tion of  tube  B-,  the  upper  portion  of  B  contains 
glass  wool  moistened  with  lead  acetate  solution; 
the  tube  A  contains  the  test  strip  of  mercuric 
chloride  paper.  See  Fig.  6.  Immediately  upon 
adding  the  required  amount  of  zinc  to  the  solution 
in  the  bottles,  the  connected  tubes  are  put  in 
position,  as  shown  in  the  illustration,  and  the 
bottle  gently  shaken  and  allowed  to  stand  for  one 
hour  for  the  small  apparatus,  forty  minutes  for  the 
large.  The  test  paper  is  removed,  dipped  in 
molten  paraffine  and  compared  with  the  standard 
stains.  See  Plate  I. 


Small  Apparatus 
/Ocm.  long  x  N 
4mm.  Bore     \ 
Constricted 
6  cm.  from 
Upper  End 


Strip  HgCl2  - 
Paper  in  Tube 


Scm.x  /.25cm} 


Glass  Wool        \ 
Moistened 

with  Lead  *> 

Acetate 
Solution 


Dry  Lead. — 
Acetate  Paper 


^-oz.  Bottle 
eOcc.,for 
Tests  of 


FIG.  6. — Gutzeit    Apparatus 
for  Arsenic  Determination. 


Estimation  of  Per  cent. 


The  milligram  As203  stain  X 100 
Weight  of  sample  taken 


As2O3. 


1  It  is  advisable  to  use  smaller  samples  when  the  arsenic  content  is  over  0.3  milli- 
gram As2O3,  as  the  longer  stains  are  unreliable. 

Ferrous  iron  prevents  polarization  between  zinc  and  the  acid  and  hence  aids  in  the 
evolution  of  arsine. 

In  the  analysis  of  baking  powders,  bauxite,  sodium  or  similar  salts,  the  distillation 
method  is  recommended.  See  pages  44  and  45,  "  Phosphates,"  and  "  Phosphate  baking 
powder." 

Hydrochloric  acid  is  used  in  place  of  sulphuric  acid  in  cases  where  complete  solu- 
tion by  the  latter  acid  cannot  be  effected. 

Standards  and  samples  should  be  run  under  similar  conditions,  temperature, 
acidity,  amount  of  zinc,  volume  of  solution,  etc.  In  place  of  zinc  shot,  zinc  rods,  cubes 
or  discs  may  be  used  for  generating  arsine  and  hydrogen. 


ARSENIC  47 

METHOD  FOR  ANALYSIS  OF  COMMERCIAL  "  ARSENIC  " 
ARSENOUS  OXIDE,  As2O3 

The  following  constituents  may  be  commonly  present  as  impurities  SiO-> 
Sb203,  Fe203,  NiO,  CoO,  CaO,  S03,  Cu,  Pb,  and  Zn. 

Determination  of  Moisture 

Two  10-gram  samples  are  dried  to  constant  weight  in  the  oven  at  100°  C- 
Loss  in  weight  = moisture. 

Sulphuric  Acid,  H2SO4 

The  samples  from  the  moisture  determination  are  dissolved  in  concentrated 
hydrochloric  acid,  heating  to  boiling  if  necessary,  and  the  samples  diluted  to 
300  to  400  cc.  Barium  chloride  solution  is  added  in  slight  excess  to  the  hot 
solution,  the  precipitate,  BaS04,  allowed  to  settle  and  filtered  and  the  sulphate 
dried  and  ignited  as  usual. 

BaS04X  0.343  =S03. 
Determination  of  Arsenic  as  As2Os 

Duplicate  5-gram  samples  are  dissolved  in  20  grams  potassium  carbonate 
in  60  cc.  of  hot  water,  by  boiling  until  solution  is  effected.  The  samples  are 
made  up  to  1  liter  and  aliquots  of  100  cc.  (=0.5  gram)  taken  for  analysis.  The 
solution  is  made  faintly  acid  with  hydrochloric  acid,  testing  the  solution  with 
litmus  paper  or  by  adding  methyl  orange  directly  to  the  solution.  An  excess 
of  bicarbonate  is  added  and  the  arsenic  titrated  with  tenth-normal  iodine 
according  to  the  standard  procedure  for  arsenic.  One  cc.  N/10  I  =.004948 
gram  As203. 

Residue  upon  Sublimation  of  As2O3.    SiO2,  Pb,  Cu,  Fe2Os,  NiO, 

CoO,  Zn 

Two  5-gram  samples  are  weighed  into  tared  porcelain  crucibles  and  heated 
gently  on  sand  baths  with  the  sand  banked  carefully  around  the  crucible  so 
as  to  heat  the  entire  receptacle.  After  the  greater  part  of  the  arsenous  oxide 
has  volatilized,  the  crucible  is  ignited  directly  in  the  flame  to  a  dull  red  heat, 
until  fumes  are  no  longer  given  off.  The  residue  is  weighed  as  total  non-sub- 
limable  residue. 

Silica 

The  residues  are  transferred  to  beakers  and  treated  with  aqua  regia,  taken 
to  dryness,  and  the  silica  dehydrated  at  110°  C.  for  an  hour  or  more.  The 
residue  is  taken  up  with  hot  dilute  hydrochloric  acid,  boiled,  and  the  silica 
filtered  off,  ignited,  and  weighed. 

Lead  and  Copper 

The  filtrate  from  the  silica  is  "  gassed  "  with  H2S  and  the  precipitate  filtered 
off.  The  filtrate  is  put  aside  for  determination  of  iron,  etc.  The  precipitate  is 
dissolved  in  hot  dilute  nitric  acid,  2  to  3  cc.  of  concentrated  sulphuric  acid  added, 


48  ARSENIC 

the  solution  taken  to  S03  fumes,  the  cooled  concentrate  diluted  to  20  or  30  cc., 
and  the  lead  sulphate  filtered  off,  ignited,  and  weighed  as  PbS04. 

The  filtrate  from  the  lead  sulphate  containing  the  copper  is  treated  with 
aluminum  powder  and  the  copper  thrown  out  of  solution;  the  excess  of  alumi- 
num is  dissolved  with  a  few  cc.  of  hydrochloric  acid.  The  filtrate  should  be 
tested  for  copper  with  H2S  and  the  precipitate  added  to  the  copper  thrown 
out  by  the  aluminum.  The  copper  on  the  filter  is  dissolved  in  hot  dilute  nitric 
acid,  the  extract  evaporated  to  2  or  3  cc.,  the  acid  neutralized  with  ammonia 
and  then  made  acid  with  acetic,  potassium  iodide  added  and  the  liberated  iodine 
titrated  with  standard  thiosulphate  solution  according  to  the  regular  scheme  for 
copper. 

Iron,  Nickel,  Cobalt,  and  Zinc 

The  filtrate  from  the  H2S  Group  is  boiled  to  expel  the  H2S  and  the  iron 
oxidized  by  addition  of  nitric  acid  and  boiling.  The  iron  (and  alumina)  is 
precipitated  with  ammonium  hydroxide  and  the  precipitate  filtered  off  and 
washed  several  times  with  hot  water.  If  alumina  is  suspected  (light-colored 
precipitate)  it  may  be  determined  by  the  difference  method — ignition  of  the 
precipitate,  weighing,  and  finally  subtracting  the  iron  found  by  titration  with 
standard  stannous  chloride  solution.  The  iron  is  dissolved  in  hydrochloric  acid 
and  titrated  hot  with  stannous  chloride  solution. 

The  filtrate  from  the  iron  is  boiled  and  a  1%  alcoholic  solution  of  dimethyl- 
glyoxime  added  to  precipitate  the  nickel.  The  salt  is  filtered  on  a  tared 
Gooch,  the  precipitate  dried  at  100°  C.,  and  weighed.  The  weight  of  the 
salt  X  0.2032  =Ni. 

The  filtrate  from  the  nickel  is  boiled  until  all  the  alcohol  has  been  driven 
off  and  the  cobalt  precipitated  by  addition  of  sodium  hydroxide  in  excess 
filtered,  ignited,  and  weighed  as  CoO. 

The  filtrate  is  made  acid  with  hydrochloric  acid,  and  then  alkaline  with 
ammonium  hydroxide  and  colorless  sodium  sulphide  solution  added  to  pre- 
cipitate the  zinc.  The  mixture  is  boiled  five  to  ten  minutes,  the  precipitated 
ZnS  allowed  to  settle,  filtered  off,  and  washed  once  or  twice  and  then  dissolved 
in  hydrochloric  acid  and  the  zinc  determined  by  titration  directly  with  potassium 
ferrocyanide,  or  by  converting  to  the  carbonate  by  addition  of  potassium  car- 
bonate, filtered  and  washed  free  of  alkali,  the  precipitate  dissolved  in  a  known 
amount  of  standard  acid,  and  the  excess  acid  titrated  with  standard  caustic 
(methyl  orange  indicator)  according  to  the  procedure  given  for  zinc. 
H2S04X0.06665=Zn. 

Antimony  and  Calcium  Oxides 

Two  15-gram  samples  are  treated  with  300  cc.  of  concentrated  hydrochloric 
acid,  boiled  down  to  50  cc.  to  expel  the  arsenic  as  AsCl3,  an  equal  amount 
of  concentrated  hydrochloric  acid  is  added,  and  the  last  traces  of  arsenic  pre- 
cipitated by  H2S  passed  into  the  hot  concentrated  hydrochloric  acid  solution. 
The  arsenous  sulphide,  As2S3,  is  filtered  off.  Antimony  is  precipitated  by  dilut- 
ing the  solution  with  an  equal  volume  of  water,  the  solution  having  been  concen- 
trated by  boiling  down  to  about  50  cc.  The  Sb2S3  is  filtered  off,  washed  several 
times  with  hot  water,  dissolved  by  washing  through  the  filter  with  concentrated 
hydrochloric  acid,  and  antimony  determined  in  the  strong  hydrochloric  acid 
solution  by  the  potassium  bromate  method — addition  of  methyl  orange  indicator 


ARSENIC  49 

and  titration  with  standard  potassium  bromate  added  to  the  hot  solution  to  the 
disappearance  of  the  pink  color  of  the  indicator. 

The  filtrate  from  the  antimony  is  concentrated,  made  slightly  alkaline  with 
ammonium  hydroxide,  and  gased  with  hydrogen  sulphide  to  remove  iron,  nickel, 
cobalt,  0inc,  chromium,  and  last  traces  of  lead,  etc.  The  filtrate  is  then  con- 
centrated and  made  acid  with  crystals  of  oxalic  acid,  boiled  and  methyl  orange 
added  and  then  ammonia  drop  by  drop  slowly  until  the  indicator  changes  to 
an  orange  color.  An  excess  of  ammonium  oxalate  is  now  added  and  the  beaker 
placed  on  the  steam  bath  until  the  calcium  oxalate  has  settled.  The  lime  is 
now  determined  by  filtering  oft7  the  precipitate  and  washing,  drying  and  igniting 
to  CaO,  or  by  titration  with  standard  permanganate,  according  to  the  regular 
procedure  for  calcium. 

The  author  wishes  to  acknowledge  the  assistance  received  from  Mr.  J.  P.  Kelly  and 
Dr.  F.  E.  Hale  by  review  and  criticism  of  this  chapter. 


BARIUM 

WILFRED  W.  SCOTT 

Ba,  at.wt.  137.37;  sp.gr.  3.78;  m.p.  850°  C.;  volatile  at  950°  C.;  oxides, 

BaO,  BaO2. 

DETECTION 

Barium  is  precipitated  as  the  carbonate  together  with  strontium  and  cal- 
cium; by  addition  of  ammonium  hydroxide  and  ammonium  carbonate  to  the 
filtrate  of  the  ammonium  sulphide  group.  It  is  separated  from  strontium 
and  calcium  by  precipitation  as  yellow  barium  chromate,  BaCr04,  from  a  slightly 
acetic  acid  solution. 

Saturated  solutions  of  calcium  or  strontium  sulphates  precipitate  white 
barium  sulphate,  BaS04,  from  its  chloride  or  nitrate  or  acetate  solution,  barium 
sulphate  being  the  least  soluble  of  the  alkaline  earth  sulphates. 

Soluble  chromates  precipitate  yellow  barium  chromate  from  its  neutral 
or  slightly  acetic  acid  solution,  insoluble  in  water,  moderately  soluble  in  chromic 
acid,  soluble  in  hydrochloric  or  nitric  acid. 

Fluosilicic  acid,  H2SiF6,  precipitates  white,  crystalline  barium  fluosilicate, 
BaSiF6,  sparingly  soluble  in  acetic  acid,  insoluble  in  alcohol.  (The  fluosilicates 
of  calcium  and  strontium  are  soluble.) 

Flame.  Barium  compounds  color  the  flame  yellowish  green,  which  appears 
blue  through  green  glass. 

Spectrum.1    Three  characteristic  green  bands  (a,  /3,  7). 

Barium  sulphate  is  precipitated  by  addition  of  a  soluble  sulphate  to  a  solu- 
tion of  a  barium  salt.  The  compound  is  extremely  insoluble  in  water  and 
in  dilute  acids  (soluble  in  hot  concentrated  sulphuric  acid).  The  sulphate  is 
readily  distinguished  from  lead  sulphate  by  the  fact  that  the  latter  is  soluble 
in  ammonium  salts,  whereas  barium  sulphate  is  practically  insoluble. 

ESTIMATION 

The  determination  of  barium  is  required  in  the  valuation  of  its  ores,  barite* 
heavy  spar,  BaS04;  witherite,  BaC03;  baryto  calcite,  BaC03CaC03.  It  is  de- 
termined in  certain  white  mixed  paints  and  colored  pigments,  Venetian,  Ham- 
burg or  Dutch  whites,  chrome  paints,  etc.  In  analysis  of  Paris  green,  baryta 
insecticides,  putty,  asphalt,  dressings  and  pavement  surfacings.  It  may  be 
found  as  an  adulterant  in  foods,  wood  preservatives,  filler  in  rubber,  rope, 
fabrics.  It  is  determined  in  salts  of  barium.  The  nitrate  is  used  in  pyro- 
techny,  in  mixtures  for  green  fire. 

Preparation  and  Solution  of  the  Sample 

Compounds  of  barium,  with  the  exception  of  the  sulphate,  BaS04,  are  sol- 
uble in  hydrochloric  and  nitric  acids.  The  sulphate  is  soluble  in  hot  concen- 

1  See  Preliminary  Tests  under  Separations. 
60 


BARIUM  51 

trated  sulphuric  acid,  but  is  reprecipitated  upon  dilution  of  the  solution.  The 
sulphate  is  best  fused  with  sodium  carbonate,  which  transposes  the  compound 
to  barium  carbonate;  sodium  sulphate  may  now  be  leached  out  with  water  and 
the  residue,  BaC03,  then  dissolved  in  hydrochloric  acid. 

Solution  of  Ores.  Sulphates.  0.5  to  1  gram  of  the  finely  divided  ore  is 
fused  with  3  to  5  grams  of  sodium  and  potassium  carbonate  mix,  2:1,  or 
sodium  carbonate  alone,  in  a  platinum  dish.  (Prolonged  fusion  is  not  nec- 
essary.) The  melt  is  cooled  and  then  extracted  with  hot  water  to  dissolve 
out  the  alkali  sulphates.  Barium  carbonate,  together  with  the  other  insoluble 
carbonates,  may  now  be  dissolved  by  hot  dilute  hydrochloric  acid.  From  this 
solution  barium  may  be  precipitated  by  addition  of  sulphuric  acid.  If  it  is 
desired  to  separate  barium  along  with  strontium,  calcium,  and  magnesium, 
the  members  of  the  preceding  groups  are  removed  by  H2S  in  acid  and  in  ammo- 
niacal  solution,  as  directed  under  "  Separations." 

Sulphides.  The  ore  is  oxidized,  as  directed  for  pyrites  under  the  subject 
of  sulphur.  After  the  removal  of  the  soluble  sulphates,  the  residue,  containing 
silica,  barium,  and  small  amounts  of  insoluble  oxides,  is  fused  and  dissolved 
according  to  the  procedure  for  sulphates. 

Carbonates.  In  absence  of  sulphates  the  material  may  be  dissolved  with 
hydrochloric  acid,  taken  to  dryness  to  dehydrate  silica  and  after  heating  for 
an  hour  in  the  steam  oven  (110°±)  the  residue  is  extracted  with  dilute  hydro- 
chloric acid  and  filtered.  The  filtrate  is  examined  for  barium  according  to 
one  of  the  procedures  given  later. 

Salts  Soluble  in  Water.  Nitrates,  chlorides,  acetates,  etc.,  are  dissolved 
with  water  slightly  acidulated  with  hydrochloric  acid. 

Material  Containing  Organic  Matter.  The  substance  is  roasted  to  destroy 
organic  matter  before  treatment  with  acids  or  by  fusion  with  the  alkali  carbonates. 

The  Insoluble  Residue  remaining  from  the  acid  treatment  of  an  ore  may 
contain  barium  sulphate  in  addition  to  silica,  etc.  The  filter  containing  this 
residue  is  burned  and  the  ash  weighed.  Silica  is  now  volatilized  by  addition 
of  hydrofluoric  acid  with  a  few  drops  of  sulphuric  acid,  and  evaporation  to 
dryness.  If  an  insoluble  substance  still  remains  after  taking  up  the  remaining 
residue  with  dilute  hydrochloric  acid,  barium  sulphate  is  indicated.  This  is 
treated  according  to  the  method  given  for  sulphates. 

NOTE.  The  insoluble  substance  remaining  is  frequently  ignited  and  weighed  as 
barium  sulphate  without  fusion  with  the  carbonate. 

SEPARATIONS 
The  Alkaline  Earths 

Preliminary  Considerations.  In  the  determination  of  barium,  calcium, 
and  strontium,  the  following  causes  may  lead  to  loss  of  the  elements  sought; 

a.  Presence  of  Phosphates.  Phosphoric  acid,  free  or  combined,  has  a  decided 
influence  upon  the  determination  of  the  members  of  this  group.  Combined 
as  phosphate  it  will  cause  the  complete  precipitation  of  barium,  calcium,  and 
strontium,  along  with  iron,  alumina,  etc.,  upon  making  the  solution  alkaline 
for  removal  of  the  ammonium  sulphide  group.  It  is  a  common  practice  to 
hold  up  the  iron+alumina  by  means  of  tartaric,  citric,  or  other  organic  acids 
before  making  ammoniacal  for  precipitation  of  this  group  as  oxalates,  or  again 
the  basic  acetate  method  is  used  for  precipitation  of  iron  and  alumina;  calcium, 


52  BAKIUM 

barium,  and  strontium  going  into  solution.  These  procedures  may  be  satis- 
factory for  the  analysis  of  phosphate  rock  and  similar  products,  but  do  not  cope 
with  the  difficulty  when  large  amounts  of  phosphates  are  present.  In  samples 
containing  free  phosphoric  acid,  barium,  calcium,  and  strontium,  present  in 
small  amounts,  may  remain  in  solution  in  presence  of  sulphates  or  oxalates. 
Appreciable  amounts  of  calcium,  1%  or  more,  may  escape  detection  by  the 
usual  method  of  precipitation  by  ammonium  oxalate  added  to  the  alkaline 
solution,  on  account  of  this  interference,  so  that  the  removal  of  phosphoric  acid 
before  precipitation  of  this  group  is  frequently  necessary.  This  may  be  ac- 
complished by  addition  of  potassium  carbonate  in  sufficient  excess  to  combine 
completely  with  the  phosphoric  acid  and  form  carbonates  with  the  bases.  The 
material  taken  to  dryness  is  fused  with  additional  potassium  carbonate  in  an 
iron  crucible,  and  the  fusion  leached  with  hot  water — sodium  phosphate  dis- 
solves and  the  carbonates  of  the  heavy  metals  remain  insoluble. 

b.  Another  source  of  loss  is  the  presence  of  sulphates,  either  in  the  original 
material  or  by  intentional  or  accidental  addition,  in  the  latter  case  due  to  the 
oxidation  of  hydrogen  sulphide,  which  has  been  passed  into  the  solution  during 
the  removal  of  elements  of  the  hydrogen   sulphide    and   ammonium    sulphide 
groups,  barium    and  strontium   sulphate    being  precipitated  along  with  these 
members.    A  potassium   carbonate    fusion  will  form  Na2S04,   which  may  be 
leached  out  with  water. 

c.  Loss  may  be  caused  by  occlusion  of  barium,  calcium,  strontium,  and  mag- 
nesium by  the  gelatinous  precipitates  Fe(OH)3,  A1(OH)3,  etc.    A  double  precipita- 
tion of  these  compounds  should  be  made  if  considerable  amounts  are  present. 

d.  A  large  excess   of  ammonium  salts,  which    accumulate  during  the  pre- 
liminary separations,  will  prevent  precipitation  of  the  alkaline  earths.    This 
can  be  avoided  by  using  the  necessary  care  required  for  accurate  work,  the 
addition  of  reagents  by  means   of  burettes  or  according  to  definite  measure- 
ments in  graduates,  etc.     Careless   addition  of  large  amounts  of  ammonium 
hydroxide  and  hydrochloric   acid   should   be  guarded  against.    In  case  large 
amounts  of  ammonium   chloride  are  present,  time  is  frequently  saved  by  a 
repetition  of  the  separations.    Ammonium  chloride  may  be  expelled  by  heating 
the  material,  taken  to  dryness  in  a  large  platinum  dish,  the  ammonium  salts 
being  volatilized. 

e.  Carbon   dioxide   absorbed   by   ammonium   hydroxide   from   the   air  will 
precipitate  the  alkaline  earths  with  the  ammonium  sulphide  group. 

Direct  Precipitation  on  Original  Sample.  For  the  determination  of 
barium,  calcium,  and  strontium,  it  is  advisable  to  take  a  fresh  sample,  rather 
than  one  that  has  been  previously  employed  for  the  estimation  of  the  hydrogen 
sulphide  and  ammonium  sulphide  groups,  as  is  evident  from  the  statements 
made  above.  The  alkaline  earths  are  isolated  by  being  converted  to  the  insol- 
uble sulphates  and  separations  effected  as  given  later  under  Sulphate  Method. 

Preliminary  Tests.  Much  time  may  be  saved  by  making  a  preliminary 
test  for  barium,  strontium,  and  calcium  by  means  of  the  spectroscope  ancJ 
avoiding  unnecessary  separations.  By  this  means  one-thousandth  of  a 'milli- 
gram of  barium,  six  hundred-thousandths  of  a  milligram  of  strontium  or  calcium 
may  be  detected.  The  characteristic  spectra  of  these  elements  are  given  in 
the  chart.  Plate  II. 

By  means  of  the  spectroscope  with  the  use  of  the  ordinary  Bunsen  flame 
0.2  milligram  of  calcium,  0.6  milligram  of  strontium  and  14  milligrams  of  barium 


BAKIUM  53 

may  be  detected  per  cc.  The  test  is  very  much  more  delicate  by  the  arc  spectra 
method.1  The  liquid  containing  the  substance  is  connected  to  the  positive 
pole  and  an  iridium  needle  is  connected  by  means  of  an  adjustable  resistance 
of  300  to  500  ohms  to  the  negative  pole.  An  E.M.F.  of  100  to  200  volts  and 
1  ampere  current  are  required.  By  the  arc  it  is  possible  to  detect  0.002  milli- 
gram of  calcium,  0.003  milligram  of  strontium,  0.006  milligram  of  barium, 
0.1  milligram  of  magnesium  per  cc.  In  these  concentrations,  calcium  shows 
one  brilliant  line  (423  MM),  a  bright  line  (616  MM),  and  a  faint  line  between  them; 
strontium  two  bright  lines  (422  and  461  MM)  and  two  fairly  bright  lines;  barium 
two  brilliant  lines  (455  and  493  MM),  two  other  bright  lines,  and  a  fairly  bright 
one;  and  magnesium  a  brilliant  band  composed  of  three  lines  (516.8  to  518.4 
MM),  as  well  as  a  fairly  bright  line  further  towards  the  violet  end  of  the  spectrum. 

The  flame  test  may  be  of  value  in  absence  of  sodium;  barium  giving  a  green 
flame,  strontium  a  brilliant  scarlet,  and  calcium  an  orange  red. 

Separation  from  Members  of  Previous  Groups.  The  members  of  the 
previous  groups  may  be  removed  by  precipitation  as  sulphides  by  H2S  passed 
into  the  acid  and  then  the  alkaline  solutions,  the  combined  nitrates  concen- 
trated to  about  300  cc.  and  made  slightly  acid  with  hydrochloric  acid.  The  fol- 
lowing procedures  for  isolation  of  barium  from  magnesium  and  the  alkalies 
and  from  members  of  the  alkaline  earth  group  may  be  necessary  before  pre- 
cipitation in  its  final  form.  The  methods  of  separation  will  apply  to  the  analyses 
of  the  elements  mentioned  so  that  the  details  of  procedure  will  not  be  given 
elsewhere. 

Separation  of  the  Alkaline  Earths  from  Magnesium  and  the  Alkalies. 
Two  general  procedures  will  cover  conditions  commonly  met  with  in  analytical 
work: 

A.  Oxalate  Method.  Applicable  in  presence  of  comparatively  large 
portions  of  calcium.  The  acid  solution  containing  not  over  1  gram  of  the 
mixed  oxides  is  brought  to  a  volume  of  350  cc.  and  for  every  0.1  gram  of  mag- 
nesium present  about  1  gram  of  ammonium  chloride  is  added,  unless  already 
present.  Sufficient  oxalic  acid  is  added  to  completely  precipitate  the  barium, 
calcium,  and  strontium.2  (H2C204-2H20  =  126.04,  Ba  =  137.37,  Ca=40.07, 
Sr=  87.63.)  The  solution  is  slowly  neutralized  by  addition,  drop  by  drop,  of 
dilute  ammonium  hydroxide  (1  :  10),  methyl  orange  being  used  as  indicator. 
About  ^  gram  of  oxalic  acid  is  now  added  in  excess,  the  solution  again  made 
alkaline  with  ammonium  hydroxide,  and  allowed  to  settle  for  at  least  two  hours. 
The  precipitate  is  filtered  off  and  washed  with  water  containing  1%  ammonium 
oxalate,  faintly  alkaline  with  ammonia. 

The  precipitate  contains  all  the  calcium  and  practically  all  of  the  barium 
and  strontium.  If  Mg  is  present  in.  amounts  of  10  to  15  times  that  of  the 
alkaline  earths  a  double  precipitation  is  necessary,  to  remove  it  completely  from 
this  group.  The  oxalates  are  dissolved  in  hydrochloric  acid  and  reprecipi- 
tated  with  ammonium  oxalate  in  alkaline  solution. 

The  filtrate  contains  magnesium  and  the  alkalies.  Traces  of  barium  and 
strontium  may  be  present.  If  the  sample  contains  a  comparatively  large 
proportion  of  barium  and  strontium,  the  filtrate  is  evaporated  to  dryness, 
the  ammonium  salts  expelled  by  gentle  ignition  of  the  residue,  and  the  Ba  and 

*E.  H.Riesenfeld  and  G.  Pfiitzer,  Ber.,  1913,  46,  3140-3144;  Analyst,  1913,  38,  584. 
2  Calcium  and  strontium  will  slowly  precipitate  in  the  oxalic  acid  solution.     Ba 
oxalate  will  precipitate  upon  making  the  solution  alkaline. 


54  BARIUM 

Sr  recovered  as  sulphates  according  to  the  method  described  below.  Mag- 
nesium is  precipitated  as  magnesium  ammonium  phosphate  from  the  nitrate. 

The  oxalates  of  barium,  calcium,  and  strontium  are  ignited  to  oxides,  in  which 
form  they  may  be  readily  converted  to  chlorides  by  dissolving  in  hydrochloric 
acid,  or  to  nitrates  by  nitric  acid. 

B.  Sulphate  Method.  Applicable  in  presence  of  comparatively  large  pro- 
portions of  barium,  strontium,  or  magnesium.  The  solution  containing  the 
alkaline  earths,  magnesium  and  the  alkalies  is  evaporated  to  dryness  and 
about  5  cc.  concentrated  sulphuric  acid  added,  followed  by  50  cc.  of  95% 
alcohol.  The  sulphates  1  of  barium,  calcium,  and  strontium,  are  allowed  to 
settle,  and  then  filtered  onto  an  S.  and  S.  No.  589  ashless  filter  paper  and  washed 
with  alcohol  until  free  of  magnesium  sulphate.  In  presence  of  large  amounts 
of  magnesium  as  in  case  of  analyses  of  Epsom  salts  and  other  magnesium  salts 
it  will  be  necessary  to  extract  the  precipitate  by  adding  a  small  amount  of  water, 
then  sufficient  95%  alcohol  to  make  the  solution  contain  50%  alcohol  and 
filter  from  the  residue.  Magnesium  is  determined  in  the  filtrate. 

The  residue  containing  barium,  calcium,  and  strontium  as  sulphate  is 
fused  with  10  parts  of  potassium  carbonate  or  sodium  acid  carbonate  until  the 
fusion  becomes  a  clear  molten  mass,  a  deep  platinum  crucible  being  used  for 
the  fusion.  A  platinum  wire  is  inserted  and  the  mass  allowed  to  solidify.  The 
fusion  may  be  removed  by  again  heating  until  it  begins  to  melt  around  the 
surface  next  to  the  crucible,  when  it  may  be  lifted  out  on  the  wire.  The  mass 
is  extracted  with  hot  water  and  filtered,  Na2S04  going  into  the  solution  and 
the  carbonates  of  barium,  strontium,  and  calcium  remaining  insoluble.  The 
carbonates  should  dissolve  completely  in  hydrochloric  acid  or  nitric  acid,  other- 
wise the  decomposition  has  not  been  complete,  and  a  second  fusion  of  this 
insoluble  residue  will  be  necessary. 

Separation  of  the  Alkaline  Earths  from  One  Another.  This  separation 
may  be  effected  by  either  of  the  following  processes: 

1.  Barium  is  separated  in  acetic  acid  solution  as  a  chromate  from  strontium 
and  calcium;   strontium  is  separated  as  a  nitrate 2  from  calcium  in  ether-alcohol 
or  amyl  alcohol. 

2.  The  three  nitrates  are  treated  with  ether-alcohol  in  which  barium  and 
strontium   nitrates  are  insoluble  and  calcium  dissolves;    the  barium  is   now 
separated  from  strontium  by  ammonium  chromate. 

Procedures.  1.  (a)  Separation  of  Barium  from  Strontium  (and  from 
Calcium).  In  presence  of  an  excess  of  ammonium  chromate,  barium  is  pre- 
cipitated from  solutions,  slightly  acid  with  acetic  acid,  as  barium  chromate 
(appreciably  soluble  in  free  acetic  acid),  whereas  strontium  and  calcium  remain 
in  solution. 

The  mixed  oxides  or  carbonates  are  dissolved  in  the  least  amount  of  dilute 
hydrochloric  acid  and  the  excess  of  acid  expelled  by  evaporation  to  near  dryness. 
The  residue  is  taken  up  in  about  300  cc.  of  water  and  5-6  drops  of  acetic  acid 
(sp.gr.  1.065)  together  with  sufficient  ammonium  acetate  (30%  solution)  to 
neutralize  any  free  mineral  acid  present.  The  solution  is  heated  and  an  excess 
of  ammonium  chromate  (10%  neutral  sol.) 3  added  (10  cc.  usually  sufficient). 

Solubility  of  BaSO4=0.17  milligram,  CaSO4  =  179  milligram,  SrSO4  =  11.4  milli- 
grams per  100  cc.  sol.  cold. 

2  Method  of  Stromayer  and  Rose.     H.  Rose,  Pogg.  Ann.,  110,  292,  (1860). 

3  The  solution  is  prepared  by  adding  NH4OH  to  a  solution  of  (NH4)2Cr2O7  until 
yellow.    The  solution  should  be  left  acid  rather  than  alkaline. 


BARIUM  55 

The  precipitate  of  barium  chromate  is  allowed  to  settle  for  an  hour  and  filtered 
off  on  a  small  filter  and  washed  with  water  containing  ammonium  chromate 
until  free  o£  soluble  strontium  and  calcium  (test — addition  of  NH4OH  and 
(NH4)2C03  produces  no  cloudiness),  and  then  with  water  until  practically  free  of 
ammonium  chromate  (e.g.,  only  slight  reddish  brown  color  with  silver  nitrate 
solution). 

To  separate  any  occluded  precipitate  of  strontium  or  calcium  the  filter 
paper  is  pierced  and  the  precipitate  rinsed  into  a  beaker  with  warm  dilute  nitric 
acid  (sp.gr.  1.20)  (2  cc.  usually  are  sufficient).  The  solution  is  diluted  to  about 
200  cc.  and  boiled.  About  5  cc.  of  ammonium  acetate,  or  enough  to  neutralize 
the  free  HN03>  are  added  to  the  hot  solution  and  then  sufficient  ammonium 
chromate  to  neutralize  the  free  acetic  acid,  10  cc.  usually  sufficient.  The  washing, 
as  above  indicated,  is  repeated.  Barium  is  completely  precipitated  and  may 
be  determined  either  as  a  chromate  or  a  sulphate  or  by  a  volumetric  pro- 
cedure. Strontium  and  calcium  are  in  the  filtrates  and  may  be  separated  as 
follows: 

(b)  Separation  of  Strontium  from  Calcium.  The  method  depends  upon 
the  insolubility  of  strontium  nitrate  and  the  solubility  of  calcium  nitrate  in 
a  mixture  of  ether-alcohol,  1:1. 

Solubility  of  SrN03  =  l  part  SrN03  in  60,000  parts  of  the  mixture.  Ca 
easily  soluble. 

If  the  solution  is  a  filtrate  from  barium,  1  cc.  of  nitric  acid  is  added  and 
the  solution  heated  and  made  alkaline  with  ammonium  hydroxide  followed 
immediately  with  ammonium  carbonate,  the  carbonates  of  strontium  (together 
with  some  SrCr04)  and  calcium  will  precipitate.  The  precipitate  is  dissolved 
in  hydrochloric  acid  and  reprecipitated  from  a  hot  solution  with  ammonium 
hydroxide  and  ammonium  carbonate.  The  precipitate,  SrC03  and  CaC03, 
is  washed  once  with  hot  water  and  is  then  dissolved  in  the  least  amount  of 
nitric  acid,  washed  into  a  small  casserole,  evaporated  to  dryness  and  heated 
for  an  hour  at  140  to  160°  C.  in  an  oven,  or  at  110°  C.  over  night.  The  dry 
mass  is  pulverized  and  mixed  with  10  cc.  of  ether-alcohol  (absolute  alcohol,  one 
part,  ether-anhydrous,  one  part).  Several  extractions  are  thus  made,  the  extracts 
being  decanted  off  into  a  flask.  The  residue  is  again  dried  in  an  oven  at  140 
to  160°  C.,  then  pulverized  and  washed  into  the  flask  with  the  ether-alcohol 
mixture  and  digested  for  several  hours  with  frequent  shaking  of  the  flask.  The 
residue  is  washed  onto  a  filter  moistened  with  ether-alcohol  mixture.  Strontium 
nitrate,  Sr(N03)2,  remains  insoluble,  and  may  be  dissolved  in  water  and  de- 
termined gravimetrically  as  a  sulphate,  oxide,  or  carbonate  or  volumetrically. 
Calcium  is  in  the  filtrate  and  may  be  determined  gravimetrically  as  an  oxide 
or  volumetrically. 

Instead  of  using  a  mixture  of  ether-alcohol,  amyl  alcohol  may  be  used  (hood), 
the  mixture  being  kept  at  boiling  temperature  to  dehydrate  the  alcohol  to  pre- 
vent solution  of  strontium  (b.p.  =130°  C.). 

2.  Separation  of  Barium  and  Strontium  from  Calcium.1  The  procedure 
depends  upon  the  insolubility  of  barium  nitrate,  (BaN03)2,  and  strontium  nitrate, 
Sr(NQ«>2,  in  a  mixture  of  anhydrous  ether  and  absolute  alcohol  or  anhydrous 
amyl  alcohol,  whereas  Ca(N03)2  dissolves. 

The  mixed  oxides  or  carbonates  are  dissolved  in  nitric  acid  and  taken  to 
dryness  in  a  beaker  or  Erlenmeyer  flask,  and  heated  for  an  hour  or  more  in  an 
iSee  Fresenius,  Z.  anal.  Chem.,  29,  413  430  (1890). 


56  BARIUM 

oven  at  140  to  160°  C.  Upon  cooling,  the  mixture  is  treated  with  ten  times 
its  weight  of  ether-alcohol  mixture  and  digested,  cold,  in  the  covered  beaker 
or  corked  flask  for  about  two  hours  with  frequent  stirring.  An  equal  volume 
of  ether  is  now  added  and  the  digestion  continued  for  several  hours  longer. 
The  residue  is  washed  by  decantation  with  ether  and  alcohol  mixture  until 
calcium  is  removed  (test — no  residue  on  platinum  foil  with  drop  of  filtrate  evap- 
orated to  dryness).  If  calcium  is  present  in  amount  above  0.5  gram,  the  residue 
is  dissolved  in  a  little  water,  again  evaporated  and  dried  and  then  extracted 
with  ether-alcohol  as  directed  above. 

Calcium  is  in  the  filtrate  and  may  be  determined  by  precipitation  as  a  sul- 
phate in  the  alcohol  solution  or  as  an  oxide  by  evaporation  of  the  ether-alcohol 
and  precipitation  as  calcium  oxalate,  CaC204,  according  to  directions  given  in 
the  determination  of  calcium. 

Barium  and  strontium  may  be  separated  by  precipitation  of  barium  as  a 
chromate,  the  nitrate  residue  being  dissolved  in  water  and  barium  precipitated 
according  to  directions  given  under  Procedure  No.  1. 

Amyl  alcohol  may  be  used  in  place  of  ether-alcohol  by  digesting  the  nitrates 
in  a  boiling  solution  (130°  C.),  calcium  going  into  solution  and  barium  and 
strontium  remaining  insoluble  as  nitrates. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION    OF 

BARIUM 

For  reasons  given  under  " Preliminary  Considerations,"  it  is  advisable  to 
take  a  special  sample  for  the  determination  of  barium  that  has  not  undergone 
treatment  with  hydrogen  sulphide  or  ammonium  hydroxide,  since  these  may 
cause  the  loss  of  barium  as  stated. 

Preparation  of  the  Sample.  The  following  general  schemes  will  meet 
practically  all  conditions: 

Barium  in  Insoluble  Residue.  In  the  complete  analysis  of  ores  the  residue 
remaining  insoluble  in  acids  is  composed  largely  of  silica,  together  with  difficultly 
soluble  substances,  among  which  is  barium  sulphate.  This  residue  is  best  fused  in  a 
platinum  dish  with  sodium  carbonate  or  a  mixture  of  sodium  and  potassium  car- 
bonates (long  fusion  is  not  necessary) .  The  cooled  mass  is  digested  with  hot  water 
to  remove  the  soluble  sodium  compounds,  silicate  being  included.  Barium,  to- 
gether with  the  heavy  metals,  remains  insoluble  as  carbonate  and  may  be  filtered 
off.  The  residue  is  now  treated  with  dilute  ammonia  water  to  remove  the 
adhering  sulphates  (testing  the  filtrate  with  hydrochloric  acid  and  barium  chlo- 
ride solution;  the  washing  being  complete  when  no  white  precipitate  of  barium 
sulphate  forms).  The  carbonates  are  washed  off  the  filter  into  a  500-cc.  beaker, 
the  clinging  carbonate  being  dissolved  by  pouring  a  few  cc.  of  dilute,  1  :  1,  hydro- 
chloric acid  on  the  paper  placed  in  the  funnel.  This  extract  is  added  to  the  pre- 
cipitate in  the  beaker  and  the  latter  covered  to  prevent  loss  by  spattering. 
Additional  hydrochloric  acid  is  cautiously  added  so  that  the  precipitate  com- 
pletely dissolves  and  the  solution  contains  about  10  cc.  of  free  hydrochloric 
acid  (sp.gr.  1.2).  Barium  is  precipitated  from  this  solution  best  as  a  sulphate 
according  to  directions  given  later. 

Silicates.    One  gram  of  the    finely  pulverized    sample  is  treated  with  10 


BARIUM  57 

cc.  of  dilute  sulphuric  acid,  1  :  4,  and  5  cc.  of  strong  hydrofluoric  acid.  The 
mixture,  evaporated  to  small  bulk  on  the  steam  bath,  is  taken  to  S03  fumes 
on  the  hot  plate.  Additional  sulphuric  acid  and  hydrofluoric  acid  are  used  if 
required.  By  this  treatment  the  silica  is  expelled  and  barium,  together  with 
other  insoluble  sulphates,  will  remain  upon  the  filter  when  the  residue  is  treated 
with  water  and  filtered.  Lead  sulphate,  if  present,  may  be  removed  by  washing 
the  residue  with  a  solution  of  ammonium  chloride.  Barium  sulphate  may  be 
purified  by  fusion  with  potassium  carbonate  as  above  directed  or  by  dissolving 
in  hot  concentrated  sulphuric  acid,  and  precipitating  again  as  BaS04  by  dilution. 
Ores  may  be  decomposed  by  either  of  the  above  methods  or  a  combination 
of  the  two.  Sulphide  ores  require  roasting  to  oxidize  the  sulphide  to  sulphate. 

Determination  of  Barium  as  a  Chromate 

A  preliminary  spectroscopic  test  has  indicated  whether  a  separation  from 
calcium  and  strontium  is  necessary.  If  these  are  present,  barium  is  separated 
along  with  strontium  from  calcium  as  the  nitrate  in  presence  of  alcohol-ether 
mixture,  according  to  directions  given  under  " Separations."  Barium  is  now 
precipitated  as  the  chromate,  BaCr04,  from  a  neutral  or  slightly  acetic  acid 
solution,  strontium  remaining  in  solution. 

Precipitation  of  Barium  Chromate.  If  barium  is  present  in  the  form 
of  nitrate,  together  with  strontium,  the  mixed  nitrates  are  evaporated  to  dryness 
and  then  taken  up  with  water.  About  10  cc.  ammonium  acetate  (300  grams 
NH4C2H302  neutralized  with  NH4OH+H20  to  make  up  to  1000  cc.)  added 
and  the  solution  heated  to  boiling.  Five  cc.  of  20%  ammonium  bichromate 
are  added  drop  by  drop  with  constant  stirring  and  the  precipitate  allowed  t:> 
settle  until  cold.  The  solution  is  decanted  off  from  the  precipitate  through 
a  filter  and  washed  by  decantation  with  dilute  (0.5%)  solution  of  ammonium 
acetate,  until  the  excess  chromate  is  removed,  as  indicated  by  the  filtrate  passing 
through  uncolored.  If  much  strontium  was  originally  present,  a  double  pre- 
cipitation is  necessary,  otherwise  the  precipitate  may  be  filtered  directly  into 
a  Gooch  crucible  and  ignited,  the  following  paragraph  directions  being  omitted. 

Purification  from  Strontium.  The  precipitate  is  dissolved  from  the  filter 
by  running  through  dilute  (1  :  5)  warm  nitric  acid,  poured  upon  the  chromate, 
catching  the  solution  in  the  beaker  in  which  the  precipitation  was  made;  the 
least  amount  of  acid  necessary  to  accomplish  this  being  used  and  the  filter 
washed  with  a  little  warm  water.  Ammonium  hydroxide  is  now  added  to  the 
solution,  cautiously,  until  a  slight  permanent  precipitate  forms  and  then  10  cc. 
of  ammonium  acetate  solution  added  with  constant  stirring  and  the  mixture 
heated  to  boiling.  The  precipitate  is  allowed  to  settle  until  the  solution  is  cold 
and  then  filtered  and  washed  by  decantation  as  before,  a  Gooch  crucible  being 
used  to  catch  the  precipitate. 

Ignition.  The  precipitate  is  washed  once  with  dilute  alcohol,  1  :  10,  dried 
at  110°  C.,  and  ignited,  gently  at  first  and  then  to  a  dull  red  heat  until  the 
color  of  the  chromate  is  uniform.  It  is  advisable  to  cover  the  crucible  at  first 
and  then  after  five  minutes  to  remove  the  cover. 


BaCr04X0.6051  =BaO.     BaCr04X0.5420  =Ba. 

use  of  sodium  h 
hydroxide  and  acetate  is  sometimes 


NOTES.      The    use  of  sodium  hydrate  or  acetate  in  place  of  the    ammonium 

a  recommended,  owing  to  the  slight  solubility  oi 


58  BARIUM 

BaCrO4  in  ammonium  salts,  as  seen  by  the  following  table,  approximate  figures  being 

given : 

100,000  parts  of  cold  water  dissolves  0.38  parts  BaCrO4 

100,000  parts  of  hot  water  dissolves  4.35  parts  BaCrO4 

100,000  of  0.5%  solution  of  NH4C1  dissolves  4.35  parts  BaCrO4 

100,000  of  0.5%  solution  of  NH4NO3  dissolves  2.22  parts  BaCrO4 

100,000  of  0.75%  solution  of  NH4C2H3O2  dissolves  2.00  parts  BaCrO4 
100,000  of  1.5%  solution  of  NH4C2H3O2  dissolves  4.12  parts  BaCrO4 
100,000  of  1%  acetic  acid  dissolves  20.73  parts  BaCrO4 

Although  the  solvent  action  of  ammonium  salts  is  practically  negligible  under 
conditions  of  analysis  given  above,  the  solvent  action  of  free  acetic  acid  is  of  importance, 
so  that  it  is  necessary  to  neutralize  or  eliminate  free  mineral  acids  before  addition 
of  the  acetate  salt. 

The  edges  of  the  BaCrO4  precipitate  upon  drying  may  appear  green,  owing  to 
the  action  of  alcohol;  upon  ignition,  however,  the  yellow  chromate  is  obtained.  The 
color  orange  yellow,  when  hot,  fades  to  a  light  canary  yellow  upon  cooling. 

BaCrO4,  mol.wt.,  253.47;  sp.gr.,  4.498150;  100  cc.  H2O  sol.  cold  will  dissolve 
0.00038 18°  gram,  hot  dissolves  0.0043  gram;  soluble  in  HC1,  HNO3,  yellow  rhombic 
plates. 

Determination  of  Barium  by  Precipitation  as  Sulphate,  BaSO4 

This  method  depends  upon  the  insolubility  of  barium  sulphate  in  water 
and  in  very  dilute  hydrochloric  acid  or  sulphuric  acid,  one  gram  of  the  salt 
requiring  about  344,000  cc.  of  hot  water  to  effect  solution. 

Reaction,  BaCl2+H2S04  =BaS04+2HCl. 

BaS04,  mol.wt.,  233,44;  sp.gr.,  4 .47  and  4.33;  m.p.,  1580°  (amorphous  decom- 
poses); H20  dissolves  0.000172°°  gram  and  0.000334°  per  100  cc.  3%  HC1  dissolves 
0.0036  gram.  Soluble  in  cone.  H2S04.  White,  rhombic  and  amorphous  forms. 

Procedure.  The  slightly  hydrochloric  acid  solution  of  barium  chloride, 
prepared  according  to  directions  given,  is  heated  to  boiling  (volume  about  200- 
300  cc.)  and  a  slight  excess  of  dilute  hot  sulphuric  acid  added.  The  precipitate 
is  settled  on  the  water  bath  and  the  clear  solution  then  decanted  through  a 
weighed  Gooch  crucible  or  through  an  ashless  filter  paper  (S.  and  S.  590  quality). 
The  precipitate  is  transferred  to  the  Gooch  (or  paper),  and  washed  twice  with 
very  dilute  sulphuric  acid  solution  (0.5%  H2S04),  and  finally  with  hot  water 
until  free  of  acid.  The  precipitate  is  dried  and  ignited,  at  first  gently  and  then 
over  a  good  flame  to  a  cherry  red  heat,  for  half  an  hour.  The  residue  is  weighed 
as  barium  sulphate,  BaS04. 

BaS04X 0.5884  =Ba,  or  X0.6569=BaO,  or    X 0.8455  =BaC03. 

NOTE.-*.  The  determination  of  barium  is  the  reciprocal  of  the  determination  of 
sulphur  or  sulphuric  acid.  Precautions  and  directions  given  for  the  sulphur  pre- 
cipitation apply  here  also,  with  the  exception  that  dilute  sulphuric  acid  is  used  as 
the  precipitating  reagent  in  place  of  barium  chloride. 

The  author  found  that  precipitation  of  barium  sulphate  in  a  large  volume  of  cold 
solution  containing  10  cc.  of  concentrated  hydrochloric  acid  per  1600  cc.  of  solution, 
by  adding  a  slight  excess  of  cold  dilute  sulphuric  acid  in  a  fine  stream,  exactly  in 
the  manner  that  barium  chloride  solution  is  added  in  the  precipitation  of  sulphur, 
and  allowing  the  precipitate  to  settle,  at  room  temperature,  for  several  hours  (pref- 
erably over  night),  gives  a  precipitate  that  is  pure  and  does  not  pass  through  the 
Gooch  asbestos  mat.  We  refer  to  the  chapter  on  Sulphur  for  directions  for  filtering, 
washing,  and  ignition  of  the  residue. 


BARIUM  59 


VOLUMETRIC   METHODS   FOR  THE   DETERMINATION   OF 

BARIUM 

Titration  of  the  Barium  Salt  with  Dichromate 

This  method  is  of  value  for  an  approximation  of  the  amount  of  barium 
present  in  a  solution  that  may  also  contain  calcium,  strontium,  and  magnesium 
or  the  alkalies.  It  depends  upon  the  reaction 

2BaCl2+K2Cr207+H20=2BaCr044-2KCl+2HCl. 

N/10  K2Cr207  (precipitation  purposes)  contains  7.355  grams  pure  salt  per 
liter. 

Procedure.  The  solution  containing  the  barium  is  treated  with  ammonia 
until  it  just  smells  of  it.  (If  an  excess  of  ammonia  is  present  the  solution  is  made 
faintly  acid  with  acetic  acid.)  It  is  then  heated  to  about  70°  C.  and  the 
standard  dichromate  added,  with  stirring  until  all  the  barium  is  precipitated 
and  \the  clear  supernatant  solution  is  a  faint  yellow  color  from  the  slight 
excess  of  the  reagent.  For  accurate  work  it  is  advisable  to  titrate  the  pre- 
cipitate formed  by  one  of  the  methods  given  below.  One  cc.  K2Cr207=  0.00687 
gram  Ba.  (Note  reaction  given  above.) 

NOTE.  An  excess  of  potassium  dichromate  maybe  added,  the  precipitate  filtered 
off,  washed  and  the  excess  of  dichromate  determined  as  stated  below. 

Reduction  of  the  Chromate  with  Ferrous  Salt  and  Titration  with 

Permanganate 

Ferrous  sulphate  reacts  with  barium  chromate  as  follows : 

2BaCr04+6FeS04+8H2S04=3Fe2(S04)3+Cr2(S04)3+2BaS04+8H20. 

An  excess  of  ferrous  salt  solution  is  added  and  the  excess  determined  by 
titration  with  N/10  KMn04  solution.  Fe  =  £Ba. 

Reagents.  N/10  solution  of  KMn04.  N/10  FeS04  (27.81  grams  per  liter) 
or  FeS04-  (NH4)2S04  (39.226  grams  per  liter).  One  cc.  =0.004579  Ba. 

Procedure.  The  well- washed  precipitate  of  barium  chromate  is  dissolved 
in  an  excess  of  standard  N/10  ferrous  ammonium  sulphate  solution  containing 
free  sulphuric  acid.  The  excess  ferrous  salt  is  titrated  with  standard  N/10 
potassium  permanganate  solution. 

(Cc.  N/10  ferrous  solution  minus  cc.  permanganate  titration)  multiplied  by 
0.004579  gives  grams  barium  in  the  solution.  Iron  factor  to  barium  is  0.8187. 

Potassium  Iodide  Method 

The  procedure  depends  upon  the  reactions : 

1.  2BaCr04+6KI+16HCl  =2BaCl2+2CrCl3+6KCl+8H20+6I. 

2.  3I2+6Na2S203  =6NaI+3Na2S406. 

Procedure.  The  precipitate,  BaCr04,  is  dissolved  in  50  to  100  cc.  of 
dilute  hydrochloric  acid  and  about  2  grams  of  solid  potassium  iodide  salt^  added 
and  allowed  to  react  about  ten  minutes.  The  liberated  iodine  is  now  titrated 


60  BARIUM 

with  N/10  thiosulphate.     Near  the  end  of  the  titration  starch  solution  is  added 
and  followed  by  N/10  thiosulphate  until  the  color  disappears. 

One  cc.  N/10  Na2S203  =0.004579  gram  Ba. 

Titration  of  Barium  Carbonate  with  Standard  Acid 

To  the  well-washed  barium  carbonate,  BaC03,  an  excess  N/10  H2S04  is  added 
and  the  excess  acid  determined. 

One  cc.  N/10  acid  =0.00687  gram  Ba. 

ANALYSIS  OF  BARYTES  AND  WITHERITE 

Barytes  or  heavy  spar  is  a  variety  of  native  barium  sulphate,  and  witherite 
a  native  barium  carbonate.  These  minerals  are  typical  examples  of  barium- 
bearing  ores.  The  analysis  may  involve  the  determination  of  barium  and 
calcium  sulphates  or  carbonates,  magnesia,  iron  and  aluminum  oxides  and 
moisture.  Traces  of  lead,  copper,  and  zinc  may  be  present,  as  well  as  sulphide, 
sulphur  and  fluorine  in  fluorspar.  The  following  is  an  approximate  composition 
of  a  high-grade  sample: 


BaS04  =  96%,  CaC03  =  1.5%,  MgC03=0.3%,  Si02=0.5%,  A1203=0.5%, 
Fe203=0.2%,H20=0.5%. 

For  complete  analysis  treat  as  directed  under  preparation  of  the  sample. 

Procedure  for  Commercial  Valuation  of  the  Ore 

Barium  Sulphate  and  Silica 

One  gram  of  the  finely  pulverized  sample  is  digested  with  about  50  cc.  of 
concentrated  hydrochloric  acid  and  taken  to  dryness  on  the  steam  bath.  The 
residue  is  taken  up  with  50  cc.  of  water,  10  cc.  of  hydrochloric  acid  added, 
and  the  mixture  heated  on  the  steam  bath  for  ten  minutes,  then  heated  to  boil- 
ing and  filtered.  The  residue  of  barium  sulphate  and  silica  is  washed  well  with 
hot  water  containing  a  little  hydrochloric  acid  and  finally  with  pure  water.  It 
is  now  ignited  and  weighed  as  BaS04-f  Si02,  or  total  insoluble  matter. 

The  residue  in  a  platinum  dish  is  now  treated  with  a  little  hydrofluoric 
acid  +  sulphuric  acid,  and  silica  expelled  as  usual.  The  residue  ignited  =BaS04. 

Silica  =  difference  between  total  insoluble  matter  and  BaS04. 

Barium  Carbonate 

Barium,  originally  present  as  a  carbonate,  will  be  found  in  the  filtrate  together 
with  iron,  alumina,  etc.,  and  may  be  precipitated  by  addition  of  sulphuric  acid. 
Barium  sulphate  is  filtered  off,  washed,  ignited,  and  weighed.  BaS04X  0.84555 
=BaC08. 

Iron  and  Alumina  Oxides 
These  are  determined  in  the  filtrate  from  barium  precipitation  in  the  usual  way. 


BARIUM  61 

Calcium  and  Magnesium 

Determined  in  the  filtrate  from  iron  and  alumina  by  the  regular  procedures. 

,  Soluble  Sulphates 

One  gram  of  the  powdered  sample  is  boiled  with  20  cc.  cone.  HC1  and  200 
cc.  water,  the  insoluble  residue  filtered  off  and  washed.  The  filtrate  contains 
the  soluble  sulphate.  This  may  be  precipitated  by  addition  of  BaCl2  solution 
according  to  the  procedure  for  sulphur.  B aS04X 0.5833  =CaS04.  BaS04X 
0.2402  =CaO. 

If  lime,  CaO,  thus  calculated,  is  less  than  lime  precipitated  as  oxalate,  the 
difference  is  calculated  to  CaC03  if  C02  is  present,  otherwise  to  CaO. 

Loss  on  Ignition 
Represents  water  free  and  combined,  carbon  dioxide  and  organic  matter. 


BISMUTH 

WILFRED  W.  SCOTT 

Bl,  af.zrt.  308.0;  sp.gr.  9.7474;    m.p.  271°  ;*  b.p.   1420°  C.;    oxides, 

Bi2O3,  Bi2O6. 

DETECTION 

Bismuth  is  precipitated  from  its  solution,  containing  free  acid,  by  H2S  gas, 
as  a  brown  sulphide,  Bi2S3.  The  compound  is  insoluble  in  ammonium  sulphide 
(separation  from  arsenic,  antimony,  and  tin),  but  dissolves  in  hot  dilute  nitric 
acid  (separation  from  mercury).  The  nitrate,  treated  with  sulphuric  acid  and 
taken  to  S03  fumes,  is  converted  to  the  sulphate  and  dissolves  upon  dilution 
with  water  (lead  remains  insoluble  as  PbS04).  Bismuth  is  precipitated  from 
this  solution  by  addition  of  ammonium  hydroxide,  white  Bi(OH)3  being  formed 
(copper  and  cadmium  dissolve).  If  this  hydroxide  is  dissolved  with  hydro- 
chloric acid  and  then  diluted  with  a  large  volume  of  water,  the  white,  basic 
salt  of  bismuth  oxy chloride,  BiOCl,  is  precipitated.  The  compound  dissolves 
if  sufficient  hydrochloric  acid  is  present.  It  is  insoluble  in  tartaric  acid  (dis- 
tinction from  antimony). 

Reducing  Agents.  Formaldehyde  in  alkaline  solution,  hypophosphorous 
acid,  potassium  or  sodium  stannite,  reduce  bismuth  compounds  to  the  metallic 
state.  For  example,  a  hot  solution  of  sodium  stannite  poured  onto  the  white 
precipitate  of  Bi(OH)3  on  the  filter  will  give  a  black  stain.  The  test  is  very 
delicate  and  enables  the  detection  of  small  amounts  of  the  compound. 

3K2Sn02+2BiCl3+6KOH=2Bi+3K2Sn03+6KCl+3H20. 

Blowpipe  Test.  A  compound  of  bismuth  heated  on  charcoal  with  a 
powdered  mixture  of  carbon,  potassium  iodide  and  sulphur,  will  give  a  scarlet 
incrustation  on  the  charcoal. 

ESTIMATION 

The  determination  of  bismuth  is  required  in  complete  analysis  of  ores  of 
cobalt,  nickel,  copper,  silver,  lead,  and  tin,  in  which  it  is  generally  found 
in  small  quantities.  In  evaluation  of  bismuthite,  bismuth  ochre,  etc.  In  the 
analysis  of  the  minerals  wolfram,  molybdenite.  It  is  determined  in  the  residues 
from  the  refining  of  lead  (the  principal  source  of  bismuth  in  the  United 
States).  In  the  analysis  of  alloys — antifriction  metals,  electric  fuses,  solders, 
stereotype  metals,  certain  amalgams  used  for  silvering  mirrors  (with  or  with- 
out lead  or  tin),  and  in  bismuth  compounds. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  the  substance,  the  following  facts  must  be  kept  in  mind :  nitric 
acid  is  the  best  solvent  of  the  metal.  Although  it  is  soluble  in  hot  sulphuric 
acid,  it  is  only  very  slightly  soluble  in  the  cold  acid.  The  metal  is  practicalry 
insoluble  in  hydrochloric  acid,  but  readily  dissolves  in  nitrohydrochloric  acid. 

1U.  S.  Bureau  of  Standards  Cir.  35. 
62 


BISMUTH  63 

The  hydroxides,  oxides,  and  most  of  the  bismuth  salts  are  readily  soluble  in 
hydrochloric,  nitric,  and  sulphuric  acids. 

Ores  or  Cinders.  One  gram  of  the  finely  pulverized  ore  or  cinder  (or  larger 
amounts  where  the  bismuth  content  is  very  low)  is  treated  in  a  400-cc.  beaker 
with  5  cc.  of  bromine  solution  (Br+KBr+HaO),1  followed  by  the  cautious 
addition  of  about  15  cc.  of  HN03  (sp.gr.  1.42).  When  the  violent  action  has 
ceased,  which  is  apt  to  occur  in  sulphide  ores,  the  mixture  is  taken  to  dryness 
on  the  steam  bath,  10  cc.  of  strong  HC1  and  20  cc.  of  concentrated  H2S04  and 
the  covered  sample  heated  until  S03  fumes  are  freely  evolved.  The  cooled  solu- 
tion is  diluted  with  50  cc.  of  water  and  gently  heated  until  only  a  white  or 
light  gray  residue  remains.  The  solution  is  filtered  and  the  residue  washed 
with  dilute  H2S04  (1  :  10),  to  remove  any  adhering  bismuth.  Silica,  the  greater 
part  of  the  lead  (also  BaS04)  remain  in  the  residue,  whereas  the  bismuth,  to- 
gether with  iron,  alumina,  copper,  antimony,  etc.,  are  in  the  solution.  Details 
of  further  treatment  of  the  solution  to  effect  a  separation  of  bismuth  are 
given  under  "Separations"  and  the  procedures  for  determination  of  bismuth. 

Alloys,  Bearing  Metal,  etc.  One  gram  of  the  borings,  placed  in  a  small 
beaker,  is  dissolved  by  adding  20  cc.  of  concentrated  HC1  and  5  cc.  of  strong 
HN03.  The  alloy  will  usually  dissolve  in  the  cold,  unless  considerable  lead 
is  present,  in  which  case  prolonged  heating  on  the  steam  bath  may  be  neces- 
sary. (A  yellow  or  greenish-yellow  color  at  this  stage  indicates  the  presence  of 
copper.)  Lead  may  now  be  removed  either  as  a  sulphate  by  taking  to  S03  fumes 
with  H2S04  or  by  precipitating  as  a  chloride,  in  the  presence  of  alcohol,  accord- 
ing to  directions  given  under  Separations.  The  bismuth  is  determined  in  the 
filtrate  from  lead  according  to  one  of  the  procedures  given  under  the  quanti- 
tative methods. 

Lead  Bullion,  Refined  Lead.2  Ten  to  twenty-five  grams  of  the  lead, 
hammered  or  rolled  out  into  thin  sheets  and  cut  into  small  pieces,  are  taken 
for  analysis.  The  sample  is  dissolved  by  a  mixture  of  250  cc.  of  water  and 
40  cc.  of  strong  nitric  acid,  in  a  large  covered  beaker,  by  warming  gently,  pref- 
erably on  the  steam  bath.  When  the  lead  has  dissolved,  the  beaker  is  removed 
from  the  heat  and  dilute  ammonia  (1:2)  added  to  the  warm  solution,  very 
cautiously  and  finally  drop  by  drop  until  the  free  acid  is  neutralized  and  the 
liquid  remains  faintly  opalescent,  but  with  no  visible  precipitate.  Now  1  cc. 
of  dilute  HC1  (1  :  3)  is  added.  The  solution  will  clear  for  an  instant  and  then 
a  crystalline  precipitate  of  bismuth  oxychloride  will  form,  if  any  considerable 
amount  of  bismuth  is  present.  The  beaker  is  now  placed  on  the  steam  bath 
for  an  hour,  during  which  time  the  bismuth  oxychloride  will  separate  out, 
together  with  a  small  amount  of  lead  and  with  antimony  if  present  in  appre- 
ciable amounts.  The  further  isolation  and  purification  of  bismuth  is  given 
under  "Separations."  In  brief — antimony  is  removed  by  dissolving  the  pre- 
cipitate in  a  small  amount  of  hot  dilute  HC1  (1  :  3),  precipitating  bismuth, 
traces  of  lead,  and  the  antimony  by  H2S,  dissolving  out  the  antimony  sulphide 
with  warm  ammonium  sulphide,  dissolving  the  Bi2S3  and  PbS  in  HN03  and 
reprecipitation  of  the  bismuth  according  to  the  procedure  given  above.  Bis- 
muth is  now  determined  as  the  oxychloride.  Further  details  of  this  method 
are  given  under  the  gravimetric  procedures  for  bismuth. 

1  Bromine  solution  is  made  by  dissolving  in  water  75  grams  of  KBr,  to  which  are 
added  50  grams  of  liquid  bromine  and  the  mixture  diluted  to  500  cc.  with  water. 

2  Bismuth  in  Refined  Lead.     "Technical  Methods  of  Ore  Analysis."    A.  H.  Low. 


64  BISMUTH 


SEPARATIONS 

The  following  procedures  are  given  in  the  order  that  would  be  followed  in  the 
complete  analysis  of  an  ore,  in  which  all  the  constituents  are  sought.  This  general 
scheme,  however,  is  not  required  for  the  majority  of  bismuth-bearing  samples  com- 
monly met  with  in  the  commercial  laboratory,  direct  precipitations  of  bismuth  fre- 
quently being  possible. 

Separation  of  Bismuth  from  Members  of  Subsequent  Groups,  Fe,  Cr, 
Al,  Mn,  Co,  Ni,  Zn,  Mg,  the  Alkaline  Earths  and  Alkalies,  together  with 
Rare  Elements  of  these  Groups.  The  solution  should  contain  5  to  7  cc.  of 
concentrated  hydrochloric  acid  (sp.gr.  1.19)  for  every  100  cc.  of  the  sample. 
The  elements  of  the  hydrogen  sulphide  group  are  precipitated  by  saturating 
the  solution  with  H2S  (Hg,  Pb,  Bi,  Cu,  Cd,  As,  Sb,  Sn,  Mo,  Se,  Te,  Au,  Pt). 
The  members  of  subsequent  groups  remain  in  solution  and  pass  into  the  nitrate. 

Separation  of  Bismuth  from  Arsenic,  Antimony,  Tin,  Molybdenum, 
Tellurium,  Selenium.  In  presence  of  mercury,  the  soluble  members  of  the 
hydrogen  sulphide  group  are  separated  from  the  insoluble  sulphides  by  digest- 
ing the  precipitate  above  obtained  with  ammonium  sulphide;  in  absence  of 
mercury,  however,  which  is  generally  the  case,  digestion  of  the  sulphides  with 
sodium  hydroxide  and  sodium  sulphide  solution  is  preferred,  the  general  pro- 
cedure being  followed.  Mercury,  lead,  bismuth,  copper,  and  cadmium  remain 
in  the  residue,  whereas  the  other  members  of  the  group  dissolve. 

Separation  of  Bismuth  from  Mercury.  The  insoluble  sulphides,  remain- 
ing from  the  above  treatment  with  ammonium  sulphide  after  being  washed 
free  of  the  soluble  members  of  this  group,  are  placed  in  a  porcelain  dish  and 
boiled  with  dilute  nitric  acid  (sp.gr.  1.2  to  1.3).  The  solution  thus  obtained 
is  filtered,  upon  dilution,  from  the  insoluble  sulphide  of  mercury.  A  little 
of  the  lead  may  remain  as  PbS04,  the  solution  may  contain  lead,  bismuth,  copper, 
and  cadmium. 

Separation  of  Bismuth  from  Lead.  This  is  the  most  important  pro- 
cedure in  the  determination  of.  bismuth  as  the  separation  is  almost  invariably 
necessary,  as  these  elements  commonly  occur  together.  Bismuth  produced 
in  the  United  States  in  1912  was  obtained  entirely  from  the  residues  in  the  re- 
fining of  lead.1 

There  are  two  general  procedures  for  the  separation  of  lead  and  bismuth. 

A.  Precipitation  of  lead  either    as  lead  sulphate  or  as  lead  chloride,  the 
bismuth  remaining  in  solution  under  the  conditions  of  the  precipitation. 

B.  Precipitation  of  bismuth  as  the  oxy chloride  or  subnitrate,  lead  remaining 
hi  solution. 

Precipitating  Lead  as  PbSO4.  This  procedure  is  generally  used  in  the 
process  of  a  complete  analysis  of  an  ore  containing  lead  and  bismuth.  The  nitric 
acid  solution  of  the  sulphides,  obtained  upon  removal  of  the  soluble  group  and 
mercury  by  boiling  the  insoluble  sulphides  with  dilute  nitric  acid,  is  treated 
with  about  10  cc.  of  strong  sulphuric  acid,  and  taken  to  S03  fumes  by  heating. 
The  cooled  sulphate  solution  is  diluted  with  water  and  the  insoluble  lead  sul- 
phate filtered  off  and  washed  with  dilute  sulphuric  acid  solution  (1  :  20). 
Bismuth  passes  into  solution,  together  with  copper  and  cadmium,  if  also  present 
in  the  original  sample. 

1  Mineral  Industry,  1912,  p.  98. 


BISMUTH  65 

Precipitation  of  Lead  as  PbCl2.  This  separation  is  used  in  the  complete 
analysis  of  pig  lead,  the  details  of  the  separation  being  given  under  this 
subject. 

As  the  separation  of  bismuth  from  lead  by  precipitation  of  the  former 
element,  as  the  oxychloride  or  subnitrate  is  incorporated  in  the  quantitative 
methods  following,  it  will  not  be  taken  up  here. 

Separation  of  Bismuth  from  Copper  and  Cadmium.  This  separation  is 
accomplished  by  precipitating  bismuth  as  the  oxychloride  with  hydrochloric  acid, 
or  as  the  carbonate  by  adding  an  excess  of  ammonium  carbonate  to  the  solu- 
tion nearly  neutralized  by  ammonia,  or  as  the  hydroxide  by  adding  an  excess 
of  ammonia.  Details  of  these  procedures  are  given  under  the  gravimetric  methods 
for  determining  bismuth. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION    OF 

BISMUTH 

Determining   Bismuth    by   Precipitation   and   Weighing   as   the 

Basic  Chloride,  BiOCl 

The  determination  depends  upon  the  formation  of  the  insoluble  oxychloride, 
BiOCl,  when  a  hydrochloric  acid  solution  of  bismuth  is  sufficiently  diluted 
with  water,  the  following  reaction  taking  place,  BiCl3+H20  =BiOCl+2HCl. 

The  procedure  is  recommended  for  the  determination  of  bismuth  in  refined 
lead,  bearing  metal,  and  bismuth  alloys.  Copper,  cadmium,  and  lead  do  not 
interfere;  appreciable  amounts  of  antimony  and  tin,  however,  should  be  re- 
moved by  H2S  precipitation  and  subsequent  treatment  with  Na2S,  and  the  resid- 
ual sulphides  dissolved  in  hot  dilute  nitric  acid,  according  to  directions  given 
under  " Separations." 

Properties  of  BiOCl.  Mol.wt.,  259.46;  sp.gr.,  7.71715";  m.p.,  red  heat;  insol. 
in  H20  and  in  H^CJ^Oe,  soluble  in  acids.  Appearance  is  white,  quadratic  crys- 
talline form. 

Procedure.  The  solution  of  bismuth,  freed  from  appreciable  amounts  of 
tin  and  antimony,  is  warmed  gently  and  treated  with  sufficient  ammonia  to 
neutralize  the  greater  part  of  the  free  acid.  At  this  stage  a  precipitate  is  formed 
by  the  addition,  which  dissolves  with  difficulty;  the  last  portion  of  the  dilute 
ammonia  (1  :  2)  is  added  drop  by  drop,  the  solution  is  diluted  to  about  300 
cc.,  and  the  remainder  of  the  free  acid  neutralized  with  dilute  ammonia  added 
cautiously  until  a  faint  opalescence  appears,  but  not  enough  to  form  an  appre- 
ciable precipitate.  One  to  3  cc.  of  dilute  hydrochloric  acid  (1  part  HC1 
sp.gr.  1.19  to  3  parts  H20)  are  now  added,  the  mixture  stirred  and  the  bismuth 
oxychloride  allowed  to  settle  for  an  hour  or  so  on  the  steam  bath,  then  filtered 
hot  by  decanting  off  the  clear  solution  through  a  weighed  Gooch  crucible.  The 
precipitate  is  washed  by  decantation  twice  with  hot  water  and  finally  washed 
into  the  Gooch,  then  dried  at  100°  C.  and  weighed  as  BiOCl. 

BiOClX0.8017=Bi. 

NOTE.  Three  cc.  of  dilute  hydrochloric  acid  (or  1  cc.  cone.  HC1,  sp.gr.  1.19) 
are  sufficient  to  completely  precipitate  1  gram  of  bismuth  from  solution. 


66  BISMUTH 


Determination  of  Bismuth  as  the  Oxide,  Bi2Os 

Preliminary  Considerations.  The  determination  of  bismuth  as  the  oxide 
requires  the  absence  of  hydrochloric  acid  or  sulphuric  acid  from  the  solution 
of  the  element,  since  either  of  these  acids  invariably  contaminates  the  final 
product.  In  presence  of  these  acids,  which  is  frequently  the  case,  determination 
of  bismuth  by  precipitation  as  Bi2S3  or  by  reduction  to  the  metal  and  so  weighing 
is  generally  recommended;  a  brief  outline  of  the  methods  is  given  later; 
a  solution  of  bismuth  free  from  hydrochloric  acid  and  practically  free  of  sul- 
phuric acid  may  be  obtained  by  precipitating  Bi2S3,  together  with  CuS,  CdS, 
and  PbS,  the  amount  of  sulphuric  acid  formed  by  the  reaction  being  negligible. 
Bismuth  should  be  in  a  nitric  acid  solution,  free  from  antimony  and  tin. 

Two  general  conditions  will  be  considered:  1.  Solutions  containing  lead. 
Copper  and  cadmium  may  also  be  present.  2.  Solutions  free  from  lead.  Copper 
and  cadmium  may  be  present. 

1.  Separation  from  Lead,  Copper,   and   Cadmium,   by  Precipitation  as 
Basic  Nitrate. l   Either  the  sulphuric  or  hydrochloric  acid  methods  may  be  employed 
'or  effecting  the  separation  of  lead  by  precipitation.     Furthermore  advantage  may 
be  taken  of  the  fact  that  bismuth  nitrate  is  changed  by  the  action  of  water  into  an 
insoluble  basic  salt,  while  lead,  copper  and  cadmium  do  not  undergo  such  a  trans- 
formation. 

Procedure.  The  bismuth  nitrate  solution  is  evaporated  to  syrupy  con- 
sistency and  hot  water  added  with  constant  stirring  with  a  glass  rod.  The 
solution  is  again  evaporated  to  dryness,  and  the  hot- water  treatment  repeated. 
Four  such  evaporations  are  generally  sufficient  to  convert  the  bismuth  nitrate 
completely  into  the  basic  salt;  when  this  stage  is  reached  the  addition  of  water 
will  fail  to  produce  a  turbidity.  The  solution  is  finally  evaporated  to  dryness 
and,  when  free  from  nitric  acid,  is  extracted  with  cold  ammonium  nitrate  solu- 
tion (l.NH4N03  :  500  H20)  to  dissolve  out  the  lead  and  other  impurities.  After 
allowing  to  stand  some  time  with  frequent  stirring,  the  solution  is  filtered  and 
the  residue  washed  with  ammonium  nitrate  solution,  then  dried. 

Ignition  to  Bismuth  Oxide.  As  much  of  the  precipitate  as  possible  is 
transferred  to  a  weighed  porcelain  crucible,  the  filter  is  burned  and  the  ash 
added  to  the  main  precipitate.  This  is  now  gently  ignited  over  a  Bunsen 
burner.  Too  high  heating  will  cause  the  oxide  to  fuse  and  attack  the  glaze 
of  the  crucible. 

Properties.  Bi(OH)2N03  mol.wt.,  304.03;  sp.gr.,  4.92815°;  decomp.,  260°; 
insol.  in  H20 ;  sol.  in  acids;  hexagonal  plates. 

Bi2O3=woZ.  wt.,  464.0;  sp.gr.,  8.8  to  9.0;  m.p.,  820  to  860°;  insoluble  in  cold 
water  and  in  alkalies,  but  soluble  in  acids;  yellow  tetragonal  crystals. 

Bi203X  0.8965  =Bi. 

2.  Precipitation  of   Bismuth  as  the   Subcarbonate    or  Hydroxide,  Lead 
being  Absent.    Either  of  these  procedures  effects  a  separation  of  bismuth  from 
copper  and  cadmium. 

A.  Procedure.  Precipitation  of  the  Subcarbonate.  The  solution  is 
diluted  to  about  300  cc.  and  dilute  ammonia  added  cautiously  until  a  faint 
turbidity  is  obtained  and  then  an  excess  of  ammonium  carbonate.  The  solution 

1 J.  Lowe,  Jour.  prak.  Chem.,  (1),  74,  344,  1858. 


BISMUTH 


67 


is  heated  to  boiling,  the  precipitate  filtered  off,  washed  with  hot  water,  dried 
and  ignited  according  to  directions  given  in  the  bismuth  subnitrate  method. 
The  residue  is  weighed  as  Bi203. 

B.  Procedure.  Isolation  of  Bismuth  by  Precipitation  as  the  Hydroxide.1 
The  solution  is  taken  to  dryness  and  the  residue  treated  with  5  cc.  of  nitric 
acid  (1  :  4)  and  25  cc.  of  water  added.  The  resulting  solution  is  poured,  with 
constant  stirring,  into  25  cc.  of  concentrated  ammonia  and  50  cc.  of  4% 
hydrogen  peroxide.  Upon  settling  of  the  bismuth  hydroxide,  the  clear  solution 
is  filtered  off  and  the  residue  is  treated  with  more  ammonia  and  peroxide.  It 
is  then  filtered  onto  a  filter  paper,  washed  with  hot,  dilute  ammonium  hydroxide, 
(1  :  8),  followed  by  hot  water  and  washed  free  of  any  adhering  copper  or  cad- 
mium (no  residue  when  a  drop  is  evaporated  on  platinum  foil).  Re-solution 
in  hot  dilute  nitric  acid  and  reprecipitation  may  sometimes  be  necessary  to 
obtain  the  pure  product.  The  hydroxide  may  be  dried,  ignited  and  weighed 
as  Bi203  according  to  directions  already  given  on  page  66. 

Properties.  Bi203-C02-H20,  mol.wt.,  523.02;  sp.gr.,  6.86;  decomp.  by  heat; 
insoluble  in  water,  soluble  in  acids,  insoluble  in  Na2C03;  white  precipitate. 

Bi(OH)3,  mol.wt.,  259.02;  loses  1%  H20  at  150°;  insol.  in  cold  water  and  in 
alkalies;  soluble  in  acids;  white  precipitate. 

Determination  of  Bismuth  as  the  Sulphide,  E^Ss 

The  procedure  is  applicable  to  the  determination  of  bismuth  in  a  hydro- 
chloric or  sulphuric  acid  solution,  freed  from  other  members  of  this  group. 

Procedure.  Bismuth  sulphide 
is  precipitated  by  passing  H2S  into 
the  slightly  acid  solution,  preferably 
under  pressure.  When  the  precipi- 
tation is  complete,  the  bismuth  sul- 
phide, Bi2S3,  is  filtered  off  into  a 
weighed  Gooch  crucible,  the  precipi- 
tate washed  with  H2S  water,  then 
with  alcohol  to  remove  the  water, 
followed  by  carbon  disulphide  to 
dissolve  out  the  precipitated  sul- 
phur, then  alcohol  to  remove  the 
disulphide,  and  finally  with  ether. 
After  drying  for  fifteen  to  twenty 
minutes,  the  residue  is  weighed  as 


Bi2S3.    This    weight    multiplied  by 
0.8122  =Bi. 


FIG.  7.— Purification  of  Carbon  Disulphide. 


NOTE.  The  carbon  disulphide  used  should  be  freshly  distilled.  This  may  be 
accomplished  by  placing  the  carbon  disuiphide  in  a  small  flask  (A,  Fig.  7)  connected 
by  means  of  a  glass  tube  (C)  to  a  second  flask  (B),  cork  stoppers  being  used.  The 
vessels  are  immersed  in  beakers  of  water,  the  container  with  the  reagent  being  placed 
in  hot  water  (60-80°  C.)  and  the  empty  flask  in  cold  water.  The  reagent  quickly  dis- 
tills into  the  empty  flask  in  pure  form. 

Properties  of  Bismuth  Sulphide.  Bi2S3,  mol.wt.,  512.21;  sp.gr.,  7-7.81; 
decomposed  by  heat,  solubility  =0.0000l8g.  per  100  cc.  cold  H20;  soluble  in  nitric 
acid;  brown  rhombic  crystals. 

1  P.  Jannasch,  Zeit.  anorg.  Chem.,  8,  302,  1895. 


68  BISMUTH 

Determination  of  Bismuth  as  the  Metal 

Reduction  with  Potassium  Cyanide.1  Bismuth  precipitated  as  the  car- 
bonate and  ignited  to  the  oxide  according  to  the  procedure  given,  is  fused  in 
a  weighed  porcelain  crucible  with  5  times  its  weight  of  potassium  cyanide  over 
a  low  flame.  The  cooled  melt  is  extracted  with  water,  pouring  the  extracts 
through  a  filter  that  has  been  dried  and  weighed  with  the  crucible.  Bismuth 
is  left  undissolved  as  metallic  bismuth.  After  washing  with  water,  alcohol, 
and  ether,  the  filter,  with  the  metal  and  loosened  pieces  of  porcelain  glaze,  is 
dried  at  100°  C.  together  with  the  crucible.  These  are  then  weighed  and  the 
increased  weight  taken  as  the  amount  of  bismuth  present  in  the  sample. 

Electrolytic  Deposition  of  Bismuth 

With  samples  containing  less  than  0.03  gram  bismuth,  the  metal  may  be 
satisfactorily  deposited  by  electrolysis  of  its  sulphuric  acid  solution,  lead  having 
been  removed  previously  by  sulphuric  acid  by  the  standard  procedure.  The 
solution  contains  about  6  cc.  of  strong  sulphuric  acid  per  100  cc.  This  is 
electrolyzed  with  a  current  of  0.6  to  0.7  ampere  and  about  2.7  to  3  volts 
Further  details  of  this  method  may  be  found  in  "  Technical  Methods  of  Ore 
Analysis,"  by  A.  H.  Low,  page  54,  VII  Edition.  John  Wiley  &  Sons. 

VOLUMETRIC   DETERMINATION   OF  BISMUTH 

Determination  of  Bismuth  by  Precipitation  as  Oxalate  and 
Titration  by  Potassium  Permanganate  2 

Normal  bismuth  oxalate,  produced  by  addition  of  oxalic  acid  to  a  nitric 
acid  solution  of  the  element,  boiled  with  successive  portions  of  water,  is  trans- 
formed to  the  basic  oxalate.  This  may  be  titrated  with  potassium  perman- 
ganate in  presence  of  sulphuric  acid. 

Procedure.  Preparation  of  the  Sample.  One  gram  of  the  finely  ground 
sample  is  treated  with  5  to  10  cc.  of  concentrated  nitric  acid  and  digested  on 
the  steam  bath  and  finally  evaporated  to  dryness,  the  residue  is  taken  up  with 
5  cc.  of  nitric  acid  (sp.gr.  1.42) +25  cc.  of  water,  and  diluted  to  100  cc. 

Precipitation  of  the  Oxalate.  About  5  grams  of  ammonium  oxalate  or 
oxalic  acid  are  added  and  the  liquid  boiled  for  about  five  minutes,  the  pre- 
cipitate allowed  to  settle  and  the  supernatant  solution  filtered  off.  The 
precipitate  is  boiled  twice  with  50-cc.  portions  of  water  and  the  washings  poured 
through  the  same  filter.  If  the  filtrate  still  passes  through  acid,  the  washing 
is  continued  until  the  acid  is  removed  and  the  washing  passing  through  the 
filter  is  neutral.  The  bulk  of  the  basic  oxalate  precipitate  is  placed  in  a  beaker 
and  that  remaining  on  the  filter  paper  is  dissolved  by  adding  2  to  5  cc.  of  hydro- 
chloric acid,  1:1,  the  solution  being  added  to  the  bulk  of  the  precipitate. 

1  Method  by  H.  Rose,  Pogg.  Ann.,  110,  p.  425. 

Vanino  and  Treubert  (Ber..  31  (1898),  1303),  reduce  bismuth  by  adding  formal- 
dehyde to  its  slightly  acid  solution  and  then  making  stiongly  alkaline  with  10% 
NaOH  solution  and  warming.  N.B.  Treadwell  and  Hall,  Anal.  Chem.,  p.  181,  3d  Ed. 

2  The  method  is  rapid  and  is  sufficiently  accurate  lor  commercial  work.     Warwick 
and  Kvle  (C.  N..  75,  3). 

Miiir  and  Robbs,  J.  C.  S.,  41,  1. 


BISMUTH  69 

This  is  now  warmed  until  it  goes  into  solution  and  the  liquid  is  diluted  to  250 
cc.  with  hot  water.  Dilute  ammonia  is  now  added  until  the  free  acid  is 
neutralized ;  the  resulting  precipitate  is  taken  up  with  dilute  sulphuric  acid,  1  :  4, 
added  in  slight  excess.  The  resulting  solution,  warmed  to  70°,  is  titrated  with 
standarcl  potassium  permanganate. 

One  cc.  KMn04  N/10  =0.0104  gram  Bi. 

NOTE.  Lead,  copper,  arsenic,  iron,  zinc,  and  tellurium  do  not  interfere.  Hy- 
drochloric acid  should  not  be  used  to  dissolve  the  sample,  as  it  interferes  with  the 
oxalate  precipitation. 

Cinchonine  Potassium  Iodide,  Colorimetric  Method  * 

This  method  is  applicable  for  the  determination  of  small  amounts  of  bis- 
muth, 0.00003  to  0.00015  gram,  in  ores  and  alloys.  The  procedure  depends 
upon  the  fact  that  bismuth  nitrate  produces  a  crimson  or  orange  color  when  its 
solution  is  added  to  a  solution  of  cinchonine  potassium  iodide,  the  intensity 
of  the  color  depending  upon  the  amount  of  bismuth  in  the  resulting  product. 

Special  Reagents.  Cinchonine  Potassium  Iodide  Solution.  Ten  grams  of 
cinchonine  are  dissolved  by  treating  with  the  least  amount  of  nitric  acid  that 
is  necessary  to  form  a  viscous  mass  and  taking  up  with  about  100  cc.  of  water. 
The  acid  is  added  a  drop  at  a  time,  as  an  excess  must  be  avoided.  Twenty 
grams  of  potassium  iodide  are  dissolved  separately  and  cinchonine  solution  added. 
The  resulting  mixture  is  diluted  with  water  to  1000  cc.  After  allowing  the 
reagent  to  stand  forty-eight  hours,  any  precipitate  formed  is  filtered  off  and 
the  clear  product  is  ready  for  use.  The  reagent  preserved  in  a  glass-stoppered 
bottle  keeps  indefinitely.  It  should  be  filtered  free  of  suspended  matter  before  use. 

Standard  Bismuth  Solution.  One  gram  of  metallic  bismuth  is  dissolved 
in  the  least  amount  of  dilute  nitric  acid  (1:1)  that  is  necessary  to  keep  it  in 
solution  and  diluted  to  1000  cc.,  in  a  graduated  flask.  One  hundred  cc.  of  this 
solution  is  diluted  to  1000  cc.  One  cc.  of  this  diluted  solution  contains  0.0001 
gram  bismuth. 

Procedure.  Isolation  of  Bismuth.  The  solution  is  freed  from  lead  by 
H2S04,  and  from  arsenic,  antimony,  and  tin  by  precipitation  of  the  sulphides 
and  extraction  with  Na2S  solution.  The  residual  sulphides  are  dissolved  in  hot 
dilute  nitric  acid,  according  to  the  standard  methods  of  procedure.  The  free 
nitric  acid  is  nearly  neutralized  by  the  cautious  addition  of  dilute  ammonia, 
the  last  portion  being  added  drop  by  drop,  until  a  faint  cloudiness  is  evident, 
and  then  10  to  15  cc.  of  10%  ammonium  carbonate  are  added  with  constant 
stirring.  The  mixture  is  digested  for  about  three  hours  on  the  steam  bath, 
the  clear  solution  decanted  through  a  small  filter,  the  residue  washed  by  de- 
cantation  once  or  twice  with  hot  water  containing  ammonium  carbonate  and 
then  on  the  filter  twice  with  pure  hot  water. 

Colorimetric  Comparison 

The  residue  of  bismuth  basic  carbonate  is  dissolved  in  the  least  amount  of 
dilute  nitric  acid  necessary  to  effect  solution  and  the  filter  washed  free  of  bis- 
muth with  a  little  water  containing  a  few  drops  of  nitric  acid.  The  solution 
is  made  up  to  a  definite  volume,  50  cc.  or  100  cc.  according  to  the  bulk  of 

1  Method  of  W.  C.  Ferguson. 


70  BISMUTH 

precipitate  dissolved.  Two  small  beakers  placed  side  by  side  may  be  used 
for  the  color  comparison,  a  sheet  of  white  paper  or  tile  being  placed  under  the 
beakers.  Two  50-cc.  Nessler  tubes,  however,  are  preferred.  Three  cc.  of  cin- 
chonine  solution  are  added  to  each  container.  From  a  burette  the  bismuth 
nitrate  sample  is  run  into  one  of  these  containers  in  just  sufficient  quantity  to 
color  the  reagent  a  crimson  or  orange  tint.  The  exact  volume  required  to  do 
this  is  noted  and  the  equivalent  amount  of  sample  used  calculated.  (If  no 
color  is  produced  bismuth  is  absent.)  The  reagent  in  the  adjacent  beaker  or 
Nessler  tube  is  diluted  to  5  to  7  cc.,  and  into  this  is  run,  from  a  burette,  the 
standard  bismuth  nitrate  solution  until  the  color  exactly  matches  the  sample. 
From  the  cc.  of  the  standard  required  the  amount  of  bismuth  in  the  sample 
can  readily  be  calculated. 

Reaction.     3KI+C19H22N2OKI+Bi(N03)3  =  C19H22N2OKIBiI3+3KN03. 

Precautions.  The  sensitiveness  of  the  method  is  lost  if  the  depth  of  color  is  too 
great.  It  is  necessary,  then,  to  add  the  sample  to  the  cinchonine  reagent  in  such 
quantity  only  as  will  produce  a  light  crimson  or  orange  color. 

Solutions  in  the  comparison  tubes  or  beakeis  must  not  be  overdiluted,  since  the 
bismuth  salt  formed  by  the  reaction  of  the  cinchonine  reagent  is  soluble  in  water 
with  the  disappearance  of  color  in  too  dilute  solutions. 

Comparison  must  be  expeditiously  made,  as  a  precipitate  is  apt  to  form  upon 
standing,  and  iodine  will  sometimes  separate. 

The  order  of  addition  must  be  observed;  e.g.,  the  bismuth  solution  is  added  to 
the  cinchonine  reagent,  never  the  reverse. 

Colorimetric  Determination  of  Bismuth.     Bismuth  Iodide 

Method  ! 

Bismuth  iodide  gives  an  intense  yellow,  orange,  or  red  color  to  its  solu- 
tion. The  color  is  not  destroyed  by  S02,  as  is  that  of  free  iodine.  The  intensity 
of  the  color  varies  as  follows: 

1  part  of  bismuth  in    10,000  parts  of  water  produces  an  orange-colored  solution. 
1  part  of  bismuth  in    40,000  parts  of  water  produces  a  light  orange  color. 
1  part  of  bismuth  in  100,000  parts  of  water  produces  a  faint  yellow  color. 

Reagents.  Standard  Bismuth  Solution.  One  gram  of  bismuth  is  dissolved 
in  3  cc.  of  strong  nitric  acid  and  with  2.8  cc.  of  water  and  made  up  to  100  cc. 
with  glycerine.  Glycerine  is  added  to  keep  the  BiI3  in  solution.  Glycerine 
is  not  necessary  for  amounts  of  bismuth  below  0.0075  gram  per  cc. 

Potassium  Iodide  Solution.  Five  grams  of  potassium  iodide  dissolved  in 
5  cc.  of  water  is  diluted  to  100  cc.  with  glycerine. 

Procedure.  The  sample  is  dissolved  with  just  sufficient  nitric  acid  and 
water  necessary  to  cause  solution,  10  cc.  of  glycerine  and  10  cc.  of  potassium  iodide 
solution  added  and  the  sample  diluted  to  50  cc.  Comparison  is  now  made  with 
10  cc.  of  the  standard  bismuth  solution  to  which  has  been  added  10  cc.  of 
potassium  iodide  and  30  cc.  of  water.  It  is  advisable  to  have  the  standard 
stronger  in  bismuth  than  the  sample  and  to  draw  out  the  standard  from  the 
comparison  cylinder  until  the  two  colors  match. 


.  C.  Thresh,  Pharm.  Jour.,  641,  1880. 


BORON 

WILFRED  W.  SCOTT 

(  amorP-  sP-ffr-  3-45?  m-P-  2200°;  b.  p.  sublimes. 

I  cr^sf  .    sp.^r.  2.55  ;  m.p.  2500°  ;  6.p.  3500°  C  ;  oxide,  B2O3 


DETECTION 

Flame  Test.  Boric  acid  is  displaced  from  its  salts  by  nearly  all  acids, 
including  even  carbonic  acid.  Upon  ignition,  however,  it  in  turn  drives  out 
other  acids  which  are  volatile  at  lower  temperatures.  A  powdered  borate, 
previously  calcined,  is  moistened  with  sulphuric  acid  and  a  portion  placed  on 
the  loop  of  a  platinum  wire  is  heated  to  expel  the  sulphuric  acid,1  then  moistened 
with  glycerine  and  placed  in  the  colorless  flame;  a  green  color  will  be  imparted 
to  the  flame.  Copper  salts  should  be  removed  with  H2S  and  barium  as  BaSCX  if 
present,  as  these  also  color  the  flame  green. 

The  flame  test  may  be  conveniently  made  by  treating  the  powdered  sample 
in  a  test-tube  with  sulphuric  acid  and  alcohol  (preferably  methyl  alcohol).  A 
cork  carrying  a  glass  tube  is  inserted  and  the  test-tube  gently  warmed.  The 
escaping  gas  will  burn  with  a  green  flame. 

The  test  may  be  made  by  igniting  the  mixture  of  powder,  alcohol,  and  sul- 
phuric acid  in  an  open  porcelain  dish.  The  green  color  will  be  seen  in  presence 
of  a  borate.  The  test  is  not  as  delicate  as  the  one  with  the  test-tube. 

Borax  Bead.  Na2B407  •  10H2O  fused  in  a  platinum  loop,  swells  to  several 
times  its  original  volume  as  the  water  of  crystallization  is  being  driven  out, 
then  contracts  to  a  clear  molten  bead.  If  the  bead  is  dipped  into  a  weak  solution 
of  cobalt  and  plunged  into  the  flame,  until  it  again  becomes  molten,  the  bead 
upon  cooling  will  be  colored  blue. 

Turmeric  Test.  A  few  drops  of  acetic  acid  are  added  together  with  2 
or  3  drops  of  an  alcoholic  turmeric  solution  to  an  alcoholic  extract  of  the 
sample,  placed  in  a  porcelain  dish.  The  solution  is  diluted  with  water  and  then 
evaporated  to  dryness  on  the  water  bath.  1/1000  milligram  of  boric  acid  will 
produce  a  distinct  color,  2/100  milligram  will  give  a  strong  reddish-brown 
colored  residue,  which  becomes  bluish-black  when  treated  with  a  drop  of  sodium 
hydroxide  solution. 

ESTIMATION 

The  determination  of  boron  is  required  in  the  valuation  of  borax, 
Na2B4(V10H20;  boracite,  4MgB4072MgOMgCl2  ;  borocalcite,  CaB407-6H20; 
hydroboracite;  boronatrocalcite,  etc.,  the  element  being  reported  generally  as 
the  oxide,  B203.  The  determination  is  required  for  obtaining  the  true  value  of 
commercial  boric  acid,  in  the  analysis  of  fluxes  and  certain  pigments.  It  is 
determined  as  a  food-preservative  in  milk,  meat,  canned  goods,  etc.  The  ele 
ment  is  determined  in  certain  alloys  of  nickel,  cobalt,  zinc,  chromium,  tungsten, 
molybdenum  and  in  the  analysis  of  steel. 

1  Silicates  should  be  mixed  with  potassium  fluoride  and  potassium  acid  sulphate, 
KHSO4,  then  held  in  the  flame. 

71 


72  BORON 


Preparation  and  Solution  of  the  Sample 

It  will  be  recalled  that  crystalline  boron  is  scarcely  attacked  by  acids  or 
alkaline  solutions;  the  amorphous  form,  however,  is  soluble  in  concentrated 
nitric  and  sulphuric  acids.  Both  forms  fused  with  potassium  hydroxide  are 
converted  to  potassium  metaborate.  Boric  acid  is  more  readily  soluble  in  pure 
water  than  in  hydrochloric,  nitric,  sulphuric,  or  acetic  acids,  but  still  more  soluble 
in  tartaric  acid  (Herz,  Chem.  Zentr.,  1903,  1,  312).  It  is  soluble  in  alcohol  and 
volatile  oils.  Borax  is  insoluble  in  alcohol.  With  acids  it  becomes  transposed 
to  boric  acid  and  the  sodium  salt  of  the  acid. 

Boric  Oxide  in  Silicates,  Enamel,  etc.  About  0.5  gram  of  the  finely  ground 
material  is  fused  with  five  times  its  weight  of  sodium  carbonate,  the  melt  extracted 
with  water  and  the  extracts,  containing  the  sodium  salt  of  boric  acid,  evap- 
orated to  small  volume.  The  greater  part  of  the  excess  sodium  carbonate 
is  neutralized  with  hydrochloric  acid  and  finally  made  acid  with  acetic  acid 
(litmus  paper  test  =  red).  Boric  oxide  is  now  determined  by  the  distillation 
process  according  to  the  procedure  given  later  in  the  chapter. 

Boronatrocalcite,  Borocalcite,  Boracite,  Calcium  Borate.  Ten  grams  of 
the  powdered  material  is  placed  in  a  flask  with  a  reflux  condenser  and  about  50 
cc.  of  normal  hydrochloric  acid  added  and  the  mixture  boiled  for  half  an  hour. 
The  contents  of  the  flask,  together  with  the  washings,  including  those  of  the 
reflux  condenser  (C02-free  water  being  used),  are  filtered  into  a  500-cc.  flask 
and  made  to  volume  with  C02-free  water.  Fifty  cc.  of  this  solution  is  titrated 
with  half-normal  sodium  hydroxide,  using  paranitrophenol  indicator.  When 
a  yellow  color  appears  the  hydrochloric  acid  has  been  neutralized.  A  second 
50-cc.  portion  is  now  taken  for  analysis  and  the  free  hydrochloric  acid  neutral- 
ized with  sodium  hydroxide,  using  the  amount  of  caustic  required  in  the  trial 
analysis  (this  time  without  an  indicator).  Boric  acid  is  now  determined  by  titra- 
tion  according  to  the  procedure  on  p.  76. 

Borax,  Boric  Acid.  Ten  grams  of  the  material  are  dissolved  in  about 
300  cc.  of  water  (free  from  C02)  and  made  to  500  cc.  in  a  graduated  flask,  with 
pure  water.  One  hundred-cc.  portions  are  taken  for  analysis  and  the  solution 
titrated,  in  presence  of  mannitol  or  glycerol,  according  to  directions  given  under 
the  volumetric  procedures. 

Boric  Acid  in  Mineral  Water.  Water  containing  more  than  0.1  gram 
boric  acid  per  liter,  about  200  cc.  are  evaporated  to  small  volume,  the  precipitated 
salts  are  filtered  off  and  washed.  Boric  acid  passes  into  the  filtrate  and  may  be 
determined  by  the  distillation  method  of  Gooch  given  on  p.  74. 

With  water  containing  traces  of  boric  acid,1  5  liters  or  more  are  evaporated  to 
about  one-tenth  the  original  volume  the  precipitate  filtered  off  and  washed  with 
hot  water.  The  filtrate  is  evaporated  down  to  a  moist  residue.  If  the  residue  is 
small,  it  is  acidified  with  acetic  acid  and  the  boric  acid  determined  by  distillation, 
as  stated  on  p.  74.  If  considerable  residue  is  present,  hydrochloric  acid  is  added 
to  acid  reaction,  and  then  the  mixture  digested  with  absolute  alcohol  in  a  corked 
flask  for  ten  to  fifteen  hours,  with  occasional  shaking.  The  solution  is  filtered,  the 
residue  washed  with  95%  alcohol,  the  filtrate  diluted  with  water,  10  cc.  of  10% 
sodium  hydroxide  solution  added  and  the  alcohol  distilled  off.  A  second  alcoholic 

1  Reference  is  made  to  Treadwell  and  Hall,  Anal.  Chem.,  4th  ed.,  p.  431-432  for  those 
desiring  more  explicit  details  of  this  method. 


BORON  73 

extraction  is  generally  recommended.  The  final  alkaline  solution  is  taken  to 
dryness  and  gently  ignited.  The  residue  is  extracted  with  water,  made  acid  with 
acetic  acid  and  B203  determined  by  distillation. 

Carbonates.  The  material  is  treated  with  sufficient  acid  (M.  0.  indicator) 
to  liberate  all  the  C02  and  react  with  the  combined  alkali  of  boric  and  carbonic 
acid;  it  is  boiled  in  a  flask  with  reflux  condenser  to  expel  C02,  ten  to  fifteen 
minutes,  the  solution  exactly  neutralized  with  sodium  hydroxide,  (M.  0.),  and  the 
liberated  boric  acid  titrated  in  presence  of  glycerol  and  phenolphthalein  as  usual. 

Boric  Acid  in  Milk,  Butter,  Meat  and  Other  Foods 

Milk.1  One  hundred  cc.  of  milk  is  treated  with  1  to  2  grams  of  sodium 
hydroxide,  and  evaporated  to  dryness  in  a  platinum  dish.  The  residue  is 
thoroughly  charred  2  by  gently  heating;  at  this  stage  care  must  be  exercised  or 
loss  of  boric  acid  will  result;  20  cc.  of  water  are  added,  the  sample  heated  and 
hydrochloric  acid  added  drop  by  drop  until  all  but  the  carbon  has  dissolved. 
The  mixture  is  washed  into  a  100-cc.  flask  with  as  little  water  as  possible,  0.5 
gram  calcium  chloride  added,  then  a  few  drops  of  phenolphthalein  indicator, 
then  a  10%  sodium  hydroxide  solution  until  a  slight  permanent  pink  color 
is  obtained  and  finally  25  cc.  of  lime  water.  (All  P205  is  precipitated  as  calcium 
phosphate.)  The  liquid  is  made  to  100  cc.,  mixed  thoroughly,  and  then  filtered 
through  a  dry  filter.  To  50  cc.  of  the  filtrate,  equivalent  to  50  cc.  of  the  milk 
taken,  normal  sulphuric  acid  is  added  until  the  pink  color  disappears,  then 
methyl  orange  indicator  is  added,  followed  by  more  of  the  standard  acid  until 
the  yellow  color  changes  to  a  faint  pink.  Carbon  dioxide  is  expelled  and  the 
liberated  boric  acid  titrated  in  presence  of  glycerine,  according  to  the  procedure 
given  for  evaluation  of  borax  and  boric  acid,  under  "  Volumetric  Determination 
of  Boron." 

Butter.3  Twenty-five  grams  of  butter  are  weighed  out  in  a  beaker  and  25 
cc.  of  a  sugar  sulphuric  acid  mixture  added.  (Mix  =6  grams  sugar  of  milk, 
4  cc.  normal  sulphuric  acid  per  100  cc.  of  solution.)  The  beaker  is  placed  in  the 
oven  (100°  C.)  until  the  fat  is  melted  and  the  mixture  is  thoroughly  stirred. 
When  the  aqueous  solution  has  settled,  20  cc.  are  pipetted  out,  phenolphthalein 
added,  the  solution  brought  to  boiling  and  half-normal  sodium  hydroxide  added 
until  a  faint  pink  color  is  obtained.  Ten  cc.  of  neutral  glycerine  are  added 
and  the  titration  carried  on  until  a  permanent  pink  color  appears.  The  dif- 
ference between  the  two  titrations  multiplied  by  the  factor  for  equivalent  boric 
acid  gives  the  weight  of  boric  acid  in  the  portion  taken. 

The  determination  is  not  affected  by  the  phosphoric  or  butyric  acid  or  by 
the  sugar  of  milk  in  the  butter. 

Meat.4  Ten  grams  of  the  chopped  meat  are  mixed  in  a  mortar  with  40  to 
80  grams  of  anhydrous  sodium  sulphate,  and  dried  in  the  water  oven.  The 
mass  is  powdered,  then  placed  in  a  flask  and  100  cc.  of  methyl  alcohol  added 
and  allowed  to  stand  for  about  twelve  hours.  The  alcohol  is  distilled  into  a 
flask  and  saved.  Fifty  cc.  more  of  alcohol  are  added  to  the  residue  and  this 
again  distilled  into  the  first  distillate.  The  distillates  are  made  up  to  150  cc.,  a 

1  R.  T.  Thomson,  Glasgow  City  Anal.  Soc.  Repts.,  1895,  p.  3. 

2  The  milk  residue  thoroughly  charred  will  give  a  colorless  solution  upon  extraction. 

3  H.  Droop  Richmond  and  J.  B.  P.  Harrison,  Analyst,  27,  197. 

4  C.  Fresenius  and  G.  Popp,  Chem.  Centr.,  1897,  2,  69. 


74 


BORON 


50-cc.  portion  diluted  with  50  cc.  of  water  and  50  cc.  of  neutral  glycerine  added 
with  phenolphthalein  indicator,  and  the  boric  acid  titrated  with  twentieth- 
normal  sodium  hydroxide. 

One  cc.  N/20  NaOH  =0.0031  gram  boric  acid,  H3B03. 

Boric  acid  in  canned  goods,  sauces,  cereals,  etc.,  may  be  determined  by 
evaporation  of  the  substance  with  sodium  hydroxide  and  incineration  as  in 
case  of  milk.  The  sodium  hydroxide  is  neutralized  and  boric  acid  titrated  as 
usual. 

GRAVIMETRIC   DETERMINATION   OF  BORON 

The  solubility  of  boron  compounds  prevents  complete  precipitation  by  any 
of  the  known  reagents,  hence  most  of  the  gravimetric  methods  are  indirect. 

Distillation  as  Methyl  Borate  and  Fixation  by  Lime  1 

This  excellent  method,  originally  worked  out  by  F.  A.  Gooch, l  and  later  modi- 
fied by  Gooch  and  Jones,2  depends  upon  the  fact  that  the  borates  of  alkaline 
earths  and  alkalies  give  up  their  boron  in  the  form  of  the  volatile  methyl  borate 
(b.p.,  65°  C.),  when  they  are  distilled  with  absolute  methyl  alcohol  (acetone- 
free).  The  methyl  borate  passed  over  lime  in  presence  of  water  is  completely 

saponified,  the  liberated  boric  acid 
combining  with  the  lime  to  form 
calcium  borate,  which  mav  be  dried, 
ignited,  and  weighed.  The  increase 
of  the  weight  of  the  lime  represents 
the  B203  in  the  sample. 

2B(OCH3)3+CaO+6H20 

=  6CH3OH+Ca(B02)2+3H20. 

Procedure.  About  1  gram  of  pure 
calcium  oxide  is  ignited  to  constant 
weight  over  a  blast  lamp  and  then 
transferred  to  the  dry,  Erlenmeyer 
receiving  flask  (Fig.  8).  The  crucible 
in  which  the  lime  was  heated  and 
weighed  is  set  aside  in  a  desiccator  for 
later  use. 

0.2  gram  or  less  of  the  alkali  borates, 
obtained  in  solution  by  a  procedure 
given  under  "Preparation  of  the  Sam- 
ple," is  treated  with  a  few  drops  of  litmus 
(or  lacmoid),  solution  and  the  free  al- 
kali neutralized  with  dilute  HC1  solution 
Fia.  8.— Distillation  of  Methyl  Borate.  added  drop  by  drop.  A  drop  of  dilute 

sodium  hydroxide  solution  is  added  and 
then  a  few  drops  of  acetic  acid.  The  slightly  acid  solution  is  transferred  to  the 

'Proc.  Am.  Acad.    of    Arts    and    Sciences,   22,    1G7-176   (1886).    Anal.    Chem., 
Treadwell-Hall,  Vol.  2. 
2  See  note  on  u.  75. 


BORON  75 

pipette-shaped  retort  R,  Fig.  <°,  by  means  of  the  attached  funnel  F,  washing 
out  the  beaker  and  funnel  with  three  2-  to  3-cc.  portions  of  water.  The  stop- 
cock of  the  funnel  is  closed,  the  apparatus  is  connected  up  as  shown  in  the  illus- 
tration^the  paraffine  bath,  heated  to  not  over  140°  C.,  placed  in  position  and 
the  liquid  in  the  retort  distilled  into  the  receiver  containing  the  known  amount 
of  lime.  When  all  the  liquid  has  distilled  over,  the  paraffine  bath  is  lowered, 
the  retort  allowed  to  cool  for  a  few  minutes,  10  cc.  of  methyl  alcohol  (acetone- 
free)  added  to  the  residue  in  R  and  the  contents  again  distilled  by  replacing 
the  paraffine  bath.  The  process  is  repeated  three  times  with  methyl  alcohol. 
The  contents  of  the  retort  (which  are  now  alkaline),  are  made  distinctly  acid 
by  addition  of  acetic  acid,  and  three  more  distillations  made  with  100-cc.  portions 
of  methyl  alcohol,  as  before.  The  paraffine  bath  is  now  removed,  the  receiving 
flask  is  stoppered,  the  contents  thoroughly  mixed  by  shaking,  and  set  aside  for 
an  hour  or  more  for  complete  saponification  of  the  methyl  borate.  The  con- 
tents are  now  poured  into  a  large  platinum  dish  and  evaporated  on  the  water 
bath  at  a  temperature  below  the  boiling-point  of  the  alcohol.  (Loss  of  boric 
acid  will  occur  if  the  alcohol  boils.)  The  adhering  lime  in  the  receiving  flask 
is  dissolved  by  wetting  its  entire  surface  with  a  few  drops  of  dilute  nitric  acid 
(the  flask  being  inclined  and  revolved  to  flow  the  acid  over  its  sides).  The 
contents  are  transferred  to  the  dish  with  a  little  water  and  the  evaporation 
repeated.  No  loss  of  boric  acid  will  take  place  at  this  stage,  the  alcohol  having 
been  removed  during  the  first  evaporation.  The  residue  is  gently  heated  to 
destroy  any  calcium  acetate  that  may  have  formed,  the  cooled  borate  and 
lime  are  taken  up  with  a  little  water  and  transferred  to  the  crucible  in  which 
the  lime  was  heated  and  weighed.  The  material  clinging  to  the  dish  is  dis- 
solved with  a  little  nitric  acid  (or  acetic  acid),  and  washed  into  the  crucible. 
The  contents  of  the  crucible  are  evaporated  to  dryness  on  the  water  bath,  then 
heated  very  gently  over  a  flame  (the  crucible  being  covered)  and  finally  more 
strongly.  The  heating  is  continued  until  a  constant  weight  is  obtained.  The 
increase  of  weight  of  the  lime  represents  the  amount  of  B203  in  the  sample. 

NOTES.  Gopch  and  Jones  worked  out  a  procedure  which  utilizes  sodium  tung- 
state  as  a  retainer  of  the  methyl  borate,  in  place  of  the  lime.  This  substance  is 
definite  in  weight,  not  hydroscopic,  soluble  in  water,  and  recoverable  in  its  original 
weight  after  evaporation  and  ignition.  "  Methods  in  Chem.  Anal.,"  p.  204,  1st  Ed. 
by  tf.  A.  Gooch,  John  Wiley  &  Sons,  Publishers. 

The  receiving  flask  has  a  cork  stopper  with  a  hole  to  accommodate  the  tube  of 
the  condenser  and  a  slit  to  permit  the  escape  of  air  from  the  flask. 

Gooch  recommends  cooling  of  the  receiving  flask. 


76  BORON 


VOLUMETRIC   DETERMINATION   OF  BORON 

Titration  of  Boric  Acid  in  Presence  of  Mannitol  or  Qlycerol 
Evaluation  of  Borax 

The  method  takes  advantage  of  the  fact  that  boric  acid  reacts  neutral  to 
methyl  orange  (or  paranitrophenol),  but  is  acid  to  phenolphthalein,  and  may 
be  quantitatively  titrated  in  the  presence  of  mannitol  or  of  glycerol,  which 
prevent  the  hydrolization  of  sodium  borate.  If  insufficient  mannitol  or  glycerol 
are  present  the  color  change  takes  place  too  soon,  the  color  fading  upon  adding 
more  of  these  substances.  The  end-point  is  reached  when  the  further  addition 
of  these  reagents  produces  no  fading  of  the  color.  In  the  procedure,  the  alkali 
is  neutralized  in  presence  of  methyl  orange  (or  paranitrophenol),  and  the  liberated 
boric  acid  is  now  titrated. 

Reactions.     Na2B407+2HCl+5H20  =2NaCl+4H3B03 
H3B03+NaOH  =NaB02+2H20. 

Procedure.  One  hundred  cc.  of  the  solution  containing  the  borax,  pre- 
pared according  to  directions  under  " Preparation  and  Solution  of  the  Sample," 
equivalent  to  2  grams  of  the  substance,  is  taken  for  analysis. 

A.  Titration   of   Combined   or   Free   Alkali.    Methyl  orange  indicator  is 
added  and  the  solution  is  titrated  with  normal  or  half-normal  sulphuric  acid 
until  the  yellow  color  is  replaced  by  an  orange  red.     (With  paranitrophenol  the 
solution  becomes  colorless.)     From  this  titration  the  combined  alkali,  together 
with  any  free  alkali,  is  calculated.     If  free  alkali  is  known  to  be  absent  (see 
note),  the  amount  of  borax  may  be  calculated. 

One  cc.  N.  H2S04  =0.031  gram  Na20,  or  =0.1911  gram  Na2B407 •  10H20, 
or  =0.101  gram  Na2B407. 

B.  Titration  of  Boric  Acid.    The  liberated  boric  acid  may  now  be  titrated 
with  caustic.    This  may  be  accomplished  either  on  the  above  portion  or  on  a 
fresh  100-cc.  portion  (free  from  methyl  orange  indicator),  to  which  the  amount 
of  acid,  required  to  neutralize  the  alkali,  has  been  added.     Fifty  cc.  of  neutral 
glycerol  or  1  gram  of  mannitol  are  added,  followed  by  phenolphthalein  indicator. 
Normal  or  half-normal  sodium  hydroxide  is  added  from  a  burette  until  a  change 
of  color  takes  place.    If  methyl  orange  is  present,  the  color,  first  becoming  yellow, 
changes  to  an  orange  red.     In  absence  of  methyl  orange  the  characteristic 
lavender  or  purplish  pink  of  alkali  phenolphthalein  is  obtained.    More  glycerol 
or  mannitol  is  now  added  and  if  the  color  fades  the  titration  is  continued  until 
the  addition  of  these  reagents  no  longer  produces  this  fading  of  the  end-point, 
From  this  titration  boric  acid  is  calculated  and  the  equivalent  borax  determined. 

One  cc.  N.  NaOH  =0.062  gram  H3B03,  equivalent  to  0.0505  Na2B407,  or 
0.0955  Na2B407-10H20. 

Factors.    Na20  to  Na2B407  =3.2581,  reciprocal  =0.3069. 

Na20  to  Na2B407-10H20  =6.1638,  recip.  =0.1622. 

Na20  to  Na2C03  =  1.7097,  recip.  =0.5849. 

Na20  to  Na2C03-10H20  =4.6155,  recip.  =0.2167. 

NOTES.  In  borax  (free  from  excess  B2O3  or  Na^O),  the  acid  titration  is  half  the 
subsequent  alkali  titration  (factor,  acid  to  borax  =  0.1911,  alkali  to  borax  =0.0955). 


BORON  77 

If  the  acid  titration  exceeds  this  proportion,  alkali  other  than  that  combined  with 
boric  acid  is  indicated;  if  the  alkali  titration  is  greater  than  twice  the  acid  titration 
free  boric  acid  is  indicated. 

The  glycerol  should  be  made  neutral  with  N/10  NaOH  before  use,  in  case  it  con- 
tains free  fatty  acids. 

Mannitol  is  a  solid  and  has  some  advantages  over  glycerol;"  it  gives  a  sharper 
end-point,  is  less  apt  to  contain,  free  acids  and  does  not  appreciably  alter  the  bulk 
of  the  solution  to  which  it  is  added.  (L.  C.  Jones,  C.  N.,  80,  65,  1899). 

N.B.  Paper  on  use  of  mannitol  and  glycerol  in  determining  boric  acid,  by  R. 
T.  Thomson,  J.  S.  C.  I.,  12,  432. 

Example.  By  actual  test  2  grams  Na2B4(V10H2O  required  10.66  cc  N  H2SO4  = 
10.66X0.1911=2.037  gram  Na2B4O7-10H2O.  The  liberated  H3BO3  required  2139 
cc.  of  N.  NaOH  =  21. 39X0.0955  =  2.043  gram  Na2B4O7-10H2O.  The  borax  had  lost 
a  small  amount  of  water  of  crystallization,  hence  the  high  results  when  calculated  to 
Na2B407-10H20. 

EVALUATION   OF  BORIC  ACID 

One  hundred  cc.  of  the  solution,  prepared  as  directed  under  " Preparation 
of  the  Sample,"  equivalent  to  2  grams  of  the  original  material,  is  treated  with 
50  cc.  of  glycerol  or  1  gram  of  mannitol,  and  the  acid  titrated  with  standard 
caustic,  in  presence  of  phenolphthalein  indicator  according  to  the  procedure 
given  in  B,  under  "Evaluation  of  Borax." 

One  cc.  normal  acid  contains  0.062  gram  H3B03,  hence  the  cc.  of  caustic 
required  multiplied  by  0.062  =  grams  boric  acid. 

Examples.  Two  grams  H3B03  by  actual  test  required  32.1  cc.  N.  NaOH 
=32.1X.062=1.99  grams  H3B03. 

Detection  of  Minute  Amounts  of  Boron. 

Robin's  Test  for  Boron.  To  a  few  drops  of  the  aqueous  solution  under  examination 
(slightly  acidified  with  HC1)  are  added  two  drops  of  a  tincture  of  mimosa  flowers,  and 
the  mixture  evaporated  to  dryness  on  the  water  bath.  The  residue  is  treated  with 
dilute  ammonia  water,  whereupon  in  presence  of  boric  acid,  a  rose  pink  to  blood  red 
color  develops,  according  to  the  amount  present.  L.  Robin  claims  that  as  little  as 
0.0001  milligram  may  be  detected  in  presence  of  nitrates,  chlorides,  iodides,  or  calcium 
sulphate.  Organic  acids  and  sodium  phosphate  interfere.  The  reagent  is  prepared  by 
extracting  the" mimosa  flowers  with  ethyl  alcohol.  The  extract  is  protected  from  the 
light. 


BROMINE 

WILFRED  W.  SCOTT 

Br,  at.wt.  79.92;  sp.gr.  3.1883°;    m.p.  —7.3°;  b.p.  58.7°  C.;  acids,  HBr, 

HBrO,  HBrO3 

DETECTION 

Silver  Nitrate  solution  precipitates  silver  bromide,  AgBr,  light  yellow, 
from  solutions  containing  the  bromine  anion.  The  precipitate  is  insoluble 
in  dilute  nitric  acid,  but  dissolves  with  difficulty  in  ammonium  hydroxide 
and  is  practically  insoluble  in  ammonium  carbonate  solution  (distinction  from 
AgCl). 

Carbon  Disulphide  or  Carbon  Tetrachloride  shaken  with  free  bromine 
solution,  or  with  a  bromide  to  which  a  little  chlorine  water  has  been  added, 
(a  large  excess  of  chlorine  must  be  avoided,  as  this  forms  BrCl  compound),  will 
absorb  the  bromine  and  become  a  reddish-yellow  color,  or  if  much  bromine 
is  present,  a  brown  to  brownish-black.  In  the  latter  case  a  smaller  sample 
should  be  taken  to  distinguish  it  from  iodine. 

Bromates  are  first  reduced  by  a  suitable  reducing  agent  such  as  cold  oxalic 
acid,  sodium  nitrite,  hydrochloric  acid,  etc.,  and  the  liberated  bromine  tested 
as  directed  above.  Silver  nitrate  added  to  bromates  in  solution  precipitates 
AgBr03,  which  is  decomposed  by  hydrochloric  acid  to  bromine  gas. 

Barium  Chloride  precipitates  Ba(Br03)2,  which  is  reduced  readily  to  bromine 
as  directed  above. 

Magenta  Test  for  Bromine.1  The  test  reagent  is  made  by  adding  10  cc. 
of  0.1%  solution  of  magenta  to  100  cc.  of  5%  solution  of  sulphurous  acid  and 
allowing  to  stand  until  colorless.  This  is  the  stock  solution.  Twenty-five  cc. 
of  this  reagent  is  mixed  with  25  cc.  of  glacial  acetic  acid  and  1  cc.  of  sulphuric 
acid.  Five  cc.  of  this  is-  used  in  the  test. 

Test.  Five  cc.  of  the  magenta  reagent  is  mixed  with  1  cc.  of  the  solution 
tested.  Chlorine  produces  a  yellow  color.  Bromine  gives  a  reddish-violet 
coloration.  The  colored  compound  in  each  case  may  be  taken  up  with  chloro- 
form or  carbon  tetrachloride  and  a  colorimetric  comparison  made  with  a 
standard. 

In  halogen  mixes,  iodine  is  first  eliminated  by  heating  with  an  iron  per 
salt.  Bromine  is  now  liberated  by  adding  sulphuric  acid  and  potassium  chromate. 
A  glass  rod  with  a  pendant  drop  of  sodium  hydroxide  is  held  in  the  vapor  to 
absorb  bromine,  and  the  drop  then  tested  with  the  magenta  reagent.  After 
iodine  and  bromine  are  eliminated,  chlorine  may  be  tested  by  heating  the  sub- 
stance with  potassium  permanganate,  which  liberates  this  halogen. 

1G.  Deniges  and  L.  Chelle.  Ann.  Chim.  anal.,  1913,  18,  11-15;  The  Analyst, 
1913,  119. 

78 


BROMINE  79 

ESTIMATION 

Bromine  never  occurs  free  in  nature.  It  is  found  chiefly  combined  with 
the  alkalies  and  the  alkaline  earths,  hence  occurs  in  many  saline  springs  and 
is  a  by-product  of  the  salt  industry.  It  is  found  in  silician  zinc  ores,  Chili 
saltpeter,  in  sea  water  (probably  as  MgBr2),  in  marine  plants.  Traces  occur  in 
coal,  hence  in  gas  liquors. 

The  substance  is  used  in  metallurgy,  the  arts,  and  medicine.  It  is  a  valu- 
able oxidizing  agent  for  the  laboratory. 

Preparation  and  Solution  of  the  Sample 

The  following  facts  regarding  solubility  should  be  remembered:  The  ele- 
ment bromine  is  very  soluble  in  alcohol,  ether,  chloroform,  carbon  disulphide, 
carbon  tetrachloride,  concentrated  hydrochloric  acid  and  in  potassium  bromide 
solution.  One  hundred  cc.  of  water  at  0°  C.  is  saturated  with  4.17  grams  of 
bromine,  and  at  50°  C.  with  3.49  grams.  The  presence  of  a  number  of  salts 
increases  its  solubility  in  water,  e.g.,  BaCl2,  SrCl2,  etc. 

NOTE.  The  element  is  a  dark,  brownish-red,  volatile  liquid,  giving  off  a  dark  reddish 
vapor  with  suffocating  odor,  irritating  the  mucous  membrane  (antidote  dil.  NH4OH, 
ether),  very  corrosive.  Acts  violently  on  hydrogen,  sulphur,  phosphorus,  arsenic, 
antimony,  tin,  the  heavy  metals,  and  on  potassium,  but  has  no  action  on  sodium, 
even  at  200°  C.  Bleaches  indigo,  litmus,  and  most  organic  coloring  matter.  It  is  a 
strong  oxidizing  agent.  Bromine  displaces  iodine  from  its  salts,  but  is  displaced  by 
chlorine  from  its  combinations. 

Bromides  are  soluble  in  water,  with  the  exception  of  silver,  mercury,  lead, 
and  cuprous  bromides. 

Bromates  are  soluble  in  water  with  the  exception  of  barium  and  silver  bro- 
mates  and  some  basic  bromates. 

Decomposition  of  Organic  Matter  for  Determination  of  Bromine.  The 
substance  is  decomposed  with  nitric  acid  in  presence  of  silver  nitrate  in  a  bomb 
combustion  tube  by  the  Carius  method  described  in  the  chapter  on  Chlorine, 
under  "  Preparation  and  Solution  of  the  Sample "  The  residue,  containing 
the  halides,  is  dissolved  in  warm  ammonia  water,  and  filtered,  as  stated.  The 
filtrate  and  washings  are  acidified  with  nitric  acid,  heated  to  -boiling  and  the 
silver  bromide  settled  in  the  dark,  then  filtered  through  a  weighed  Gooch  cru- 
cible, the  washed  precipitate  dried  at  130°  C.  and  weighed  as  AgBr. 

In  presence  of  two  or  three  halogens  the  lime  method  is  recommended,  as 
given  in  the  chapter  on  chlorine,  page  122. 

Salts  of  Bromine.  The  ready  solubility  of  bromides  and  bromates  has  been 
mentioned.  A  water  extract  is  generally  sufficient.  Insoluble  salts  are  decom- 
posed by  acidifying  with  dilute  sulphuric  acid  and  adding  metallic  zinc.  The 
filtrate  contains  the  halogens. 

SEPARATIONS 

Separation  of  Bromine  from  the  Heavy  Metals.  Bromides  of  the  heavy 
metals  are  transposed  by  boiling  with  sodium  carbonate,  the  metals  being  pre- 
cipitated as  carbonates  and  sodium  bromide  remaining  in  solution. 

Separation  of  Bromine  from  Silver  (AgBr)  and  from  Cyanides  (AgCN). 
The  silver  salts  are  heated  to  fusion.  The  mass  is  now  treated  with  an  excess 


80  BROMINE 

of  zinc  and  sulphuric  acid,  the  metallic  silver  and  the  paracyanogen  filtered 
off  and  the  bromine  determined  in  the  filtrate. 

Separation  of  Bromine  from  Chlorine  or  from  Iodine.  Details  of  the 
procedure  for  determining  the  halogens  in  presence  of  one  another  is  given  in 
the  chapter  on  Chlorine,  page  130.  Free  bromine  is  liberated  when  the  solu- 
tion of  its  salt  is  treated  with  chlorine. 

Separation  of  Bromine  from  Iodine.1  The  neutral  solution  containing 
the  bromide  and  iodide  is  diluted  to  about  700  cc.  and  2  to  3  cc.  of  dilute  sul- 
phuric acid,  1  :  1,  added,  together  with  about  10  cc.  of  10%  sodium  nitrite, 
NaN(>2,  solution.  (Nitrous  acid  gas  may  be  passed  through  the  solution  in 
place  of  adding  sodium  nitrite,  if  desired.)  2  The  solution  containing  the  halides 
is  boiled  until  colorless  and  about  twenty  minutes  longer,  keeping  the  volume 
of  solution  above  600  cc.  0.5  gram  KI  may  be  decomposed  and  the  iodine 
expelled  from  the  bromide  in  half  an  hour.  The  bromine  is  precipitated  from  the 
residue  remaining  in  the  flask  by  addition  of  an  excess  of  silver  nitrate  and 
determined  as  silver  bromide. 

The  procedure  for  determining  iodine  is  given  in  the  chapter  on  this  subject. 


GRAVIMETRIC   METHODS 
Precipitation  as  Silver  Bromide 

The  general  directions  for  determination  of  hydrochloric  acid  and  chlorides 
apply  for  determining  hydrobromic  acid  and  bromides. 

I.  Hydrobromic  Acid  and  Bromides  of  the  Alkalies  and  Alkaline  Earths. 
Procedure.    The  bromide  in  cold  solution  is  made  slightly  acid  with  nitric 

acid  and  then  silver  nitrate  added  slowly  with  constant  stirring  until  a  slight 
excess  is  present.  The  mixture  is  now  heated  to  boiling  and  the  precipitate 
settled  in  the  dark,  then  filtered  through  a  weighed  Gooch  crucible,  and  washed 
with  water  containing  a  little  nitric  acid  and  finally  with  pure  water  to  remove 
the  nitric  acid.  After  ignition  the  silver  bromide  is  cooled  and  weighed  as  AgBr. 

AgBrX0.4256=Br,  or  X0.6337=KBr. 

II.  Heavy  Metals  Present. 

If  heavy  metals  are  present  it  is  not  always  possible  to  precipitate  silver 
bromide  directly.  The  heavy  metals  may  be  removed  by  precipitation  with 
ammonia,  sodium  hydroxide  or  carbonate  and  the  bromide  then  determined 
in  the  filtrate  as  usual. 

VOLUMETRIC   METHODS 

Free  hydrobromic  acid  may  be  titrated  with  standard  alkali  exactly  as  is 
described  for  the  determination  of  hydrochloric  acid  in  the  chapter  on  Acids. 
One  cc.  normal  caustic  solution  is  equivalent  to  0.08093  gram  HBr. 

1 F.  A.  Gooch  and  J.  R.  Ensign.  Am.  Jour.  Sci.,  (3),  xl,  145. 

2  Nitrous  acid  gas  is  generated  by  dropping  dilute  H2SO4,  by  means  of  a  separatory 
funnel  onto  sodium  nitrite  in  a  flask! 


BROMINE  81 

Determination  of  Free  Bromine.    Potassium  Iodide  Method 

The  method  depends  upon  the  reaction  KI-f-Br=KBr+I. 

Procedure.  A  measured  amount  of  the  sample  is  added  to  an  excess  of 
potassium  iodide,  in  a  glass-stoppered  bottle,  holding  the  point  of  the  delivering 
burette  just  above  the  potassium  iodide  solution.  The  stoppered  bottle  is 
then  well  shaken,  and  the  liberated  iodine  titrated  with  standard  thiosulphate 
solution. 

One  cc.  of  N/10  thiosulphate,  Na2S203  =0.007992  gram  Br. 

Determination  of  Bromine  in  Soluble  Bromides.    Liberation  of 
Bromine  by  Addition  of  Free  Chlorine 

When  chlorine  is  added  to  a  colorless  solution  of  a  soluble  bromide,  bromine 
is  liberated,  coloring  the  solution  yellow.  At  boiling  temperature  the  bromine  is 
volatilized,  the  liquid  becoming  again  colorless.  When  the  bromide  is  completely 
decomposed  and  bromine  expelled,  further  addition  of  chlorine  produces  no  color 
reaction.  KBr+Cl  =KCl+Br. 

Procedure.  The  solution  containing  the  bromide  is  heated  to  boiling  and 
standard  chlorine  water  added  from  a  burette  (protected  from  the  light  by 
being  covered  with  black  paper),  the  tip  of  the  burette  being  held  just  above 
the  surface  of  the  hot  bromide  solution  to  prevent  loss  of  chlorine.  The  reagent 
is  added  in  small  portions  until  finally  no  yellow  coloration  is  produced.  From 
the  value  per  cc.  of  the  chlorine  reagent  the  bromine  content  is  readily  calculated. 

Standard  Chlorine  Water.  The  reagent  is  made  by  diluting  100  cc.  of 
water  saturated  with  chlorine  to  500  cc.  This  solution  is  standardized  against 
a  known  amount  of  pure  potassium  bromide  (dried  at  170°  C.),  the  same 
amount  of  bromide  being  taken  as  is  supposed  to  be  present  in  the  solution 
examined.  The  value  per  cc.  of  the  reagent  is  thus  established. 

Silver-=Thiocyanate»Ferric  Alum  Method.    (Volhard) 

The  procedure  is  the  same  as  that  used  for  the  determination  of  chlorine. 
The  bromide  solution  is  treated  with  an  excess  of  tenth-normal  silver  nitrate 
solution,  and  the  excess  of  this  reagent  determined  by  titration  with  ammonium 
thiocyanate,  using  ferric  alum  indicator.  One  cc.  of  the  thiocyanate  should  be 
equivalent  to  1  cc.  of  silver  nitrate  solution.  The  formation  of  the  red  ferric 
thiocyanate  indicates  the  completed  reaction.  (Consult  the  procedure  in  the 
chapter  on  Chlorine,  page  125.) 

One  cc.  of  N/10  AgN03  =0.007992  gram  Br. 

Determination  of  Traces  of  Bromine 

By  means  of  the  magenta  reagent,  described  under  "Detection,"  small 
amounts  of  bromine  may  be  determined  colorimetrically. 

To  5  cc.  of  the  solution  is  added  0.2  cc.  of  strong  hydrochloric  acid,  1  cc. 
of  concentrated  sulphuric  acid,  1  cc.  of  the  stock  magenta  reagent  and  0.2  cc, 
of  a  10%  solution  of  potassium  chromate,  shaking  the  mixture  with  additior 


82 


BROMINE 


of  each  reagent,  and  without  cooling,  1  cc.  of  chloroform  is  added.     Comparison 
is  made  with  a  standard  sample  containing  a  known  amount  of  bromide.1 

NOTE.     A  solution  containing  0.001  gram  bromine  per  liter  has  a  violet  to  reddish- 
violet  color. 


Determination  of  Bromates  by  Reduction  with    Arsenous  Acid 
and  Titration  of  the  Excess 2 

Bromic  acid  may  be  reduced  by  arsenous  acid  in  accordance  with  the  reac- 
tion 3H3As03+HBr03=3H3As04+HBr.  In  the  process  a  considerable  excess 
of  arsenous  acid  is  added,  the  excess  titrated  with  iodine  and  the  bromate 
calculated. 

Procedure.  The  sample  of  bromate,  dissolved  in  water,  is  treated  with  a 
considerable  excess  of  N/10  arsenous  oxide  (dissolved  in  alkali  hydrogen  car- 
bonate) reagent,  the  solution  then  acidified  with  3  cc.  to  7  cc.  of  dilute  sul- 
phuric acid  (1:1)  and  diluted  to  a  volume  not  exceeding  200  cc.  After  boiling 
for  ten  minutes,  the  free  acid  is  neutralized  with  alkali  hydrogen  carbonate 
(NaHCOs  or  KHC03)  and  the  excess  of  arsenite  titrated  with  N/10  iodine. 

Let  x  cc.  equal  the  difference  between  the  two  titrations  with  N/10  iodine  (i.e. 
of  total  arsenite  minus  excess  arsenite)  and  w  equal  the  weight  of  bromate  de- 
sired, then 


w 


x  cc.Xmol.  wt.  RBrO3 
6X10X1000 


milligrams. 


ANALYSIS  OF  CRUDE  POTASSIUM  BROMIDE  AND 
COMMERCIAL  BROMINE 

Determination  of  Chlorine,  Combined  or  Free 

This  is  the  principal  impurity  present  and  its  estimation  is  concerned  here. 
Andrews'  modification  of  Bugarszk's  method  3  is  as  follows : 

Procedure.  The  following  amount  of  sample  and  reagents  should  be 
taken. 


Appro*.  p?r  cent  Impurity 
if  KC1  Present  is 

Amount  Substance  to 
be  Taken,  Gram. 

lodate  Solution  1/5  N. 
Required:  cc. 

2N.  HNOa  Required, 
cc. 

Over  5 
1.5to5 
0.2to  1.5 

0.6 
1.8 
3.6 

36 
96 
186 

20 
26 
35 

*G.  Denigds  and  L.  Chelle,  Ann.  Chem.  anal.,  1913,  18-15;  Analyst,  1913,  p.  119. 
By  means  of  the  magenta  reagent  it  is  possible  to  detect  bromine  in  the  ash  of 

Elants,  beet  root,  spinach,  etc.     The  organic   substance  may  be   decomposed  by 
eating  in  a  combustion  tube.     Filter  paper  moistened  with  the  reagent  and  held  in 
the  fumes  of  the  organic  substances  gives  the  characteristic  test  if  bromine  is  present. 
2  Method  of  F.  A.  Gooch  and  J.  C.  Blake,  Am.  Jour.  Sci.,  14,  Oct.,  1902.    Pro- 
cedure communicated  to  the  Editor  by  Prof.  Gooch. 

8  Jour.  Am.  Chem.  Soc.,  1907,  29,  275-283;  Zeits.  anorg.  Chem.,  1895,  10,  387. 


BROMINE  83 

The  mixture  is  gently  heated  to  boiling  in  a  long-necked  Kjeldahl  flask, 
inclined  at  an  angle  of  30°,  potassium  iodate  solution  added,  then  nitric  acid 
and  sufficient  water  to  make  the  volun.e  about  250  cc.  The  boiling  is  con- 
tinued until  bromine  is  expelled  (test  steam  with  2%  KI  solution  rendered 
faintly  acid  with  hydrochloric  acid).  The  mixture  is  boiled  down  to  not  below 
90  cc.  Now  1  to  1.5  cc.  of  25%  phosphorus  acid  are  added  and  the  mixture 
boiled  for  five  minutes  after  all  the  iodine  has  been  expelled.  The  colorless 
liquid  is  cooled,  mixed  with  a  slight  excess  of  1/20  or  1/50  normal  silver  nitrate 
solution  (according  to  the  proportion  of  chloride),  the  excess  of  silver  nitrate 
then  determined  by  titration  with  standard  thiocyanate  with  ferric  nitrate  as 
indicator.  (See  procedure  for  silver-thiocyanate-ferric  alum  method  of  Volhard 
for  determination  of  chlorine,  page  125.) 

Determination  of  Chlorine  in  Crude  Bromine 

Three  grams  of  bromine  (or  more  if  less  than  0.5%  chlorine  is  present)  in 
50  cc.  of  4%  potassium  iodide  solution  in  a  glass-stoppered  flask  (cooled  in  ice 
during  hot  weather)  are  shaken  and  then  transferred  to  a  Kjeldahl  flask.  Sixty 
cc.  of  1/5  N.  KI03  solution  and  24  cc.  2N.  HN03  introduced,  the  solution 
diluted  to  250  cc.  and  chlorine  determined  as  directed  above. 


CADMIUM 

WILFRED  W.  SCOTT 
Cd,  at.wt.  112,4;    sp.^r.  8.642;  m.p.  320.9°  *;    b.p.    778°  C.;    oxide,    CdO 

DETECTION 

Cadmium  is  precipitated  by  hydrogen  sulphide  from  an  acid  solution  as 
yellow  cadmium  sulphide,  CdS.  The  precipitate  is  insoluble  in  ammonium 
sulphide  (distinction  from  arsenic,  antimony,  and  tin),  but  dissolves  upon 
addition  of  hot  nitric  acid  (separation  from  mercury).  Upon  addition  of  sul- 
phuric acid  and  expulsion  of  nitric  by  taking  the  solution  to  S03  fumes,  and 
dilution  with  water,  cadmium  remains  in  solution  (lead  is  precipitated,  PbS04). 
Bismuth  is  precipitated  by  ammonium  hydroxide  and  removed  by  nitration. 
Potassium  cyanide  is  added  to  prevent  the  precipitation  of  copper  sulphide; 
and  hydrogen  sulphide  is  led  into  the  solution,  whereupon  cadmium  precipitates 
as  yellow  CdS. 

Cadmium  gives  a  brilliant  spectrum  of  green  and  blue  lines. 

Blowpipe  Tests.  Heated  on  charcoal  in  the  reducing  flame,  cadmium  gives 
a  brown  incrustation.  The  residue  is  volatile  in  the  reducing  flame. 

ESTIMATION 

The  element  occurs  combined  as  the  sulphide  in  small  quantities.  In  the 
mineral  greenockite  it  occurs  as  the  principal  element.  As  it  occurs  in  prac- 
tically all  zinc  ores  and  is  found  in  most  commercial  zinc,  it  is  determined  in 
the  analysis  of  these  substances.  It  is  a  by-product  of  lead  and  zinc  smelting. 
The  element  is  determined  in  certain  alloys,  especially  those  used  for  trial  plates 
for  silver  coinage.  It  is  determined  in  paint  pigments;  e.g.,  CdS,  yellow. 

Preparation  and  Solution  of  the  Sample 

The  metal  is  slowly  soluble  in  hot,  moderately  dilute  hydrochloric  acid  or 
sulphuric  acid,  much  more  readily  in  nitric  acid.  It  is  soluble  in  ammonium 
nitrate.  The  oxide  is  readily  soluble  in  acids. 

Treatment  of  Ores 

Sulphides  are  best  dissolved  by  treating  0.5  to  1  gram  of  the  finely  powdered 

ore  with  15  to  20  cc.  of  strong  hydrochloric  acid  and  10  cc.  of  strong  nitric 

acid.    After  standing  on  the  water  bath  for  ten  to  fifteen  minutes,  the  solution 

is  boiled    until    the  sulphides  are    decomposed,  additional  hydrochloric  being 

added  if  necessary.    Unless  silica  is  known  to  be  absent  the  solution  is  taken 

to  dryness  and  the  residue  dehydrated  in  the  air  oven  for  an  hour.    Five  to  ten 

cc.  of  strong  hydrochloric  acid  and  about  25  cc.  of  water  are  added  and  the 

lCir.  35  (2d  Ed.),  U.  S.  Bureau  of  Standards. 

84 


CADMIUM  85 

mixture  heated  to  boiling.  The  residue  of  silica  should  appear  white.  This 
is  filtered  off  and  cadmium  determined  in  the  filtrate  after  making  the  necessary 
separations. 

If  lead  is  present  it  is  advisable  to  add  5-6  cc.  of  concentrated  sulphuric 
acid  to  ,,the  cooled  solution  after  the  hydrochloric-nitric  acid  treatment  and 
to  evaporate  to  S03  fumes.  After  cooling,  50  cc.  of  water  are  added  and  the 
mixture  heated  to  boiling,  then  placed  on  the  steam  bath  until  any  iron  present 
has  completely  dissolved.  Silica  and  lead  are  now  filtered  off  and  the  filtrate 
treated  as  directed  under  " Separations." 

Carbonates  may  be  dissolved  by  hydrochloric  acid  alone.  Evaporation 
to  dryness  is  necessary  if  silica  is  present. 

Alloys  are  best  dissolved  in  hydrochloric  and  nitric  acids,  followed  by  addition 
of  sulphuric  acid,  and  nitric  acid  then  expelled  by  evaporating  the  solution 
to  SO 3  fumes. 

SEPARATIONS 

Removal  of  Silica.  The  procedure  has  been  given  under  "Preparation 
and  Solution  of  the  Sample." 

Separation  from  the  Ammonium  Sulphide  Group,  the  Alkaline  Earths 
and  the  Alkalies.  The  solution,  acidified  with  2  cc.  of  concentrated  sulphuric 
acid  or  about  5  cc.  of  strong  hydrochloric  acid  per  100  cc.,  is  treated  with 
hydrogen  sulphide  to  saturation.  The  precipitate,  containing  cadmium  sul- 
phide with  other  members  of  the  group  that  were  present  in  the  original  solu- 
tion, is  filtered  off  and  washed  with  hydrogen  sulphide  water  slightly  acidulated 
with  hydrochloric  acid. 

Removal  of  Arsenic,  Antimony,  and  Tin.  Treatment  in  Absence  of 
Copper.  The  precipitate  is  rinsed  from  the  filter  into  the  beaker  as  completely 
as  possible  with  no  more  water  than  is  necessary.  The  beaker  is  placed  under 
the  filter  and  cold  solution  of  potassium  hydroxide  (20%)  is  poured  onto  the 
filter.  (Sodium  hydroxide  will  do.)  Arsenic,  antimony,  and  tin  will  dissolve 
and  leave  cadmium  sulphide.  A  dark-colored  residue  indicates  the  presence 
of  bismuth,  lead,  and  less  frequently,  of  mercury. 

Treatment  in  Presence  of  Copper.  A  strong  solution  of  potassium  cyanide 
may  be  used  in  place  of  a  fixed  alkali  hydroxide.  By  this  treatment,  the  copper 
is  removed  along  with  arsenic,  antimony,  and  tin. 

If  the  precipitate  is  yellow  or  orange-colored,1  it  is  dissolved  in  hydrochloric 
acid,  after  thorough  washing  with  hydrogen  sulphide  water,  and  the  solution 
treated  according  to  one  of  the  procedures  given  later. 

Removal  of  Lead  and  Bismuth.  Should  the  above  precipitate  appear 
dark-colored,  lead,  bismuth,  and  possibly  mercury  are  indicated.  In  the  pre- 
liminary treatment  of  the  ore  with  sulphuric  acid,  the  lead  is  generally  com- 
pletely removed  as  lead  sulphate,  but  traces  may  be  present  in  the  filtrate.  The 
moist  precipitate  and  filter  are  placed  in  a  flask  and  10  cc.  of  strong  hydro- 
chloric acid  added,  with  an  equal  amount  of  water.  The  mixture  is  boiled  until 
the  cadmium  sulphide  dissolves,  the  H2S  gas  being  driven  out  of  the  solution. 
The  solution,  diluted  with  25  cc.  of  water,  is  filtered,  and  the  filter  washed  with 
hot  water.  Any  dark  residue  may  be  rejected.  The  filtrate  is  diluted  some- 
what and  then  sodium  carbonate  added  in  slight  excess,  followed  by  1  or  2 
grams  of  potassium  cyanide.  After  digesting  for  some  time  at  a  gentle  heat 

1  Cadmium  sulphide  precipitated  from  a  sulphuric  acid  solution  is  orange-colored. 


86  CADMIUM 

the  mixture  is  filtered  and  washed  with  cold  water.  Bismuth  and  lead  remain 
on  the  filter  as  carbonates.  H2S  is  now  passed  into  the  filtrate,  diluted  if 
necessary.  This  should  precipitate  pure  cadmium  sulphide,  unless  mercury 
is  present.  The  residue  is  washed  with  hydrogen  sulphide  water,  and  then 
dissolved  in  hydrochloric  acid. 

Separation  of  Cadmium  from  Mercury.  This  separation  is  seldom  re- 
quired. The  procedure  is  based  upon  the  insolubility  of  mercury  sulphide  in  hot 
dilute  nitric  acid,  whereas  cadmium  sulphide  is  readily  soluble.  The  two  sul- 
phides are  boiled  with  nitric  acid,  1:3,  filtered  and  the  residue  washed  with  hot 
water.  The  filtrate  is  evaporated  with  a  little  sulphuric  acid  to  small  volume 
on  the  hot  plate  and  then  to  S03  fumes.  (Spattering  during  the  last  stages  of 
removal  of  water  will  cause  loss  unless  the  recepticle  is  covered.)  The  cooled 
residue  is  taken  up  with  water  and  if  any  insoluble  matter  remains  it  is  filtered 
off.  Cadmium  is  now  determined  in  the  solution. 


GRAVIMETRIC    METHODS    FOR    THE    DETERMINATION    OF 

CADMIUM 

Determination  as  Cadmium  Sulphate,  CdSO4 

The  hydrochloric  acid  solution  of  cadmium  obtained  under  the  section  on 
isolation  of  the  cadmium  is  evaporated  to  dryness  on  the  water  bath  in  a  weighed 
platinum  crucible  or  dish.  The  residue  is  covered  with  a  slight  excess  of  dilute 
sulphuric  acid,  the  solution  again  evaporated  as  far  as  possible  on  the  water 
bath,  and  finally  the  excess  sulphuric  acid  expelled  by  gently  heating.  This 
final  stage  is  best  accomplished  by  placing  the  crucible  in  a  larger  one,  pro- 
vided with  an  asbestos  ring  to  separate  the  two.  The  outer  crucible  may  now 
be  heated  to  redness  without  danger  of  decomposing  the  cadmium  sulphate. 
The  heating  is  continued  until  no  more  fumes  of  sulphuric  acid  are  evolved. 
The  residue  is  weighed  as  cadmium  sulphate,  CdS04. 

CdS04X0.5392=Cd. 

Electrolytic  Determination  of  Cadmium 

This  method  for  determination  of  cadmium  is  exceedingly  accurate.  The 
procedure  recommended  by  Treadwell  *  gives  excellent  results. 

Procedure.  A  drop  of  phenol phthalein  is  added  to  the  cadmium  sulphate 
solution  (obtained  by  evaporating  the  hydrochloric  acid  solution  with  sulphuric 
acid  to  S03  fumes),  then  a  solution  of  pure  caustic  soda  until  a  permanent  red 
color  is  obtained.  A  strong  solution  of  potassium  cyanide  is  now  stirred  in,  adding 
drop  by  drop,  until  the  cadmium  hydroxide  precipitate  just  dissolves  (an  excess 
should  be  avoided).  The  solution  is  diluted  to  about  100  cc.  with  water  and 
electrolyzed  in  the  cold,  using  a  gauze  cathode,  the  current  being  0.5  to  0.7  ampere 
and  the  electromotive  force  4.8  to  5  volts.  At  the  end  of  five  or  six  hours  the 
current  is  increased  to  i-i.2  amperes,  and  the  solution  electrolyzed  for  an  hour 
more. 

i  Treadwell  and  Hall,  Analytical  Chem.,  Vol.  II.  Beilstein  and  Jawein,  Ber.,  12, 
446. 


CADMIUM  87 

The  liquid  is  quickly  poured  off,  or  better,  the  beaker  lowered,  and  another 
of  water  substituted.  The  deposited  metal  is  then  washed  by  dipping  the 
cathode  in  alcohol  and  finally  in  ether.  After  drying  at  100°  C.,  the  coded 
cathode  is  weighed.  The  increase  of  weight  represents  the  deposited  metal, 
cadmium. 

E.  F.  Smith,1  recommends  the  addition  of  one  gram  of  potassium  cyanide  to 
50  cc.  solution  of  the  chloride  or  sulphate  salt,  followed  by  dilution  to  125  cc.  The 
electrolysis  is  conducted  at  a  temperature  of  60°  C.  with  N.D.10o  =  .06  ampere  and 
E.M.F.=  3.2  volts. 

Rapid  deposition  can  be  effected  by  means  of  the  rotating  anode  (600  revolutions 
per  minute).  The  solution  of  cadmium  sulphate  containing  3  cc.  of  H2S04  (1  :  10) 
per  150  cc.  The  solution,  heated  to  boiling,  is  electrolyzed  with  a  current  of  N.D.ioo 
=  5  amperes,  E.M.F.  =8-9  volts.  Fifteen  minutes  is  sufficient  for  the  deposition 
of  .5  gram  of  cadmium. 

NOTES.  Before  washing  and  discontinuing  the  current,  it  is  advisable  to  add 
a  little  water  to  raise  the  level  of  the  liquid  and  continue  the  electrolysis  to  ascertain 
whether  the  deposition  is  complete. 

Traces  of  cadmium  may  be  estimated  in  the  above  solution  by  saturating  this 
with  H2S  and  comparing  the  yellow-colored  colloidal  cadmium  sulphide  solution  with 
a  known  quantity  of  cadmium  and  the  same  amounts  of  potassium  hydroxide  and 
cyanide  as  in  the  solution  tested. 

VOLUMETRIC  DETERMINATION  OF  CADMIUM 
Titration  of  Cadmium  Sulphide  with  Iodine.2 

The  titration  of  cadmium  sulphide  with  standard  iodine  in  a  hydrochloric 
acid  solution  is  the  same  as  the  procedure  given  for  determination  of  sulphur 
by  the  evolution  method,  the  following  reaction  taking  place : 

CdS+2HCl-hI2  =  CdCl2+2HI+S. 

Procedure.  Cadmium  having  been  isolated  as  the  sulphide  according  to 
the  standard  procedures  given,  the  precipitate  is  washed  and  allowed  to  drain 
on  the  filter.  The  filter,  together  with  the  sulphide,  is  placed  in  a  beaker 
or  an  Erlenmeyer  flask,  water  added,  and  the  whole  shaken  to  break  up  the 
precipitate.  A  moderate  quantity  of  hydrochloric  acid  is  added  and  the  solu- 
tion titrated  with  standard  N/5  or  N/10  iodine  solution.  Towards  the  end 
a  little  starch  solution  is  added  and  the  titration  continued  until  the  excess 
of  iodine  colors  the  solution  blue.  If  preferred,  an  excess  of  iodine  solution 
may  be  added  and  the  excess  determined  by  a  back-titration  with  standard 
thiosulphate  solution. 

One  cc.  N/10  iodine  =0.00582  gram  cadmium. 

1  Electro-Analysis,  E.  F.  Smith.     P.  Blakiston's  Son  &  Co.  Pub. 

2  P.  von  Berg  (Z.  a.  C.,  26,  23)   transfers  the  precipitate  and  filter  to  a  stoppered 
flask,  expels  the  air  with  CO2  and  by  boiling  and  then  titrates  in  an  hydrochloric  acid 
solution.    Experiments  by  the  author  have  shown  this  caution  to  be  unnecessary. 


CALCIUM 

WILFRED  W.  SCOTT 
Ca,  at.wt.  40.07;  sp.gr.  1.544629";  m.p.  810° »  C.;  oxide,  CaO 

DETECTION 

In  the  usual  course  of  qualitative  and  quantitative  analysis  calcium  passes 
into  the  filtrates  from  the  elements  precipitated  by  hydrogen  sulphide  in  acid 
and  alkaline  solutions  (Ag,  Hg',  Hg",  Pb,  Cu,  Cd,  As,  Sb,  Sn,  Fe,  Cr,  Al,  Mn, 
Ni,  Co,  Zn,  etc.),  and  is  precipitated  from  an  ammoniacal  solution  by  am- 
monium carbonate  as  calcium  carbonate,  along  with  the  carbonates  of  barium 
and  strontium.  The  separation  of  calcium  from  barium  and  strontium  is  con- 
sidered under  Separations.  The  oxalate  of  calcium  is  the  least  soluble  of 
the  alkaline-earth  group.2  All,  however,  are  soluble  in  mineral  acids.  Calcium 
oxalate  may  be  precipitated  from  weak  acetic  acid  solution  by  ammonium 
oxalate. 

Flame  Test.  The  flame  of  a  Bunsen  burner  is  colored  yellowish  red  when 
a  platinum  wire  containing  calcium  salt  moistened  with  concentrated  hydrochlo- 
ric acid  is  held  in  the  flame. 

Spectrum.  An  intense  orange  and  green  line  with  a  less  distinct  violet 
line.  Note  chart  of  the  spectra  of  the  alkaline  earths.  Plate  II. 

See  chapter  on  Barium  under  Separations — Preliminary  Tests,  page  52. 

ESTIMATION 

The  determination  of  calcium  is  required  in  complete  analyses  of  ores.  It 
is  of  special  importance  in  the  analysis  of  mortar,  cement,  bleaching  powder,, 
plaster  of  Paris,  certain  paint  pigments  such  as  phosphorescent  paint,  CaS. 
The  determination  is  required  in  the  analysis  of  water. 

Calcium  occurs  in  the  following  substances:  as  carbonate  in  limestone, 
marble,  chalk,  Iceland  spar,  shells,  coral,  pearl.  Together  with  magnesium  it 
is  found  in  dolomite.  It  occurs  as  sulphate  in  anhydrite,  gypsum,  alabaster^ 
selenite;  as  silicate  in  the  mineral  wollastonite,  CaSi03;  as  phosphate  in  phos- 
phorite, Ca3(P04)2,  also  in  bones  and  in  apatite,  3Ca3(P04)2-CaF2;  as  fluoride 
in  fluorspar,  CaF2.  As  oxalate  it  occurs  in  plant  cells.  It  is  found  in  nearly  all 
mineral  springs,  artesian  wells,  and  river  waters,  principally  as  bicarbonate  of 
calcium,  CaHCO,. 

Preparation  and  Solution  of  the  Sample 

The  oxide,  hydroxide,  and  salts  of  calcium  are  soluble  in  acids  with  the 
exception  of  gypsum  and  certain  silicates  which  require  fusion  with  sodium 
carbonate  or  bicarbonate  followed  by  an  hydrochloric  acid  extraction. 

»Cir.  35  (2d  Ed.)  U.  S.  Bureau  of  Standards. 

2  Solubility:   CaC2O4-H2O  =0.000554  gram  per  100  cc.  H2O.  BaC2O4.H2O  =0.0093 
gram.    SrC2O4-H2O= 0.0051  gram.    MgC2O42H2O= 0.07  gram. 
Van  Nostrand's  Chem.  Annual — Olsen. 

88 


\  CALCIUM  89 

Solution   of  Limestones,   Dolomites,  Magnesites,  Cements,  Lime,  etc. 

One  gram  of  the  powdered  material  is  digested  in  a  250-cc.  beaker  with 
20  cc.  of  water,  5  cc.  of  concentrated  hydrochloric  acid,  and  2  or  3  drops  of 
nitric  acid  (sp.gr.  1.42).  The  beaker  is  covered  to  prevent  loss  by  effervescence. 
When  the  violent  action  has  subsided,  the  sample  is  placed  on  a  hot  plate  and 
boiled  for  a  few  minutes.  The  watch-glass  is  rinsed  into  the  beaker  and  the 
solution  filtered.  The  residue  is  washed,  dried  and  ignited  in  a  platinum  cru- 
cible, and  then  fused  with  a  little  sodium  carbonate  or  bicarbonate.  The  cooled 
fusion  is  dissolved  in  hot  dilute  hydrochloric  acid,  the  liquid  added  to  the  main 
solution  and  calcium  determined  by  precipitation  as  calcium  oxalate,  after  removal 
of  silica,  iron,  alumina,  etc. 

Solution  of  Gypsum,  Plaster  of  Paris,  and  Sulphates  of  Lime,  etc.  The 
treatment  of  the  sample  is  similar  to  the  one  given  above  with  the  exception 
that  it  is  advisable  to  add  a  larger  amount  of  strong  hydrochloric  acid,  e.g., 
about  20  to  25  cc.  If  barium  sulphate  is  present  it  is  indicated  by  the  clouding 
of  the  solution,  upon  acidifying  the  water  extract  of  the  carbonate  fusion. 

Silicates.  Solution  of  silicates  is  best  obtained  by  direct  fusion  of  1  gram 
of  the  powdered  material  with  4  to  5  grams  of  sodium  carbonate,  in  a  plati- 
num crucible.  The  cooled  melt  is  now  covered  with  water  and  dissolved  with 
hydrochloric  acid  according  to  the  standard  procedure  for  carbonate  fusions. 
The  hydrochloric  acid  solutions  are  taken  to  dryness  and  the  silica  dehydrated 
in  an  oven  at  110°  C.  for  an  hour  and  then  the  residue  is  extracted  with  dilute 
hydrochloric  acid  and  filtered.  The  filtrate  contains  iron,  alumina,  magnesium, 
lime,  etc. 

Chlorides,  Nitrates,  and  Other  Water-soluble  Salts.  These  are  dissolved 
in  water  slightly  acidified  with  hydrochloric  acid. 

Sulphides,  Pyrites  Ore,  etc.  The  ore  should  be  oxidized  with  bromine  or 
by  roasting,  previous  to  the  acid  treatment. 

SEPARATIONS 

Removal  of  Silica.  The  solution  obtained  by  one  of  the  above  procedures 
is  evaporated  to  dryness  and  the  silica  dehydrated  at  110°  C.  for  an  hour.  The 
residue  is  now  extracted  with  dilute  hydrochloric  acid.  Silica  remains  insoluble 
and  may  be  filtered  off.  The  solution  contain,  lime,  together  with  iron,  alumina, 
magnesia,  etc.,  as  chlorides. 

Removal  of  Iron  and  Alumina.  The  filtrate  from  the  silica  residue  is 
treated  with  a  few  drops  of  nitric  acid  and  boiled  to  oxidize  the  iron.  Ammonia 
is  now  added  cautiously  until  the  solution  just  smells  of  it  (a  large  excess  over 
that  required  to  neutralize  the  acid  and  combine  with  iron  and  alumina, 
will  tend  to  dissolve  A1(OH)3).  The  precipitated  hydroxides  are  allowed  to 
settle  and  then  filtered  hot  through  a  rapid  filter  and  washed  with  hot  water. 
Calcium,  together  with  magnesium,  is  in  solution  and  passes  into  the  filtrate. 

Removal  of  Copper,  Nickel,  Cobalt,  Manganese,  Zinc,  and  Elements 
Precipitated  as  Sulphides  in  Acid  and  Alkaline  Solutions.  This  separation 
is  required  seldom  in  lime-bearing  ores.  In  analysis  of  pyrites  and  certain 
other  ores,  containing  members  of  the  hydrogen  sulphide  and  ammonium  sul- 
phide groups,  the  removal  of  these  impurities  is  necessary. 

The  solution  from  the  residue  of  silica  is  made  slightly  ammoniacal  and 
H2S  passed  into  the  solution  to  saturation  (or  ammonium  sulphide  may  be 


90  CALCIUM 

added).  The  precipitated  sulphides  are  filtered  off  from  the  solution  heated  to 
boiling.  The  filtrate  containing  the  calcium  is  boiled  down  to  50  to  75  cc.  and 
the  precipitated  sulphur  removed  by  filtration.  Calcium  is  determined  in  the 
filtrate  by  precipitation  with  ammonium  oxalate  or  oxalic  acid  according  to 
directions  given  later. 

Separation  of  Calcium  from  Magnesium  and  the  Alkalies.  In  the  pres- 
ence of  considerable  amounts  of  calcium  and  comparatively  small  quantities 
of  magnesium  the  oxalate  method  of  precipitating  calcium,  in  presence  of 
ammonium  chloride,  is  generally  sufficient  for  precipitating  calcium  free  from 
magnesium  and  the  alkalies.  In  analysis  of  dolomite,  MgC03-CaC03,  and  of 
samples  containing  comparatively  large  amounts  of  magnesium,  a  double  pre- 
cipitation of  calcium  is  generally  necessary  for  removal  of  occluded  magnesium. 

Separation  of  Calcium  from  Barium  and  from  Strontium.  The  alkaline 
earths  are  converted  to  nitrates,  all  moisture  expelled  by  heat,  and  calcium 
nitrate  extracted  from  the  insoluble  nitrates  of  barium  and  strontium  by  a 
mixture  of  anhydrous  ether  and  absolute  alcohol,  in  equal  parts,  or  by  boiling 
the  dry  nitrates  in  amyl  alcohol  (b.p.,  137.8°  C.).  Details  of  the  procedure  are 
given  under  Separations  of  the  Alkaline  Earths  in  the  chapter  on  Barium,  page  53. 

Phosphate  Rocks,  Calcium  Phosphate,  etc.1 

Determination  of  Lime  in  Presence  of  Phosphates,  Iron,  and  Alumina. 

Should  phosphoric  acid  be  present  in  the  solution,  calcium  will  be  precipitated 
as  a  phosphate  upon  making  the  solution  neutral  or  slightly  alkaline  with 
ammonia,  and  will  remain  with  iron  and  alumina  precipitates. 

Precipitation  of  Calcium  Oxalate  in  Presence  of  Iron  and  Alumina. 
The  solution  containing  the  .phosphates  freed  from  silica  is  oxidized  by 
boiling  with  nitric  acid  as  usual.  Ammonia  water  is  added  to  the  cooled 
solution  until  a  slight  precipitate  forms,  and  then  citric  acid  is  added  in  suf- 
ficient quantity  to  just  dissolve  the  precipitate.  If  this  does  not  readily  occur, 
additional  ammonia  is  added,  followed  by  citric  acid  until  the  solution  clears, 
then  about  15  cc.  of  citric  acid  in  excess.  The  solution  is  diluted  to  200  cc. 
and  heated  to  boiling.  Calcium  oxalate  is  now  precipitated  by  addition  of 
ammonium  oxalate.  Iron  and  alumina  remain  in  solution. 

Citric  acid  is  made  by  dissolving  70  grams  of  the  acid,  H3C6H507  •  H2O,  in  a 
liter  of  water. 

Wagner's  Solution.  In  place  of  citric  acid,  the  following  solution  may  be 
used.  Twenty-five  grams  of  citric  acid  and  1  gram  of  salicylic  acid  are  dissolved 
in  water  and  made  to  1000  cc.  Twenty-five  to  50  cc.  of  this  reagent  is  effective 
in  preventing  precipitation  of  iron  and  alumina. 

1  Zeit.  fur  Angewandte  Chemie,  34,  776,  Aug.,  1898. 


CALCIUM  91 

GRAVIMETRIC   DETERMINATION  OF  CALCIUM 
Precipitation  of  Calcium  Oxalate  and  Ignition  to  Calcium  Oxide 

Calcium  oxalate  is  precipitated  from  feebly  ammoniacal  solutions  or  from 
solutions  acidified  with  acetic,  oxalic,  citric,  or  salicylic  acids,  by  means  of 
ammonium  oxalate.  The  presence  of  ammonium  chloride  hinders  precipitation 
of  magnesium  and  does  not  interfere  with  that  of  calcium.  If,  however,  much 
magnesium  (or  sodium)  is  present  it  will  contaminate  the  calcium  precipitate 
so  that  a  second  precipitation  is  necessary  to  obtain  a  pure  product.  The 
compound  formed  from  hot  solutions  is  crystalline  or  granular  and  filters  readily, 
whereas  the  flocculent  precipitate  formed  in  cold  solutions  does  not.  Calcium 
oxalate,  CaC204-H20,1  decomposes  at  red  heat  to  CaO,  in  which  form  it  is 
weighed. 

Procedure.  If  the  calcium  determined  is  in  the  filtrate  from  previous 
groups,  hydrogen  sulphide  is  expelled  by  boiling  and  the  precipitated  sulphur 
filtered  off,  the  solution  having  been  concentrated  to  about  200  cc.  The  fil- 
trate should  contain  sufficient  ammonium  chloride  to  hold  magnesium  in  solu- 
tion in  presence  of  ammonium  oxalate  (i.e,  about  10  grams  NH4C1  per  0.0015 
gram  MgO  per  100  cc.  of  solution.)  2  If  not  already  present,  the  chloride  is 
added  in  sufficient  amount,  and  the  solution  diluted  to  about  400  cc. 

Precipitation.  The  solution  is  heated  to  boiling  and  10  cc.  of  acetic  acid 
added  to  the  neutral  mixture.  Fifteen  cc.  or  more  of  a  saturated  solution  of 
oxalic  acid  3  is  added  and  after  five  minutes  a  slight  excess  of  ammonia.  The 
solution  is  allowed  to  cool  an  hour  or  so,  the  clear  solution  decanted  through 
a  10-cm.  filter  and  the  precipitate  washed  three  times  by  decantation  and  finally 
on  the  filter  with  dilute  ammonia  (1  :  10),  or  1%  ammonium  oxalate. 

To  remove  clinging  impurities  (Na  or  Mg)  the  precipitate  is  dissolved  in 
dilute  nitric  acid  (1  :  4)  and  the  filtrate  collected  in  the  beaker  in  which  the 
first  precipitation  was  made.  The  solution  is  heated  to  boiling  after  addition 
of  a  few  drops  of  oxalic  acid  and  sufficient  ammonium  hydroxide  to  make  the 
solution  slightly  alkaline.  The  precipitated  oxalate  is  allowed  to  settle,  filtered 
and  washed  as  in  the  first  precipitation,  the  oxalate  adhering  to  the  sides 
of  the  beaker  being  carefully  " copped"  out.  The  oxalate  is  ignited  wet  in  a 
weighed  crucible,  the  heat  being  low  at  first,  until  the  filter  has  charred  and 
then  to  the  full  heat  of  the  Me*ker  blast  lamp.  Fifteen  minutes  of  blasting 
should  be  sufficient  to  obtain  constant  weight.  If  the  precipitate  is  large  a  second 
ignition  is  advisable  to  insure  the  complete  decomposition  of  the  oxalate  and 
carbonate  to  oxide. 

The  crucible  is  cooled  in  a  desiccator  and  weighed  as  soon  as  possible.4 

Factors.  CaO  X 0.7146  =Ca,  or  X1.7847=CaC03,  or  X 2.8908  =Ca(HC03)2, 
or  X  2.428  =CaS04. 

lCalcium  oxalate  dried  at  100  =  CaC2O4-H2O.  Heated  to  200°  C.=  =CaC2O4. 
At  500°  C.  the  oxalate  begins  to  decompose,  free  carbon  is  liberated,  and  calcium 
carbonate  begins  to  form.  At  bright  red  heat  carbon  burns  off  and  the  carbonate  is 
completely  decomposed  to  the  oxide  and  CO2. 

2  Mellor,  "A  Treatise  on  the  Ceramic  Industries,"  213  (1913). 

3  Approximately  8.6%  at  20°  C.     About  five  times  as  much  ammonium  oxalate 
as  is  required  for  combination  with  calcium  and  magnesium  should  be  added  to  the 
solution. 

4  Calcium  oxide  absorbs  moisture  and  CO2  from  the  air. 


92  CALCIUM 

Other  Methods.     Gravimetric 

Calcium  may  be  converted  to  carbonate,  sulphate  or  fluoride  and  so  weighed. 
The  oxide  above  obtained  may  be  converted  to  sulphate  by  moistening  with 
a  few  drops  of  water  and  then  adding  a  slight  excess  of  sulphuric  acid  (1:4, 
dilute).  The  excess  sulphuric  acid  is  driven  off  by  heating  over  a  low  flame 
to  S03  fumes  and  then  more  strongly  at  dull  red  heat  until  the  excess  acid  has 
been  expelled.  A  ring  burner  reduces  the  risk  of  spurting.  Addition  of  a  drop 
or  so  of  ammonia  to  the  cooled  residue  and  reheating  assists  expulsion  of  the 
acid.  The  residue  is  weighed  as  CaS04. 

CaS04X 0.2943  =Ca  or  X0.4119=CaO  or  X 0.7352  =CaC03. 

VOLUMETRIC  DETERMINATION  OF  CALCIUM 
Titration  of  the  Oxalate  with  Permanganate  1 

This  procedure  may  be  applied  successfully  in  a  great  variety  of  instances 
on  account  of  the  readiness  with  which  calcium  oxalate  may  be  separated. 
In  the  presence  of  iron,  alumina,  manganese,  magnesia,  etc.,  it  is  advisable  to 
make  a  reprecipitation  of  calcium  oxalate  to  free  it  from  adhering  contaminations. 

The  following  reaction  takes  place  when  potassium  permanganate  is  added 
to  calcium  oxalate  in  acid  solution: 

5CaC204+2KMn04+8H2S04=5CaS04+K2S04+2MnS04+10C02+8H20. 

Procedure.  Calcium  oxalate,  obtained  pure,  by  precipitation  and  washing 
according  to  directions  given  under  the  gravimetric  determination  of  calcium, 
is  washed  into  a  flask  through  a  perforation  made  in  the  filter  paper,  the  filter 
is  treated  with  a  little  warm,  dilute  sulphuric  acid  2  and  the  adhering  oxalate 
dissolved  and  washed  into  the  flask.  About  25  cc.  of  dilute  sulphuric  acid, 
1  :  1,  is  added  and  the  solution  diluted  to  250  to  300  cc. 

When  the  precipitate  has  dissolved,  the  solution  warmed  to  60  or  70°  C. 
is  titrated  with  standard  potassium  permanganate,  added  cautiously  from  a 
burette  with  constant  agitation,  until  a  faint  permanent  pink  color  is  obtained. 

One  cc.  N/10  KMn04  =0.0020  gram  Ca,3  or  ^KO.0028  =CaO. 

Factors.  CaX1.3993=CaO  or  X2.4974=CaC03  or  X3.3975=CaS04  or 
X2.581=Ca3(P04)2. 

Analysis  of  Limestone  and  Cement.  See  chapter  on  Cement  by  Richard  K. 
Meade. 

1Fresenius,  Hempel,  Mohr,  Sutton  and  others  have  testified  to  the  accuracy 
of  this  methoa  for  the  determination  of  calcium. 

2  HC1  in  moderate  quantity  may  be  used  in  place  of  sulphuric  acid  without  danger 
of  liberating  free  chlorine  as  is  the  case  in  presence  of  iron. — Fleischer. 

8  From  the  reaction  2KMnO4,  equivalent  to  5O  or  10H,  reacts  with  5CaC2O4. 
and  5Ca=  (5X40) -7-10  =  20.  A  normal  solution  of  calcium  =  20  grams  Caper  liter. 
One  cc.  N/10  solution  =0.002  gram  Ca. 


CARBON 

WILFRED  W.  SCOTT. 

C,1  at.wt.  12.0;  sp.gr.  amorp.  1.75-3.10;  cryst.:  graphite,  2.25;  diamond, 
3.47-3.5585;  m.p.  sublimes  at  3500°  C.;  oxides,  CO  and  CO2 

DETECTION2 

Element.  Carbon  is  recognized  by  its  appearance  and  by  its  inertness 
towards  general  reagents.  It  is  seen  in  the  charring  of  organic  matter  when 
heated  or  when  acted  upon  by  hot  concentrated  sulphuric  acid. 

Upon  combustion  with  oxygen  or  by  oxidation  with  chromic  and  sulphuric 
acids,  carbon  dioxide  is  formed.  The  gas  passed  into  lime  water  forms  a  white 
precipitate,  CaC03.  White  precipitates  are  formed  when  the  gas  is  led  into 
baryta  water  (BaC03  ppt.),  or  into  an  ammoniacal  solution  of  lead  acetate 
(PbCOg  pptd.). 

Carbon  Dioxide.  Carbonates.  CO2  in  Gas.  A  white  precipitate  with  lime 
water,  baryta  water,  ammoniacal  solutions  of  calcium,  or  barium  chlorides,  or 
lead  acetate  (basic). 

Carbonates.  Action  of  mineral  acids  cause  effervescence,  C02  being  evolved. 
The  gas  is  odorless  (distinction  from  S02,  H2S,  and  N203)  and  is 
colorless  (distinction  from  N203).  The  gas  absorbed  in  the 
reagents  above  mentioned  produces  a  white  precipitate.  The 
test  is  best  made  by  placing  the  powdered  material  in  a  large 
test-tube  with  a  stopper  carrying  a  funnel  and  delivery  tube  as 
shown  in  the  illustration,  Fig.  9.  For  small  amounts  of  combined 
C02,  warming  of  the  test-tube  may  be  necessary.  Sulphuric  or 
phosphoric  acid  should  be  used  to  liberate  the  gas,  which  is 
conducted  into  the  reagent  used  for  the  test. 

Distinction  between  Soluble  Carbonates  and  Bicarbonates. 
The  solution  of  the  former  is  alkaline  to  phenolphthalein  indicator 
(pink).  Bicarbonate  solutions  remain  colorless  with  this  indi- 
cator. Normal  carbonates  precipitate  magnesium  carbonate  when 
added  to  magnesium  sulphate  solution;  bicarb onates  cause  no 
precipitation.  FlG  9._Test  for 

Free  Carbonic  Acid  in  Water  in  Presence  of  Bicarbon-      Carbonate, 
ates.     0.5  cc.  of  rosolic  acid  (1  part  acid  in  500  parts  of  80% 
alcohol),  produces  a   red  color  with  bicarbonates  in  absence  of  free  C02,  and  a 
colorless  or  faintly  yellow  solution  when  free  C02  is  present. 

Carbon  Monoxide.  The  gas  burns  with  a  pale  blue  flame  and  is  not  ab- 
sorbed by  potassium  hydroxide  or  lime  water  (distinction  from  C02).  It  is  oxi- 
dized to  C02  and  so  detected.  With  hot,  concentrated  potassium  hydroxide, 
potassium  formate  is  produced. 

The  gas  is  detected  in  the  blood  by  means  of  the  absorption  spectrum. 

1  Van  Nostrand's  Chemical  Annual,  Olsen. 

2  Prescott  and  Johnson,  "Qual.  Chem.  Anal." 

93 


M'2  CO, 


94  CARBON" 


ESTIMATION 

The  element  occurs  free  in  nature  in  the  crystalline  forms,  diamond  and 
graphite,  and  in  the  amorphous  form,  charcoal,  coke,  etc.  It  occurs  in  iron, 
steel,  and  in  certain  alloys.  Its  estimation  in  these  metals  is  generally  required. 
Carbon  is  determined  in  the  analysis  of  organic  compounds  in  which  it  is 
invariably  combined  and  may  also  be  present  as  free  carbon  (asphaltum) . 

Combined  as  a  carbonate  it  occurs  in  a  large  number  of  substances,  among 
which  are  found  calcite,  marble,  limestone,  dolomite,  magnesite,  strontianite, 
witherite,  spatic  iron  ore.  It  occurs  as  the  dioxide  in  the  air,  in  water  (H20-C02) 
and  in  flue  gas.  Carbon  dioxide  is  the  active  constituent  of  baking  powders 
(NaHC03). 

Preparation  of  the  Sample 

Iron,  Steel,  and  Alloys.  Drillings  taken  from  different  sections  of  the  rep- 
resentative bar  should  be  free  from  grease  and  dust.  These  are  best  kept  in 

glass-stoppered  bottles.  Where  a  large  number  of 
daily  samples  are  determined,  it  is  found  more 
convenient  to  use  small  manila  envelopes,  upon 
which  the  record  of  the  analysis  may  be  placed. 
Should  it  be  impossible  to  obtain  drillings  free 
from  grease,  this  impurity  may  be  removed  by 
heating  the  sample  in  an  atmosphere  of  nitrogen,  or 
by  repeated  extraction  with  ether. 

Coarse  chips,  cast-iron  drillings,  etc.,  should  be 
broken  down  in  a  chilled-steel  mortar,  Fig.  10. 
FIG.  10. — Chilled  Steel  Mortar.         Carbon  may   now  be  separated  in   a   definite 

weight  of  the  sample  as  directed  below,  or  it  may 

be  determined  by  direct  combustion  or  by  oxidation  with  chromic  acid  accord- 
ing to  a  procedure  given  later. 

Organic  Matter.  It  is  advisable  to  fuse  this  in  a  nickel  or  iron  crucible 
with  sodium  peroxide.  The  carbonate  thus  formed  may  be  determined  as  usual. 
The  organic  substance  may  be  oxidized  directly  in  the  combustion  furnace. 

Carbonates.  Limestone,  Dolomite,  Cement,  Alkali  Carbonates  and 
Bicarbonates.  The  powdered  material  is  decomposed  by  addition  of  an  acid 
as  directed  in  the  methods  given  later. 

Separation  of  Carbon  from  Other  Substances 

The  element  is  generally  determined  as  carbon  dioxide,  in  which  form  it  is 
liberated  from  most  of  the  combinations  in  which  it  occurs,  free  from  other 
substances  by  ignition  in  a  current  of  oxygen,  or  by  oxidation  with  chromic 
acid  as  directed  later. 

Separation  of  Carbon  in  Iron  and  Steel.  Cupric  Potassium  Chloride 
Method.  0.5  to  2  grams  of  the  drillings  are  treated  with  100  to  200  cc.  of 
cupric  potassium  chloride  solution  and  10  cc.  of  hydrochloric  acid  (1.19).  This 
mixture  dissolves  the  iron  according  to  the  reaction 

Fe-f-CuCl2=FeCL>+Cu  and  Cu+CuCl2=Cu2Cl2-f- carbon  as  a  residue. 


CARBON  95 

The  solution  should  be  stirred  frequently  to  hasten  the  solution  of  the  iron. 
It  is  advisable  to  keep  the  temperature  of  the  solution  at  about  50°  C.  When 
the  iron  and  copper  have  dissolved  the  carbon  is  filtered  off  into  a  perforated 
platinum  boat  or  crucible,  as  directed  under  the  methods.  It  is  now  oxidized 
to  C02  and  so  determined. 

NOTE.  The  cupric  potassium  chloride  solution  is  prepared  by  dissolving  150 
parts  of  potassium  chloride  and  170  parts  of  crystallized  cupric  chloride  in  water 
and  crystallizing  out  the  double  salt.  Three  hundred  grams  of  this  salt  are  dissolved 
in  1000  cc.  The  solution  may  be  used  several  times  by  chlorinating  the  dirty  brown 
filtrate  from  the  carbonaceous  residue.  The  cuprous  chloride  formed  daring  the 
solution  of  the  steel  is  converted  again  to  cupric  chloride,  and  the  chlorinated  double 
salt  is  even  more  energetic  in  its  solvent  action  than  the  freshly  made  reagent.  (Blair.) 


GRAVIMETRIC  METHODS   FOR  DETERMINATION  OF 

CARBON 

The  determination  of  carbon  by  combustion  with  oxygen  is  made  in  two 
general  classes  of  substances:  A.  Steel,  iron  and  in  certain  alloys.  B.  Organic 
compounds.  Carbon  in  steel  and  alloys  is  considered  in  two  forms:  carbide 
or  combined  carbon,  and  graphitic  carbon.  In  organic  substances  carbon  occurs 
principally  combined  with  hydrogen,  oxygen,  and  nitrogen.  For  the  present 
we  will  consider  procedures  for  the  determination  of  carbon  in  steel  and 
alloys. 

The  most  accurate  procedure  for  determination  of  carbon  in  steel,  alloys, 
and  in  other  materials  containing  the  substance  combined  or  free  is  by  com- 
bustion with  oxygen  in  a  furnace  heated  by  gas  or  electricity;  the  carbon  dioxide 
formed  being  absorbed  in  caustic,  and  weighed. 

Apparatus.  Combustion  Furnace.  Although  the  gas  furnace  has 
been  used  more  commonly  on  account  of  gas  being  more  available  than  elec- 
tricity, the  extension  of  generating  electric  plants  makes  it  possible  to  use  electric 
furnaces,  and  these  are  gradually  displacing  those  heated  by  gas,  as  they  are 
more  compact,  easily  manipulated  and  comparatively  simple  in  structure. 

A  simple  electric  furnace  may  be  made  by  wrapping  a  silica  tube  with  a 
thin  covering  of  asbestos  paper,  which  has  been  moistened  with  water.  On 
drying  the  paper  will  cling  to  the  tube.  A  spiral  coil  of  nichrome  wire  (Driver 
and  Harris)  is  wound  around  this  core.  On  a  2-foot  length  of  tube  two  45-foot 
lengths  of  No.  18  wire,  connected  in  parallel,  will  heat  the  tube  to  bright  redness, 
attaching  the  terminals  to  an  ordinary  light  socket.  The  coils  should  be 
covered  with  |-in.  coating  of  alundum  cement.  For  appearance7  sake  as  well 
as  for  protection,  the  tube  is  placed  in  a  large  cylinder  of  sheet  iron,  packed 
around  with  asbestos,  and  is  held  in  position  by  circular  asbestos  boards  placed 
at  the  ends  of  the  large  cylinder.  The  cylinder  is  mounted  on  a  stand. 

Absorption  Apparatus.  A  large  number  of  forms  are  for  sale.  The  Geissler 
and  Liebig  bulbs  have  been  popular  (Figs.  11  and  12),  but  are  now  being  displaced 
by  forms  that  have  less  surface  exposed,  that  are  more  easily  cleaned  and  less 
fragile,  such  as  Gerhardt's,  Vanier's  and  Fleming's  apparatus  (Figs.  ^  13, 
14  and  16).  The  Vanier  and  the  Fleming  absorption  apparatus  are  especially 
to  be  recommended,  on  account  of  their  capacity,  compactness,  efficiency,  in 
handling  gases  passing  at  a  rapid  rate,  and  their  simplicity  of  form. 


96 


CARBON 


Procedure  for  Determining  Carbon  by  Combustion.  Mr.  William  R. 
Fleming  *  describes  his  apparatus  in  the  Iron  Age,  Jan.  1,  1914.  The  following 
abstract  is  taken  from  Eimer  &  Amend's  circular,  edited  by  Mr.  Fleming. 

The  greatest  value  of  this  rapid  method  is  realized  when  it  is  used  to  follow 
a  bath  of  steel  in  the  open-hearth  furnace  preliminary  to  tapping.  It  abolishes 


FIG.  11.— Geissler  Bulb.      FIG.  12.— Liebig  Bulb.      FIG.  13.— Gerhardt  Bulb. 

completely  the  unreliable  and  dangerous  color  carbon.  By  this  method  abso- 
lutely accurate  results  can  be  reported  to  the  open  hearth  ten  minutes  after 
the  drillings  are  received. 

In  principle  this  method  is  not  new;  in  manipulation  it  is  new.  Hereto- 
fore chemists  have  been  laboring  under  the  impression 
that  the  flow  of  gas  during  a  combustion  must  not  exceed 
a  certain  snail-like  pace.  This  false  impression  has  been 
injected  into  the  minds  of  chemists  by  a  few  who  were 
supposed  to  have  investigated  the  matter.  The  truth  is 
that  the  faster  oxygen  is  fed  to  burning  steel  the  more 
complete  the  combustion  will  be.  The  rate  of  current  is 
limited  by  the  efficiency  of  the  apparatus  used  to  absorb 
the  evolved  carbon  dioxide. 

The  Apparatus  Described.  The  combustion  train  is 
shown  complete  in  Fig.  15.  The  oxygen  is  delivered  to 
the  train  through  a  regulating  and  reducing  valve  such  as 
is  used  for  welding.  The  regulating  valve  is  not  essen- 
tial, yet  any  chemist  who  uses  one  will  appreciate  its  con- 
venience, especially  in  this  method.  Its  convenience  will  be 
explained  later.  K  is  a  mercury  pressure  gauge.  It  serves 
as  a  guide  during  the  combustion  and  is  an  essential  piece 
of  apparatus.  The  graduated  column  is  6  ins.  high  and  is 
divided  into  eighths.  P  is  a  washing  bottle  containing  caustic  potash  solution. 
Filled  to  the  mark  indicated  with  50%  solution  it  will  serve  for  at  least  1000  com- 
bustions. It  is  used  solely  to  indicate  the  flow  of  gas,  not  to  purify  it.  If  the 
chemist  desires  he  may  omit  this  from  the  train.  T  is  a  calcium  chloride  jar. 
It  is  filled  to  the  mark  indicated  with  finely  divided  calcium  chloride,  about  pea  size, 
retaining  all  the  dust.  A  layer  of  asbestos  is  formed  over  the  chloride  and  the 
remaining  space  filled  with  soda  lime.  The  glass  tubing  leading  from  the  jar  is 
loosely  packed  for  a  distance  of  several  inches  with  asbestos.  This  prevents  any 
soda  lime  dust  being  carried  into  the  combustion  tube.  G  is  a  mercury  valve  like 
that  used  in  Johnson's  train.  It  is  used  solely  to  maintain  an  atmosphere  of 
1  Metallurgist,  Andrews  Steel  Company,  Newport,  Ky. 


FIG.  14. — Vanier 
Bottle. 


CARBON 


97 


pure  oxygen  in  the  purifying  train,  a  condition  essential  to  accurate  results. 
It  is  not  used  to  prevent  carbon  dioxide  backing  into  the  purifying  train,  of  which 
there  is  not  the  remotest  possibility. 

The  combustion  tube  is  the  ordinary  fused 
silica  tube  glazed  on  the  inside  only.  The  tube 
is  30  ins.  long  with  inside  diameter  of  from  J 
to  1  in.  One  tube  of  30  ins.  will  serve  twice  as 
long  as  one  of  24  ins.  It  is  loosely  packed  with 
asbestos  for  a  distance  of  6  ins.  at  the  exit  end, 
and  3  ins.  is  allowed  to  project  from  the  furnace. 
For  about  the  first  100  combustions,  the  com- 
bustion boat  is  pushed  close  against  the  asbestos. 
The  portion  of  the  tube  immediately  above  this 
will  become  coated  with  iron  oxide.  The  asbestos 
is  then  moved  up  so  that  it  covers  this  portion 
of  the  tube  and  a  fresh  area  exposed  to  the 
spraying  oxide.  In  this  manner  one  tube  can  be 
made  to  serve  600  combustions  or  even  more. 
Both  platinum  and  nickel  cylinders  have  been 
used  inside  the  tube  to  protect  it  from  the  spraying 
oxide,  but  it  is  doubtful  whether  this  practice  pays. 
These  cylinders  are  not  used  in  this  laboratory 
because  it  is  believed  that  they  delay  incipient 
combustion  for  at  least  thirty  seconds. 

The  Furnace  and  Combustion  Tube.  The 
furnace  used  is  one  of  the  ordinary  resistance 
type.  It  is  constantly  maintained  at  a  tem- 
perature of  1000°  C.  This  temperature  is  verified 
daily  by  the  use  of  a  pyrometer.  Many  claim  to 
be  expert  at  judging  temperatures,  but  none  are 
expert  enough  to  be  without  a  pyrometer.  The 
two-way  stop  following  the  combustion  tube  will 
be  found  very  convenient  when  it  is  not  desirable 
to  pass  the  current  through  the  jars  Z  and  0. 

Z  is  filled  with  20-mesh  zinc.  Once  filled  it 
will  serve  for  several  thousand  combustions.  As 
a  matter  of  fact  it  is  included  in  this  train  as 
a  filter.  If  nickel  boats  and  aluminum  are  used 
the  chemist  may  omit  this  zinc  jar  from  the 
train,  for  with  all  ordinary  grades  of  steel  it  serves 
no  purpose. 

0  is  the  phosphoric  anhydride  jar.  A  little 
asbestos  is  placed  in  the  lower  part  just  above 
the  lower  stopper.  The  remaining  space  in  the 
jar  is  completely  filled  with  phosphoric  anhydride. 
The  upper  stopper  is  packed  tightly  enough  to 
prevent  any  powder  being  swept '  into  the  weigh- 
ing apparatus.  As  the  anhydride  liquefies  it  ^^3^ 
passes  down  into  the  lower  stopper,  where  it  can 
be  removed  conveniently  without  disturbing  the  anhydride  above  it.  Likewise 


98  CARBON 

the  anhydride  can  be  replenished  by  removing  only  the  upper  stopper.  The 
jar  need  not  be  washed  oftener  than  once  in  500  combustions.  When  filled 
with  anhydride,  fresh  reagent  need  not  be  added  for  at  least  150  combustions. 
After  each  combustion  the  jar  should  be  given  a  few  sharp  taps  with  the  hand 
to  prevent  canals  being  formed. 

Details  of  the  Absorption  Apparatus.  The  absorption  apparatus,  shown 
in  detail  in  Fig.  16,  has  been  modified  slightly  at  the  sug- 
gestion of  Henry  G.  Martin,  of  the  Railway  Steel  Spring 
Company,  Chicago  Heights,  111.  This  apparatus  is  no  more 
efficient  than  the  old  style,  but  it  is  much  more  convenient 
and  less  troublesome.  In  the  old-style  tube  the  anhydride 
would  liquefy  after  several  days  and  require  replenishing. 
To  overcome  this,  Mr.  Martin  suggested  using  separate  cham- 
bers for  the  anhydride  and  soda  lime,  so  that  communication 
could  be  broken  when  the  tube  was  standing  idle.  The  tube 
shown,  Fig.  16,  is  Fleming's  modification  of  Mr.  Martin's 
suggestion.  When  properly  filled  this  tube  will  serve  for  at 
least  70  combustions  when  operating  on  1 .5  grams  of  sample 
containing  1.03%  carbon. 

The  anhydride  in  the  upper  chamber  serves  for  at  least 
300  combustions.    Soda  lime,  placed  in  the  lower  tube  in  alter- 
.  nate  layers  (£  in.)  of  the  different  meshes,  has  proven  a  very 

Absorption11^    convenient  and  desirable  reagent.    The  12-mesh  soda  lime  for 
paratus.  nitrogen  can  also  be  used  with  excellent  results.     If  this  is 

employed,  part  of  it  should  be  ground  to  about  60-mesh  and 
alternate  layers  of  fine  and  coarse  used. 

It  is  exceedingly  important  that  the  tube  be  loaded  with  alternate  layers 
of  coarse  and  fine  reagent,  for,  if  the  12-mesh  reagent  is  transferred  directly 
from  the  bottle  to  the  absorption  tube,  the  latter  will  fail  to  be  effective  for 
more  than  30  combustions  and  in  some  cases  less.  The  reason  for  this  is  evident. 
The  lower  stopper  is  packed  loosely  with  asbestos,  also  the  lower  portion  of  the 
soda  lime  chamber  just  above  the  stopper.  Beginning  with  a  layer  of 
12-mesh  soda  lime,  the  entire  chamber  is  filled  with  alternate  layers  of  fine  and 
coarse  reagent.  The  small  diameter  of  the  anhydride  chamber  is  packed  with 
asbestos  and  the  remaining  space  filled  with  phosphoric  anhydride.  Finally, 
the  upper  stopper  is  packed  with  asbestos.  The  anhydride  chamber,  filled  as 
indicated,  will  not  require  refilling  for  at  least  300  combustions.  It  is  not 
necessary  to  turn  the  chamber  to  break  communication  while  the  tubes  are 
idle,  for  the  packing  of  the  small  diameter  with  asbestos  prevents  the  absorption 
of  moisture  from  the  soda  lime.  The  tubes  must  be  used  in  pairs,  so  that  one 
serves  as. a  tare  in  weighing  the  other.  A  pair  of  tubes  assures  the  operator 
of  at  least  140  combustions.  A  glass  or  rubber  tubing  about  12  ins.  long  serves 
as  a  guard  for  the  absorption  tube.  It  connects  the  bottle,  Pi,  which  is  used 
to  indicate  flow  of  gas. 

The  use  of  clay  boats  has  been  abandoned  in  favor  of  nickel  boats  filled  with 
alundum.  These  are  greatly  superior  to  clay  boats  in  every  conceivable  way. 
The  alundum  is  labeled  as  being  free  from  carbon,  but  this  is  not  true.  In  fact, 
some  of  it  contains  considerable  carbon.  It  should  always  be  burned  in  oxygen 
at  1000°  before  using.  The  boats  are  formed  out  of  22-gauge  pure  sheet  nickel. 
One  boat  will  serve  for  about  100  to  150  combustions,  some  more,  some  less. 


CARBON  99 

Details  of  the  Analysis.  The  furnace  being  at  1000°,  the  two  freshly 
prepared  absorption  tubes  are  placed  in  the  train  and  oxygen  run  through  at 
the  rate  of  300  cc.  per  minute  for  fifteen  minutes.  This  insures  the  displace- 
ment of  all  air  from  the  purifying  train  as  well  as  the  absorption  tubes.  Remove 
one  absorption  tube  from  the  train  and  turn  on  the  oxygen  until  the  mercury 
stands  at  about  2  ins.  The  rate  of  current  is  then  measured  by  inverting  a 
graduated  cylinder  filled  with  water.  Several  trials  will  establish  a  rate  of 
about  325  cc.  per  minute.  Note  the  reading  of  the  column  of  mercury  at  this 
rate  and  subsequently,  when  using  the  same  absorption  tube,  maintain  this 
same  pressure  in  the  train  and  the  rate  of  flow  will  be  325  cc.,  the  rate  during  all 
combustions.  Shut  off  the  oxygen  and,  when  it  comes  to  a  slow  bubbling 
through  Pi,  close  the  upper  stopper  of  the  absorption  tube.  Disconnect  it  from 
the  train,  but  do  not  close  the  lower  stopper  for  about  five  seconds  after  dis- 
connection. Weigh  against  its  mate  as  a  tare.  It  is  now  ready  for  the  first 
combustion. 

Weigh  1.5  grams  of  drillings,  preferably  thin,  curly  drillings  from  a  twist 
drill,  and  spread  out  in  the  nickel  boat  which  is  half  filled  with  alundum.  Place 
the  absorption  tube  in  the  train  and  place  its  mate  beside  it.  With  the  oxygen 
flowing  about  100  cc.  per  minute,  the  drillings  are  pushed  into  the  combustion 
tube.  The  current  is  immediately  run  up  to  the  desired  pressure,  which  gives 
325  cc.  per  minute.  The  regulator  will  do  the  rest.  It  will  feed  the  oxygen 
automatically  to  the  burning  steel.  As  a  rule  the  drillings  are  entirely  burned 
one  and  one-half  minutes  after  insertion.  Continue  the  flow  of  oxygen  for 
three  and  one-half  minutes  more  (five  minutes,  total  time)  and  disconnect 
as  before  the  absorption  tube.  Weigh  immediately.  The  result  will  be  accurate 
and  reliable.  Whether  determining  carbon  in  a  standard  steel,  where  the 
greatest  accuracy  is  required,  or  in  a  bath  test,  the  time  required  is  always 
five  minutes. 

The  weight  of  the  boat,  plus  refractory  lining,  should  be  kept  as  low  as 
possible,  so  as  not  to  introduce  too  much  cold  material  into  the  combustion 
tube.  The  boats  used  in  this  laboratory  are  |  in.  wide,  i  in.  deep  and  3  ins.  long. 
Sheet  nickel  varies  in  percentage  of  carbon.  As  a  rule,  a  nickel  boat  must  be 
ignited  in  oxygen  at  1000°  for  one  to  two  hours. 

There  seems  to  be  a  difference  of  opinion  concerning  the  physical  condition 
of  the  steel  after  burning,  some  chemists  believing  that  inaccurate  results  are 
obtained  if  the  drillings  have  fused  during  combustion.  Others  maintain  that 
complete  fusion  of  the  drillings  is  essential  to  accurate  result.  If  drillings 
which  happen  to  be  a  little  thick  are  used,  low  results  are  obtained  unless  these 
are  perfectly  fused. 

Graphitic  Carbon 

In  Iron  and  Steel.  The  sample  of  1  gram  of  pig  iron  or  10  grams  of 
steel  is  treated  with  15  cc.  of  nitric  acid  (sp.gr.  1.2),  per  gram  of  sample  taken. 
When  all  the  iron  has  dissolved,  the  graphite  is  allowed  to  settle  and  the  super- 
natant liquid  decanted  onto  an  ignited  asbestos  filter,  using  either  a  perforated 
boat,  Fig.  17,  or  a  filtering  tube.  The  residue  is  transferred  to  the  filter, 
and  washed  thoroughly  with  hot  water.  It  is  treated  with  hot  caustic 
solution  (sp.gr.,  1.1),  washed  thoroughly  again  with  hot  water,  then  with  a 
little  dilute  hydrochloric  acid,  and  finally  with  hot  water.  The  carbon  is 
now  burned  by  one  of  the  procedures  given— the  oxidation  in  the  combustion 


100 


CARBOIST 


furnace  being  recommended.    The  C02  is  absorbed  in  caustic  and  estimated 
according  to  the  standard  procedure  given  for  carbon. 

C02X 0.2727=  graphitic  carbon. 

The  perforated  boat,  shown  in  the  cut,  fits  snugly 
into  the  receptacle  below.  Sufficient  asbestos  is  poured 
into  the  boat  to  form  a  film  over  the  bottom.  A  seal 
is  made  around  the  boat  with  additional  asbestos,  the 
apparatus  having  been  inserted  in  a  rubber  stopper 
in  the  neck  of  a  suction  flask  and  suction  applied. 

The  apparatus  is  recommended  by  Blair  for  com- 
bustion of  graphitic  carbon  or  of  total  carbon  liberated 
from  iron  or  steel  by  the  cupric  potassium  chloride 
for  CMbon  Determina-  "«th«i.  The  boat  may  be  placed  directly  in  the 
tion.  combustion  tube  and  the  carbon  oxidized  as  usual. 


The  Shimer  Combustion  Apparatus 1 

The  apparatus,  designed  for  the  rapid  determination  of  iron  and  steel,  is 
in  general  applicable  to  the  same  class  of  chemical  operations  as  is  the  com- 
bustion tube  of  platinum,  silica,  or  porcelain.  It 
offers  the  advantage  of  neatness,  reduction  in  the 
number  of  parts  to  be  handled,  diminished  con- 
sumption of  gas,  and  increased  ease  of  manipula- 
tion. The  simplified  form,  shown  in  the  cut,  Fig. 
18,  enables  the  use  of  the  standard  form  of  plati- 
num crucible,  A,  with  its  inner  wall  ground  to  fit  a 
tapered  nickel,  water-jacketed  stopper,  B.  The  rub- 
ber jacket  of  the  original  type  is  eliminated  and  a 
detachable  nickel  reinforcing  ring,  C,  at  the  top  of 
the  crucible  serves  the  "double  purpose  of  completing 
the  security  of  the  seal  and  as  a  support  for  the 
apparatus. 

Water  is  circulated  through  the  stopper  through  FIG.  18.— Shimer  Combustion 
the  tubes  c  and  d.  The  current  of  oxygen  passes  Apparatus,  Simplified  Form, 
through  a  into  the  crucible,  oxidizing  the  material 

within  the  crucible,  which  is  heated  to  red  heat  with  a  burner  placed  below  it. 
The  carbon  dioxide  formed  passes  through  6  to  the  absorption  train.  The 
remainder  of  the  apparatus  for  the  determination  is  the  same  as  is  used  with 
the  combustion  tube.  An  asbestos  shield  protects  the  upper  portion  of  the 
outfit,  the  crucible  fitting  snugly  in  a  hole  in  the  asbestos  board. 


Combined  Carbon 

Indirect  Method.  The  excess  of  carbon  remaining  when  the  graphitic 
carbon  is  subtracted  from  total  carbon  (in  iron  and  steel),  is  calculated  as  com- 
bined carbon.  This  difference  method  is  generally  accepted  as  being  the  most 
accurate  for  estimation  of  combined  carbon. 


1  Courtesy  of  Baker  Platinum  Works. 


CARBON  101 

NOTES.  In  chromium,  tungsten  and  titanium  steels  a  temperature  of  1500°  C 
is  necessary  to  oxidize  the  carbon  by  direct  combustion  for  thirty  minutes  (J  R' 
Cam  and  H.  E.  Cleaves,  J.  Wash.  Acad.  Sci.,  194,  4,  393-397.) 

Carbon  in  Soils.  One  to  3  grams  of  60-mesh  sample  is  treated  with  a  solu- 
tion of  3.3  grams  CrO3  +  10  cc.  H2O  and  50  cc.  cone.  H2SO4  (1.84).  The  evolved 
CO2  is  absorbed  in  standard  caustic  and  titrated  with  acid,  phenolphthalein  and  methvl 
orange  being  used  as  indicators.  (J.  Ind.  Eng.  Chem.,  1914,  6,  843-846.) 

DETERMINATION  OF  CARBON  IN  ORGANIC  SUBSTANCES 

Combustion  of  Organic  Substances  Free  of  Nitrogen,  Halogens, 
Sulphur,  and  the  Metals 

The  following  modification  of  the  procedure  described  for  determination 
of  carbon  in  iron  and  steel  is  applicable  to  the  determination  of  carbon  in  organic 
substances  free  from  the  substances  mentioned  above. 

Apparatus.  This  is  practically  the  same  as  that  shown  in  Fig.  19,  with  the 
exceptions  that  copper  plugs  may  be  used  to  advantage  in  place  of  the  plati- 
num plugs.  In  the  absorption  end  of  the  train  a  calcium  chloride  tube  is 
preferred.  The  calcium  chloride  should  have  been  saturated  with  dry  C02 
gas,  the  excess  of  which  has  been  removed  by  a  current  of  pure  air.  This  tube 

Copper 
Platinum          Boat.^    Platinum   Oxide     .'Platinum 


r^SSsBsirrr^ 


FIG.  19. — Diagrammatic  Sketch  of  Combustion  Tube. 

is  weighed  as  well  as  the  potash  bulb,  the  calcium  chloride  retaining  the  water 
formed  by  the  combustion  of  the  hydrogen  of  the  organic  substance,  which 
is  thus  determined. 

The  organic  substance,  if  a  solid,  is  introduced  into  the  combustion  boat 
directly;  if  it  is  a  liquid,  it  is  held  in  a  bulb  blown  in  a  capillary  tube.  One 
end  of  the  tube  is  sealed  and  a  bulb  blown.  When  cool,  the  tube  is  weighed,  and 
the  material  then  introduced  by  first  warming  the  bulb  and  then  inserting  the 
open  end  of  the  tube  into  the  liquid  to  be  examined.  By  cooling  the  bulb,  liquid 
is  drawn  into  the  tube.  The  end  is  wiped  off,  and  the  liquid  expelled  from 
the  capillary  by  gently  heating  this  portion.  The  end  is  now  sealed  if  the 
liquid  is  volatile,  otherwise  it  is  left  open,  and  the  tube  is  weighed.  The 
increased  weight  is  due  to  the  organic  substance.  The  tip  of  the  capillary  is 
now  broken,  if  sealing  was  necessary,  by  means  of  a  file.  The  tube  containing 
the  sample  is  placed  in  the  boat,  the  open  end  of  the  capillary  pointing  toward 
the  open  end  of  the  combustion  tube.  After  connecting  up  the  apparatus, 
the  copper  oxide  end  of  the  tube  is  heated  to  redness  and  oxygen  slowly  passed 
through  the  tube  at  such  a  rate  that  the  bubbles  in  the  potash  bulb  can  be 
readily  counted.  The  entire  tube  is  now  heated  and  remaining  operation  is 
the  same  as  has  been  described  for  iron  and  steel  combustion. 

The  gain  of  weight  of  the  calcium  chloride  tube  is  due  to  water  formed  by 
the  combustion  of  hydrogen  of  the  compound,  that  of  the  potash  bulb  to  the 
carbon. 

H2OX0.1121=H, 
C02X  0.2727=0. 


102  CARBON 

NOTE.  The  oxygen  gas  should  be  free  from  hydrogen.  A  preheat  er,  placed 
before  the  purifying  tubes  of  the  train,  causes  the  combustion  of  the  hydrogen  and 
the  absorption  of  the  water  formed  before  the  gas  enters  the  combustion  tube. 

Determination  of  Carbon  and  Hydrogen  in  Nitrogenous 

Substances 

A  modification  of  the  first  procedure  described  for  determinations  of  carbon 
and  hydrogen  in  organic  substances  must  be  made,  since  from  substances 
containing  nitrogen,  nitroso  and  nitro  compounds,  oxides  of  nitrogen  are  formed 
which  would  be  absorbed  in  the  calcium  chloride  and  potash  bulbs,  giving  high 
results  for  hydrogen  and  carbon.  To  overcome  this  difficulty,  a  copper  spiral, 
that  has  been  reduced  (See  note  below)  is  placed  in  the  front  end  of  the 
combustion  tube  (to  the  right  in  Fig.  19)  to  reduce  the  oxides  of  nitrogen  to 
nitrogen. 

NOTE.  Reduction  of  copper  spiral  may  be  accomplished  as  follows:  The  copper 
spiral  is  prepared  by  rolling  together  a  piece  of  copper  gauze  about  10  centimeters 
wide,  making  it  as  large  as  will  conveniently  pass  into  the  combustion  tube.  The 
spiral  is  heated  till  it  glows  by  holding  it  in  a  large  gas  flame,  and  while  still 
hot  it  is  dropped  into  a  test-tube  containing  1  or  2  cc.  of  methyl  alcohol  or  ether. 
This  quickly  boils  away,  igniting  at  the  end  of  the  tube.  The  copper  is  completely 
reduced  to  bright  metallic  copper.  The  spiral  is  taken  out  with  a  pair  of  crucible 
tongs  and  dried  by  quickly  passing  it  through  a  flame  a  few  times,  and  while  it  is 
still  warm  it  is  introduced  into  the  front  of  the  combustion  tube.1 

The  substance  is  introduced  into  the  tube  and  the  connections  made.  The 
copper  oxide  spiral,  that  was  pushed  after  the  boat,  is  heated,  and  then  the 
reduced  spiral  (right  end  of  tube).  The  oxide  near  the  boat,  and  finally 
the  entire  tube  is  heated  to  a  red  heat.  When  the  bubbles  cease  to  show  in 
the  potash  bulb,  the  stopcock  is  opened  to  the  oxygen-purifying  train  and  a 
slow  flow  of  oxygen  turned  on,  the  gas  allowed  to  pass  through  the  tube  until 
it  can  be  detected  with  a  glowing  splinter  at  the  exit  of  the  absorption  end  of 
the  apparatus. 

If  the  substance  is  difficult  to  burn,  it  is  mixed  with  freshly  ignited  (cold) 
copper  oxide,  which  assists  combustion. 

The  remainder  of  the  operation  is  the  same  as  has  been  described. 

Organic  Substances  Containing  Halogens 

The  procedure  is  the  same  as  that  described  for  nitrogenous  substances 
with  the  exception  that  a  silver  spiral  is  used  in  place  of  the  reduced  copper 
spiral.  The  heating  of  this  spiral*  should  be  between  180  and  200°  C.  (not 
over  200°). 

Organic  Substances  Containing  Sulphur 

These  are  best  ignited  with  sodium  peroxide  and  the  carbonate  formed  is 
determined  by  the  procedure  given  for  carbon  dioxide  in  carbonates. 

The  Wet  Combustion  Process  for  Determination  of  Carbon 

The  method  depends  upon  the  oxidation  of  carbon  to  carbon  dioxide  when 
the  powdered  material  is  digested  with  a  mixture  of  concentrated  sulphuric 
acid  and  chromic  acid,  or  potassium  dichromate,  or  permanganate.    The  pro- 
1  Treadwell  and  Hall,  "Quantitative  Analysis."     John  Wiley  &  Sons. 


CARBON  103 

cedure  is  applicable  to  oxidation  of  free  carbon,  carbon  combined  in  organic 
substances  and  in  certain  instances  to  carbon  combined  with  metals,  where 
the  substance  may  be  decomposed  by  the  action  of  the  acids.1  It  is  of  value 
in  determination  of  carbonates  in  presence  of  sulphides,  sulphites,  thiosulphates 
and  nitrites,  which  would  vitiate  results  were  they  not  oxidized  to  more  stable 
forms,  from  passing  into  the  potash  bulb  with  the  carbon  dioxide. 

Apparatus.  The  apparatus  is  identical  with  that  used  for  determining 
carbon  dioxide  in  carbonates,  Fig.  20,  with  the  exception  that  in  place  of  the 
acid  bulb  nearest  the  decomposition  flask  two  bulbs  are  placed.  The  first  of 
these  contains  a  strong  solution  of  chromic  and  sulphuric  acids,  the  second 
is  filled  with  glass  beads  moistened  with  chromic  acid  solution.  Following  this 
is  the  drying  bulb  containing  concentrated  sulphuric  acid  and  finally  the 
absorption  apparatus,  as  shown  in  the  illustration. 

Procedure.  0.2  to  1  gram  of  the  powdered  material,  fine  drillings,  free 
carbon,  or  organic  substance  is  placed  in  the  decomposition  flask.  If  the 
material  is  apt  to  pack  it  is  advisable  to  mix  with  it  pure  ignited  sea-sand  to 
prevent  this.  Five  to  10  grams  of  granular  potassium  dichromate  are  added 
and  the  apparatus  swept  free  of  carbon  dioxide  by  passing  purified  air  through 
it  before  attaching  the  absorption  apparatus.  The  potash  bulb  is  now  weighed, 
using  a  counterbalance  bulb  and  following  the  precautions  given  in  the  dry- 
combustion  method.  The  bulb  is  attached  to  the  train. 

Oxidation.  Concentrated  sulphuric  acid  placed  in  the  acid  funnel,  attached 
to  the  decomposition  flask,  is  allowed  to  flow  down  on  the  sample  until  the 
funnel  is  almost  empty;  the  stop-cock  is  then  closed.  A  flame  is  placed  under 
the  flask,  when  the  vigorous  action  has  ceased,  and  the  material  gently  heated 
until  the  reaction  is  complete  and  the  organic  matter  or  carbon  completely 
oxidized. 

The  apparatus  is  now  swept  free  of  residual  C02  by  applying  suction,  the  gas 
being  completely  absorbed  by  the  potash,  o:  the  soda  lime  reagent. 

The  increase  of  weight  of  the  absorption  bulb  is  due  to  carbon  dioxide. 

C02X0.2727=C. 

NOTE.  The  following  additional  purifiers  are  frequently  advisable:  (a)  an  absorp- 
tion bulb  containing  silver  sulphate  to  absorb  chlorine  and  vapors  from  sulphur 
compounds;  (6)  a  capillary  tube  of  silica  or  platinum  heated  to  a  dull  redness  to  oxidize 
any  hydrocarbons,  carbon  monoxide,  etc.,  that  may  be  evolved  and  imperfectly  oxidized 
by  the  chromic  acid. 

DETERMINATION   OF  CARBON   DIOXIDE  IN  CARBONATES 

The  method  is  applicable  for  determination  of  carbon  dioxide  in  limestone, 
dolomite,  magnesite,  strontianite,  witherite,  spatic  iron  ore,  carbonates  of  sodium, 
and  potassium,  bicarbonates  in  baking  powder,  carbon  in  materials  readily 
oxidized  to  C02  chromic  sulphuric  acid  mixture.  The  procedure  depends  upon 
the  evolution  of  carbon  dioxide  by  a  less  volatile  acid,  or  the  oxidation  of  carbon. 
The  C02  is  absorbed  in  caustic  and  weighed. 

Apparatus.  The  illustration  shows  the  apparatus  found  suitable  for  this 
determination.  It  is  Knorr's  apparatus  slightly  modified.  The  absorption 
bulb  or  bottle  should  be  one  that  will  effectively  absorb  carbon  dioxide  entering 

1  Not  applicable  for  determining  carbon  in  ferro-silicon,  ferro-chrome  or  tungsten 
steel. 

CALIFORNiA   SOLLEil 


104 


CARBON 


at  a  rapid  rate.     The  Vanier  or  the    Fleming   forms    is  satisfactory  for   this 
purpose. 

Procedure.  A  sample  weighing  0.5  to  2  grams,  according  to  the  carbon 
dioxide  content,  is  placed  in  the  dry  decomposition  flask  (C).  The  flask  is 
closed  by  inserting  the  funnel  tube  (B)  fitted  with  the  soda  lime  tube  (A),  and 
connected  by  means  of  a  condenser  to  the  train  for  removing  impurities  from 
carbon  dioxide,  leading  to  the  absorption  bulb,  as  shown  in  Fig.  20. 


Glass  wool 


CoCI2 


Glass  wool 


4  FLEMING'S 


,G 

-  Soda  L  ime 

Glass  wool 


FLEMING'S  C02 
Apparatus 


-£Mfo  Lime  to  remove 

'"• J .  ~ •  I '- '  '•]  from  the  air 

-'•Gloss  wool 


Suction 


''"/""///"//////^^^ 

FIG.  20. — Apparatus  for  Determining  Carbon  Dioxide. 

The  apparatus  is  swept  out  with  a  current  of  dry,  purified  air  before  attaching 
the  weighed  absorption  bottle.  This  is  accomplished  by  applying  gentle  suction 
at  the  end  of  the  purifying  train.  The  absorption  apparatus  is  now  attached 
(Fleming  absorption  apparatus  is  shown  in  the  illustration).  The  tube  (B) 
is  nearly  filled  with  dilute  sulphuric  acid  (1  :  3),  the  stop-cock  (Bf)  being  closed. 
The  soda  lime  tube  is  now  inserted  into  place  as  shown  in  the  cut.  The  acid 
in  (B)  is  now  allowed  to  run  slowly  down  on  the  sample  at  a  rate  that  evolves 


CARBON  105 

gas  not  too  rapidly  to  be  absorbed;  1  to  2  cc.  of  acid  being  retained  in  (B)  to 
act  as  a  seal,  the  stop-cock  (B')  being  then  closed. 

When  the  violent  action  has  ceased,  the  solution  in  (C)  is  heated  to  boiling 
and  boiled  for  about  three  minutes.  If  the  sample  is  baking  powder,  or  con- 
tains organic  matter,  the  decomposition  flask  is  protected  from  excessive  heat  by 
placing  a  casserole  of  hot  water  under  it.  This  prevents  charring  of  the  starch 
or  organic  matter,  which  would  be  apt  to  occur  if  the  direct  flame  was  used. 
Gentle  suction  is  now  applied  to  the  absorption  end  of  the  apparatus  and  the 
stop-cock  (B')  opened,  allowing  the  remainder  of  the  acid  to  flow  into  the  flask  (C) 
and  admitting  a  current  of  air,  purified  by  passing  through  the  soda  lime  "in 
(A).  The  suction  should  be  gentle  at  first,  and  then  the  speed  of  the  flow 
increased  to  the  full  capacity  of  the  absorption  bottle.  A  fairly  rapid  current 
is  preferred  to  the  old-time  procedure  of  bubbling  the  gas  through  the  apparatus 
at  a  snail-like  pace,  but  discretion  should  be  used  in  avoiding  a  too  rapid  flow. 

In  the  analysis  of  baking  powders,  where  foaming  is  apt  to  occur,  the  decom- 
position flask  should  be  of  sufficient  capacity  to  prevent  foaming  over.  A  small 
flask  is  generally  to  be  preferred  for  obvious  reasons.  By  gently  heating  to 
boiling  during  the  passage  of  the  air,  steam  assists  in  expelling  any  residual 
C02  in  the  flask.  When  the  passage  of  air  is  rapid,  this  boiling  should  be  dis- 
continued. 

The  increase  of  weight  of  the  absorption  bottle  is  due  to  the  carbon  dioxide 
of  the  sample.  This  procedure  gives  total  C02. 

Determination  of  Carbon  Dioxide  by  Measuring  the  Gas 

Fairly  accurate  results  may  be  obtained  by  measuring  the  gas  evolved.  A 
large  cylindrical  tube  having  a  capacity  of  about  1100  cc.  is  used.  The  tube 
is  graduated  from  1000  cc.  to  0  at  the  upper  portion  of  the  cylinder;  a  space  of 
about  100  cc.  remains  at  the  upper  portion.  A  tube  extending  from  a  little 
above  the  0  graduation  to  the  bottom  of  the  cylinder  carries  out  the  water  as 
the  gas  is  admitted. 

To  make  the  run,  the  cylinder  is  filled  to  the  mark  0  with  saturated  salt 
solution.1  It  is  now  connected  to  a  condenser.2  Twenty-five  cc.  of  saturated 
salt  solution  are  admitted  to  the  decomposition  flask,  and  the  generated  gas 
measured  by  the  water  displacement  in  the  tube  described.  Calculations  are 
made  after  reduction  to  standard  conditions.  5.1  cc.  C02  at  0°  C.  and  760 
mm.  weigh  0.01  gram. 

Residual  Carbon  Dioxide 

This  is  the  C02  remaining  after  baking  powder  has  been  treated  with  water 
and  the  evolved  CO2  expelled  by  warming. 

The  procedure  recommended  by  the  U.  S.  Department  of  Agriculture  is  as 
follows  :3 

1  H.  W.  Brubacker,  Jour.  Ind.  Eng.  Chem.,  1915,  7,  432. 

2  The  nitrometer  may  be  used  in  place  of  the  cylinder  and  atmospheric  condi- 
tions obtained  as  usual.    Formula  for  reduction  to  760  millimeters  and  0°  C.: 

(P-tp) 
760(1 +.003670* 

3  Bureau  of  Chem.  Bulletin  No.  107. 


106 


CARBON 


Weigh  2  grams  of  baking  powder  into  a  flask  suitable  for  the  subsequent 
determination  of  carbonic  acid,  add  20  cc.  of  cold  water,  and  allow  to  stand 
twenty  minutes.  Place  the  flask  in  a  metal  drying  cell  surrounded  by  boiling 
water  and  heat,  with  occasional  shaking,  for  twenty  minutes. 

To  complete  the  reaction  and  drive  off  the  last  traces  of  gas  from  the  semi- 
solid  mass,  heat  quickly  to  boiling  and  boil  for  one  minute.  Aspirate  until  the 
air  in  the  flask  is  thoroughly  changed,  and  determine  the  residual  carbon  dioxide 
by  absorption,  as  described  under  total  carbonic  acid. 

The  process  described,  based  on  the  methods  of  McGill  and  Catlin,  imitate, 
as  far  as  practicable,  the  conditions  encountered  in  baking,  but  in  such  a  manner 
that  concordant  'results  may  be  readily  obtained  on  the  same  sample,  and  com- 
parable results  on  different  samples. 

Available  Carbon  Dioxide 

The  residual  is  subtracted  from  the  total,  and  the  difference  taken  as  avail- 
able C02. 

Determination  of  Carbon  Dioxide  by  Loss  of  Weight 

An  approximate  estimation  of  the  carbon  dioxide  in  carbonates — baking 
powders,  bicarbonate  of  soda,  limestone,  etc.,  may  be  obtained  by  the  loss  of 
weight  of  the  material  when  treated  with  a  known  weight  of  acid. 


FIG.  21.— Schroetter's  Alkalimeter.        FIG.  22.— Mohr's  Alkalimeter. 

Various  forms  of  apparatus  are  used  for  this  determination.  The  Schroetter 
and  Mohr  types  are  shown,  Figs.  21  and  22. 

About  0.5  to  1.0  gram  of  sample  is  taken  and  placed  in  the  bottom  of  the 
flask,  dilute  hydrochloric  and  strong  sulphuric  acids  then  placed  in  the  bulbs 
as  indicated  in  the  illustrations.  The  apparatus  is  weighed  as  it  is  thus  charged. 
The  hydrochloric  acid  is  now  allowed  to  flow  down  on  the  carbonate  and  the 
stopper  closed.  The  evolved  gas  passes  through  the  strong  sulphuric  acid, 
which  absorbs  the  moisture.  After  the  vigorous  action  has  subsided  the  appa- 


CARBON  107 

ratus  is  placed  over  a  low  flame  and  the  solution  heated  to  boiling  and  boiled 
very  gently  for  about  three  minutes.  C02-free  air  is  aspirated  through  the 
solution  to  expel  the  last  traces  of  C02,  by  applying  gentle  suction  at  a  and 
opening  6,  the  air  being  purified  by  passing  through  soda  lime.  The  apparatus 
is  again  weighed  and  the  loss  of  weight  taken  as  the  C02  of  the  material. 

Available  C02  in  baking  powder  may  be  determined  by  substituting  water 
in  place  of  hydrochloric  acid. 

VOLUMETRIC   METHODS    FOR  THE   DETERMINATION    OF 

CARBON 

Total  Carbon.    Absorption  of  Carbon  Dioxide  in  Barium  Hydroxide 

The  carbon  dioxide  evolved  by  oxidation  of  the  material  by  dry  combustion 
with  oxygen  or  by  oxidation  with  chromic  sulphuric  acid  mixture  is  absorbed 
in  barium  hydroxide,  free  from  carbonate,  and  the  precipitated  barium  car- 
bonate titrated  with  standard  hydrochloric  acid. 

Procedure.  The  essential  difference  in  this  method  from  those  already 
described  under  the  gravimetric  methods  is  in  the  fact  that  a  perfectly  clear 
saturated  solution  of  barium  hydroxide  is  used  for  absorption  of  the  carbon 
dioxide  in  place  of  caustic  potash.  Considerable  care  must  be  exercised  to 
prevent  contaminating  the  reagent  with  carbonate.  The  solution  is  drawn 
by  suction  through  a  siphon,  dipping  below  the  surface  of  the  reagent,  into  the 
absorption  tube,  which  should  be  of  such  construction  that  the  material  may 
readily  be  poured  out.  After  absorption  of  the  C02  gas,  the  apparatus  is  dis- 
connected and  the  excess  barium  hydroxide  neutralized  with  dilute  hydro- 
chloric acid  (1:4)  using  phenolphthalein  indicator.  A  few  drops  of  methyl 
orange  are  now  added  and  a  measured  excess  of  standard  hydrochloric  acid 
run  in  from  a  burette.  After  heating  to  boiling  the  excess  acid  is  titrated  with 
standard  caustic  solution,  1  cc.  of  which  is  equivalent  to  1  cc.  of  the  hydro- 
chloric acid. 

HC1X0.1646=C. 

1  cc.  N/10  HCloO.0022  gram  C02. 

NOTE.  The  method  is  used  in  the  Omaha  laboratory  of  the  Union  Pacific  Rail- 
road. Dr.  N.  F.  Harriman,  Chief  Chemist,  informed  the  writer  (W.  W.  Scott),  that 
with  care  no  difficulty  is  experienced  with  contamination  of  the  barium  hydroxide 
and  excellent  results  are  obtained.  The  Victor-Meyer  bulb  is  used  for  holding  the 
barium  hydroxide. 


Determination  of  Carbon  by  Measurement  of  the  Volume  of  Carbon  Dioxide  Evolved 
by  Oxidation  of  Carbon,  or  by  the  Decomposition  of  Carbonates  with  Acid. 

Description  of  the  Scheibler  and  Dietrich  Process  and  that  of  Lunge  and  March- 
lewski  are  given  in  Mellor's  work  on  "Inorganic  Analysis,"  pp.  555-559,  1st  Ed. 
A  modification  of  Wiborg's  method  is  described  in  Blair,  "Chemical  Analysis  of  Iron," 
pp.  146-149,  7th  Ed. 

Determination  of  Carbon  Dioxide  in  a  Gas  Mixture. 

See  Gas  Analysis. 


108 


CARBON 


Direct  Colorimetric  Method  for  Determination  of  Combined 

Carbon 

The  procedure  is  of  value  to  the  steel  laboratory  where  a  large  number  of 
daily  determinations  of  combined  carbon  are  required.  By  this  method  over  a 
hundred  determinations  a  day  may  be  made  by  an  experienced  manipulator. 
The  method  depends  upon  the  color  produced  by  combined  carbon  dissolved 
in  nitric  acid,  the  depth  of  color  increasing  with  the  combined  carbon  content 
of  the  material.  Comparison  is  made  with  a  standard  sample  of  iron  or  steel, 
which  is  of  the  same  kind  and  in  the  same  physical  condition  as  the  material 
tested.1  That  is  to  say,  a  Bessemer  steel  should  be  compared  with  a  Bessemer 
standard,  open  hearth  with  open  hearth,  crucible  steel  with  crucible  steel,  the 
standards  containing  approximately  the  same  amounts  of  carbon,  and  as  nearly 
as  possible  the  same  chemical  composition.  The  samples  should  be  taken 
from  the  original  bar  which  has  not  been  reheated,  hammered.,  or  rolled.  Copper, 


FIG.  23. 
Hot  Water  Racks  for  Test  Tubes. 


FIG.  24. 
Color  Carbon  Determination. 


cobalt,  and  chromium  will  interfere  with  the  test;  the  other  elements  have  very 
little  effect. 

Procedure.  One  standard  sample  of  0.2  gram  and  the  same  amount  of 
sample  drillings  are  taken  for  analysis.  The  weighings  are  conveniently  made 
in  brass  or  aluminum  pans,  boat-shaped  to  enable  the  drillings  to  be  dumped 
into  test-tubes.  A  counterpoise,  weighing  the  same  as  the  boat,  is  placed  on 
the  opposite  pan,  together  with  the  0.2  gram  weight.  A  magnetized  knife  will 
assist  in  removing  the  excess  of  material.  The  weighed  sample  is  brushed  into 
a  test-tube  6  ins.  long  (150  mm.)  f  in.  (16  mm.)  in  diameter.  (Each  test-tube 
has  a  label  near  the  open  end  to  distinguish  the  sample.)  A  rack  or  a  600-cc. 
beaker  may  be  employed  for  holding  the  test-tubes  during  the  weighing.  After 
the  batch  is  ready  the  tubes  are  transferred  to  a  perforated  rack  (Figs.  23  or  24) 
and  this  then  stood  in  the  water  bath  filled  with  cold  water. 

The  proper  amount  of  nitric  acid  (sp.gr.  1.2;  e.g.,  1  cone.  HN03  :  1  H20), 
from  a  burette,  is  now  added  to  each  test-tube. 


3  cc.  HN03  for  0.3%  C. 

4  cc.  HN03  for  0.3  to  0.5%. 

5  cc.  HN03  for  0.5  to  0.8%  C. 


6  cc.  HN03  for  0.8  to  1%  C. 

7  cc.  HN03  for  over  1%  C.  steel* 


1  Blair,  "The  Chemical  Analysis  of  Iron." 


CAKBOST 


109 


The  depth  of  color  produced  by  the  acid  will  give  an  idea  of  the  amount 
required.  One  cc.  of  acid  is  added  at  a  time  until  the  depth  of  color  is  correct. 
This  requires  experience  gained  from  observation  of  the  color  produced  by  standard 
samples.  The  acid  is  added  slowly  to  the  coarse  drillings.  Insufficient  acid 
gives  a  darker  tinted  solution  than  it  properly  should  be.  The  nitric  acid  should 
be  free  from  chlorine  and  hydrochloric  acid,  since  these  produce  a  yellow  color. 
(Cl  and  FeCl3  are  yellow.) 

A  glass  bulb  or  a  small  funnel  is  placed  in  each  test-tube  and  the  water  in 
the  bath  then  heated  to  boiling  and  boiled  until  all  the  carbonaceous  matter 
has  dissolved,  the  tubes  being  shaken  from  time  to  time  to  prevent  formation 
of  a  film  of  oxide.  Low-carbon  steels  require  about  twenty  minutes,  whereas 
steels  of  over  1%  carbon  require  about  forty-five  minutes.  (Blair.)  As  soon 
as  the  bubbles  cease  and  the  brownish  flocculent  matter  disappears,  the  rack 
is  removed  from  the  bath  and  placed  in  a  casserole  of  cold  water.  (Prolonged 
heating  and  strong  light  each  causes  fading  of  the  color  due  to  combined  carbon.) 


FIG.  25.— Carbon  Tubes.         FIG.  26. — Color  Comparator  or  Camera. 

Color  Comparison.  This  is  made  in  graduated,  clear,  colorless,  glass  cyl- 
inders called  carbon  tubes.  The  form  shown  in  Fig.  25  was  found  by  the 
writer  l  to  be  the  most  satisfactory  type  for  a  steel-works  laboratory  where  rapidity 
of  manipulation  was  essential.  The  bend  at  the  upper  portion  of  the  tube 
facilitates  mixing  of  the  solution  upon  dilution  with  water,  the  tube  being  tilted 
back  and  forth  until  the  solution  is  homogeneous,  the  bend  preventing  the 
liquid  from  spilling.  The  dilution  should  be  at  least  twice  that  of  the  amount 
of  nitric  acid  used,  as  this  amount  of  water  is  necessary  to  destroy  the  color 
due  to  ferric  nitrate. 

The  standard  is  poured  into  the  carbon  tube  and  the  rinsings  from  the  test 
tube  added.     The  solution  is  diluted  to  a  convenient  multiple  in  cc.  of 
carbon  content.     For  example,  0.45%  carbon  sample  may  be  diluted  to  9  cc., 
then  each  cc.  will  represent  0.05%  carbon.     The  sample  is  placed  in  a  second 
tube  of  exactly  the  same  diameter,  wall  thickness,  and  form.     If  the  solution 
of   the  sample  is   darker  than  the  standard,  water  is   added  little   by  little, 

i  W.  W.  Scott. 


110  CARBON 

followed  by  mixing,  until  the  shade  matches  the  standard.  If  the  standard, 
on  the  other  hand,  is  darker  than  the  sample,  a  greater  dilution  of  the  standard 
is  necessary,  the  cc.  again  representing  a  multiple  of  the  carbon  content.  For 
example  dilution  of  the  .45%  carbon  sample  to  15  cc.  makes  each  cc.  to  repre- 
sent 0.03  carbon.  (It  is  frequently  advisable  to  take  a  standard  of  lower  carbon 
content  in  place  of  greater  dilution  of  the  standard.) 

Example.  Suppose  in  the  first  case  the  dilution  of  the  sample  was  15  cc. 
in  order  to  match  the  standard,  then  15X0.05=0.75%  carbon.  Six  cc.  dilution 
case  2  =6X0.03  =0.18%  carbon. 

The  color  comparison  can  be  best  made  in  a  "  camera, "  a  long  box  with  one 
end  closed  by  a  ground-glass  screen,  Fig.  26.  Parallel  to  the  screen  and  near 
it,  two  holes  through  the  top  of  the  box  admit  the  test-tubes.  The  inner  walls 
of  the  camera  are  blackened  to  prevent  reflection  of  light.  If  a  camera  is  not 
available,  the  tubes  may  be  held  side  by  side  and  compared  against  a  sheet 
of  white  paper  held  as  a  background. 

ANALYSIS  OF  GRAPHITE 
Determination  of  Carbon 

The  procedure  for  determining  carbon  in  graphite  is  the  same  as  that  de- 
scribed for  determination  of  carbon  in  difficultly  combustible  organic  substances. 

The  material  is  broken  down  in  a  steel  mortar  and  powdered  in  an  agate 
mortar.  About  0.2  gram  is  taken  for  the  determination  and  mixed  with  copper 
oxide  to  assist  the  combustion,  then  placed  in  the  boat  and  the  combustion 
of  the  carbon  carried  on  according  to  the  standard  method  in  the  combustion 
tube. 

C02X0.2727=C. 

VOLUMETRIC  DETERMINATION  OF  HYDROCYANIC  ACID1 

The  method  depends  upon  the  decolorization  of  the  blue  ammoniacal  solu- 
tions of  cupric  salts  by  a  soluble  cyanide,  the  reduction  to  cuprous  condition 
being  available  for  an  accurate  quantitative  estimation  of  the  cyanide. 

Standard  Copper  Sulphate.  Twenty-five  grams  of  copper  sulphate, 
CuS04-5H20  are  dissolved  in  a  1000-cc.  flask  with  500  cc.  of  distilled  water  and 
ammonium  hydroxide  added  until  the  precipitate  that  first  forms  dissolves  and 
a  deep  blue  solution  is  obtained.  Water  is  now  added  to  make  the  volume  exactly 
1000  cc.  The  cupric  solution  is  standardized  by  running  a  portion  into  a  solu- 
tion containing  0.5  gram  pure  potassium  cyanide,  KCN,  per  100  cc.  of  water 
and  5  cc.  of  ammonium  hydroxide  until  a  faint  blue  color  is  evident.  Chlorides 
do  not  interfere. 

Procedure.  0.5  gram  of  the  soluble  cyanide  is  dissolved  in  100  cc.  of  water 
and  5  cc.  strong  ammonium  hydroxide  added.  The  standard  cupric  sulphate 
solution  is  now  added  until  the  blue  color  is  obtained.  The  cc.  required  mul- 
tiplied by  the  factor  of  the  copper  salt  in  terms  of  the  salt  sought  gives  the 
weight  of  that  salt  in  the  sample. 

NOTE.  Test  for  Cyanide.  This  depends  upon  the  solvent  action  of  HCN  upon 
freshly  precipitated  HgO  in  presence  of  KOH.  The  filtrate  is  tested  for  mercury 
in  an  acid  solution  by  addition  of  H2S.  (Hood.) 

1 J.  McDowell,  C.  N.,  1904,  p.  221. 


CARBON  in 


Liebig's  Method  for  Determination  of  Hydrocyanic  Acid.    Soluble 

Cyanides l 

Silver  nitrate  reacts  with  an  alkali  cyanide  in  neutral  or  alkaline  solution  as 
follows:  AgN03+2KCN=Ag(CN)2K+KN03.  The  potassium  silver  cyanide  is 
soluble,  hence  the  precipitate  that  first  forms  immediately  dissolves  on  stirring 
as  long  as  the  cyanide  is  present  in  excess  or  in  sufficient  quantity  to  react 
according  to  the  equation.  A  drop  of  the  silver  salt  in  excess  will  produce 
a  permanent  turbidity,  owing  to  the  following  reaction: 

Ag(CN)2K+AgN03=2AgCN+KN03,  the  insoluble  AgCN  being  formed. 

Procedure.  The  alkali  cyanide  contained  in  a  beaker  placed  over  a  sheet 
of  black  glazed  paper,  is  treated  with  4  to  5  cc.  of  10%  KOH  solution  and 
diluted  to  100  cc.  The  liquid  is  now  titrated  with  standard  silver  nitrate,  with 
constant  stirring,  until  a  faint  permanent  turbidity  is  obtained. 

One  cc.  N/10  AgN03  =  0.013022  gram  KCN. 

For  his  review  and  criticism  of  this  chapter  the  author  wishes  to  mention  Mr.  J.  M. 
Cratty,  Chief  Chemist,  U.  S.  Navy  Yards,  Philadelphia,  Pa. 

1  Ann.  d.  Chem.  und  Pharm.,  77,  p.  102. 


CERIUM  AND  THE  OTHER  RARE  EARTHS 

R.  STUART  OWENS  l 


Group  * 

Symbol. 

At.  Wt.f 

Sp.  Gr. 

M.  P. 

Oxides. 

Yttrium  

Yt 

88.7 

3.800 

1250 

Vr,')3 

Erbium 

Er 

167  7 

4  770 

Fr2O,  Er2Pf 

Holmium 

Ho 

163  5 

Thulium 

...     Tm 

168  5 

Tm2O, 

Dysprosium           .  .  . 

Dy 

162  5 

Ytterbium  .          .... 

Yb 

173.5 

1800 

Yb2O3 

(Neo-ytterV  him) 

Lutecium  .               .  . 

Lu 

175  0 

Europium      

Eu 

152  0 

Victorium    

Discovery 

not    confirr. 

ed. 

Group  2: 
Terbium  

Tb 

159.2 

Tb2O3 

Gadolinium  

Gd 

157.3 

1.310 

Gd2O3 

Group  3: 
Cerium 

Ce 

140  25 

6  625 

950 

Ce.,(X  CeoO* 

Lanthanum 

La 

139  0 

6  163 

La->O3 

Neodymium 

Nd 

144  3 

6  544 

840 

Nd2O3 

Praseodymium  
Samarium 

Pr 

.    .     Sa 

140.9 
150  4 

6.544 
7  700 

940 
1350 

Pr203 
Srn20s 

Scandium 

Sc 

44.1 

1300 

Fc2O8 

Decipium  . 

E  iscovery 

not    confirrr 

ed. 

*  According  to  Bohm  (Browning,  "  Introduction  to  the  Rarer  Elements.") 
t  International  atomic  weights,  1916. 

DETECTION 

The  samples  having  been  brought  into  solution  by  one  of  the  methods 
detailed  under  preparation  and  solution  of  the  sample,  the  elements  may  be 
detected  by  one  of  the  following  tests : 

Spectroscopic.  Many  of  the  rare  earth's  elements  have  either  character- 
istic spark  spectrums  or  absorption  spectrums  and  their  presence  may  be  detected 
by  this  means. 

no   absorption  spectrum;   gives  brilliant  spark  spectrum, 
gives 


no 
no 
no 
no 

gives 
no 


no   spark  spectrum. 


Yttrium, 

Erbium, 

Ytterbium. 

Terbium, 

Cerium, 

Lanthanum, 

Samarium, 

Scandium, 

Praseodymium,    no 

Neodymium,        no 

Cerium  shows  lines  of  greatest  intensity  in  the  arc  spectrum  at  4337.9, 
4527.5,  4386.9,  4594.1.  In  the  spark  spectrum  at  4460.3,  4562.5,  4572.4,  4594.1, 
4628.3.  All  of  these  lines  are  in  the  visible  spectrum. 

1  Research  Chemist,  New  York  City. 
112 


CERIUM   AND   THE  OTHER  RARE   EARTHS        113 

In  the  wet  way  cerium  may  be  detected  when  in  the  form  of  cerium  nitrate 
by  boiling  with  lead  peroxide  and  nitric  acid.  A  deep  yellow  color  is  imparted 
to  the  solution,  due  to  the  formation  of  eerie  nitrate. 

Cerium  may  be  detected  by  the  addition  of  sodium  hypochlorite  to  the  solu- 
tion of  a  colorless  cerous  salt.  Red  eerie  hydroxide  is  precipitated.  The  test 
may  be  confirmed  by  the  chlorine  gas  evolved  when  the  precipitate  is  dissolved  in 
hydrochloric  acid. 

Cerous  salts  are  precipitated  by  fixed  alkalies  and  are  insoluble  in  excess. 
Tartaric  acid  hinders  the  precipitation.  Ammonium  sulphide  also  precipitates 
the  hydroxide.  Oxalic  acid  precipitates  cerous  oxalate,  white,  from  moderately 
acid  solutions.  It  is  soluble  in  hot  ammonium  oxalate  but  precipitated  by 
dilution  with  cold  water. 

Lanthanum  may  be  detected  by  adding  iodine  to  the  washed  precipitate, 
formed  by  the  addition  of  ammonium  hydroxide  to  a  solution  of  its  salts.  A 
characteristic  blue  coloration  results. 

Praseodymium,  neodymium,  may  be  detected  by  the  reddish  color  of  their 
solutions  also  by  the  rose  red  or  violet  color  imparted  to  a  bead  of  microcosmic 
salt  when  heated  in  the  flame  of  a  blow  pipe. 

Scandium.  The  hydrochloric  acid  solution  of  a  scandium  salt,  when  boiled 
for  thirty  minutes  with  solid  Na2SiFl6  gives  a  precipitate  which  is  free  from  all 
the  other  rare  earths,  the  scandium  taking  the  place  of  the  sodium  in  the  com- 
pound. 

Ytterbium  may  be  detected  by  adding  to  a  neutral  solution  H2Se03  '4H20. 
A  white  precipitate  of  Yb2(Se03)3,  which  is  insoluble,  results. 

Erbium.     In  the  flame  test  this  earth  gives  an  intense  green  light. 

ESTIMATION 

The  estimation  of  the  rare  earths  is  not  required,  other  than  Cerium,  at 
the  present  time  except  in  a  few  special  instances  as  the  various  elements  have 
found  but  limited  commercial  applications.  They  have  all  been  separated 
from  their  native  combinations,  but  only  a  few  have  been  isolated  and  many  are 
still  believed  to  be  combinations  of  elements. 

Cerium  enters  into  the  manufacture  of  Welsbach  mantles;  iri  the  form  of 
Ce2(S04)3  it  is  used  in  the  manufacture  of  aniline  black;  as  oxalate,  it  is  used  in 
medicine,  and  as  metal  in  alloys. 

Yttrium  is  employed  in  the  fabrication  of  Nernst  lamp  filaments  and  gas 
mantles. 

The  most  important  ores  which  contain  the  rare  earth  elements  are: 

Monazite,  (Ce,  La,  Di,  Th^PCX,  raw  material  for  Ce,  La. 

Gadolinite,  Be2FeY2Si2Oi0,  Yt  earths- 

Xenotime,  YtPO4, 


Euxenite,  R"'(NbO,),  - R2'"(Ti03)3 •  3/2H20, 
Cerite,  (Ca,  Fe)(CeO)(Ce2-30H)(Si03)3, 
Samarskite,  R3"R2'"(Nb,  Ta)602i, 
Yttrotantalite,  R"R2"'(Nb,  Ta)4Oi5-4H20, 
Sipylite,  complex, 
Keilhauite,  complex  silicate, 


Yt 
Ce 
Yt 
Yt 
Yt 
Yt 


In  the  formulas  given  above  R"  stands    for  any  dibasic  radical  or  element 
while  R'"  stands  for  any  tribasic  radical  or  element. 


114        CERIUM  AND  THE  OTHER  RARE  EARTHS 


Preparation  and  Solution  of  the  Sample 

1.  Fusion  Method.    The  finely  pulverized  sample  is  fused  with  sodium 
carbonate  and  the  melt  after  cooling  is  extracted  with  cold  water.    A  sufficient 
quantity  of  hydrochloric  acid  to  impart  an  acid  reaction  is  added.    The  solu- 
tion obtained  is  evaporated  to  dryness  and  baked  to  dehydrate  the  silica,  then 
treated  with  a  little  hydrochloric  acid  and  after  dilution  with  water,  filtered. 
Ammonia  water  is  added  to  the  solution  in  slight  excess  and  the  solution  allowed 
to  stand  until  the  precipitate  has  settled.    It  is  then  filtered  off,  washed  with  cold 
water  and  dissolved  in  hydrochloric  acid.    All  of  the  rare  earths  are  then  present 
in  the  solution  as  chlorides. 

2.  Acid  Extraction.    Decomposition  of  the  finely  pulverized  sample  may 
be  effected  by  mixing  it  with  a  sufficient  quantity  of  sulphuric  acid  to  make  a 
paste  and  then  heating  the  mass,  slowly  at  first  and  then  gradually  increasing 
the  heat  to  dull  redness  when  fumes  of  S03  appear.    After  cooling,  the  mass 
is  extracted  with  cold  water  and  the  metals  of  the  H2S  group  removed  in  the  usual 
way.    The  rare  earths  are  then  present  in  the  solution  as  sulphates  and  may  be 
separated  by  one  of  the  methods  detailed  below. 

3.  Acid  Extraction.    A  strong  mixture  of  nitric  acid  and  hydrochloric  acid 
may  be  used  to  effect  the  decomposition  of  some  of  the  minerals.    The  solution 
after  being  evaporated  to  dryness  and  baked  leaves  a  residue  which  contains 
the  mixed  rare  earths.    The  rare  earths  are  dissolved  in  dilute  hydrochloric  acid. 
Any  silica  present  is  filtered  off  and  the  rare  earths  present  in  the  clear  solution 
may  be  separated  by  one  of  the  methods  detailed  below. 

4.  Decomposition    by     Means    of    Hydrofluoric     Acid.1      Samarskite    and 
euxenite  in  the  finely  powdered  state  are  moistened  with  their  own  weight  of  water 
and  twice  as  much  fuming  hydrofluoric  acid.    The  attack  takes  place  in  a  few 
seconds.    When  the  violent  action  is  over  the  solution  is  evaporated  to  dryness 
on  the  steam  bath,  taken  up  with  water  (30  to  40  cc.  for  a  5-gram  sample)  and 
the  contents  of  the  dish  filtered  and  washed.    The  mineral  is  then  divided  into 
two  portions,  the  filtrate  containing  all  the  metallic  acids,  iron  and  manganese, 
the  insoluble  portion  containing  all  the  rare  earths  and  uranic  acid. 

The  difficulty  of  attack  increases  in  proportion  to  the  amount  of  tantalic 
acid  present  in  the  sample.  The  rare  earths  are  then  extracted  from  the  incoluble 
portion  by  one  of  the  methods  previously  mentioned.  Fusion  with  sodium  car- 
bonate is  preferred. 

SEPARATIONS 

Separation  of  the  rare  earths  from  iron,  aluminum  and  thorium  2  may 
be  effected  by  adding  sodium  fluoride  to  the  hydrochloric  acid  solution  of  the 
Iron  Group  which  has  been  precipitated  as  hydroxide.  The  precipitate,  which 
consists  of  the  double  fluorides  of  the  rare  earths  and  thorium,  is  washed  thoroughly 
and  evaporated  with  sulphuric  acid  on  the  sand  bath  to  decompose  the  fluorides. 
This  process  removes  the  alkaline  earths  as  insoluble  sulphates.  The  excess  acid 
is  removed  by  fuming  and  the  solution  of  the  sulphates  after  diluting  and  warm- 
ing is  treated  with  sodium  thiosulphate  in  solution.  Thorium  thiosulphate  is 
precipitated.  In  solution  are  the  sulphates  of  all  the  rare  earths.  Scandium 

1  Prescott  and  Johnson. 

a  Browning's  "Introduction  to  the  Rarer  Elements." 


CERIUM  AND  THE  OTHER  RARE  EARTHS       115 

is  also  precipitated  as  thiosulphate  if  the  solution  in  sulphuric  is  fumed  too  long 
and  a  neutral  solution  results. 

Calcium  and  manganese,  which  may  also  come  down  with  an  oxalate  pre- 
cipitate of  the  rare  earths,  may  be  separated  from  the  earths  of  the  yttrium  group 
by  precipitation  of  the  solution  with  oxalic  acid,  filtering  off  the  precipitate,  dis- 
solving it  in  nitric  acid  and  evaporating  to  dryness  to  decompose  the  manganese 
salts.  Extracting  with  water  leaves  the  manganese  in  the  residue.  Treat  the 
filtrate  with  ammonia  water.  The  yttrium  group  precipitates  as  hydroxides 
and  may  be  filtered  from  the  calcium,  which  remains  in  solution. 

Cerium,  lanthanum,  praseodymium,  neodymium,  europium  and  gado- 
linium may  be  separated  from  the  other  rare  earths  by  adding  a  saturated  solu- 
tion of  potassium  sulphate  to  the  sulphate  or  chloride  solution  of  all  of  the 
rare  earths.  The  above-mentioned  elements  form  insoluble  double  salts. 

Scandium  may  be  separated  from  yttrium  by  boiling  a  solution  of  the  nitrates. 
A  basic  scandium  nitrate  is  first  precipitated. 

Yttrium  Group.  Barium  carbonate  forms  no  precipitate  in  the  cold,  hence 
the  elements  comprising  same  may  be  separated  from  aluminum,  iron,  chromium, 
thorium,  cerium,  lanthanum,  praseodymium,  and  neodymium  by  this  means. 

Yttrium  Group.  The  precipitation  of  the  group  as  hydroxides  is  not  affected 
by  the  presence  of  tartaric  acid.  Hence  the  members  may  be  thus  separated 
from  aluminum,  glucinum,  thorium,  zirconium,  and  iron. 

Praseodymium,  neodymium,  lanthanum,  and  samarium  may  be  separated 
from  each  other  by  the  fractional  precipitation  of  a  dilute  solution  of  the  nitrates 
with  a  very  dilute  solution  of  ammonia  water  (1  gram  of  NH3  in  500  cc.).  The 
first  precipitates  are  rich  in  samarium;  the  didymiums  come  down  next  and 
the  lanthanum  in  the  last  portions.  By  a  continual  repetition  nearly  pure  salts 
may  be  obtained. 

Besides  the  separations  mentioned  above  the  group  members  may  be  freed 
from  each  other  by  various  other  methods,  as  for  example: 

(1)  Fractional  crystallization  of  the  picrates. 

(2)  Fractional  crystallization  of  the  double  magnesium  nitrates. 

(3)  Fractional  precipitation  of  the  oxalates  in  a  nitric  acid  solution,  etc. 


GRAVIMETRIC  ESTIMATIONS 

Owing  to  the  fact  that  the  quantitative  separation  of  the  rare  earths  is  only 
accomplished  by  the  expenditure  of  a  vast  amount  of  time  and  labor  and  that 
the  various  elements  with  the  exception  of  but  few  have  found  no  commercial 
application,  exact  methods  have  not  been  worked  out  for  the  various  quanti- 
tative assays. 

Cerium,  however,  which  is  the  most  important,  may  be  determined  as 
follows : 

The  element  having  been  brought  into  solution  by  one  of  the  methods  detailed 
above  and  separated  from  the  base  metals,  silica  and  thorium  may  be  isolated 
from  the  other  rare  earths  by  precipitation  in  a  slightly  acid  solution  with  oxalic 
acid.  The  precipitate  is  allowed  to  settle  twenty-four  hours,  filtered,  washed 
with  water  and  ignited.  The  oxides  are  then  dissolved  in  hydrochloric  acid  and 
precipitated  as  hydroxide  by  the  addition  of  an  excess  of  caustic  potash.  The 


116         CERIUM   AND   THE   OTHER  RARE  EARTHS 

precipitate,  suspended  in  solution,  is  subjected  to  the  action  of  chlorine  gas 
which  is  bubbled  through  in  a  steady  stream.  All  of  the  rare  earths  except 
cerium  are  converted  into  the  chlorides,  while  the  latter  remains  as  a  reddish, 
gelatinous  precipitate,  eerie  hydroxide — (Ce(OH)4).  This  may  be  filtered  off, 
washed,  ignited  and  weighed  as  oxide  (Ce02). 

Cerium  may  be  determined  in  its  salts  by  precipitation  with  oxalic  acid, 
allowing  to  settle  out,  filtering,  washing,  and  igniting  to  the  oxide. 

VOLUMETRIC  METHOD  FOR  THE  DETERMINATION 

OF   CERIUM 

Method  of  Franz  Stolba.1  The  cerium  having  been  separated  from  all 
of  the  other  rare  earths  by  some  procedure,  as,  for  example,  that  outlined  above 
under  Gravimetric  Determination,  may  be  precipitated  as  eerie  oxalate.  (Dis- 
solving the  hydroxide  in  hydrochloric  acid  and  then  precipitating  with  oxalic 
acid.)  The  oxalate  precipitate  is  filtered  off,  washed  with  water  until  free  from 
hydrochloric  acid,  and  transferred  to  a  beaker  containing  a  small  quantity  of 
sulphuric  acid  and  a  sufficient  quantity  of  water.  The  mixture  is  warmed  to 
about  70°  C.  and  titrated  with  a  standard  solution  of  KMn04.  During  the 
process  of  titration  the  quantity  of  undissolved  matter  diminishes  and  the 
change  of  color  at  the  end  is  very  distinct.  The  solution  of  KMn04  used  is  pre- 
viously standardized,  using  a  known  amount  of  pure  eerie  sulphate  and  the  same 
quantities  of  water  and  sulphuric  acid. 

Determination  of  Cerium  in  Welsbach  Mantles. 
Colorimetric  Method2 

Burn  off  the  organic  matter  and  heat  with  about  three  times  their  own  weight 
of  H2S04  (cone.)  on  a  sand  bath.  Allow  to  cool  and  pour  into  20  cc.  of  wat3r. 
In  twenty-four  hours  the  sulphates  are  completely  dissolved  and  the  solution 
after  neutralizing  the  excess  of  acid  with  ammonia  water  is  precipitated  with 
oxalic  acid.  The  oxalates  after  settling  out  are  filtered,  washed,  transferred  to 
a  porcelain  casserole  and  digested  with  nitric  acid,  a  little  being  added  at  a  time 
until  complete  decomposition  has  taken  place.  Evaporate  to  dryness  to  remove 
the  excess  acid.  The  nitrates  of  cerium  and  thorium  are  dissolved  in  water 
and  made  to  volume.  Aliquots  are  then  taken  and  diluted  in  comparison  tubes, 
1  cc.  H202  (Merck's  perhydrol)  is  added.  On  adding  ammonia  water  Th(OH) 
is  colored  orange  in  proportion  to  the  amount  of  cerium  present.  In  dilute 
solutions  citric  acid  prevents  the  precipitation  of  the  hydroxides  and  the  color 
can  be  easily  compared  with  standards  containing  known  amounts. 

1  Crooke's  "Select  Methods  of  Analysis." 

8  Method  of  E.  Benz,  Z.  angew  Chem.,  16,  300,  1902. 


CERIUM   AND    THE   OTHER  RARE   EARTHS        117 


RARE  EARTH  OXALATES 

Convert  into   the   sulphates   by   evaporating   with   sulphuric   acid, 
solid  sodium  sulphate  in  excess  to  the  nearly  neutral  solution. 


Dissolve  in    water  and  add 


(1)   PRECIPITATE: 

Th,  Ce,  La,  Pr,  Nd,  Sa,  Eu,  Gd,  etc.,  as  double  sodium  sul- 
phates. 

Boil  with  an  excess  of  sodium  hydroxide,  filter,  wash  with  hot 
water  and  dissolve  in  nitric  acid.  _  Treat  the  nitrates  with 
an  excess  of  zinc  oxide  and  potassium  permanganate. 


(1)  FILTRATE: 

As  double  sodium  sulphates.  Yt,  Tb, 
Dy,  Ho,  Er,  Tm,  Yb,  Sc,  etc. 

Add  oxalic  acid  in  excess  to  precipitate 
the  earths  as  oxalates. 


(2)   PRECIPITATE: 

(2)     FIL- 

(3) PRECIPITATE: 

(3)   FILTRATE: 

As  an  excess  of  sulphuric 

TRATE: 

CeO2  and  ThO2  •  MnO2  is  pres- 
ent is  removed  by  solution  in 

Saturate  the  solution  with 
sodium  sulphate  and  wash 

acid  and  evaporate  to  form 
anhydrous  sulphates  of  Yt, 

Add     to 
filtrate 

hydrochloric    acid    and    then 
precipitation  of  the  Ce  and  Th 
as  double  sulphates  with  so- 

the     precipitate      formed- 
with  a  solution  of  sodium 
sulphate. 

Tb,  drous  sulphates  of  Yt, 
Yb,  Dy,  Ho,  Er.  Tm,  Sc, 
Yb,  etc. 

No.  3. 

dium. 

Dissolve  in  cold  water  and 

Precipitate   is   boiled    with    an 

pour   over    an    excess    of 

excess    of    sodium    hydroxide, 
washed    with   hot   water   and 

PRECIPITATE: 

FIL- 

TRATE  ' 

barium       bromate.       Stir 
well  and  place  on  the  hot 

dissolved  in  nitric  acid.     Add 

Boil  with  excess 

water  bath.     When  double 

ammonia  and  ammonium  ox- 
alate and  ammonium  acetate. 

of  sodium  hy- 
droxide,    filter 

Combine 
with  fil- 

decomposition is  complete 
(when  the  liquid  gives  no 

and  wash  with 

trate 

further     precipitate     with 

hot      water. 

No.  1. 

barium   bromate    solution 

PRECIPITATE: 

FILTRATE: 

Dissolve    in    a 
known  amount 

after  diluting  and  boiling), 
the    mass   is    filtered    and 

Cerium     oxalate. 

Thorium 

of    nitric    acid 

evaporated  to  crystalliza- 

Treat   with    ex- 

oxalate   is 

and     add  an 

tion. 

cess  of  zinc  oxide 

treated 

equivalent 

Terbium    crystallizes    1st, 

and   solution  of 
potassium     per- 

with    am- 
monia    in 

amount      of 
magnesium  ni- 

Dysprosium      crystallizes 
2d,    Holmium  crystallizes 

manganate.  Ce- 

excess, ig- 

trate  in   solu- 

3d,     Yttrium    crystallizes 

rium   oxide  pre- 

nite. 

tion.      Evapo 

4th,   Erbium    crystallizes 

cipitates.       Dis- 

ThO2. 

rate    the    solu- 

Thulium 5th,    crystallizes 

solve   in  hydro- 

tion until  upon 

6th 

chloric  acid  ard 

blowing          on 

The  mother  liquor  is  made 

precipitate       ce- 

surface    small 

neutral  with  ammonia  and 

rium   as  oxalate 

crystals    form. 

saturated  with  potassium 

with  oxalic  acid. 

Spray  water  on 

sulphate. 

surface  and  al- 

low to  crystal- 

lize. 

PRECIPI- 

FILTRATE: 

Lanthanum 

crystallizes  1st, 

TATE 

Add      oxalic 

Praseodymium 

Scandium. 

acid. 

crystallizes  2d, 

Potassium 

Ytterbium   is 

Neodymium 

Sulphate. 

precipitat- 

crystallizes 3d 

ed  as  oxal- 

Samarium 

ate. 

crystallizes  4th 

Europium 

crystallizes  5th 

Gadolinium 

crystallizes  6th 

The  crystalliza- 

tion     is      con- 

trolled  by   the 

spectroscope. 

The        greater 

number      of 

times       the 

earths  arefrac- 

tionated      the 

purer  the  prod- 

uct will  be. 

CHLORINE 

WILFRED  W.  SCOTT  and  WM.  F.  DOERFLINGER 

C12,  at.wt.  35.46;  D.  (air),  3.491;  m.p.  -1O1.50;1   b.p.   —  33.6°  C.;  oxides, 

C120,  C102,  C1207. 

DETECTION 

Free  Chlorine.  The  yellow  gas  is  recognized  by  its  characteristic  odor. 
It  liberates  iodine  from  iodides;  it  bleaches  litmus,  indigo,  and  many  organic 
coloring  substances. 

Chlorides.  Silver  Nitrate  Test.  In  absence  of  bromides  and  iodides, 
which  also  form  insoluble  silver  salts,  silver  nitrate  precipitates  from  solutions 
containing  chlorides  white,  curdy,  silver  chloride,  AgCl  (opalescent  with  traces), 
soluble  in  NH4OH  (AgBr  slowly  soluble,  Agl  difficultly  soluble),  also  soluble 
in  concentrated  ammonium  carbonate  (AgBr  is  very  slightly  soluble;  Agl  is  insol- 
uble). Silver  chloride  turns  dark  upon  exposure  to  light. 

Free  Hydrochloric  Acid.  Manganese  Dioxide,  Potassium  Permanganate, 
and  certain  oxidizing  agents  liberate  free  chlorine  gas  when  added  to  solutions 
containing  free  hydrochloric  acid.  The  gas  passed  into  potassium  iodide  lib- 
erates free  iodine,  which  produces  a  blue  solution  with  starch. 

Concentrated  Sulphuric  Acid  added  to  chlorides  and  heated  liberates  HC1 
gas,  which  produces  a  white  fume  in  presence  of  ammonium  hydroxide. 

Detection  in  Presence  of  Cyanate,  Cyanide,  Thiocyanate.  An  excess 
of  silver  nitrate  is  added  to  the  solution,  the  precipitate  filtered  off  and  boiled 
with  concentrated  nitric  acid  to  oxidize  the  cyanogen  compounds  and  the  white 
precipitate,  silver  chloride,  subjected  to  the  tests  under  chlorides  to  confirm 
the  compound. 

Detection  in  Presence  of  Bromide  and  Iodide.  About  10  cc.  of  the 
solution  is  neutralized  in  a  casserole  with  acetic  acid,  adding  about  1  to  2  cc. 
in  excess,  and  then  diluting  to  about  6  volumes  with  water.  About  half  a 
gram  of  potassium  persulphate,  K2S208,  is  added  and  the  solution  heated. 
Iodine  is  liberated  and  may  be  detected  by  shaking  the  solution  with  carbon 
disulphide,  which  is  colored  blue  by  this  element.  Iodine  is  expelled  by  boiling, 
the  potassium  persulphate  being  repeatedly  added  until  the  solution  is  colorless. 
Bromine  is  liberated  by  adding  2  or  3  cc.  of  dilute  sulphuric  acid  and  additional 
persulphate.  A  yellowish-red  color  is  produced  by  this  element.  Carbon 
disulphide  absorbs  bromine,  becoming  colored  yellowish  red.  Bromine  is  expelled 
with  additional  persulphate  and  by  boiling.  The  volume  of  the  solution  should 
be  kept  to  about  60  cc.,  distilled  water  being  added  to  replace  that  which  is 
expelled  by  boiling.  When  bromine  is  driven  out  of  the  solution,  the  silver 
nitrate  test  for  chlorides  is  made.  A  white,  curdy  precipitate,  soluble  in 
ammonium  hydroxide  and  reprecipitated  upon  acidifying  with  nitric  acid,  is 
produced,  if  chlorides  are  present. 

1  Ref.  Cis.  35  (2d  Ed.),  U.  S.  Bureau  of  Standards. 
118 


CHLORINE  119 

If  Chlorates  are  Present.  The  halogens  are  precipitated  with  silver  nitrate, 
the  precipitate  dissolved  with  zinc  and  sulphuric  acid  and  the  solution  treated 
as  directed  in  the  preceding  paragraph. 

Test  for  Hypochlorite.  Potassium  hypochlorite,  KC10,  shaken  with  mer- 
cury forms  the  yellowish-red  compound  Hg.OCk,1  which  does  not  form  with  the 
other  potassium  salts  of  chlorine,  i.e.,  KC1,  KC102,  KC103,  KC104. 

Hypochlorites  decolorize  indigo,  but  do  not  decolorize  potassium  perman- 
ganate solutions.  If  arsenious  acid  is  present,  indigo  is  not  decolorized  until 
all  of  the  arsenious  acid  has  been  oxidized  to  the  arsenic  form. 

Tests  for  Chlorite.  Potassium  permanganate  solution  is  decolorized  by 
chlorites.  (The  solution  should  be  dilute.) 

A  solution  of  indigo  is  decolorized,  even  in  presence  of  arsenious  acid  (dis- 
tinction from  hypochlorites) . 

Detection  of  Chlorate.  The  dry  salt  heated  with  concentrated  sulphuric 
acid  detonates  and  evolves  yellow  fumes. 

Chlorates  liberate  chlorine  from  hydrochloric  acid. 

Perchlorate.  The  solution  is  boiled  with  hydrochloric  acid  to  decompose 
hypochlorites,  chlorites  and  chlorates.  Chlorides  are  removed  by  precipitation 
with  silver  nitrate,  the  filtrate  evaporated  to  dryness,  the  residue  fused  with 
sodium  carbonate  to  decompose  the  perchlorate  to  form  the  chloride,  which  may 
now  be  tested  as  usual. 

ESTIMATION 

The  determination  of  chlorine  is  required  in  a  large  number  of  substances. 
It  occurs  combined  as  a  chloride  mainly  with  sodium,  potassium  and  mag- 
nesium. Rock  salt,  NaCl,  sylvine,  KC1,  carnallite,  KC1  •  MgCl2  •  6H20,  matlockite, 
PbCl2-PbO;  horn  silver,  AgCl,  atacamite,  CuCl2-3Cu(OH)2,  are  forms  in  which  it 
is  found  in  nature.  Chlorine  is  determined  in  the  evaluation  of  bleaching  powder. 
It  is  estimated  in  the  analysis  of  water. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  the  sample  the  following  facts  should  be  borne  in  mind: 
Although  chlorides  are  nearly  all  soluble  in  water,  silver  chloride  is  practically 
insoluble  (100  cc.  dissolves  0.000152  gram  at  20°  C.);  mercurous  chloride  is 
nearly  as  insoluble  as  silver  chloride  (0.00031  gram);  lead  chloride  requires  heat 
to  bring  it  into  solution  (in  cold  water  only  0.673  gram  soluble  per  100  cc.  of 
water).  Chlorides  of  antimony,  tin,  and  bismuth  require  free  acid  to  keep 
them  in  solution.  Hydrochloric  acid  increases  the  solubility  of  silver,  mercury, 
lead,  antimony,  bismuth,  copper  (Cu')>  gold  and  platinum,  but  decreases  the 
solubility  of  cadmium,  copper  (Cu"),  nickel,  cobalt,  manganese,  barium,  cal- 
cium, strontium,  magnesium,  thorium,  sodium,  potassium  and  ammonium  chlorides. 

Chlorine  gas  is  most  readily  dissolved  in  water  at  10°  C.  (1  vol.  H20  dissolves 
3.095  vols.  Cl).  Boiling  completely  removes  chlorine  from  water. 

Hypochlorites,  chlorites,  chlorates,  and  perchlorates  are  soluble  in  water. 

The  chlorine  may  be  present  either  combined  or  free.  In  the  combined 
state  it  may  be  present  as  free  hydrochloric  acid  or  as  a  water-soluble  or  insol- 
uble salt. 

1  Prescott  and  Johnson,  Qual.  Chem.  Anal.    D.  Van  Nostrand  Co. 


120  CHLORINE 

Water-soluble  Chlorides.  Chlorides  of  the  alkali  or  alkaline  earth  groups 
may  be  treated  directly  with  silver  nitrate  upon  making  slightly  acid  with 
nitric  acid,  the  chlorine  being  determined  either  gravimetrically  or  volumetrically 
according  to  one  of  the  procedures  given  later.  It  is  convenient  to  work  with 
samples  containing  0.01  gram  to  1  gram  of  Cl.  The  sample  is  dissolved  in  about 
150  cc.  of  water,  made  acid  with  nitric  acid  with  about  5  to  10  cc.  in  excess  of 
the  point  of  neutralization,  should  the  sample  be  alkaline.  Then  the  chlorine 
combined  as  chloride  is  determined  as  directed  later. 

If  the  water  solution  contains  a  chloride  of  a  heavy  metal  which  forms 
basic  salts  (e.g.,  stannic,  ferric,  etc.,  solutions),  or  which  may  tend  to  reduce 
the  silver  solution,  it  is  necessary  to  remove  these  by  precipitation  with  ammo- 
nium hydroxide,  or  by  sodium  hydroxide,  or  potassium  carbonate  solution. 
The  salt  is  dissolved  in  water  and  acidified  with  HN03,  adding  about  10  cc.  in 
excess,  for  about  150  cc.  of  solution.  (This  excess  HN03  should  be  sufficient 
to  oxidize  substances  which  would  tend  to  reduce  the  silver  reagent;  e.g.,  FeS04, 
etc.)  Ammonia  solution  (free  from  chloride)  is  added  in  sufficient  quantity 
to  precipitate  the  heavy  metals  iron,  manganese,  aluminum,  etc.  The  mixture  is 
filtered  and  the  residue  washed  several  times  with  distilled  water.  Chlorine 
is  determined  in  the  filtrate  by  acidifying  with  HN03  as  directed  above. 

Water-insoluble  Chlorides.  The  chloride  may  frequently  be  decomposed 
by  boiling  with  sodium  carbonate  solution.  Many  of  the  minerals,  however, 
require  fusion  with  sodium  carbonate  to  prepare  them  for  solution;  e.g.,  apatite, 
sodalite,  etc.  Silver  chloride  may  also  be  decomposed  by  fusion. 

Silver  Chloride.  The  sample  is  mixed  with  about  three  times  its  weight  of 
Na2C03  and  fused  in  a  porcelain  crucible  until  the  mass  has  sintered  together. 
The  soluble  chloride,  NaCl,  is  leached  out  with  water,  leaving  the  water-in- 
soluble carbonate  of  silver,  which  may  be  filtered  off.  The  filtrate  is  acidified 
with  HNO3  and  chlorine  determined  as  usual. 

Chlorine  in  Rocks.  The  finely  ground  material  is  fused  with  about  five  times 
its  weight  of  potassium  carbonate.  The  melt  is  extracted  with  hot  water,  cooled 
and  the  solution  acidified  with  nitric  acid  (methyl  orange  indicator),  and  the 
solution  allowed  to  stand  several  hours  (preferably  over  night).  If  silicic  acid 
precipitates,  the  solution  is  treated  with  ammonia  and  boiled,  filtered  and  the 
filter  washed  with  hot  water.  The  cooled  filtrate  is  acidified  with  nitric  acid  and 
chlorine  determined  as  usual.  If  silicic  acid  does  not  separate,  the  addition  of 
ammonia  may  be  omitted  and  chlorine  determined  in  the  solution. 

Free  Chlorine.  Free  chlorine  may  be  determined  volumetrically  according 
to  the  procedure  given  under  this  section.  If  it  is  desired  to  determine  this 
gravimetrically,  a  definite  amount  of  the  chlorine  water  is  transferred  by  means 
of  a  pipette  to  a  flask  containing  ammonia  solution  and  the  mixture  heated 
to  boiling.  The  cooled  solution  is  acidified  with  nitric  acid  and  the  chloride 
precipitated  with  silver  nitrate  according  to  the  standard  procedure  given 
on  page  127. 

NOTE.  Free  chlorine  cannot  be  precipitated  directly,  as  the  following  reaction 
takes  place:  6Cl+6AgNO3+3H2O=5AgCl+AgClO3+6HNO3. 

Reaction  of  chlorine  with  ammonia:  2C1+2NH4OH  =  NH4C1+NH4OC1+H2O. 
When  the  solution  is  boiled,  NH4OC1  breaks  down,  e.g,  3NH4OC1+2NH3  =  3NH4C1 
+N2+3H20. 

Chlorine  in  Ores  and  Cinders.  One  hundred  grams  of  the  finely  ground 
ore  or  cinder  are  placed  in  a  500-cc.  flask,  containing  300  cc.  of  strong  sulphuric 


CHLORINE  121 

acid  (Cl-free).  The  flask  is  shaken  to  mix  the  sample  with  the  acid  and  then 
connected  with  an  absorption  apparatus,  containing  distilled  water  or  dilute 
caustic  solution.  The  sample  is  gradually  heated,  the  distillation  flask  resting 
upon  a  sand  bath.  After  two  hours,  which  is  sufficient  to  expel  all  the  chlorine 
as  hydrochloric  acid,  the  contents  of  the  absorption  tubes  are  filtered,  if  free 
sulphur  is  present  (sulphide  ores),  nitric  acid  added  and  the  filtrate  brought 
to  boiling  to  oxidize  any  S02  that  may  be  present.  Chlorine  is  precipitated 
according  to  the  standard  procedure  on  page  124. 

During  the  run  the  distilling  flask  should  be  shaken  occasionally  to  prevent 
caking.  Suction  applied  at  the  absorption  end  of  the  apparatus  and  a  current 
of  air  swept  through  the  system  aids  in  carrying  over  the  HC1  into  the  water 
or  NaOH. 

Determination  of  Halogens  in  Organic  Compounds.    Method  of 

Carius x 

Organic  compounds  may  be  decomposed  by  heating  with  strong  nitric  acid 
at  high  temperatures  under  pressure.  If  this  heating  is  conducted  in  the  presence 
of  silver  nitrate,  the  halogen  hydride,  formed  by  the  action  of  nitric  acid  on  the 
organic  compound,  is  converted  to  the  silver  halide.  This  is  weighed,  or  the 
excess  AgN03  titrated  (p.  125).  Arsenic,  phosphorus,  and  sulphur  are  oxidized 
to  arsenic,  phosphoric,  and  sulphuric  acids,  the  metals  present  being  converted 
to  nitrates. 

Procedure.  About  0.5  to  1  gram  of  powdered  silver  nitrate  is  introduced, 
by  means  of  a  glazed  paper  funnel,  into  a  heavy-walled,  bomb-glass  tube,  which 
is  sealed  at  one  end  and  is  50  cm.  long,  2  cm.  in  diameter  and  about  2  mm.  thick- 
ness of  wall.  About  30  cc.  of  strong  nitric  acid  (96%),  free  from  chlorine,  are 
introduced  by  means  of  a  long-stemmed  funnel,  to  avoid  wetting  the  upper  portion 
of  the  tubing.  About  0.1  gram  of  the  organic  substance,  contained  in  a  small  bore, 
thin  wall,  glass  tube  closed  at  one  end  (4-5  cm.  long),  is  introduced  into  the  bomb 
tube,  inclined  to  one  side.  The  small  tube  should  float  in  the  nitric  acid,  as  it  is 
important  that  the  material  should  not  come  in  contact  with  nitric  acid  until  the 
bomb  has  been  sealed,  as  loss  of  halogen  is  apt  to  occur  with  open  tubes.  The 
upper  end  of  the  bomb  is  softened  in  the  blast-lamp  flame,  drawn  out  to  a  thick- 
walled  capillary  tube  and  fused. 

When  cold,  the  bomb  is  wrapped  in  asbestos  paper,  shoved  into  an  iron  tube 
of  a  bomb  furnace  and  the  heat  turned  on.  The  heating  is  so  regulated  that  the 
temperature  is  raised  to  200  °  C.  in  three  hours.  If  a  higher  temperature  is  neces- 
sary, the  heating  should  be  such  as  to  cause  a  rise  of  50°  C.  in  three  hours.  Sub- 
stances of  the  aromatic  series  require  eight  to  ten  hours  heating  at  250  to  300°  C., 
while  aliphatic  substances  may  be  decomposed  at  200°  C.  in  about  four  hours.2 
Occasionally  it  is  necessary  to  relieve  the  pressure  in  a  tube  after  heating  to  200°  C., 
before  taking  to  a  higher  temperature,  by  softening  the  tip  of  the  cooled  bomb  in 
a  flame,  allowing  the  accumulated  gas  to  blow  out,  resealing  and  again  heating 
to  the  desired  temperature.  Evidence  of  crystals  or  drops  of  oil  in  the  glass  tube 
indicate  incomplete  decomposition.  When  the  bomb  is  cooled,  it  is  removed  by 

1  Ann.  d.  Chem.  u.  Pharm.  (1865),  136,  p.  129. 

2  Treadwell  and  Hall,  Anal,  Chem.,  J.  Wiley  &  Son.    P.  C.  R.  Kingscott  and  R.  S.  G. 
Knight,  Methods  of  Quant.  Org.  Anal.      Longmans,  Green  &  Co.  (1914),  Clowes  and 
Coleman,  Quant.  Chem.   Anal.,  P.  Blakiston's  Son  &  Co.,  1900. 


122  CHLORINE 

taking  out  the  iron  sheath  from  the  furnace  and  inclining  it  so  that  the  glass  capil- 
lary tip  slides  partly  out  of  the  tube.  (The  eyes  should  be  protected  by  goggles.) 
The  point  of  the  capillary  is  held  in  the  flame  until  the  tip  softens  and  the  gas 
pressure  is  released  by  blowing  through  a  passage  in  the  softened  glass.  When  the 
gas  has  escaped,  a  scratch  with  a  file  is  made  below  the  capillary  and  the  tip 
broken  off  by  touching  the  scratch  with  a  hot  glass  rod.  The  contents  of  the  bomb 
are  poured  out  into  a  beaker,  the  tube  washed  out  with  water  and  the  combined 
solution  made  to  about  300  cc.  This  is  heated  to  boiling  and  then  allowed  to  cool. 
The  halide  precipitate  is  filtered  through  a  Gooch  crucible,  then  dried  and  weighed, 
or  by  titrating  the  excess  AgN03  by  Volhard's  method,  the  halide  may  be  esti- 
mated. 

If  pieces  of  glass  should  be  present,  the  precipitates,  AgCl  or  AgBr,  are 
dissolved,  in  ammonium  hydroxide,  filtered  and  reprecipitated  by  acidifying 
with  nitric  acid.  Agl  may  be  dissolved  by  means  of  dilute  sulphuric  acid  and 
zinc.  The  excess  zinc  is  removed,  the  glass  washed  free  of  iodine,  dried  and 
weighed  and  its  weight  subtracted  from  the  original  impure  Agl,  giving  the  weight 
of  the  pure  silver  iodide. 

Lime  Method  for  Determination  of  Halogens  in  Organic  Matter 

A  layer  of  lime  (free  from  chloride),  about  6  cm.  long,  is  introduced  into 
a  difficultly  fusible  glass  tube,  closed  at  one  end  (35  cm.  long  and  with  1  cm. 
bore),  followed  by  0.5  gram  of  the  substance,  and  6  cm.  more  of  the  lime.  The  sub- 
stance is  thoroughly  mixed  by  means  of  a  copper  wire  with  a  spiral  end.  The 
tube  is  nearly  filled  with  lime,  and  in  a  horizontal  position,  gently  tapped  to  cause 
the  lime  to  settle  and  form  a  channel  above  the  layer.  The  tube  is  placed  in  a 
small  carbon  combustion  furnace.  The  heat  is  turned  on,  so  that  the  front  end 
of  the  tube  is  heated  to  dull  redness  and  then  the  end  containing  the  substance. 
When  the  organic  matter  has  been  decomposed,  the  tube  is  cooled  and  the  contents 
transferred  to  a  beaker  and  the  lime  dissolved  in  dilute  nitric  acid  (Cl-free).  The 
carbon  is  filtered  off  and  the  halogen  determined  as  usual  in  the  filtrate. 

Should  a  sulphate  be  present  in  the  mixture,  organic  matter  will  reduce  it  to  a 
sulphide,  so  that  AgS  will  be  precipitated  along  with  the  halides.  To  prevent 
this,  hydrogen  peroxide  is  added  to  the  solution  which  should  be  slightly  alkaline. 
The  mixture  is  boiled  to  remove  the  excess  of  H202  and  is  then  acidified  with 
nitric  acid,  the  solution  filtered  and  the  halide  determined  in  the  filtrate. 

With  substances  rich  in  nitrogen,  some  soluble  cyanide  is  apt  to  form.  The 
silver  precipitate  containing  the  halides  and  the  cyanide  is  heated  to  fusion.  The 
residue  is  now  treated  with  zinc  and  sulphuric  acid,  the  metallic  silver  and  the 
paracyanogen  filtered  off  and  the  halides  determined  in  the  filtrate, 

Sodium  Peroxide  Method 

Organic  compounds  may  be  decomposed  by  sodium  peroxide  in  an  open 
crucible  without  recourse  to  a  sealed  tube,  as  is  required  by  the  Carius  method. 
The  following  is  the  procedure  outlined  by  Pringsheim.1 

About  0.2  gram  of  substance  in  a  small  steel  crucible  is  treated  with  a  cal- 

*  C.  N.,  1905,  91,  2372,  215. 


CHLORINE  123 

ciliated  quantity  of  sodium  peroxide.1  The  crucible  should  be  only  two-thirds 
of  its  height  full;  this  is  put  in  a  large  porcelain  crucible,  in  which  a  little  cold 
water  is  carefully  placed,  so  that  the  steel  crucible  stands  out  1  to  2  cm.  This 
latter  crucible  is  covered  with  its  own  cover,  in  which  is  a  hole  through  which 
an  iron  "wire  heated  to  redness  can  be  introduced  with  the  object  of  starting 
the  combustion.  As  soon  as  the  combustion  is  completed  the  whole  is  plunged 
into  the  water  in  the  larger  crucible.  The  porcelain  crucible  is  covered  with  a 
watch-glass  and  heated  gently  until  the  whole  mass  is  dissolved.  This  point  is 
recognized  when  n'p  more  bubbles  are  given  off  and  when  there  are  no  more 
particles  of  carbon  which  have  escaped  combustion.  The  steel  crucible  is  then 
removed  and  washed  carefully;  the  solution  is  filtered  and  treated  with  an 
excess  of  sulphurous  acid  (to  neutralize  the  alkaline  liquid,  and  to  reduce  the 
oxidized  products:  bromic,  iodic  acids,  etc.).  The  solution  is  acidulated  with 
nitric  acid,  then  made  to  a  volume  of  about  500  cc.,  and  the  halogens  precip- 
itated with  silver  nitrate  and  the  precipitate  washed,  dried  and  weighed  as 
usual. 

SEPARATIONS  2 

Separation  of  Chlorine  and  the  Halides  from  the  Heavy  Metals.  Halides 
of  the  heavy  metals  are  transposed  by  boiling  their  solutions  with  sodium  car- 
bonate, the  heavy  metals  being  precipitated  as  carbonates  and  the  halides  going 
into  solution  as  sodium  salts. 

Separation  of  Halides  from  Silver  and  from  Silver  Cyanide.  The  silver 
salt  is  treated  with  an  excess  of  zinc  and  sulphuric  acid,  the  metallic  silver 
and  the  paracyanogen  filtered  off,  and  the  halides  determined  in  the  filtrate. 

Separation  of  the  Halides  from  One  Another.  Separation  of  Chlorine 
from  Iodine.  The  method  depends  upon  the  fact  that  nitrous  acid  sets  iodine 
free  from  dilute  solutions  containing  a  mixture  of  halogen  salts,  bromides  and 
chlorides  being  unaffected. 

The  solution  of  the  chloride  and  the  iodide  in  an  Erlenmeyer  flask  is  diluted 
to  400  cc.  and  10  cc.  of  dilute  sulphuric  acid,  1  :  1,  are  added.  The  gas  from  2 
grams  of  sodium  nitrite  is  passed  into  the  solution  at  the  rate  of  about  five  bub- 
bles per  second.3  (Pure  sodium  or  potassium  nitrite  may  be  added  directly  to  the 
solution  in  the  flask.)  The  liberated  iodine  is  now  completely  expelled  by  boiling 
until  the  evolving  steam  no  longer  reacts  upon  litmus  paper.  Should  a  deter- 
mination of  iodine  be  desired  the  evolved  gas  is  absorbed  in  a  hydrogen  peroxide 
sodium  hydroxide  solution  according  to  the  procedure  described  under  iodine. 

1  Charge  of  sodium  peroxide  is  judged  as  follows: 


Per  cent  C  and  O  in  material. 

Amount  of  sugar  to  add. 

Amount  of  Na2<32  required. 

Over  75 
30  to  75 
25  to  50 
Below  25 

0 
0 
|  the  wt.  of  sub. 
An  equal  weight 

18  times  wt.  of  sub. 
16  times  wt.  of  sub. 
16  times  wt.  of  sub. 
16  times  wt.  of  sub. 

2  Attention  is  called  to  "  Methods  in  Chemical  Analysis,"  by  F.  A.  Gooch  for  useful 
information  on  the  separation  of  the  halogens.  . 

3  Nitrous  acid  is  generated  by  addition  of  dilute  H2SO4  to  NaNOg,  the  acid  being 
added  drop  by  drop  through  a  thistle  tube  with  glass  stop-cock. 


124  CHLORINE 

The  contents  of  the  flask  are  treated  with  silver  nitrate  and  the  precipitated 
silver  chloride  determined  as  usual. 

Separation  of  Chlorine  and  Bromine  from  Iodine.  The  procedure  is 
similar  to  the  separation  of  chlorine  from  iodine  with  the  exception  that  a  more 
dilute  solution  is  necessary  to  prevent  the  volatilization  of  bromine  with  the 
iodine. 

The  neutral  solution  containing  the  halogens  is  diluted  to  about  700  cc.  and 
about  2  to  3  cc.  of  dilute  sulphuric  acid,  1:1,  are  added  and  a  sufficient  amount 
of  pure  sodium  nitrite  introduced  or  nitrous  acid  gas  passed  into  the  solution 
as  directed  above.  The  solution  is  boiled  until  colorless  and  until  the  evolved 
steam  no  longer  acts  upon  litmus  paper.  About  twenty  minutes'  boiling  after 
the  color  of  iodine  has  disappeared  from  the  flask  will  completely  eliminate 
iodine;  in  this  case,  however,  water  should  be  added  to  the  flask  to  replace  that 
evaporated  before  the  solution  has  been  reduced  to  a  volume  of  less  than  600  cc. 

For  determination  of  bromine  in  the  residue  remaining  in  the  flask,  see  the 
chapter  on  this  subject,  page  79. 


GRAVIMETRIC   METHOD 

Determination  of  Chlorine  Combined  as  Chloride  by  Precipitation 

as  Silver  Chloride 

The  procedure  is  the  reciprocal  to  the  one  for  determination  of  silver;  in  this 
case  the  soluble  silver  salt  is  added  to  the  sodium  chloride  solution,  in  which 
chlorine  is  to  be  determined. 

Procedure.  To  the  nitric  acid  solution  of  the  chloride,  prepared  according  to 
directions  given  under  "  Preparation  and  Solution  of  the  Sample,"  is  added  silver 
nitrate  solution  in  slight  excess,  stirring  during  the  addition  of  the  reagent.  (Stir- 
ring aids  the  coagulation  of  the  AgCl  and  hastens  settling.  It  is  advisable  to  allow 
the  precipitate  to  settle  sufficiently  to  clear  the  upper  portion  of  the  solution 
in  order  to  detect  whether  further  precipitation  takes  place  upon  addition  of 
more  of  the  reagent.)  The  mixture  is  now  heated  until  it  is  hot  to  the  touch 
and  then  allowed  to  settle  for  half  an  hour  or  more,  preferably  in  the  dark.  It 
is  filtered  through  a  weighed  Gooch  crucible,  washing  the  precipitate  by  decan- 
tation  several  times  with  cold  water,  slightly  acid  with  nitric  acid,  and  then 
the  precipitate  transferred  to  the  Gooch  is  washed  free  of  silver  nitrate  (HC1 
test)  with  cold  distilled  water.  The  Gooch  is  dried  for  fifteen  to  twenty  minutes 
at  100°  C.  and  then  at  about  130°  C.  to  constant  weight.  The  sample  is  now 
weighed  as  AgCl.1 

AgClX  0.2474  =C1. 

NOTES.  Free  chlorine  is  converted  to  chloride  according  to  the  procedure  given 
for  preparing  the  sample,  and  then  determined  according  to  the  procedure  given 
above.  If  chlorine  and  chlorides  are  both  present  in  the  solution  and  each  is  desired, 
the  free  chlorine  is  determined  according  to  the  volumetric  procedure  given  later, 
and  the  total  chloride  determined  gravimetrically,  then  free  chlorine  subtracted 
from  total  chlorine  and  the  result  taken  as  combined  chlorine  of  the  solution. 

1  The  silver  chloride  should  be  completely  soluble  in  ammonia.  If  it  is  not,  the 
product  is  impure.  To  separate  it  from  SiO?,  A12O3,  and  other  impurities,  the  pre- 
cipitate is  dissolved  in  ammonia,  the  solution  filtered  free  from  the  impurities, 
and  the  AgCl  reprecipitated  by  acidifying  with  nitric  acid  and  adding  a  few  drops 
of  silver  nitrate. 


CHLORINE  125 

If  a  paper  filter  is  used  in  place  of  the  Gooch  crucible,  the  greater  part  of  the 
precipitate  is  removed,  the  paper  ignited  separately,  the  reduced  silver  oxidized  with 
HNO3,  a  drop  or  so  HC1  added,  then  evaporated  off,  and  the  residue  combined  with 
major  portion  of  AgCl  and  ignited  gently  until  the  salt  begins  to  melt. 

VOLUMETRIC   METHODS 

Determination  of   Chlorine  in  Acid   Solution,  Silver  Thiocyanate 

Ferric  Alum  Method 

The  method,  devised  by  Volhard,1  is  applicable  to  titration  of  chlorine  in 
acid  solutions,  a  condition  frequently  occurring  in  analysis,  where  the  Silver- 
Chromate  Method  of  Mohr  cannot  be  used.  The  method  is  based  on  the  fact 
that  when  solutions  of  silver  and  an  alkali  thiocyanate  are  mixed  in  presence 
of  a  ferric  salt,  the  thiocyanate  has  a  selective  action  towards  silver,  combining 
with  this  to  form  thiocyanate  of  silver,  any  excess  of  that  required  by  the  silver 
reacting  with  the  ferric  salt  to  form  the  reddish-brown  ferric  thiocyanate,  which 
color  serves  as  an  indication  of  the  completion  of  the  reaction.  An  excess  of 
silver  nitrate  is  added  to  the  nitric  acid  solution  containing  the  chloride,  AgCl 
filtered  off,  and  the  excess  of  silver  titrated  with  the  thiocyanate  in  presence  of 
the  ferric  salt. 

Copper  (up  to  70%),  arsenic,  antimony,  cadmium,  bismuth,  lead,  iron,  zinc, 
manganese,  cobalt,  and  nickel,  do  not  interfere,  unless  the  proportion  of  the  latter 
metals  is  such  as  to  interfere  by  intensity  of  the  color  of  their  ions. 

Preparation  of  Special  Reagents.  N/10  Ammoniutn  or  Potassium  Thio- 
cyanate Solution.  About  8  grams  of  ammonium  or  10  grams  of  potassium  salt 
are  dissolved  in  water  and  diluted  to  one  liter.  The  solution  is  adjusted  by 
titration  against  the  N/10  silver  nitrate  solution.  It  is  advisable  to  have  1  cc. 
of  the  thiocyanate  equivalent  to  1  cc.  of  the  silver  nitrate  solution.  Owing  to 
the  deliquescence  of  the  thiocyanates  the  exact  amount  for  an  N/10  solution 
cannot  be  weighed. 

N/10  Silver  Nitrate.  This  solution  contains  10.788  grams  Ag  or  16.989  grams 
AgN03  per  liter.  The  silver  nitrate  salt,  dried  at  120°  C.,  or  pure  metallic  silver 
may  be  taken,  the  required  weight  of  the  latter  being  dissolved  in  nitric  acid 
and  made  to  volume,  or  17.1  grams  of  the  salt  dissolved  in  distilled  water  and 
made  to  1000  cc.  The  solution  is  adjusted  to  exact  decinormal  strength  by 
standardizing  against  an  N/10  sodium  chloride  solution,  containing  5.846  grams 
of  pure  NaCl  per  liter. 

Ferric  Indicator.  Saturated  solution  of  ferric  ammonium  alum.  Should 
this  not  be  available,  FeS04  may  be  oxidized  with  nitric  acid,  and  the  solution 
evaporated  with  an  excess  of  H2S04  to  expel  the  nitrous  fumes.  A  10%  solution 
is  desired.  Five  cc.  of  either  of  these  reagents  are  taken  for  each  titration. 

Pure  Nitric  Acid.  This  should  be  free  from  the  lower  oxides  of  nitrogen. 
Pure  nitric  acid  is  diluted  to  contain  about  50%  HN03,  and  boiled  until  per- 
fectly colorless.  The  reagent  should  be  kept  in  the  dark.  Dilute  nitric  acid 
does  not  interfere  with  the  method. 

Procedure.  To  the  solution,  containing  0.003  to  0.35  gram  chlorine,  in 
combination  as  a  chloride,  is  added  sufficient  of  the  pure  HN03  to  make  the  solu- 
tion acid  and  about  5  cc.  in  excess.  To  the  solution,  diluted  to  about  150  cc., 
is  added  an  excess  of  standard  silver  nitrate  reagent.  The  precipitated  AgCl 

1  Liebig's  Ann.  d.  Chem.,  190,  1;  Sutton,  "  Volumetric  Analysis,"  10  Ed.  Z.  Anorg. 
Chem.,  63,  330,  1909. 


126  CHLORINE 

is  filtered  off  and  washed  free  of  silver  nitrate.     The  nitrate  and  washings  are 
combined  and  titrated  with  standard  thiocyanate.1 

The  filtrate  from  the  precipitated  chloride  is  treated  with  5  cc.  of  the  ferric 
solution,2  and  the  excess  silver  determined  by  addition  of  the  thiocyanate 
until  a  permanent  reddish-brown  color  is  produced.  Each  addition  of  the 
reagent  will  produce  a  temporary  reddish-brown  color,  which  immediately  fades 
as  long  as  silver  uncombined  as  thiocyanate  remains.  The  trace  of  excess 
produces  ferric  thiocyanate,  the  reddish-brown  color  of  this  compound  being  best 
seen  against  a  white  background.  From  this  titration  the  amount  of  silver 
nitrate  used  by  the  chloride  is  ascertained. 

One  cc.  N/10  AgN03  =0.00355  gram  Cl  or  0.00585  gram  NaCl. 

Volumetric  Determination   of  Chlorine  in   a  Neutral   Solution, 
Silver  Chromate  Method 

The  method,  worked  out  by  Fr.  Mohr,  is  applicable  for  determination  of 
chlorine  in  water  or  in  neutral  solutions  containing  small  amounts  of  chlorine; 
the  element  should  be  present  combined  as  a  soluble  chloride.  Advantage  is 
taken  of  the  fact  that  silver  combines  with  chlorine  in  presence  of  a  chromate, 
Ag2Cr04  being  decomposed  as  follows:  Ag2Cr04+2NaCl=2AgCl+Na2Cr04. 
When  all  the  chlorine  has  gone  into  combination  as  AgCl,  an  excess  of  K2Cr04 
immediately  forms  the  red  Ag2Cr04,  which  shows  the  reaction  of  AgN03  with 
the  chl  )ride  to  be  complete. 

Reagents.  Tenth  Normal  Silver  Nitrate  Solution.  Theoretically  16.989 
grams  AgN08  per  liter  are  required.  In  practice  17.1  grams  of  the  salt  are  dis- 
solved per  1000  cc.  and  the  solution  adjusted  against  an  N/10  NaCl  solution 
containing  5.846  grams  NaCl  per  liter. 

Potassium  Chromate.     Saturated  solution. 

Procedure.  To  the  neutral  solution  (made  so,  if  necessary,  by  addition  of 
nitric  acid  or  ammonium  hydroxide),  are  added  2  or  3  drops  of  the  potassium 
chromate  solution.  A  glass  cell 3  (or  a  50-cc.  beaker)  is  filled  to  about  1  cm. 
in  depth  with  water  tinted  to  the  same  color  as  the  solution  being  titrated. 
The  cell  is  placed  on  a  clear  glass  plate  half  covering  the  casserole  containing  the 
sample.  The  standard  silver  solution  is  now  added  to  the  chloride  solution 
from  a  burette  until  a  faint  blood-red  tinge  is  produced,  the  red  change  being 
easily  detected  by  looking  through  the  blank,  colored  cell. 

One  cc.  N/10  K2CrO4=  0.003546  gram  Cl. 

NOTES.  Chlorides  having  an  acid  reaction  (A1C13)  are  treated  with  an  excess  of 
neutral  solution  of  sodium  acetate  and  then  titrated  with  silver  nitrate. 

Elements  whose  ions  form  colored  solution  with  chlorine  are  precipitated  from 
the  solution  by  sodium  hydroxide  or  potassium  carbonate,  and  the  filtrate,  faintly 
acidified  with  acetic  acid,  is  titrated  as  usual. 

1  Time  is  saved  by  filtering,  through  a  dry  filter  paper,  only  a  portion  of  the  mixture 
made  to  a  definite  volume,  and  titrating  an  aliquot  portion.     The  first  10-15  cc.  of  the 
filtrate  are  rejected. 

2  Upon  addition  of  the  ferric  solution  no  color  should  develop.     If  a  reddish 
or  yellowish  color  results,  more  nitric  acid  is  required  to  destroy  this.     The  amount 
of  nitric  acid  does  not  affect  results  when  within  reasonable  limits. 

3  Depre",  Analyst,  5,  123;  also,  Systematic  Handbook  of  "  Volumetric  Analysis,"  F. 
A.  Sutton. 


CHLORINE  127 


Free  hydrochloric  acid  is  neutralized  with  ammonium  hydroxide  and  titrated 
It  is  advisable  to  titrate  the  sample  under  the  same  conditions  as  those  observed 
during  standardization.      The  solution  should  be  kept  to  small  bulk  and  low  tem- 
perature for  accuracy  on  account  of  the  solubility  of  the  silver  chromate. 

Free  chlorine  should  be  converted  to  a  chloride  before  titration   '  This  mav  be 


xr         ^.>  on  conanng  poassum  oe,  te      erate 

by  N/10  thiosulphate,  Na2S2O3,  and  the  equivalent  chlorine  estimated. 

Volumetric  Determination  of  Free  Chlorine 

The  determination  depends  upon  the  reaction  Cl-f-KI=KCl-fI.  The  iodine 
liberated  by  the  chlorine  is  titrated  with  Na2S203  and  the  equivalent  Cl  cal- 
culated. 

Procedure.  A  measured  amount  of  the  chlorine  water  is  added  to  a 
solution  of  potassium  iodide  in  a  glass-stoppered  bottle  by  means  of  a  pipette, 
the  delivery  tip  of  which  is  just  above  the  surface  of  the  iodide  solution.  The 
bottle  is  then  closed  and  the  contents  vigorously  shaken.  The  liberated  iodine  is 
titrated  with  tenth-normal  sodium  thiosulphate  (2Na2S203+I2=2NaI+Na2S408). 
When  the  yellow  color  of  the  iodine  has  become  faint,  a  little  starch  solution 
is  added  and  the  titration  completed  to  the  fading  out  of  the  blue  color. 

One  cc.  N/10  Na2S203  =0.003546  gram  Cl. 

Determination  of  Hypochlorous  Acid  in  the  Presence  of  Chlorine 

The  determination  depends  upon  the  reactions: 

2KI+HOC1=KC1+KOH+I2  and  2KI+C12=2KC1+I2. 

The  alkali  liberated  by  hypochlorous  acid  and  the  total  iodine  are  determined 
and  the  calculations  made  for  each  of  the  constituents. 

Procedure.  A  measured  volume  of  N/10  HC1  is  added  to  a  potassium  iodide 
solution.  To  this  the  sample  containing  the  hypochlorous  acid  and  chlorine 
are  added.  The  liberated  iodine  is  titrated  with  N/10  Na2S203.  (The  addition 
of  starch  is  omitted.)  The  colorless  solution  is  treated  with  methyl  orange 
indicator  and  the  excess  of  hydrochloric  acid  is  titrated  with  N/10  NaOH. 
The  potassium  hydroxide,  produced  by  the  action  of  the  hypochlorous  acid 
upon  the  iodide,  requires  half  as  much  acid  for  neutralization  as  the  volume 
of  thiosulphate  required  by  the  iodine  set  free  by  the  hypochlorous  acid. 

Calculation.  The  cc.  back  titration  with  NaOH  are  subtracted  from  the 
total  cc.  of  HC1  taken  =cc.  HC1  required  by  NaOH  liberated  by  HOC1=A. 
Then  2A  cc.  =cc.  Na2S203  required  by  the  I  liberated  by  HOC1.  Cc.  A  X  0.005247 
=  gram  HOC1.  The  total  Na2S203  titration  minus  2A  cc.  (due  to  the  iodine 
liberated  by  HOC1)  =cc.  Na2S203  that  are  required  by  the  iodine  liberated  by 
chlorine.  The  cc.  thus  required  multiplied  by  0.003546=  grams  chlorine  in  the 
sample  taken. 

1  Six  parts  AgCrO4,  dissolve  in  100,000  parts  H2O  at  15.5°.—  W.  G.  Young,  Analyst, 
18,  125. 


128  CHLORINE 

Gravimetric  Determination  of  Chloric  Acid,  HC1O3,  or  Chlorates, 
by  Reduction  to  Chloride  and  Precipitation  as  Silver  Chloride 

Reduction  of  the  Chlorate.  Among  the  methods  of  reduction  of  chlorates 
the  following  deserve  special  mention:  1.  Reduction  with  Sulphurous  Acid.1 
2.  Ferrous  sulphate.  3.  Zinc. 

1.  About  0.2  to  0.5  gram  of  the  salt  is  dissolved  in  100  cc.  of  distilled  water 
and  either  S02  gas  passed  into  the  solution  or  sulphurous  acid  in  solution  added 
in  excess.    The  solution  is  now  boiled  to  expel  SOa  and  the  chloride  precipitated 
as  AgCl  in  presence  of  free  nitric  acid. 

2.  The  sample  in  100  cc.  of  distilled  water  is  treated  with  50  cc.  of  crys- 
tallized ferrous  sulphate  (10%  solution),  heated  to  boiling,  with  constant  stirring, 
and  then  boiled  for  fifteen  minutes.     Nitric  acid  is  added  to  the  cooled  solution, 
until  the  deposited  basic  ferric  salt  is  dissolved.    The  chloride  is  now  precip- 
itated as  AgCl,  as  usual. 

3.  The  dilute  chlorate  solution  is  treated  with  acetic  acid  until  it  reacts 
distinctly  acid.    An  excess  of  powdered  zinc  is  now  added  and  the  solution 
boiled  for  an  hour.    Nitric  acid  is  added  to  the  cooled  solution  in  sufficient 
quantity  to  dissolve  the  zinc  remaining.     The  solution  is  filtered,  if  necessary, 
and  the  chloride  precipitated  as  usual. 

Factors.    AgCl X 0.855  =KC103,  or  X 0.2474=01. 

NOTE.  In  absence  of  cyanides,  carbonates  and  acids  decomposed  and  vola- 
tilized by  hydrochloric  acid,  or  oxides,  hydroxides  and  substances  other  than  chlorates 
that  may  be  decomposed  or  acted  upon  by  this  acid,  evaporation  of  the  salt  with  HC1 
and  ignition  of  the  residue,  or  addition  of  an  excess  of  ammonium  chloride,2  and  sub- 
sequent heating  will  give  a  residue  of  chloride,  which  may  be  determined  as  usual 
and  the  equivalent  chlorate  calculated.  Method  by  L.  Blangey. 

The  methods  may  be  used  in  determining  chlorates  in  presence  of  perchlorates, 
only  the  former  being  reduced  to  chlorides.  Outline  of  the  procedure  is  given  later. 

Gravimetric  Determination  of  Perchloric  Acid  by  Reduction  to 

Chloride 

A  perchlorate  ignited  with  about  four  tunes  its  weight  of  ammonium  chloride 
in  a  platinum  dish  may  be  decomposed  to  chloride.  A  second  treatment  is 
usually  necessary  to  change  the  salt  completely.  Platinum  appears  to  act  as  a 
catalyser,  so  must  be  added  in  solution  if  a  porcelain  crucible  is  used. 

Procedure.  About  0.2  to  0.5  gram  of  potassium  perchlorate  is  intimately 
mixed  with  about  2  grams  of  ammonium  chloride  in  a  platinum  crucible,  the 
latter  then  covered  with  a  watch-glass  and  the  charge  ignited  gently  for  one 
and  a  half  to  two  hours,  the  temperature  being  below  the  fusing-point  of  the 
residual  chloride  (otherwise  the  platinum  would  be  attacked).  A  second  addi- 
tion of  ammonium  chloride  is  made  and  the  mix  again  heated  as  before.  The 
resulting  chloride  may  now  be  determined  as  usual. 

Factors.    AgCl X 0.9667  =KC104,  X0.2474=C1. 

1  Blattner  and  Brassuer,  Chem.  Zeit.  Rep.,  1900,  24,  793. 

2  Perchlorates  are  decomposed  by  ignition  with  NH4C1  in  presence  of  platinum. 


CHLORINE  129 

Determination  of  Chlorates  and  Perchlorates  in  Presence  of  One 

Another 

(1)4  portion  of  the  sample  is  treated  with  about  twelve  times  its  weight  of 
ammonium  chloride  in  a  platinum  dish  (or  in  a  porcelain  dish  with  the  addition 
of  1  cc.  of  hydroplatinic  acid),  and  the  mixture  heated  according  to  the  procedure 
given  for  perchloric  acid  (page  128).  The  resulting  chloride  is  determined  as 
usual.  This  is  the  total  chlorine  in  the  sample. 

(2)  In  a  second  portion  the  chlorate  is  reduced  by  means  of  S02  or  FeS04, 
according  to  directions  given  for  determination  of  chloric  acid,  and  chlorine 
determined.  The  chlorine  of  this  portion  is  subtracted  from  the  total  chlorine, 
the  difference  multiplied  by  3.9075  =KC104.  The  chlorine  of  the  second  portion 
multiplied  by  3.4563  =KC103,  or  AgCl  in  (2)  subtracted  from  AgCl  of  (1) 
and  the  difference  multiplied  by  0.9667  =KC104.  AgCl  of  (2)  multiplied  by  0.855  - 
=  KC103. 

Determination   of   Hydrochloric,    Chloric,   and   Perchloric  Acids 
in  the  Presence  of  One  Another 

(1)  Total  Chlorine.    If  the  determination  is  made  in  the  valuation  of  niter 
a  5-gram  sample  is  fused  with  about  three  times  its  weight  of  alkali  carbonate  l 
or  calcium  hydroxide,2  in  a  platinum  dish,  whereby  all  the  chlorine  compounds 
are  converted  to  chlorides.    If  the  compounds  are  present  as  alkali  salts,  fusion 
with  ammonium  chloride  in  a  platinum  dish  may  be  made  and  the  total  chlorides 
determined  after  dissolving  the  residue  in  nitric  acid. 

(2)  Chloride   and   Chlorate.    If  the    estimation  is  being  made  in  niter,  5 
grams  of  the  salt  are  treated  with  10  grams  of  zinc  dust  (Cl-free)  in  presence 
of  150  cc.  of  1%  acetic  acid.    The  solution  is  boiled  for  half  an  hour,  filtered, 
and  the  chloride  determined.     In  a  mixture  of  alkali  salts  of  hydrochloric,  chloric, 
and  perchloric  acids,  reduction  may  be  accomplished  by  passing  in  S02  gas  or 
by  adding  ferrous  sulphate  and  boiling  according  to  directions  given  for  the 
determination  of  chlorate.    The  chloride  now  present  in  the  residue  is  due  to  the 
reduced  chlorate  and  to  the  original  chloride  of  the  sample. 

(3)  The  chloride  of  the  sample  is  determined  by  acidifying  the  salt  with 
nitric  acid  (cold)  and  precipitating  as  AgCl. 

Perchlorate.  The  chloride  and  chlorate  in  terms  of  chlorine  are  subtracted 
from  total  chlorine  of  (1)  and  multiplied  by  the  factor  for  the  salt  desired. 

Chlorate.  The  chlorine  of  (3)  is  subtracted  from  chlorine  of  (2)  and  mul- 
tiplied by  the  factor  for  the  compound  desired. 

Chloride.    The  AgCl  of  (3)  is  multiplied  by  the  appropriate  factor. 

Factors.  AgCl X 0.2474  =C1,  or  X0.2544=HC1,  or  X0.4078  =NaCl,  or 
X0.5202=KC1. 

AgCl X 0.855  =KC103,  or  X 0.9667  =KC104. 

C1X3.4563=KC103,  or  X3.9075=KC104,  or  X  2.1027  =KC1,  or  X3.0028  = 
NaC103,  or  X3.4535=NaC104,  or  X  1.6486  =NaCl. 

1  Mennick,  Chem.  Zeit.  Rep.,  1898,  22, 117. 

8  Blattner  and  Brasseur,  Chem.  Zeit.  Rep.,  1900,  24,  793. 


130  CHLORINE 

Determination  of  Chlorine,  Bromine,  and  Iodine  in  the  Presence 

of  Each  Other 

The  procedure  is  Bekk's  modification  of  Baubigny's  method.1 
Procedure.  The  halogens  are  precipitated  with  an  excess  of  silver  nitrate, 
filtered  onto  asbestos  or  glass  wool,  washed,  dried,  and  weighed  as  total  halogens 
ap  silver  salts.  A  second  portion  is  precipitated  and  the  moist,  washed  silver 
salts  (0.3  to  0.4  gram)  are  treated  with  a  solution  of  2  grams  of  potassium 
dichromate  in  30  cc.  of  concentrated  sulphuric  acid  at  95°  C.,  and  digested  for 
thirty  minutes.  By  this  procedure  the  iodine  is  oxidized  to  hydriodic  acid 
(HI03)  and  chlorine  together  with  bromine  is  liberated  in  form  of  the  free 
halogen.  Toward  the  end  of  the  reaction  a  stream  of  air  is  led  through  the 
solution  to  remove  any  chlorine  and  bromine.  This  is  now  diluted  to  300  to  400 
cc.,  filtered,  and  the  hydriodic  acid  reduced  by  adding,  drop  by  drop,  with  con- 
stant stirring,  a  concentrated  solution  of  sodium  sulphite,  Na2S03,  until  a  faint 
odor  of  S02  remains  after  standing  ten  minutes.  (Under  certain  conditions  an 
excess  may  result  in  a  partial  reduction  of  the  silver  iodide.)  The  precipitated 
silver  salt  is  filtered,  washed  with  hot,  dilute  nitric  acid,  dried  and  weighed  as  Agl. 
The  filtrate  containing  the  silver,  formerly  with  the  chlorine  and  bromine,  is 
treated  with  potassium  iodide  in  sufficient  amount  completely  to  precipitate 
the  silver  as  Agl.  This  is  filtered,  washed  and  weighed.  From  the  three  weights 
the  chlorine,  bromine  and  iodine  can  be  easily  calculated. 

NOTE.     Bekk  claims  an  accuracy  within  less  than  0.15%. 

EVALUATION   OF   BLEACHING   POWDER,    CHLORIDE   OF 
LIME,    FOR  AVAILABLE  CHLORINE 

When  chloride  of  lime  is  treated  with  water,  it  is  resolved  into  calcium 
hypochlorite,  Ca(OCl)2,  and  calcium  chloride,  CaCl2.  The  calcium  hypochlorite 
constitutes  the  bleaching  agent.  The  technical  analysis  is  confined  to  the 
determination  of  available  chlorine,  which  is  expressed  as  percentage  by  weight 
of  the  bleaching  powder.2 

Procedure.  Ten  grams  of  the  sample  are  washed  into  a  mortar  and  ground 
with  water,  the  residue  allowed  to  settle  and  the  supernatant  liquor  poured  into 
a  liter  flask.  The  residue  is  repeatedly  ground  and  extracted  with  water  until 
the  whole  of  the  chloride  is  transferred  to  the  flask.  The  combined  extracts 
are  made  up  to  1000  cc. 

To  50-cc.  portions  (0.5  gram)  of  the  solution,  3  to  4  grams  of  solid  potassium 
iodide  and  100  cc.  of  water  are  added  and  the  solution  acidified  with  acetic 
acid.  Iodine  equivalent  to  the  available  chlorine  is  liberated.  This  is  titrated 
with  N/10  arsenious  acid.8 

One  cc.  N/10  arsenious  acid  =0.003546  gram  Cl.    This  multiplied  by  200  =%C1. 

1  Julius  Bekk,  Chem.  Ztg.,  39,  405-6  (1915).     C.  A.,  9,  2042,  (1915). 

2  In   France  the   strength   is  given   in   Gay-Lussac  degrees,   e.g.,  liters   of   gas 
evolved  by  2  kilograms  of  bleaching  powder,  0°  C.  and  760  mm.    100°  =  31.78%  Cl. 

8  The  standard  arsenious  acid  is  made  by  dissolving  4.95  grams  of  pure  As2Oj 
together  with  20  grams  of  sodium  bicarbonate  in  50  cc.  of  warm  water.  When  dis- 
solved the  solution  is  made  up  to  1  liter. 


CHLORINE  131 

NOTE.  In  the  analysis  of  compounds  containing  hypochlorites  and  chlorides, 
the  conversion  of  hypochlorites  to  chlorides  by  heating  with  hydrogen  peroxide  is 
a  great  convenience. 

For  instances  in  the  analysis  of  bleach  liquors,  washes,  etc.,  the  (OC1)  and  Cl 
may  be  very  easily  and  quickly  determined  by  titrating  an  aliquot  with  As2O3  and  then 
a  similar  aHquot  with  AgNOs  after  converting  all  the  OC1  to  Cl  by  warming  with 
H2O2. 

It  is  also  a  convenience  in  getting  rid  of  OC1  as,  for  instance,  in  the  deter- 
mination of  CO2  in  bleaching  powder,  which  is  often  of  great  importance.  It  is 
preferable  to  the  use  of  ammonia,  which  is  always  liable  to  suspicion  of  having  taken 
up  a  little  CO2,  and  there  is  no  danger  of  NH4C1  fumes  which  are  sometimes  a  nuisance. 


CHROMIUM 

WILFRED  W.  SCOTT 

Cr,  at.wt.  52.0;  sp.gr.  6.92;  m.p.  1520°;  b.p.  2200°  C;  oxides,  CrO2; 

Cr203,  Cr03. 

DETECTION 

Chromium  is  precipitated  by  hydrogen  sulphide  and  ammonium  hydroxide 
as  bluish-green,  Cr(OH)3,  along  with  the  hydroxides  of  iron  and  aluminum 
(members  of  previous  groups  having  been  removed).  The  chromic  compound 
is  oxidized  to  chromate  by  action  of  chlorine,  bromine,  sodium  peroxide,  or 
hydrogen  peroxide  added  to  the  substance  containing  an  excess  of  caustic  alkali. 
The  chromate  dissolves  and  is  thus  separated  from  iron,  which  remains  insol- 
uble as  Fe(OH)3.  The  alkali  chromates  color  the  solution  yellow. 

Barium  acetate  or  chloride  added  to  a  neutral  or  slightly  acetic  acid 
solution  of  a  chromate  precipitates  yellow  barium  chromate,  BaCr04.  Addition 
of  ammonium  acetate  to  neutralize  any  free  inorganic  acid  aids  the  reaction. 

Lead  acetate  produces  a  yellow  precipitate  with  chromates,  in  neutral 
or  acetic  acid  solutions. 

Mercurous  nitrate  or  silver  nitrate  gives  red  precipitates  with  chromates. 

Hydrogen  peroxide  added  to  a  chromate  and  heated  with  an  acid,  such 
as  sulphuric,  nitric,  or  hydrochloric,  will  form  a  greenish-blue  colored  solution. 
Chromates  are  reduced  by  hydrogen  peroxide  in  acid  solution,  the  action  being 
reversed  in  alkaline  solution. 

Reducing  agents,  hydrogen  sulphide,  sulphurous  acid,  ferrous  salts, 
alcohol  form  green  chromic  salts  when  added  to  chromates  in  acid  solution. 

Ether  shaken  with  a  chromate  to  which  nitric  acid  and  hydrogen  peroxide 
are  added,  is  colored  a  transient  blue.  Oxygen  is  given  off  as  the  color  fades. 

HCr04-h3HN03  =Cr(N03)3+2H20+02. 

Diphenyl  carbazide  test.  To  5  cc.  of  the  solution  containing  chromium  as 
chromate,  2  drops  of  hydrochloric  or  acetic  acid  are  added,  and  1  drop  of  an  acetic 
acid  solution  of  diphenyl  carbazide  (0.2  gram  CO  (NH-NH-C6H5)2  is  dissolved 
in  5  cc.  glacial  acetic  acid  and  diluted  to  20  cc.  with  ethyl  alcohol).  A  violet 
pink  color  is  produced  in  presence  of  a  chromate.  Less  than  0.0000001  gram 
chromium  may  be  detected. 

Chromic  salts  are  bluish  green;  chromic  acid  is  red;  chromates,  yellow; 
bichromates,  red;  chrome  alum,  violet. 

The  powdered  mineral,  containing  chromium,  when  fused  with  sodium 
carbonate  and  nitrate,  produces  a  yellow  colored  mass. 

ESTIMATION 

Among  the  substances  in  which  chromium  is  determined  are  the  following: 
Chrome  iron  or  chromite,  Cr203 •  FeOMgO ;  crocoisite,  PbCr04;  slags;  chromic 
oxide,  chrome  green,  in  pigments;  chromates  and  dichromates;  chrome  steel 
and  ferro-chrome. 

132 


CHROMIUM  133 

Preparation  and  Solution  of  the  Sample 

Although  powdered  metallic  chromium  is  soluble  in  dilute  hydrochloric  or 
sulphuric  acid,  it  is  only  slightly  soluble  in  dilute  or  concentrated  nitric  acid. 
It  is  practically  insoluble  in  aqua  regia  and  in  concentrated  sulphuric  acid! 
Chrome  iron  ore  is  difficult  to  dissolve.  It  is  important  to  have  the  material 
in  finely  powdered  form  to  effect  a  rapid  and  complete  solution  of  the  sample. 
An  agate  mortar  may  be  used  to  advantage  in  the  final  pulverizing  of  the 
substance. 

General  Procedures  for  Decomposition  of  Refractory  Materials  Con- 
taining Chromium.  The  following  fluxes  may  be. used: 

A.  Fusion  with  KHS04  and  extraction  with  hot  dilute  HC1.    The  residue 
fused  with  Na2C03  and  KC103,  3  :  1,  or  fusion  with  soda  lime  and  KC103,  3:1. 

B.  Fusion  with  NaHS04  and  NaF,  2  :  1. 

(7.  Fusion  with  magnesia  or  lime  and  sodium  or  potassium  carbonates 
4  :1. 

E.  Fusion  with  Na202,  or  NaOH  and  KN03,  or  NaOH  and  Na202.  Nickel, 
iron,  copper,  or  silver  crucibles  should  be  used  for  E.  Platinum  may  be  used 
for  4,  B,  orC. 

Special  Procedures.  Materials  High  in  Silica.  The  finely  ground  sample, 
1  to  5  grams,  is  placed  in  a  platinum  dish  and  mixed  with  2  to  5  cc.  concentrated 
sulphuric  acid  (1.84),  and  10  to  50  cc.  of  strong  hydrofluoric  acid  added.  The 
solution  is  evaporated  to  small  volume  on  the  steam  bath  and  to  S03  fumes  on 
the  hot  plate.  Sodium  carbonate  is  added  in  sufficient  amount  to  react  with 
the  free  acid,  and  then  an  excess  of  5  to  10  grams  added  and  the  mixture  heated 
to  fusion  and  kept  in  molten  condition  for  half  an  hour.  From  time  to  time  a 
crystal  of  potassium  nitrate  is  added  to  the  center  of  the  molten  mass  until 
1  to  2  grams  are  added.  (Caution.  Platinum  is  attacked  by  KN03,  hence 
avoid  adding  a  large  amount  at  any  one  time.)  Chromium  and  aluminum  go 
into  solution  in  the  flux,  but  iron  is  thrown  out  as  Fe(OH)3.  The  cooled  fusion 
is  extracted  with  hot  water  and  filtered  from  the  iron  residue.  Chromium 
is  in  solution  together  with  aluminum.  If  much  iron  is  present  it  should  be  dis- 
dissolved  in  a  little  hydrochloric  acid  and  the  solution  poured  into  boiling  10% 
solution  of  potassium  hydroxide,  the  cooled  solution +Fe  (OH  )3  precipitate  is 
treated  with  hydrogen  peroxide  or  sodium  peroxide  to  oxidize  any  chromium 
that  may  have  been  occluded  by  the  iron  in  the  first  precipitate.  The  mixture 
is  again  filtered  and  the  combined  filtrates  examined  for  chromium. 

Sodium  Peroxide  Fusion.  Chrome  Iron  Ores.  One  to  two  grams  of  finely 
pulverized  ore  are  placed  in  a  nickel  or  iron  crucible  of  50  to  75  cc.  capacity 
and  mixed  with  5  to  10  grams  of  yellow  sodium  peroxide.  (Fresh  peroxide  is 
best).  The  mass  is  gently  heated  over  a  Bunsen  burner  until  it  melts.  The 
fusion  is  kept  at  a  low  red  heat  for  about  fifteen  minutes.  About  5  grams  more 
of  the  Na202  are  added  and  the  fusion  heated  for  about  ten  minutes  more. 
The  cooled  fusion  is  dissolved  in  a  casserole  with  100  cc.  to  150  cc.  of  water,  more 
peroxide  being  added  to  this  solution  if  it  appears  purple.  The  excess  of  peroxide 
is  decomposed  by  boiling  the  solution,  and  to  the  caustic  solution  free  from  per- 
oxide is  added  10  to  15  grams  of  ammonium  carbonate  or  a  sufficient  quantity  of 
the  salt  to  neutralize  four-fifths  of  the  sodium  hydroxide  present  in  the  solu- 
tion, as  the  strong  caustic  would  otherwise  dissolve  the  filter.  The  solution 
is  now  filtered  The  insoluble  matter  is  treated  on  the  filter  with  dilute  sulphuric 


134  CHROMIUM 

acid,  1:4.  If  a  portion  remains  insoluble,  it  is  an  indication  of  incomplete 
decomposition  of  the  ore,  and  this  residue  is  again  fused  with  peroxide  and 
treated  as  above.  The  combined  nitrates  contain  the  chromium. 

Since  chromates  are  reduced  in  presence  of  free  acid  and  peroxide,  the  latter 
should  be  expelled  before  making  the  solution  acid.1 

If  the  chromate  is  to  be  precipitated  as  BaCr04  or  PbCr04,  the  solution 
should  be  acidified  with  hydrochloric  acid.  If  the  reduced  solution  is  to  be 
titrated  with  potassium  permanganate,  it  is  best  to  use  sulphuric  acid  in  neutral- 
izing the  caustic  solution.  Further  directions  will  be  given  under  the  method 
chosen. 

Method  for  Solution  of  Iron  and  Steel.  Three  to  five  grams  of  steel  are 
boiled  for  about  ten  to  fifteen  minutes  with  50  cc.  of  strong  hydrochloric  acid 
and  about  150  cc.  concentrated  nitric  acid  added  and  the  boiling  continued 
until  the  hydrochloric  acid  is  expelled,  brown  fumes  and  the  odor  of  Cl  no  longer 
being  evident.  Ten  grams  of  potassium  chlorate  are  now  added  to  the  cooled 
solution,  a  few  crystals  at  a  time,  the  solution  then  replaced  on  the  hot  plate 
and  boiled  down  to  about  50  cc.  to  decompose  the  chlorate.  The  solution  is 
diluted  to  150  cc.,  and  if  an  appreciable  amount  of  manganese  dioxide  has 
separated  out,  it  is  decomposed  by  the  addition  of  a  few  drops  of  hydrochloric 
.acid.  The  chlorine  is  expelled  by  boiling  and  the  solution  cooled.  Chromium 
is  determined  in  this  solution  by  the  ferrous  ammonium  sulphate  method. 

SEPARATIONS 

Chromium,  Iron,  and  Aluminum.  If  chromium  has  been  fused  with  sodium 
peroxide  or  carbonate  containing  a  little  potassium  nitrate,  and  the  fusion 
extracted  with  boiling  water,  most  of  the  chromium  goes  into  solution  as  a 
chromate,  together  with  alumina,  but  some  of  the  chromium  is  occluded  by  Fe(OH)3. 
If  the  amount  of  the  iron  precipitate  is  appreciable,  and  warrants  the  recovery 
of  occluded  chromium,  it  is  dissolved  in  hydrochloric  acid  and  the  iron  repre- 
cipitated  by  pouring  into  a  solution  of  strong  sodium  hydroxide.  Before  filtering 
off  the  iron  hydroxide,  a  little  H202  is  added  to  oxidize  the  Cr203,  if  accidentally 
present,  and  the  solution  boiled  and  filtered.  The  combined  filtrates  will  con- 
tain all  of  the  chromium  and  aluminum. 

If  chromium  is  present  as  a  chromic  salt,  instead  of  a  chromate,  it  is  oxidized 
to  the  higher  form,  by  adding  peroxide  (H202  or  Na202)  to  the  alkaline  solu- 
tion. Bromine  added  to  this  solution  or  chlorine  gas  passed  in  will  accomplish 
complete  oxidation.2  It  must  be  remembered  that  in  acid  solutions  hydrogen 
peroxide,  sodium  peroxide,  or  nitrites  will  cause  reduction  of  chromates  to 
chromic  salts  (exception,  see  method  for  solution  of  steel),  so  that  these  should 
be  boiled  out  of  the  alkaline  solution  before  making  decidedly  acid  with  hydro- 
chloric or  sulphuric  acids.  Since  these  are  difficult,  if  not  impossible,  to  com- 
pletely expel  from  an  alkaline  solution,  after  boiling  the  strongly  alkaline  solu- 
tion, dilute  sulphuric  acid  is  added  until  the  solution  acquires  a  permanent 
brown  color  (nearly  acid),  acid  potassium  sulphate,  KHS04,  is  added,  and 

1  See  Separations. 

*  Br  may  DC  added  and  then  NaOH  to  oxidize  Cr  and  precipitate  Fe(OH)3. 

Chromic  oxide  and  most  of  its  compounds,  except  chrome  iron  stone,  may  be 
decomposed  by  cone.  HNOs+KClOa  (added  in  small  portions).  M.  Groger,  Zeitsch. 
anorg.  Chem.,  81,  233-242,  1913. 


CHROMIUM  135 

the  boiling  continued.1  This  will  decompose  the  bromates  and  expel  bromine, 
etc.,  but  will  not  cause  the  reduction  of  the  chromate,  as  would  a  strong  acid 
solution. 

Separation  of  Chromium  from  Aluminum.  This  separation  is  necessary  if 
chromium  is  to  be  precipitated  as  Cr(OH)3.  The  sodium  chromate  and  alumi- 
nate  solutions  are  made  slightly  acid  with  nitric  acid  and  then  faintly  alkaline 
with  ammonium  hydroxide,  A1(OH)3  is  precipitated  and  chromium  remains 


in  solution  as  a  chromate. 


GRAVIMETRIC    METHODS    FOR    THE    DETERMINATION    OF 

CHROMIUM 

Precipitation  of  Chromic  Hydroxide  and  Ignition  to  Cr2O32 

Chromium  present  as  a  chromic  salt  in  solution,  free  from  iron  and  aluminum 
or  elements  precipitated  as  hydroxides,  is  thrown  out  of  solution  by  NH4OH 
as  Cr(OH)3,  the  precipitate  ignited  to  the  oxide,  Cr203,3  and  so  weighed.  The 
presence  of  hydrochloric  acid  or  sulphuric  acid  does  not  interfere. 

Reduction.  If  the  chromium  is  already  present  as  the  chromic  salt,  free 
from  iron  and  alumina,  it  may  be  precipitated  directly  as  the  hydroxide  by 
addition  of  ammonia;  otherwise,  if  present  as  the  chromate,  as  is  the  case  when 
a  separation  from  iron  and  alumina  has  been  necessary,  and  in  cases  where 
the  chromium  has  been  brought  into  solution  by  fusion  with  an  oxidizing 
reagent,  reduction  is  necessary.  This  is  accomplished  by  passing  S02  or 
H2S  into  the  slightly  acid  solution  of  the  chromate,  or  by  adding  alcohol 
to  the  hydrochloric  acid  solution  and  boiling  until  the  solution  appears  a 
deep  grass  green.  Twenty  cc.  of  alcohol  for  every  0.1  gram  of  Cr  has  been 
found  to  be  ample  for  this  reduction.  The  S02  or  H2S  should  be  expelled 
from  solution  by  boiling,  in  case  either  has  been  used  for  reduction  of  the 
chromate. 

Precipitation.  Ammonium  hydroxide  or  ammonium  sulphide  are  added 
in  slight  excess  and  the  solution  boiled  for  about  ten  minutes.  The  solution 
should  be  slightly  alkaline  (litmus),  otherwise  a  few  drops  of  ammonia  should 
be  added,  but  not  a  large  excess;  the  solution  will  then  settle  out  clear.  A 
cloudy  solution  results  from  prolonged  boiling  when  the  solution  has  become 
acid;  on  the  other  hand,  a  large  excess  of  ammonia  will  prevent  complete  pre- 
cipitation of  chromium  and  the  filtrate  will  be  colored  pink  or  violet.  The 
chromic  hydroxide  is  filtered  off  on  S  and  S  589  filter  paper.  Since  the  precipi- 
tate is  apt  to  be  gelatinous  it  is  advisable  to  wash  two  or  three  times  by  decanta- 
tion  and  several  times  on  the  paper.  The  well-drained  precipitate  and  filter  is 
ignited  wet  in  a  porcelain  or  platinum  crucible,  first  over  a  low  flame  until  the 
paper  has  been  charred,  then  over  a  strong  gas  flame  for  about  thirty  minutes, 

1KHSO4  will  not  cause  reduction  of  chromates.  A.  Kurtenacker,  Zeitsch.  anal. 
Chem.,  52,  401-407,  1913.  The  Analyst,  38,  449,  page  387. 

2  It  is  advisable  to  take  such  a  weight  of  sample  that  the  ignited  Cr2O3  does  not 
exceed  0.5  gram  in  weight.  . 

3Cr2O3,  mol.wt.,  152;  sp.gr.,  5.04;  m.p.,  2059°;  insol.  in  H2O,  slightly  sol.  m  acids, 
dark  green  hexagonal. 


136  CHROMIUM 

and  finally  a  blast  heat  for  five  minutes.    The  green  residue  is  weighed  as 


Cr203X  0.6846  =Cr. 
Determination  of  Chromium  as  Barium  Chromate2 


Chromium,  present  as  a  chromate,  is  precipitated  from  a  neutral  or  faintly 
acetic  acid  solution  of  an  alkali  chromate  by  addition  of  barium  acetate  or 
chloride.  The  BaCr04  is  gently  ignited  and  weighed.  The  solution  should  be 
free  from  sulphuric  acid  or  sulphates. 

Procedure.  The  alkali  chromate  solution  is  neutralized  with  nitric  acid 
or  ammonia  as  the  case  may  require,  precautions  for  avoiding  reduction 
having  been  observed  as  indicated  under  Preparation  and  Solution  of  the 
Sample.  10  cc.  of  £  N.  BaCl2  or  Ba(C2H302)2  (approx.  10%  sol.)  are  added 
to  the  boiling  solution  for  each  0.1  gram  of  chromium  present.  The  reagent 
should  be  added  in  a  fine  stream  or  drop  by  drop  to  prevent  occlusion  of  the 
reagent  by  the  precipitate.  The  precipitated  chromate  is  allowed  to  settle 
on  the  steam  bath  for  two  or  three  hours  and  then  filtered  into  a  weighed  Gooch 
crucible  and  washed  with  10%  alcohol  solution.  The  precipitate  is  dried  for 
an  hour  in  the  oven,  then  placed  in  an  asbestos  ring  suspended  in  a  large 
crucible  with  cover  and  thus  heated  over  a  low  flame,  gradually  increasing  the 
heat  until  the  outer  crucible  becomes  a  dull  red.  The  cover  is  removed  and 
the  heating  continued  for  five  minutes,  or  until  the  precipitate  appears  a  uniform 
yellow  throughout.  High  heating  should  be  avoided.  The  cooled  residue  is 
weighed  as  BaCr04. 

BaCr04X0.2055=Cr, 
BaCr04X  0.3002  =  Cr203. 
BaCr04X0.7666  =K2Cr04. 
BaCr04X0.5807  =K2Cr207. 

NOTES.  If  the  precipitate  on  the  sides  of  the  crucible  appears  green,  it  is  ignited 
until  the  green  color  disappears. 

If  sulphates  are  present,  BaSO4  will  be  precipitated,  hence  this  method  could 
not  be  used.  In  this  case  either  reduction  to  the  chromic  salt  and  precipitation  of 
chromium  as  Cr(OH)s  or  a  volumetric  procedure  should  be  followed. 

Oxidize  chromium  with  an  excess  of  hydrogen  peroxide  in  alkaline  solution,  reduce 
in  acid  solution  with  ferrous  sulphate  and  titrate  with  permanganate.  Decomposition 
of  hydrogen  peroxide  is  accelerated  by  heat  and  by  presence  of  sodium  sulphate  or 
ferric  salts.  Salts  of  nickel  cobalt,  or  manganese,  decompose  H2O2  energetically  and 
lower  results  are  obtained.  F.  Bourin  and  A.  Senechal.  Compt.  lend.,  157,  1528-31. 

1  If  the  filtrate  appears  yellow,  chromate  is  indicated,  the  solution  should  be  reduced 
and  the  chromium  precipitated  as  Cr(OH)3.  If  the  filtrate  is  pink,  it  should  be  boiled 
until  it  appears  green  and  Cr(OH)3  precipitates.  These  precipitates  should  be  included 
in  the  above  calculation  for  chromium. 

2BaCrO4,  mol.wt.,253A7',  sp.gr.,  4.498;  solubility  per  100  cc.  H2O,  0.00038180  and 
0.0043  hot.  Soluble  in  HC1  and  in  HNO3;  yellow  rhombic  plates. 


CHROMIUM  137 

VOLUMETRIC  METHODS   FOR  THE  DETERMINATION 

OF  CHROMIUM 
Potassium  Iodide  Method  for  Determination  of  Chromium 

Chromium  present  as  a  chromate  is  reduced  in  acid  solution  by  addition 
of  potassium  iodide  and  the  liberated  iodine  titrated  by  standard  sodium  thio- 
sulphate.  The  method  depends  upon  the  following  reactions: 

(a)  2Cr03+6KI  =  Cr203+3K20+6I. 

(6)  I2+2Na2S203=2NaI+Na2S406. 

The  presence  of  large  quantities  of  Ca,  Br,  Sr,  Mg,  Zn,  Cd,  Al,  Ni,  Co,  H2S04, 
HC1,  does  not  interfere.1 

Procedure.  The  alkali  chromate  solution  containing  not  over  0.17  gram 
Cr  2  and  free  from  Fe203,  is  made  nearly  acid  with  H2S04,  boiled  with  20  cc.  of 
30%  potassium  acid  sulphate  to  decompose  bromates  or  expel  Br,  Cl,  or  H202 
as  the  case  may  require,  more  KHS04  being  added  if  necessary.  If  the  solution 
is  not  acid  it  is  made  so  with  sulphuric  acid  and  5  cc.  of  the  acid  per  100  cc.  of 
solution  is  added  in  excess.3  About  2  grams  of  solid  potassium  iodide  are  added 
and,  after  five  minutes,  the  liberated  iodine  is  titrated  with  N/10  Na2S203 
solution.  When  the  green  color  of  the  reduced  chromate  begins  to  predominate 
over  the  free  iodine  color  (brownish  red)  a  little  starch  solution  is  added  and 
the  titration  with  the  thiosulphate  continued  until  the  blue  color  of  the  starch 
compound  is  just  destroyed,  care  being  taken  not  to  confuse  the  green  color  of 
the  reduced  chromium  with  the  blue  of  the  starch. 

One  cc.  of  N/10  Na2S2034  =0.001733  gram  Cr. 

Determination   of   Chromium    by   Reduction   of   the   Chromate 

with  Ferrous  Salts 

The  procedure  may  be  used  for  the  determination  of  chromium  in  presence 
of  ferric  iron  and  alumina.  Hydrochloric  or  sulphuric  acids  do  not  interfere. 
If  hydrochloric  acid  is  present  in  solution,  the  K2Cr207  back  titration  should  be 
made.  In  presence  of  H2S04  either  KMn04  or  K2Cr207  titrations  may  be 
made.  The  method  depends  upon  the  reduction  of  soluble  chromates  by  ferrous 
salts,  the  excess  being  determined  by  titration. 

Reactions,     a.  2Cr203+6FeO+zsFeO  =  Cr203+3Fe203+zsFeO. 

6.  zsFeO  is  oxidized  by  standard  oxidizing  reagent  to  Fe203. 

*M.  Groger,  Zeit.  anal.  Chem.,  81,  233-242,  1913. 

2  If  desired,  stronger  solution  of  titration  reagents  may  be  used,  and  consequently 
a  larger  sample  taken.  A  normal  sol.  of  Na2S2O3  may  be  used  to  advantage  with  1 
gram  samples  of  chromium  salts  or  hydrates,  where  Cr  exceeds  10%. 

a  A.  Kurtenacker,  Zeit.  anal.  Chem.,  52,  401-407.  1913. 

Sutton  recommends  for  every  0.5  gram  K2Cr2O7  present  to  add  .5  gram  KI  and  1.8 
gram  H2SO4  per  100  cc.  of  solution.  If  more  K2Cr2O7  is  present,  increase  the  KI  and 
H2SO4,  but  not  the  water. 

4  If  desired,  a  normal  solution  of  thio  sulphate  may  be  used  with  one  gram  sample 
of  chromium  salts  or  hydroxides,  when  the  chromium  present  exceeds  10  per  cent. 


138 


CHROMIUM 


Procedure.  Reduction.  The  sample,  containing  not  over  0.17  gram  chromium 
present  as  a  chromate,  is  boiled  to  expel  oxidizing  reagents  according  to  the 
method  described  under  the  potassium  iodide  procedure  for  chromium.  The  solu- 
tion is  made  acid,  if  not  already  so,  and  about  5  cc.  cone.  H2S04  per  100  cc. 
of  solution,  added  in  excess.  Tenth  normal  ferrous  ammonium  sulphate  solu- 
tion containing  free  sulphuric  acid  is  added  until  the  solution  changes  from 
yellow  through  olive  green  to  deep  grass  green.  For  every  0.1  gram  of  chro- 
mium about  65  to  70  cc.  of  N/10  ferrous  salt  solution  should  be  added.  After 
five  minutes,  the  excess  of  this  reducing  reagent  is  titrated  either  with  perman- 
ganate or  with  dichromate  as  directed  below. 

Potassium  Permanganate  Titration.  To  be  used  in  presence  of  free  sulphuric 
acid,  free  hydrochloric  acid  being  absent. 

Tenth-normal  potassium  permanganate  solution  is  run  into  the  reduced 
chromate  until  the  green  color  gives  place  to  a  violet  tinge.  At  the  end-point 
the  solution  appears  to  darken  slightly.  A  little  practice  enables  one  to  get  this 
with  accuracy.  A  slight  excess  of  permanganate  gives  the  solution  a  pinkish 
color,  readily  distinguishable  in  the  green.  Addition  of  3  to  4  cc.  syrupy  phos- 
phoric acid  gives  a  sharper  end-point.  The  color  should  hold  one  minute. 

Potassium  Dichromate  Titration.  N/10  K2Cr2071  is  run  into  the  solution 
until  a  drop  of  the  sample  placed  on  a  white  glazed  surface  with  a  drop  of  potas- 
sium ferricyanide  reagent  no  longer  gives  a  blue  color. 

Calculation.    From  the  total  ferrous  ammonium   sulphate  added,  subtract 
the  cc.  of  back  titration  (the  reagents  being  exactly  N/10),  the  difference  gives 
the  cc.  of  ferrous  salt  required  for  chromium  reduction.     If  reagents  are  not 
N/10,  multiply  cc.  titrations  by  factor  converting  to  N/10. 
Cc.  ferrous  ammonium  sulphate X 0.00 1733  =Cr. 

Cr203+30  =Cr206.    /.  Cr  =  1  JO  or  =3H;  hence  J  mol.  wt.  Cr  per  liter  =N  sol. 


Determination  of  Small  Amounts  of  Chromium2 

Advantage  may  be  taken  of  the  color  produced  by  chromates  in  solution 
in  determining  small  amounts,  the  depth  of  color  depending  upon  the  amount 
of  chromate  in  solution.  The  method  possesses  the  usual  disadvantage  of  color- 
imetric  procedures  in  that  there  is  always  room  for  doubt  as  to  whether  the 
element  sought  is  entirely  responsible  for  .the  color  of  the  solution. 

Procedure.  The  solution  containing  the  sample  is  nearly  neutralized  with 
sodium  carbonate,  the  reagent  being  added  until  a  slight  cloudiness  results. 
The  solution  is  now  cleared  with  a  few  drops  of  sulphuric  acid,  and  then  suf- 
ficient excess  of  a  strong  solution  of  sodium  thiosulphate  added  to  precipitate 
aluminum,  chromium,  manganese,  etc.  The  precipitate  is  filtered  off,  dis- 
solved in  the  least  amount  of  dilute  nitric  acid,  then  filtered  from  the  precipitated 
sulphur  and  diluted  to  300  to  400  cc.  Chromium  is  now  oxidized  by  adding 
10  cc.  of  0.2%  silver  nitrate  solution,  about  10  grams  each  of  ammonium  nitrate 
and  persulphate.  After  boiling  for  about  twenty  minutes,  sufficient  hydro- 
chloric acid  is  added  to  decompose  any  permanganate  present  and  to  precip- 

1  If  desired,  a  larger  sample  may  be  taken  and  N/5  or  N  solutions  used  in  titra- 
tion.    It  is  advisable  to  titrate  chromium  salts,  e.g.,  over  1.0%  Cr,  with  normal  solu- 
tions, so  that  one  pram  sample  may  be  taken  for  analysis. 

2  M.  Dittrich,  Zeitsch.  anorg.  Chem.,  80,  171-174,  1913. 


CHROMIUM  139 

itate  the  silver,  and  a  few  cc.  added  in  excess.  The  solution  is  again  boiled 
for  about  ten  minutes  and  then  filtered.  The  nitrate  is  treated  with  a  little 
sodium  phosphate  to  repress  the  color  of  traces  of  iron  that  may  be  present 
and  ma4e  to  a  definite  volume. 

The  solution  may  now  be  compared  with  a  standard  solution  containing 
the  same  amounts  of  acids,  manganese,  alumina,  etc.,  as  are  present  in  the 
sample,  tenth  normal  potassium  dichromate  being  run  into  this  standard  solu- 
tion until  its  color  matches  that  of  the  sample.  The  burette  reading  is  taken 
and  the  chromium  calculated. 

One  cc.  of  N/10  K2Cr207  =0.00173  gram  Cr. 

NOTES.  Prolonged  boiling  after  addition  of  hydrochloric  acid  to  the  solution  of 
the  chromate  will  cause  its  reduction.  A  green  tint  usually  indicates  that  the  chro- 
mate  has  been  reduced. 

The  test  may  be  carried  on  in  the  presence  of  sulphuric,  hydrochloric,  phosphoric 
hydrofluoric,  and  nitric  acids.  Alumina,  manganese,  and  small  amounts  of  iron 
do  not  interfere. 

Organic  matter  should  be  destroyed  by  either  calcining  the  sample  or  by  oxida- 
tion by  taking  to  fumes  with  sulphuric  acid.  The  presence  of  this  prevents  pre- 
cipitation of  chromium. 


COBALT 

W.    L.    SAVELL1 

Co,  at. ict.  58.97;  sp.gr.  8.7918;  m.p.  1478°;   b.p.  unknown;  Oxides,  Co3O4, 

Co2O3,  CoO,  CoO2. 

DETECTION 

After  the  removal  of  the  elements  precipitated  by  hydrogen  sulphide  from 
acid  solution,  a  little  nitric  acid  is  added  to  the  solution  to  oxidize  to  the  ferric 
state  any  ferrous  salts  which  may  be  present,  and  ammonia  is  added  until  its 
odor  is  distinctly  perceptible,  to  precipitate  iron,  aluminum  and  chromium.2 
This  precipitate  is  removed  by  nitration  and  hydrogen  sulphide  passed  through 
the  ammoniacal  solution  to  precipitate  cobalt,  nickel,  manganese  and  zinc.  After 
collecting  this  precipitate  it  is  washed  thoroughly  with  cold  hydrochloric  acid  of 
approximately  1.035  specific  gravity,  to  remove  manganese  and  zinc.  A  small 
quantity  of  the  residue  is  fused  with  borax  in  the  loop  of  a  platinum  wire.  A 
blue  color  in  the  cold  bead  indicates  cobalt.  This  test  is  masked  in  the  presence 
of  large  quantities  of  nickel.  In  this  case  the  residue  is  dissolved  in  hydrochloric 
acid  to  which  a  few  drops  of  nitric  acid  have  been  added  and  the  solution  evap- 
orated to  dryness.  The  residue  is  redissolved  in  water,  acidified  with  hydrochloric 
acid  and  the  cobalt  precipitated  with  a  hot  solution  of  nitroso-beta-naphthol 
in  50%  acetic  acid.  A  brick  red  precipitate  indicates  cobalt. 

Potassium  sulphocyanate,  KCNS,  produces  a  red  color  with  cobalt.  Alcohol 
and  ether  are  added  to  this  solution  and  shaken.  •  The  ether  layer  is  colored 
blue  by  cobalt.  If  iron  is  present  a  solution  of  sodium  thio-sulphate,  Na2S203, 
is  added  until  the  red  color  disappears,  the  solution  filtered  and  then  treated  with 
the  alcohol-ether  mixture. 

Potassium  Nitrite,  KN02,  added  to  a  neutral  or  slightly  acid  solution  con- 
taining acetic  acid,  will  precipitate  cobalt  as  a  yellow  complex  nitrite  having 
the  formula  K3Co(N02)6. 

A  solution  of  dicyandiamidine  sulphate  and  sodium  hydroxide  added  to  a 
cobalt  solution  to  which  ammonia  has  been  added  until  the  odor  is  distinctly 
discernible,  and  containing  from  10  to  20  cc.  of  10%  sugar  solution,  will  change 
the  color  of  the  solution  to  red  or  reddish  violet.  If  large  quantities  of  nickel 
are  present  the  color  will  be  yellow  or  reddish  yellow,  after  which  the  nickel  will 
separate  out  in  brilliant  crystals,  leaving  the  cobalt  in  solution,  coloring  it  as 
described  above. 

A  concentrated  solution  of  ammonium  sulphocyanate  added  to  a  cobaltous 
solution  colors  it  blue.  On  dilution  this  becomes  pink.  Amyl  alcohol  or  a  mix- 
ture of  amyl  alcohol  and  ether  1:1,  added  to  this  and  shaken,  extracts  this 
blue  compound.  Iron  sulphocyanate,  Fe(CNS)3,  likewise  colors  the  ether- 

1  Research  Chemist,  Doloro  Mining  and  Reduction  Company,  Doloro,  Ontario. 
8  If  a  relatively  large  amount  of  iron  is  present  the  basic  acetate  method  of  separa- 
tion is  necessary,  as  iron  occludes  cobalt. 

140 


COBALT  141 

alcohol  extract  red,  which  may  mask  the  cobalt  blue.  By  addition  of  sodium 
carbonate  solution  ferric  hydroxide  precipitates,  while  the  cobalt  color  will  remain 
after  this  treatment. 

ESTIMATION 

Cobalt  is  usually  estimated  as  metal;  either  reduced  by  hydrogen  from  the 
ignited  oxide  or  reduced  by  electrolysis  from  an  ammoniacal  solution  of  its 
salts.  Sometimes,  however,  it  is  estimated  as  oxide;  usually  as  Co304.  The 
reduction  of  the  oxide  by  hydrogen  may  be  carried  out  in  conjunction  with  any 
process  giving  an  oxide,  hydroxide,  carbonate,  nitrate,  chloride  or  an  organic 
compound,  as  a  final  product. 

The  reduction  of  the  metal,  in  solution,  by  electrolysis,  must  be  accomplished 
in  a  strongly  ammoniacal  solution  free  from  copper  and  nickel,  as  these  metals 
are  deposited  with  the  cobalt  on  the  cathode.  When  desirable  the  copper  and 
nickel  may  be  estimated  after  the  electrolysis  by  dissolving  the  deposit  from  the 
cathode  and  proceeding  in  the  usual  manner. 

Preparation  and  Solution  of  the  Sample 

General  Procedure  for  Ores.  The  ores  containing  cobalt  vary  so  widely 
in  their  chemical  nature  that  it  is  difficult  to  lay  down  a  method  for  treating  all 
ores.  However,  as  the  principal  ores  contain  the  cobalt  as  a  sulphide  or  arsenide 
the  same  general  methods  may  be  used  in  the  majority  of  cases.  In  all  cases  it 
is  necessary  to  prepare  the  sample  for  treatment  by  grinding  finely.  Usually 
either  of  the  above  ores  may  be  brought  into  solution  by  heating  with  strong 
nitric  acid  or  a  mixture  of  nitric  and  hydrochloric  acids,  except  silver-bearing 
ores,  which  may  usually  be  dissolved  in  a  mixture  of  nitric  and  sulphuric  acids. 

While  it  is  desirable  to  use  no  more  acid  than  is  necessary  to  bring  the  sam- 
ple into  solution,  an  excess  will  not  interfere,  as  it  may  be  driven  off  by  evapora- 
tion and  in  the  event  of  determining  the  cobalt  electrolytically  it  is  essential 
that  the  solution  be  free  from  nitric  acid,  so  that  this  evaporation  becomes 
part  of  the  procedure. 

In  the  case  of  especially  refractory  ores  or  oxides  of  cobalt  or  nickel,  a  fusion 
with  potassium  bisulphate  will  usually  be  found  sufficient  as  a  preliminary  treat- 
ment to  enable  it  to  be  brought  into  solution.  Under  certain  conditions,  how- 
ever, it  has  been  found  necessary  to  fuse  the  ore  with  sodium  peroxide  in  a  silver 
crucible,  dissolving  the  cobalt  oxide  formed  in  hydrochloric  acid.  In  some- 
what less  refractory  ores  of  a  silicious  nature  a  preliminary  fusion  with  a  mixture 
of  sodium  carbonate  and  potassium  carbonate  with  subsequent  solution  in 
hydrochloric  acid  or  sulphuric  acid,  if  the  ore  is  a  silver-bearing  one,  will  be 
found  satisfactory. 

Cobalt  Oxides.  Cobalt  oxide,  gray  or  black,  may  be  fused  with  potassium 
bisulphate,  and  the  melt  leached  with  water;  or  they  may  be  treated  with  sul- 
phuric acid,  in  which  they  dissolve  slowly;  or  with  hydrochloric  acid,  in  which 
they  dissolve  more  rapidly. 

Metallic  Cobalt,  Nickel  and  Cobalt  Alloys.  Metallic  cobalt  dissolves 
readily  in  nitric  acid,  as  do  nickel  and  the  ordinary  cobalt  alloys.  There  are 
some  alloys  of  cobalt,  however,  which  require  fusion  with  sodium  peroxide  be- 
fore they  become  amenable  to  further  treatment.  Among  these  are  certain 
cobalt-chromium  alloys. 


142  COBALT 


SEPARATIONS 

Separation  of  the  Ammonium  Sulphide  Group  Containing  Cobalt  from  the 
Hydrogen  Sulphide  Group — Mercury,  Lead,  Bismuth,  Copper,  Cadmium 
Arsenic,  Antimony,  Tin,  Gold,  Molybdenum,  etc. 

Hydrogen  sulphide  passed  into  a  hydrochloric  acid  solution  containing 
from  5  to  7  cc.  of  concentrated  hydrochloric  acid  per  100  cc.  of  solution,  pre- 
cipitates only  the  members  of  that  group  and  silver,  whereas  the  members  of  the 
subsequent  groups  remain  in  solution.  If  the  solution  is  too  acid,  lead  and 
cadmium  are  not  completely  precipitated. 

Separation  of  the  Ammonium  Sulphide  Group  from  the  Alkaline  Earths 
and  Alkalies.  Ammonium  sulphide,  free  from  carbonate,  added  to  a  neutral 
solution  containing  the  above  elements  in  the  presence  of  ammonium  chloride, 
precipitates  only  the  members  of  this  group;  the  alkaline  earths  metals,  mag- 
nesium and  the  alkalies  remain  in  solution.  A  second  precipitation  should  be 
made  if  large  quantities  of  the  alkaline  earths  or  alkalies  are  present. 

Separation  of  Cobalt  and  Nickel  from  Manganese.  The  solution  of  the 
chlorides  or  sulphates  of  cobalt  or  nickel  is  treated  with  an  excess  of  sodium 
carbonate  and  then  made  strongly  acid  with  acetic  acid.  About  5  grams  of 
sodium  acetate  for  each  gram  of  cobalt  or  nickel  present  is  now  added,  the  solution 
diluted  to  200  cc.  and  heated  to  about  80°  C.  and  saturated  with  hydrogen  sul- 
phide. Cobalt  and  nickel  are  precipitated  as  sulphides  and  the  manganese 
remains  in  solution.  The  filtrate  is  concentrated,  and  colorless  ammonium 
sulphide  added  when  the  cobalt  and  nickel  that  may  have  passed  in  solution 
from  the  hydrogen  sulphide  treatment,  will  be  precipitated.  The  treatment 
should  be  repeated  with  the  second  filtrate  to  ensure  complete  precipitation  of 
the  cobalt  and  nickel. 

Separation  of  Cobalt  from  Nickel.  Among  a  number  of  methods  for  effect- 
ing this  separation  the  following  give  good  results: 

A.  Nickel  is  removed  from  the  solution  by  precipitation  with  dimethyl- 
glyoxime.    The  details  of  the  procedure  may  be  found  in  the  gravimetric  methods 
for  the  determination  of  nickel.     Cobalt  remains  in  solution. 

B.  Cobalt  is  precipitated  by  nitroso-beta-naphthol,  leavffg  nickel  in  solu- 
tion.   Details  of  the  procedure  are  given  under  gravimetric  methods  for  deter- 
mination of  cobalt. 

C.  Cobalt  is  precipitated  as  potassium  cobalti-nitrite,  nickel  remaining  in 
solution.    Details  of  the  procedure  are  given  under  gravimetric  methods  for 
the  determination  of  cobalt. 

Separation  of  Cobalt  from  Zinc.  Zinc  is  precipitated  from  weak  acetic  or 
formic  acid  solution  by  hydrogen  sulphide  as  zinc  sulphide.  Cobalt,  nickel 
and  manganese  remain  in  solution.  The  details  of  the  procedure  are  given  under 
the  methods  of  determination  of  zinc. 


COBALT  143 

GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 

OF  COBALT 

,      Precipitation  of  Cobalt  by  Potassium  Nitrite 

Cobalt  may  be  precipitated  from  a  solution  made  slightly  acid  with  an  excess  of 
acetic  acid  by  adding  a  hot  solution  of  potassium  nitrite.  The  cobalt  is  precipitated 
as  potassium  cobalti-nitrite,  K»Co(NO»)t,  very  completely,  after  standing  for  a 
period  of  six  hours  in  a  warm  place.  This  method  has  the  advantage  of  making 
possible  the  separation  of  cobalt  from  nickel  and  iron,  although  it  has  the  one 
disadvantage,  for  commercial  purposes,  of  requiring  a  long  time  to  complete  the 
determination. 

Procedure.  After  bringing  the  material  into  solution  and  separating  the 
silica  and  members  of  the  first  and  second  groups  in  the  usual  manner,  the 
solution  is  boiled  to  eliminate  hydrogen  sulphide.  Oxidize  the  iron  present 
with  a  little  hydrogen  peroxide  and  evaporate  the  solution  to  a  syrup.  Take 
up  in  a  little  water  and  neutralize  with  a  practically  saturated  solution  of  sodium 
carbonate.  Render  slightly  acid  with  acetic  acid  and  add  an  excess  of  1  :  1 
acetic  acid.  Heat  to  almost  boiling  and  add  solution  of  50%  potassium  nitrite 
containing  100  cc.  of  glacial  acetic  acid  per  liter,  also  heated  to  nearly  boiling. 
This  solution  should  be  added  slowly  to  the  solution  of  the  sample  which  should 
be  agitated,  preferably  by  rotating  gently  while  the  addition  is  being  made. 
The  sides  of  the  beaker  should  be  washed  down  with  a  1%  solution  of  potassium 
nitrite  containing  1  cc.  of  glacial  acetic  acid  per  liter.  Allow  to  stand  for  at 
least  six  hours  and  if  possible  overnight.  Filter  through  thick  Swedish  filter 
paper  without  previous  wetting.  As  this  precipitate  shows  a  very  decided 
tendency  to  creep,  considerable  care  is  required  to  keep  it  well  down  in  the  apex 
of  the  filter-paper  cone.  Wash  about  ten  times  with  the  warm  nitrite  solution 
mentioned  above.  Transfer  to  a  beaker  by  removing  the  filter  paper  from  the 
funnel  and  opening  it  into  the  beaker  with  the  outside  of  the  paper  against  the 
glass.  This  leaves  it  in  a  convenient  position  for  washing.  The  bulk  of  the 
precipitate  is  washed  off  with  10  cc.  of  1  :  1  sulphuric  acid,  heated  to  about  80°  C. 
This  should  leave  only  a  slight  film  of  precipitate  on  the  paper.  Keep  the  solution 
in  the  beaker  at  about  80°  C.  to  assist  in  dissolving  the  precipitate  and  wash 
the  paper  with  the  hot  sulphuric  acid  solution  five  times,  using  about  10  cc.  each 
time.  Gradually  withdraw  the  filter  paper  from  the  top  of  the  beaker  during  the 
washing  operation.  Give  the  paper  a  final  wash  with  hot  water  and  squeeze  the 
last  drops  from  it  into  the  beaker.  Evaporate  and  allow  to  fume  strongly  for 
ten  minutes.  Set  the  beaker  in  a  cooling  trough  and  add  water  until  the  volume 
is  about  doubled.  Neutralize  and  make  slightly  ammoniacal  and  then  add 
an  excess  of  50  cc.  of  strong  ammonia  and  electrolyze  as  described  under  Elec- 
trolysis in  Reduction  of  Cobalt  by  Electrolysis,  page  144. 

Precipitation   of   Cobalt  by   Nitroso=beta=NaphthoI l 

Nitrosobeta-naphthol,  Ci0H6(NOH),  added  to  a  hydrochloric  acid  solution  of 
cobalt,  precipitates  cobalti-nitroso-beta-naphthol,  Co(Ci0H60(NO))3;  nickel,  if 
present,  remains,  in  solution.  The  method  is  especially  suitable  for  the  deter- 
mination of  small  amounts  of  cobalt  in  the  presence  of  comparatively  large 

i  Burgess,  Z.  Angew.,  1896,  596. 


144  COBALT 

amounts  of  nickel.  The  cobalt  precipitate  is  voluminous,  so  that  the  sample 
taken  for  the  determination  should  not  contain  over  0.1  gram  of  cobalt.  The 
reagent  will  also  precipitate  copper  and  iron  completely  from  solution,  and 
silver,  bismuth,  chromium  and  tin  partially;  but  mercury,  lead,  cadmium,  arsenic, 
antimony,  aluminum,  manganese,  nickel,  glucinum,  calcium  and  magnesium 
remain  in  solution. 

Procedure.  To  the  solution  containing  the  cobalt  is  added  a  freshly  prepared 
hot  solution  of  nitroso-beta-naphthol,  in  50%  acetic  acid,  as  long  as  a  precipi- 
tate is  produced.  After  allowing  it  to  settle,  more  of  the  reagent  is  added  to 
insure  complete  precipitation  of  the  cobalt.  The  compound  is  allowed  to 
settle  for  two  of  three  hours,  the  clear  solution  decanted  through  a  filter  and  the 
precipitate  washed  by  decantation  with  cold  water,  then  with  warm  12%  hydro- 
chloric acid  solution  to  remove  the  nickel,  and  finally  with  hot  water  until  free  of 
acid. 

The  brick-red  precipitate  is  dried,  then  ignited  in  a  weighed  platinum  cru- 
cible (Rose  crucible),  first  over  a  low  flame  and  finally  at  a  white  heat,  the 
crucible  being  covered  by  a  platinum  cover  (Rose  crucible  type)  with  a  platinum 
tube,  through  which  is  passed  a  slow  current  of  oxygen.  The  residue  is  weighed 
as  Co304.  The  oxide  may  be  reduced  in  a  current  of  hydrogen  and  weighed  as 
metallic  cobalt.  Ignited  in  the  presence  of  C02  the  oxide  CoO  is  formed. 

Precipitation  of  Cobalt  by  Electrolysis1 

Metallic  cobalt  is  readily  deposited  from  an  ammoniacal  solution  of  the 
sulphate,  but  in  the  presence  of  copper  and  nickel  these  are  also  completely  pre- 
cipitated on  the  cathode;  so,  in  case  it  is  desired  to  determine  the  cobalt  alone 
it  is  necessary  to  separate  these  metals  from  the  solution  before  electrolysis  or  to 
determine  them  separately  after  electrolysis  in  a  solution  of  the  metallic  deposit. 
In  practice  the  copper  is  usually  separated  before  electrolysis  and  the  nickel,  if 
determined  separately,  is  estimated  afterward  by  one  of  the  methods  given  under 
Nickel,  the  cathode  deposit  being  dissolved  for  this  purpose. 

Procedure.  After  preparation  and  solution  of  the  sample  the  usual  sepa- 
rations with  hydrogen  sulphide  in  acid  solution  are  made  if  necessary.  In 
most  cases  it  is  necessary  to  pass  hydrogen  sulphide  through  the  warmed  solu- 
tion for  at  least  one  hour  to  insure  the  complete  precipitation  of  arsenic.  Filter 
and  boil  to  expel  hydrogen  sulphide.  Add  5  cc.  hydrogen  peroxide  to  insure 
oxidation  of  iron  compounds  to  ferric  state  and  add  ammonium  hydroxide  until 
slightly  alkaline  to  litmus.  Filter  off  ferric  hydroxide  and  wash  with  water 
containing  a  small  quantity  of  ammonium  hydroxide.  Redissolve  and  repre- 
cipitate  this  ferric  hydroxide  in  the  above  manner,  using  a  little  hydrogen  per- 
oxide in  each  instance,  until  the  last  traces  of  cobalt  have  been  removed  from  it, 
keeping  the  filtrates,  which  should  be  as  small  as  possible,  to  add  to  the  main 
filtrate.  If  much  iron  is  present  this  is  best  removed  as  the  basic  acetate. 

Electrolysis.  If  the  treatment  of  the  iron  precipitate  has  made  a  large 
volume  of  solution  this  may  be  reduced  by  evaporation,  after  which  50  cc.  of 
strong  ammonia  are  added  and  the  solution  electrolyzed,  using  direct  current  of 
2  volts  and  0.5  ampere  per  square  decimeter.  The  electrodes  should  be 
platinum,  the  anode  a  spiral  wire  and  the  cathode  either  a  hollow  cylinder  or  a 
•ylindrical  gauze.  By  agitating  the  solution,  raising  the  voltage  and  the  cur- 
1  Low,  "  Technical  Methods  of  Analysis." 


COBALT  145 

rent  density,  the  rate  of  deposition  may  be  increased.  In  a  properly  agitated 
solution  the  deposition  may  be  completed  in  forty-five  minutes. 

The  current  should  not  be  cut  off  until  the  solution  is  tested  to  determine 
if  the  electrolysis  is  complete.  This  is  done  by  mixing  a  drop  or  two  of  the 
solution  from  the  end  of  a  stirring  rod  with  a  few  drops  of  ammonium  sulphide. 
If  the  electrolysis  is  complete  the  mixture  will  remain  colorless,  but  if  some 
cobalt  still  remains  in  the  solution  the  mixture  will  be  darkened.  After  the 
electrolysis  is  complete  the  cathode  is  carefully  removed  from  the  solution  and 
dipped  into  a  beaker  of  clean  water,  after  which  it  is  washed  with  alcohol,  pref- 
erably ethyl  alcohol. 

If  a  large  number  of  electrolytic  determinations  are  to  be  made,  it  is  con- 
venient to  have  a  wide-mouthed  bottle  with  a  well-ground-in  glass  stopper  or  a 
cork  stopper  for  holding  the  alcohol  for  the  preliminary  washing.  The  mouth 
should  be  large  enough  to  receive  the  cathode  without  pouring  out  the  alcohol. 
The  cathode  may  be  lowered  into  the  alcohol  in  this  bottle,  which  should  only 
be  partly  filled,  and  then  rinsed  again  by  pouring  fresh  alcohol  over  it  and  allow- 
ing it  to  drain  into  the  wide-mouth  bottle.  This  allows  a  great  many  cathodes 
to  be  washed  with  a  comparatively  small  quantity  of  alcohol.  Directly  after  the 
final  washing  with  alcohol  the  cathode  is  passed  through  the  flame  of  a  Bunsen 
burner  and  the  alcohol  ignited.  After  this  is  entirely  burned  off  the  cathode 
is  placed  in  a  desiccator  to  cool  and  when  cool  is  weighed.  The  increase  in  weight 
of  the  cathode  is  the  weight  of  cobalt  in  the  sample  if  the  solution  had  been  free 
from  nickel  before  electrolysis.  If  the  nickel  remained  in  the  solution  the  increase 
in  weight  of  the  cathode  represents  the  cobalt  and  nickel  in  the  sample.  If  it 
is  desired  to  determine  the  cobalt  and  nickel  together  the  increase  in  weight  of  the 
cathode  is  divided  by  the  weight  of  the  sample  and  multiplied  by  100  to  obtain 
the  percentage.  If  it  is  desired  to  obtain  the  percentage  of  cobalt  separately, 
the  plate  is  dissolved  from  the  cathode  in  a  few  cc.  of  nitric  acid  and  the  nickel 
determined  in  the  resulting  solution  by  precipitation  with  dimethyl-glyoxime 
as  described  in  the  chapter  on  Nickel,  after  which  the  cobalt  is  found  by 
difference. 

Cobalt  in  Cobalt  Oxide  * 

One  gram  of  finely  ground  cobalt  oxide  is  either  fused  with  10  grams  of  potas- 
sium bisulphate  or  heated  with  20%  sulphuric  acid  until  dissolved.  If  the 
fusion  method  is  used  the  melt  is  extracted  with  water  and  acidified  with  sulphuric 
acid.  Arsenic  and  copper  are  precipitated  by  passing  hydrogen  sulphide  through 
the  warmed  solution,  which  should  be  diluted  to  about  200  cc.  for  about  one 
hour.  These  are  removed  by  filtration  and  the  cobalt  determinated  by  one  of  the 
above  methods.  The  following  procedure  is  one  of  the  most  satisfactory: 

Procedure.  If  it  is  desired  to  determine  the  nickel  separately,  as  is  usually 
the  case,  this  is  first  precipitated  with  dimethylglyoxime  as  described  in  the 
chapter  on  Nickel,  after  boiling  the  solution  to  expel  hydrogen  sulphide.  It  is 
then  evaporated  to  fumes  of  sulphur  trioxide  and  taken  up  with  twice  its  volume 
of  water.  The  free  acid  is  neutralized  with  ammonium  hydroxide  and  an  excess 
of  50  cc.  of  strong  ammonium  hydroxide  added.  The  solution  is  made  up  to 
250  cc.  and  electrolyzed  as  under  Precipitation  of  Cobalt  by  Electrolysis. 

1 R.  W.  Landrum,  Proc.  Am.  Ceramic  Soc.,  12,  1910. 


146  COBALT 


Cobalt  in  Metallic  Cobalt  and  Ferro-cobalt 

Cobalt  is  usually  determined  in  metallic  cobalt  and  farro-cobalt  by  electrol- 
ysis, after  separation  of  the  elements  precipitated  by  hydrogen  sulphide  in  acid 
solution  and  elimination  of  iron,  if  present  in  large  quantities.  In  case  it  is 
desired  to  estimate  nickel  separately  it  is  precipitated  by  dimethylglyoxime  as 
described  in  the  chapter  on  Nickel,  before  electrolysis,  taking  the  solution  down 
to  sulphur  trioxide  fumes,  diluting  with  water  and  adding  ammonium  hydroxide 
in  excess  and  electrolyzing.  In  case  the  solution  is  electrolyzed  before  sepa- 
rating the  nickel  the  determination  of  this  element  may  be  made  in  the  solution 
of  the  electrolytic  deposit  dissolved  in  acid,  the  cobalt  then  found  by  difference. 

Procedure.  Dissolve  1  gram  of  well-mixed  drillings  in  the  least  possible 
quantity  of  nitric  acid  and  add  20  cc.  of  1  :  1  sulphuric  acid.  Evaporate  to 
fumes  of  sulphur  trioxide  and  allow  to  fume  strongly  for  ten  minutes.  This 
insures  the  complete  elimination  of  nitrates,  which  would  interfere  subsequently 
with  the  electrolysis.  Cool  and  dilute  carefully  with  20  cc.  of  water.  Heat 
the  solution  to  nearly  boiling  and  pass  in  hydrogen  sulphide  for  one  hour  to 
precipitate  copper  and  arsenic.  Filter  and  boil  the  solution  to  expel  the  last 
traces  of  hydrogen  sulphide.  Add  2  cc.  of  hydrogen  peroxide  to  oxidize  ferrous 
compounds  to  ferric  state,  and  add  ammonium  hydroxide  until  slightly  alkaline 
to  litmus  paper  and  heat  to  boiling.  Filter  off  the  ferric  hydroxide  and  wash 
with  water  containing  a  small  quantity  of  ammonium  hydroxide.  Redissolve 
the  precipitate  in  a  little  1  :  1  sulphuric  acid,  adding  a  little  hydrogen  peroxide 
to  keep  the  iron  in  the  ferric  state,  and  reprecipitate  in  the  same  manner  as  that 
described  above.  In  presence  of  comparatively  large  amounts  of  iron  the  basic 
acetate  separation  of  iron  is  necessary,  as  Fe(OH)3  occludes  cobalt  and  nickel. 
The  nitrates  from  these  precipitations  are  added  to  the  main  one. 

In  determining  the  cobalt  in  metallic  cobalt  it  is  not  necessary  to  filter  off  the 
iron  precipitate,  if  this  is  small,  as  it  has  been  found  by  W.  L.  Rigg,  of  Deloro, 
Ontario,  that  this  precipitate  does  rot  interfere  with  the  accuracy  of  the  deter- 
mination. The  iron  content  may  be  up  to  5%  without  interfering  seriously  with 
the  electrolysis. 

The  solution  is  made  ammoniacal  with  50  cc.  of  strong  ammonium  hydroxide 
and  electrolyzed  as  described  above. 

Cobalt  in  Metallic  Nickel 

The  cobalt  in  metallic  nickel  may  be  determined  by  precipitation  with  potas- 
sium nitrite  from  a  solution  of  the  sample  containing  an  excess  of  acetic  acid. 
The  precipitate  is  filtered  off  and  dissolved  in  hot  sulphuric  acid  solution,  after 
which  the  solution  is  evaporated  to  fumes  of  sulphur  trioxide  and  carefully 
diluted.  The  excess  of  acid  is  neutralized  and  made  strongly  ammoniacal  with 
ammonium  hydroxide.  The  solution  is  then  electrolyzed  as  previously  described. 

Procedure.  Dissolve  5  grams  of  thoroughly  mixed  drillings  in  a  minimum 
quantity  of  nitric  acid.  Evaporate  to  a  syrup.  Care  must  be  exercised  at  this 
point  to  prevent  evaporating  too  far  and  decomposing  the  nitrates.  Dissolve 
in  50  cc.  of  water.  Neutralize  with  a  practically  saturated  solution  of  sodium 
carbonate.  For  this  purpose  a  dropping  bottle  is  very  convenient.  Render 
slightly  acid  with  acetic  acid  and  add  an  excess  of  10  cc.  of  1  :  1  acetic  acid.  Heat 


COBALT  14? 

to  almost  boiling  and  add  10  cc.  of  a  50%  solution  of  potassium  nitrite  to  which 
has  been  added  10  cc.  of  glacial  acetic  acid  per  100  cc.  of  solution.  This  solu- 
tion must  also  be  nearly  boiling  and  should  be  added  while  gently  rotating  the 
nickel  solution.  Wash  down  the  sides  of  the  beaker  with  a  1%  solution  of 
potassium  nitrite  containing  1  cc.  glacial  acetic  acid  per  liter.  Allow  to  stand 
for  at  least  six  hours  and  preferably  overnight.  Filter  through  a  thick,  9-cm. 
filter  paper  without  previous  wetting.  Considerable  care  is  required  to  keep  the 
precipitate  well  down  in  the  apex  of  the  filter  paper  cone,  as  it  creeps  very  badly. 
Wash  about  ten  times  with  the  warm  nitrite  solution  mentioned  above.  Lift  gently 
from  the  funnel  and  open  the  filter  paper  into  a  beaker.  Lay  the  paper  against 
the  side  of  the  beaker  with  the  outside  against  the  glass.  This  leaves  the  paper 
adhering  to  the  side  of  the  beaker  in  a  most  convenient  position  for  washing. 
Wash  down  as  much  of  the  precipitate  as  possible  with  about  10  cc.  of  1  :  1  sul- 
phuric acid  solution,  heated  to  about  80°  C.  This  should  leave  only  a  slight 
film  of  precipitate  on  the  paper.  Keep  the  solution  at  about  80°  C.  and  wash 
the  paper  five  times  with  the  warm  sulphuric  acid  solution,  using  about  10  cc. 
each  time,  gradually  withdrawing  the  paper  from  the  top  of  the  beaker.  Give 
a  final  wash  with  hot  water  and  squeeze  the  last  drops  from  the  filter  paper  into 
the  beaker.  Evaporate  and  allow  to  fume  strongly  for  ten  minutes.  Add  water 
in  a  cooling  trough  until  the  volume  is  about  doubled.  Neutralize  with  ammo- 
nium hydroxide  and  add  an  excess  of  50  cc.  of  strong  ammonium  hydroxide  and 
electrolyze  as  described  in  Precipitation  of  Cobalt  by  Electrolysis. 

Cobalt  in  Ores  and  Enamels1 

The  determination  of  cobalt  in  ores  and  enamels  is  usually  made  by  a  slight 
variation  of  the  above  methods.  The  silica  is  separated  in  the  usual  manner 
by  taking  down  to  dryness  with  hydrochloric  acid  and  the  warmed  solution  is 
treated  with  hydrogen  sulphide  to  precipitate  sulphides  insoluble  in  acid  solution. 
Aluminum,  chromium  and  iron  are  precipitated  by  adding  ammonium  hydrox- 
ide to  the  oxidized  solution.  In  the  enamel  industry  it  has  been  the  practice 
to  follow  R.  W.  Landrum's  method,  in  which  the  cobalt,  manganese  and  nickel 
are  precipitated  together  as  sulphides  and  filtered  off.  The  manganese  is  dis- 
solved from  this  precipitate  with  cold  hydrogen  sulphide  water  acidified  with 
one-fifth  its  volume  of  hydrochloric  acid  (sp.gr.  1.11).  The  residue  of  cobalt 
sulphide  is  burned  in  a  porcelain  crucible,  dissolved  in  aqua  regia  and  evap- 
orated with  hydrochloric  acid.  The  platinum  and  copper,  if  they  are  present, 
are  thrown  down  by  passing  hydrogen  sulphide  through  the  solution.  The 
filtrate  is  made  ammoniacal  and  the  cobalt  is  precipitated  with  hydrogen  sul- 
phide. This  is  filtered  off  and  washed  with  water  containing  a  small  quan- 
tity of  ammonium  sulphide.  The  precipitate  is  either  ignited  and  weighed  as 
oxide  or  reduced  in  hydrogen  to  metallic  cobalt,  taking  care  to  cool  it  thor- 
oughly in  an  atmosphere  of  hydrogen  before  allowing  it  to  come  into  contact 
with  the  atmosphere  of  the  room,  as  finely  divided  cobalt  is  decidedly  pyrophoric 
and  oxidizes  readily,  particularly  if  reduced  at  a  low  temperature. 

Instead  of  igniting  the  sulphide  precipitate  it  may  be  dissolved  in  hot  1  :  1 
sulphuric  acid  solution  with  the  aid  of  a  little  nitric  acid  and  treated  as  described 
under  Precipitation  of  Cobalt  by  Electrolysis. 

i  R.  W.  Landrum,  Trans.  Am.  Cer.  Soc.,  12, 1910. 


148  COBALT 


Cobalt  in  Steel 

This  determination  is  a  modification  of  the  nitroso-beta-naphthol  method 
already  described,  as  worked  out  in  the  laboratory  of  the  Firth  Stirling  Steel 
Company,  McKeesport,  Pa.  The  procedure  as  described  by  Mr.  Giles,  Chief 
Chemist,  is  as  follows. 

Two  grams  of  the  sample  are  weighed  into  a  500-cc.  Erlenmeyer  flask  and 
dissolved  in  50  cc.  of  concentrated  hydrochloric  acid.  When  the  sample  is 
completely  decomposed  10  cc.  of  concentrated  nitric  acid  are  added  to  oxidize 
the  iron,  tungsten,  etc.  The  solution  is  evaporated  to  10  cc.;  50  cc.  of  water 
are  added;  the  contents  of  the  flask  are  then  transferred  to  a  500-cc.  volumetric 
flask  and  cooled  to  room  temperature.  A  fresh  solution  of  zinc  oxide  is  added 
in  slight  excess,  the  contents  of  the  flask  diluted  to  the  mark,  well  mixed,  trans- 
ferred back  to  the  original  Erlenmeyer  flask  and  allowed  to  settle.  Filter  250 
cc.  (equivalent  to  1  gram  of  the  sample)  through  a  dry  filter  paper,  transfer  it 
to  a  500-cc.  flask,  then  add  6  cc.  of  concentrated  hydrochloric  acid. 

The  solution,  which  should  now  be  between  300  and  350  cc.  in  volume,  is 
heated  to  boiling  and  10  cc.  of  freshly  prepared  solution  of  nitroso-beta-naphthol 
(1  gram  of  salt  to  10  cc.  glacial  acetic  acid)  are  added  for  each  0.025  gram  of 
cobalt  present.  Continue  to  heat  for  two  minutes,  remove  from  plate,  shake 
well,  and  set  aside  until  the  bright  red  precipitate  settles,  which  will  only  take 
a  few  minutes.  Filter  the  hot  solution  and  wash  the  flask  out  with  hot  1  :  1 
hydrochloric  acid  and  then  wash  the  flask  out  with  hot  acid  of  the  same  strength. 
Wash  the  paper  alternately  with  hot  (1:1)  hydrochloric  acid  and  hot  water 
until  it  has  been  washed  five  times  with  the  acid,  then  wash  ten  times  with  hot 
water.  The  precipitate  is  transferred  to  a  quartz  or  porcelain  crucible,  heated 
gently  to  expel  the  carbonaceous  matter,  then  at  a  high  temperature  until  ignition 
is  complete.  After  cooling  the  crucible  is  weighed  and  the  weight  of  the  residue 
(Co304)  is  multiplied  by  0.734  to  obtain  the  percentage  of  cobalt  present.  If 
desired  the  Co304  may  be  reduced  in  hydrogen  and  weighed  as  metal. 


COPPER 

WILFRED  W.  SCOTT  and  W.  G.  DERBY. 

Cu,  at.wt.  63.57;  sp.gr.  8.892O°;  m.p.  1083  (m  air  1065);  b.p.  2310; 
oxides  Cu2O  and  CuO. 

DETECTION 

Copper  is  precipitated  in  an  acid  solution  by  H2S  gas,  along  with  the  other 
members  of  the  hydrogen  sulphide  group.  The  insolubility  of  its  sulphide 
in  sodium  sulphide  is  a  means  of  separating  copper  from  arsenic,  antimony,  and 
tin.  The  sulphide  dissolves  in  nitric  acid  (separation  from  mercury)  along  with 
lead,  bismuth,  and  cadmium.  Lead  is  precipitated  as  PbS04  by  sulphuric  acid 
and  bismuth  as  the  hydroxide,  Bi(OH)3,  upon  adding  ammonium  hydroxide. 
Copper  passes  into  the  nitrate,  coloring  this  solution  blue, 
Cu(OH)2.2NH4OH.(NH4)2S04. 

Flame  Test.  Substances  containing  copper  (sulphides  oxidized  by  roasting), 
when  moistened  with  hydrochloric  acid  and  heated  on  a  platinum  wire  in  the 
flame,  give  a  blue  color  in  the  reducing  flame  and  a  green  tinge  to  the  oxidizing 
flame. 

Wet  Tests.  Nitric  acid  dissolves  the  metal  or  the  oxides  (sulphides  should 
be  roasted),  forming  a  green  or  bluish-green  solution.  Ammonium  hydroxide 
added  to  this  solution  will  precipitate  a  pale  blue  compound,  which  dissolves 
in  excess  with  the  formation  of  a  blue  solution.  (Nickel  also  gives  a  blue  color.) 

Hydrogen  sulphide,  H2S,  passed  into  an  acid  solution  containing  copper, 
precipitates  a  brownish-black  sulphide,  CuS.  (Distinction  from  nickel.) 

Copper  is  displaced  from  its  solution  by  zinc,  cadmium,  tin,  aluminum,  lead, 
bismuth,  iron,  cobalt,  nickel,  magnesium,  and  phosphorus.  From  a  potassium 
hydroxide  solution  it  is  precipitated  by  K2Sn02.  If  a  strip  of  iron  is  placed  in  a 
solution  of  copper,  neutral  or  slightly  acid,  it  will  be  coated  over  with  metallic 
copper.  (Delicacy  1  part  Cu  per  120,000  of  solution.) 

The  greenish-blue  cupric  salts  in  acid  solution  are  reduced  to  the  colorless 
cuprous  compounds  by  metallic  copper  and  by  stannous  chloride  and  by 
arsenious  acid,  grape  sugar,  sulphurous  acid  in  alkaline  solutions. 

ESTIMATION 

The  estimation  of  copper  is  required  in  the  following  substances :  In  ores l 
of  copper,  in  which  it  occurs  as  native  copper  or  combined  as  sulphide,  oxide, 
carbonate,  chloride,  and  silicate.  In  furnace  slags,  mattes,  concentrates,  blister 
copper,  bottoms.  The  determination  of  copper  is  required  in  the  analysis  of 


150 


COPPER 


alloys  containing  copper,1  brass,  bronze,  etc.  It  is  occasionally  looked  for  aa 
an  undesirable  impurity  in  food  products.  It  is  determined  in  salts  of  copper, 
in  insecticides,  germicides,  etc. 

Preparation  and  Solution  of  the  Sample 

Hydrochloric  and  sulphuric  acids  are  effective  in  dissolving  metallic  copper 
only  in  presence  of  an  oxidizing  agent;  nitric  acid  is  the  most  active  solvent.  The 
oxides  of  copper  may  be  dissolved  in  hydrochloric  or  sulphuric  acid,  but  nitric 
acid  is  commonly  used. 

Ores.  If  the  ore  consists  practically  of  a  single  mineral,  the  fineness  of  the 
sample  need  not  exceed  80  mesh.  If  the  ore  is  a  mixture  of  minerals,  lean  and 
rich  in  copper,  the  laboratory  sample  should  pass  a  120-mesh  sieve. 

Metallic  particles  or  masses  are  separated  at  some  stage  in  the  process  of 
sampling  and  made  into  a  separate  sample.  If  the  metallic  portion  is  a  small 
percentage  of  the  total  sample  and  consists  of  particles,  the  copper  value  of 
which  is  known  to  vary  by  a  few  percent,  no  attempt  is  made  to  refine  the  sample 
of  such,  but  a  large  portion,  10-100  grams,  is  taken  for  analysis  and  the  copper 
determined  in  an  aliquot  part  of  the  solution.  If  the  metallic  masses  are  a  large 
percentage  of  the  sample,  large  of  size,  or  consisting  of  particles  differing  widely 
in  copper  content,  a  weighed  amount  of  1  to  50  Ibs.  is  melted  in  a  graphite  crucible, 
with  addition  of  suitable  fluxes,  such  as  powdered  silica  or  lime,  if  necessary. 
Separate  samples  are  made  of  the  weighed  products  of  the  fusion  and  the  copper 
content  of  the  material  before  melting  calculated  from  their  analyses.  The  amount 
of  the  sample  taken  for  analysis  depends  upon  the  richness  of  the  ore;  as  a  general 
rule  0.5  to  1  gram  sample  is  taken  of  ores  containing  over  30%  copper,  2  grams 
of  10  to  30%  copper  ores  and  5  grams  of  ores  containing  less  than  10%  copper. 

Sulphide  Ores.  Copper  Pyrites,  Copper  Glance,  Iron  Pyrites,  etc.  One 
to  five  grams  of  the  finely  ground  ore  is  dissolved  in  a  flask  by  adding  10  to  20 
cc.  of  dilute  nitric  acid  (sp.gr.  1.2),  warming  gently  for  about  fifteen  minutes. 
The  solution  is  evaporated  to  small  volume  and  nitric  acid  expelled  by  either 
taking  to  dryness,  after  adding  hydrochloric  acid,  or  to  S03  fumes,  upon  the 
addition  of  5  to  10  cc.  of  dilute  sulphuric  acid,  1:1.  In  presence  of  lead  the 
latter  procedure  is  recommended. 

The  residue  is  taken  up  with  20  cc.  of  water  acidulated  with  sulphuric  acid 
(10%)  diluted  to  about  150  cc.  and  the  mixture  brought  to  boiling.  Lead  sul- 
phate, if  present,  is  filtered  off  together  with  silica,  and  copper  passes  into  the 
solution. 

Copper  may  now  be  separated  from  other  interfering  elements  by  one  of 
the  procedures  outlined  under  Separations,  then  determined  gravimetrically 
or  volumetrically. 

NOTES.  The  sulphur  that  appears  upon  adding  acid  to  the  ore,  with  proper 
precautions,  should  be  yellow.  If  it  is  dark  and  opaque,  the  solution  has  been  over- 
neated,  and  some  of  the  ore  has  been  occluded.  It  is  advisable  in  this  case  to  remove 
the  globule  of  sulphur  and  oxidize  it  separately  with  bromine  and  nitric  acid,  then 
boil  out  the  bromine  and  add  the  solution  to  the  rest  of  the  sample. 

Sulphide  ores  may  be  treated  according  to  the  procedure  recommended  for  iron 
pyrites  in  the  chapter  on  Sulphur,  the  ore  being  decomposed  with  a  mixture  of  bro- 
mine and  carbon  tetrachloride,  2  :  3,  followed  by  nitric  acid  and  then  sulphuric  acid. 

1  Alloys  of  zinc,  tin  and  zinc,  aluminum,  silver,  nickel,  manganese,  and  gold. 


COPPER  151 

Matte.  0.5  to  1  gram  of  the  fine  sample  is  dissolved  in  nitric  acid  and 
evaporated  with  sulphuric  acid  as  in  case  of  ores. 

Oxidized  Ores,  Oxides,  etc.  The  sample  is  dissolved  in  nitric  acid  and 
evaporated  with  dilute  sulphuric  acid  to  pastiness,  and  then  heated  to  S03 
fumes.  Frequently  a  direct  treatment  with  dilute  sulphuric  acid  or  with  hydro- 
chloric acid  may  be  employed. 

Treatment  of  Matte  Slag.  Only  by  quick  quenching  of  the  molten  slag  is 
decomposition  of  the  sample  by  acids  made  possible,  without  preliminary  treat- 
ment with  hydrofluoric  acid.  As  a  rule  lime  slags  are  readily  decomposed  by 
mixed  acids.  Extremely  acid,  or  iron  slags,  are  apt  to  be  refractory  and  are 
decomposed  with  most  certainty  by  treatment  with  hydrofluoric  acid  followed  by 
fusion  with  potassium  bisulphate. 

The  following  scheme  (White— Chemist  Analyst,  July,  1912)  of  attack,  which 
also  can  be  applied  to  silicious  ores,  with  skilful  manipulation  gives  very  satis- 
factory results : 

One  gram  of  the  100  mesh  fine  slag  is  placed  in  a  250  cc.  beaker  of  Jena  glass, 
moistened  with  water,  mixed  with  3  cc.  of  sulphuric  acid  (sp.gr.  1.54),  and 
then,  while  the  particles  of  the  slag  are  in  suspension  through  rotary  movement 
of  the  beaker,  15  cc.  hydrochloric  acid  are  added.  The  silica  is  gelatinized  in 

2  or  3  minutes  by  heating  the  beaker  over  a  free  flame.     One  cc.  nitric  acid  followed 
by  a  few  drops  of  hydrofluoric  acid  are  added,  and  the  heating  continued  in  a 
hood  until  the  material  is  nearly  dry,  and  then  to  strong  sulphuric  acid  fumes 
on  a  hot  plate.     When  cool,  4  cc.  of  sulphuric  acid  (sp.gr.  1.54)  are  added. 

The  remainder  of  the  procedure  depends  upon  the  method  that  is  to  be  fol- 
lowed in  the  determination  of  copper.  If  the  electrolytic  method  is  preferred, 

3  cc.  of  nitric  acid  are  added;  the  mass  heated  until  solution  is  effected,  the  liquid 
diluted  to  175  cc.  with  cold,  distilled  water,  and  copper  plated  out  in  20-35 
minutes,  using  a  rotating  anode  and  2|  amperes  current. 

If  the  iodide  method  is  to  be  followed,  without  addition  of  other  acid  than  sul- 
phuric, the  mass  is  again  heated  to  fumes.  When  cooled,  25-30  cc.  water  and 
5  cc.  hydrochloric  acid  are  added  and  the  liquid  boiled  until  clear.  After  addition 
of  40  cc.  saturated  solution  of  sodium  acetate,  4|%  solution  of  sodium  fluoride  is 
added  until  the  color  of  ferric  acetate  is  discharged,  and  then  an  excess  of  10  cc. 
When  cold,  titration  is  commenced,  using  a  thiosulphate  solution  with  a  copper 
equivalent  of  0.0005  g.  per  cc. 

The  following  quick  method  has  been  systematically  and  satisfactorily  checked 
for  a  long  period  by  a  hydrofluoric  acid-bisulphate  fusion  method,  by  which  cop- 
per, precipitated  as  a  sulphide,  is  ignited,  the  oxide  dissolved  in  nitric  acid  and 
copper  determined  by  electrolysis. 

Three  grams  of  the  100  mesh  fine  sample  are  placed  in  an  800  cc.  Jena  beaker. 
The  slag  is  spread  over  the  bottom  of  the  beaker,  and  while  in  motion  5  cc. 
of  sulphuric  acid  are  added  rapidly  to  prevent  the  slag  gathering  into  a  mass. 
After  addition  of  40  cc.  hydrochloric  acid,  the  beaker  is  heated  over  a  bare  flame 
for  about  3  minutes  until  the  silica  has  gelatinized.  To  the  hot  solution  nitric 
acid  is  added,  drop  by  drop,  until  the  liquid  becomes  dark  brown.  To  the  liquid, 
while  in  a  state  of  agitation,  1-2  cc.  hydrofluoric  acid  are  added  and  the  mix- 
ture boiled  until  the  solution  is  complete.  The  liquid  is  diluted  to  400  cc.  and 
saturated  with  hydrogen  sulphide  and  the  precipitate  filtered  and  washed  as 
usual.  The  copper  sulphide  is  ignited  in  a  silica  crucible;  the  residue,  if  washing 
of  the  precipitate  has  been  thorough,  can  be  brushed  into  a  250  cc.  beaker  dan 


152 


COPPER 


dissolved  with  a  few  cc.  of  nitric  acid.  After  boiling  gently  to  expel  nitrogen 
gases,  the  free  acid  is  neutralized  with  ammonia,  and  the  solution  then  acidified 
with  a  slight  excess  of  acetic  acid.  The  cold  solution  is  titrated  by  the  iodide 
method,  using  a  thiosulphate  solution  having  a  copper  equivalent  of  about  0.0005  g. 
per  1  cc. 

Metals.  A  casting  of  a  copper  alloy  and  even  of  refined  copper  is  not  homo- 
geneous, and  the  zones  of  segregation  of  the  constituents  of  the  alloy  (usually 
roughly  parallel  to  the  cooling  surfaces)  are  the  more  sharply  defined  as  the 
conditions  which  favor  diffusion  of  the  eutectic  prevail,  therefore,  unless  the  cast- 
ing be  quite  thin  and  quickly  cooled,  a  satisfactorily  representative  sample  of  it 
cannot  be  obtained  from  a  single  drill  hole.  A  single  casting  may  be  sampled  by 
complete  cross-sectional  cuts  by  a  suitable  saw  or  by  a  series  of  drill  holes  located 
in  such  a  manner  as  to  amount  substantially  to  one  or  more  cross-sectional  cuts. 
Steel  is  usually  present  as  a  contaminant  of  the  drill  or  saw  shavings  from  refined 
copper  and  the  tougher  alloys  and  should  be  removed  by  a  magnet.  Crude 
copper,  such  as  blister  or  black  copper,  is  sampled  by  drilling  one  hole  in  each 
piece  of  a  definite  fraction  of  the  total  pieces  of  the  average  lot.  The  position 
of  the  hole  in  successive  pieces  is  changed  to  conform  with  a  pattern  or 
"  templet "  which  will  cover  a  quarter,  or  half,  or  the  complete  top  surface  of 
the  average  piece,  the  "  templet "  is  divided  into  squares,  preferably  about  1  inch 
on  a  side,  and  in  the  centre  of  each  square  the  |-inch  hole  is  drilled.  The 
drillings  are  ground  to  pass  a  20-mesh  screen  and  the  sample  then  withdrawn  by 
means  of  a  riffle  sampler. 

Sampling  by  splashing  from  a  molten  stream  and  by  slowly  pouring  the 
metal  into  water  are  methods  frequently  practiced.  The  size  of  the  particles, 
the  degree  of  homogeneity  and  the  limit  of  accuracy  of  result  required  are  factors 
which  determine  whether  one  or  more  grams  of  the  sample  should  be  taken  for 
analysis. 

Iron  Ores  and  Iron  Ore  Briquettes.  A  5-gram  sample  of  the  finely 
divided  material  is  fused  in  a  large  platinum  dish  with  40  grams  of  pure  potas- 
sium bisulphate.  If  the  ore  is  high  in  sulphur,  it  should  be  roasted  by  heating 
to  redness  in  a  silica  or  porcelain  crucible  before  placing  in  the  platinum  dish 
and  mixing  with  the  bisulphate. 

The  cooled  fusion  is  broken  up  into  small  pieces  and  placed  in  an  800-cc. 
beaker  with  clock-glass  cover.  Three  hundred  cc.  of  hot  water  and  25  cc.  of 
strong  hydrochloric  acid  are  added  and  the  fusion  is  boiled  until  it  passes  into 
solution.  If  an  appreciable  residue  remains,  the  solution  is  filtered,  the  residue 
fused  with  additional  bisulphate,  then  dissolved  in  hot  dilute  acid  and  the 
filtrate  added  to  the  first  solution.  Silica  and  barium  sulphate  remain  in  the 
residue. 

The  solution  is  now  reduced  and  copper  precipitated  according  to  directions 
given  under  ''Separation  of  Copper  by  Precipitation  in  Metallic  Form  by  a 
more  Positive  Element,"  aluminum  powder  being  preferably  used. 

The  precipitated  copper  is  filtered  free  from  iron  and  other  commonly 
occurring  impurities,  then  dissolved  by  pouring  on  the  precipitated  metal  30 
cc.  of  hot  dilute  nitric  acid,  1:1,  followed  by  10  cc.  of  bromine  water  and  then 
10  cc.  of  hot  water.  The  filter  paper  is  removed,  ignited  and  the  ash  added  to 
the  copper  solution.  The  whole  solution  is  now  evaporated  to  small  volume 
and  determined,  preferably,  by  the  "Potassium  Iodide"  method  as  described 
under  the  volumetric  procedures. 


COPPER  153 

Steel,  Cast  Iron,  and  Alloy  Steels.  1  From  3  to  5  grams  of  steel,  depending 
upon  the  amount  of  copper  present,  are  dissolved  in  a  mixture  of  60  cc.  of 
water  and  7  cc.  of  sulphuric  acid  (sp.gr.  1.84)  in  a  250-cc.  beaker.  After  all 
action  has  ceased,  a  strip  of  sheet  aluminum,  1£  ins.  square,  bent  so  that  it  will 
stand  upright  in  the  beaker,  is  placed  in  the  solution. 

After  boiling  the  solution  for  twenty  to  twenty-five  minutes,  which  is  suf- 
ficient to  precipitate  all  of  the  copper  in  the  sample,  the  beaker  is  removed 
from  the  heat  and  the  cover  and  the  sides  washed  down  with  cold  water.  The 
liquid  is  decanted  through  an  11-cm.  filter,  the  precipitate  washed  three  times 
with  water,  then  placed  with  the  filter  in  a  100-cc.  beaker,  and  8  cc.  of  con- 
centrated nitric  acid  and  15  cc.  of  water  are  poured  over  the  aluminum  and 
the  solution  heated  to  boiling.  This  hot  solution  is  poured  over  the  precipitate 
and  filter  in  the  100-cc.  beaker,  and  boiled  until  the  paper  becomes  a  fine  pulp, 
only  a  few  minutes  being  required.  The  solution  is  filtered,  the  residue  washed 
several  times  with  hot  water  and  the  filtrate  and  washings,  not  over  200  cc., 
are  received  in  an  electrolytic  beaker,  2  cc.  of  concentrated  sulphuric  acid  added 
and  the  solution  electrolyzed,  using  a  current  of  2  amperes  with  an  E.M.F. 
of  2  volts.  With  gauze  cathodes  and  anodes  the  deposition  is  complete  in  an 
hour  and  a  half. 

SEPARATIONS 

Isolation  of  copper  in  presence  of  large  amounts  of  iron,  or  in  substances 
containing  nickel,  cobalt,  zinc,  bismuth,  cadmium,  etc.,  may  be  accomplished 
by  precipitation  of  the  element  as  cuprous  sulphocyanate  according  to  the 
following  procedure : 

Precipitation  of  Copper  as  Sulphocyanate.  Nitric  acid  having  been 
expelled  from  the  sample,  the  solution,  50-100  cc.,  is  nearly  neutralized  with 
sodium  carbonate  and  the  copper  reduced  by  addition  of  sodium  bisulphite 
or  metabisulphite  or  by  passing  in  S02  gas.  The  solution  is  gently  warmed 
and  potassium  sulphocyanate  reagent  added  (50  grams  KCNS  salt  per  liter), 
until  no  further  precipitation  takes  place.  The  sulphocyanate  solution  may  be 
prepared  by  addition  of  50  grams  of  potassium  bisulphite  or  metabisulphite 
to  the  above  reagent.  The  preliminary  reduction  of  copper  is  then  unneces- 
sary, as  reduction  takes  place  with  addition  of  the  reagent.  After  settling, 
the  precipitate  is  collected  on  a  filter  and  washed  free  of  acid,  first  washing 
with  the  precipitating  reagent,  then  with  ammonium  acetate  solution  and 
finally  with  water. 

The  precipitate  may  now  be  dissolved  in  nitric  acid  and  evaporated  to  near 
dryness  with  sulphuric  acid  and  copper  determined  by  electrolysis  or  by  potas- 
sium iodide  procedure. 

The  precipitated  cuprous  sulphocyanate  may  be  weighed  after  drying  at 
100°  C.,  the  compound  having  been  collected  in  a  weighed  Gooch  crucible.  The 
compound  multiplied  by  0.5226  gives  the  equivalent  metallic  copper. 

The  precipitate  may  be  dried  and  burned  with  sulphur  and  the  residue  weighed 
as  cuprous  sulphide,  Cu2S.  This  multiplied  by  0.7986  gives  the  equivalent  weight 
of  copper. 

Reaction.    2CuS04+2KCNS+S02+2H20  =  2CuCNS+2H2S04+K2S04. 
1 W.  B.  Price,  Jour.  Ind.  Eng.  Chem.,  Vol.  6,  No.  9,  p.  170. 


154  COPPER 

NOTE.  Cuprous  sulphocyanate  is  insoluble  in  water  and  in  dilute  hydrochloric 
acid.  With  the  exception  of  silver,  selenium  and  tellurium,  copper  is  the  only  metal 
that  is  precipitated  in  hydrochloric  acid  solution  by  potassium  sulphocyanate,  hence 
it  may  be  separated  from  other  elements  that  would  interfere  in  its  determination  by 
this  method. 

Separation  of  Copper  by  Precipitation  in  Metallic  Form  by  a  More  Posi- 
tive Element.  Metallic  aluminum  or  zinc  is  more  commonly  used  in  this 
procedure.  A  strip  of  pure  aluminum  or  zinc,  placed  in  the  neutral  or  slightly 
acid  solution,  causes  the  complete  deposition  of  copper.  The  copper  is  removed 
mechanically  from  the  displacing  metal  and  dissolved  in  nitric  acid  and  then 
estimated,  or  the  aluminum  may  be  dissolved  with  the  copper. 

A  method  of  precipitation  by  means  of  powdered  aluminum  is  recom- 
mended especially  for  separation  of  copper  from  large  amounts  of  iron,  iron 
ores  and  iron  ore  briquettes.  The  solution  of  the  bisulphate  fusion  of  the  iron 
ore  is  heated  until  bubbles  appear  over  the  bottom  of  the  containing  beaker. 
Aluminum  powder  is  now  added  in  small  portions  at  a  time,  in  sufficient  quantity 
to  reduce  the  iron,  the  solution  becoming  colorless.  The  solution  is  now  heated 
until  the  aluminum  completely  dissolves.  Metallic  copper  is  precipitated.  It 
is  advisable  to  add  25  cc.  of  water  saturated  with  H2S  gas  to  precipitate  traces 
of  copper  in  solution.  The  solution  is  filtered  while  hot  through  a  filter  (S. 
&  S.  No.  589),  and  washed  six  times,  keeping  the  residue  covered  with  water 
to  prevent  oxidation  by  air.  The  copper  is  now  dissolved  in  hot  dilute  nitric 
acid,  evaporated  to  small  volume  and  determined  by  the  procedure  preferred. 
The  potassium  iodide  method  gives  excellent  results. 

Separation  of  Copper  from  Members  of  the  Ammonium  Sulphide  and 
Subsequent  Groups  by  Precipitation  as  Copper  Sulphide  in  Acid  Solution. 
The  solution  containing  free  hydrochloric  or  sulphuric  acid  is  saturated  with  H2S 
gas,1  the  precipitated  copper  sulphide  (together  with  the  members  of  the  group), 
is  filtered  and  washed,  first  with  water  containing  H2S  and  finally  with  a  little 
pure  water.  The  residue  is  dissolved  in  nitric  acid  and  the  resulting  solution 
examined  for  copper. 

Removal  of  Silver.  This  element  is  precipitated  as  the  insoluble  chloride, 
AgCl,  by  addition  of  hydrochloric  acid,  and  may  be  removed  by  filtration,  copper 
passing  into  the  filtrate. 

Removal  of  Bismuth.  Upon  adding  ammonium  hydroxide  to  a  solution 
containing  copper  and  bismuth  the  latter  is  precipitated  as  Bi(OH)3  and  may 
be  removed  by  filtration.  Copper  passes  into  the  filtrate  as  the  double  ammo- 
nium salt.  Ammonium  carbonate  or  potassium  cyanide  may  be  used  instead 
of  ammonium  hydroxide. 

Removal  of  Lead.  Lead  is  precipitated  by  sulphuric  acid  as  PbS04  and 
may  be  removed  by  filtration,  copper  passing  into  the  filtrate. 

Removal  of  Mercury.  The  sulphide  of  mercury  remains  undissolved  when 
the  precipitated  sulphides  are  treated  with  dilute  nitric  acid,  copper  sulphide 
dissolving  readily. 

Removal  of  Arsenic,  Antimony,  and  Tin.  These  elements  may  be  re- 
moved by  dissolving  their  sulphides  with  a  mixture  of  sodium  sulphide  and 
sodium  hydroxide.  Copper  sulphide  remains  insoluble. 

1  Copper  may  be  precipitated  as  the  sulphide  by  nearly  neutralizing  the  free  aci( 
with  sodium  hydroxide,  warming  the  solution  and  adding  crystals  of  sodium  thiosi  ' 
phate.     Upon  boiling  black  sulphide  of  copper  is  precipitated   together   with   fi 
sulphur. 


COPPER 


155 


In  an  alloy  tin  and  antimony  may  be  precipitated  as  oxides  by  evaporation 
of  the  solution  of  the  alloy  with  strong  nitric  acid,  copper  remains  in  readily 
soluble  form. 

Separation  from  Cadmium.  The  sulphides  in  a  solution  of  dilute  sul- 
phuric acid,  1  :  4,  are  boiled  and  H2S  gas  passed  in  for  twenty  minutes,  the 
solution  being  kept  at  boiling  temperature.  Cadmium  sulphide  dissolves  while 
copper  sulphide  remains  unaffected.  The  solution  is  filtered  hot,  the  air  above 
the  filter  being  displaced  by  C02  to  prevent  oxidation.  Traces  of  cadmium  are 
removed  by  repeating  the  operation.  (Method  by  A.  W.  Hofmann.) 


GRAVIMETRIC   DETERMINATIONS   OF  COPPER 
Deposition  of  Metallic  Copper  by  Electrolysis 

The  electrolytic  method  of  determining  copper  is  the  most  accurate  of  the 
gravimetric  methods.  This  deposition  may  conveniently  be  made  from  acid 
solutions  containing  free  nitric  or  sulphuric  acid)  or  from  an  ammoniacal  solution. 


PIG.  27.— Terminal  Case  Showing  Battery  of  Electrodes  for  Electrolytic  Deposition 

of  Copper. 

The  end  sought  by  this  method  is  to  plate  out  all,  except  a  trace,  of  the 
copper  in  the  form  of  an  evenly  distributed,  firmly  adherent,  very  finely  crystal- 
line deposit,  which  is  free  from  a  weighable  amount  of  impurity. 


156  COPPER 

In  ores,  mattes,  alloys  (from  which  lead  has  been  removed  as  the  sulphate 
by  taking  the  solution  to  fumes  with  sulphuric  acid)  deposition  by  electrolysis, 
from  a  solution  containing  free  sulphuric  acid,  is  convenient.  On  the  other 
hand,  deposition  from  a  nitric  acid  solution  is  advantageous  under  conditions 
, where  this  reagent  has  been  used  as  a  solvent  and  evaporation  with  sulphuric  acid 
is  unnecessary.  This  is  the  case  in  the  analysis  of  certain  alloys  and  the  deter- 
mination of  copper  from  which  impurities  have  been  largely  removed.  Deposi- 
tion from  an  ammoniacal  solution  is  recommended  when  the  copper  salt  con- 
tains chlorides  and  it  is  desired  to  avoid  evaporation  with  sulphuric  acid.  A 
chloride  in  an  acid  solution  gives  rise  to  a  spongy  deposit  of  copper,  and  endangers 
a  solvent  action  on  the  anode  and  deposition  of  platinum  on  the  cathode. 

Conditions  other  than  the  presence  of  precipitable  impurities,  which  affect  the 
character  of  the  deposit  are — quantity  and  concentration  of  copper,  size  and 
shape  of  electrodes,  current  density,  uniformity  of  distribution  of  current  to  the 
cathode,  volume,  temperature  and  rate  of  circulation  of  the  electrolyte,  and 
concentration  of  oxidizing  agents  such  as  nitric  acid  and  ferric  salts.  Inas- 
much as  the  change  of  one  condition  limits  or  makes  possible  or  necessary  a  modi- 
fication of  others,  a  large  number  of  practicable  combinations  of  conditions  are 
possible.  For  discussion  of  these  conditions  reference  is  made  to  articles  by 
Blasdale  and  Cruess,  Jour.  Am.  Chem.  Soc.  Oct.  1910,  1264;  and  by  Richards 
and  Bisbee,  Jour.  Am.  Chem.  Soc.,  May,  1904,  530. 

By  the  feature  of  rate  of  deposition,  electrolytic  methods  may  be  classified 
ae  "  slow  "  or  "  rapid."  The  slow  methods,  with  12  to  24  hour  periods  of  elec- 
trolysis, are  practiced  when  extreme  accuracy  is  required,  or  when  the  distribution 
of  laboratory  labor  and  time  allowed  for  completion  of  the  assays  permit 
their  economical  employment.  The  electrolyte  is  a  solution  of  sulphate  salts  of 
the  metals  present,  ammonium  sulphate  or  nitrate,  and  a  quantity  of  free  nitric 
acid,  which  varies  with  the  amount  of  copper  and  ferric  salts  present,  and  the 
current  density  employed.  The  oxidizing  effect  of  nitric  acid  is  intensified  by  the 
presence  of  ferric  ions.1  Electrolysis  is  carried  out  at  room  temperature,  at  cur- 
rent densities  varying  from  ND/100, 0.15  to  0.5  amperes;  and  deposition  on  plain, 
corrugated,  slit  or  perforated  platinum  cylinders  from  0.75  to  2  in.  diameter 
having  50  to  200  cm.  depositing  surface.  A  perforated  cylinder  permits  freedom 
of  circulation  between  the  two  surfaces  of  the  electrode,  the  most  even  distri- 
bution of  current  density,  and  produces  the  most  uniform  coaling  of  the  foil. 
On  account  of  the  effect  on  the  character  of  the  deposit  by  oxygen  lodging 
in  regions  of  the  cathode  where  the  current  density  and  circulation  is  least,  the 
anode  should  be  of  such  a  form  that  all  the  gas  liberated  will  be  in  the  zone  of 
maximum  circulation.  To  procure  uniform  behavior  under  given  conditions  the 
size  and  shape  of  the  electrolytic  beaker  should  be  such  as  to  present  the  smallest 
practicable  volume  of  electrolyte  between  the  outer  surface  of  the  cylinder  and 
the  inside  of  the  beaker.  An  unclosed  seam  or  ri vetted  joint  in  a  negative 
electrode  will  hold  tenaciously  salts  which  require  extreme  care  to  remove.  It  is 
probable  that  such  recesses  retain  traces  of  the  electrolyte  underneath  the  coat- 
ing of  copper. 

Rapid  methods  have  a  tendency  to  procure  high  results,  resolution  and 
mechanical  loss  through  misting  having  been  prevented.  Deposition  is  hastened 
by  increasing  the  rate  of  circulation  and  the  current  density.  Circulation  is 

1  Larison,  Eng.  and  Min.  Jour.  84,  442.  Fairlie  and  Boone,  Elect  and  Met.  Ind. 
6,  58.) 


COPPER 


157 


promoted  by  the  use  of  the  gauze  cathode,1  by  rotating  either  cathode,2  or  by 
placing  the  vessel,  containing  the  solution  and  electrodes,  in  a  field  of  electro- 
magnetic force.3  Quick  deposition  of  a  quality  satisfactory  for  some  classes  of 
work  is  brought  about  by  increase  of  current  density  upon  an  electrolyte  heated 
to  50°  to  80°  C.  In  all  the  quick  methods,  the  progress  of  electrolysis  should  be 
watched,  and  the  cathode  removed  as  soon  as  completion  of  deposition  is  de- 
tected by  the  evolution  of  gas  about  its  surface.  The  completion  of  action  is 
ascertained  with  greater  certainty  by  addition  of  water  to  the  electrolyte  and 
observing  whether  the  newly  exposed  surface  of  the  cathode  remains  bright. 
When  the  electrolyte  is  hot  or  has  a  high  acid  content,  detachment  of  the  cathode 
should  be  preceded  by  removal  of  the  electrolyte  and  simultaneously  washing 
the  cathode  without  interruption  of  the  current.  A  syphon  may  be  employed, 
water  being  added  as  the  liquid  drains  from  the  beaker  until  the  acid  is  removed. 


RAPID  METHODS 
Rapid  Deposition  of  Copper— Solenoid  Method  of  Heath  4 

The  solenoid  is  made  by  winding  500  turns  of  No.  13  B  and  S  gauge  magnet 
wire  upon  a  copper  cylinder  2f  in.  in  diameter,  3i  in.  high,  -^  in.  thickness  of 
metal.  The  cylinder  is 
brazed  water  tight  at  the 
bottom  to  a  5^  in.  disc  of 
-fy  in.  soft  steel.  In  this 
disc  is  a  1-in.  hole  for  the 
insertion  of  a  rubber  plug, 
through  which  glass  tubes 
may  be  inserted  for  inlet 
and  outlet  of  air  or  water 
to  cool  the  electrolytic 
beaker.  A  steel  disc  of 
the  same  size  as  the  bot- 
tom and  with  an  opening 
to  fit  is  brazed  to  the  top 
of  the  cylinder.  The  sole- 
noid thus  made  is  suitable 
for  a  300  cc.  lipless  beaker 


Solenoid     for    Potation 
of     the    Electrolyte 

FIG.  28. 


4|  m.  high  and  2\  in. 
diameter.  The  solenoid 
coil  may  be  in  series  in  the 
electrolytic  line  or  excited 
separately. 

The  negative  electrode  is  of  gauze  40  meshes  per  linear  Inch,  with  a  depositing 
surface  of  100  cm.  and  is  slit  to  permit  quick  removal  from  the  electrolyte. 

i  Stoddard,  Jour.  Am.  Chem.  Soc.,  1909,  385.     Price  and  Humphreys,  Jour.  Soc- 
Chem.  Ind.,  1910,  307. 

3  ^^^A^°Chem:  loV  No°v.,  1907,  1592.      Heath,  Jour.  Ind.  Eng.  Chem., 
Feb.,  1911,' 74. 

4  Heath,  Jour.  Ind.  Eng.  Chem.,  Feb.,  1911,  76, 


158  COPPER 

Procedure.  Five  grams  of  the  thoroughly  cleaned  copper  sample  are  dissolved 
in  the  covered  electrolytic  beaker  on  a  steam  plate  with  40  cc.  of  stock  acid  solu- 
tion composed  of  7  parts  (1.42  sp.gr.)  nitric  acid,  10  parts  sulphuric  acid  (1.84 
sp.gr.)  and  25  parts  by  volume  of  water.  The  temperature  during  the  solution 
is  kept  just  below  the  boiling  point,  50  cc.  of  the  stock  solution  is  used  for  copper 
containing  0.03  to  0.1  per  cent  of  arsenic,  60  cc.  for  material  containing  0.11  to 
0.5  per  cent  arsenic.  The  electrolyte  is  diluted  to  120  cc.  A  current  of  4.5 
amperes  is  used  for  the  electrolysis  and  the  same  amount  employed  to  excite  the 
solenoid.  During  the  deposition  a  double  pair  of  watch  glasses  cover  tightly 
the  beaker  until  the  color  of  the  electrolyte  fades  out,  when  they  are  rinsed  and 
removed.  In  about  30  minutes  a  test  for  completion  of  deposition  is  made 
by  withdrawal  of  1  cc.  onto  a  porcelain  tile  and  treating  with  a  few  drops  of 
freshly  prepared  hydrogen  sulphide  water.  This  test  will  detect  the  presence  of 
0.000005  g.  copper  or  more  remaining  in  the  solution.  The  determination  is 
complete  in  two  and  a  half  hours. 

NOTES.  The  advantage  of  the  solenoid  over  any  mechanical  device  for  the  rota- 
tion of  electrodes  is  due  to  the  prevention  of  loss  by  spraying  from  the  anode,  as  the 
beaker  can  be  covered  with  a  double  pair  of  watch  glasses. 

Results  range  from  0.003  to  0.01  per  cent  higher  than  the  author's  slow  method  of 
assay  of  refined  copper,  and  is  due  to  platinum  from  the  anode,  which  is  corroded  by 
the  influence  of  heat,  nascent  nitrous  acid  and  high  current. 

Deposition  from  Nitric  Acid  Solution.  The  solution  should  not  contain 
over  2-3  cc.  of  free  concentrated  nitric  acid.  If  more  than  this  is  present, 
the  solution  is  evaporated  to  expel  most  of  the  acid,  the  remainder  neutralized 
with  ammonia  and  the  requisite  amount  of  nitric  acid  added.  The  solution  is 
diluted  to  100  cc.,  warmed  to  50°  or  60°  C.  and  electrolyzed  with  a  current  of  1 
ampere  and  2-2.5  volts.  Two  hours  are  sufficient  to  deposit  0.3  gram  copper.  Since 
nitric  acid  acts  vigorously  on  copper,  it  is  necessary  to  wash  out  the  acid  from  the 
beaker  before  breaking  the  current.  (See  method  for  copper  in  alloys,  page  175.) 

Deposition  from  an  Ammoniacal  Solution.  Ammonium  hydroxide  is 
added  to  the  solution  containing  copper  until  the  precipitate,  first  formed,  dis- 
solves. Twenty  to  twenty-five  cc.  of  ammonium  hydroxide  (sp.gr.  0.96)  are 
required  for  0.5  gram  copper  or  30-35  cc.  for  1  gram.  Three  to  four  grains 
of  ammonium  nitrate  are  added  and  the  solution  electrolyzed  with  a  current 
of  ND/100=2  amperes.  The  electrodes  are  washed,  without  breaking  the 
current,  until  the  ammonia  and  nitrate  are  removed. 

Lead,  bismuth,  mercury,  cadmium,  zinc  and  nickel  should  be  absent  from 
the  ammoniacal  solution.  Arsenic  is  not  deposited.  Unless  a  very  pure  platinum 
anode  is  used,  platinum  may  contaminate  the  deposit  appreciably.  Jena  or  other 
brand  of  zinc  borate  resistance  glass  should  not  be  used  for  the  electrolytic  beaker. 

SLOW  METHODS 
Electrolytic  Determination  of  Copper  in  Blister  Copper 

The  sample  should  be  no  coarser  than  20  mesh.  Because  fine  particles  are 
comparatively  poor  in  copper,  extreme  care  must  be  taken  in  drawing  the 
portion  for  analysis  to  preserve  the  ratio  of  the  coarse  to  fine.  Some  analysts, 
to  avoid  sampling  error,  sieve  the  coarse  from  the  40  or  60  mesh  fine  and  either 
make  a  separate  analysis  of  each  weighed  product,  or  weigh  into  a  single  test 
the  due  proportion  of  each.  Others  draw  a  large  portion,  by  means  of  a  riffle 


COPPER 


159 


FIG.  29— Riffle  Sampler. 


(Fig.  29)  or  similar  sampling  device  and  from  its  solution  in  a  volumetric  flask 
pipette  an  aliquot  part  equivalent  to  one  or  more  grams. 

By  the  small  portion  method  insoluble  matter  must  be  removed  by  filtration. 
When  the  sample  contains  an  insignificant  quantity  of  insoluble  matter,  the  prac- 
tice is  to  deposit  the  silver  with  the  copper  and 
make  a  correction  for  its  presence  in  accordance 
with  the  result  of  the  silver  assay  of  the  sample. 

By  the  large  portion  method,  insoluble 
matter  and  silver,  as  silver  chloride,  is  removed 
from  the  electrolyte  by  sedimentation  in  the 
volumetric  flask. 

Procedure.  Small  Portion  Method.  The 
coarse  and  fine  portions  are  quartered  down 
to  convenient  amounts  and  from  these  a  5- 
gram  composite  weighed,  which  contains  the 
coarse  and  fine  portions  in  ratio  of  their  per- 
centage weights.  The  sample  is  placed  in  a 
350-cc.  tall-form  beaker,  without  lip  and  with 
flaring  rim.  Fifty  cc.  of  chlorine-free,  stock 
acid  solution  (15  parts  nitric  and  5  parts  sul- 
phuric acids)  are  added,  the  beaker  covered 
with  a  funnel  (stem  up),  which  just  fits  in  the 
rim,  and  the  mixture  heated  gently  at  first  and 
finally  to  boiling.  When  the  sample  has 
dissolved,  5  cc.  saturated  solution  of  am- 
monium nitrate  are  added  and  the  sample  diluted  to  200  cc.  with  water. 

When  the  electrolyte  has  cooled  to  room  temperature  the  electrodes  are  intro- 
duced, the  beaker  covered  with  split  watch  glasses  and  electrolysis  started  with  a  cur- 
rent of  .05  ampere  and  continued  until  the  appearance  of  the  foil  indicates  that  the 
silver  has  deposited.  The  current  is  then  raised  to  ND/100  =  .75  ampere  and  this 
continued  for  twenty  to  twenty-two  hours,  or  until  the  appearance  of  gas  about  the 
negative  electrode  indicates  that  deposition  of  the  copper  is  practically  complete. 
For  the  unexperienced  a  simple  method  is  to  add  a  little  water  to  the  electrolyte 
without  breaking  the  current  and  after  15  minutes  to  observe  whether  any  depo- 
sition or  copper  takes  place  on  the  freshly  exposed  surface.  The  watch  glasses  and 
electrode  stems  should  be  rinsed  when  the  electrolysis  has  continued  15-16  hours. 

Procedure.  Large  Portion  Method.1  The  sample  is  quartered  by  a 
riffle  sampler  (see  Fig.  29)  to  an  amount  very  close  to  80  grams.  This  quan- 
tity is  weighed  and  transferred  by  a  paper  chute  into  a  2000  cc.  flask,  which 
has  been  calibrated  by  the  method  of  repeated  delivery  at  constant  temperature, 
of  a  50  cc.  overflow,  dividing  pipette  (see  Fig.  30).  The  liquid  employed  in  cali- 
brating is  a  copper  solution  of  the  same  composition  as  that  for  which  the 
flask  is  to  be  used.  A  cold  mixture  of  80  cc.  sulphuric  acid  (sp.gr.  1.82)  and 
200  cc.  nitric  acid  (1.42)  with  500  cc.  of  water  is  added.  A  standard  solution 
of  sodium  chloride  is  added  in  sufficient  quantity  to  precipitate  the  silver,  care 
being  taken  to  add  less  than  20%  excess.  A  bulbed  condenser  tube  is  placed 
in  the  neck  before  putting  the  flask  on  a  hot  plate. 

The  solution  is  gradually  heated  to  boiling  and  when  the  solution  is  nearly 
complete,  boiled  gently  for  one  hour.    This  generally  completely  dissolves  the 
1 W.  C.  Ferguson,  Jour.  Ind.  and  Eng.  Chem.,  May,  1910. 


160 


COPPER 


copper  present.    Residues  of  lead,  tin,  silver,  or  silica  if  present  in  appreciable 
amounts  are  separated  at  this  point  by  filtration. 

When  the  solution  in  the  flask  has  cooled  for  half  an  hour,  water  is  added 
to  a  little  above  the  2000-cc.  mark,  giving  the  flask  a  rotary  motion,  during 
the  addition,  to  mix  the  solution.  The  flask  is'  placed  in  a  large  tank,  Fig.  30, 


FIG.  30. — Constant  Temperature  Bath  and  Dividing  Pipette. 

containing  water  and  allowed  to  remain  until  it  becomes  of  the  same  temperature 
as  the  water  and  very  close  to  that  of  the  room.  The  solution  is  then  made 
exactly  to  the  mark  and  allowed  to  settle,  after  thorough  mixing,  by  placing 
the  flask  again  in  the  water  tank. 

Electrolysis.  Portions  equivalent  to  2  grams  of  sample  are  measured  out 
by  means  of  a  dividing  pipette,  with  water-jacket  through  which 
the  tank-water  flows.  The  solution  is  run  into  glasses,  hydro- 
meter-jar in  shape,  with  concave  bottoms,  height  of  glass,  6|  ins., 
diameter  2|  ins.,  Fig.  31.  Each  portion  is  treated  with  5  cc.  of 
a  saturated  solution  of  ammonium  nitrate  and  diluted  to  125  cc. 
with  water.  (NH4N03  or  (NH4)2S04  delays  deposition  of  As  and 
Sb  until  electrolyte  is  freed  from  Cu.)  The  electrolyte,  at  this 
stage,  contains  about  3.7  cc.  of  nitric  acid. 

The  copper  is  deposited  by   electrolysis,  using   a   current  of 
.33  ampere  per  100  sq.cm.,  which  is  kept  constant  until  deposi- 
tion is  complete,  about  twenty  hours.    It  is  advisable  to  begin 
FIG.  31.        the  electrolysis  in  the  evening,  5  P.M.    The  following  morning, 
the  inside  of  the  jar,  the  rods  of  the  electrodes,  and  the  split 
watch-glasses  which  cover  the  jar  are  rinsed  with  a  spray  of  water  into  the 
glass  and  the  run  continued  for  two  or  three  hours.    Each  electrode  is  quickly 


COPPER  161 

detached  from  the  binding  posts,  the  cathode  plunged  into  cold  water  then 
successively  into  three  jars  of  95%  alcohol,  shaken  free  of  adherent  drops  and 
dried  by  revolving  rapidly  over  a  Bunsen  flame  for  a  few  seconds  after  ignition 
of  the  film  pf  alcohol. 

The  weighing  of  foil  plus  the  deposit  is  made  with  as  little  delay  as  possible. 

Determination  of  the  Copper  Remaining  in  the  Electrolytes.  The  elec- 
trolyte is  concentrated  and  any  residual  copper  precipitated  as  sulphide  by 
H2S  after  first  neutralizing  the  free  acid  and  then  making  slightly  acid  with 
HC1.  The  copper  sulphide  is  dissolved  with  a  little  hot  HN03  and  made  ammo- 
niacal.  The  color  of  the  solution  is  compared  with  a  standard  solution  treated 
with  the  same  amount  of  reagents  as  the  sample,  care  being  taken  that  similar 
conditions  prevail  when  making  comparison.  The  electrolytes  seldom  contain 
over  0.01%  copper. 

Notes  and  Precautions 

Character  of  the  Deposits.  The  ideal  deposit  is  of  a  salmon-pink  color,  silky 
in  texture  and  luster,  smooth  and  tightly  adherent.  A  slightly  spongy  and  coarsely 
crystalline  deposit,  although  good  in  color  and  perfectly  adherent,  will  invariably 
give  high  results.  A  loosely  adherent  deposit  caused  by  either  too  rapid  a  deposition 
at  the  commencement  or  too  low  a  current  density  at  some  period  of  the  electrolysis, 
usually  shows  a  red  tint  and  may  give  a  high  result  on  account  of  oxidation  or  a  low 
result  because  of  detachment  of  particles.  A  darkly  shaded  deposit  indicates  the  pres- 
ence of  impurity  in  greater  or  less  extent.  If  it  is  impossible  to  complete  the  electrol- 
ysis without  this  appearance  the  electrolyte  should  be  purified.  Impurities  such  as 
arsenic,  antimony,  bismuth,  selenium  and  tellurium  may  occur  in  the  blister  copper. 

A  dark  colored,  but  perfectly  adherent  deposit  is  dissolved  very  slowly  from  the 
foil,  in  a  covered  electrolytic  jar,  by  gently  heating  for  several  hours  with  about  60-70 
cc.  of  a  solution  containing  2  cc.  sulphuric  and  5  cc.  nitric  acids.  When  the  solution 
is  complete  the  temperature  is  raised  to  expel  dissolved  gases.  Five  cc.  saturated 
ammonium  nitrate  solution  is  added  and  the  electrolyte  diluted  to  125  cc.  When 
cooled  to  room  temperature,  electrolysis  is  carried  out  under  the  same  conditions  as 
that  of  the  first  deposit  and  on  the  same  foil,  if  arsenic  or  antimony  is  the  interfering 
impurity;  on  a  fresh  foil  if  selenium  or  tellurium  has  been  the  contaminating  element. 
The  undeposited  copper  is  determined  colorimetrically  in  the  mixture  of  the  first  and 
final  electrolytes  and  added  to  the  weight  of  the  copper  deposited. 

If  the  sample  contains  a  large  percentage  of  arsenic  or  antimony,  a  portion  represent- 
ing 2  grams  is  drawn  from  a  pipette  into  a  Kjeldahl  flask,  10  cc.  of  sulphuric  acid  added, 
and  the  liquid  boiled  until  nitric  acid  has  been  expelled.  From  this  solution  cuprous 
sulphocyanate  is  precipitated  according  to  the  method  described  on  page  153.  The 
funnel  containing  the  filter  is  placed  in  a  500  cc.  flask  with  long  neck,  the  filter  is  punc- 
tured and  the  precipitate  washed  into  the  flask  with  the  least  quantity  of  water  possible, 
the  adherent  precipitate  is  dissolved  from  the  filter  with  warm  dilute  nitric  acid,  added 
cautiously  to  avoid  violent  evolution  of  gases  from  the  dissolving  precipitate  in  the 
flask.  The  washed  filter  is  incinerated  and  the  solution  of  its  ash  by  nitric  acid  reserved 
for  addition  to  the  electrolyte  after  completion  of  electrolysis.  When  solution  of  the 
precipitate  is  complete,  the  liquid  is  boiled  to  small  volume,  neutralized,  and  5  cc. 
ammonium  nitrate  solution  and  3  cc.  excess  free  nitric  acid  added.  The  liquid  is 
transfered  to  an  electrolytic  jar  and  electrolysis  carried  out  in  the  manner  already 
described. 

The  amounts  of  bismuth,  arsenic,  antimony,  selenium  or  tellurium  usually  found 
in  blister  copper  may  be  precipitated  together  with  iron  present  by  addition  of  ammonia 
to  a  pipetted  portion.  The  filtered  precipitate  is  purified  of  copper  by  solution  with 
nitric  acid  and  reprecipitation.  The  combined  filtrates  are  neutralized,  3£  cc.  of  free 
nitric  acid  added  and  the  solution  electrolyzed  under  the  conditions  already  described. 
The  nitric  acid  solution  of  the  incinerated  filter,  carrying  the  iron,  etc.,  is  added  to  the 
electrolyte  after  electrolysis  is  complete.  The  undeposited  copper  is  determined 
colorimetrically  by  one  of  the  procedures  outlined  on  pages  165,  166  or  167. 

The  deposited  copper  is  never  absolutely  pure.  The  total  impurities  seldom 
exceed  0.03%.  Ag  from  0.000  to  0.18%;  As  from  0.000  to  0.003%;  Sb  from  0.000 


162  COPPER 

to  0.004%;  Se  and  Te  from  0.001  to  0.027%;  Bi  from  0.000  to  0.0003%.  Periodical 
complete  analyses  may  be  made  and  corrections  applied  to  the  analysis  when  ex- 
ceedingly accurate  percentages  are  required. 

Too  low  a  current  density  or  excessive  oxidizing  power  of  the  electrolyte  may  pro- 
duce high  results,  due  to  the  oxidation  of  the  deposited  copper.  Too  high  a  current 
density  or  a  deficiency  of  oxidizing  power  in  the  electrolyte,  by  causing  a  deposition 
of  impurities,  will  give  high  results. 

The  electrodes  used  by  the  Nichols  Copper  Co.  are  straight  platinum  wires  for 
the  positive  ends  and  cylinders  If  in.  long,  1  in.  in  diameter  of  0.004  in.  irido- 
platinum  foil,  ll£  sq.  in.  depositing  surface,  tor  the  cathodes. 

A  uniform  current  is  essential. 

The  nitric  acid  used  should  be  free  of  iodic  acid. 

The  presence  of  oxide  of  nitrogen  gases,  or  a  chloride  in  an  acid  solution,  will  cause 
a  coarsely  crystalline  or  brittle  deposit,  under  conditions  which  in  their  absence  would 
produce  a  good  plating.  The  deposit  moreover  may  contain  platinum  from  the  anode 
if  the  electrolyte  contains  a  chloride  salt. 

Silver  may  be  removed  from  the  electrolyte  by  nitration,  upon  precipitation  as  a 
chloride,  or  it  may  be  deposited  with  the  copper  and  correction  made  for  its  presence 
from  the  result  of  a  separate  assay.  In  the  latter  case  the  copper  deposits  in  poor 
form,  unless  the  silver  be  first  plated  out  at  a  very  low  current  density. 

Solid  matter,  unless  removed,  will  contaminate  the  deposit  mechanically. 

Arsenic,  antimony,  selenium  or  tellurium  have  an  influence  on  the  physical  character 
of  the  deposit  which  may  affect  the  copper  result  beyond  the  sum  of  such  impurities 
deposited. 

In  the  process  of  preparing  an  electrolyte,  arsenic  may  be  eliminated  as  arsenious 
fluoride  in  the  decomposition  of  silicious  material  by  hydrofluoric  acid.  Selenium  is 
expelled  by  evaporation  to  dryness  of  a  hydrochloric  acid  solution  or  by  fuming  a  sul- 
phuric acid  solution.  All  impurities  may  be  removed  by  occlusion  with  ferric  hydroxide; 
several  times  their  weight  of  iron  being  added  and  the  hydroxide  then  precipitated  with 
ammonia.  In  the  handling  of  copper  solutions  account  is  to  be  taken  of  the  retention 
of  copper  in  the  ferric  hydroxide  precipitate  and  the  combination  of  copper  in  ammo- 
niacal  solution  with  cellulose. 

Whether  impurities  are  deposited  or  not,  appreciably  high  results  are  obtained  by 
continuing  electrolysis  for  some  time  after  the  electrolyte  has  become  impoverished 
of  copper. 

Overheating  of  the  copper  deposit,  in  the  process  of  ignition  of  the  alcohol  clinging 
to  the  cathode,  will  cause  oxidation  of  the  copper.  As  much  as  possible  of  the  alcohol 
must  be  shaken  off  before  passing  the  electrode  rapidly  through  the  flame.  It  is  advis- 
able to  weigh  the  copper  shortly  after  deposition,  as  prolonged  contact  with  air  is  unde- 
sirable, if  extreme  accuracy  is  desired. 

The  copper  deposits  may  be  removed  by  plunging  the  electrode,  for  a  few  moments, 
in  hot  nitric  acid.  After  washing  with  water,  the  foil  is  ignited  to  a  cherry  red  in  a 
direct  colorless  flame.  The  ignition  removes  any  grease  which  would  be  objectionable, 
that  may  contaminate  the  platinum.  Alcohol  frequently  contains  oily  matter  which 
will  cling  to  the  electrode  in  spite  of  the  rapid  ignition  for  drying  the  deposit, 


OTHER  METHODS 
Determination  as  Cuprous  Sulphocyanate 

The  procedure  has  been  outlined  under  Separations  on  page  153. 

CuCNSX0.5226=Cu. 

Determination  as  Copper  Oxide l 

The  solution,  free  from  ammonium  salts  and  organic  matter,  is  heated  to 
boiling  in  a  porcelain  dish  and  pure  potassium  hydroxide  solution  added,  drop 
»"  Analytical  Chemistry,"  Treadwell  and  Hall. 


COPPER  163 

by  drop,  until  a  permanent  precipitate,  dark  brown  in  color,  is  formed.  The 
solution  is  alkaline  to  litmus-paper.  The  precipitate  is  washed  by  decantation, 
transferred  to  the  filter  and  washed  with  hot  water  free  of  alkali.  The  precipi- 
tate and  filter  are  ignited  in  a  porcelain  dish,  first  gently  and  finally  with  the 
full  heat  of  a  Bunsen  burner.  The  residue  is  weighed  as  CuO. 

CuOX0.7989=Cu. 

VOLUMETRIC   METHODS   FOR  THE   DETERMINATION 

OF  COPPER 

Potassium  Iodide  Method 

The  procedure  depends  upon  the  fact  that  cupric  salts  when  heated  with 
potassium  iodide  liberate  iodine,  the  cuprous  iodide  formed  being  insoluble  in 
dilute  acetic  acid  is  thus  removed,  no  reversible  reaction  taking  place. 

Reactions.    2CuS04+4KI  =  2CuI+2K2S04+I2. 
The  liberated  iodine  is  titrated  with  standard  thiosulphate. 
2Na2S203+2I  =Na2S406+2NaI. 

This  method  is  exceedingly  accurate.  Very  few  metals  interfere.  Bismuth, 
selenium,  trivalent  arsenic,  antimony  or  iron  should  not  be  present.  Lead,  mer- 
cury, and  silver  increase  the  consumption  of  iodide,  but  do  not  otherwise  interfere. 

Solutions.  Sodium  Thiosulphate.  7.5  grams  of  the  salt,  Na2S203-5H20, 
are  dissolved  and  made  to  2  liters  with  water.  The  solution  is  standardized  against 
a  copper  solution  containing  1  gram  of  pure  copper  per  liter,  1  cc.  =0.001  gram 
Cu.  Approximately  the  same  amount  of  copper  is  taken  as  will  be  determined 
in  the  ores.  For  high-grade  copper  ores  and  crude  copper,  etc.,  it  is  advisable 
to  prepare  a  standard  thiosulphate  solution  ten  times  the  above  strength.  The 
copper  solution  is  made  slightly  ammoniacal  and  then  acid  with  acetic  acid. 
Potassium  or  sodium  iodide  crystals,  free  from  iodate,  are  added  and  the  liberated 
iodine  titrated  with  the  standard  thiosulphate.  (See  Procedure.) 

Weight  of  copper  taken  .   . . 

.  .       : — .  =  value  of  1  cc.  of  the  thiosulphate  solution. 

cc.  thiosulphate  required 

Standard  Copper  Solution.  One  gram  of  purest  electrolytic  copper  is  dis- 
solved in  20  cc.  of  dilute  nitric  acid,  sp.gr.  1.2,  and  the  solution  diluted  to  1000 
cc.  For  standardizing  the  thiosulphate  to  be  used  with  high-grade  copper 
ores,  crude  copper,  blister  copper,  etc.,  a  copper  solution  containing  ten  times 
the  above  amount  of  metallic  coppers  is  prepared. 

The  following  additional  reagents  are  required:  starch  solution,  solid  potas- 
sium iodide,  50%  acetic  acid  solution,  and  other  common  laboratory  reagents. 

NOTE.  Sodium  thiosulphate  is  apt  to  change  in  strength  upon  standing,  so 
that  restandardization  is  necessary. 

Procedure.  The  solution  containing  the  copper,  separated  from  inter- 
fering elements,  by  precipitation  with  aluminum  powder  or  potassium  sulpho- 
cyanate,  is  evaporated  to  about  30  cc.  and  the  free  acid  neutralized  with  sodium 
carbonate,  or  ammonia,  and  then  made  slightly  acid  with  acetic  acid,  1  : 3, 
the  solution  becoming  clear,  about  3  grams  of  potassium  iodide,  or  the  equivalent 


164  COPPER 

of  a  saturated  solution,  are  added  and  the  liberated  iodine  titrated  with  standard 
thiosulphate,  the  reagent  being  added  until  the  brown  color  changes  to  light 
yellow  and  after  the  addition  of  starch  solution  until  the  blue  color  fades  out. 
The  end-point  is  very  sharp. 

Cc.  thiosulphate  multiplied  by  value  of  reagent  gives  weight  of  copper  in 
sample. 

NOTES.  Nitrous  oxides  should  be  expelled  before  neutralizing  with  alkalies.  A 
large  excess  of  acetic  acid  should  be  avoided.  The  solution  should  be  cool  and  con- 
tain at  least  6  parts  of  KI  for  1  of  Cu,  e.g.,  1  Cu  =  5.2231  KI  =  1.9965  1  =  3.9034 
NfteSgOs  -5H2O.  The  solution  should  be  concentrated,  40  to  50  cc. 

Prof.  Gooch  recommends  a  volume  of  100  cc.,  containing  no  more  than  3  cc. 
nitric,  sulphuric,  or  hydrochloric  acids,  or  25  cc.  of  50%  acetic  acid,  with  5  grams 
potassium  iodide.  Two  to  3  grams  more  of  potassium  iodide  are  added  if  the  titra- 
tions  are  large.  "Methods  in  Chemical  Analysis." 

When  ferric  iron  is  the  only  disturbing  impurity  and  no  nitrates  are  present,  the 
necessity  of  separation  of  copper  may  be  avoided  by  fixing  the  free  mineral  acid  by 
use  of  sodium  acetate  and  then  adding  a  clear,  4^  per  cent  solution  of  sodium  fluoride 
until  the  red  color  of  ferric  acetate  has  bleached  and  then  an  excess  of  10  cc.  (Jour. 
Sci.  Chem.  Ind.,  May  15,  1915,  p.  462;  Mott,  Chemist  Analyst,  July,  1912.) 

Arsenic  or  antimony  when  present  in  trivalent  form  may  be  oxidized  by  treatment 
with  bromine,  chlorine,  hydrogen  peroxide  or  potassium  permanganate,  care  being 
taken  to  expel  or  reduce  any  excess  of  the  oxidizing  agent  before  titration. 

Potassium  Cyanide  Method 

This  procedure  is  largely  employed  on  account  of  its  simplicity,  although 
it  does  not  possess  the  degree  of  accuracy  of  the  Iodide  Method.  The  procedure 
depends  upon  the  decoloration  of  an  ammoniacal  copper  solution  by  potassium 
cyanide. 

The  operations  of  the  standardization  of  potassium  cyanide  and  of  making 
the  assay  should  be  as  near  alike  as  possible.  If  iron  is  present  in  the  assay 
it  should  be  added  to  the  standard  copper  solution  titrated,  in  order  to  become 
accustomed  to  the  end-point  in  its  presence. 

Silver,  nickel,  cobalt,  cadmium,  and  zinc  interfere  and  should  be  removed 
if  present  in  appreciable  quantities.  Precipitation  of  metallic  copper  by  alumi- 
num powder,  as  directed  under  Separations,  is  recommended  as  a  procedure 
for  iron  ores  and  briquettes.  In  presence  of  smaller  amounts  of  iron,  the  titra- 
tion may  be  made  in  presence  of  iron  suspended  in  the  solution.  It  is  not 
advisable  to  filter  off  this  precipitate,  as  it  invariably  occludes  copper.  With 
practice,  the  shade  of  color  the  iron  precipitate  assumes  at  the  end  of  the  reac- 
tion serves  as  an  indicator,  so  that  the  operator  is  assisted  rather  than  retarded 
by  its  presence. l 

2Cu(NH3)4S04-H2O+7KCN  = 

K3NH4Cu2(CN)6+NH4CNO+2K2S04+6NH3+H20. 

Standard  Potassium  Cyanide  Solution.  Thirty-five  grams  of  the  salt  are 
dissolved  in  water,  then  diluted  to  1000  cc. 

Standardization.  0.5  gram  of  pure  copper  is  dissolved  in  a  flask  by  warming 
with  10  cc.  of  dilute  nitric  acid  (sp.gr.  1.2),  the  nitrous  fumes  expelled  by  boiling, 
the  solution  neutralized,  diluted  and  titrated  as  directed  under  Procedure. 

Button,  "  Volumetric  Analysis."  Davies,  C  N.,  58,  131.  J.  J.  and  C.  Beringer, 
C.  N.,  49,  3.  Dr.  Steinbeck,  Z.  a.  C.,  8,  1;  C.  N.,  19,  181. 


COPPER  165 

If  iron  is  present  in  the  samples  titrated,  it   is   advisable   to  add   iron   to  the 
standard  copper  solution  as  directed  above. 

*        CC.KCN  Solution  =Wt"  Cu  per  cc'  of  standard  KCN' 

Procedure.  The  solution  containing  the  copper  is  neutralized  with  sodium 
carbonate  or  hydroxide,  the  reagent  being  added  until  a  slight  precipitate  forms. 
One  cc.  of  ammonium  hydroxide  is  now  added  and  the  solution  titrated  with 
standard  potassium  cyanide  solution.  The  blue  color  changes  to  a  pale  pink; 
finally  a  colorless  solution  is  obtained.  In  presence  of  iron,  when  the  copper 
is  in  excess  of  the  cyanide,  the  iron  precipitate  possesses  a  purplish-brown  color, 
but,  as  this  excess  lessens,  the  color  becomes  lighter  until  it  is  finally  an  orange 
brown,  the  solution  appearing  nearly  colorless.  The  reagent  should  be  added 
from  a  burette  drop  by  drop  as  the  end-point  is  approached. 

Cc.  KCN  X factor  per  cc.  =  weight  Cu  in  assay. 


COLORIMETRIC  DETERMINATION  OF  SMALL  AMOUNTS 

OF  COPPER 
Potassium  Ethyl  Xanthate  Method 

The  method  is  based  upon  the  fact  that  potassium  ethyl  xanthate  produces 
a  yellow-colored  compound  with  copper.  The  reagent  added  to  a  solution 
containing  traces  of  copper  will  produce  a  yellow  color  varying  in  intensity  in 
direct  proportion  to  the  amount  of  copper  present.  Larger  amounts  of  copper 
with  the  reagent  produce  a  bright  yellow  precipitate  of  copper  xanthate.  Small 
quantities  of  iron,  lead,  nickel,  cobalt,  zinc,  or  manganese  do  not  interfere.  The 
procedure  is  especially  valuable  for  determination  of  the  purity  of  salts  crys- 
tallized in  copper  pans. 

Special  Solutions.  Stock  Solution  of  Copper  Sulphate.  3.9283  grams 
CuS04-5H20  are  dissolved  in  water  and  made  up  to  a  volume  of  1000  cc.  One 
cc.  is  equivalent  to  0.001  gram  Cu. 

Standard  Copper  Sulphate.  Ten  cc.  of  the  stock  solution  are  diluted  to  1000 
cc.  with  distilled  water.  One  cc.  =0.00001  gram  Cu. 

Potassium  Ethyl  Xanthate  Solution.  One  gram  of  the  salt  is  dissolved  in 
1000  cc.  of  water.  The  solution  is  kept  in  an  amber-colored  glass-stoppered 
bottle. 

Procedure.  Five  grams  of  the  substance  are  dissolved  in  90  cc.  of  water 
(see  note)  and  the  solution  poured  into  100-cc.  Nessler  tube;  10  cc.  of  the  potas- 
sium xanthate  reagent  are  added  and  the  solution  mixed  by  means  of  a  glass 
plunger.  To  a  similar  tube  containing  50  or  60  cc.  of  water  are  added  10  cc. 
of  the  xanthate  reagent  and  then  gradually  drop  by  drop  the  standard  copper 
solution  from  a  10-cc.  burette  (graduated  in  ^  cc.)  until  the  colors  in  both 
tubes  match. 

If  a  =  grams  of  the  substance  taken  for  analysis,  6=  number  of  cc.  standard 
copper  solution  required  to  match  the  sample;  then  6X0.00001  X 100 +a  =  %  Cu. 

NOTES.     The  amount  of  the  substance  to  be  taken  varies  according  to  its  copper 
content.     The  greater  the  copper  contamination  of  the  salt,  the  less  sample  required. 
The  solution  should  be  neutral  or  only  very  slightly  acid. 


166  COPPER 

In  place  of  the  Nessler  tubes  the  special  colorimetric  apparatus  desciibed  under 
Titanium  and  under  Lead  may  be  used.  A  very  weak  copper  standard  will  be 
required  for  the  comparison  tube. 

If  the  substance  is  insoluble  in  water  the  copper  is  rendered  soluble  by  treat- 
ment with  nitric  acid.  Hydrochloric  acid  is  added  and  the  nitric  expelled  by  evapo- 
ration. The  substance  is  taken  up  with  water  and  the  insoluble  residue  filtered  off. 

Starch  and  organic  matter  are  destroyed  by  addition  of  10  cc.  10%  sodium 
hydroxide +10  cc.  of  saturated  sodium  nitrate  solution,  then  evaporating  to  dryness 
arid  igniting.  Hydrochloric  acid  is  now  added  to  expel  the  nitric  acid  as  directed 
above. 

Ferrocyanide  Method  for  Determination  of  Small  Amounts 

of  Copper 

By  this  colorimetric  method  it  is  possible  to  detect  one  part  of  copper  in 
2,500,000  parts  of  water.  The  procedure  depends  upon  the  purplish  to  chocolate- 
brown  color  produced  by  potassium  ferrocyanide  and  copper  in  dilute  solutions. 
The  procedure  is  applicable  to  the  determination  of  copper  in  water  and  may 
be  used  in  presence  of  a  number  of  elements  that  occur  in  slags.  Iron  also 
produces  a  colored  compound  with  ferrocyanide  (1  part  Fe  detected  in  13  million 
parts  H20),  so  this  element  must  be  removed  from  the  solution  before  testing 
for  copper. 

Solutions.  Standard  Copper  Solution.  0.393  gram  CuS04-5H20  per  liter. 
1  cc.  =0.0001  gramCu. 

Ammonium  Nitrate.     100  grams  of  the  salt  per  liter. 

Potassium  Ferrocyanide.     Four  grams  of  the  salt  per  100  cc.  of  solution. 

Procedure.  A  volume  of  5  to  20  drops  of  potassium  ferrocyanide,  accord- 
ing to  the  amount  of  copper  present  in  the  solution,  is  placed  in  a  tall,  clear, 
glass  cylinder  or  Nessler  tube  of  150  cc.  capacity,  5  cc.  of  ammonium  nitrate 
solution  added  and  then  the  whole  or  an  aliquot  portion  of  the  neutral x  solution 
of  the  assay.  The  mixture  is  diluted  to  150  cc.  The  same  amount  of  ferrocyanide 
and  ammonium  nitrate  solutions  are  poured  into  the  comparison  cylinder,  placed 
side  by  side  with  the  one  containing  the  sample,  on  a  white  tile  or  sheet  of  white 
paper.  The  standard  copper  solution  is  now  run  from  a  burette  into  the 
comparison  cylinder,  stirring  during  the  addition,  until  the  color  matches  that 
of  the  assay.  The  number  of  cc.  required  multiplied  by  0.0001  gives  the  weight 
of  copper  in  the  sample  contained  in  the  adjacent  cylinder. 

Amount  of  Cu  XI 00 

c^r- — 7 —  — - — =  %  Cu  in  the  sample. 

Wt.  of  sample  compared 

NOTES.  The  solution  must  be  neutral,  as  the  copper  compound  is  soluble  in  ammo- 
nium hydroxide  and  is  decomposed  by  the  fixed  alkalies.  If  the  solution  contains  free 
alkalies,  it  is  made  slightly  acid  and  then  the  acid  neutralized  with  ammonia,  added 
in  slight  excess.  This  is  boiled  to  expel  the  excess  of  ammonia,  and  then  tested  accord- 
ing to  the  directions  under  "  Procedure."  Solutions  containing  free  acids  are  neu- 
tralized with  ammonia. 

Iron  may  be  removed  by  precipitation  with  ammonia.  As  this  hydroxide  occludes 
copper,  the  precipitate  should  be  dissolved  and  reprecipitated  to  recover  the  occluded 
copper. 

Determination  of  copper  in  water  is  accomplished  by  evaporating  a  quantity 
of  water  to  dryness,  taking  up  the  residue  with  a  little  water  containing  1  cc.  nitric 
acid,  the  residue  having  been  ignited  to  destroy  organic  matter,  precipitating  iron 
with  ammonia,  as  directed  above,  and  determining  copper  in  the  filtrate. 

The  colorimeter  used  in  determination  of  traces  of  lead  and  for  the  colorimetric 
determination  of  titanium  may  be  employed  in  place  of  the  Nessler  tubes. 


COPPER  167 

Ammonia  Method  for  Determining  Small  Amounts  of  Copper 

^  In  the  absence  of  organic  matter,  nickel  and  elements  giving  a  precipitate 
with  ammonia,  copper  to  an  upper  limit  of  10  milligrams  can  be  determined  by 
comparison  of  the  depth  of  the  blue  tint  of  its  ammonium  solution  with  a  tem- 
porary or  permanent  standard  copper  solution  of  equal  volume.  Permanent 
standard  solution  of  copper  sulphate,  free  of  nitrate,  if  kept  cool  and  away  from 
the  direct  sunlight,  lasts  for  a  long  time,1 

Hydrogen  Sulphide  Method 

In  the  absence  of  elements  precipitated  by  hydrogen  sulphide,  copper  to  the 
limit  of  about  1  milligram,  in  a  solution  not  too  strongly  acid  with  sulphuric  or 
hydrochloric  acid,  may  be  determined  by  comparison  of  its  sulphide  with  that  of 
a  known  quantity  of  copper  in  equal  volume  and  similarly  treated.  The  liquid 
should  be  cold  and  the  passage  of  the  hydrogen  sulphide  stopped  before  the 
compound  coagulates. 

NOTE.  Either  the  ammonia  or  the  hydrogen  sulphide  method  is  applicable  to  the 
determination  of  the  copper  not  deposited  in  the  operation  of  the  electrolytic  method. 

DETERMINATION   OF   IMPURITIES    IN   BLISTER  AND 
REFINED   COPPER 

Introduction.  In  the  complete  analysis  of  copper  the  following  impurities 
are  generally  estimated:  silver,  gold,  lead,  bismuth,  arsenic,  antimony,  selenium, 
tellurium,  iron,  zinc,  cobalt,  nickel,  oxygen,  sulphur,  and  less  commonly,  tin 
and  phosphorus.  In  high  grades  of  blister  and  in  refined  copper  the  percentage 
of  these  impurities  is  very  low,  the  blister  copper  usually  averaging  over  99.0% 
copper  with  silver  and  the  refined  copper  over  99.93%  of  the  metal.  The  principal 
impurity  in  the  refined  element  is  oxygen,  which  may  be  present  to  the  extent 
of  .02  to  .15%,  the  remaining  impurities  being  in  the  third  decimal  place. 
From  this  it  is  readily  seen  that  large  samples  are  required  for  the  accurate 
determination  of  these  constituents.  The  amount  of  sample  taken  in  blister 
copper  depends  upon  the  grade  of  copper  analyzed.  The  impurities  in  this 
vary  from  tenths  of  a  per  cent  to  thousandths,  as  the  metal  from  one  locality 
may  contain  quite  appreciable  amounts  of  a  constituent,  which  may  be  present 
only  in  extremely  small  quantities  or  not  at  all  in  copper  from  a  different  section. 
In  usual  practice  it  is  customary  to  take  from  10  to  50  grams  of  blister  and  50 
to  500  grams  of  refined  copper  for  analysis,  depending  upon  the  purity  of  the 
material.  If  a  larger  sample  than  50  grams  is  taken,  it  is  necessary  to  divide 
the  material  into  several  lots,  and,  after  removal  of  the  bulk  of  copper  and  isola- 
tion of  the  impurities,  to  combine  the  filtrates  or  residues  containing  the  con- 
stituents sought. 

In  the  procedures  the  smallest  amount  of  sample,  10  grams,  is  taken  as 
the  basis  of  calculation  for  amounts  of  reagents  used.  For  larger  samples,  in 
the  initial  treatment  for  removal  of  copper,  proportionately  larger  amounts  of 
the  reagents  are  required,  i.e.,  multiples  of  from  2  to  5  times  the  amount  stated. 
A  50-gram  sample  is  the  largest  amount  of  material  handled  in  one  lot. 

Scrupulous  care  must  be  exercised  throughout  the  analysis  to  prevent  con- 

1  Heath,  Jour.  Am.  Chem.  Soc.,  19,  21. 


168  COPPER 

lamination  of  the  sample  or  reagents,  and  to  avoid  loss  of  constituents.  The 
reagents  used  should  be  free  from  the  substance  sought  or  from  interfering  sub- 
stances. It  is  the  practice  to  carry  blank  tests  of  the  reagents  through  under 
conditions  similar  to  a  regular  analysis  for  iron,  lead,  zinc,  arsenic  antimony  and 
sulphur. 

It  is  found  best  to  determine  the  impurities  in  several  portions,  i.e.,  gold 
and  silver  by  assay;  bismuth  and  iron  in  one  portion;  lead,  zinc,  cobalt,  and 
nickel  in  a  second;  arsenic,  antimony,  selenium,  and  tellurium  in  a  third;  and 
separate  portions  for  sulphur,  oxygen,  phosphorus  and  tin,  when  these  are 
occasionally  required. 

Determination  of  Bismuth  and  Iron 

Separation  of  Copper.  Amount  of  Sample.  Blister  copper  10  to  25  grams, 
refined  copper  100  to  500  grams.  The  drillings  are  dissolved  in  a  large  beaker 
in  40  cc.  of  nitric  acid  per  10-gram  sample  and  the  free  acid  expelled  by  boiling. 
The  solution  should  not  become  basic  during  the  evaporation.  Water  is  added 
to  make  the  volume  130  cc.  per  10  grams  or  proportionately  more  for  larger 
samples.  Ammonia  is  now  added  in  sufficient  excess  to  hold  the  copper  in 
solution  and  5  cc.  of  saturated  ammonium  carbonate  solution  and  the  sample 
diluted  to  200  cc.  (25  cc.  (NH4)2C03  per  50  grams,  and  dilution  to  1000  cc.). 
The  beaker  is  placed  on  the  steam  bath  for  several  hours,  preferably  over  night. 
The  solution  is  filtered  hot  (to  avoid  crystallization  of  the  copper  salt),  the  first 
100  cc.  being  refiltered,  and  the  residue  washed  with  hot  water  containing  a 
little  ammonia.  By  this  procedure  the  copper  passes  into  the  filtrate  and 
bismuth  and  iron  remain  in  the  residue  on  the  filter. 

Separation  of  Iron  and  Bismuth.  The  precipitate  is  dissolved  in  warm, 
dilute  hydrochloric  acid  (1  :  3),  ammonia  added  to  the  solution  in  sufficient 
amount  to  almost  neutralize  the  acid  and  the  solution  then  saturated  with  hydro- 
gen sulphide.  After  settling  some  time,  the  precipitate  containing  bismuth  sul- 
phide is  filtered  off,  iron  passing  into  the  solution. 

Determination  of  Iron.  Hydrogen  sulphide  is  expelled  by  boiling  the 
filtrate,  and  iron  oxidized  by  addition  of  hydrogen  peroxide,  or  potassium 
chlorate  (nitric  acid  should  not  be  used).  The  solution  is  evaporated  to  dry- 
ness  and  iron  then  determined  in  the  residue  by  the  stannous  chloride  method, 
details  of  which  may  be  found  in  the  chapter  on  Iron,  page  221. 

Determination  of  Bismuth.  The  sulphides  remaining  on  the  filter  are 
dissolved  in  nitric  acid,  the  solution  evaporated  with  sulphuric  acid  to  S03  fumes 
to  expel  nitric  acid,  the  concentrate  diluted  with  water,  and  lead  filtered  off.  Bis- 
muth is  precipitated  in  the  filtrate  by  addition  of  ammonia  in  slight  excess, 
followed  by  10  cc.  of  a  saturated  solution  of  ammonium  carbonate,  and  boiling. 
The  precipitate  is  settled  for  several  hours  or  over  night  if  preferred,  and  then 
separated  by  filtration.  This  is  now  dissolved  in  the  least  amount  of  nitric 
acid,  added  to  the  filter  drop  by  drop  from  a  burette  and  bismuth  determined 
in  the  solution  by  the  cinchonine  iodide  method,  given  in  detail  in  the  chapter 
on  Bismuth,  page  69. 

NOTES.  An  excess  of  nitric  acid,  or  the  presence  of  cadmium,  lead,  silver,  or 
hydrochloric  acid  interferes  with  the  colorimetric  procedure. 

In  analysis  of  refined  copper  several  50-gram  portions  are  taken  for  analysis, 
ten  such  portions  on  a  500-gram  sample;  the  filtrates,  obtained  upon  dissolving  the 
residue  freed  from  copper,  are  combined  and  bismuth  and  iron  determined  on  this 
combined  solution. 


COPPER  169 

Determination  of  Lead,  Zinc,  Nickel,  and  Cobalt 

Removal  of   Copper.    Ten  to  25  grams  of  blister  copper,  and  100  to  250 

grams  oLrefined  copper  in  25-gram  portions  are  taken  for  analysis.  The  metal 
is  dissolved  in  nitric  acid  (40  cc.  per  10  grams)  and  the  solution  boiled  until 
a  faint  green  precipitate  begins  to  appear  on  the  surface  of  the  solution. 
The  free  acid  being  expelled,  the  solution  is  made  faintly  acid  by  adding  1  to 
2  cc.  of  nitric  acid,  the  solution  diluted  300  to  700  cc.,  according  to  the  amount 
of  copper  taken,  and  then  electrolyzed  with  a  current  of  1.5  to  2  amperes  for 
thirty-six  hours,  with  a  spiral  anode  and  a  cathode  with  about  160  cm.  depositing 
surface.  The  solution  should  remain  slightly  acid  throughout  the  electrolysis, 
otherwise  cobalt,  nickel,  and  zinc  may  be  precipitated  as  hydroxides  from  a 
neutral  solution.  When  the  copper  is  nearly  removed,  the  electrodes  are  dis- 
connected, and  removed. 

The  solution  is  concentrated  by  boiling,  a  few  crystals  of  oxalic  acid  added, 
and  the  anode  (which  may  be  coated  with  Pb02)  immersed  in  the  hot  solution 
for  a  few  minutes,  then  rinsed  off  into  the  solution. 

Separation  of  Lead.  The  solution  is  evaporated  to  small  volume,  about 
40  cc.  of  dilute  sulphuric  acid  (1  :  1)  are  added  and  the  mixture  evaporated 
to  S03  fumes.  The  cooled  concentrate  is  diluted  with  100  cc.  of  water  and 
again  evaporated  to  fumes.  About  300  cc.  of  water  added  and  when  the  soluble 
salts  have  dissolved,  the  solution  is  filtered  and  the  residue,  PbS04,  washed. 
The  filtrate  contains  Zn,  Ni,  Co,  etc. 

Determination  of  Lead.  The  residue,  PbS04,  is  dissolved  by  successive 
treatments  with  ammonium  acetate  and  hot  water,  the  lead  precipitated  from 
the  solution,  made  slightly  acid  with  acetic  acid,  by  adding  a  slight  excess  of 
potassium  chromate  and  the  element  determined  as  lead  chromate  according 
to  the  standard  procedure  for  lead.  See  page  233  in  the  chapter  on  Lead. 

Removal  of  the  Hydrogen  Sulphide  Group.  The  nitrate  from  the  lead 
sulphate  is  saturated  with  H2S  and  filtered.  The  filtrate  contains  zinc,  cobalt, 
and  nickel.  To  recover  any  occluded  zinc,  the  precipitate  is  dissolved  in  nitric 
acid,  taken  to  fumes  with  sulphuric  acid,  diluted  to  about  200  cc.,  and  again 
treated  with  H2S.  The  filtrate  from  this  precipitate  is  combined  with  the  first 
portion.  The  precipitate  is  rejected. 

Removal  of  Iron.  This,  if  present,  will  be  found  in  the  filtrate.  The 
H2S  is  expelled  by  boiling  and  the  solution  concentrated  to  400  cc.  after  adding 
5  cc.  of  H202  to  oxidize  the  iron.  Five  grams  of  ammonium  sulphate  are  added, 
the  solution  made  strongly  ammoniacal,  and  filtered.  Iron  is  precipitated  as 
Fe(OH)3  and  is  thus  removed.  If  much  iron  is  present,  a  double  precipitation 
is  advisable  to  recover  any  occluded  zinc,  nickel,  or  cobalt,  and  the  filtrates 
combined. 

Determination  of  Zinc.  The  filtrate  from  iron  is  concentrated  to  400 
cc.,  then  made  neutral  to  litmus  by  cautious  addition  of  dilute  sulphuric  acid, 
drop  by  drop,  and  then  faintly  acid  with  3  drops  in  excess.  Zinc  is  now  pre- 
cipitated as  the  sulphide  by  saturating  the  solution  with  H2S  and  allowing 
to  stand  over  night.  The  sulphide  is  filtered  off.  The  filtrate  contains  cobalt 
and  nickel. 

Zinc  sulphide  is  dissolved  in  hot  dilute  HC1  (1  :  2)  and  a  few  crystals  of 
KC103.  The  solution  is  evaporated  to  dryness,  the  residue  taken  up  water  con- 
taining a  few  drops  of  HC1  and  the  extract  filtered.  (To  remove  any  Si02  dis- 


170  COPPER 

solved  from  the  beakers.)  Zinc  carbonate  is  now  precipitated  (in  a  beaker  of 
glass,  which  does  not  contain  zinc)  from  the  filtrate  by  addition  of  sodium  carbon- 
ate, and  ignited  to  the  oxide  ZnO. 

ZnOX  0.8034  =  Zn. 

Determination  of  Nickel  and  Cobalt.  The  filtrate  from  the  zinc  sulphide 
is  examined  for  nickel  and  cobalt.  About  0.5  cc.  of  sulphuric  acid  is  added. 
H2S  is  expelled  by  boiling,  and  2  cc.  of  H202  added.  The  solution  is  concentrated 
to  about  400  cc.  (this  should  be  free  from  nitric  acid),  treated  with  about 
25  cc.  of  ammonium  hydroxide,  and  electrolyzed  over  night  with  a  current  of  0.5 
amperes.  Nickel  and  cobalt,  if  present,  are  deposited  on  the  cathode  as  metals 
and  so  determined.  For  greater  details,  consult  the  chapter  on  Nickel  under 
the  method  by  electrolysis. 

Determination  of  Arsenic,  Antimony,  Selenium,  and  Tellurium 

Separation  of  Copper.  Ten  to  50  grams  of  blister  copper  and  100  to 
500  grams  of  refined  copper  are  required  for  the  determination.  (For  500-grams 
sample,  5  lots  of  100  grams  are  taken.)  The  drillings  are  dissolved  in  nitric  acid 
(40  cc.  per  10  grams)  and  the  solution  boiled  until  a  light-green  precipitate 
appears  on  the  surface.  The  liquor  is  diluted  to  500  cc.,  and  5  cc.  of  ferric 
nitrate  containing  3%  of  iron  are  added.  A  basic  acetate  precipitate  is  now  made, 
weak  sodium  hydroxide  being  added  to  neutralize  the  free  acid,  but  not  in 
sufficient  amount  to  produce  a  permanent  precipitate.  If  the  end-point  is 
overrun,  nitric  acid  is  added  drop  by  drop  until  the  solution  clears.  The 
solution  is  diluted  to  about  800  cc.,  20  cc.  of  a  saturated  solution  of  sodium 
acetate  added,  the  liquor  brought  to  boiling  and  filtered  hot  through  a  large 
creased  filter  paper,  the  first  portion  of  the  filtrate  being  poured  back  on  the 
filter.  The  residue  is  washed  twice  with  hot  water  to  remove  the  copper.  Five 
cc.  additional  iron  are  added  to  the  filtrate  and  a  second  basic  acetate  precipitation 
made,  a  separate  filter  being  used.  The  precipitates  are  dissolved  in  the  least 
amount  of  nitric  acid  necessary  and  the  solutions  combined.  The  liquor  is 
concentrated  to  150  cc.,  a  pinch  of  potassium  chlorate  added,  and  the  con- 
centration continued  until  the  volume  has  been  reduced  to  about  30  cc.  An 
equal  volume  of  strong  hydrochloric  acid  is  added  and  a  second  pinch  of  chlorate 
and  the  evaporation  repeated  to  eliminate  all  traces  of  nitric  acid. 

The  evaporation  is  best  conducted  in  a  casserole,  resting  in  the  circular 
opening  of  an  asbestos  board,  in  order  that  the  sides  of  the  vessel  may  be  pro- 
tected from  the  flame. 

Separation  and  Determination  of  Arsenic.  The  solution  is  transferred 
to  a  distillation  flask,  arsenic  reduced  with  ferrous  chloride,  and  distilled  according 
to  the  standard  procedure  for  this  element,  p.  33.1  In  this  distillate  arsenic  is 
determined  volumetrically.2  (See  chapter  on  subject.)  Antimony,  selenium 
and  tellurium  remain  in  the  flask. 

Separation  and  Determination  of  Antimony.  Twenty-five  cc.  of  a  saturated 
solution  of  zinc  chloride  are  added  to  the  liquor  remaining  in  the  distilling 

JThe  concentration  should  not  be  carried  below  30  cc. 

2  Arsenic  may  be  precipitated  by  H2S,  the  sulphide  dissolved  in  NH4OH,  the  filtrate 
taken  to  dryness,  HNOs  added  and  the  evaporation  repeated.  Arsenic  now  is  deter- 
mined by  precipitation  with  AgNO3  and  titration  of  the  silver  with  KCNS  in  presence 
of  a  ferric  salt.  AgX0.2316=As. 


COPPER  171 

flask  after  the  elimination  of  arsenic.  The  antimony  is  now  distilled,  strong 
hydrochloric  acid  being  introduced  in  the  distilling  flask  drop  by  drop  by  means 
of  a  separatory  funnel,  to  replace  the  solution  distilled,  the  volume  in  the  flask 
being  kept  as  low  as  possible,  avoiding  crystallization.  When  the  antimony 
has  been  completely  eliminated,  the  contents  of  the  distilling  flask  is  poured 
out  while  still  hot,  and,  together  with  the  rinsings  of  the  flask,  placed  aside 
for  the  subsequent  determination  of  selenium  and  tellurium. 

The  distillate  is  neutralized  with  ammonia,  then  made  slightly  acid  with 
HC1  and  antimony  precipitated  with  H2S.  Most  of  the  selenium  and  tellurium 
remain  in  the  flask.  Some  of  the  selenium,  however,  distills  with  the  antimony, 
hence  this  must  be  recovered  from  the  antimony  sulphide  precipitate  and  at 
the  same  time  this  must  be  purified. 

The  precipitate  is  dissolved  in  dilute  HC1  (1  :  2),  containing  a  little  bromine 
to  oxidize  the  sulphur.  The  solution  is  filtered  free  from  sulphur  and  the  filter 
washed  with  a  little  dilute  HC1.  The  filtrate  should  contain  one-third  its  volume 
of  strong  HC1.  Selenium  is.  now  precipitated  by  passing  in  S02  gas  to  satura- 
tion and  bringing  the  solution  to  boiling.  The  precipitate  is  allowed  to  settle 
several  hours  and  then  filtered  through  a  tared  Gooch  crucible.  (To  this  is 
added  the  selenium  and  tellurium  later  obtained  from  the  residue  of  the  flask.) 
The  filtrate  contains  antimony. 

After  boiling  out  the  S02,  the  filtrate  is  first  neutralized  with  ammonia,  then 
made  slightly  acid  with  hydrochloric  acid  and  antimony  precipitated  as  the 
sulphide  by  saturating  the  solution  with  H2S,  allowing  the  precipitate  to  settle, 
resaturating  with  H2S  and  again  allowing  to  settle.  The  filtered,  washed  pre- 
cipitate is  dissolved  with  sodium  sulphide,  and  10  cc.  of  25%  potassium  cyanide 
(poison)  added  to  the  filtrate,  together  with  2  cc.  of  25%  sodium  hydroxide. 

The  solution  is  now  electrolyzed  hot  (90°  C.)  for  an  hour  with  a  current  of 
0.5  ampere  and  antimony  deposited  as  the  metal  on  the  cathode.  This  is 
quickly  removed  and  washed  by  dipping  it  successively  into  a  beaker  of  cold 
water,  three  of  hot  water  and  one  of  95%  alcohol.  The  foil  is  dried  at  100°  C., 
and  then  weighed,  on  cooling,  as  usual.  Antimony  is  now  removed  by  immersing 
the  cathode  in  boiling  nitric  acid  containing  tartaric  acid,  and  washing  as 
before.  The  loss  of  weight  of  the  foil  is  taken  as  antimony. 

NOTE.  It  is  advisable  to  test  the  electrolyte  for  antimony  by  acidifying  the  solu- 
tion with  oxalic  acid  (Hood).  A  reddish  coloration  indicates  the  incomplete  removal 
of  the  element. 

Determination  of  Selenium  and  Tellurium.  The  solution  from  the  dis- 
tillation flask  is  nearly  neutralized  with  ammonia  and  saturated  with  H2S. 
The  precipitate  is  filtered  off  and  dissolved  in  equal  parts  of  nitric  acid  (sp.gr. 
1.42)  potassium  bromide  bromine  solution  (20  cc.  Br  added  to  a  saturated 
solution  of  KBr  and  diluted  to  200  cc.).  The  liquor  is  diluted  to  400  cc.,  5  cc. 
of  ferric  nitrate  (3%  Fe'")  solution  added,  and  sufficient  ammonia  to  make  the 
solution  decidedly  alkaline.  The  precipitate  contains,  besides  the  iron,  all  of 
the  selenium  and  tellurium,  whereas  any  copper  that  may  have  been  present 
is  removed.  The  precipitate,  washed,  is  dissolved  in  hydrochloric  acid^  the 
free  acid  nearly  neutralized  and  H2S  passed  in  to  saturation.  The  precipitate 
is  filtered  off,  washed,  and  dissolved  in  the  nitric  acid  potassium  bromide  and 
bromine  mixture  stated  above.  The  solution  is  filtered  and  then  sufficient  hydro- 
chloric acid  added  to  make  the  solution  contain  about  one-third  its  volume  of 
strong  HC1.  Selenium  and  tellurium  are  precipitated  from  this  solution  by  pass- 


172  COPPER 

ing  in  S02  to  saturation,  and  boiling  for  a  minute  or  so.  The  precipitate  is  now 
filtered  into  the  crucible  containing  the  selenium  obtained  in  the  purification  of 
the  antimony  precipitate.  After  washing  with  hot  water  and  once  with  95% 
alcohol,  the  residue  is  dried  at  100°  C,  for  an  hour  and  weighed  as  selenium  and 
tellurium.  Solution  should  stand  three  hours  at  least,  or  overnight,  before  filtering. 

NOTE.  The  precipitate  of  selenium  and  tellurium  may  contain  gold,  which  should 
be  determined  by  assay. 

Determination  of  Oxygen 

This  determination  is  required  only  in  refined  copper.  The  method  depends 
upon  the  reduction  with  hydrogen  of  cuprous  oxide  heated  to  redness;  the  water 
formed  by  the  reaction  being  the  measure  of  the  oxygen. 

Apparatus.  The  combustion-furnace  is  the  same  as  that  used  for  the 
determination  of  carbon.  As  it  is  necessary  that  the  hydrogen  be  absolutely 
free  from  oxygen  and  moisture,  the  gas  is  passed  through  a  preheater  con- 
sisting of  a  platinum  or  silica  tube  of  small  bore  heated  to  redness  by  a  flame 
or  an  electrical  device.  The  gas  is  then  passed  through  a  tube  containing 
calcium  chloride  and  finally  through  a  P205  bulb  containing  the  anhydride. 
In  this  purified  form  it  enters  the  combustion-tube.  The  product  of  com- 
bustion, water,  is  absorbed  in  a  tared  bulb  by  P205,  to  which  is  attached  a  tube 
of  calcium  chloride. 

Procedure.  The  sample,  which  has  been  drilled  with  considerable  care 
to  avoid  overheating,  is  dried  under  partial  vacuum  in  a  desiccator  after  warming 
to  below  70°  C.  for  a  few  minutes. 

One  hundred  grams  are  taken  for  analysis  and  placed  in  the  combustion 
tube,  the  drillings  being  held  in  a  large  boat.  Purified  hydrogen  is  rapidly 
passed  through  the  tube  for  half  an  hour  to  sweep  out  the  air,  the  tube  being 
cold.  The  tared  P206  bulb  and  the  calcium  chloride  tube  are  now  attached. 
The  heat  is  turned  on  to  bring  the  sample  to  cherry  red  heat,  900°  C.,  and  the 
current  of  hydrogen  passed  slowly  over  the  sample  for  several  hours. 

The  increase  of  weight  of  the  P206  bulb  =H20. 

H2OX0.8881  =0.     0X4.9687  =  CuO. 


Determination  of  Sulphur 

This  determination  is  rarely  required  in  refined  copper. 

Twenty  grams  of  blister,  unrefined  or  cement  copper,  placed  in  a  casserole, 
ire  treated  cold  with  50  cc.  bromine-potassium  bromide  mixture  (see  under 
Determination  of  Selenium  and  Tellurium).  After  standing  at  least  ten 
minutes,  100  cc.  of  strong  nitric  acid  are  added.  After  another  ten  minutes 
the  casserole  is  placed  on  the  steam  bath  and  the  solution  evaporated  to  small 
volume.  This  is  taken  up  with  25  cc.  of  strong  hydrochloric  acid  and  evaporated 
to  a  pasty  mass.  The  treatment  is  repeated  to  ensure  the  decomposition  of 
nitrates  and  to  expel  nitric  acid.  It  is  now  taken  up  with  5  cc.  of  hydrochloric 
acid,  diluted  with  water  and  sulphuric  acid  precipitated  as  BaS04,  according 
to  the  standard  procedure  for  sulphur.  See  p.  395. 

BaS04X0.1374=S. 


COPPER  173 

Determination  of  Phosphorus 

This  determination  is  seldom  required,  and  then  only  in  low-grade  copper 
and  copper  scrap  containing  phosphor  bronze.  The  sample,  dissolved  in  nitric 
acid,  is  treated  with  ferric  nitrate  and  the  basic  acetate  precipitation  made  as 
has  been  described  for  the  determination  of  arsenic,  etc.  The  precipitate  is 
dissolved  in  HC1,  this  solution  then  made  strongly  ammoniacal,  and  saturated 
with  H2S,  and  filtered.  The  filtrate  containing  the  arsenic  and  phosphoric 
acid  is  acidified,  arsenic  sulphide  and  sulphur  filtered  off,  and  phosphoric  acid 
determined  in  the  filtrate  by  precipitation  with  magnesia  mixture  as  usual. 
See  chapter  on  Phosphorus. 

Mg2P207X.2787=P. 

DETERMINATION  OF  COPPER   IN  REFINED  COPPER 

In  determining  the  quality  of  copper  for  electrical  purposes  each  hundredth 
of  a  percent  above  99.90  has  its  significance.  The  methods  employed  are  the  elec- 
trolytic and  the  hydrogen  reduction  methods.  Silver  present  is  rated  as  copper. 

Electrolytic  Method.1  The  sample,  consisting  of  unground  drillings,  should 
be  untarnished,  free  of  grease  or  oil,  and  cleaned  of  particles  of  iron  by  use  of  a 
good  magnet. 

Procedure.  A  catch  weight  of  about  5  grams  is  taken,  each  piece  being  ex- 
amined for  dust,  particles  from  the  drill  and  surface  oxidation  before  it  is 
placed  on  the  balance  pan.  Solution  is  effected  in  a  special  400  cc. 
beaker  which  has  hipped  sides  to  support  a  series  of  watch 
glasses,  the  lower  hip  at  the  125  cc.  mark,  the  upper  at  350  cc. 
(Fig.  32.) 

The  drillings  are  treated  with  50  cc.  of  a  stock  solution  (10.5 
p  .rts  nitric  acid  and  4.5  parts  of  sulphuric).  The  watch-glass 
traps  are  put  in  place  to  retain  the  copper  which  is  always 
entrained  in  the  nitrogen  peroxide  fumes.  Except  that  the  cur- 


rent is  maintained  at  .75  ampere  throughout  the  period  of  elec-        FIG.  32. 

trolysis,  the  conditions  are  the  same  as  have  been  described  for 

the  determination  of  copper  by  the  "  Small  Portion  Method."     (Page  159.) 

Hydrogen  Reduction  Method.  This  method  is  applicable  to  the  determina- 
tion of  copper  in  grades  of  refined  copper  which  are  characterized  by  a  metallic 
impurity  content  which  is  constant  and  less  than  0.01  per  cent.  The  apparatus 
consists  of  a  combustion  furnace,  preferably  electrolytically  heated,  the  tem- 
perature of  which  can  be  kept  constant  at  about  950°  C.;  a  silica  tube  of  f-in. 
bore,  one  end  of  which  is  connected  with  a  large  Peligot  tube  containing  con- 
centrated sulphuric  acid,  the  other  end  is  connected  by  a  rubber  plug  and  flexible 
tube  with  a  source  of  purified  hydrogen;  porcelain  combustion  boats  95  mm. 
long,  18  mm.  wide  and  10  mm.  deep. 

Procedure.  A  catch  weight  of  about  25.1  grams  of  drillings  is  placed  in  the 
combustion  boat,  and  the  boat  inserted  in  the  silica  tube.  After  passing  hydrogen 
for  half  an  hour  through  the  cold  tube,  the  temperature  is  raised  to  950°  C.  and 
so  maintained  for  two  hours.  If  the  furnace  is  of  a  type,  which  will  permit  the 
removal  of  the  tube  without  disconnecting  the  train,2  the  tube  is  taken  from  the 

1  Ferguson,  Jour.  Ind.  and  Eng.  Chem.,  May,  1910. 

2  Electric  Heating  Apparatus  Co.,  New  York. 


174 


COPPER 


furnace  without  interruption  of  the  stream  of  hydrogen  and  cooled  by  a  jet  of  cold 
air.  When  cold,  the  mass  of  copper,  the  particles  of  which  are  cemented,  is  taken 
from  the  boat  and  weighed. 

NOTE.  If  the  sample  is  allowed  to  become  molten,  the  boat  and  tube  will  be  coated 
with  a  film  of  copper. 

A  convenient  and  efficient  type  of  combustion  furnace,  hinged  design,  is  shown  in 
Fig.  326.  This  furnace  may  be  purchased  from  the  Electric  Heating  Apparatus  Com- 
pany, New  York  City. 


FIG.  32a. — Combustion  Furnace,  Hinged  Design,  Type  70 — Shown  with  one  "  Spare  " 

Unit.     Height  to  center,  9£". 
By  courtesy  of  the  Electric  Heating  Apparatus  Company,  New  York  City. 


CHLORINE  IN  CEMENT  COPPER  AND  COPPER  ORES 

If  the  material  contains  very  little  silver  the  following  method  is  applicable 
in  laboratories  equipped  with  apparatus  for  furnace  assaying. 

Ten  grams  of  the  finely  ground  sample  placed  in  an  800  cc.  beaker  are  treated 
with  600  cc.  water,  100  cc.  nitric  acid  (free  from  iodic  acid)  and  the  mixture 
brought  to  boiling  by  gentle  heating.  After  filtration  and  thorough  washing,  the 
insoluble  residue  is  treated  repeatedly  with  additional  water  and  acid,  of  the  above 
proportion,  until  a  test  of  the  filtrate  with  silver  nitrate  indicates  complete  extrac- 
tion of  the  soluble  chloride.  The  combined  filtrates  are  treated  with  a  slight  excess 
of  silver  nitrate  and  chloride  of  silver  precipitated  and  determined  in  the  usual  way. 
Page  124. 

On  a  separate  10  gram  sample  an  assay  of  silver  is  made  and  the  equivalent 
weight  of  chloride  calculated.  This  equivalent  is  added  to  the  weight  of  silver 
chloride  obtained  in  the  extract.  The  percent  of  chlorine  is  calculated  from  this 
result  by  the  formula. 


Weight  of  AgClX. 2474X100 
10 


=gram  chlorine. 


COPPER 


DETERMINATION  OF  COPPER   IN  BLUE  VITROL 


175 


This  i§  best  determined  on  a  2  gram  sample  of  the  finely  powdered  dry  salt  or 
a  catch  weight  of  approximately  2  grams  if  the  salt  is  moist.  Copper  is  deposited 
electrolytically,  the  electrolyte  being  diluted  to  130  cc.  and  containing  4  cc.  of 
nitric  acid  and  5  cc.  saturated  solution  of  ammonium  nitrate.  A  current  of  .18 
amperes  and  an  electrode  of  11|  sq.  in.  depositing  surface  are  used.  If  the  salt 
contains  insoluble  matter  consisting  wholly  of  basic  salts,  complete  solution  is 
brought  about  by  gently  boiling  after  adding  4  cc.  nitric  acid  and  25  cc.  of  hot 
water  to  the  salt.  If  the  insoluble  matter  shows  a  tendency  to  remain  in  suspen- 
sion, the  presence  of  arsenic  or  antimony  is  indicated.  In  this  case  the  impurities 
are  precipitated  along  with  ferric  hydroxide  as  has  been  previously  described 
under  the  notes  on  the  electrolytic  determination  of  copper  in  blister  copper, 
page  162. 

DETERMINATION  OF  COPPER  AND  LEAD   IN  BRASS1 

One  gram  of  the  alloy  is  dissolved  in  8  cc.  nitric  acid  and  the  nitrous  fumes 
are  boiled  off;  if  tin  is  present,  40  cc.  of  boiling  water  are  added,  the  metastannic 
acid  allowed  to  settle  on  the  hot  plate  for  fifteen  minutes  and  filtered  off. 
(Method  for  tin  is  accurate  only  for  wrought  brass;  high  iron  or  antimony 
interfere). 

The  filtrate  from  the  tin  is  electrolyzed  for  copper  and  lead.  If  the  lead  is 
less  than  0.75  per  cent,  an  ordinary  sandblasted,  spiral  anode  is  used;  if  the 
amount  of  lead  is  0.75  to  />  per  cent  a  sandblasted  gauze  cylinder  is  necessary. 
For  amounts  of  lead  over  5  per  cent  either  a  smaller  sample  is  taken  or  the  greater 
part  of  the  lead  is  precipitated  as  lead  sulphate  and  the  small  amount  of  lead 
passing  into  the  filtrate  is  recovered  by  electrolysis,  using  £•  ampere  current  per 
solution,  after  adding  3  cc.  of  nitric  acid.  For  lead  under  0.5  per  cent;  5  cc.  of 
1  : 1  sulphuric  acid  are  stirred  in,  after  the  current  has  been  passing  for  at  least 
ten  minutes.  If  the  lead  is  high  the  sulphuric  acid  is  added  after  the  electrolysis 
has  continued  for  at  least  an  hour.  Under  these  conditions  no  lead  sulphate 
deposits  from  the  solution  and  as  long  as  the  current  passes,  the  sulphuric  acid 
present  does  not  attack  the  Pb02  deposited.  After  the  sulphuric  acid  is  added 
the  current  is  raised  to  ^  ampere  per  solution  and  the  electrolysis  continued  over- 
night. 

The  lead  peroxide  is  dried  at  250°C.  for  half  an  hour.  The  factor  £6. 13 
gives  the  equivalent  per  cent  lead.  (Factor  determined  from  the  average  of  a 
large  number  of  tests  made  on  pure  lead.  The  factor  is  best  obtained  under  the 
conditions  of  the  laboratory  where  the  determinations  are  made,  as  it  varies  slightly 
with  change  of  conditions.) 

The  copper  on  the  cathode  is  washed,  dried  and  weighed  according  to  the  usual 
standard  procedure. 

1  Method  of  The  National  Brass  and  Copper  Tube  Company,  communication  by 
R.  T.  Roberts. 


FLUORINE 

WILFRED  W.  SCOTT 

F',  at.wt.  19;  D  (air)  1.3115°,  sp.gr.  (-187°)  1.14;  m.p.  -223;  b.p.  -187°  C; 

acids,  HF,  H2SiF6. 

DETECTION 

Fluorine  is  the  most  active  element  known,  and  is  by  far  the  most  active 
of  the  halogens,  displacing  chlorine,  bromine,  and  iodine  from  their  combinations. 
Etching  Test.    The  procedure  depends  upon  the  corrosive  action  of  hydro- 
fluoric acid  on  glass,  the  acid  being  liberated  from  fluorides  by  means  of  hot 

concentrated  sulphuric  acid.  This  test  is 
applicable  to  fluorides  that  are  decomposed 
by  sulphuric  acid.  The  reactions  taking  place 
may  be  represented  as  follows: 

I.    CaF2+H2S04  =  CaS04+2HF. 
II.    Si02+4HF=2H20+SiF4. 

The  test  may  be  carried  out  in  the  appa- 
ratus shown  in  the  illustration,  Fig.  33.  A 
clear,  polished  glass  plate  2  ins.  square,  free 
from  scratches,  is  warmed  and  molten  wax 
allowed  to  flow  over  one  side  of  the  plate,  the 
excess  of  wax  being  drained  off.  A  small  mark 
is  made  through  the  wax,  exposing  the  surface 
of  the  plate,  care  being  exercised  not  to  scratch 
the  glass.  If  the  test  is  to  be  quantitative, 
the  marks  should  be  of  uniform  length  and 
width.  The  powdered  material  is  placed  in  a 
large  platinum  crucible  (B)  (a  lead  crucible 
will  do) ;  sufficient  concentrated  sulphuric  acid 
is  added  to  cover  the  sample.  The  plate  (D) 
with  the  wax  side  down  is  placed  over  the 
FIG.  33.— Etching  Test  for  Fluorine,  crucible  and  pressed  firmly  down.  To  prevent 

the  wax  from  melting,  a  condenser  (C),  with 

flowing  water,  cools  the  plate.  An  Erlenmeyer  flask  (C)  is  an  effective  and  simple 
form  of  condenser,  though  a  metallic  cylinder  is  a  better  conductor  of  heat.  A 
little  water  placed  on  the  plate  makes  better  contact  with  the  condenser.  As  a 
further  protection  a  wide  collar  of  asbestos  board  (E}  may  be  placed  as  shown 
in  the  figure.  In  quantitative  work,  where  a  careful  regulation  of  heat  is  nec- 
essary, the  crucible  is  placed  in  a  casserole  with  concentrated  sulphuric  acid  or 
in  a  sand  bath,  containing  a  thermometer  to  register  the  temperature.  The  run 
is  best  conducted  at  a  temperature  of  200°  C.  (not  over  210° — H2S04  fumes). 

176 


G/05 


Plate 


FLUORINE 


177 


After  an  hour  the  wax  is  removed  with  hot  water  and  the  plate  wiped  clean, 
and  examined  by  reflected  light  for  etching.  A  test  is  positive  when  the  mark 
can  be  seen  from  both  sides  of  the  glass.  Breathing  over  the  etched  surface 
intensifies,  the  mark. 

Treatment  of  Fluo-Silicates  not  Attacked  by  Sulphuric  Acid.  The 
powdered  material  is  mixed  with  about  eight  times  its  weight  of  sodium  car- 
bonate and  fused  in  a  platinum  crucible.  The  cooled  melt  is  extracted  with 
water.  Calcium  fluoride  is  thrown  out  from  the  filtrate,  according  to  directions 
under  Preparation  and  Solution  of  the  Sample.  The  fluoride  may  now  be 
tested  as  directed  in  the  etching  test  or  as  follows  by  the  hanging  drop  test. 

The  Hanging  Drop  Test.  The  test  depends  upon  the  reaction  3SiF4+3H20 
=  2H2SiF6+H2Si03. 

If  the  material  contains  carbonates,  it  is  calcined  to  expel  carbon  dioxide. 
Half  a  gram  of  the  powdered  dry  material  is  mixed  with  0.1  gram  dried  pre- 
cipitated silica  and  placed  in  a  test-tube,  Fig.  34,  about 
5  cm.  long  by  1  cm.  in  diameter.  A  one-hole  rubber 
stopper  fits  in  the  tube.  A  short  glass  tube,  closed  at  the 
upper  end,  passes  through  the  stopper  extending  about 
3  mm.  below.  Two  or  three  drops  of  water  are  placed  in 
this  small  tube  by  means  of  a  pipette,  nearly  filling  it. 
Two  cc.  of  concentrated  sulphuric  acid  are  added  to  the 
sample  in  the  test-tube  and  this  immediately  closed  by 
inserting  the  stopper  carrying  the  hanging  drop  tube,  exer- 
cising care  to  avoid  dislodging  the  drop  of  water.  The 
test-tube  is  placed  in  a  beaker  of  boiling  water  and  kept 
there  for  thirty  minutes.  If  an  appreciable  quantity  of 
fluorine  is  present  a  heavy  gelatinous  ring  of  silicic  acid 
will  be  found  at  the  end  of  the  hanging  drop  tube  in  the 
stopper. 

It  is  important  to  have  material,  test-tube,  and  rubber 
stopper  dry,  so  that  the  deposition  may  occur  as  stated.1 

NOTE.     Dr.  Olsen2  makes  the  test  by  heating  the  sample  in 

a  small  Erlenmeyer  flask,  with  concentrated  sulphuric  acid. 

A  watch-crystal  with  a  drop  of  water  suspended  on  its  curved 

surface  is  placed  over  the  mouth  of  the  flask.     A  spot  etch  is  obtained  in  presence  of 

fluorine. 

Black  Filter  Paper  Test.  According  to  Browning,3  small  amounts  of  fluorine 
may  be  detected  by  the  converse  method  for  detection  of 
silicates  and  fluosilicates  ( See  silicon) .  The  fluoride  is 
placed  with  a  suitable  amount  of  silica,  in  a  small  lead  cup, 
1  cm.  in  diameter  and  depth  (Fig.  35) ;  a  few  drops  of 
concentrated  sulphuric  are  added;  the  cup  is  covered  by  a 
flat  piece  of  lead  with  a  small  hole  in  the  center;  upon  the 
cover  is  placed  a  piece  of  moistened  black  filter  paper  and 
upon  this  a  small  pad  of  moistened  filter  paper.  The  cup 

is  heated  on  the  steam  bath  for  ten  or  fifteen  minutes.    A  white  deposit  will 

1C.  D.  Howard;  Jour.  Am.  Chem.  Soc.,  1906,  28,  1238-1239.  C.  N.,  1906,  30, 
420. 

2  Communicated  to  the  author  by  J.  C.  Olsen. 

3  P.  E.  Browning,  Am.  Jour.  Sci.  (4),  32,  249. 
by  F.  A.  Gooch. 


FIG.  34. 

Hanging  Drop  Test 
for  Fluorine. 


J  L 


FIG.  35. 


Methods  in  Chemical  Analysis/' 


178  FLUORINE 

be  found  on  the  under  side  of  the  black  filter  paper,  over  the  opening  in  the 
cover,  if  fluorine  is  present  in  an  appreciable  amount.  (0.001  gram.  CaF2  or 
above,  and  0.005  gram  Na3AlF6  will  give  the  test.) 

ESTIMATION 

The  determination  of  fluorine  in  the  evaluation  of  minerals  used  for  the 
production  of  hydrofluoric  acid  is  of  technical  importance.  The  demand  for 
elimination  of  the  use  of  fluorides  for  preservatives  of  food  makes  its  estimation 
in  small  amounts  of  importance. 

Fluorine  occurs  only  combined.  It  is  found  abundantly  combined  with  lime 
in  the  mineral  fluorspar,  CaF2.  It  occurs  as  cryolite,  Na3AlF6;  apatite, 
3Ca3(P04)2CaF2.  It  is  found  in  mineral  springs,  ashes  of  plants,  in  bones,  and  in 
the  teeth  (CaF2).  It  occurs  sparingly,  with  aluminum  and  silicon,  in  topaz, 
and  with  cerium  and  yttrium  in  fluocerite,  yttrocerite,  also  in  wavellite,  wag- 
nerite,  etc. 

Preparation  and  Solution  of  the  Sample 

Fluorides  of  the  alkalies,  and  of  silver  and  mercury,  are  readily  soluble; 
copper,  lead,  zinc,  and  iron  fluorides  are  sparingly  soluble;  the  alkaline  earth 
fluorides  dissolve  in  100  cc.  H20  as  follows:  BaF2  =0.163  gram,  SrF2  =0.012 
gram,  CaF2  =0.0016  gram. 

Fluosilicates  of  potassium,  sodium,  and  barium  are  slightly  soluble  in  water 
and  practically  insoluble  if  sufficient  alcohol  is  added. 

Organic  Substances.1  These  are  best  decomposed  by  the  lime  method,  the 
details  of  which  are  given  in  the  chapter  on  chlorine  under  the  section  for  the 
preparation  and  solution  of  the  sample,  p.  122.  For  fluorides  in  organic 
matter  it  is  advisable  to  decompose  the  substance  in  a  seamless  nickel  tube, 
40  mm.  long  by  4-5  mm.  bore.  The  end  of  the  tube  is  sealed  with  silver  solder. 
The  lime  used  should  be  soluble  in  acetic  acid.  The  tube  is  heated  to  yellow 
heat  for  two  hours.  The  lime  is  then  extracted  with  acetic  acid  and  fluorine 
determined  as  calcium  fluoride. 

Silicious  Ores  and  Slags.  0.5  to  1.0  gram  of  material  is  fused  in  a  cru- 
cible with  ten  times  its  weight  of  sodium  and  potassium  carbonates  (1:1)  and 
poured  into  an  iron  mould.  If  a  porcelain  crucible  has  been  used,  this  is  broken 
up  and  added  to  the  cooled  fusion.  The  mass  is  digested  with  about  200  cc. 
of  hot  water  for  an  hour,  the  mass  having  been  broken  up  into  small  lumps, 
(Kneeland  recommends  using  an  agate-ware  casserole  as  diminishing  the  liability 
of  subsequent  bumping) 2  then  boiled  briskly  for  ten  minutes  longer  and  filtered, 
the  solution  being  caught  in  a  large  beaker.  The  residue  is  washed  with  hot 
water,  followed  by  a  hot  solution  of  ammonium  carbonate  and  the  insoluble 
material  rejected.  The  silica  is  removed  with  ammonium  carbonate,  followed 
by  the  zinc  oxide  treatment  of  the  second  filtrate,  as  described  under  the  section 
of  Separations.  In  presence  of  appreciable  amounts  of  fluorides,  the  gravi- 
metric precipitation  of  fluorine  as  calcium  fluoride  is  recommended. 

1 H.  Meyer  and  A.  Hub,  Monatsch.  fur  Chem.,  1910,  31,  933-938.  C.  N..  1910, 
35,  489. 

2E.  Kneeland,  Eng.  and  Min.  Jour.,  80,  1212.  A.  H.  Low,  "Technical  Methods 
of  Ore  Analysis." 


FLUORINE  179 

Calcium  Fluoride.1  The  product  is  best  decomposed  by  fusion  with  sodium 
and  potassium  carbonates,  after  mixing  the  fluoride  with  2.5  times  as  much  silicic 
acid,  followed  by  ten  times  its  weight  of  carbonates.  Most  of  the  silicic  acid  and 
all  the  fluorine  will  be  changed  to  soluble  alkali  salts,  while  the  calcium  will  be 
left  as  insoluble  calcium  chloride.  The  mixture  should  be  heated  gradually  to 
prevent  the  contents  of  the  crucible  from  running  over  the  sides  by  a  rapid  evo- 
lution of  carbon  dioxide.  The  thin  liquid  fusion  soon  thickens  to  a  pasty  mass. 
The  reaction  is  complete  when  there  is  no  further  evolution  of  carbon  dioxide. 
The  fused  mass  is  now  extracted  with  hot  water  as  indicated  above,  and  the 
soluble  fluoride  filtered  from  the  calcium  carbonate  residue.  Silicic  acid  is 
removed  from  the  filtrate  by  addition  of  ammonium  carbonate.  Traces  of 
silicic  acid  are  removed  from  the  filtrate  taken  to  near  dryness,  after  neutralizing 
the  alkali  with  dilute  hydrochloric  acid  (phenolphthalein  indicator),  by  the  zinc 
oxide  emulsion  method  given  under  Separations.  Fluorine  is  precipitated  as 
calcium  fluoride,  according  to  the  procedure  given  later  on  page  180. 

Soluble  Fluorides.  The  salts  are  dissolved  in  water.  In  presence  of  free 
acid  a  platinum  dish  should  be  used  and  the  acid  neutralized  with  sodium  car- 
bonate with  addition  of  about  one-fourth  as  much  more  in  excess.  The  fluoride 
is  then  precipitated  as  calcium  fluoride. 

Hydrofluoric  Acid.  The  acid  may  be  titrated  with  standard  caustic. 
Determined  gravimetric  ally,  the  acid  is  neutralized  and  fluorine  precipitated  as 
calcium  fluoride  or  lead  chlorofluoride  (pages  180,  181). 

Valuation  of  Fluorspar.  Details  of  the  procedure  worked  out  by  E.  Bidtel, 
Chief  Chemist,  Fairview  Fluorspar  and  Lead  Company,  are  given  at  the  close 
of  the  chapter. 

SEPARATIONS 

Removal  of  Silicic  Acid  from  Fluorides.  This  separation  is  frequently 
required,  especially  in  samples  where  the  sodium  and  potassium  carbonate 
fusion  has  been  required  for  decomposition  of  fluosilicates,  or  calcium  fluoride 
mixed  with  silicic  acid.  (See  Preparation  and  Solution  of  the  Sample.) 

To  the  alkaline  solution  about  5  to  10  grams  of  ammonium  carbonate  are 
added,  the  solution  boiled  for  five  minutes  and  allowed  to  stand  in  the  cold 
for  two  or  three  hours.  (Treadwell  and  Hall  recommend  heating  to  40°  C., 
and  allowing  to  stand  over  night.)  The  precipitate  is  filtered  off  and  washed 
with  ammonium  carbonate  solution.  The  fluoride  passes  into  the  filtrate,  while 
practically  all  of  the  silicic  acid  remains  on  the  filter. 

Small  amounts  of  silica  in  the  filtrate  are  removed  by  evaporating  the  solu- 
tion to  near  dryness  on  the  water  bath,  then  neutralizing  the  carbonate  with 
dilute  hydrochloric  acid  (phenolphthalein  indicator)  added  to  the  residue  taken 
up  with  a  little  water.  Upon  boiling  the  pink  color  is  restored,  the  solution 
then  cooled  and  acid  again  added  to  discharge  the  color;  this  is  repeated  until 
finally  the  addition  of  1-2  cc.  of  2  N.  HC1  is  sufficient  to  discharge  the  color. 
Four  to  5  cc.  of  ammoniacal  zinc  oxide  solution  (moist  ZnO  dissolved  in 
NH4OH— Low  recommends  20  cc.  of  an  emulsion  of  ZnO  in  NH4OH)  is  added 
and  the  mixture  boiled  until  ammonia  has  been  completely  expelled.  The 
precipitate  of  zinc  silicate  and  oxide  is  filtered  pnd  washed  with  water.  The 
puoride  is  determined  in  the  filtrate  by  precipitation  with  calcium  chloride 
as  directed  later. 

1  Treadwell  and  Hall,  Analytical  Chem.,  p.  472. 


180  FLUORINE 

Separation  of  Hydrofluoric  and  Phosphoric  Acids.  The  method  of  Rose 
modified  by  Treadwell  and  Koch,1  takes  advantage  of  the  fact  that  silver  phos- 
phate is  insoluble  in  water,  whereas  silver  fluoride  is  soluble.  The  alkaline 
solution  of  the  salts  of  the  acids  (solution  of  the  sodium  carbonate  fusions)  is 
carefully  neutralized  with  nitric  acid  and  transferred  to  a  300-cc.  calibrated 
flask.  A  slight  excess  of  silver  nitrate  solution  is  added,  and  the  mixture  made 
to  volume  and  thoroughly  shaken.  After  settling,  the  solution  is  filtered 
through  a  dry  filter,  the  first  10  to  15  cc.  being  rejected;  225  cc.  of  this  filtrate 
is  again  transferred  to  a  300-cc.  calibrated  flask,  the  excess  of  silver  precipitated 
by  adding  sodium  chloride  solution,  and  after  diluting  to  the  mark  and  snaking, 
the  precipitate  is  again  allowed  to  settle;  200  cc.  of  this  solution  is  taken  for 
analysis,  after  filtering  as  previously  directed.  This  sample  represents  50%  of  the 
original  sample  taken.  Fluorine  is  now  determined  by  one  of  the  procedures 
outlined. 

Separation  of  Hydrofluoric  and  Hydrochloric  Acids.  The  solution  con- 
taining hydrofluoric  and  hydrochloric  acids,  in  a  platinum  dish,  is  treated  with 
nitric  acid  and  silver  nitrate.  The  chloride  is  precipitated  as  the  silver  salt, 
whereas  the  fluorine  remains  in  solution  and  may  be  filtered  off  through  a  glass 
funnel  coated  with  paraffine  or  wax,  or  a  hard  rubber  funnel.  In  presence  of 
phosphoric  acid,  silver  nitrate  added  to  the  solution  will  precipitate  the  phos- 
phate as  well  as  the  chloride,  whereas  the  fluoride  remains  in  solution.  The 
phosphate  may  be  dissolved  out  from  the  chloride  by  means  of  dilute  nitric 
acid. 

Separation  of  Hydrofluoric  and  Boric  Acids.  An  excess  of  calcium 
chloride  is  added  to  the  boiling  alkali  salt  solutions  of  the  two  acids.  The 
precipitate  is  filtered  off  and  washed  with  hot  water.  The  residue,  consisting  of 
calcium  fluoride,  borate  and  carbonate,  is  gently  ignited  and  then  treated  with 
dilute  acetic  acid,  taken  to  dryness,  and  the  residue  taken  up  with  acetic  acid 
and  water.  Calcium  acetate  and  borate  are  dissolved,  whereas  the  fluoride 
remains  insoluble  and  may  be  filtered  off  and  determined. 


GRAVIMETRIC   METHODS   FOR  THE   DETERMINATION 

OF   FLUORINE 

Precipitation  as  Calcium  Fluoride 

The  method  utilizes  the  insolubility  of  calcium  fluoride  in  dilute  acetic  acid 
in  its  separation  from  calcium  carbonate,  the  presence  of  which  facilitates 
filtration  of  the  slimy  fluoride.  The  reaction  for  precipitation  is  as  follows: 

2NaF+CaCl2  =CaF2+2NaCl. 

Procedure.  Solution  of  the  sample  and  the  removal  of  silica  having  been 
accomplished  according  to  procedures  given  under  Preparation  and  Solution 
of  the  Sample,  and  Separations,  the  solution  is  neutralized,  if  acid,  by  the 
addition  of  sodium  carbonate  in  slight  excess;  if  basic,  by  addition  of  hydrochloric 
acid  in  excess,  followed  by  sodium  carbonate.  To  this  solution,  faintly  basic, 
1  cc.  of  twice  normal  sodium  carbonate  reagent  is  added,  followed  by  sufficient 

1Z.  anal.  Chem.,  43,  400,  1004.  "Analytical  Chemistry,"  Vol.  2,  by  Tread- 
well  and  Hall.  John  Wiley  and  Sons. 


FLUORINE  181 

calcium  chloride  solution  to  precipitate  completely  the  fluoride  and  the  excess 
of  carbonate,  i.e.,  until  no  more  precipitate  forms,  and  then  2-3  cc.  in  excess. 
After  the  precipitate  has  settled,  it  is  filtered  and  washed  with  hot  water.  (The 
nitrate  should  be  tested  for  fluoride  and  carbonate  with  additional  ca*lcium 
chloride.)  The  precipitate  of  calcium  fluoride  and  carbonate  is  dried  and 
transferred  to  a  platinum  dish,  the  ash  of  the  filter,  burned  separately,  is  added 
and  the  material  ignited.  After  cooling,  an  excess  of  dilute  acetic  acid  is  added, 
and  the  mixture  evaporated  to  dryness  on  the  water  bath.  The  lime  is  con- 
verted to  calcium  acetate,  while  the  fluoride  remains  unaffected.  The  residue 
is  taken  up  with  a  little  water,  filtered  and  washed  with  small  portions  of  hot 
water,  by  which  procedure  calcium  acetate  is  removed,  while  calcium  fluoride 
remains  on  the  filter.1  The  residue  is  dried,  separated  from  the  filter  and 
ignited.  This,  together  with  the  ash  of  the  filter,  is  weighed  as  calcium 
fluoride,  CaF2. 

To  confirm  the  result,  the  residue  is  treated  with  a  slight  excess  of  sulphuric 
acid  and  taken  to  fumes  in  a  platinum  dish.  The  adhering  acid  is  removed  as 
usual  by  heating  with  ammonium  carbonate,  and  the  ignited  residue  weighed  as 
calcium  sulphate.  One  gram  of  calcium  fluoride  should  yield  1.7436  grams  of 
calcium  sulphate.2 

CaOX1.3924  =  CaF2,  or  X0.677  =  F. 


Factors.  CaF2  X  0.4867  =F,  or  X0.5126=HF,  or  XL0757=NaF.  CaS04 
X0.5735=CaF2,  or  X0.2937=F,  or  X0.2539=HF. 

Precipitation  of  Fluorine  as  Lead  Chlorofluoride 

The  method,  worked  out  by  Starck,3  takes  advantage  of  the  double  halide 
formed  by  action  of  lead  chloride  upon  a  soluble  fluoride.  The  compound, 
PbFCl,  is  about  fourteen  times  the  weight  of  the  fluorine  it  contains.  Unfor- 
tunately, the  compound  is  quite  appreciably  soluble  in  water,4  so  that  a  loss 
occurs  if  pure  water  is  used  for  washing  the  precipitate.  The  method  is  limited 
to  the  determination  of  soluble  fluorides. 

The  sample,  made  neutral,  is  treated  with  a  large  excess  of  a  cold  saturated 
solution  (200  cc.  PbCl2  per  0.1  gram  NaF  in  50  cc.  solution)  of  lead  chloride, 
the  precipitate,  settled  over  night,  is  filtered  off  in  a  weighed  Gooch  crucible, 
washed  several  times  with  a  saturated  solution  of  lead  chlorofluoride,  and 
finally  two  or  three  times  with  ice-cold  water.  The  compound  is  dried  two  hours 
at  140-150°  C.,  and  weighed  as  PbFCl. 


results  are  slightly  low,  owing  to  the  solubility  of  calcium  fluoride: 
100  cc.  H2O  dissolves  0.0016  gram  CaF2;  100  cc.  1.5  N.  HC2H3O2  dissolves  0.0  11  gram. 

2  Low  recommends  disintegration  of  the  fluoride  with  sulphuric  acid,  diluting 
the  mixture  with  water,  boiling  with  ammonium  chloride,  and  then  with  ammonium 
hydroxide  and  hydrogen  peroxide.  Calcium  oxalate  is  now  precipitated  from  the 
filtrate  and  CaO  determined  by  titration  with  standard  permanganate  according  to 
the  usual  procedure  for  determination  of  lime. 

•  Z.  anorg.  Chem.,  70  ,  173  (1911);  Chem.  Ate.,  5,  2049  (1911). 

4  One  hundred  grams  H2O  at  18°  C.  dissolves  0.0325  gram  PbFCl  and  0.1081 
gram  at  100°  C. 


182 


FLUORINE 


VOLUMETRIC   METHODS   FOR  THE   DETERMINATION 
OF   FLUORINE 

Volumetric  Determination  of  Fluorine — Formation  of  Silicon 
Tetrafluoride  and  Absorption  of  the  Evolved  Gas  in  Water. 
Offerman's  Method  l 

Silicon  tetrafluoride  is  formed  by  the  action  of  sulphuric  acid  upon  a  fluoride 
in  presence  of  silica,  the  evolved  gas  is  received  in  water  and  the  resulting  com- 
pound titrated  with  standard  potassium  hydroxide.  The  following  reactions 
take  place: 

A.  3SiF4+2H20=2H2SiF6+Si02. 

B.  H2SiF6+6KOH  =6KF+Si02+4H20. 

The  method  is  suitable  for  determining  fluorine  in  fluorspar  in  evaluation 
of  this  mineral. 

Procedure.  The  powdered  sample,  containing  the  equivalent  of  0.1-0.2 
gram  calcium  fluoride,  is  mixed  with  about  three  times  its  weight  of  pulverized 
quartz  (previously  ignited  and  kept  in  a  desiccator),  placed  in  the  decom- 
position flask  F,  shown  in  Fig.  36,  and  about  1  gram  of  anhydrous  copper  sulphate 


Air 


FIG.  36. 

added,  followed  by  25  cc.  of  concentrated  sulphuric  acid.  The  stopcock  E 
is  closed  and  the  air  bath  heated  gradually  till  in  one-half  hour  the  temperature 
has  risen  to  220°.  The  cock  E  is  now  opened  and  air  slowly  forced  through  the 
apparatus  (by  means  of  water  pump)  at  the  rate  of  about  three  bubbles  per 
second,  the  temperature  being  kept  at  220°,  and  the  flask  containing  the  sample 
occasionally  shaken.  When  the  bubbles  of  silicon  tetrafluoride  have  disappeared 
from  F,  the  flame  is  removed,  but  the  air  current  continued  for  hah7  an  hour 
longer.  The  solution  in  the  receiving  flask  is  now  titrated  with  0.1  N.  KOH. 

NOTES.  The  apparatus  shown  in  the  cut  is  the  form  recommended  by  Adolph, 
and  the  details  of  procedure  are  essentially  his.  This  method  is  preferred  to  that 
of  Penfield,2  in  which  an  alcoholic  solution  of  potassium  chloride  is  used  to  absorb 
the  tetrafluoride,  and  the  liberated  hydrochloric  acid  titrated  with  the  standard 
alkali  in  presence  of  cochineal  indicator. 

The  results  obtained  by  this  method  are  generally  low,  but  the  procedure  is  use- 
ful for  rapid  valuation  of  fluorspar. 

1Z.  angew.  Chem.,  3,  615  (1890).  Wm.  H.  Adolph,  Jour.  Am.  Chem.  Soc., 
37,  11,  2500  (1915). 

«  Am.  Chem.  Jour.,  1,  27  (1879). 


FLUORINE  183 

The  bottles  A,  B,  C,  and  D  are  for  the  purpose  of  thoroughly  drying  the  air,  as 
moisture  in  the  apparatus  is  to  be  avoided.  G  contains  strong  sulphuric  acid,  H 
is  filled  with  glass  beads  to  remove  sulphuric  acid  spray,  7  and  J  are  empty  tubes, 
which  should  be  thoroughly  dry.  The  gas  is  completely  absorbed  in  K. 

Volumetric  Determination  of  Fluorine — Ferric  Chloride  Method 1 

The  procedure,  worked  out  by  Greef,  depends  upon  the  principle  that 
a  neutral  aqueous  solution  of  ferric  chloride  forms  a  white  crystalline  precipi- 
tate with  neutral  solutions  of  alkali  fluorides,  the  following  reaction  taking  place : 

6NaF+FeCl3  =Na3(FeF6)+3NaCl. 

The  double  fluoride  is  only  very  slightly  soluble  in  water  and  does  not  form  the 
red  compound  Fe(CNS)3  with  sulphocyanates.  The  addition  of  sodium  chloride 
makes  the  precipitation  more  complete. 

Procedure,  Half  a  gram  sample  of  the  sodium  or  potassium  salt  is  placed 
in  a  300-cc.  Erlenmeyer  flask,  and  dissolved  in  about  25  Cc.  of  hot  water, 
then  cooled  and  20  grams  of  sodium  chloride  and  5  cc.  of  potassium  sulpho- 
cyanate  added  (100  grams  KCNS  per  500  cc.  H20).  The  solution  is  titrated 
with  a  standard  solution  of  ferric  chloride  (of  such  strength  that  100  cc.  is 
equivalent  to  about  1  gram  of  NaF)  until  a  yellow  color  is  produced.  Ten  cc. 
of  alcohol  and  10  cc.  of  ether  are  now  added  and  the  mixture  shaken  gently, 
then  the  flask  closed  and  shaken  vigorously.  The  titration  is  now  continued 
until  the  ether  layer  is  permanently  colored  red. 

NOTE.  Commercial  sodium  fluoride  frequently  contains  free  hydrofluoric  acid 
and  silico-fluoride.  These  are  converted  to  the  fluoride  of  sodium  by  titration  with 
sodium  hydroxide  in  presence  of  phenolphthalein  to  neutral  reaction;  the  total  fluoride 
may  now  be  determined  as  described. 

The  free  acid  may  be  determined  by  titrating  the  salt  in  an  aqueous  alcoholic  solu- 
tion in  presence  of  potassium  chloride,  which  converts  the  silico-fluoride  to  the  in- 
soluble potassium  silico-fluoride. 

Colorimetric  Determination  of  Fluorine— Method  of  Steiger2 

and  Merwin  3 

The  method  is  based  on  the  bleaching  action  of  fluorine  upon  the  yellow 
color  produced  by  oxidizing  a  solution  of  titanium  with  hydrogen  peroxide. 
A  known  amount  of  titanium  in  solution  is  mixed  with  definite  volume  of  the 
solution  containing  the  fluorine  and  the  tint  compared  with  a  standard  solution 
containing  an  equivalent  amount  of  titanium.  The  extent  of  bleaching  enables 
the  computation  of  the  fluorine  present.  The  method  is  applicable  to  deter- 
mination of  fluorine  in  amounts  ranging  from  0.00005  to  0.01  gram.  Merwin 
has  shown  that  large  amounts  of  alkali  sulphates  have  a  bleaching  action 
similar  to  fluorine.  Addition  of  free  acid,  or  rise  of  temperature,  intensifies 
the  color  lost  by  bleaching.  Aluminum  sulphate  has  no  marked  effect  on  standard 
solutions,  or  on  solutions  bleached  by  alkali  sulphates,  but  it  restores  the  color 
to  a  considerable  degree  to  solutions  bleached  by  fluorine.  Ferric  sulphate  has 
a  similar  effect.  Phosphoric  acid  bleaches  a  standard  solution.  Silica  has  little 

1  Method  by  A.  Greef,  Analyst,  1913,  p.  521.     C.  N.,  7,  3939  (1913). 

2  G.  Steiger,  Jour.  Am.  Chem.  Soc.,  30,  219, 1908. 

'H.  E.  Merwin,  Am.  Jour.  Sci.  (4),  28,  119,  1909.  Chem.  Abs.,  3  2919  (1909). 
J,  W,  Millor,  "  A  Treatise  on  Quantitative  Inorganic  Analysis."  Chas.  Griffin  &  Co. 


184  FLUORINE 

effect.  According  to  Merwin  an  accuracy  of  0.002  gram  may  be  expected,  an 
error  which  is  half  that  of  the  most  reliable  gravimetric  method. 

Reagents.  Standard  Titanium  Solution.  An  intimate  mixture  of  1  gram 
of  Ti02  and  3  grams  of  ammonium  persulphate  is  heated  until  the  vigorous 
action  has  ceased,  and  the  ammonium  sulphate  is  expelled.  The  residue  is  treated 
with  20  cc.  of  strong  sulphuric  acid,  heated  to  fuming  and,  when  cold,  poured 
into  about  800  cc.  of  cold  water.  When  the  suspended  salt  has  dissolved, 
57.5  cc.  of  strong  sulphuric  acid  are  added,  and  the  solution  made  up  to  1000 
cc.  (50  cc.  or  more  of  the  solution  should  be  analyzed  for  Ti02).  One  cc.  mil 
contain  0.001  gram  Ti02. 

Standard  Fluorine  Solution.  2.21  grams  of  sodium  fluoride,  which  has  been 
purified  by  recrystallizing,  washing,  and  igniting  strongly,  is  dissolved  in  1000 
cc.  of  water.  One  cc.  will  contain  0.001  gram  fluorine. 

Sulphuric  Acid.     95.5%  solution,  sp.gr.,  1.84. 

Hydrogen  Peroxide.     Ordinary  strength. 

Standard  Colored  Solution.  The  solution  used  in  determining  fluorine  in 
materials  fused  with  alkali  carbonates  contains  10  cc.  of  the  titanium  solution, 
4  cc.  of  hydrogen  peroxide,  and  4  cc.  of  concentrated  sulphuric  acid. 

Apparatus.  Nessler  Tubes  6  cm.  long,  2.7  cc.  in  diameter  are  recommended 
by  the  authors.  Colorimeters  may  be  used  in  place  of  Nessler  tubes.  A  very 
suitable  type  for  this  purpose  is  shown  on  page  245,  Fig.  43. 

Procedure.  Two  grams  of  the  powdered  sample  are  fused  with  8  grams 
of  mixed  sodium  and  potassium  carbonates,  the  fusion  taken  up  with  hot  water, 
and  when  leached,  3  to  4  grams  of  ammonium  carbonate  added.  The  mix  is 
warmed  for  a  few  minutes  and  then  heated  on  the  water  bath  till  the  ammonium 
carbonate  is  decomposed  and  the  bulk  of  liquid  is  small.  Silica,  ferric  oxide, 
and  alumina  oxide  are  thrown  down  and  are  removed  by  filtration.  The  filtrate, 
which  should  not  exceed  75  cc.,  is  treated  with  4  cc.  of  hydrogen  peroxide,  and 
then  10  cc.  of  standard  titanium  solution  cautiously  added  (H2O2  prevents 
precipitation  of  Ti02  by  the  alkali  carbonates),  followed  by  4  cc.  of  strong  sulphuric 
acid  to  neutralize  the  alkali  carbonates.  The  solution,  neutral  or  slightly  acid, 
acquires  a  light  orange  tint.  A  little  sodium  carbonate  is  added  in  just  suf- 
ficient amount  to  discharge  the  color,  and  then  a  drop  or  so  of  acid  to  again 
restore  it.  The  amount  of  excess  acid  now  required  depends  upon  the  amount 
of  fluorine  present  in  the  solution.  For  amounts  of  fluorine  less  than  0.0025 
gram  (0.125%  of  sample),  3  cc.  of  acid  are  added.  For  amounts  of  0.0025  to 
0.012  gram  fluorine,  12  cc.  of  acid  are  added.  The  solution  is  diluted  to  100  cc. 

Comparison.  The  test  solution  is  now  compared  with  the  standard  solu- 
tion containing  10  cc.  titanium  reagent,  and  the  same  amount  of  acid  and 
hydrogen  peroxide  as  in  the  test  sample,  in  a  volume  of  100  cc.  If  Nessler  tubes 
are  used,  these  are  held  over  a  white  surface  illuminated  with  diffused  light. 
In  the  absence  of  a  bleaching  substance,  such  as  fluorine,  the  two  solutions  will 
have  the  same  tint,  but  in  presence  of  fluorine  the  bleaching  effect  will  cause 
the  test  solution  to  appear  paler  than  the  standard.  The  depths  of  the  liquids 
are  adjusted  so  that  the  tubes  will  have  the  same  intensity  of  color  when  moved 
from  right  to  left  or  reversed.  Should  the  left  eye  perceive  a  darker  shade,  the 
tube  on  the  left  will  appear  uniformly  darker  whether  it  be  the  test  sample  or 
the  standard.  The  comparative  depths  of  the  liquids  in  the  tubes  are  measured 
and  the  ratio  obtained  by  dividing  the  depth  of  the  fluorine  solution  by  the 
depth  of  the  standard  and  multiplying  by  100.  Reference  may  be  made  to  the 


FLUORINE 


185 


plotted    curve  shown  in  Fig.  37.    The    ratio   — — -J — £— — ^—X 100=  the 

Depth  of  Standard 


v 

s 

\ 

s 

00020 

^ 

s 

\ 

\ 

z 

\ 

tt    000  IS 

\ 

\ 

3 

X 

Li. 

X 

O 

\ 

52  oon  in 

\ 

< 

v 

o: 

^ 

o 

s,, 

V 

,. 

noons 

V 

«^ 

•> 

** 

•x 

•^ 

!*» 

•V. 

0 

—  ^- 

•*. 

aL 

65  70  75  80  85 

APPARENT  PERCENTAGE  OF  TiOi 

FIG.  37. 


too. 


abscissa,  while  the  ordinate  represents  the  amount  of  fluorine  in  the  2-gram 
sample. 

Example.    Suppose  the  test  solution  =3.6  cm.  and  the  standard  =4.5  cm., 


0.0040 


140  160  I 

RATIO  OF  DEPTHS  OF  COLOR 

FIG.  38. 


the  ratio  then  =80,  from  the  curve  it  is  evident  that  the  fluorine  =0.00095  gram 
or  0.0475%,  since  a  2-gram  sample  was  taken. 


186  FLUORINE 

According  to  Merwin,  however,  the  bleaching  effect  of  alkali  sulphates,  which 
are  present,  will  make  the  ratio  much  higher  than  it  would  be  if  they  were 
absent.  (The  sulphates  alone  give  a  ratio  of  125.)  This  ratio  should  be  deter- 
mined on  two  8-gram  portions  of  the  alkali  carbonate  mixture  used  in  the  fusion 
and  the  correction  made  accordingly.  If  m=  ratio  of  the  blank  thus  obtained, 
and  r  the  ratio  of  the  final  test,  then  the  formula,  according  to  Merwin,  is 

— — —  =gram  fluorine  in  the  sample,  4  cc.  excess  sulphuric  acid  being  used 
^o,UUU 

in  the  samples,  or  —  =  grams  F,  if  12  cc.  of  acid  are  used  in  testing  larger 

uoOO 

amounts  of  fluorine.  The  plotted  curve,  Fig.  38,  is  that  given  by  Merwin, 
and  shows  the  effect  of  acidity  on  the  depth  of  color  obtained.  The  abscissa 
represents  the  ratio  of  the  solutions,  and  the  ordinate  the  amount  of  fluorine 
in  grams.  Temperature  of  the  tests  was  22°  C. 

VALUATION  OF  FLUORSPAR 

The  following  procedure,  worked  out  by  Dr.  Bidtel,1  meets  the  commercial 
requirements  for  the  valuation  of  fluorspar.  The  determinations  usually  required 
are  calcium  fluoride,  silica,  and  calcium  carbonate;  in  some  particular  cases 
lead,  iron,  zinc,  and  sulphur. 

Procedure.  Calcium  Carbonate.  One  gram  of  the  finely  powdered  sample 
is  placed  in  a  small  Erlenmeyer  flask,  10  cc.  of  10%  acetic  acid  are  added,  a 
short-stemmed  funnel  inserted  in  the  neck  of  the  flask  as  a  splash  trap,  and 
the  mixture  heated  for  an  hour  on  a  water  bath,  agitating  from  time  to  time. 
The  calcium  carbonate  is  decomposed  and  may  be  dissolved  out  as  the  soluble 
acetate,  whereas  the  fluoride  and  silica  are  practically  unaffected.  The  solution 
is  filtered  through  a  7-cm.  ashless  filter,  the  residue  washed  with  warm  water 
four  times,  and  the  filter  burned  off  in  a  weighed  platinum  crucible  at  as  low 
a  temperature  as  possible.  The  loss  of  weight  minus  0.0015  gram  (the  amount 
of  calcium  fluoride  soluble  in  acetic  acid  under  the  conditions  named)  is  reported 
as  calcium  carbonate, 

Silica.  The  residue  in  the  platinum  crucible  is  mixed  with  about  1  gram 
of  yellow  mercuric  oxide,  in  form  of  emulsion  in  water  (to  oxidize  any  sulphide 
that  may  be  present);  any  hard  lumps  that  may  have  formed  are  broken  up, 
the  mixture  evaporated  to  dryness  and  heated  to  dull  redness,  then  cooled 
and  weighed.  About  2  cc.  of  hydrofluoric  acid  are  added  and  the  mixture 
evaporated  to  dryness.  This  is  repeated  twice  to  ensure  complete  expulsion 
of  silica  (as  SiF4).  A  few  drops  of  hydrofluoric  acid  are  then  added,  together 
with  some  macerated  filter  paper,  and  a  few  drops  of  ammonium  hydroxide  to 
precipitate  the  iron.  The  solution  is  evaporated  to  dryness,  heated  to  dull 
redness,  cooled  and  weighed.  The  loss  of  weight  is  reported  as  silica. 

Calcium  Fluoride.  The  residue  is  treated  with  2  cc.  of  hydrofluoric  acid 
and  10  drops  of  nitric  acid  (to  decompose  the  oxides),  the  crucible  covered  and 
placed  on  a  moderately  warm  water  bath  for  thirty  minutes,  the  lid  then 
removed  and  the  sample  taken  to  dryness.  The  evaporation  with  hydrofluoric 
acid  is  repeated  to  ensure  the  transposition  of  the  nitrates  to  fluorides,  and  if 

1  Dr.  E.  Bidtel,  Chemist,  Fairview  Fluorspar  and  Lead  Company,  Jour.  Tnd.  Eng. 
Chem.,  Vol.  4,  No.  3,  March,  1912. 


FLUORINE  187 

the  residue  is  still  colored,  hydrofluoric  acid  again  added  and  the  mixture  taken 
to  dryness  a  third  time;  then  a  few  drops  of  hydrofluoric  acid  are  added  and 
10  cc.  of  ammonium  acetate  solution  (the  acetate  solution  is  made  by  neutral- 
izing 400  cc.  of  80%  acetic  acid  with  strong  ammonia,  adding  20  grams  of  citric 
acid  and  making  the  mixture  up  to  1000  cc.  with  strong  ammonium  hydroxide). 
The  mixture  is  digested  for  thirty  minutes  on  a  boiling  water  bath,  then  filtered 
and  washed  with  hot  water  containing  a  small  amount  of  ammonium  acetate, 
and  finally  with  pure  hot  water.  (Several  washings  by  decantation  are  advis- 
able.) The  residue  is  ignited  in  the  same  crucible  and  weighed  as  calcium  fluoride. 
An  addition  of  0.0022  gram  should  be  made  to  compensate  for  loss  of  CaF2. 

Pure  calcium  fluoride  is  white.  To  test  the  purity  of  the  residue,  2  cc.  of 
sulphuric  acid  are  added  and  the  material  taken  to  fumes  to  decompose  the 
fluoride;  1  cc.  of  additional  sulphuric  acid  is  added  and  the  excess  of  acid 
expelled  by  heating.  The  residue  is  weighed  as  calcium  sulphate.  This  is  now 
fused  with  sodium  carbonate,  and  the  fusion  treated  witfi  hydrochloric  acid 
in  excess.  If  barium  is  present  the  solution  will  be  cloudy  ( =*BaS04.) 

ANALYSIS  OF  SODIUM   FLUORIDE 

Preparation  of  the  Sample  and  Insoluble  Residue.  Ten  grams  of  the 
sample  are  dissolved  in  250  cc.  of  water  in  a  beaker,  and  boiled  for  five  minutes, 
then  filtered  into  a  liter  flask  through  an  ashless  filter;  the  residue  is  washed  with 
several  portions  of  water  and  ignited.  This  is  weighed  as  insoluble  residue. 
The  filtrate  and  washings  are  made  to  1000  cc.  with  distilled  water. 

Sodium  Fluoride.  Fifty  cc.  of  the  solution  equivalent  to  0.5  gram  of 
sample  are  diluted  to  200  cc.  in  a  beaker,  0.5  gram  sodium  carbonate  is  added 
and  the  mixture  boiled.  An  excess  of  calcium  chloride  solution  is  now  added 
slowly  and  boiled  for  about  five  minutes.  A  small  amount  of  paper  pulp  is 
added  to  prevent  the  precipitate  from  running  through  the  filter,  the  precipitate 
allowed  to  settle  and  then  filtered,  using  a  9-cm.  S.  &  S.  590,  or  B.  &  A. 
grade  A,  filter  paper.  The  fluoride  is  washed  twice  by  decantation,  and  four 
or  five  times  on  the  filter  with  small  portions  of  hot  water.  The  final  washings 
should  be  practically  free  of  chlorine. 

The  residue  is  ignited  in  a  platinum  dish,  then  treated  with  25  cc.  of  acetic 
acid,  and  taken  to  dryness.  This  treatment  is  repeated  and  the  residue  taken 
up  with  a  little  hot  water  and  filtered.  The  calcium  fluoride  is  washed  free  of 
calcium  acetate  with  small  portions  of  water,  remembering  that  CaF2  is  slightly 
soluble  in  water.  The  ignited  residue  is  weighed  as  CaF2. 

CaF2Xl.0757=NaF. 

Sodium  Sulphate.  To  the  filtrate  from  calcium  fluoride  is  added  10  cc. 
hydrochloric  acid  and  then  a  hot  solution  of  barium  chloride.  The  BaS04  is 
allowed  to  settle,  filtered,  washed,  dried,  ignited,  and  weighed  as  usual. 

BaS04X0.6086=Na2S04. 

Sodium  Carbonate.  Sodium  carbonate  is  determined  on  a  5-gram  sample 
by  the  usual  method  for  carbon  dioxide  as  described  in  the  chapter  on  Carbon. 

Approximate  results  may  be  obtained  by  adding  a  small  excess  of  normal 
sulphuric  acid  to  5  grams  of  the  fluoride  in  a  platinum  dish,  boiling  off  the  carbon 


188  FLUORINE 

dioxide,  and  titrating  the  excess  of  acid  with  normal  caustic,  using  phenolphthalein 
indicator. 

One  cc.  N.  H2S04  =0.053  gram  Na2C03. 

H2S04X  1.0816  =Na2C03. 

Sodium  Chloride.  Fifty  cc.  of  the  sample  is  titrated  with  N/10  AgN03 
solution. 

Silica.  This  is  probably  present  as  sodium  fluoride  and  silicate.  One  gram 
of  the  sample  is  dissolved  in  the  least  amount  of  water  and  a  small  excess  of 
hydrofluoric  acid  added  to  convert  the  silicate  to  silico-fluoride,  then  an  equal 
volume  of  alcohol.  After  allowing  to  stand  for  an  hour,  the  precipitate  is  filtered, 
washed  with  50%  alcohol  until  free  of  acid  and  the  filter  and  fluoride  are  placed 
in  a  beaker  with  100  cc.  of  water,  boiled  and  titrated  with  N/10  NaOH. 

One  cc.  N/lONaOH  =0.0015  gram  Si02  or  0.0047  gram  Na2SiF6. 

Volatile  Matter  and  Moisture.  One-gram  sample  is  heated  to  dull  redness 
to  constant  weight.  Loss  of  weight  is  due  to  moisture  and  volatile  products. 


DETERMINATION   OF  TRACES   OF   FLUORINE 

An  approximate  estimation  of  traces  of  fluorine  may  be  made  by  utilizing 
the  method  outlined  for  detection  of  this  element.  The  apparatus  l  is  the 
same,  with  the  exception  that  the  crucible  rests  in  a  paraffine  2  bath  containing 
a  thermometer  to  regulate  the  temperature.  A  casserole  may  be  used  to  hold 
the  paraffine.  By  varying  the  amounts  of  substance  tested  an  etch  is  obtained 
that  is  comparable  with  one  of  a  set  of  standard  etches,  obtained  with  known 
amounts  of  fluorine  in  form  of  calcium  fluoride,  added  to  the  same  class  of  material 
examined. 

The  conditions  in  obtaining  the  standard  etches  and  those  of  the  tests  should 
be  the  same.  This  applies  to  the  temperature  of  the  paraffine  bath,  duration 
of  the  run,  size  of  mark  exposing  the  surface  of  the  test-plate,  and  the  general 
mode  of  procedure. 

NOTE.  The  importance  of  regulating  the  temperature  may  be  seen  by  the  results 
obtained  by  Woodman  and  Talbot.  With  a  temperature  of  79^82°  C.,  one  part 
of  fluorine  may  be  detected  in  25  to  100  thousand  parts  of  material;  by  raising  the 
temperature  to  136°  C.,  the  delicacy  of  the  procedure  is  increased  to  one  part  of 
fluorine  in  1  to  5  million  parts.  The  limit  of  delicacy  is  apparently  reached  at  213-218° 
C.  (i.e.,  1  part  F  per  25  million). 

1  A  metal  condenser,  such  as  is  recommended  for  mercury  determinations,  may 
be  used  and  the  paraffine  bath  substituted  by  an  electric  heater  automatically  con- 
trolled. 

2  Crisco  is  claimed  to  be  better  than  paraffine,  as  this  does  not  give  off  any  un- 
pleasant fumes  when  heated. 


GLUGINUM   (BERYLLIUM) 

W.  W.  SCOTT. 
Gl,  at.wt.  9.1;  sp.gr.  1.85200;    mp.  >  960°  C.;   oxide,  G1O. 

DETECTION 

In  the  usual  course  of  analysis  glucinum  will  be  precipitated  by  ammonia  along 
with  iron  and  aluminum  hydroxides.  Silica  having  been  removed  by  evaporation 
to  dryness  of  the  acid  solution  of  the  substance,  extraction  of  the  residue  with 
dilute  hydrochloric  acid  and  subsequent  filtration;  the  members  of  the  hydrogen 
sulphide  group  are  precipitated  from  slightly  acid  solution  by  hydrogen  sul- 
phide. The  filtrate  is  concentrated  to  about  30  cc.,  and  about  2  grams  of  sodium 
peroxide  are  added  to  the  cooled  liquid,  which  is  now  heated  to  boiling  and 
filtered.  Fe(OH)3  remains  insoluble,  if  iron  is  present,  while  aluminum  and 
glucinum  dissolve.  The  filtrate  is  acidified  with  nitric  acid,  and  ammonia  then 
added  in  excess.  If  a  precipitate  forms,  alumina  or  glucinum  or  both  are  indi- 
cated. Glucinum  hydroxide  and  aluminum  hydroxide  cannot  be  distinguished 
by  appearance;  the  solubility  of  the  former  in  sodium  bicarbonate  solution  makes 
it  possible  to  separate  the  two.  The  precipitate  is  dissolved  in  acid  and  the 
solution  made  almost  neutral  with  ammonia.  Solid  sodium  bicarbonate  is  added 
in  sufficient  amount  to  make  the  solution  contain  10%  of  the  reagent  and  the 
mixture  heated  to  boiling,  then  filtered.  Alumina  hydroxide  remains  on  the  filter 
paper  and  glucinum  passes  into  the  filtrate,  in  which  it  may  be  detected  by 
diluting  to  ten  volumes  with  water  and  boiling,  whereupon  glucinum  hydroxide 
precipitates. 

Glucinum  hydroxide,  G1(OH)2,  is  precipitated  from  neutral  or  acid  solu- 
tion by  ammonia,  insoluble  in  excess  (distinction  from  A1(OH)3).  It  is  pre- 
cipitated by  sodium  and  potassium  hydroxides,  soluble  in  excess  (separation 
from  iron);  if  this  solution  is  boiled  G1(OH)2  is  repiecipitated,  A1(OH)3  remains 
in  solution.  G1(OH)2  is  soluble  in  an  excess  of  ammonium  carbonate,  Al  (OH), 3 
is  insoluble. 

ESTIMATION 

Glucinum  occurs  in  the  minerals  beryl,  euclase,  davalite,  chrysoberyl,  helvite, 
leucophane,  phencaite. 

The  oxide,  G10,  is  soluble  in  strong  sulphuric  acid.  It  is  decomposed  by 
fusion  with  potassium  fluoride.  The  freshly  precipitated  hydroxide,  G1(OH)2, 
is  easily  soluble  in  dilute  acids,  in  alkalies  and  alkali  carbonates  and  bicar- 
bonates. 

The  methods  of  preparation  and  solution  of  the  sample  are  the  same  as 
those  described  for  the  estimation  of  aluminum.  For  details  of  these  procedures 
the  analyst  is  referred  to  the  chapter  on  this  element. 

189 


190  GLUCINUM   (BERYLLIUM) 

SEPARATIONS 

Removal  of  Silica  and  Members  of  the  Hydrogen  Sulphide  Group.  See 
proceduie  given  under  "Detection." 

Separation  of  Glucinum  from  Iron  and  Manganese.  The  acid  solution 
is  nearly  neutralized  with  ammonia  and  then  poured  with  constant  stirring  into 
an  excess  of  a  cold  mixture  of  ammonium  sulphide  and  carbonate.  Iron  and 
manganese  are  precipitated,  whereas  glucinum  passes  into  the  filtrate.  (Zir- 
conium and  yttrium  will  be  found  with  glucinum,  if  they  are  present  in  the 
material  examined.) 

Separation  from  Zirconium  and  Yttrium.  The  filtrate  obtained  from 
the  separation  of  iron  and  manganese  is  boiled  for  an  hour,  the  precipitate 
is  filtered  and  washed,  then  dissolved  in  dilute  hydrochloric  acid.  To  this 
solution  is  added  an  excess  of  sodium  hydroxide,  zirconium  and  yttrium  are  pre- 
cipitated, whereas  glucinum  remains  in  solution.  After  filtering,  glucinum 
may  be  precipitated  by  boiling  the  diluted  filtrate. 

Separation  from  Aluminum,  Chromium  and  Iron.  The  elements  precip- 
itated as  hydroxides  are  ignited  to  oxides  and  fused  with  sodium  carbonate 
for  an  hour  or  more.  Upon  leaching  with  water,  aluminum  and  chromium  dis- 
solve, while  iron  and  glucinum  remain  insoluble.  The  oxides  of  glucinum  and 
iron  may  be  separated  by  fusion  with  sodium  acid  sulphate,  extracting  with  water 
and  precipitating  the  iron  with  an  excess  of  sodium  hydroxide,  glucinum  re- 
maining in  solution. 

Separation  of  Glucinum  from  Aluminum.  The  hydroxides  of  alumina 
and  glucinum  are  precipitated  with  ammonia  and  the  precipitate  treated  with 
an  excess  of  ammonium  carbonate.  G1(OH)2  dissolves,  whereas  A1(OH)3  re- 
mains insoluble.  See  Detection,  also  Gravimetric  Method  for  Determination 
of  Glucinum. 


GRAVIMETRIC  DETERMINATION  OF  QLUCINUM 

The  procedure  recommended  by  Parsons  and  Barnes  l  depends  upon  the 
solubility  of  glucinum  hydroxide  in  a  10%  sodium  bicarbonate  solution,  in  the 
separation  of  this  element  from  iron  and  aluminum  hydroxide  precipitate,  with 
which  it  is  commonly  thrown  out  from  solution.  (Uranium,  if  present,  also 
dissolves.) 

Procedure.  Silica  and  the  members  of  the  hydrogen  sulphide  group  having 
been  removed  by  the  usual  methods  (See  Detection),  hydrogen  sulphide  is 
expelled  by  boiling,  nitric  acid  is  added  in  sufficient  amount  to  oxidize  iron 
(the  hydrochloric  acid  solution  turns  yellow)  and  ammonium  hydroxide  added 
in  slight  excess.  The  precipitated  hydroxides  are  allowed  to  coagulate  by  heating 
to  boiling  and,  after  settling  a  few  minutes,  filtered  and  washed  with  a  2% 
solution  of  ammonium  acetate  containing  free  ammonia. 

Separation  from  Iron  and  Aluminum  Hydroxide.  The  precipitate  is 
dissolved  in  hydrochloric  acid,  the  solution  oxidized  with  nitric  acid  or  hydro- 
gen peroxide  (C.P.),  if  necessary,  and  the  free  acid  then  neutralized  with  ammonia. 
To  the  cold  solution  are  added  10  grams  of  sodium  bicarbonate  for  each  100  cc. 

JC.  L.  Parsons  and  S.  K.  Barnes,  Jour.  Am.  Chem.  Soc.,  28,  1589,  1906. 


GLUCINUM   (BERYLLIUM)  191 

of  liquid.  The  mixture  is  heated  to  boiling  and  boiled  for  one  minute,1  then 
cooled  and  filtered.  The  residue  is  washed  with  hot  10%  solution  of  sodium 
bicarbonate.  Iron  and  aluminum  hydroxides  remain  on  the  filter  and  gluci- 
num  passes  into  the  filtrate. 

To  recover  occluded  glucinum  from  the  hydroxides  of  iron  and  alumina, 
the  precipitate  is  dissolved  in  a  few  drops  of  hydrochloric  acid,  and  the  pre- 
cipitation repeated.  It  is  advisable  to  repeat  this  treatment  a  third  time, 
adding  the  nitrates  to  the  first  portion  containing  the  glucinum. 

Precipitation  of  Glucinum.  The  combined  filtrates  from  the  alumina  and 
iron  hydroxides  are  acidified  with  strong  hydrochloric  acid,  the  beakers  covered 
to  prevent  loss  by  spurting  and  the  carbon  dioxide  completely  removed  by 
boiling.  (C02  remaining  in  solution  would  form  ammonium  carbonate,  on  sub- 
sequent treatment  with  ammonia,  which  would  dissolve  glucinum.)  A  slight 
excess  of  ammonia  is  now  added,  the  mixture  again  boiled  and  the  precipitated 
glucinum  hydroxide  allowed  to  settle,  then  filtered  and  washed  with  a  2%  solu- 
tion of  ammonium  acetate  containing  free  ammonia,  until  the  chlorides  are  removed. 
After  ignition  the  residue  is  weighed  as  glucinum  oxide,  G10. 

G10X  0.3626  =G1. 

Prolonged  boiling  would  cause  the  loss  of  too  much  CO2,  so  that  A1(OH)3  would 
be  apt  to  pass  into  solution.  The  evolution  of  CO2  may  be  mistaken  for  boiling. 


GOLD 

W.  G.  DERBY 
Au,  at.wt.  197.2;  sp.^r.  19.33;  m.p.  1063;  b.p.  2530°  C;  oxides,  Au2O,  Au2O3 

DETECTION 

Because  of  the  limited  application  and  tediousness  of  wet  methods,  the 
detection  of  a  small  quantity  (2  parts  per  million  or  less)  of  gold  in  a  mineral  or 
base  met  1  is  most  positively  carried  out  by  furnace  melhods  of  assaying. 
Wet  methods  of  detection  of  traces  of  gold  can  be  applied  only  to  solutions  free  of 
colored  salts  and  elements  precipitated  by  the  reagents  employed.  As  a  rule, 
in  the  treatment  of  an  unknown  substance,  advantage  is  taken  of  the  solubility 
of  most  metals  and  their  compounds,  and  insolubility  of  gold  by  one  of  the  mineral 
acids. 

Detection  of  Gold  in  Alloys.  In  metals  or  alloys  which  produce  colorless 
solutions  with  dilute  nitric  acid,  gold,  in  the  absence  of  other  insoluble  matter, 
exhibits  itself  as  a  black  or  brownish  residue  which  settles  readily,  and  from  which 
the  liquid  can  be  separated  by  careful  decantation.  If  unassociated  with  metals 
of  the  platinum  group,  this  residue  will  become  yellowish  brown  on  heating  with 
strong  nitric  acid. 

In  copper,  nickel  and  such  alloys,  which  leave  a  residue  of  sulphur,  carbon  or 
silicious  matter  on  treatment  with  dilute  nitric  acid,  the  solution  is  filtered  through 
double  ashless  filters  and  the  filter  and  residue  incinerated  in  a  porcelain  crucible. 
The  residue,  which  may  require  pulverizing,  is  digested  for  a  few  minutes  with 
aqua  regia,  and  the  dilute,  filtered  solution  evaporated  to  dryness  by  heating 
below  200°  F.  Just  as  soon  as  dry,  the  mass  is  moistened  with  the  least  quantity 
of  hydrochloric  acid  and  the  purple  of  Cassius  test  applied  to  its  water  solution 
in  a  small  volume.  This  test  is  made  by  adding  a  solution  of  stannous  chloride, 
containing  stannic  chloride.  In  strongly  acid  and  concentrated  gold  solu- 
tions a  precipitate  of  brown  metallic  gold  is  obtained.  If  the  solution  is  but 
slightly  acid  and  dilute,  a  reddish  purple  color  is  produced  by  colloidal  gold  and 
the  stannic  acid.  The  tint  fades  on  standing.  Addition  of  ammonia  produces 
a  red  coloration. 

This  test  applied  to  1  part  of  gold  in  600,000  of  solution  will  impart  a  per- 
ceptible shade;  to  double  this  quantity,  a  mauve  color.  When  gold  is  present  in 
somewhat  greater  proportion  a  flocculent  precipitate  will  form. 

Test  for  Gold  in  Minerals.  From  minerals,  in  which  the  metal  exists  in  unal- 
loyed, or  uncombined  state,  gold  may  be  extracted  by  iodine  in  potassium  iodide 
solution,  or  by  chlorine  or  bromine  water.  All  minerals  containing  sulphides 
should  be  roasted.  In  natural  or  roasted  state  the  sample  should  be  ve  y  finely 
pulverized,  and  usually  yields  the  gold  best  if  first  digested  with  nitric  acid  and 
washed  free  of  soluble  salts.  The  sample  in  a  flask  is  covered  with  bromine 
water,  the  flask  closed  with  a  plug  and  shaken  frequently  during  a  period  of  three 

192 


GOLD  193 

or  four  hours.  The  purple  of  Cassius  test  is  applied  to  the  extract,  removed  by 
decantation  after  con  entration. 

If  it  is  evident  that  base  metals  are  present  in  the  bromine  water  extract  in 
quantity^  sufficient  to  mask  the  purple  of  Cassius  test,  hydrogen  peroxide  is  added 
to  the  concentrated  liquid,  slightly  alkaline  with  sodium  or  potassium  hydroxide 
or  carbonate.1  After  boiling  the  solution  until  hydrogen  peroxide  is  removed, 
precipitated  hydroxides  or  carbonates  are  dissolved  by  hydrochloric  acid.  Gold  in 
exceedingly  small  quantity  exhibits  itself  as  a  light-brown  residue  on  a  fine  filter. 
This  indication  should  be  confirmed  by  a  purple  of  Cassius  test  on  the  aqua  regia 
solution  of  the  residue;  the  test  carried  out  in  the  same  manner  as  on  the  residue 
from  a  solution  of  a  metal. 

Benzidine  Acetate  Tests.  Maletesta  and  Nola 2  make  use  of  benzidine  acetate 
(1  gram  benzidine  dissolved  in  10  cc.  acetic  acid  and  50  cc.  water)  as  a  reagent  in 
the  detection  of  gold  and  platinum  in  quite  dilute  solutions.  Gold  gives  a  blue 
coloration  which  gradually  changes  to  violet.  The  coloration  is  green  in  the 
presence  of  free  acetic  acid,  changing  to  blue  with  addition  of  benzidine  in  excess. 
Platinum  gives  a  blue  flocculent  precipitate,  the  formation  of  which  is  pro- 
moted by  heating.  Free  mineral  acids  have  no  influence  on  the  gold  and  retard 
the  platinum  reaction  only  in  the  cold.  Since  ferric  salts  give  a  blue  colora- 
tion, stable  only  in  excess  of  benzidine,  their  absence  must  be  assured  before 
application  of  the  test  for  the  precious  metals.  The  limit  of  sensitiveness 
of  the  test  is  35  parts  for  gold  and  125  parts  for  platinum  per  10,000,000. 

Phenylhydrazine  Acetate  Test.  E.  Pozzi  Escot 3  adds  phenylhydrazine 
acetate  to  a  very  dilute  gold  solution  which  contains  an  excess  of  an  organic  acid 
(formic  or  citric).  A  violet  coloration,  permanent  for  several  hours,  is  imparted. 
The  depth  of  color  is  proportional  to  the  quantity  when  the  gold  is  present  in  less 
amount  than  one  part  in  500,000. 

ESTIMATION 
Solubility 

Gold  in  massive  form  is  practically  insoluble  in  pure  nitric,  sulphuric  or  hydA- 
chloric  acids,  but  in  the  presence  of  oxidizing  agents,  is  attacked  appreciably  by 
sulphuric,  and  actively  by  hydrochloric  acid.  Gold  is  found  in  minute  quantity 
in  the  nitric  acid 4  solution  of  its  alloys  and  in  such  as  contain  selenium,  the 
amount  may  be  a  large  part  of  the  total  present. 

Gold  is  attacked  energetically  by  aqua  regia.  Large  amounts  of  gold  are 
dissolved  with  requirement  of  least  attention  when  the  proportion  of  hydrochloric 
acid  is  several  times  that  of  the  aqua  regia  formula,  (3HC1  :  1HN03). 

Gold  is  dissolved  by  solutions  of  chlorine  or  bromine,  by  alkaline  thiosulphates; 
in  the  presence  of  free  oxygen  by  iodine  in  potassium  iodide  solution,  by  soluble 
cyanides,  by  fused  potassium  or  sodium  hydroxide;  by  fused  potassium  or  sodium 
nitrate  or  sulphide.  In  a  finely  divided  state,  it  is  dissolved  by  a  solution  of  potas- 
sium or  sodium  hydroxide. 

Gold  alloys  quickly  with  molten  lead.  When  in  the  form  of  bright,  untarnished 
particles  it  alloys  readily  with  mercury. 

1  Vanino  and  Seeman,  Berichte,  32,  1968;  Rossler,  Zeit.  Anal.  Chem.,  49,  733. 

2  Bull.  Chim.  Farm,  52,  461;  Chem.  Abs.,  April  20,  1397,  1914. 

3  Am.  Chim.  Anal.  Appl.,  1907,  12,  90;  J.S.C.I.,  June  15,  1907,  645. 

*Dewey,  J.A.C.S.,  March,  1910,  318;  E.  Keller,  Bull.  Am.  Inst.  Min.  Eng.,  67,  681. 


194  GOLD 

GRAVIMETRIC   METHODS 

Gold  is  always  weighed  in  metallic  state,  and  is  determined  most  accurately 
in  the  form  of  the  mass  obtained  by  dilute  nitric  acid  treatment  of  the  silver 
alloy  resulting  from  the  operation  of  cupellation  in  the  method  of  assaying  by 
furnace  processes.  On  account  of  tediousness  in  making  complete  separation 
from  associated  metals,  and  of  uncertainty  in  collection  of  the  product  in  a 
form  suitable  for  accurate  weighing,  direct  precipitation  methods  are  never  used 
for  the  valuation  of  gold-bearing  material,  but  may  be  applied  to  the  estimation 
of  gold  in  plating  baths,  the  Wohlwill  parting  electrolyte  and  solutions  of  similar 
type. 

Precipitation  of  Gold.  From  such  solutions  of  auric  chloride,  slightly  acid 
with  hydrochloric,  freed  of  oxidizing  agents  by  evaporation  and  displacement  with 
hydrochloric  acid,  and  containing  but  little  of  the  salts  of  the  alkalis  or  alkali 
earths,  gold  is  separated  from  other  than  occluded  platinum  and  palladium  by 
precipitation  with  oxalic  acid,  ferrous  sulphate,  or  hydrazine  hydrochloride.  The 
reactions  are  hastened  by  heat.  When  salts  of  the  alkalis  or  earths  are  present, 
equally  good  separation  and  more  complete  precipitation  can  be  obtained 
by  addition  of  excess  of  sodium  peroxide,  boiling  vigorously  for  a  few  minutes 
and  then  acidifying  with  hydrochloric  acid.  The  precipitated  metal  is  collected 
on  an  ashless  filter  paper,  and  after  drying,  weighed. 

Gold  precipitated  from  a  very  weak  solution  is  in  such  fine  form  that  it  is  not 
wholly  retained  by  the  finest  paper. 

Wet  Gold  Assay  of  Minerals 

A  wet  gold  assay,  suitable  for  prospector's  use,1  is  carried  out  by  covering  one 
assay  ton  (29.17  grams),  of  the  finely  pulverized  natural  or  roasted  ore,  in  a  por- 
celain mortar,  with  50  cc.  of  a  solution  of  2  parts  of  iodine  and  4  parts  potassium 
iodide  in  100  cc.  of  water.  Sulphide  ores  should  be  roasted  and  digested  with 
nitric  acid  before  treatment  with  the  iodine  solution.  Similar  treatment  is 
advantageously  applied  to  all  ores.  The  ore  is  ground  in  contact  with  the  iodine 
solution  and  additions  of  the  halogen  are  made  whenever  the  liquid  becomes  color- 
less. The  solution  is  then  allowed  to  stand  at  least  an  hour.  To  the  filtrate 
and  washings  from  the  pulp,  in  a  glass-stoppered  bottle  or  flask,  are  added  5 
grams  of  gold  free  mercury.  The  liquid  is  shaken  vigorously  with  the  mercury 
until  clear.  The  mercury  is  then  transferred  to  a  small  porcelain  casserole, 
washed  with  clean  water  and  dissolved  by  warming  carefully  with  10  cc.  nitric 
acid.  The  gold  mass  is  washed  free  of  nitrate  of  mercury  by  decantation,  dried 
and  annealed  by  heating  in  a  casserole  over  a  Bunsen  flame,  and  the  metal 
weighed.  Each  milligram  represents  an  ounce  per  ton.  Results  obtained  by  this 
method  of  assaying  are  usually  more  than  50  per  cent  of  the  actual  gold  content. 

Electrolytic  Method.  The  gold  content  of  a  cyanide  plating  bath  containing 
no  potassium  ferrocyanide  may  be  estimated  by  electrolysis.2 

Procedure.  A  measured  quantity,  25  to  50  cc.  in  a  tared  platinum  dish,  is 
diluted  to  1  cm.  of  the  rim  of  the  dish  and  using  a  carbon  or  platinum  anode,  elec- 

*De  Luce,  Min.  Sci.  Press,  100,  895;  Hawson,  Min.  Sci.  Press,  100,  936;  Davis, 
Mines  and  Minerals,  Oct.,  1910,  Feb.,  1911;  Austen,  Inst.  of  Min.  and  Met.,  May 
31,  1911. 

2  Electro  Deposition  of  Metals,  Langbein. 


GOLD  195 

trolyzed  for  about  three  hours  at  a  current  density  ND100  =0.067  amp.  (.0.0043  per 
square  inch).  Completion  of  deposition  is  recognized  by  the  lack  of  any  deposit 
within  fifteen  minutes,  on  a  platinum  strip  suspended  on  the  rim  of  the  dish.  The 
dish  plus  gold  deposit  is  washed,  rinsed  with  alcohol,  dried  at  212°  and  when  cold 
weighed. 

The  following  is  a  summary  of  the  conditions  of  deposition  of  gold  in  compact 
form  as  described  by  Classen  l  3  grams  potassium  cyanide  were  added  to  a  gold  chloride 
solution  containing  0.0545  grams  of  gold  in  120  cc.  This  solution  heated  to  about  55°  C 
when  electrolyzed  at  a  current  density  of  ND100=  0.38  amp.  (0.024  amp.  per  square  inch) 
with  a  potential  difference  of  2.7-4.0  volts,  deposited  its  gold  content  in  one  and  a 
half  hours.  Time  required  for  deposition  is  tripled  if  the  electrolyte  is  at  room  tem- 
perature. 

Miller2  deposited  0.1236  gram  of  gold  in  two  and  a  quarter  hours  from  125  cc. 
of  electrolyte  at  50°  C.  containing  1  gram  potassium  cyanide  by  a  current  of  NDioo= 
0.03  amp.  (0.002  amp.  per  square  inch)  and  2.5  volts. 

Perkin  and  Preble 3  use  an  electrolyte  containing  ammonium  thiocyanate  in  place  of 
potassium  or  sodium  cyanide. 

Gold  is  removed  from  the  platinum  electrode  by  warming  with  a  solution  of  chromic 
anhydride  in  a  saturated  salt  solution,4  or  with  a  solution  of  potassium  cyanide  con- 
taining some  oxidizing  agent  as  hydrogen  peroxide,  sodium  peroxide  or  alkali  per- 
sulphate.5 

VOLUMETRIC  METHODS 

These  methods  are  applicable  to  the  determination  of  the  strength  of  chloride 
of  gold  solutions  used  in  photography,  electro  gilding,  and  as  electrolyte  in  the 
Wohlwill  parting  process. 

Preparation  of  the  Sampl?.  Nitric  acid  or  nitrates  in  the  solutions  should  be 
removed  by  repeated  evaporations  to  syrup  with  addition  of  hydrochloric  acid 
saturated  with  chlorine.  Free  chlorine  or  bromine  should  be  removed  by  addition 
of  ammonia  to  formation  of  permanent  precipitate,  then  making  the  solution 
very  slightly  acid  with  hydrochloric  acid  and  heating  until  the  precipitate  of 
fulminating  gold  dissolves.  The  gold  solution  should  contain  but  little  free 
hydrochloric  acid,  an  excessive  amount  of  which  may  be  removed  by  ammonia. 

Permanganate  Method 

Weak  gold  solutions  should  be  concentrated  whenever  possible.  The  perman- 
ganate method,6  which  is  not  applicable  when  the  sample  contains  organic  matter, 
depends  upon  the  titration,  after  complete  precipitation  of  gold,  of  the  unoxidized 
portion  of  a  measured  quantity  of  an  added  reagent  of  a  known  gold  precipi- 
tating value.  The  reagent  may  be  ammonium  or  potassium  oxalate,  ferrous 
sulphate  or  ferrous  ammonium  sulphate  in  solutions  varying  from  5  to  25  milligram? 
gold  precipitating  value  and  is  titrated  with  a  permanganate  solution  of  approx- 
imately equal  oxidizing  strength.  One  part  of  gold  requires  for  precipitation  1.08 
of  ammonium  oxalate,  1.40  of  potassium  oxalate,  4.22  of  ferrous  sulphate,  5.96 

Classen,  "  Quantitative  Chemical  Analysis  by  Electricity,"  Classen-Boltwood. 

2  J.A.C.S.,  Oct.,  1904,  1255. 

3  Elec.  Chem.  and  Met.  Ind.,  3,  490. 

4  Classen-Boltwood,  "  Quantitative  Chemical  Analysis  by  Electricity." 

5  Rose,  "  Met.  of  Gold,"  5th  Ed.,  469. 

6  Bull.  Chim.  Farmac.,  1894,  XXX,  III,  c5;  Oestr.  Zeit.  f.  Berg,  und  Hut.,  182, 1880; 
Sutton,  "  Volumetric  Analysis,"  10th  Ed.;   E.  A.  Smith,  "  Sampling  and  Assaying  of 
Precious  Metals";  Min.  Eng.  World,  37,  853. 


CMJFORKiA   COU66E 

~f  PHARMACY  - 


196  GOLD 

parts  ferrous  ammonium  sulphate,  each  in  crystalline  form.  The  most  satis- 
factory precipitations  are  made  with  the  iron  salts.  The  standard  solution  of 
either  should  contain  about  0.1  per  cent  of  sulphuric  acid.  One  part  of  gold,  in 
solution  as  auric  chloride,  has  an  oxidizing  value  equivalent  to  0.4808  part  of 
potassium  permanganate. 

The  precipitating  value  of  0.2548  gram  of  dry  Sorenson's  sodium  oxalate  is  250 
milligrams  of  gold,  and  by  titrating  a  solution  of  this  amount  of  oxalate  in  250  cc. 
of  water,  aciduated  with  a  few  drops  of  sulphuric  acid,  the  oxidizing  value  of  the 
permanganate  solution  is  obtained  in  terms  of  gold. 

The  value  of  the  precipitating  reagent  and  relative  oxidizing  value  of  the 
permanganate  solution  can  be  checked  very  accurately  by  adding  a  measured 
quantity  of  the  reagent  to  an  excess  of  gold  chloride,  filtering,  washing  thoroughly, 
incinerating  and  weighing  the  precipitate  obtained  in  a  tared  porcelain  crucible. 

Procedure.  In  carrying  out  the  determination  of  a  gold  solution,  a  meas- 
ured or  weighed  portion  is  freed  of  oxidizing  agents,  a  measured  amount  of  the 
standard  precipitating  reagent  added  in  slight  excess  of  the  amount  required  to 
decolorize  the  solution,  and  digestion  on  a  steam  bath  or  hot  plate  continued  until 
the  gold  settles  out,  leaving  a  clear  liquid.  A  few  drops  of  sulphuric  acid  may  be 
then  added  and,  without  filtering,  titration  performed.  The  gold  value  of  the 
quantity  of  reagent  added,  minus  that  found  of  the  excess  of  reagent,  is  the  gold 
content  of  the  amount  of  the  sample  taken. 

Iodide  Method 

Small  quantities  of  gold  are  determined  by  Gooch  and  Morley's  iodide 
method.1  A  measured  or  weighed  portion  of  the  gold  solution  is  treated, 
as  has  been  described  for  removal  of  oxidizing  agents,  with  an  excess  of  free 
hydrochloric^acid.  Potassium  iodide  solution  is  run  into  the  cold  liquid  until 
the  gold  precipitated  as  aurous  iodide  is  completely  dissolved.  Starch  solution  is 
then  added,  and  the  amount  of  N/1000  thiosulphate  required  to  decolorize  the 
liquid  noted.  From  this  amount  is  deducted  the  amount  of  N/1000  iodine 
required  to  just  produce  a  perceptible  rose  tint  in  the  liquid. 

The  reactions  involved  are  AuCl3+3KI  =  AuI+I2+3KCl  and  I,+2Na2S203  = 


The  gold  value  of  the  N/1000  solution  of  sodium  thiosulphate  should  be  deter- 
mined by  performance  of  the  operations  of  the  method  on  a  known  quantity 
of  gold,  similar  in  amount  and  contained  in  a  volume  of  solution  approxi- 
mately equal  to  that  of  the  analysis. 

Lenher's  Method.  By  Lenher's  method  2  of  determining  gold  in  solutions  free  of 
oxidizing  agents,  sulphurous  acid  of  a  reducing  strength  of  2-5  milligrams  gold  per  cc.  is 
used  as  the  reagent.  The  sulphurous  acid  requires  frequent  standardizing  by  means 
of  standard  iodine  or  potassium  iodide  to  which  a  definite  amount  of  standard  per- 
manganate has  been  added  or  by  a  gold  solution  of  known  strength.  Using  starch 
as  indicator,  the  iodine  liberated  by  addition  of  potassium  iodide  can  be  titrated  by 
sulphurous  acid.  Bromine  liberated  by  potassium  bromide  according  to  the  equation, 
AuCl3-f2KBr=AuCl+2KCl+Br2,  can  be  titrated  by  sulphurous  acid.  Excess  of 
magnesium  or  sodium  chloride  gives  to  auric  chloride  a  yellow  color  which  by  sul- 
phurous acid  can  be  titrated  to  the  colorless  or  aurous  state.  These  alkaline  salts 
do  not  interfere  in  the  potassium  bromide  or  iodide  reactions. 


iAmer.  Jour.  Sci.,  Oct.,  1899,  261;    Min.  and  Eng.  World,  37>  853;    Vol.  Am., 
Sutton,  10th  Ed.;  "  Assaying  of  Precious  Metal,"  E.  A.  Smith. 
2  Jour.  Am.  Chem.  Soc.,  June,  1913,  735. 


GOLD  197 

COLORIMETRIC   METHODS 

Practical  application  of  these  methods  is  made  in  the  estimation  of  gold  in 
the  liquors  produced  in  the  treatment  of  ores  by  the  cyanide  process. 

Prister's  Method 

By  Prister's  method *  a  slight  excess  of  copper  solution  is  added  to  a  100  to  200- 
cc.  portion  of  a  cyanide  solution  in  which  the  cyanide  has  been  decomposed  by 
boiling  several  minutes  after  acidifying  with  hydrochloric  acid.  Assurance  of 
the  presence  of  an  excess  of  copper  is  made  by  spot  test  with  a  solution  of  potas- 
sium ferrocyanide. 

The  copper  solution  is  made  by  boiling  for  ten  minutes  in  contact  with  copper 
shavings,  a  solution  of  1  part  blue  vitriol  and  2  parts  salt  in  10  parts  of  water, 
and  adding  a  little  acetic  acid  on  cooling.  A  few  drops  of  a  1  to  2  %  sodium  sul- 
phide solution  are  added,  the  liquid  boiled  for  five  minutes,  the  precipitate 
allowed  to  settle,  and  liquid  separated  by  decantation  on  to  a  filter.  The  pre- 
cipitate in  the  beaker  and  on  the  filter  is  dissolved  with  2|  to  3  cc.  of  a  3  to  5% 
solution  of  potassium  cyanide  to  which  a  few  drops  of  potassium  hydrate  solu- 
tion has  been  added. 

Gold  is  precipitated  from  this  cyanide  solution  (which  may  be  turbid),  by 
addition  of  1  to  2  grams  of  zinc  dust  and  warming  to  100°  F.  for  half  an  hour. 
Liquid  is  separated  by  decantation  through  a  filter.  The  residue  on  the  filter 
and  in  the  beaker  is  first  treated  with  hydrochloric  acid  to  dissolve  zinc,  then  with 
10  cc.  aqua  regia,  the  reagent  being  passed  several  times  through  the  filter. 
Stannous  chloride  solution  is  then  added  to  the  liquid  diluted  to  20  cc.  Com- 
parison of  the  coloration  produced  is  made  with  that  from  a  standard  solution  of 
gold  treated  in  the  same  manner. 

Cassel's  Method.  By  Cassel's  method  2  0.5  gram  potassium  bromate  is  mixed 
with  10  to  50  cc.  of  the  cyanide  solution  and  concentrated  sulphuric  acid  added 
gradually  with  constant  agitation  until  reaction  commences.  When  the  reaction 
stops,  saturated  solution  of  stannous  chloride  is  added  dropwise  until  the  liquid  is 
just  colorless.  The  tint  produced  is  compared  with  that  from  a  standard  gold 
solution  treated  in  the  same  manner. 

Moir's  Method.  By  Moir's  method 3  a  measured  quantity  of  the  cyanide  solution 
is  oxidized  by  addition  of  1  to  2  grams  of  sodium  peroxide  and  boiling.  If  sufficient 
sodium  peroxide  is  present,  the  brown  spot  produced  by  addition  of  a  few  drops  of 
lead  acetate  will  immediately  dissolve.  The  lead-aluminum  couple  formed  by  addi- 
tion of  aluminum  powder  precipitates  gold  which  is  filtered  off.  To  the  aqua  regia 
solution  of  the  precipitate  a  solution  of  stannous  chloride  is  added  drop  by  drop  until 
the  liquid  is  dissolved.  The  purple  of  Cassius  tint  developed  is  compared  with  per- 
manent standards  composed  of  mixtures  of  solutions  of  copper  sulphate  and  cobalt 
nitrate  which  have  been  adjusted  to  shades  corresponding  to  those  produced  by  known 
amounts  of  gold  treated  according  to  the  method  described. 

Bettel 4  filters  suspended  matter  from  the  cyanide  solution,  adds  a  measured  quan- 
tity of  a  strong  solution  of  potassium  cyanide  which  contains  some  cuprous  cyanide  and 
precipitates  gold  by  the  copper  zinc  couple  produced  by  addition  of  a  measured  quantity 
of  zinc  fume.  The  remainder  of  the  method  is  the  same  as  Prister's. 

1  Proc.  Chem.  Met.  and  Min.  Soc.  of  So.  Af .,  IV,  235,  1904. 

2  Eng.  and  Min.  Journal,  Oct.  31,  1903. 

3  Proc.  Chem.  Met.  and  Min.  Soc.  of  So.  Af .,  Sept.,  1913. 

4  Min.  World,  33, 102  and  35,  987. 


198  GOLD 

Dowsett's  1  factory  test  of  barren  cyanide  solutions  is  capable  of  detecting 
variation  in  gold  value  of  1  cent  per  ton  in  solutions  varying  from  one 
cent  to  about  15  cents  per  ton.  To  500  cc.  of  the  sample  in  a  bottle  with  slight 
shoulder  are  added  10-15  cc.  saturated  sodium  cyanide  solution,  2  or  3  drops 
saturated  lead  nitrate  solution  and  1-2  grams  200-mesh  fine  zinc  dust.  The  stop- 
pered bottle  is  shaken  violently  until  the  precipitate  settles  rapidly.  Inverting 
the  bottle  allows  the  precipitate  to  settle  into  a  casserole.  .  Clear  liquid  is  removed 
by  decantation.  Zinc  is  dissolved  by  hydrochloric  acid  added  drop  by  drop  until 
reaction  ceases.  A  few  drops  excess  hydrochloric  acid  and  3-5  drops  dilute 
nitric  acid  (sp.gr.  1.18)  are  added  and  the  liquid  concentrated  to  1-2  cc.  The 
solution  is  transferred  to  a  ^-in.  diameter  test-tube,  about  1  cc.  of  stannous  chloride 
reagent  added  and  grade  of  cyanide  solution  estimated  by  the  tint  obtained  after 
one  or  two  minutes  standing.  1/1000  oz.  gold  per  ton  of  original  cyanide  solution 
gives  a  very  slight  coloration;  15/10000  a  slight  yellow;  1/500  a  slight  pinkish 
yellow;  3/1000  a  strong  pink;  1/250  the  purple  of  Cassius.  Too  much  nitric  acid 
hinders  the  production  and  the  presence  of  mercury  causes  modification  of  the 
color.  No  more  lead  nitrate  should  be  used  than  is  sufficient  to  produce  a  rapidly 
settling  precipitate.  The  stannous  chloride  reagent  is  a  water  solution  contain- 
ing about  12|%  crystals  and  10%  concentrated  hydrochloric  acid. 

PREPARATION   OF  PROOF  GOLD 

Commercial  gold  may  contain  arsenic,  antimony,  selenium,  tellurium,  copper, 
lead,  mercury,  silver,  zinc,  palladium,  platinum  and  other  metals  of  the  platinum 
group.  The  method  of  making  pure  gold  depends  to  a  certain  extent  upon  the 
character  and  quantity  of  impurities.2  The  method  described  assumes  the 
raw  material  to  be  of  extreme  impurity.  The  metal  is  treated  in  10-g  am  portions. 

When  the  metal  contains  silver  its  solution  is  effected  most  quickly  by  rolling 
extremely  thin  and  annealing  before  treatment  with  acids. 

The  strips,  in  a  covered  No.  6  casserole  on  a  steam  bath,  are  dissolved  with  a 
mixture  of  5  cc.  nitric  and  50  cc.  hydrochloric  acid.  If  but  little  silver  is  present 
the  quantity  of  hydrochloric  acid  may  be  decreased  to  25  cc.  The  solution  is 
evaporated  to  dryness  and  the  casserole  gently  heated  over  a  Eunsen  flame  until 
all  the  gold  is  reduced  to  metal. 

Digestion  with  ammonia  will  dissolve  most  of  the  silver  and  copper.  After 
decanting  the  ammoniacal  solution  and  washing  with  water,  the  gold  is  digested 
with  hot  nitric  acid.  If  the  solution  is  wine  colored  the  digestion  is  continued 
for  several  hours,  and  reheated  with  fresh  portions  of  acid  until  the  absence  of 
color  indicates  removal  of  palladium.  The  gold  is  now  dissolved  with  5  cc.  of  nitric 
and  15  to  20  cc.  hydrochloric  acids,  evaporated  to  dryness,  residue  moistened  with 
the  least  quantity  of  hydrochloric  acid,  dissolved  with  about  800  cc.  water  and 
liquid  transferred  to  a  1000  cc.  beaker.  After  the  faint  cloud  of  silver  chloride 
settles  to  the  bottom  of  the  beaker,  the  clear  liquid  only  is  siphoned  to  another 
beaker,  and  allowed  to  stand  another  period  of  several  days  if  it  appears  at  all 
cloudy.  The  clear  liquid  is  now  siphoned  into  a  1000-cc.  flask  and  sulphur  dioxide 
gas  passed  until  the  gold  is  practically  all  precipitated.  The  gold  is  allowed  to 

1  Trans.  I.M.M.,  1912-13,  190;  Met.  and  Chem.  Eng.,  July,  ,1914. 

2Eng.  and  Min.  Jour.,  68,  785,  1899;  "Metallurgy  of  Gold,"  Rose,  5th  Ed.;  Min. 
and  Sci.  Press,  Nov.  14,  1903;  "  Manual  of  Fire  Assaying,"  Fulton;  "  Assaying  of  Pre- 
cious Metals,"  Smith. 


GOLD  199 

settle,  digested  with  hot  nitric  acid  for  a  few  minutes,  washed  by  decantation 
several  times,  redissolved  with  aqua  regia,  solution  transferred  to  a  casserole,  and 
nitric  acid  expelled  by  repeated  evaporation  to  syrup  with  addition  of  hydro- 
chloric acid.  The  product  of  the  second  evaporation  is  moistened  with  the  least 
quantity  of  hydrochloric  acid,  dissolved  with  water  and  solution  transferred  to 
a  1000-cc.  beaker  or  Erlenmeyer  flask.  To  the  liquid  of  about  500-cc.  volume  is 
added  11  grams  of  ammonium  oxalate  crystals.  The  beaker  is  permitted  to 
remain  on  a  steam  bath  until  reaction  is  complete.  The  spongy  mass  of  gold 
is  now  washed  with  hot  water  by  decantation  until  free  of  salts. 

The  gold  is  dried,  melted  in  a  clay  crucible  which  has  previously  been  thinly 
glazed  with  borax  glass  and  poured  out  into  a  mold  of  charcoal,  graphite  and  clay 
or  iron  polished  with  graphite. 

The  ingot,  which  will  have  a  volume  of  half  a  cubic  centimeter,  is  cleaned  by 
paring  with  a  knife  and  rolled  or  hammered  into  a  thin  sheet.  The  rolls  or 
hammer  should  be  clean,  bright  and  free  of  grease. 

The  gold,  cut  into  convenient  strips,  is  digested  for  several  hours  with  hydro- 
chloric acid  and  finally  washed  thoroughly  with  distilled  water. 

The  dried  gold  thus  prepared  may  be  considered  1000  fine. 


IODINE 

WILFRED  W.  SCOTT 

If  at.wt.  136.93;  sp.gr.  4.948170;  m.p.  113.5°; l  b.p.  184.4°  C;  acids,  HI, 

HIO,  HI03,  HI04. 

DETECTION 

The  element  may  be  recognized  by  its  physical  properties.  It  is  a  grayish 
black,  crystalline  solid,  with  metallic  luster,  brownish-red  in  thin  layers.  It 
vaporizes  at  ordinary  temperatures  with  characteristic  odor.  Upon  gently 
heating  the  element  the  vapor  is  evident,  appearing  a  deep  blue  when  unmixed 
with  other  gases,  and  violet  when  mixed  with  air.  It  colors  the  skin  brown. 
Chemically  it  behaves  very  similarly  to  chlorine  and  bromine. 

Free  iodine  colors  water  yellow  to  black,  carbon  disulphide  violet,  ether 
or  chloroform  a  reddish  color,  cold  starch  solution  blue. 

Tannin  interferes  with  the  usual  tests  for  iodine,  unless  ferric  chloride  is 
present. 

Iodide.  The  dry  powder,  heated  with  concentrated  sulphuric  acid,  evolves 
violet  fumes  of  iodine.  Iodine  is  liberated  from  iodides  by  solutions  of  As5, 
Sb»,  Bi',  Cu",  Fe'",  Cr«,  H3Fe(CN)6,  HN02,  Cl,  Br,  H202,  ozone. 

Insoluble  iodides  may  be  transposed  by  treatment  with  H2S,  the  filtered 
solution  being  tested  for  the  halogen. 

lodate.  The  acidulated  solution  is  reduced  by  cold  solution  of  S02,  or 
K4Fe(CN)6,  (acidulated  with  dilute  H2S04),  or  by  Cu2Cl2,  H3As03,  FeS04,  etc. 
An  iodate  in  nitric  acid  may  be  detected  by  diluting  the  acid  with  water,  adding 
starch  solution,  then  hydrogen  sulphide  water,  drop  by  drop,  a  blue  zone  forming 
in  presence  of  the  substance. 

ESTIMATION 

The  element  is  found  free  in  some  mineral  waters;  combined  as  iodides 
and  iodates  in  sea  water;  in  ashes  of  sea  plants;  small  quantities  in  a  number 
of  minerals,  especially  in  Chili  saltpeter  as  sodium  iodate,  hence  in  the  mother 
liquor  from  the  Chilian  niter  works  from  which  iodine  is  principally  produced. 
Sea-weed  ash  (drift  kelp,  Laminaria  digitata  and  L.  stenophylla)  is  an  important 
source  of  iodine. 

Free  iodine,  potassium  iodide,  iodoform,  are  the  principal  commercial  products. 

Preparation   and   Solution   of  the  Sample 

In  dissolving  the  substance  it  will  be  recalled  that  free  iodine  is  soluble  in 
alcohol,  ether,  chloroform,  glycerole,  benzole,  carbon  disulphide,  solutions  of 
soluble  iodides.  One  hundred  cc.  of  water  at  11°  C.  is  saturated  with  0.0182 
gram  iodine,  at  55°  with  0.092  gram. 

^Circular  35  (2d  ed.)  U.  S.  Bureau  of  Standards. 
200 


IODINE  201 

Iodides  of  silver,  copper  (cuprous),  mercury  (mercurous),  and  lead  are 
insoluble,  also  Til,  PdI2.  Iodides  of  other  metals  are  soluble;  those  of  bismuth, 
tin,  and  antimony,  require  a  little  acid  to  hold  them  in  solution. 

lodates  of  silver,  barium,  lead,  mercury,  bismuth,  tin,  iron,  chromium 
require  more  than  500  parts  of  water  at  15°  C.  to  hold  them  in  solution, 
lodates  of  copper,  aluminum,  cobalt,  nickel,  manganese,  zinc,  calcium,  strontium, 
magnesium,  sodium,  and  potassium  are  more  soluble.  One  hundred  cc.  of 
cold  water  dissolves  0.00385  gram  AgI03  and  0.000035  gram  Agl  at  ordinary 
temperatures. 

Free  Iodine  (Commercial  Crystals).  Iodine  is  best  brought  into  solution 
in  a  strong  solution  of  potassium  iodide  according  to  the  procedure  described 
for  standardization  of  sodium  thiosulphate  under  Volumetric  Methods.  The 
iodine  is  now  best  determined  volumetrically  by  titration  with  standard  thio- 
sulphate or  arsenic. 

Iodine  or  Iodides  in  Water.  The  sample  of  water  is  evaporated  to  about 
one-fourth  its  volume  and  then  made  strongly  alkaline  with  sodium  carbonate. 
The  precipitated  calcium  and  magnesium  carbonates  are  filtered  off  and  washed. 
The  filtrate  containing  the  halogens  is  evaporated  until  the  salts  begin  to  crystallize 
out.  The  hot  concentrated  solution  is  poured  into  three  volumes  of  absolute 
alcohol  and  the  resulting  solution  again  filtered.  The  residue  is  washed  four 
or  five  times  with  95%  alcohol.  All  of  the  bromine  and  iodine  pass  into  the 
solution,  whereas  a  large  part  of  chlorine  as  sodium  chloride  remains  insoluble 
and  is  filtered  off.  About  half  a  cc.  of  50%  potassium  hydroxide  is  added  and 
a  greater  part  of  the  alcohol  distilled  off  with  a  current  of  air.  The  residue 
is  concentrated  to  crystallization  and  again  poured  into  three  times  its  volume 
of  absolute  alcohol  and  filtered  as  above  directed.  This  time  only  one  or  two 
drops  of  potassium  solution  is  added  and  the  procedure  repeated  several 
times.  The  final  filtrate  is  freed  from  alcohol  by  evaporation,  the  solution 
taken  to  dryness  and  gently  ignited,  then  taken  up  with  a  little  water  and  filtered. 
Iodine  is  determined  in  the  filtrate,  preferably  by  the  volumetric  procedure  III, 
decomposition  with  nitrous  acid,  described  under  Volumetric  Methods,  p.  206. 

Organic  Substances.  If  only  an  iodide  is  present,  the  Carius  method  is 
followed;  in  presence  of  other  halogens,  the  "lime  method"  is  preferred.  Details 
of  these  methods  are  given  in  the  chapter  on  Chlorine  under  Preparation  and 
Solution  of  the  Sample,  p.  121. 

Silver  iodide  cannot  be  separated  from  the  glass  of  the  combustion-tube 
by  solution  with  ammonium  hydroxide  as  is  the  chloride  or  bromide  of  silver. 
The  compound,  together  with  the  glass,  is  collected  upon  a  filter  paper,  and 
washed  with  dilute  nitric  acid,  followed  by  alcohol;  then  dried  at  100°  C. 
After  removing  most  of  the  iodide  and  the  glass,  the  filter  is  ignited  in  a  weighed 
porcelain  crucible,  the  main  bulk  of  the  material  then  added,  the  substance 
fused  and  weighed  as  Agl + glass.  The  mass  is  then  covered  with  dilute  sul- 
phuric acid  and  a  piece  of  pure  zinc  added.  After  several  hours  (preferably  over 
night)  the  excess  zinc  is  carefully  removed  and  the  iodine  solution  decanted 
from  the  glass  and  metallic  silver,  and  the  residue  washed  by  decantation.  The 
silver  is  now  dissolved  in  hot  dilute  nitric  acid,  then  filtered  from  the  residue  of 
glass  through  a  small  filter.  The  glass  and  filter  are  ignited  and  weighed.  The 
difference  between  the  two  weighings  is  due  to  silver  iodide. 

Minerals.  Phosphates.  The  substance  is  decomposed  by  digestion  with 
1  : 1  sulphuric  acid  in  a  flask  through  which  a  current  of  air  passes  to  sweep  out 


202  IODINE 

the  iodine  vapor  into  a  solution  of  potassium  hydroxide,  the  sample  being 
boiled  until  all  the  iodine  vapors  have  been  driven  into  the  caustic.  lodates 
are  converted  to  iodides  by  reduction  with  sulphurous  acid. 

With  the  iodine  content  below  0.02%,  a  50  to  100-gram  sample  should  be 
taken. 

SEPARATIONS 

Separation  of  Iodine  from  the  Heavy  Metals.  The  heavy  metals  are  pre- 
cipitated as  carbonates  by  boiling  with  solutions  of  alkali  carbonates,  the  soluble 
alkali  iodide  being  formed. 

Iodine  is  liberated  from  combination  by  nitrous  acid. 

Silver  iodide  may  be  decomposed  by  warming  with  metallic  zinc  and  sul- 
phuric acid. 

Separation  of  Iodine  from  Bromine  or  from  Chlorine.1  Details  of  sepa- 
ration and  estimation  of  the  halides  in  presence  of  one  another  are  given  in 
the  chapter  on  Chlorine.  Advantage  is  taken  of  the  action  of  nitrous  acid  on 
dilute  solutions,  free  iodine  being  liberated,  while  bromides  and  chlorides  are 
not  acted  upon. 

The  solution  containing  the  halogens  is  place  in  a  large,  round-bottom  flask 
and  diluted  to  about  700  cc.  Through  a  two-holed  stopper  a  glass  tube  passes 
to  the  bottom  of  the  flask;  through  this  tube  steam  is  conducted  to  assist  the 
volatilization  of  iodine.  A  second  short  tube  connected  to  the  absorption  appa- 
ratus conducts  the  evolved  vapor  from  the  flask  into  a  5%  caustic  soda  solution 
containing  an  equal  volume  of  hydrogen  peroxide  (about  50  cc.  of  each).  The 
absorption  system  may  be  made  by  connecting  two  Erlenmeyer  flasks  in  series, 
the  inlet  tubes  dipping  below  the  solutions  in  the  flasks.  It  is  advisable  to  cool 
the  receivers  with  ice. 

Two  to  3  cc.  of  dilute  sulphuric  acid  (1  :  1)  and  25  cc.  of  10%  sodium  nitrite 
solution  are  added  to  the  liquid  containing  the  halogens,  the  apparatus  is  immedi- 
ately connected,  and  the  contents  of  the  large  flask  heated  to  boiling,  conducting 
steam  into  it  at  the  same  time.  The  iodine  vapor  is  gradually  driven  over  into 
the  cooled  receiving  flasks. 

When  the  solution  in  the  large  flask  has  become  colorless  it  is  boiled  for  half 
an  hour  longer.  The  steam  is  now  shut  off,  the  flask  disconnected  from  the  receiv- 
ing flasks  and  the  heat  turned  off.  The  contents  of  the  receiving  flasks  are  com- 
bined with  the  washing  from  the  connecting  tubes  and  the  solution  heated  to 
boiling  to  expel,  completely,  hydrogen  peroxide.  The  cooled  liquid  is  acidified 
with  a  little  sulphuric  acid  and  the  solution  decolorized  with  a  few  drops  of  sul- 
phurous acid.  Iodine  is  now  precepitated  as  silver  iodide  by  adding  an  excess 
of  silver  nitrate  and  a  little  nitric  acid  and  boiling  the  mixture  to  coagulate  the 
precipitate.  Agl  is  determined  as  directed  on  page  203. 

Chlorine  and  bromine  remain  in  the  large  flask  in  combined  form  and  may  be 
determined  in  this  solution  if  desired. 

NOTES.     Reactions:  2KI+2KNO2+4H2SO4  =  I2+2NO+4KHSO4-f-2H20. 

2NaOH+I2  =  NaI+NaIO-f  H2O  and  NaIO+H2O2  =  H2O+O2+NaI. 

Consult  Separations  in  the  chapter  on  Chlorine,  p.  123. 

1  References:  Method  of  Jannasch,  Zeit.  fur  anorg.  Chem.,  1,  p.  144  (1892).  Tread- 
well  and  Hall,  "  Analytical  Chemistry."  F.  A.  Gooch  "  Methods  in  Chemical  Analysis." 


IODINE  203 

Separation  of  Iodine  from  Chlorine  and  Bromine  by  Precipitation  as 
Palladous  Iodide.  The  solution  containing  the  halogens  is  acidified  with  hydro- 
chloric acid,  and  palladous  chloride  solution  added  to  the  complete  precipitation 
of  the  iodide.  The  compound  is  allowed  to  settle  in  a  warm  place  for  twenty- 
four  hours  or  more  and  then  filtered  and  washed  free  of  the  other  halogens. 
It  may  now  be  dried  and  weighed  as  palladous  iodide,  PdI2,  or  ignited  in  a 
current  of  hydrogen,  then  weighed  as  metallic  palladium  and  the  equivalent 
iodine  calculated.  See  Gravimetric  methods. 


GRAVIMETRIC   METHODS 
Precipitation  as  Silver  Iodide 

The  procedure  is  practically  the  same  as  that  described  for  determining 
chlorine. 

Silver  nitrate  solution  is  added  to  the  iodide  solution,  slightly  acidified  with 
nitric  acid.  The  precipitate  is  filtered  into  a  weighed  Gooch  crucible,  then 
washed,  dried,  gently  ignited,  and  weighed  as  silver  iodide. 

AglXO.5406  =1  or  X0.7071  =KI. 

NOTE.  If  filter  paper  is  used  in  place  of  a  Gooch  crucible,  the  precipitate  is 
removed  and  the  filter  ignited  separately.  A  few  drops  of  nitric  and  hydrochloric 
acid  are  added,  the  acids  expelled  by  heat  and  the  residue  weighed  as  AgCl.  This, 
multiplied  by  1.638  =  AgI.  The  result  is  added  to  the  weight  of  the  silver  iodide, 
which  is  ignited  and  weighed  separately. 

Determination  of  Iodine  as  Palladous  Iodide 

This  method  is  applicable  for  the  direct  determination  of  iodine  in  iodides 
in  presence  of  other  halogens. 

The  method  of  isolation  of  iodine  as  the  palladous  salt  has  been  given  under 
Separations.  The  salt  dried  at  100°  C.  is  weighed  as  PdI2. 

PdI2X0.704=I. 

PdI2  ignited  in  a  current  of  hydrogen  is  changed  to  metallic  palladium. 

PdX2.379=I. 

VOLUMETRIC   METHODS 
Determination  of  Hydriodic  Acid— Soluble  Iodides 

Free  hydriodic  acid  cannot  be  determined  by  the  usual  alkalimetric  methods 
for  acids.  The  procedures  for  its  estimation,  free  or  combined  as  a  soluble 
salt,  depends  upon  the  liberation  of  iodine  and  its  titration  with  standard  sodium 
thiosulphate,  in  neutral  or  slightly  acid  solution;  or  by  means  of  standard  arsen- 
ious  acid,  in  presence  of  an  excess  of  sodium  bicarbonate  in  a  neutral  solution. 
The  following  equations  represent  the  reactions  that  take  place: 
I.  Thiosulphate.  2NaS203+l2=2NaI+Na2S406. 

II.  Arsenite.    Na,AsO,+I,+HaO=Na,As04+2HI. 


204  IODINE 

The  free  acid  formed  in  the  second  reaction  is  neutralized  and  the  reversible 
reaction  thus  prevented  : 

HI+NaHC03  =NaI+H204-C02. 

The  presence  of  a  free  alkali  is  not  permissible,  as  the  hydroxyl  ion  would 
react  with  iodine  to  form  iodide,  hypoiodite  and  finally  iodate,  hence  sodium 
or  potassium  carbonates  cannot  be  used.  Alkali  bicarbonates,  however,  do  not 
react  with  iodine. 

Standard  Solutions.  Tenth  Normal  Sodium  Thiosulphate.  From  the 
reaction  above  it  is  evident  that  1  gram  molecule  of  thiosulphate  is  equivalent 
to  1  atom  iodine  =  1  atom  hydrogen,  hence  a  tenth  normal  solution  is  equal  to  one- 
tenth  the  molecular  weight  of  the  salt  per  liter,  e.g.,  24.822  grams  Na2S203-5H20; 
generally  a  slight  excess  is  taken  —  25  grams  of  the  crystallized  salt.  It  is 
advisable  to  make  up  5  to  10  liters  of  the  solution,  taking  125  to  250  grams 
sodium  thiosulphate  crystals  and  making  up  to  volume  with  distilled  water, 
boiled  free  of  carbon  dioxide.  The  solution  is  allowed  to  stand  a  week  to 
ten  days,  and  then  standardized  against  pure,  resublimed  iodine. 

About  0.5  gram  of  the  purified  iodine  is  placed  in  a  weighing  bottle  con- 
taining a  known  amount  of  saturated  potassium  iodide  solution  (2  to  3  grams 
of  KI  free  from  KI03  dissolved  in  about  £  cc.  of  H20),  the  increased  weight 
of  the  bottle,  due  to  the  iodine,  being  jioted.  The  bottle  and  iodine  are  placed 
in  a  beaker  containing  about  200  cc.  of  1%  potassium  iodide  solution  (1  gram 
KI  per  200  cc.),  the  stopper  removed  with  a  glass  fork  and  the  iodine  titrated 
with  the  thiosulphate  to  be  standardized. 

Calculation.  The  weight  of  the  iodine  taken,  divided  by  the  cc.  thio- 
sulphate required,  gives  the  value  of  1  cc.  of  the  reagent;  this  result  divided 
by  0.012692  gives  the  normality  factor. 

NOTE.  The  thiosulphate  solution  may  be  standardized  against  iodine,  which 
has  been  liberated  from  potassium  iodide  in  presence  of  hydrochloric  acid  by  a  known 
amount  of  standard  potassium  bi-iodate,  a  salt  which  may  be  obtained  exceedingly 
pure. 

KIO8-HIO3+10KI+llHCl 


A  tenth  normal  solution  contains  3.2496  grams  of  the  pure  salt  per  liter.  (One 
cc.  of  this  will  liberate  0.012692  gram  of  iodine  from  potassium  iodide.)  The  purity 
of  the  salt  should  be  established  by  standardizing  against  thiosulphate,  which  has  been 
freshly  tested  against  pure  resublimed  iodine. 

About  5  grams  of  potassium  iodide  (free  from  iodate)  are  dissolved  in  the  least 
amount  of  water  that  is  necessary  to  effect  solution,  and  10  cc.  of  dilute  hydrochloric 
acid  (1  :  2)  are  added,  and  then  50  cc.  of  the  standard  bi-iodate  solution.  The  solu- 
tion is  diluted  to  about  250  cc.  and  the  liberated  iodine  titrated  with  the  thiosulphate 
reagent;  50  cc.  will  be  required  if  the  reagents  are  exactly  tenth  normal. 

Tenth  Normal  Arsenite.  From  the  second  reaction  above  it  is  evident  that 
As203  is  equivalent  to  2I2,  e.g.,  to  4H,  hence  \  the  gram  molecular  weight  of 
arsenious  oxide  per  liter  will  give  a  normal  solution:  198  -5-4  =49.5. 

4.95  grams  of  pure  arsenious  oxide  is  dissolved  in  a  little  20%  sodium 
hydroxide  solution,  the  excess  of  the  alkali  is  neutralized  with  dilute  sulphuric 
acid,  using  phenolphthalein  indicator,  the  solution  being  just  decolorized.  Five 
hundred  cc.  of  distilled  water  containing  about  25  grams  of  sodium  bicarbonate 
are  added.  If  a  pink  color  develops,  this  is  destroyed  with  a  few  drops  of 
weak  sulphuric  acid.  The  solution  is  now  made  to  volume,  1000  cc.  The 


IODINE  205 

reagent"  is  standardized  against  a  measured  amount  of  pure  iodine.    The  oxide 
may  be  dissolved  directly  in  sodium  bicarbonate  solution. 

NOTE.  Commercial  arsenic  us  oxide  is  purified  by  dissolving  in  hot  hydrochloric 
acid,  filtering  the  hot  saturated  solution,  cooling,  decanting  off  the  mother  liquor 
washing  the  deposited  oxide  with  water,  drying  and  finally  subliming. 

Starch  Solution.  Five  grams  of  soluble  starch  are  dissolved  in  cold  water, 
the  solution  poured  into  2  liters  of  hot  water  and  boiled  for  a  few  minutes. 
The  reagent  is  kept  in  a  glass-stoppered  bottle. 

Iodides  are  decomposed  and  iodine  determined  by  one  of  the  following 
procedures : 

I.     Decomposition  of  the  Iodide  by  Ferric  Salts 

The  method  takes  advantage  of  the  following  reaction: 
Fe2(S04)3+2KI  =K2S04+I2-f-2FeS04. 

The  procedure  enables  a  separation  from  bromides,  as  these  are  not  acted 
upon  by  ferric  salts. 

Procedure.  To  the  iodide  in  a  distillation  flask  is  added  an  excess  of  ferric 
ammonium  alum,  the  solution  acidified  with  sulphuric  acid,  then  heated  to 
boiling,  and  the  iodine  distilled  into  a  solution  of  potassium  iodide.  The  free 
iodine  in  the  distillate  is  titrated  with  standard  thiosulphate,  or  by  arsenious 
acid  in  presence  of  an  excess  of  sodium  bicarbonate. 

The  reagent  is  added  from  a  burette  until  the  titrated  solution  becomes  a 
pale  yellow  color.  About  5  cc.  of  starch  solution  are  now  added  and  the  titra- 
tion  continued  until  the  blue  color  of  the  starch  fades  and  the  solution  becomes 
colorless. 

One  cc.  of  tenth  normal  reagent  =0.012692  gram  iodine,  equivalent  to 
0.012793  gram  HI,  or  0.016602  gram  KI. 

II.    Decomposition  with  Potassium  lodate1 

The  reaction  with  potassium  iodate  is  as  follows : 

5KI+KI03+6HC1  =KC1+3H20+3I2. 

It  is  evident  that  I  of  the  titration  for  iodine  would  be  equal  to  the  iodine 
of  the  iodide,  hence  1  cc.  of  tenth  normal  thiosulphate  is  equivalent  to  0.012692 
Xf  =0.01058  gram  iodine  due  to  the  iodide.  The  procedure  is  as  follows: 

Procedure.  A  known  amount  of  tenth  normal  potassium  iodate  is  added 
to  the  iodide  solution,  in  sufficient  amount  to  liberate  all  of  the  iodine,  com- 
bined as  iodide,  and  several  cc.  in  excess.  Hydrochloric  acid  and  a  piece  of  calcite 
are  added.  The  mixture  is  boiled  until  all  of  the  liberated  iodine  has  been 
expelled.  To  the  cooled  solution  2  or  3  grams  of  potassium  iodide  are  added 
and  the  liberated  iodine,  corresponding  to  the  excess  of  iodate  in  the  solution, 
is  titrated  with  standard  thiosulphate.  If  1  cc.  of  thiosulphate  is  equal  to  1 
cc.  of  the  iodate,  then  the  total  cc.  of  the  iodate  used,  minus  the  cc.  thio- 

iH.  Dietz  and  B.  M.  Margosches,  Chem.  Ztg.,  2,  1191,  1904.  Treadwell 
and  Hall,  "Analytical  Chemistry,"  Vol.  2. 


206 


IODINE 


sulphate  required  in  the  titration  gives  a  difference  due  to  the  volume  of  iodate 
required  to  react  with  the  iodide  of  the  sample. 

One  cc.  of  N/10  KI03  =0.01058  gram  I  in  KI. 
NOTE.     Tenth  normal  potassium  iodate  contains  3.5675  grams  KIO3  per  1000  cc. 

III.     Decomposition  of  the  Iodide  with  Nitrous  Acid  (Fresenius)1 

Nitrous  acid  reacts  with  an  iodide  as  follows : 

2HN02+2HI  =2NO+2H20+I2. 

Since  neither  hydrochloric  nor  hydrobromic  acids  are  attacked  by  nitrous 
acid,  the  method  is  applicable  to  determining  iodine  in  presence  of  chlorine  and 
bromine ;  hence  is  useful  for  determining  small  amounts  of  iodine  in 
mineral  waters  containing  comparatively  large  amounts  of  the  other 
halogens. 

Nitrous    Acid.    The   reagent  is  prepared  by  passing  the  gas 
j      |\          into  strong  sulphuric  acid  until  saturated. 

Ill  Procedure.     The  neutral   or  slightly  alkaline  solution  of  the 

iodide  is  placed  in  a  glass-stoppered  separatory  funnel,  Fig.  39, 
and  slightly  acidified  with  dilute  sulphuric  acid.  A  little  freshly 
distilled  colorless  carbon  disulphide  (or  chloroform)  is  added,  then 
10  drops  of  nitrous  acid  reagent.  The  mixture  is  well  shaken,  the 
disulphide  allowed  to  settle,  drawn  off  from  the  supernatant  solu- 
tion and  saved  for  analysis.  The  liquor  in  the  funnel  is  again 
extracted  with  a  fresh  portion  of  disulphide  and  if  it  becomes  dis- 
colored it  is  drawn  off  and  added  to  the  first  extract.  If  the 
extracted  aqueous  solution  appears  yellow,  it  must  be  igain  treated 
with  additional  carbon  disulphide  until  all  the  iodine  has  been 
removed  (e.g.,  until  additional  CS2  is  no  longer  colored  when  shaken 
with  the  solution).  The  combined  extracts  are  washed  with  three 
or  four  portions  of  water,  then  transferred  to  the  filter  and  again 
washed  until  free  from  acid.  A  hole  is  made  in  the  filter  and  the  disulphide 
allowed  to  run  into  a  small  beaker  and  the  filter  washed  down  with  about  5  cc. 
of  water.  Three  cc.  of  5%  sodium  bicarbonate  are  added  and  the  iodine  titrated 
with  N/20  or  N/50  standard  thiosulphate,  the  reagent  being  added  until  the 
reddish-violet  carbon  disulphide  becomes  colorless. 

The  sodium  thiosulphate  used  is  standardized  against  a  known  amount  of 
pure  potassium  iodide  treated  in  the  manner  described  above. 


FIG.  39. 


One  cc.  N/20  Na2S203  =  .00635  gram  I,  1  cc.  N/50  Na2S203  =  . 002538  gram  I. 


IODINE  207 

IV.  Liberation  of  Iodine  by  Means  of  Hydrogen  Peroxide  and 

Phosphoric  Acid  l 

Principle.  Iodine  is  liberated  from  an  iodide  by  addition  of  hydrogen  per- 
oxide to  the  solution  acidified  with  phosphoric  acid,  the  iodine  distilled  into 
potassium  iodide  and  titrated  with  thiosulphate. 

Procedure.  Fifty  cc.  of  the  iodide  solution  are  mixed  with  5  cc.  of  pure 
phosphoric  acid  and  10  to  20  cc.  hydrogen  peroxide  added,  the  mixture  being 
placed  in  a  round-bottomed  flask,  connected  with  a  short  condenser,  delivering 
into  two  absorption  vessels  containing  a  10%  solution  of  potassium  iodide. 
A  current  of  air  is  drawn  through  the  apparatus,  and  the  contents  of  the  flask 
gradually  heated  to  boiling.  The  iodine  is  absorbed  in  the  potassium  iodide 
solution  and  titrated  as  usual  with  standard  sodium  thiosulphate.  Twenty 
minutes'  heating  is  generally  sufficient. 

One  cc.  Na2S203  =0.012692  gram  I,  or  0.016602  gram  KI. 

NOTE.  Iodine  in  urine  may  be  determined  by  evaporating  to  1/10  its  volume. 
After  adding  an  excess  of  sodium  hydroxide,  the  mixture  is  taken  to  dryness  and 
gently  ignited.  The  ash  may  be  used  for  the  iodine  determination. 

V.  Oxidation    of    Combined     Iodine    with    Chlorine.     (Mohr's 

Modification  of  Dupre's  Method)2 

When  a  solution  of  potassium  iodide  is  treated  with  successive  amounts 
of  chlorine  water,  iodine  is  liberated,  which  reacts  with  an  excess  of  chlorine 
with  formation  of  chloride  of  iodine  (IC1)  and  with  greater  excess  the  penta- 
chloride  (IC15)  which  is  changed  in  presence  of  water  to  iodic  acid  (HI03) . 

Procedure.  The  weighed  iodide  compound  is  brought  into  a  stoppered 
flask,  and  chlorine  water  delivered  from  a  large  burette  until  all  yellow  color  has 
disappeared.  A  drop  of  the  mixture  brought  in  contact  with  a  drop  of  starch 
solution  should  produce  no  blue  color.  Sodium  bicarbonate  is  now  added  until 
the  mixture  is  slightly  alkaline,  followed  by  an  excess  of  potassium  iodide  and 
4  to  5  cc.  of  starch  reagent.  Standard  thiosulphate  is  now  added  until  the 
blue  color  is  removed.  The  excess  of  chlorine  water  is  thus  ascertained.  From 
the  value  of  the  chlorine  reagent  the  iodine  of  the  sample  may  readily  be 
calculated. 

The  chlorine  water  is  standardized  by  running  25  to  50  cc.  of  the  reagent 
into  potassium  iodide  solution  (see  procedure  for  bromides,  p.  81),  and 
titrating  the  liberated  iodine  with  standard  sodium  thiosulphate.  The  value 
of  the  reagent  in  terms  of  thiosulphate  are  thus  ascertained  and  from  this  the 
value  per  cc.  in  terms  of  iodine. 

OTHER  METHODS 
Volhard's  Method  for  Determining  Iodides 

This  procedure  is  very  similar  to  those  for  determining  chlorine  or  bromine, 
with  the  exception  that  silver  iodide  formed  will  occlude  both  the  iodide  solu- 

*E.  Winterstein  and  E.  Herzfeld,  Zeit.  Physiol.  Chem.,  63,  49-51,  1909.  Chem. 
Zentralbl.,  (1),  473-474,  1910. 

2Sutton,  "Volumetric  Analysis,"  10th  Ed. 


208  IODINE 

tion  and  silver  nitrate  unless  the  additions  of  the  silver  salt  are  made  in  small 
portions  with  vigorous  shaking. 

Standard  silver  nitrate  is  added  to  the  solution  in  a  glass-stoppered  flask, 
shaking  vigorously  with  each  addition.  As  long  as  the  solution  appears  milky 
the  precipitation  is  incomplete.  When  the  silver  iodide  is  coagulated  and  the 
supernatant  liquid  appears  colorless,  ferric  alum  solution  is  added,  and  the 
excess  of  silver  nitrate  titrated  with  potassium  sulphocyanate  until  the  char- 
acteristic reddish  end-point  is  obtained. 

The  iodine  is  calculated  from  the  amount  of  silver  nitrate  required.  E.g., 
total  AgN03  added,  minus  excess  determined  by  KCNS=cc.  AgN03  required 
by  the  iodine. 

NOTE.  The  ferric  salt  oxidizes  hydriodic  acid  with  separation  of  iodine,  whereas 
the  silver  iodide  is  not  acted  upon,  hence  the  indicator  is  added  after  all  the  iodide 
has  combined  with  silver. 

VI.    Determination  of  lodates 

The  procedure  is  the  reciprocal  of  the  one  for  determination  of  iodide  by 
means  of  an  iodate : 

Reaction.    KI03+5KI+6HC1  =6KCl+3H20-f3I2. 

Procedure.  The  solution  containing  the  iodate  is  allowed  to  run  into  an 
excess  of  potassium  iodide  solution  containing  hydrochloric  acid.  The  liber- 
ated iodine  is  titrated  with  sodium  thiosulphate  as  usual. 

One  cc.  N/10  Na2S203  =0.002932  gram  HI03,  or  0.003567  gram  KI03. 

VII.    Determination  of  Periodates 

The  procedure  is  the  same  as  that  described  for  iodates,  the  reaction  in  this 
case,  however,  being  as  follows: 

KI04+7KI+8HC1  =8KC1+4H20+4I2. 

From  the  equation  it  is  evident  that  1  gram  molecule  of  the  iodate  is  equiv- 
alent to  8  atoms  of  iodine  =8  atoms  of  hydrogen,  hence  £  the  molecular  weight 
per  liter  of  solution  would  equal  a  normal  solution.  Therefore,  1  cc.  of  a  tenth 
normal  solution  would  contain  0.019193-^8  =0.002399  gram  HI04. 

One  cc.  N/10  Na2S203  =0.002399  gram  HI04,  or  =0.002849  gram  HI04-2H20, 
or  =0.002875  gram  KI04. 

VIII.    Determination   of   lodates  and   Periodates   in   a   Mixture 

of  the  Two 

The  procedure  depends  upon  the  fact  that  an  iodate  does  not  react  with 
potassium  iodide  in  neutral  or  slightly  alkaline  solutions,  whereas  a  periodate 
undergoes  the  following  reactions : 

KI04+2KI-r-H20  =2KOH+KI03+I2. 

Procedure.  The  sample,  dissolved  in  water,  is  divided  into  two  equal 
portions. 

A.  To  one  portion  a  drop  of  phenolphthalein  indicator  is  added  and  the 


IODINE  209 

solution  made  just  faintly  alkaline  by  addition  of  alkali  to  acid  solutions  or 
hydrochloric  acid  to  alkaline  solution,  as  the  case  may  require.  Ten  cc.  of 
cold  saturated  solution  of  sodium  bicarbonate  are  added  and  an  excess  of  potas- 
sium iodide.  The  liberated  iodine  is  titrated  with  tenth  normal  arsenious  acid.1 
(Na2S203  will  not  do  in  this  case,  as  the  solution  is  alkaline.) 

One  cc.  N/10  As208  =0.0115  gram  KI04. 

B.  To  the  other  portion  potassium  iodide  is  added  in  excess  and  the  solu- 
tion made  distinctly  acid.  The  liberated  iodine  is  titrated  with  standard  sodium 
thiosulphate.  (As203  will  not  do.) 

Calculation.  In  the  acid  solution,  B,  both  iodates  and  periodates  are 
titrated,  whereas  in  the  alkaline  solution,  A,  only  the  periodates  are  affected. 
From  the  reactions  in  VII  and  VIII  it  is  evident  that  1  cc.  Na2S203  =4  cc.  As20» 
for  the  periodate  titration,  hence 

Cc.  Na2S203— cc.  As203X4=cc.  thiosulphate  due  to  KIOs. 
The  difference,  multiplied  by  0.003567  =  grams  KI03  in  the  sample. 

1  In  alkaline  solutions  the  arsenious  acid  titration  must  be  made,  whereas  in  acid 
solutions  potassium  thiosulphate  is  used. 


IRON 

WILFRED  W.  SCOTT 

Fe,  at.wt.  55.84;  sp.gr.  7.85-7.88;  m.p.  pure  15300,1  wrought  160O0,2  white 
pig  10750,1  gray  pig  12750,1  steel  1375°;  *  b.p.  3450°  1  C.;  oxides  FeO, 
Fe2O3t  Fe3O4. 

DETECTION 

Ferric  Iron.  The  yellow  to  red  color  in  rocks,  minerals,  and  soils  is  gen- 
erally due  to  the  presence  of  iron. 

Hydrochloric  acid  solutions  of  iron  as  ferric  chloride  are  colored  yellow. 

Potassium  or  ammonium  sulphocyanate  produces  a  red  color  with  solutions 
containing  ferric  iron.  Nitric  acid  and  chloric  acid  also  produce  a  red  color  with 
potassium  or  ammonium  sulphocyanate.  This  color,  however,  is  destroyed  by 
heat,  which  is  not  the  case  with  the  iron  compound.  The  red  color  of  ferric 
iron  with  the  cyanate  is  destroyed  by  mercuric  chloride  and  by  phosphates, 
borates,  certain  organic  acids,  and  their  salts,  e.g.,  acetic,  oxalic,  tartaric,  citric, 
racemic,  malic,  succinic,  etc. 

Potassium  ferrocyanide,  K4Fe(CN)6,  produces  a  deep  blue  color  with  ferric 
salts. 

Salicylic  acid  added  to  the  solution  of  a  ferric  salt  containing  no  free  mineral 
acid  gives  a  violet  color.  Useful  for  detecting  iron  in  alum  and  similar  products. 

Ferrous  Iron.  Potassium  Ferricyanide,  K3Fe(CN)6,  gives  a  blue  color 
with  solutions  of  ferrous  salts. 

Distinction  between  Ferrous  and  Ferric  Salts. 

KCNS  gives  red  color  with  Fe'"  and  no  color  with  Fe''. 

K3Fe(CN)6  gives  a  blue  color  with  Fe"  and  a  brown  or  green  with  Fe'". 

NH4OH,  NaOH  or  KOH  precipitates  red,  Fe(OH)3  with  Fe"'  and  white, 
Fe(OH)2  with  Fe"  turning  green  in  presence  of  air  due  to  oxidation.3 

Sodium  peroxide  produces  a  reddish-brown  precipitate  of  Fe(OH)3  with 
either  ferrous  or  ferric  salt  solutions,  the  former  being  oxidized  to  the  higher 
valence  by  the  peroxide.  Chromium  and  aluminum  remain  in  solution,  if  present 
in  the  sample. 

ESTIMATION 

Iron  is  so  widely  diffused  in  nature  that  its  determination  is  necessary  in 
practically  all  complete  analyses  of  ores,  rocks,  minerals,  etc.  It  is  especially 
important  in  the  evaluation  of  iron  ores  for  the  manufacture  of  iron  and  steel. 
Among  the  ores  of  iron  the  following  are  more  common : 

Oxides.  Red  hematite,  Fe203;  brown  hematite,  2Fe203-3H20;  black  mag- 
netite or  magnetic  iron  ore,  Fe304.  Ferric  oxide  with  varying  amounts  of  water 

Circular  35  (2d  Ed.)  U.  S.  Bureau  of  Standards. 
2  D.  Van  Nostrand's  Chemical  Annual. — Olsen. 

8  The  green  salt  is  a  hydrate  of  Fe3O4.  The  white  precipitate  can  be  obtained  in 
absence  of  air  or  by  using  H2S03  to  take  up  oxygen  in  solution. 

210 


IRON  211 

forms  the  substances  known  as  hematite,  gothite,  limonite,  yellow  ochre,  bog 
iron  ore. 

Sulphide.     Iron  pyrites  or  "fool's  gold,"  FeS2;  pyrrhotite,  FeS. 

Carbonates.  Spatic  iron  ore,  FeC03;  combined  with  clay  in  clay  ironstone 
with  bituminous  material  as  " black  band." 

Iron  is  determined  in  the  cinders  and  in  iron  ore  briquettes  from  burned  iron 
pyrites,  by-products  of  sulphuric  acid. 

It  is  found  as  an  impurity  in  a  large  number  of  commercial  salts  and  in  the 
mineral  acids. 

Preparation  and  Solution  of  the  Sample 

The  material  should  be  carefully  sampled  and  quartered  down  according 
to  the  general  procedure  for  sampling.  Ores  should  be  ground  to  pass  an  80- 
mesh  sieve.  In  analysis  of  metals,  both  the  coarse  and  fine  drillings  are  taken. 

The  following  facts  regarding  solubility  should  be  remembered:  The  element 
is  soluble  in  hydrochloric  acid  and  in  dilute  sulphuric  acid,  forming  ferrous 
salts  with  liberation  of  hydrogen.  It  is  insoluble  in  concentrated,  cold  sulphuric 
acid,  but  is  attacked  by  the  hot  acid,  forming  ferric  sulphate  with  liberation  of 
S02.  Moderately  dilute,  hot  nitric  acid  forms  ferric  nitrate  and  nitrous  oxide; 
the  cold  acid  gives  ferrous  nitrate  and  ammonium  nitrate  or  nitrous  oxide  or 
hydrogen.  Cold,  concentrated  nitric  acid  forms  " passive  iron,"  which  remains 
insoluble  in  the  acid.  The  oxides  of  iron  are  readily  soluble  in  hydrochloric  acid, 
if  not  too  strongly  ignited,  but  upon  strong  ignition  the  higher  oxides  dissolve 
with  extreme  difficulty.  They  are  readily  soluble,  however,  by  fusion  with 
acid  potassium  sulphate  followed  by  an  acid  extraction.  Silicates  are  best 
dissolved  by  hot  hydrochloric  acid  containing  a  few  drops  of  hydrofluoric  acid 
or  by  fusion  with  sodium  and  potassium  carbonates,  followed  by  hot  hydro- 
chloric acid. 

Soluble  Iron  Salts.  Water  solutions  are  acidified  with  HC1  or  H2S04,  so 
as  to  contain  about  3%  of  free  acid. 

Ores.     The  samples  should  be  pulverized  to  pass  an  80-  to  100-mesh  sieve. 

Sulphides,  Ores  Containing  Organic  Matter.  One-  to  5-gram  samples 
should  be  roasted  in  a  porcelain  crucible  over  a  Bunsen  flame  for  about  half 
an  hour,  until  oxidized.  The  oxide  is  now  dissolved  as  directed  in  the  following 
procedure. 

Oxides,  Including  Red  and  Brown  Hematites,  Magnetic  Iron  Ore,  Spatose 
Iron  Ore,  Roasted  Pyrites,  and  Iron  Ore  Briquettes.  One  to  5  grams 
of  the  ore,  placed  in  a  400-cc.  beaker,  is  dissolved  by  adding  twenty  times 
its  weight  of  strong  hydrochloric  acid  with  a  few  drops  of  5%  stannous  chloride 
solution.  Addition  of  4  or  5  drops  of  HF  is  advantageous  if  small  amounts 
of  silica  are  present.  The  solution  is  covered  with  a  watch-glass  and  heated  to 
80  or  90°  C.  until  solution  is  complete.  Addition  of  more  stannous  chloride 
may  be  necessary,  as  this  greatly  assists  solution.  An  excess  sufficient  to  com- 
pletely decolorize  the  solution  necessitates  reoxidation  with  hydrogen  peroxide, 
hence  should  be  avoided.  If  a  colored  residue  remains,  it  should  be  filtered 
off,  ignited  and  fused  with  a  mixture  of  Na2C03  and  K2C03  in  a  platinum  cru- 
cible. The  fusion  dissolved  in  dilute  HC1  is  added  to  the  main  filtrate. 

NOTE  .  The  ore  placed  in  a  porcelain  boat  in  a  red-hot  combustion  tube  may  be 
reduced  with  hydrogen  (taking  precaution  first  to  sweep  out  oxygen  with  CO2)  and 
after  cooling  in  an  atmosphere  of  hydrogen  the  reduced  iron  may  be  dissolved  in  acid 
and  titrated. 


212  IRON 

Iron  Silicates.  One  to  5  grams  of  the  material,  placed  in  a  deep  plati- 
num crucible,  is  treated  with  ten  times  its  weight  of  60%  HF  and  3  to  4  drops 
of  cone.  H2S04.  The  mixture  is  evaporated  to  near  dryness  on  the  steam  bath 
and  taken  up  with  dilute  sulphuric  acid  or  hydrochloric  acid.  The  latter  acid 
is  the  best  solvent  for  iron. 

Fusion  with  Potassium  Bisulphate.  The  sample  is  mixed  with  ten  times 
its  weight  of  the  powdered  bisulphate  and  2-3  cc.  of  concentrated  sulphuric  acid 
added.  A  porcelain  or  silica  dish  will  do  for  this  fusion.  The  fusion  should 
be  made  over  a  moderate  flame  and  cooled  as  soon  as  the  molten  liquid  becomes 
clear.  Complete  expulsion  of  S03  should  be  avoided.  It  may  be  necessary 
to  cool  and  add  more  cone,  sulphuric  acid  to  effect  solution.  Iron  and  alumina 
completely  dissolve,  but  silica  remains  undissolved.  The  melt  is  best  cooled  by 
pouring  it  on  a  large  platinum  lid. 

Fusion  with  Carbonates  of  Sodium  and  Potassium.  The  residues  insoluble 
in  hydrochloric  acid  are  fused  with  5  parts  by  weight  of  the  fusion  mixture 
(NaaCOa+K^COs)  in  a  platinum  crucible.  The  M6ker  blast  will  be  necessary. 
When  the  effervescence  has  ceased  and  the  melt  has  become  clear,  the  crucible 
is  removed  from  the  flame,  a  platinum  wire  inserted  and  the  melt  cooled.  Upon 
gently  reheating,  the  fuse  may  be  readily  removed  by  the  wire  in  a  convenient 
form  for  solution  in  dilute  hydrochloric  acid. 

The  bisulphate  fusion  is  recommended  for  fusion  of  residues  high  in  iron 
and  alumina.  It  is  an  excellent  solvent  for  ignited  oxides  of  these  elements. 
The  carbonate  fusions  are  adapted  to  residues  containing  an  appreciable  amount 
of  silica. 

Iron  and  steel  are  best  dissolved  in  hydrochloric  acid  with  a  few  drops  of 
nitric  acid.  The  iron  hydroxide  should  be  precipitated  or  the  solution  taken  to 
dryness  to  expel  the  nitric  acid  followed  by  resolution  in  dilute  hydrochloric 
acid  or  sulphuric  acid. 

The  finer  the  material  the  more  rapid  its  solution  is  a  fact  that  should  be  remem- 
bered in  all  cases. 


IRON  213 

GRAVIMETRIC   METHODS    FOR   THE   DETERMINATION 

OF   IRON 

The  gravimetric  determination  of  iron  may  be  made  from  solutions  practi- 
cally free  from  other  metals.  A  number  of  elements  such  as  phosphorus, 
arsenic,  molybdenum,  tungsten,  vanadium,  and  the  like,  form  fairly  stable 
compounds  with  iron  in  neutral  or  slightly  alkaline  solutions,  whereas  others, 
such  as  lead,  copper,  nickel,  cobalt,  sodium,  and  potassium  may  be  occluded 
in  the  ferric  hydrate  precipitate  and  are  removed  only  with  considerable  diffi- 
culty. Aluminum,  chromium,  and  several  of  the  rare  earths  are  precipitated 
with  iron,  if  present.  These  facts  taken  into  consideration,  the  volumetric 
methods  are  generally  preferred  as  being  more  rapid  and  trustworthy. 

Determination  of  Iron  as  Fe2Oa 

Iron  is  precipitated  as  the  hydroxide  and  ignited  to  the  oxide,  Fe203,  in 
which  form  it  is  weighed. 

Reactions.    FeCl3+3NH4OH  =Fe(OH)3+3NH4Cl. 
2Fe(OH)3+heat  =Fe203+3H20. 

Procedure.  One-gram  sample  or  a  larger  amount  of  material  if  the  iron 
content  is  low,  is  brought  into  solution  with  hydrochloric  acid,  aqua  regia,  or  by 
fusion  with  potassium  carbonate  or  potassium  acid  sulphate,  as  the  case  may 
require.  Silica  is  filtered  off  and  the  acid  solution  treated  with  H2S  if  members 
of  that  group  are  present.  The  filtrate  is  boiled  to  expel  H2S  and  the  iron 
oxidized  to  ferric  condition  by  boiling  with  5  cc.  concentrated  nitric  acid. 

Absence  of  Aluminum  and  Chromium.  About  1  gram  of  ammonium 
chloride  salt  or  its  equivalent  in  solution  is  added,  the  volume  made  to  about 
200  cc.  and  ammonium  hydroxide  added  in  slight  excess  to  precipitate  Fe(OH)3. 
The  solution  is  boiled  for  about  five  minutes,  then  filtered  through  an  ashless 
filter.  (S.  &  S.  589  is  good  for  this  purpose.) 

If  Aluminum  and  Chromium  are  Present.  In  place  of  ammonium  hydroxide 
powdered  sodium  peroxide  is  added  in  small  portions  until  the  precipitate  first 
formed  clears,  the  solution  being  cold  and  nearly  neutral.  It  is  diluted  to  about 
300  cc.  and  boiled  ten  to  fifteen  minutes  to  precipitate  the  iron.  Aluminum  and 
chromium  are  in  solution.  (Mn  will  precipitate  with  Fe,  if  present.)  The 
precipitate  is  filtered  onto  a  rapid  filter  and  washed  with  hot  water. 

Second  Precipitation.  In  either  case  dissolve  the  precipitate  with  the 
least  amount  of  hot  dilute  hydrochloric  acid  and  wash  the  paper  free  of  iron. 
Add  a  few  cc.  of  10%  ammonium  chloride  solution  and  reprecipitate  the  hydroxide 
of  iron  by  adding  an  excess  of  ammonium  hj'droxide,  the  volume  of  the  solu- 
tion being  about  200  cc.  Washing  the  precipitate  by  decantation  is  advisable. 
Three  such  washings,  100-cc.  portions,  followed  by  two  or  three  on  the  filter 
paper,  will  remove  all  impurities. 

Ignition.  The  precipitate  is  ignited  wet  over  a  low  flame,  gradually  in- 
creasing the  heat.  Blasting  is  not  recommended,  as  the  magnetic  oxide  of 
iron,  Fe304,  will  form  with  high  heating.  The  oxide  heated  gently  appears  a 
reddish-brown.  Higher  heat  gives  the  black  oxide,  Fe304.  Twenty  minutes' 
ignition,  at  red  heat,  is  sufficient. 


214  IRON 

The  crucible,  cooled  in  a  desiccator,  is  weighed  and  Fe2O3  obtained. 

Factors.    Fe203  X  0.6994  =  Fe. 
Fe203X  0.8998  =FeO. 

Precipitation  of  Iron  with  "  Cupferron,"  Amino  nitrosophenyl- 

hydroxylamine 1 

By  this  procedure  iron  may  be  precipitated  directly  in  acid  solution  in 
presence  of  a  number  of  elements.  Mercury,  lead,  bismuth,  tin,  and  silver 
may  be  partially  precipitated.  Copper  precipitates  with  iron,  but  may  be 
easily  removed  by  dissolving  it  out  with  ammonia.  The  method  is  especially 
adapted  for  separation  of  iron  from  aluminum,  nickel,  cobalt,  chromium,  cadmium, 
and  zinc. 

Procedure.  The  solution  containing  the  iron  is  made  up  to  100  cc.  and  20 
cc.  of  concentrated  hydrochloric  acid  added.  To  this  cool  solution  (room 
temperature)  Baudisch's  reagent,  cupferron,  is  slowly  added  with  constant 
stirring,  until  no  further  precipitation  of  iron  takes  place,  and  crystals  of  the 
reagent  appear.  The  iron  precipitate  is  a  reddish-brown.  Copper  gives  a 
grayish-white  flocculent  compound.  An  excess  of  the  reagent  equal  to  one-fifth 
of  the  volume  of  the  solution  is  now  added,  the  precipitate  allowed  to  settle 
for  about  fifteen  minutes,  then  poured  into  a  filter  paper  and  washed,  first  with 
2N.  HC1,  followed  by  water,  then  with  ammonia  and  finally  with  water.  The 
drained  precipitate  is  slowly  ignited  in  a  porcelain  or  platinum  crucible  and  the 
residue  weighed  as  Fe203 

Fe203X  0.6994  =Fe. 

NOTES.  Baudisch's  reagent,  amino  nitrosophenyl-hydroxylamine  (cupferron),  is 
made  by  dissolving  6  grams  of  the  salt  in  water  and  diluting  to  100  cc.  The  reagent 
keeps  for  a  week  if  protected  from  the  light.  It  decomposes  io  the  light,  forming 
nitrobenzine.  Turbid  solutions  should  be  filtered. 

The  precipitates  of  copper  or  iron  are  but  slowly  attacked  by  twice  normal  hydro- 
chloric acid  in  the  cold,  but  decomposed  by  hot  acid,  hence  the  solution  and  reagent 
should  be  cold. 

Cold,  dilute  potassium  carbonate  solution,  or  ammonium  hydroxide,  have  no  action 
on  the  iron  precipitate;  the  copper  compound  dissolves  readily  in  ammonia.  Alkaline 
hydroxide  causes  rapid  decomposition. 

The  precipitation  is  best  made  in  comparatively  strong  acid  solutions  (HC1,  H2SO4, 
or  acetic  acid). 


VOLUMETRIC  DETERMINATION  OF  IRON  IN  ORES  AND 
METALLURGICAL  PRODUCTS 

General   Considerations.     Two  general  procedures  are  commonly  employed 
in  the  determination  of  iron. 

A.  Oxidation  of  ferrous  to  ferric  condition  by  standard  oxidizing  agents. 

B.  Reduction  of  ferric  iron  to  ferrous  condition. 

The  sample  is  dissolved  as  directed  under  Preparation  and  Solution  of  the 
Sample. 

1O.  Baudisch,  Chem.  Ztg.,   33,  1298,  1905.     Ibid.,  35,  913,  1911.     O.  Baudisch 
and  V.  L.  King,  Jour.  Ind.  Eng.  Chem.,  3,  627,  1911. 


IRON  215 


Determination  of  Iron  by  Oxidation  Methods 

Some  ^modification  of  either  the  dichromate  or  permanganate  methods  is 
commonly  employed  in  the  determination  of  iron  by  oxidation.  To  accomplish 
this  quantitatively,  the  iron  must  be  reduced  to  its  ferrous  condition.  This 
may  be  accomplished  in  the  following  ways : 

1.  Reduction  by  Hydrogen  Sulphide.    During  the  course  of  a  complete  anal- 
ysis of  an  ore,  H2S  is  passed  into  the  acid  solution  to  precipitate  the  members  of  that 
group  (Hg,  Pb,  Bi,  Cu,  Cd,  As,  Sb,  Sn,  Pt,  Au,  Se,  etc.).    The  nitrate  contains  iron 
in  the  reduced  condition  suitable  for  titration  with  either  dichromate  or  per-, 
manganate,  the  excess  of  H2S  having  been  boiled  off.     If  the  expulsion  of  H2S 
is  conducted  in  an  Erlenmeyer  flask  there  is  little  chance  for  reoxidation  of  the 
iron  during  the  boiling.     Reduction  by  H2S  is  very  effective  and  is  frequently 
advisable.    This  is  the  case  when  titanium  is  present,  since  this  is  not  reduced 
by  H2S,  but  by  methods  given  below.    Arsenic,  antimony,  copper,  and  platinum, 
which,  if  present  would  interfere,  are  removed  by  this  treatment. 

Reaction.     2FeCl3+H2S  =2FeCl2+2HCl+S. 

2.  Reduction   with   Stannous   Chloride.     SnCl2   solution   acts   readily   in 
a  hydrochloric  acid  solution  of  the  ore;  the  reduction  of  the  iron  is  easily  noted 
by  the  disappearance  of  the  yellow  color.    The  excess  of  the  reagent  is  oxidized 
to  SnCl4  by  addition  of  HgCl2. 

Reactions.     1.  2FeCl3+SnCl2  =2FeCl3+SnCl4. 

2.  Excess  SnCl2+2HgCl2=SnCl4-h2HgCl  precipitated. 

An  excess  of  SnCl2  is  advisable,  but  a  large  excess  is  to  be  avoided,  as  a 
secondary  reaction  would  take  place,  as  follows:  2SnCl2+2HgCl2=2SnCl4+2Hg. 
This  reaction  is  indicated  by  the  darkening  of  the  solution  upon  the  addition  of 
HgCl2.  Precipitation  of  metallic  mercury  would  vitiate  results.  The  solution- 
should  be  cooled  before  addition  of  mercuric  chloride.  About  15-20  cc.  of  sat- 
urated mercuric  chloride,  HgCl2,  solution  should  be  sufficient. 

3.  Reduction  by  a  Metal  such  as  Test  Lead,  Zinc,  Magnesium,  Cadmium, 
or  Aluminum,  in  Presence  of  Either  Hydrochloric  Acid  or  Sulphuric  Acid. 
The  former  acid  is  preferred  with  the  dichromate  titration,  and  the  latter  with 
the  permanganate.    Two  methods  of  metallic  reduction  are  in  common  use — 
reduction  by  means  of  test  lead,  and  reduction  with  amalgamated  zinc  by  means 
of  the  Jones  reductor. 

(a)  Reduction  with  Test  Lead.  By  this  method  copper  is  precipitated 
from  solution  and  small  amounts  of  arsenic  and  antimony  expelled.  Sufficient 
test  lead  is  added  to  the  acid  ferric  solution  to  completely  cover  the  bottom  of 
the  beaker.  The  solution  is  covered  and  boiled  vigorously  until  the  yellow  color 
has  completely  disappeared,  and  the  solution  is  colorless.  The  reduced  iron 
solution,  cooled,  is  decanted  into  a  600-cc.  beaker,  the  remaining  iron  washed 
out  from  the  lead  mat  by  several  decantations  with  water;  two  or  three  50-cc. 
portions  of  water  should  be  sufficient;  the  washings  are  added  to  the  first  portion. 
If  the  solution  becomes  slightly  colored,  a  few  drops  of  stannous  chloride,  SnCl2, 
solution  are  added,  followed  by  10  cc.  mercuric  chloride,  HgCl2,  solution.  The 
sample  is  now  ready  for  titration. 


216  IRON 

(6)  Reduction  with  Zinc,  Using  the  Jones  Reductor.  The  acid  solution  of 
iron,  preferably  sulphuric  acid,  is  passed  through  a  column  of  amalgamated  zinc.1 
The  hydrogen  evolved  in  presence  of  the  zinc  reduces  the  ferric  iron  to  ferrous 
condition.  The  procedure  is  described  in  detail  under  the  Permanganate  Method 
for  Determination  of  Iron,  page  218.  Titanium  if  present  will  also  be  reduced. 

4.  Reduction  with  Sulphurous  Acid,  Sodium  Sulphite  or  Metabisulphite. 
S02  gas  is  passed  into  a  neutral  solution  of  iron,  since  iron  is  not  reduced 
readily  in  an  acid  solution  by  this  method.  The  excess  S02  is  expelled  by  acidi- 
fying the  solution  and  boiling. 

6.  Reduction  with  potassium  iodide,  the  liberated  iodine  being  expelled  by 
heat. 

In  the  solution  of  the  ore  with  stannous  chloride  and  hydrochloric  acid,  if  an 
excess  of  the  former  has  been  accidentally  added,  it  will  be  necessary  to  oxidize  the 
iron  before  reduction.  This  may  be  accomplished  by  addition  of  hydrogen  peroxide 
until  the  yellow  color  of  ferric  chloride  appears  (or  by  addition  o/KMn04  solution), 
the  excess  H202  may  be  removed  by  boiling.  The  iron  may  now  be  reduced  by  one  of 
the  above  methods. 

Volumetric  Determination  of   Iron  by  Oxidation  with 
Potassium  Dichromate 

Principle.  This  method  depends  upon  the  quantitative  oxidation  of  ferrous 
salts  in  cold  acid  solution  (HC1  or  H2S04)  to  ferric  condition  by  potassium 
dichromate,  the  following  reaction  taking  place : 

6FeCl2+K2Cr207-r-14HCl=6FeCl3+2CrCl3+2KCl+7H20. 

Potassium  ferricyanide  is  used  as  an  outside  indicator.  This  reagent  pro- 
duces a  blue  compound  with  ferrous  salts  and  a  yellowish-brown  with  ferric. 
The  chromic  salt  formed  by  the  reaction  with  iron  colors  the  solution  green. 

Reagents  Required.  Standard  Potassium  Dichromate.  When  oxygen 
reacts  with  ferrous  salts,  the  following  reaction  takes  place : 

6FeCl2+6HCl+ 30  =6FeCl3+3H20. 

Comparing  this  reaction  with  that  of  dichromate,  it  is  evident  that  a  normal 
solution  of  dichromate  contains  one-sixth  of  the  molecular  weight  of  K2Cr207 
per  liter,  namely,  49.033  grams.  For  general  use  it  is  convenient  to  have  two 
strengths  of  this  solution,  N/5  for  ores  high  in  iron  and  N/10  for  products  con- 
taining smaller  amounts. 

Standardization.  For  N/5  solution  9.807  grams  of  the  recrystallized  de- 
hydrated salt  are  dissolved  and  made  up  to  one  liter;  N/10  potassium  dichro- 
mate contains  4.903  grams  of  the  pure  salt  per  liter.  It  is  advisable  to  allow 
the  solution  to  stand  a  few  hours  before  standardization.  The  Sibley  iron 
ore  furnished  by  the  U.  S.  Bureau  of  Standards,  Washington,  D.  C.,  is  recom- 
mended as  the  ultimate  standard.  Other  ores  uniform  in  iron  may  be  standardized 
against  the  Sibley  ore  and  used  as  standards.  The  ore  in  question  contains 
69.20%  Fe  (1914).  For  accurate  work  it  is  desirable  to  use  a  chamber  burette 

1  Amalgamated  zinc  is  best  prepared  by  dissolving  5  grams  of  mercury  in  25  cc. 
of  concentrated  nitric  acid  with  an  equal  volume  of  water,  250  cc.  of  water  are  added 
and  the  solution  poured  into  500  grams  of  shot  zinc,  20-mesh.  When  thoroughly 
amalgamated  the  solution  is  poured  off,  and  the  zinc  dried. 


IKON  217 

with  graduations  from  75  to  90  cc.  in  tenths  and  from  90  to  100  in  twentieths  of 
a  cc.  A  titration  of  90  to  100  cc.  of  the  dichromate  would  require  0.9  to  1.1 
gram  of  iron  for  a  fifth  normal  solution  and  half  this  amount  for  a  tenth  normal 
solution4  of  dichromate.  In  the  first  case  1 A  gram  of  Sibley  iron  ore  should 
be  taken  and  for  N/10  0.7  gram  of  the  ore.  The  ore  is  best  dissolved  in  strong 
HC1,  adding  a  few  drops  of  stannous  chloride  solution  and  heating  just  below 
boiling.  In  case  of  an  ore  or  iron  ore  briquette,  containing  silica  in  an  appre- 
ciable amount,  a  carbonate  fusion  of  the  residue  may  be  necessary.  Reduction 
and  titration  of  the  ore  is  done  exactly  as  prescribed  under  Procedure  below. 

The  equivalent  iron  in  the  ore  divided  by  the  cc.  titration  required  for  com- 
plete oxidation  gives  the  value  in  terms  of  grams  per  cc.,  e.g.,  1.4  gram  of  ore 
containing  69.2%  Fe  required  a  titration  of  95  cc.  K2Cr207  solution,  then, 

1  cc.  =  (69'^L4)^-95  =0.0102  gram  Fe. 
lUU 

Stannous  Chloride.  Sixty  grams  of  the  crystallized  salt  dissolved  in  600 
cc.  of  strong  HC1  and  made  up  to  one  liter.  The  solution  should  be  kept  well 
stoppered. 

Mercuric  Chloride.     Saturated  solution  of  HgCl2  (60  to  100  grams  per  liter), 

Potassium  Ferricyanide,  KsFe(CN)6.  The  salt  should  be  free  of  ferrocyanide, 
as  this  produces  a  blue  color  with  ferric  salts,  which  would  destroy  the  end- 
point.  It  is  advisable  to  wash  off  the  salt  before  using.  A  crystal  the  size  of 
a  pinhead  dissolved  in  50  cc.  of  water  is  sufficient  for  a  series  of  determinations. 
The  solution  should  be  made  up  fresh  for  each  set  of  determinations. 

Apparatus.  Chamber  burette.  This  should  read  from  75  to  90  cc.  in 
tenths  and  from  90  to  100  cc.  in  twentieths  of  a  cc. 

Test  Plate.  The  usual  porcelain  test-plate  with  depressions  may  be  replaced 
by  a  very  simple  and  efficient  test-sheet  made  by  dipping  a  white  sheet  of  paper 
in  paraffin.  The  indicator  does  not  cling  to  this  surface,  the  drops  assuming 
a  spherical  form,  which  renders  the  detection  of  the  end-point  more  delicate. 

Procedure.  Iron  Ores.  The  amount  of  sample  taken  should  be  such  that 
the  actual  iron  present  would  weigh  between  0.9  to  1.1  gram.  This  weight 
can  be  estimated  by  dividing  95  by  the  approximate  percentage  of  iron  present, 
e.g.,  for  50%  Fe  ore  take  •§-§•  =  1.9  gram;  95%  iron  material  would  require  1 
gram,  whereas  20%  Fe  ore  would  require  4.75  grams. 

For  samples  containing  less  than  20%  Fe  it  is  advisable  to  use  N/10  K2Cr207 
solution. 

The  sample  should  be  finely  ground  (80-mesh). 

Solution.  The  hydrochloric  acid  method  for  solution  of  the  oxidized  ore 
with  subsequent  carbonate  fusion  of  the  residue  is  recommended  as  being  suitable 
for  iron  ores,  briquettes,  and  materials  high  in  iron. 

Reduction.  H2S  reduction  is  recommended  in  ores  containing  arsenic  or 
titanium.  SnCl2  in  very  slight  excess,  followed  by  mercuric  chloride,  HgCl2, 
gives  excellent  results  in  absence  of  other  reducible  salts  of  elements,  Cu,  As,  etc. 

Test  Lead.  The  easy  manipulation  and  efficiency  of  this  method  of  reduc- 
tion makes  it  applicable  for  a  large  variety  of  conditions.  The  acid  solution 
preferably,  HC1,  is  diluted  to  about  150  to  200  cc.,  containing  15  to  20  cc.  con- 
centrated hydrochloric  acid  (sp.gr.  1.19).  Sufficient  test  lead  is  added  to  cover 
the  bottom  of  a  No.  4  beaker.  The  solution  covered  is  boiled  vigorously  until 
it  becomes  colorless.  Copper,  if  present,  is  precipitated,  as  well  as  platinum, 


218  IRON 

and  small  amounts  of  arsenic  and  antimony  eliminated  from  the  solution  during 
the  reduction  of  the  iron.  The  cooled  solution  is  poured  into  a  600-cc.  beaker 
and  the  mat  of  lead  remaining  in  the  No.  4  beaker  washed  free  of  iron,  two  or 
three  50-cc.  washings  being  sufficient.  The  main  solution  and  washings  are 
combined  for  titration.  If  the  solution  is  slightly  colored,  due  to  reoxidation 
of  iron,  a  few  drops  of  stannous  chloride  solution  are  added  to  reduce  it,  followed 
by  an  excess  of  HgCl2  solution,  20  to  25  cc.,  and  allowed  to  stand  five  minutes. 

Titration.  The  standard  potassium  dichromate  is  run  into  the  solution  to 
within  5  to  10  cc.  of  the  end-point,  this  having  been  ascertained  on  a  portion 
of  the  sample.  The  dichromate  is  run  in  slowly  near  the  end-reaction,  and 
finally  drop  by  drop  until  a  drop  of  the  solution  mixed  with  a  drop  of  potassium 
ferricyanide  solution  produces  no  blue  color  during  thirty  seconds.  A  paraffined 
surface  is  excellent  for  this  test. 

FeX  100 
Cc.  K2Cr207  multiplied  by  value  per  cc.  =Fe  present  in  sample.  %  = — . 

NOTES.  If  SnCl2  solution  has  been  used  for  reduction  of  the  iron,  it  is  necessary 
to  add  the  HgCl2  rapidly  to  a  cold  solution,  as  slow  addition  to  a  warm  solution  is 
apt  to  precipitate  metallic  mercury. 

In  case  an  excess  of  dichromate  has  been  added  in  the  titration,  as  often  occurs, 
back  titration  may  be  made  with  ferrous  ammonium  sulphate  (NH4)2SO4-FeSO4'6H2O. 
N/10  solution  of  this  reagent  may  be  prepared  by  dissolving  9.81  grams  of  the  clear 
crystals  in  about  100  cc.  of  water,  adding  5  cc.  of  concentrated  H2SO4  and  making  to 
250  cc.  The  solution  should  be  standardized  against  the  dichromate  solution  to  get 
the  equivalent  values,  by  running  the  dichromate  directly  into  the  ferrous  solution. 

The  ferricyanide  indicator  should  be  made  up  fresh  each  time  it  is  required. 

Large  amounts  of  manganese  in  the  iron  solution  titrated  cause  a  brown  coloration, 
which  masks  the  end-point.  Nickel  and  cobalt,  present  in  large  amounts,  are  objection- 
ab'e  for  the  same  reason.  This  interference  may  be  overcon  e  by  using  very  dilute 
acid  solutions  of  ferricyanide  indicator,  so  that  the  insoluble  ferricyanide  of  these 
metals  will  not  form. 

Potassium  Permanganate  Method  for  Determination  of  Iron 

Introduction.  The  method  depends  upon  the  quantitative  oxidation  of 
ferrous  salts  to  the  ferric  condition  when  potassium  permanganate  is  added  to 
their  cold  solution,  the  following  reaction  taking  place : 

10FeS04+2KMn04+8H2S04=5Fe2(S04)3+K2S04+2MnS04+8H20. 

Hydrochloric  acid  in  presence  of  iron  salts  has  a  secondary  reaction  upon 
the  permanganate,  e.g., 

2KMn04+16HCl=2KCl+2MnCl2+8H;:0+10Cl. 

This  reaction  may  be  prevented  by  addition  of  large  amounts  of  zinc  or  man- 
ganous  sulphates  together  with  an  excess  of  phosphoric  acid.1  It  is  preferable, 
however,  to  expel  HC1,  when  this  has  been  used  as  a  solvent,  by  adding  sul- 
phuric acid  and  taking  to  fumes.  The  solution  is  diluted  and  reduced  with  zinc 
and  titrated  as  directed. 

The  reduction  of  ferric  sulphate  is  best  accomplished  by  passing  the  solution 
through  a  column  of  amalgamated  zinc  in  the  Jones  reductor.  In  presence 
of  titanium,  reduction  is  accomplished  by  H2S  in  a  hydrochloric  acid  solution  of 

the  iron. 

1  Jour.  Am.  Chem.  Soc.,  17,  405. 


IRON  219 

Since  potassium  permanganate  enters  into  reaction  with  acid  solutions  of 
antimony,  tin,  platinum,  copper  and  mercury,  when  present  in  their  lower  state 
of  oxidation,  (also  with  manganese  in  neutral  solutions)  and  with  S02,  H2S,  N2O, 
ferrocyaiiides  and  with  most  soluble  organic  bodies,  these  must  be  absent  from 
the  iron  solution  titrated. 

Potassium  permanganate  produces  an  intense  pink  color  in  solution,  so  that 
it  acts  as  its  own  indicator. 

Solutions  Required.  Standard  Permanganate  Solutions.  As  in  case  of 
potassium  dichromate,  it  is  convenient  to  have  two  standard  solutions,  N/5 
andN/10. 

From  the  reaction  given  above  it  is  evident  that  2  KMn04  are  equivalent  to 
5  oxygens,  e.g.,  2KMn04=K204-2MnO-h50,  hence  a  normal  solution  would 
contain  one-fifth  of  the  molecular  weight  of  KMn04  =31.6  grams  of  the  pure  salt. 
Hence  a  N/5  solution  would  contain  6.32  grams  per  liter  and  a  N/10  solution 
3.16  grams. 

Since  commercial  potassium  permanganate  is  seldom  pure,  it  is  necessary  to 
determine  its  exact  value  by  standardization.  This  is  commonly  accomplished 
by  any  of  the  following  methods : 

(a)  By  a  standard  electrolytic  iron  solution. 

(6)  By  ferrous  salt  solution,  e.g.,  (NH4)2S04-FeS04-6H20. 

(c)  By  oxalic  acid  or  an  oxalate. 

Reaction.    2KMn04+5Na2C204+8H2S04 

=K2S04+2MnS04+5Na2S04+10C02+8H20. 

Standardization  of  KMn04  against  sodium  oxalate  is  recommended  as  the 
most  accurate  procedure.  The  salt  has  no  water  of  crystallization  and  is  not 
hygroscopic.  It  can  be  obtained  from  the  Bureau  of  Standards  with  a  guarantee 
of  purity.  Traces  of  moisture  can  be  expelled  by  heating  the  salt  to  120°  C.  for 
two  hours,  then  cooling  in  a  desiccator. 

N/5  Na2C204  contains  13.40  grams  per  liter,  N/10  solution  contains  6.7 
grams.  For  standardization  of  N/5  KMn04,  3.35  grams  of  the  sodium  oxalate 
are  dissolved  in  warm  (70°  C.)  water  (about  200  cc.),  50  cc.  of  2N.  H2S04  are  added 
and  the  solution  made  up  to  250  cc. 

N/5  KMn04  contains  6.32  grams  of  the  salt  per  liter.  It  is  advisable  to 
dissolve  6.4  grams  of  the  salt  in  about  500  cc.  of  hot  water  and  filter  the  solution 
through  asbestos  to  remove  any  dioxide  of  manganese  that  may  be  present, 
as  Mn02  aids  in  the  decomposition  of  KMn04  solution.  The  reagent  should  be 
kept  tightly  sealed  in  a  dark  bottle  well  protected  from  the  light.  This  solution 
should  stand  two  or  three  days  before  standardization. 

To  standardize  the  solution  100  cc.  of  the  N/5  sodium  oxalate  solution  is  heated 
to  about  70°  C.  and  the  permanganate  solution  added  from  a  100-cc.  burette 
very  slowly  in  small  portions  at  a  time,  allowing  the  color  to  fade  after  each 
addition  before  adding  more.  When  within  5-10  cc.  of  the  end-point  the  per- 
manganate solution  should  be  added  drop  by  drop  until  a  faint  permanent  pink 
color  persists. 

Procedure  for  the  Determination  of  Iron  by  the  Jones  Reductor 

Preparation  of  Sample.  Such  an  amount  of  the  sample  is  taken  that  the 
iron  content  is  between  two-  and  three-tenths  of  a  gram  (0.2  to  0.3  gram).  If 
hydrochloric  acid  has  been  required  to  effect  solution,  or  hydrochloric  acid  and 


220 


IRON 


nitric  acid  (25  cc.  :  1  cc.),  as  in  case  of  iron  and  steel,  4  to  5  cc.  cone,  sulphuric 
are  added,  and  the  solution  evaporated  to  small  bulk  on  the  steam  bath  and  to 
S03  fumes  to  remove  hydrochloric  acid.  The  iron  is  taken  up  with  about  50  cc. 
dilute  sulphuric  acid,  1  :  4,  heating  if  necessary,  and  filtering  if  an  insoluble 
residue  remains. 

Preparation  of  the  Reductor.    Cleaning  out  the  apparatus.    See  Fig.  40. 
The  stop-cock  of  the  reductor  is  closed,  a  heavy-walled  flask  or  bottle  is  put  into 

position  at  the  bottom,  and  50  cc.  of  dilute 
sulphuric  acid  poured  into  the  funnel.  The 
cock  is  opened  and  the  acid  allowed  to  flow 
slowly  through  the  zinc  in  the  tube,  applying 
a  gentle  suction.  Before  the  acid  has  drained 
out  of  the  funnel,  50  cc.  of  water  are  added, 
followed  by  50  cc.  more  of  dilute  sulphuric 
acid  and  50  cc.  of  water  in  turn.  The  stop- 
cock is  turned  off  before  the  water  has  drained 
completely  from  the  funnel  so  that  the  zinc  is 
always  covered  by  a  solution  of  acid  or  water. 
This  precaution  should  be  observed  in  all 
determinations  with  the  Jones  reductor  to  pre- 
vent the  inflow  of  air  into  the  column  of  zinc. 
The  contents  of  the  flask  being  emptied  and 
the  flask  replaced,  the  apparatus  is  ready  for 
the  determination  of  the  blank. 

Determination  of  the  Blank.  Fifty  cc. 
of  dilute  sulphuric  acid,  1  : 4,  are  passed 
through  the  reductor,  followed  by  250  cc.  of 
distilled  water,  according  to  the  directions 
given  above.  The  acid  solution  in  the  flask 
is  then  titrated  with  N/10  KMn04  solution. 
If  more  than  3  or  4  drops  of  the  permanga- 
nate are  required,  the  operation  must  be  re- 
peated until  the  blank  titration  does  not 
exceed  this  amount.  The  final  blank  obtained 

should  be  deducted  from  the  regular  determinations  for  iron.  The  end-point  of 
the  titration  is  a  faint  pink,  persisting  for  one  minute. 

Reduction  and  Titration  of  the  Iron  Solution.  The  sample  is  diluted 
to  200  cc.,  and,  when  cold,  is  run  into  the  funnel,  the  stop-cock  opened  and 
the  solution  drawn  slowly  through  the  column  of  zinc  into  the  flask,  about  four 
minutes  being  required  for  200  cc.  of  solution.  Before  the  funnel  has  com- 
pletely drained,  rinsings  of  the  vessel  which  contained  the  sample  are  added; 
two  50-cc.  portions  are  sufficient,  followed  by  about  50  cc.  of  water.  The 
stop-cock  is  closed  before  the  solutions  have  completely  drained  from  the  funnel. 
Titration.  The  flask  is  removed  and  tenth  normal  solution  of  perman- 
ganate added  until  a  faint  pink  color,  persisting  one  minute,  is  obtained.  The 
blank  is  deducted  from  the  cc.  reading  of  the  burette. 

Cc.  KMnOi  thus  found  multiplied  by  the  value  of  the  reagent  in  terms  of 
N/10  =true  value  of  N/10  KMn04  required  to  oxidize  the  reduced  iron. 

One  cc.  N/10  KMn04  =  .005584  gram  Fe;  or  .007984  gram  Fe208. 


FIG.  40. — Jones  Reductor. 


JRON 


221 


This  weight,  divided  by  the  weight  of  the  sample  taken,  and  multiplied  by 
100  =per  cent  iron,  or  iron  oxide  in  the  sample,  according  to  the  factor  taken 
above. 

4 

Stannous  Chloride  Method  for  Determination  of  Ferric  Iron 

The  procedure  is  based  upon  the  reduction  of  the  yellow  ferric  chloride  to 
the  colorless  ferrous  salt  by  stannous  chloride,  the  following  reaction  taking  place: 

2FeCl3+SnCl2  =2FeCl2+SnCl4. 

The  method  is  of  value  in  estimating  the  quantity  of  ferric  iron  in  presence 
of  ferrous,  where  the  two  forms  are  to  be  determined.  In  order  to  obtain  the 
total  iron  the  ferrous  is  oxidized  by  adding 
a  few  crystals  of  potassium  chlorate  and  tak- 
ing to  dryness  to  expel  chlorine,  and  then 
titrated  with  stannous  chloride. 

The  accuracy  of  the  method  depends 
upon  the  uniformity  of  conditions  of  tem- 
perature, concentration,  etc.,  of  making  the 
run  with  the  sample  and  of  standardizing  the 
stannous  chloride.  The  solution  should  be 
free  from  other  oxidizing  agents,  or  from 
salts  that  give  colored  solutions. 

The  amount  of  iron  in  terms  of  ferric 
oxide  that  can  be  estimated  by  this  procedure 
ranges  from  0.002  gram  to  0.05  gram. 

Reagents.  Stannous  Chloride  Solution. 
The  reagent  is  prepared  by  dissolving  2  grams 
of  stannous  chloride  crystals  in  hot  concen- 
trated hydrochloric  acid  and  making  up  to 
1  liter.  The  solution  should  be  kept  in  a 
dark  bottle  to  which  the  titrating  burette  is 
attached  in  such  a  way  that  the  liquid  may 
be  siphoned  out  into  this,  as  shown  in  the 
illustration,  Fig.  41.  The  air  entering  the 
bottle  passes  through  phosphorous  or  pyro- 

gallic  acid  to  remove  the  oxygen.  In  this  way,  protected  from  the  air,  the 
reagent  will  keep  nearly  constant  for  several  weeks.  It  is  advisable,  however,  to 
restandardize  the  solution  about  every  ten  to  fifteen  days.  One  cc.  will  be  equiv- 
alent to  about  0.001  gram  Fe. 

Standard  Iron  Solution.  8.6322  grams  of  ferric  ammonia  alum  is  dissolved 
in  dilute  hydrochloric  acid  and  made  up  to  one  liter.  The  iron  is  determined  in 
100-cc.  portions  by  the  dichromate  method.  One  cc.  will  contain  about  0.001 
gram  Fe. 

Procedure.  To  the  sample  in  a  casserole  is  added  25  cc.  of  concentrated 
hydrochloric  acid  and  an  equal  volume  of  water.  The  resulting  solution  is 
heated  to  boiling  and  quickly  titrated  with  the  stannous  chloride  reagent, 
until  the  yellow  color  fades  out  and  the  solution  becomes  colorless. 

NOTE.  The  titration  should  be  done  quickly,  as  the  iron  will  reoxidize  on  standing 
and  the  solution  again  become  yellow.  The  true  end-point  is  the  first  change  to  a 
colorless  solution. 


Heavy  Wat!  Tube 
with  small  bore 


Pressure  release 
tube.  Finger  placed 
over  opening  during 
ng  of  burette 


Valve 


Rubber 
Bulb 


Valve 
••Opening 
La rqe  test  tube 
having  interior 
wall  coated  with 
phosphorus 


Standard 
•Stannous 
Chloride 


FIG.   41. — Apparatus  for  Stannous 
Chloride  Titration  of  Iron. 


222  IRON 

COLORIMETRIC   METHODS   FOR  THE  DETERMINATION   OF 
SMALL  AMOUNTS   OF   IRON 

Iron  Traces.     Sulphocyanate  (Thiocyanate)  Method1 

Introduction.  By  this  method  1  part  of  iron  may  be  detected  in  50  million 
parts  of  water.  The  presence  of  free  mineral  acid  increases  the  sensitiveness 
of  the  method,  so  that  it  is  especially  applicable  to  the  determination  of  small 
amounts  of  iron  in  mineral  acids.  It  is  available  in  presence  of  many  of  the 
ordinary  metals  and  in  presence  of  organic  matter.  Silver,  copper,  cobalt,  mer- 
curic chloride,  however,  interfere. 

Nitric  acid  gives  a  color  with  sulphocyanates  that  may  be  mistaken  for 
iron. 

This  method,  like  the  stannous  chloride  method,  determines  only  the  ferric 
iron.  It  is  based  on  the  fact  that  ferric  iron  and  an  alkali  sulphocyanate, 
ammonium  or  potassium  sulphocyanates,  in  an  acid  solution  gives  a  red  color, 
the  intensity  of  which  is  proportional  to  the  quantity  of  iron  present.  The 
color  is  due  to  the  formation  of  the  compound,  Fe(CNS)3-9KCNS-4H20. 

Reagents  Required.  Standard  Iron  Solution.  A  ferric  solution,  the  iron 
content  of  which  has  been  determined,  is  diluted  and  divided  so  as  to  obtain 
0.0004  gram  Fe.  This  is  made  up  to  2  liters  with  water  containing  200  cc.  of 
iron-free,  C.P.  H2S04.  One  hundred  cc.  of  this  solution,  together  with  10  cc. 
of  normal  ammonium  sulphocyanate  solution,  is  used  as  a  standard.  One 
hundred  cc.  contains  0.00002  gram  Fe. 

Normal  sulphocyanate  contains  76.1  grams  of  NH4CNS  per  liter. 

Procedure.  The  weighed  sample,  1  to  10  grams,  or  more  if  necessary,  is 
dissolved  in  dilute  H2S04  and  oxidized  by  adding  dilute  permanganate,  KMn04, 
solution  drop  by  drop  until  a  faint  pink  color  is  obtained.  The  sample  is  diluted 
to  exactly  100  cc.  and  is  poured  into  a  burette  graduated  to  ^  cc.  Two 
colorless  glass  cylinders  of  the  100-cc.,  Nessler  type  are  used  for  comparison 
of  standard  and  sample.  Into  one  cylinder  is  poured  100  cc.  of  the  standard 
solution,  made  as  directed  above.  Into  the  second  cylinder  containing  10  cc. 
of  sulphuric  acid  with  10  cc.  ammonium  sulphocyanate,  NH4CNS,  diluted  to 
60  or  70  cc.,  the  sample  is  run  from  the  burette  until  the  depth  of  the  color 
thus  produced  on  dilution  to  100  cc.  exactly  matches  the  standard.  From  the 
number  of  cc.  used  the  weight  of  the  sample  is  calculated.  One  hundred  cc. 
of  the  standard  contains  0.00002  gram  Fe. 

Dividing  the  weight  of  iron  in  the  standard  by  the  weight  of  sample  used 
and  multiplying  by  100  gives  the  per  cent  of  iron  in  the  sample. 

NOTES.  If  other  metals  are  present,  that  form  two  series  of  salts,  they  must  be  in 
the  higher  stare  of  oxidation,  or  the  color  is  destroyed.  (Sutton.)  Oxalic  acid,  if  pres- 
ent, destroys  the  color.  Oxidation  with  KMnO4  or  KC1O3  with  subsequent  removal  of 
C12  prevents  this  interference.  (Lunge,  C.  N.,  73,  250.) 

Chlorides  of  the  alkaline  earths  retard  or  prevent  the  sulphocyanate  reaction. 
(Weber,  C.  N.,  47,  165.) 

The  colorimeter  used  for  the  determination  of  minute  quantities  of  lead  would  serve 
admirably  for  the  determination  of  traces  of  iron  by  the  sulphocyanate  method. 

Anids,  hydrochloric  or  sulphuric  (diluted),  may  be  added  directly  to  the  ammonium 
sulphocyanate  solution. 

i  Thomson,  ,T.  C.  S.,  493,  1885,  and  C.  N.,  51,  259.  Kruss  and  Moraht,  C.  N.,  64, 
255.  Davies,  C.  N.,  8,  163. 


IRON 


223 


Salicylic  Acid  Method  for  Determining  Small  Amounts  of  Iron l 

Salicylic  acid  produces  an  amethyst  color  with  neutral  solutions  of  ferric 
salts,  the  depth  of  the  color  being  proportional  to  the  concentration  of  the  ferric 
iron  in  tfhe  solution.  The  reaction  is  useful  in  determining  small  amounts  of 
iron  in  neutral  salts,  such  as  sodium,  ammonium,  or  potassium  alums,  sulphates, 
or  chlorides,  zinc  chloride,  etc.  Phosphates,  fluorides,  thiosulphates,  sulphites, 
bisulphites  and  free  mineral  acids  should  be  absent.  The  sample  should  not 
contain  over  0.0002  gram  iron,  as  the  depth  of  color  will  then  be  too  deep  for 
colorimetric  comparisons.  As  low  as  0.00001  gram  ferric  iron  may  be  detected. 
Ferrous  iron  produces  no  color  with  the  reagents,  hence  the  procedure  serves 
for  determining  ferric  iron  in  presence  of  ferrous. 

The  material  is  dissolved  in  20  cc.  of  pure  water,  the  sample  filtered  if  cloudy, 
and  transferred  to  a  Nessler  tube.  Dilute  potassium  permanganate  solution 
is  added  until  a  faint  pink  color  is  produced  and  then  5  cc.  of  a  saturated  solution 
of  salicylic  acid.  (The  reagent  is  filtered  and  the  clear  solution  used.)  Com- 
parison is  made  with  standard  solutions  containing  known  amounts  of  ferric 
iron,  the  standards  containing  the  same  reagents  as  the  sample.  If  desired 
the  standard  iron  solution  (0.086  gram  ferric  ammonium  alum,  clear  crystals,  dis- 
solved in  water  containing  2  cc.  of  dilute  sulphuric  acid  and  made  to  1000  cc., 
each  cc.  contains  approximately  0.00001  gram  Fe"')  is  added  from  a  burette 
to  5  cc.  of  salicylic  acid  diluted  to  25  cc.  in  a  Nessler  tube,  until  the  color  of  the 
standard  matches  the  sample.  A  plunger  is  used  to  stir  the  liquids. 

TECHNICAL  ANALYSIS   OF   IRON   AND   STEEL 

The  elements  carbon,  manganese,  phosphorus,  sulphur,  and  silicon  are  in- 
variable constituents  of  iron  and  steel,  and  are  always  included  in  an  analysis. 
Copper  and  arsenic  are  sometimes  found;  aluminum,  chro- 
mium, nickel,  molybdenum,  tin,  titanium,  tungsten,  vana- 
dium, and  zinc  occur  in  special  alloy  steels.  Minute  traces  of 
oxygen,  hydrogen,  and  of  many  other  elementary  constituents 
frequently  are  present,  but  are  of  so  little  importance  that 
they  are  seldom  considered  in  an  analysis. 

Our  attention  is  drawn  in  this  chapter  to  the  more  impor- 
tant constituents,  whose  estimation  is  required  in  the  daily 
routine  analysis  of  a  steel  works  laboratory.  The  elements 
considered  are  carbon — carbide  or  combined  carbon  and  graph- 
itic carbon,  manganese,  phosphorus,  sulphur,  and  silicon. 
Determination  of  the  elements  of  special  alloy  steels  contain- 
ing aluminum,  chromium,  nickel,  titanium,  tungsten,  vana- 
dium, etc.,  are  given  in  the  chapters  on  the  elements  in  question; 
for  example  the  determination  of  vanadium  in  steel  will  be 
found  in  the  chapter  on  Vanadium,  chromium  and  copper  in 
the  chapters  on  Chromium  and  Copper,  etc. 

As  is  generally  the  case,  a  large  number  of  determinations 
are  required  in  the  steel  works  laboratories  and  it  is  not  an 
uncommon  thing  for  one  man  to  turn  out  50  to  100  determina- 
tions a  day.  To  accomplish  this,  simple  and  rapid  procedures  are  required. 
When  the  metal  is  unusually  high  in  an  undesirable  constituent  it  is  indicated 
1  Method  of  W.  S.  Allen,  by  courtesy  of  the  General  Chemical  Company. 


224  IRON 

by  the  test,  and  a  confirmation  of  the  result  is  obtained  by  an  additional  test, 
exercising  extreme  care,  and  using  a  procedure  giving  results  of  the  highest 
accuracy.  Fortunately  the  analysis  of  steel  has  received  considerable  attention 
and  rapid  methods  have  been  worked  out  which  are  extremely  accurate. 

The  procedures  briefly  outlined  have  proven  of  value  to  analysts  of  iron 
and  steel.  While  in  charge  of  the  laboratory  at  Baldwin  Locomotive  Works, 
the  author  found  that  a  skilled  analyst  was  able  to  turn  out  125  determinations 
of  combined  carbon,  or  100  of  manganese,  or  of  sulphur,  or  50  determinations 
of  phosphorus,  or  25  determinations  of  silicon  per  day  by  the  procedures  given. 
This  necessitates  the  use  of  a  large  number  of  beakers  and  flasks,  ample  desk 
room,  individual  balances,  hot  plates,  and  hoods  to  accommodate  a  dozen  to 
two  dozen  beakers  or  flasks  at  a  time,  and  a  carefully  planned  system. 

The  dividing  pipette,  shown  in  Fig.  42,  is  useful  for  adding  a  definite  amount 
of  reagent  to  the  sample. 

In  addition  to  the  short  methods,  we  include  the  procedures  recommended 
by  the  U.  S.  Bureau  of  Standards,  for  cases  where  accuracy  is  essential  and 
time  a  secondary  consideration. 

Preparation  of  the  Sample 

The  metal  is  sampled  by  drilling  with  a  clean  twist  drill,  using  no  water 
or  oil. 

Hard  grades  of  pig  iron,  chilled  iron,  ferromanganese,  quenched  steel,  etc., 
are  broken  down  to  a  coarse  powder  in  a  chilled  steel  mortar. 

Combined  or  Carbide  Carbon — Colorimetric  Method 

Rapid  Method.  0.2  gram  of  well-mixed  drillings  is  placed  in  a  test-tube 
6Xf  ins.  and  4  to  10  cc.  of  nitric  acid  (sp.gr.  1.2)  added  from  a  burette,  the 
test-tube  being  placed  in  cold  water  to  prevent  too  violent  action.  The  amount 
of  acid  added  is  governed  by  the  carbon-content  of  the  steel  (see  chapter  on 
Carbon,  page  108).  After  the  violent  action  has  ceased,  the  tube  is  placed  in  a 
specially-designed  water  bath,  the  water  heated  to  boiling  and  boiled  for  twenty 
minutes  or  more  until  the  solution  in  the  tube  has  become  perfectly  clear. 
The  sample  is  now  removed,  washed  into  a  color  carbon  tube  and  compared  with 
a  standard  steel  of  the  same  class  of  material  as  that  examined.  Full  details  of 
the  procedure  may  be  found  in  the  chapter  on  Carbon. 

Iron  and  steel  containing  graphite  must  be  filtered  before  making  comparisons. 
The  solution,  diluted  with  one-half  its  volume  of  water,  is  filtered  through  a  small 
filter  paper  into  a  test-tube.  The  residue  is  washed  with  a  fine  jet  of  distilled 
water  until  free  of  color.  The  filtrate  is  compared  with  a  standard  sample  of 
similar  composition  treated  in  the  same  way. 

Steel  containing  chromium,  copper,  nickel,  and  elements  yielding  a  colored 
solution  should  not  be  examined  by  the  colorimetric  methods. 

Method  of  the  Bureau  of  Standards.  Total  and  graphitic  carbon  are 
determined  and  the  difference  taken  as  combined  carbon. 


IRON  225 

Specifications  for  Combined  Carbon. 

Material.  Per  cent  Carbon. 

Boiler  rivets 0.15 

Seamless  boiler  tubes 0 . 18-0 . 25 

Boiler  and  fire-box  plates 0. 15-0.25 

Cylinder  grade  pig  iron 0.25-0. 50 

Forged  and  rolled  steel  wheels 0. 70-0. 75 

Steel  blooms  for  forgings,  open  hearth,  basic 0.40  0.55 

Steel  blooms  for  forgings,  acid 0 . 35-0 . 40 

Bolt  steel 0 . 22-0 . 28 

Spring  steel 0.90-1.10 

Crank  axles  forged 0. 35-0. 55 

Casting not  over  0 . 35 

Tire  steel 0.65-0.75 

Floor  grade  pig  iron not  over  0 . 40 

i 
Total  Carbon 

The  determination  is  required  for  an  accurate  estimation  of  carbon  where 
the  color  test  indicates  the  carbon  content  outside  the  limits  of  requirement, 
or  in  cases  where  interfering  substances  are  present.  In  material  where  the 
carbon  content  is  of  extreme  importance,  the  color  method  is  not  used.  Details 
of  the  procedure  for  determining  carbon  by  direct  combustion  are  given  in 
the  chapter  on  Carbon.  The  following  procedure  is  recommended  by  the 
Bureau  of  Standards: 

(a)  In  Irons.  Two  grams  of  iron  are  mixed  with  about  twice  the  weight 
of  purified  ferric  oxide.  The  mixture  is  placed  in  a  platinum  boat,  which  is 
lined  with  a  suitable  bed  material,  and  is  burned  in  a  current  of  oxygen,  as 
described  below. 

(6)  In  Steels.  The  method  is  the  same  as  for  irons  with  omission  of  the 
ferric  oxide  mixture. 

Details  of  Direct  Combustion  Method.  Furnaces  and  Temperature  of 
Burning.  Porcelain  tubes  wound  with  "nichrome"  wire,  provided  with  suit- 
able heat  insulation  and  electrically  heated,  are  used,  and  readily  give  tem- 
peratures to  1100°  C.  Type  FB  301  Hoskins  tube  furnace  and  the  hinged 
type,  Fig.  326,  are  satisfactory.  The  temperature  control  is  by  means  of  an 
ammeter  and  rheostat  in  series  with  the  furnace,  with  occasional  check  by  a 
thermocouple. 

Boats  and  Lining.  Platinum  boats  provided  with  a  long  platinum  wire  for 
manipulation  in  the  tube  are  mostly  used;  alundum  ones  occasionally.  The  bed 
or  lining  on  which  the  steel  rests  is  90-mesh  "RR  alundum,  alkali-free,  specially 
prepared  for  carbon  determination."  A  layer  of  this  alundum  is  also  placed 
in  the  bottom  of  the  combustion  tube  to  prevent  the  boat  sticking  to  the  glaze. 
A  platinum  cover  for  the  boat  is  sometimes  used,  and  is  essential  when  the 
combustion  is  forced. 

The  nature  and  quality  of  the  bed  material  are  matters  of  great  importance. 
Alumina  as  prepared  from  the  sulphate  or  from  alum  may  not  be  free  from 
sulphate  or  alkali,  both  of  which  have  given  serious  trouble  at  the  Bureau.  The 
alkali,  if  present,  may  not  manifest  itself  by  an  alkaline  reaction  until  after 
one  or  two  combustions  have  been  made,  using  the  same  bed  material.  Even 
the  ordinary  white  " alundum"  on  the  market  carries  a  few  hundredths  of  1% 
of  alkali.  Iron  oxide  has  been  tried,  and  when  pure  should,  apparently,  give  good 


226  IRON 

service.  As  yet,  however,  it  has  been  difficult  to  obtain  or  prepare  acceptable 
material  for  use  with  steels.  Quartz  sand  gives  rise  to  a  fujible  slag,  which 
melting  before  combustion  is  complete,  incloses  bubbles  of  carbon  dioxide  gas. 
This  defect  would  probably  inhere  in  any  other  material  of  an  acid  character. 
The  presence  in  the  silica  bed  after  combustion  of  crystals  which  appear  to  be 
carborundum,  have  occasionally  been  noted.1 

Purity  of  Oxygen.  Blanks.  The  Bureau  makes  its  oxygen  electrolytically, 
and  its  content  of  this  element  is  usually  99  to  99.5%,  and  sometimes  higher. 
Even  with  this  gas  a  slight  blank  is  usually  obtained.  When  running  a  blank, 
in  addition  to  the  usual  precautions,  the  rate  at  which  the  oxygen  is  introduced 
should  be  the  same  as  when  burning  a  sample,  and  the  time  should  be  three  to 
five  times  as  long. 

Method  of  Admitting  Oxygen  and  Rate  of  Combustion.  The  furnace  being 
at  the  proper  temperature,  the  boat  containing  the  sample  is  introduced.  Oxygen 
is  admitted  either  at  once  or  after  the  boat  has  reached  the  temperature  of  the 
furnace,  as  the  operator  prefers,  or  as  the  nature  of  the  steel  may  demand. 
The  rate  of  flow  of  the  oxygen  varies  with  the  absorption  apparatus  used  and 
with  the  preference  of  the  operator,  and  may  be  considerably  more  rapid  when 
absorbing  carbon  dioxide  in  soda  lime  than  in  an  alkaline  solution.  A  rapid 
flow  of  oxygen  also  facilitates  the  burning  of  resistant  samples.  A  continuous 
forward  movement  of  the  gas  current  is  maintained  at  all  times.  The  time 
for  a  determination  varies,  of  necessity,  with  the  nature  of  the  sample  and  the 
rate  of  flow  of  the  oxygen,  ranging  from  ten  to  thirty  minutes.  The  endeavor 
is  to  obtain  a  well-fused  oxide.  With  all  samples  close  packing  in  a  small  space 
is  conducive  to  rapid  combustion  and  to  fusion  of  the  resulting  oxide. 

Authorities  differ  as  to  the  advisability  of  allowing  the  oxide  of  iron  to  fuse 
thoroughly.  Even  when  fusion  does  take  place  additional  carbon  dioxide  is 
obtained  very  frequently  by  grinding  the  oxide  and  reburning.  Often  more 
than  one  regrinding  and  reburning  is  necessary  in  order  to  reduce  the  amount 
of  carbon  dioxide  obtained  to  that  of  the  constant  blank. 

Oxides  of  sulphur  have  been  found  very  difficult  to  eliminate  from  the  gases 
leaving  the  tube.  Lead  peroxide  ("nach  Dennstedt")  heated  to  300°  C.  and 
zinc  at  room  temperature  appear  to  retain  them  best. 

Attention  is  called  to  the  inadmissibility  of  using  dry  agents  of  different 
absorptive  power  in  the  same  train,  in  positions  where  a  difference  could  possibly 
affect  results. 

Weighing  of  Tubes.  There  is  much  greater  difficulty  in  securing  constant 
conditions  when  weighing  absorption  tubes  than  is  usually  considered  to  be 
the  case.  Electrical  effects,  caused  by  wiping  as  a  preliminary  to  weighing, 
may  occasionally  cause  errors  in  weight  running  into  the  milligrams.  The 
use  of  counterpoises  of  equal  volume  and  similar  material  and  shape  is  recom- 
mended. 

If  tubes  are  weighed  full  of  oxygen,  care  is  necessary  to  secure  a  uniform 
atmosphere  in  them.  Even  though  the  attempt  is  made  to  keep  the  apparatus 
always  full  of  oxygen,  some  air  is  admitted  when  the  boat  is  pushed  into 
combustion  tube,  and  a  much  longer  time  is  required  to  displace  this  than  is 
usually  allowed,  unless  the  flow  of  oxygen  during  aspiration  is  rapid.  The 
same  is  true  if  the  tubes  are  weighed  full  of  air  by  displacing  the  oxygen  left  in 
them  after  the  steel  is  burned.  Another  source  of  error  may  arise  from 

1  Statement  of  Mr.  George  M.  Berry,  of  the  Halcomb  Steel  Co.. 


IRON  227 

air  admitted  when  putting  the  boat  into  the  tube,  if  this  air  contains  much 
carbon  dioxide,  as  is  the  case  when  a  gas  furnace  is  used.  The  boat  is  usually 
pushed  at  once  into  the  hot  furnace,  and  as  combustion  begins  almost  imme- 
diately, there  is  no  opportunity  for  displacing  this  air  before  the  steel  begins 
to  burn. 

Graphite  in  Iron 

Two  grams  of  iron  are  dissolved  in  nitric  acid  (sp.gr.  1.20),  using  35  cc.  and 
heating  very  gently.  The  residue  is  collected  on  an  asbestos  felt,  washed  with 
hot  water,  then  with  a  hot  solution  of  potassium  hydroxide  (sp.gr.  1.10),  fol- 
lowed by  dilute  hydrochloric  acid  and  finally  by  hot  water.  After  drying  at 
100°  C.,  the  graphite  is  burned  in  the  same  manner  as  the  total  carbon,  but 
without  admixture  of  ferric  oxide. 

Manganese  in  Iron  and  Steel.     Ammonium  Persulphate  Method 

Small  amounts  of  manganese  may  be  determined  colorimetrically  by  the 
persulphate  method,  provided  the  sample  does  not  contain  over  1.5%  of  man- 
ganese. The  procedure  given  in  detail  in  the  chapter  on  Manganese,  page  267, 
in  brief  is  as  follows  : 

Reaction.    2Mn(N03)2+5(NH4)2S208+8H20 

=  5(NH4)2S04+5H2S04+4HN03+2HMn04. 

0.1  to  0.2  gram  of  steel,  according  to  the  amount  of  manganese  in  the  sample, 
is  placed  in  a  10-in.  test-tube  and  10  cc.  of  nitric  acid  (sp.gr.  1.2)  are  added. 
The  sample  is  heated  in  a  water  bath  until  the  nitrous  fumes  are  driven  off  and 
the  steel  is  completely  in  solution.  Fifteen  cc.  of  silver  nitrate  solution  are 
added  to  the  cooled  sample,  followed  immediately  with  about  1  gram  of  ammo- 
nium persulphate  crystals.  The  solution  is  warmed  (80  to  90°  C.)  until  the 
color  commences  to  develop,  and  then  for  half  a  minute  longer,  and  then  placed 
in  a  beaker  of  cold  water  until  the  solution  is  cold.  Comparison  is  now  made 
with  a  standard  steel  treated  in  the  same  way.  The  comparison  being  made 
exactly  as  indicated  for  determining  carbon  by  the  color  method.  See  chapter 
on  Carbon. 

Example.  If  the  standard,  containing  0.6%  Mn  is  diluted  to  15  cc.,  each 
cc.  =0.04%  Mn.  If  the  sample  required  a  dilution  of  20  cc.  to  match  the 
standard,  then  0.04X20=0.8%  Mn. 

Lead  Oxide  Method    (Deshey)  . 

Oxidation  of  the  manganese  in  the  steel  is  effected  in  a  nitric  acid  solution 
by  addition  of  red  lead  (or  by  lead  peroxide)  ;  the  lead  peroxide,  formed  oxidizes 
the  manganese  nitrate  to  permanganic  acid.  The  solution  is  now  titrated  with 
standard  sodium  arsenite,  the  following  reaction  taking  place: 


0.5  gram  of  steel  is  placed  in  a  150-cc.  beaker  and  dissolved  with  about 
30  cc.  of  nitric  acid  (sp.gr.  1.12).    After  violent  action  has  subsided,  the  beaker 


228  IRON 

is  placed  on  a  hot  plate  and  when  the  iron  has  dissolved,  20  cc.  of  water  added. 
The  manganese  is  now  oxidized  by  adding  red  lead  in  small  portions  at  a  time, 
until  the  solution  appears  brown  with  a  pinkish  purple  foam  on  the  surface. 
The  solution  is  diluted  with  hot  water  until  the  volume  is  about  100  cc.  and 
then  boiled  for  a  few  minutes.  It  is  now  placed  in  a  dark  closet  to  cool.  (A 
fresh  batch  of  samples  may  be  started  in  the  meantime.)  The  solution  is 
carefully  decanted  off  from  the  peroxide,  and  with  the  washings  of  the  peroxide 
residue,  titrated  with  standard  sodium  arsenite  to  the  yellowish  green  end- 
point.  The  sodium  arsenite  is  made  by  dissolving  4.96  grams  of  pure  arsenous 
acid  together  with  25  grams  of  sodium  carbonate  in  200  cc.  of  hot  water  and  the 
solution  diluted  to  2500  cc.  The  arsenite  is  standardized  against  a  steel  sample 
of  known  manganese  content,  or  against  standard  permanganate  solution. 

Bismuthate  Method  for  Determining  Manganese,  Recommended 
by  the  U.  S.  Bureau  of  Standards  l 

This  is  the  most  accurate  method  for  determining  manganese  in  iron  and 
steel.  The  procedure  is  as  follows: 

Procedure.  One  gram  of  drillings  is  dissolved  in  50  cc.  of  nitric  acid 
(sp.gr.  1.135)  in  a  200-cc.  Erlenmeyer  flask.  Irons  should  be  filtered.  The 
solution  is  cooled,  about  0.5  gram  of  sodium  bismuthate  is  added,  and  it  is 
then  heated  until  the  pink  color  has  disappeared.  Any  manganese  dioxide 
separating  is  dissolved  in  a  slight  excess  of  a  solution  of  ferrous  sulphate  or 
sodium  sulphite.  The  solution  is  boiled  till  free  from  nitrous  fumes.  After 
cooling  to  15°  C.,  a  slight  excess  of  bismuthate  is  added  and  the  flask  is  shaken 
vigorously  for  a  few  minutes.  Then  50  cc.  of  3%  nitric  acid  is  added  and  the 
solution  is  filtered  through  asbestos.  A  measured  excess  of  ferrous  sulphate 
is  run  in  and  the  excess  titrated  against  permanganate  solution  which  has  been 
compared  with  the  iron  solution  on  the  same  day.  A  great  many  steels  now 
carry  small  amounts  of  chromium  as  impurity.  In  such  cases  titration  against 
arsenite  solution  is  recommended,  or  removal  of  the  chromium  by  zinc  oxide  and 
subsequent  determination  of  the  manganese  by  the  bismuthate  method. 

Permanganate  solutions  are  standardized  against  sodium  oxalate  (Bur.  Stds. 
Sample  No.  40)  as  prescribed  by  McBride.2 

Specifications  for  Manganese  in  Iron  and  Steel 

Material.  Percentage  of  Manganese. 

Boiler  rivets 0.30-0.60 

Boiler  and  fire-box  plates not  over  0. 45 

Seamless  boiler  tubes 0 . 40-0 . 65 

Floor-grade  pig  iron not  over  0 . 80 

Cylinder-grade  pig  iron 0 . 50-0 . 80 

Forged  and  rolled  steel  wheels 0.60-0.80 

Steel  blooms  lor  forgings not  over  0.70 

Bolt  steel not  under  0 . 50 

Spring  steel not  over  0 . 50  (0 . 25  desired) 

Crank  axles,  forged not  over  0 . 75 

Castings not  over  0 . 75 

Tire  steel 0.50-0.75 

1  See  page  263. 

*Bull.  Bur.  Sds.,  8,  641.    J.  Am.  Chem.  Soc.,  34,  393,  1912. 


IRON  229 

Determination  of  Phosphorus 

The  procedures  outlined  by  the  Bureau  of  Standards  are  generally  used  in  steel 
works  laboratories. 

(a)  Preparation    of    Solution    and    Precipitation    of    Phosphorus.     Two 
grams  of  sample  are  dissolved  in  nitric  acid  (sp.gr.  1.135)  and  the  solution  is 
boiled  until  brown  fumes  no  longer  come  off.     Ten  cc.  of  permanganate  solu- 
tion (15  grams  to  1  liter)  are  added,  and  the  boiling  is  continued.     Sodium  sul- 
phite solution  is  added  to  dissolve  the  oxide  of  manganese,  and  the  solution  is 
again  boiled  and  then  filtered.    With  irons  the  insoluble  residue  should  be  tested 
for  phosphorus.    After  cooling  the  filtrate,  40  cc.  of  ammonia  (sp.gr.  0.96)  are 
added,  the  solution  is  agitated,  and  when  the  temperature  is  at  40°  C.,  40  cc. 
of  molybdate  solution  :  are   added  and   the   solution  is  shaken  vigorously  for 
five  minutes.    After  settling  out,  the  yellow  precipitate  is  treated  according  to 
one  of  the  following  methods,  b  or  c: 

(b)  Alkalimetric   Method.    The  precipitate  is  washed  with   1%  nitric  acid 
solution  followed  by  0.1%  potassium  nitrate  solution  until  the  washings  are 
no  longer  acid.     The  precipitate  is  dissolved  in  a  measured  excess  of  standard- 
ized sodium  hydroxide  solution  and  titrated  back  with  standardized  nitric  acid 
using  phenolphthalein.     The  solutions   are   standardized  against   a  steel  with 
a  known  amount  of  phosphorus. 

(c)  Molybdate   Reduction   Method.     The   precipitate   is   washed   ten   to 
fifteen  times  with  acid  ammonium  sulphate   (prepared  according  to  Blair)  or 
until  the  washings  no  longer  react  for  iron  or  molybdenum.     It  is  dissolved 
in  25  cc.  of  ammonia  (5  cc.  ammonia  of  0.90  sp.gr.  to  20  cc.  water).     The  filter 
is  washed  well  with  water  and  10  cc.  of  strong  sulphuric  acid  added  to  the 
filtrate,  which  is  run  through  the  reductor  at  once  and  titrated  against  a  N/30 
permanganate  solution  which  has  been  standardized   against   sodium   oxalate, 
as  prescribed  by  McBride.2 

Specifications  for  the  Amount  of  Phosphorus 

Class  of  Material.  phorS^e^er  cent. 

Boiler  steel 0 . 05 

Forged  and  rolled  steel  wheels 0 . 05 

Steel  blooms  for  forgings 0 . 05 

Crank  axles 0. 05 

Tire  and  bolt  steel 0.05 

Spring  steel 0 . 05 

Spring  steel  desired 0 . 03 

Fire-box  plates 0 . 03 

Castings 0.06 

Floor-grade  pig  iron 0 . 5-0 . 9 

Cylinder  iron 0 . 5-0 . 9 

Determination  of  Sulphur 

Rapid-evolution  Method.  Volumetric.  Five  grams  of  iron  or  steel  are 
placed  in  a  500-cc.  Erlenmeyer  flask,  provided  with  a  two-holed  rubber  stopper, 
through  which  passes  a  long-stem  thistle  tube  reaching  to  the  bottom  of  the 

1  Blair,  "Chemical  Analysis  of  Iron,"  (7th Ed.),  p.  97. 

2  Bull.  Bur.  Stds.,  8,  641.     J.  Am.  Chem.  Soc.,  34,  393,  1912. 


230  IRON 

flask,  and  a  delivery-bulb  condenser,  connected  by  means  of  a  rubber  tube  to 
an  absorption  bulb.  (See  sketch  of  apparatus  in  the  chapter  on  Sulphur,  volu- 
metric methods,  page  399.) 

About  25  to  35  cc.  of  an  ammoniacal  solution  of  cadmium  chloride  are  placed 
in  the  absorption  bulb,  the  apparatus  connected  and  about  100  cc.  of  dilute 
hydrochloric  acid  (sp.gr.  1.1)  poured  through  the  thistle  tube  into  the  flask 
containing  the  drillings.  The  mixture  is  heated  gently  until  the  sample  goes 
into  solution  and  then  boiled  until  steam  escapes  from  the  apparatus.  The 
reagent  in  the  absorption  bulb  should  remain  alkaline,  otherwise  a  loss  of  sulphur 
is  apt  to  occur. 

The  absorption  bulb  is  now  disconnected  and  the  contents  emptied  into  a 
400-cc.  beaker  and  the  bulb  washed  out  with  dilute  hydrochloric  acid  after 
first  rinsing  out  once  or  twice  with  water.  The  solution  is  now  diluted  to 
about  300  cc.,  and  if  not  already  acid,  is  made  so  by  addition  of  more  hydrochloric 
acid. 

Two  to  3  cc.  of  starch  indicator  are  added  and  the  mixture  titrated 
with  standard  iodine,  stirring  constantly  during  the  titration.  A  permanent 
blue  color  in  the  end-point  sought.  If  much  cadmium  sulphide  is  present 
additional  hydrochloric  acid  may  be  required. 

The  number  of  cc.  of  iodine  solution  required  multiplied  by  the  factor  of 
iodine  to  sulphur  gives  the  amount  of  sulphur  present  in  the  sample  taken. 

NOTES.     For  a  more  complete  description  of  the  procedure  see  chapter  on  Sulphur. 

With  certain  pig  irons  low  results  are  apt  to  be  obtained  by  the  evolution  method. 
For  such  the  gravimetric  method  given  is  recommended. 

Gray  iron  will  evolve  all  its  sulphur  as  H2S,  white  iron,  gray  water-chilled  iron, 
gives  up  only  part  of  its  sulphur  by  the  evolution  method.  The  method  gives  low 
results  for  high  carbon  steel. 

In  place  of  absorbing  the  H2S  in  cadmium  chloride,  the  Bureau  of  Standards 
recommends  absorption  in  an  ammonicaal  solution  of  hydrogen  peroxide  (5  cc.  H2O2 
3% +25  cc.  NH4OH,  sp.gr.,  0.90).  The  sulphuric  acid  formed  is  precipitated  from 
a  slightly  hydrochloric  acid  solution,  by  barium  chloride  and  weighed  as  BaS04. 


Method  by  the  U.  S.  Bureau  of  Standards.    Gravimetric 
Sulphur  by  Oxidation 

Five  grams  of  iron  or  steel  are  dissolved  in  a  400-cc.  Erlenmeyer  flask,  using 
50  cc.  of  strong  nitric  acid.  A  little  sodium  carbonate  is  added,  the  solution 
is  evaporated  to  dryness,  and  the  residue  baked  for  an  hour  on  the  hot  plate. 
To  the  flask  30  cc.  of  strong  hydrochloric  acid  are  added,  and  the  evaporation 
and  baking  are  repeated.  After  solution  of  the  iron  in  another  30  cc.  of  strong 
hydrochloric  acid  and  evaporation  to  &  sirupy  consistency,  2  to  4  cc.  of  the 
same  acid  are  added,  followed  by  30  to  40  cc.  of  hot  water.  The  solution  is  then 
filtered  and  the  residue  washed  with  hot  water.  The  sulphur  is  precipitated 
in  the  cold  filtrate  (about  100  cc.)  with  10  cc.  of  a  10%  solution  of  barium 
chloride.  After  forty-eight  hours  the  precipitate  is  collected  on  a  paper  filter, 
washetl  first  with  hot  water  (containing  10  cc.  of  concentrated  hydrochloric  acid 
and  1  gram  of  barium  chloride  to  the  liter)  until  free  from  iron  and  then  with 
hot  water  till  free  from  chloride;  or,  first  with  cold  water,  then  with  25  cc. 
of  water  containing  2  cc.  of  concentrated  hydrochloric  acid  to  the  liter.  The 


IKON  231 

washings  are  kept  separate  from  the  main  filtrate  and  are  evaporated  to  recover 
dissolved  barium  sulphate. 

With  irons  the  paper  containing  the  insoluble  residue  above  mentioned  is 
put  into  a  platinum  crucible,  covered  with  -sodium  carbonate  free  from  sulphur, 
and  charted  without  allowing  the  carbonate  to  melt.  The  crucible  should 
be  covered  during  this  operation.  Sodium  nitrate  is  then  mixed  in  and  the 
mass  fused  with  the  cover  off.  An  alcohol  flame  is  used  throughout.  The  melt 
is  dissolved  in  water  and  evaporated  with  hydrochloric  acid  in  excess  to  dryness 
in  porcelain.  The  evaporation  with  water  and  hydrochloric  acid  is  repeated 
to  insure  removal  of  nitrates.  The  ^esidue  is  extracted  with  a  few  drops  of 
hydrochloric  acid  and  water,  the  insoluble  matter  is  filtered  off,  and  barium 
chloride  is  added  to  the  filtrate.  The  barium  sulphate  obtained  is  added  to 
the  main  portion. 

Careful  blanks  are  run  with  all  reagents. 

Specifications  for  Sulphur  in  Iron  and  Steel 

Material.  ^S^ei?*' 

Seamless  boiler  tubes must  be  below  0 . 05 

Cylinder  iron 0 . 05 

Forged  and  rolled  steel  wheels 0 . 05 

Steel  blooms  for  forgings,  basic  and  acid  open  hearth 0.05 

Bolt  steel 0.05 

Spring  steel 0.05 

Crank  axles 0 . 05 

Tire  steel 0 . 05 

Castings 0 . 06 

Boiler  rivets 0 . 04 

Floor-grade  iron 0 . 04 

Boiler  plates 0.035 

Fire-box  plates 0.035 

Amount  desired  in  spring  steel 0.030 

Muck  bar  iron 0 . 02 

Determination  of  Silicon 

One  gram  of  pig  iron,  cast  iron,  and  high  silicon  iron,  or  5  grams  of  steel, 
wrought  iron,  and  low  silicon  iron  are  taken  for  analysis.  (By  taking  multiples 
of  the  factor  weight  0.4693,  Si02  to  Si,  the  final  calculation  is  simplified.)  The 
sample  is  placed  in  a  250-cc.  beaker  and  20  to  50  cc.  of  dilute  nitric  acid  added. 
If  the  action  is  violent,  cooling  the  beaker  in  water  is  advisable.  When  the 
reaction  subsides,  20  cc.  of  dilute  sulphuric  acid,  1:1,  are  added,  the  mixture 
placed  on  the  hot  plate  and  evaporated  to  dense  white  fumes.  The  residue 
is  taken  up  with  150  cc.  of  water  containing  2  to  5  cc.  of  sulphuric  acid  and 
heated  until  the  iron  completely  dissolves. 

The  solution  is  filtered  and  the  silica  residue  washed  first  with  hot  dilute 
hydrochloric  acid,  sp.gr.  1.1,  and  then  with  hot  water  added  in  small  portions 
to  remove  the  iron  sulphate.  The  residue  is  now  ignited  and  weighed  as  silica. 

NOTE.  II  the  ash  is  colored  by  iron  oxide,  silica  is  determined  by  difference, 
after  expelling  the  silica  by  adding  4  to  5  cc.  of  hydrofluoric  acid  and  a  few  drops  of 
sulphuric,  taking  to  drvness  and  igniting  he  esidue. 

The  following  acid  mixtures  are  recommended  >y  the  U.  P.  Ry.  For  steel,  wrought 
iron  and  low  silicon  iron,  8  parts  by  volume  of  HNO3,  sp.gr.  1.42;  4  parts  of  cone. 
H2SO4,  sp.gr.  1.84;  6  parts  HC1,  sp.gr.  1.2  and  15  parts  by  volume  of  water.  For 


232  IRON 

dissolving  pig  iron,  cast  iron  and  high  silicon  iron,  a  mixture  of  8  parts  by  volume 
of  strong  nitric  acid  and  5  parts  of  strong  sulphuric  acid,  diluted  with  17  volumes  of 
water  is  used. 

Rapid  Method  for  Determining  Silicon  in  Foundry  Work.  Liquid  iron, 
dropped  into  cold  water  from  a  ladle  3  ft.  above  the  water,  will  form  shot  shaped 
according  to  forms  resulting  from  its  chemical  constitution,  silicon  being  an 
important  factor.  Round  shot,  concave  upper  surface,  1  to  f  in.  in  diameter, 
indicate  over  2%  silicon.  Flat,  or  irregular  shot  indicate  low  silicon.  Shot  with 
elongated  tails  indicate  very  low  silicon. 

Method  of  the  U.  S.  Bureau  of  Standards  for  Silicon 

The  insoluble  residue  obtained  in  preparing  the  iron  or  steel  for  the  gravi- 
metric sulphur  determination  is  filtered  off,  ignited  in  platinum,  and  weighed. 
Evaporation  with  a  little  hydrofluoric  acid  and  1  drop  of  sulphuric  acid  and 
subsequent  ignition  gives  by  the  loss  of  weight  silica  corresponding  to  the 
silicon  of  the  sample. 

Specifications  for  Silicon  in  Iron  and  Steel 

Material.  Amount  of  Silicon,  per  cent. 

Boiler  and  fire-box  plates not  over  0 . 03 

Floor-grade  pig  iron*. ~ . . .  2 . 25-2 . 75 

Cylinder-grade  pig  iron 1 . 25-1 . 60 

Forged  and  rolled  steel  wheels not  over  0.20 

Spring  steel not  over  0 . 25  (0.15  desired) 

Tire  steel . .  .  .  under      0 . 25 


LEAD 

WILFRED  W.  SCOTT 

Pb,  at.wt.  207.3;   sp.gr.  11.34;   m.p.  327°;  b.p.  1535° C;   oxides,  PbO, 

PbO2,  Pb3O4. 

DETECTION 

Hydrochloric  acid  precipitates  lead  incompletely  from  its  cold  solution  as 
white  PbCl2,  soluble  in  hot  water  by  which  means  it  is  separated  from  mercurous 
chloride  and  silver  chloride.  PbCl2  forms  needle-like  crystals  upon  cooling  the 
extract. 

Hydrogen  sulphide  precipitates  black  PbS  from  slightly  acid  solutions  along 
with  the  other  elements  of  the  group.1  Yellow  ammonium  sulphide,  sodium 
sulphide  and  the  fixed  alkalies  dissolve  out  arsenic,  antimony  and  tin.  The 
sulphide  of  lead,  together  with  bismuth,  copper  and  cadmium,  dissolve  in  hot 
dilute  nitric  acid,  leaving  mercuric  sulphide  insoluble.  The  extract  evaporated 
to  dryness  and  then  to  S03  fumes,  after  addition  of  sulphuric  acid,  expels  nitric 
acid.  Upon  adding  water  to  the  residue  and  boiling  with  a  little  additional 
sulphuric  acid  the  sulphates  of  bismuth,  copper  and  cadmium  are  dissolved  out, 
lead  sulphate  remaining  as  a  white  residue. 

Lead  may  be  further  confirmed  by  dissolving  the  sulphate  in  ammonium 
acetate  (barium  sulphate  is  very  slightly  soluble,)  and  precipitating  the  yellow 
chromate,  PbCr04,  by  addition  of  potassium  dichromate  solution. 

ESTIMATION 

The  determination  of  lead  is  required  in  valuation  of  its  ores — galena, 
PbS;  anglesite  PbS04;  cerussite,  PbC03;  krokoite,  PbCr04;  pyromorphite, 
3Pb3P208 •  PbCl2.  It  is  determined  in  lead  mattes;  certain  slags;  drosses  from 
hard  lead;  cupel  bottoms;  skimmings;  lead  insecticides  (arsenate  of  lead); 
paint  pigments  such  as  white  lead,  red  lead,  yellow  and  red  chromates,  etc. 
It  is  determined  in  alloys  such  as  solder,  type  metal,  bell  metal,  etc.  The  esti- 
mation is  necessary  in  the  complete  analysis  of  a  large  number  of  ores,  especially 
in  minerals  of  antimony  and  arsenic.  Traces  of  lead  are  determined  in  certain 
food  products  where  its  presence  is  undesirable. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  lead,  its  alloys,  or  ores  the  following  facts  will  be  recalled. 
Hot,  dilute  nitric  acid  is  the  best  solvent  of  the  metal.  Lead  nitrate  is  insol- 

1  Lead  precipitates  best  from  solutions  containing  1  cc.  of  concentrated  free  hydro- 
chloric acid  (sp.gr.  1.19)  for  each  100  cc.  of  solution.  The  sulphide  is  appreciably 
soluble  if  the  acidity  is  increased  to  3  cc.  HC1  per  100  of  solution. 

233 


234  LEAD 

uble  in  concentrated  nitric  acid,  but  dissolves  readily  upon  dilution  with  water. 
The  metal  is  insoluble  in  dilute  sulphuric  acid,  but  dissolves  in  the  hot,  concen- 
trated acid.  Although  not  soluble  in  dilute  hydrochloric,  it  dissolves  in  the 
hot,  concentrated  acid,  especially  in  presence  of  the  halogens  chlorine,  bromine 
and  iodine.  The  metal  is  soluble  in  glacial  acetic  acid.  The  salts  are  soluble  in 
hot,  dilute  nitric  acid.  In  dissolving  sulphide  ores  it  should  be  kept  in  mind  that 
strong  nitric  acid  will  form  some  lead  sulphate  which  will  be  precipitated  upon 
dilution  of  the  solution.  Oxidation  is  less  apt  to  occur  with  the  dilute  acid. 
Silicates  and  slags  require  fusion  with  sodium  carbonate  and  potassium  car- 
bonate. The  cooled  mass  may  then  be  extracted  with  hot  water  to  remove  silica 
and  the  residue  containing  the  carbonates  of  the  heavy  metals  dissolved  hi 
dilute  nitric  acid.  Lead  salts  are  soluble  in  ammonium  acetate. 

Ores,  Minerals  of  Lead,  etc.  One  gram  of  ore  if  rich  in  lead  (galena), 
or  more  if  the  lead  content  is  low,  is  placed  in  a  platinum  dish  and  40  to  50  cc. 
of  a  mixture  of  one  part  concentrated  sulphuric  acid  (sp.gr.  1.84)  and  three  parts 
of  concentrated  nitric  acid  (sp.gr.  1.42)  added.  The  covered  dish  is  heated 
gently  until  the  violent  action  has  ceased,  the  cover  is  then  rinsed  off  and  10 
to  15  cc.  of  hydrofluoric  acid,  HF,  added.  The  mixture  is  evaporated  to  S03 
fumes  (hood),  but  not  to  dryness,  and  cooled.  The  concentrate  is  diluted  with  100 
cc.  of  distilled  water  and  digested  on  the  steam  bath  until  the  salts  are  in  solution. 
The  insoluble  lead  sulphate  is  filtered  and  washed  with  10%  sulphuric  acid  solu- 
tion and  finally  with  50%  alcohol. 

It  may  be  advisable,  in  certain  cases,  to  open  up  the  ore  with  nitric  acid 
or  aqua  regia,  followed  by  sulphuric  acid  and  hydrofluoric  acid. 

Iron  Pyrites  and  Ores  with  Large  Amounts  of  Impurities  with  Small 
Amounts  of  Lead.  Ten  grams  of  the  sample  or  more,  if  lead  is  present  in 
very  small  amounts  (less  than  0.1%),  are  taken  for  analysis,  and  50  cc.  of  a 
mixture  of  potassium  bromide  and  bromine  solution  added  (75  grams  of  KBr 
dissolved  in  400  cc.  of  water  and  50  cc.  of  bromine  added).  After  ten  to 
fifteen  minutes  about  50  cc.  of  concentrated  nitric  acid  are  added  and  after  the 
violent  reaction  has  ceased  25  to  30  cc.  of  concentrated  hydrochloric  acid  and  the 
solution  is  evaporated  on  the  hot  plate  to  near  dryness.  Fifty  cc.  of  C.P.  (lead 
free)  concentrated  sulphuric  acid  is  now  added  and  the  sample  taken  to  fumes 
of  S03  on  a  sand  bath.  After  cooling,  the  concentrate  is  diluted  to  500  cc. 
with  water,  about  5  cc.  of  strong  sulphuric  acid  added,  the  solution  heated  to 
boiling  and  cooled.  The  precipitate  is  filtered  by  decantation  onto  a  fine-grained 
filter  (quality  of  an  S.  &  S.  590  or  B.  &  A.  grade  A),  the  residue  boiled  with  more 
water  containing  H2S04  and  again  decanted.  This  is  repeated  until  all  the  iron 
sulphate  is  removed.  (The  filtrates  should  be  kept  several  hours  to  see  whether 
any  of  the  lead  has  passed  through  the  paper  in  a  colloidal  condition.)  The 
precipitate  is  finally  poured  on  the  filter  and  washed  with  2%  H2S04.  Impure 
residues  are  extracted  for  lead  with  ammonium  acetate. 

Solution  of  Lead  Alloys.  As  a  rule  these  are  best  decomposed  by  treating 
0.5  to  1.0  gram  of  the  material,  or  more  as  the  case  may  require,  with  a  hot 
solution  of  nitric  acid,  1:1,  and  evaporating  the  solution  to  low  bulk,  but  not 
to  dryness.  Hot  water  is  now  added  and  the  material  boiled  and  the  soluble 
portion  filtered  off.  The  insoluble  material  is  digested  with  concentrated  hydro- 
chloric acid  to  which  a  little  bromine  has  been  added.  Boiling  the  mixture 
will  generally  effect  solution.  (It  must  be  remembered  that  lead  chloride  is 
difficultly  soluble  in  cold  dilute  solutions.)  The  lead  is  converted  to  PbS04 


LEAD  235 

by  addition  of  sulphuric  acid  and  taking  to  S03  fumes  as  in  case  of  ores.  The 
purification  of  the  impure  sulphate  will  be  given  later. 

Lead  may  be  precipitated  as  the  chloride  in  the  presence  of  a  large  excess  of 
absolute  alcohol  and  filtered  free  practically  rrom  impurities. 

Brass  and  bronze  may  be  dissolved  in  hot  dilute  nitric  acid,  1:1.  Bearing 
metal  is  best  treated  with  a  mixture  of  hydrochloric  acid  5  parts  and  nitric  acid 
1  part. 

SEPARATIONS 

Separation  of  Lead  as  Sulphate.  Lead  is  most  frequently  separated  from 
other  metals  by  precipitation  as  sulphate,  PbS04,  according  to  the  details  given 
under  "  Preparation  and  Solution  of  the  Sample."  In  the  presence  of  much  bis- 
muth or  iron  it  is  necessary  to  wash  the  precipitate  with  a  10%  sulphuric  acid 
solution  to  keep  the  bismuth  in  solution  and  to  prevent  the  formation  of  the  dif- 
ficultly soluble  basic  ferric  sulphate.  In  absence  of  appreciable  amounts  of 
these  elements  the  lead  sulphate  is  more  completely  separated  by  adding  to  the 
dilute  sulphuric  acid  solution  an  equal  volume  of  alcohol,  filtering  and  washing  the 
residue  with  50%  alcohol. 

Separation  of  Lead  from  Barium,  In  the  analysis  of  minerals  containing 
barium,  the  insoluble  sulphate,  BaS04,  will  be  precipitated  with  lead.  Since 
barium  sulphate  is  slightly  soluble  in  ammonium  acetate  it  will  contaminate  the 
lead  in  the  subsequent  extraction  by  this  reagent.  The  presence,  however,  of  a 
little  sulphuric  acid,  renders  this  solubility  practically  neglig  ble.  The  sulphuric 
acid  should  not  exceed  1-2%  in  the  ammonium  acetate  reagent,  as  lead  sulphate 
will  precipitate  if  sufficient  sulphuric  acid  is  added  to  the  acetate  extract.  (Lead 
sulphate  is  precipitated  almost  completely  if  the  acetate  solution  contains  10% 
sulphuric  acid.) 

Lead  may  be  separated  from  barium  sulphate  by  digesting  the  mixed  sulphates 
with  ammonium  carbonate  solution,  whereby  the  lead  sulphate  is  transposed  to  lead 
carbonate  and  ammonium  sulphate,  while  barium  sulphate  is  not  changed.  The 
soluble  ammonium  sulphate  may  be  washed  out  with  ammonium  solution  followed 
by  water.  Since  lead  carbonate  is  slightly  soluble  in  the  ammonium  salt,  the 
filtrate  is  treated  with  hydrogen  sulphide  and  the  dissolved  lead  recovered  as 
PbS.  The  residue  containing  lead  carbonate  and  barium  sulphate  is  treated  with 
dilute  nitric  or  acetic  acid.  Lead  passes  into  solution,  while  barium  sulphate 
remains  insoluble. 

Extraction  of  Lead  from  the  Impure  Sulphate  by  Ammonium  Acetate.  The 
filter  containing  the  impure  sulphate,  obtained  by  one  of  the  procedures  for 
solution  of  the  sample,  is  placed  in  a  casserole  and  extracted  with  about  50  cc. 
of  hot,  slightly  ammoniacal  ammonium  acetate,  the  stronger  the  acetate  the 
better.  The  clear  liquid  is  decanted  through  a  filter  and  the  extraction  repeated 
until  the  residue  is  free  from  lead  (i.e.,  no  test  is  obtained  for  lead  with 
K2Cr207).  A  very  effective  method  of  extraction  is  by  adding  solid  ammonium 
acetate  directly  to  the  sample  on  a  filter  and  pouring  over  it  a  hot  solution  of 
ammonium  acetate.  The  filtrate  containing  the  pure  lead  acetate  solution  may 
now  be  examined  by  one  of  the  following  procedures. 

Lead  sulphate  containing  arsenic  should  be  dissolved  in  ammonium  acetate, 
the  extract  made  alkaline  and  lead  precipitated  as  PbS.  Arsenic  remains  in  solu- 
tion. 


236  LEAD 

The  isolation  of  minute  quantities  of  lead  from  large  amounts  of  other  sub- 
stances is  described  under  "Gravimetric  Methods  for  Traces  of  Lead." 


GRAVIMETRIC  METHODS 

Determination  of  Lead  as  the  Sulphate,  PbSO4 

Procedure.  The  sample  having  been  dissolved  according  to  a  method  out- 
lined, the  lead  precipitated  as  PbS04  by  addition  of  an  excess  of  sulphuric  acid,  and 
taking  to  S03  fumes,  the  lead  sulphate  is  filtered  off,  upon  cooling  and  diluting 
the  sample.  The  PbS04  is  washed  with  water  containing  10%  H2S04  until  free 
from  soluble  impurities.  If  insoluble  sulphates  or  silica  are  present  the  lead  must 
be  purified.  If  such  impurities  are  known  to  be  absent  (alloys),  the  sulphate 
may  be  filtered  directly  onto  an  asbestos  mat  in  a  tared  Gooch  crucible,  dried, 
then  ignited  to  dull  red  heat,  cooled  and  finally  weighed  as  PbS04.  In  the  analysis 
of  ores,  however,  it  is  generally  advisable  to  purify  the  sulphate. 

Purification  of  Lead  Sulphate.  Details  of  the  procedure  have  been  given 
under  Separations — Extraction  of  Lead  from  the  Impure  vSulphate.  The  lead 
sulphate  having  been  brought  into  solution  by  extraction  with  strong  ammonium 
acetate  solution,  the  excess  acetic  acid  is  volatilized  by  evaporation,  the  residue 
cooled  and  diluted  with  water.  An  excess  of  sulphuric  acid  is  added  and  the 
precipitated  sulphate  is  filtered  off,  washed  with  dilute  sulphuric  acid  and 
alcohol,  dried  at  about  110°  C.,  or  if  preferred  by  ignition  at  dull  red  heat,  and 
weighed. 

PbS04X  0.6831  =Pb.  Pb  multiplied  by  100  and  divided  by  weight  of  sample 
taken  equals  per  cent. 

NOTES.  Lead  sulphate  may  be  precipitated  from  ammonium  acetate  solution 
by  adding  sulphuric  acid  until  the  solution  contains  approximately  10%  H2SO4. 

An  acetate  extraction  may  not  be  necessary,  as  is  generally  the  case  in  the  analysis 
of  alloys.  In  analysis  of  ores,  however,  PbSO4  may  be  contaminated  by  sulphates  of 
the  alkaline  earths  and  by  silica.  The  difficultly  soluble  oxides  of  iron  and  alumina 
may  also  be  present. 

If  arsenic  is  in  the  sulphate  it  will  pass  into  the  filtrate  with  the  lead. 


Determination  of  Lead  as  the  Chromate,  PbCrO* 

This  excellent  method  is  applicable  to  a  large  class  of  materials  and  is  of 
special  value  in  precipitation  of  lead  from  an  acetic  acid  solution,  the  method 
depending  upon  the  insolubility  of  lead  chromate  in  weak  acetic  acid. 

Procedure.  The  solution  of  the  sample,  precipitation  of  the  lead  as  the 
sulphate  and  extraction  of  lead  with  ammonium  acetate  have  been  given  in  detail. 

The  filtrate,  containing  all  the  lead  in  solution  as  the  acetate,  is  acidified 
slightly  with  acetic  acid  and  heated  to  boiling.  Lead  is  precipitated  by  addition 
of  potassium  dichromate  solution  in  excess  (10  cc.  of  5%  K2Cr2O7  solution  are  gen- 
erally sufficient).  The  solution  is  boiled  until  the  yellow  precipitate  turns  to  a 
shade  of  orange  or  red.1  The  precipitate  is  allowed  to  settle  until  the  super- 
natant solution  is  clear.  (This  should  appear  yellow  with  the  excess  of  dichromate 
reagent.)  The  PbCr04  is  filtered  onto  an  asbestos  mat  in  a  tared  Gooch  cru- 

1  The  yellow  precipitate  gives  high  results,  since  it  is  difficult  to  wash.  The  crys- 
talline orange  or  red  compound  may  be  quickly  filtered  and  washed. 


LEAD  237 

cible,  washed  with  water,  dried  in  an  oven  at  about  110°  C.  and  the  cooled 
compound  weighed  as  PbCr04. 

•pu  y  i  AA 

«         PbCr04X0.641  =Pb.     _       '    r  =per  cent  Pb. 

Wt.  of  sample 

NOTES.  Impurities,  such  as  iron,  copper,  cadmium,  etc.,  in  the  acetate  solution  of 
lead  seriously  interfere  in  the  chrornite  precipitation.  These  should  be  leached  out 
with  water  containing  a  little  sulphuric  acid  before  extracting  the  lead  sulphate  with 
ammonium  acetate.  See  remarks  under  section  on  Traces  of  Lead. 

If  a  standard  solution  of  potassium  dichromate  is  used  in  the  precipitation 
of  lead  the  excess  of  the  reagent,  upon  filtering  of  the  precipitate,  may  ba  titrated 
and  the  lead  determined  vofumetrically.  A  known  amount  of  dichromate  solution 
(added  from  a  burette)  sufficient  to  precipitate  all  the  lead  and  about  one-third  of  the 
volume  in  excess  is  added  to  the  hot  solution.  After  boiling  about  two  minutes  the 
precipitate  is  filtered  off  quickly  and  washed  several  times  with  hot  water.  The 
filtrate,  or  an  aliquot  part  of  it,  is  made  acid  with  5  cc.  concentrated  sulphuric  acid 
and  titrated  with  standard  ferrous  sulphate  at  about  60°  C.,  using  potassium  ferri- 
cyanide  as  an  outside  indicator;  the  end-point  is  a  blue  color  produced  by  the  slight 
excess  of  the  ferrous  salt  reacting  with  the  indicator.  The  excess  of  dichromate  may 
be  determined  by  adding  3  to  4  grams  of  solid  potassium  iodide,  KI,  to  the  solution 
diluted  to  about  500  cc.  with  water  to  which  15  cc.  of  concentrated  sulphuric  acid 
has  been  added.  The  liberated  iodine  is  titrated  with  standard  thiosulphate,  the 
end-point  being  colorless,  with  starch  solution  internal  indicator,  changing  from 
blue.  Bi,  Sb,  Ba,  Sr  and  Ca  interfere  slightly. 

One  cc.  N/10  K2Cr207  =  0.010355  gram  Pb.     One  cc.  N/5  K2Cr2O7  =0.02071  gram  Pb. 

Determination  of  Lead  as  the  Molybdate,  PbMo(>4 

This  method  is  rapid  and  has  the  following  advantages : 

a.  The  sulphation  of  lead  is  avoided.  6.  The  acetate  extraction  is  elimi- 
nated, c.  The  precipitate  may  be  ignited,  d.  The  ratio  of  lead  to  its  molybdate 
compound  is  greater  than  either  lead  to  PbS04  or  to  PbCr04,  lessening  the  chance 
of  error  through  weighing. 

Cobalt,  calcium,  strontium  and  barium  have  little  effect  in  presence  of 
ammonium  acetate.  In  absence  of  this  salt  they  interfere  slightly. 

Procedure.  The  ore  or  alloy  is  decomposed  with  nitric  acid  or  aqua  regia 
as  the  case  may  require.  (Silica  if  present  is  eliminated  by  taking  to  dryness, 
dehydrating,  taking  up  with  dilute  nitric  acid  and  filtering.)  To  the  clear  liquid 
ammonium  chloride  is  added  and  then  sufficient  ammonium  oxalate  to  destroy 
the  excess  of  free  nitric  acid. 

Lead  is  now  precipitated  by  adding  20  to  30  cc.  of  ammonium  molybdate 
(4  grams  per  liter + acetic  acid)  stirring  the  mixture  during  the  addition.  After 
boiling  for  two  or  three  minutes  the  precipitated  lead  molybdate  is  allowed  to 
settle,  then  filtered  through  pulp,  washed  with  small  portions  of  hot  water  and 
ignited  over  a  Bunsen  burner. 

The  cooled  residue  is  weighed  as  PbMo04. 

PbMo04X0.5642=Pb. 

NOTES.  If  antimony  or  other  members  of  the  group  are  present  in  the  original 
sample  it  is  advisable  to  dissolve  the  residue  in  HC1  and  reprecipitate  the  lead  with 
molybdate  reagent. 

If  lead  is  in  the  form  of  the  sulphide,  as  may  be  the  case  in  a  complete  analysis 
of  a  substance,  it  is  decomposed  with  hot  dilute  HNOa  and  precipitated  as  PbMoO4. 


238  LEAD 

Electrolytic  Determination  of  Lead  as  the  Peroxide,  PbO2 

An  electric  current  passed  through  a  solution  of  lead  containing  sufficient 
free  nitric  acid  will  deposit  all  the  lead  on  the  anode  as  lead  peroxide.  The  method 
is  excellent  for  analysis  of  lead  alloys. 

Procedure.  The  sample  containing  not  over  0.5  gram  lead  is  brought  into 
solution  by  heating  with  dilute  nitric  acid,  1:1.  The  solution  is  washed  into 
a  large  platinum  dish  with  unpolished  inner  surface.  Twenty  to  25  cc.  concen- 
trated nitric  acid  (sp.gr.  1.4)  are  added  and  the  solution  diluted  to  about  150  cc. 

The  sample  is  electrolyzed  in  the  cold  with  0.5  to  1  ampere  current  and  2  to 
2.5  volts,  the  platinum  dish  forming  the  anode  of  the  circuit,  a  spiral  platinum 
wire  or  a  platinum  crucible  dipped  into  the  solution  being  the  cathode.  Three 
hours  are  generally  sufficient  for  the  deposition  of  0.5  gram  Pb.  Overnight 
is  advisable,  a  current  of  0.05  ampere  being  used. 

A  rapid  deposition  of  the  lead  may  be  obtained  by  heating  the  solution  to 
60  to  65°  C.  and  electrolyzing  with  a  current  NDi0o  =  1.5  to  1.7  amperes,  the 
E.M.F.  varying  within  wide  limits.  Stirring  the  solution  with  a  rotating  cathode 
aids  in  the  rapid  deposition  of  the  Pb02. 

To  ascertain  whether  all  the  lead  has  been  removed  from  the  solution,  more 
water  is  added  so  as  to  cover  a  fresh  portion  of  the  dish  with  water.  The  elec- 
trolysis is  complete  if  no  fresh  deposition  of  the  peroxide  takes  place  after  half 
an  hour. 

The  water  is  siphoned  off  while  more  water  is  being  added  until  the  acid  is 
removed,  the  current  is  then  broken,  the  dish  emptied  of  water  and  the  deposits 
dried  at  180°  C.  and  weighed  as  Pb02. 

The  deposit  of  lead  peroxide  gently  ignited  forms  lead  oxide,  PbO,  a  pro- 
cedure recommended  by  W.  C.  May,1  confirmed  by  Treadwell  and  Hall  as 
giving  more  accurate  results  than  the  peroxide,  Pb02. 

Pb02X0.8662=Pb. 
PbO  X0.9283=Pb. 

NOTE.  The  deposits  of  lead  oxide  or  peroxide  may  be  removed  by  dissolving  off 
with  warm  dilute  nitric  acid. 

For  volumetric  procedur  e-titration  of  the  peroxide  PbO2  see  page  240. 


VOLUMETRIC  METHODS 
Volumetric  Ferrocyanide  Method  for  the  Determination  of  Lead 

Although  the  gravimetric  methods  for  the  determination  of  lead  are  con- 
sidered the  more  accurate,  yet  the  volumetric  procedures  may  be  frequently  used 
with  advantage.  The  ferrocyanide  method  has  been  pronounced  by  Irving  C. 
Bull 2  to  be  the  best  of  the  procedures  in  common  use,  the  results  being  accurate. 

Procedure.  Lead  sulphate  is  obtained  according  to  the  method  outlined 
under  Preparation  and  Solution  of  the  Sample.  The  lead  sulphate  is  transferred 
to  a  small  beaker  and  gently  boiled  with  10  to  15  cc.  of  a  saturated  solution  of 
ammonium  carbonate,  the  liquid  having  been  added  cold  and  brought  up  to 

1  Am.  Jour.  Sci.  and  Arts  (3)  6,  255. 

2  C.  N.,  2253,  87,  1903. 


LEAD  239 

boiling.  After  cooling,  the  precipitate  is  filtered  onto  the  original  filter  paper 
from  which  the  lead  sulphate  was  removed.  The  lead  carbonate  is  washed  free 
of  alkali  with  cold  water.  The  filter  with  the  precipitate  is  dropped  into  a  flask 
containing  a  hot  mixture  of  5  cc.  of  glacial  acetic  acid  with  25  cc.  of  water. 
The  lead  carbonate  is  decomposed  by  boiling  and  the  solution  diluted  to  150  cc. 

Titration.  The  sample  warmed  to  60°  C.  is  titrated  with  a  standard  solu- 
tion of  potassium  ferrocyanide,  using  a  saturated  solution  of  uranium  acetate, 
as  an  outside  indicator.  The  excess  of  ferrocyanide  produces  a  brown  color  with 
the  uranium  acetate  drop  on  the  tile. 

Free  ammonia  must  be  absent,  as  it  reacts  with  uranium  acetate  and  gives 
low  results.  NH4OH  precipitates  reddish  brown,  gelatinous  uranous  hydroxide, 
U(OH)4. 

The  bulk  of  solution  to  be  titrated  should  be  as  near  as  possible  to  100  cc., 
including  10  cc.  of  50%  acetic  acid. 

One  per  cent  potassium  ferrocyanide  reagent  is  used  in  the  titration.  This 
reagent  is  standardized  against  a  known  amount  of  lead  in  solution  as  an  acetate. 

A  correction  of  0.8  cc.  is  generally  necessary  on  account  of  the  indicator. 
This  is  determined  by  a  blank  titration. 

Antimony,  bismuth,  barium,  strontium  and  calcium  interfere  only  to  a  very 
slight  extent,  the  error  being  negligible. 

Volumetric  Determination  of  Lead  by  the  Molybdate  Method 1 

Lead  is  precipitated  as  molybdate  from  an  acetic  acid  solution  by  a  standard 
molybdic  solution,  the  termination  of  the  reaction  being  recognized  by  the 
yellow  color  produced  by  the  excess  of  molybdic  reagent  when  a  drop  of  the 
mixture  comes  in  contact  with  a  drop  of  tannin  solution  used  as  an  outside 
indicator. 

Special  Reagents  Required.  Ammonium  Molybdate  Reagent.  4.75  grams 
of  the  salt  are  dissolved  in  water  and  made  up  to  1  liter.  One  cc.  with  a  half 
gram  sample  is  equal  approximately  to  1%  Pb. 

Standardization  of  Ammonium  Molybdate  Reagent.  0.293  gram  pure 
lead  sulphate,  PbS04,  equivalent  to  0.2  gram  Pb,  is  dissolved  in  50  cc.  of  a  sat- 
urated solution  of  ammonium  acetate,  a  piece  of  litmus  paper  is  thrown  in  and 
a  few  drops  of  acetic  acid  added  to  acid  reaction.  The  solution  is  made  up  to 
200  cc.  and  is  titrated  as  directed  below  in  the  procedure  for  lead. 

0  2 

The  lead  value  per  cc.  = : — 3  gram  Pb. 

cc.  reagent  required 

NOTE.  In  place  of  PbSO4  pure  lead  foil  may  be  taken.  0.2  gram  of  the  foil  dis- 
solved in  10-15  cc.  hot  nitric  acid  1  :  1  and  converted  to  the  sulphate  by  taking  to 
fumes  with  20  cc.  1  :  1  H2SO4. 

Tannin  Indicator.  Freshly  prepared  tannin  solution  containing  0.1  gram 
tannin  per  20  cc.  of  water. 

Procedure.  0.5  gram  of  the  ore  is  dissolved  by  gently  heating  with  10  cc.  of 
strong  hydrochloric  acid  followed  by  5  cc.  of  nitric  acid  and  additional  hydro- 
chloric acid  if  necessary.  Five  to  10  cc.  of  concentrated  sulphuric  acid  are  added 
and  the  solution  evaporated  to  S03  fumes  over  a  free  flame.  About  25  cc.  of 

1  Method  of  D.  H.  H.  Alexander,  modified  by  Low. 


240  LEAD 

water  are  added  to  the  cooled  solution  and  the  liquid  boiled  for  ten  to  fifteen 
minutes  to  dissolve  the  anhydrous  ferric  sulphate  that  may  be  present. 

Upon  cooling,  the  precipitated  PbS04  with  any  impurities  it  may  contain 
(Si02,  CaS04,  BaS04,  etc.)  is  filtered  off  and  washed  with  cold  dilute  sulphuric 
acid  (1  :  10). 

Purification  of  the  Lead  Precipitate,  in  Presence  of  Calcium,  Iron,  etc. 
The  precipitate  is  rinsed  into  the  original  flask  and  about  5  grams  of  pure 
ammonium  chloride  and  1  cc.  of  concentrated  hydrochloric  acid  added.  The 
solution  with  the  precipitates  is  boiled  until  only  the  silica  remains  undissolved. 
The  free  acid  is  just  neutralized  with  ammonia  and  the  lead  precipitated  as 
PbS  by  addition  of  ammonium  sulphide.  The  precipitate  is  filtered  and  washed 
free  of  calcium.  If  iron  is  present  it  must  be  removed  by  redissolving  the  pre- 
cipitate in  5  cc.  of  dilute  sulphuric  acid  and  again  precipitating  the  lead  as  PbS 
by  addition  of  sufficient  hydrogen  sulphide  water  or  passing  the  gas  into  the 
acid  solution.  The  lead  sulphide  is  now  decomposed  by  boiling  with  5  cc.  of 
concentrated  hydrochloric  acid  for  several  minutes  and  then  adding  3  or  4  drops 
of  nitric  acid  to  remove  the  last  traces  of  H2S. 

The  free  acid  in  the  solution  is  neutralized  with  ammonium  hydroxide 
(litmus  indicator),  and  then  made  slightly  acid  by  addition  of  glacial  acetic  acid. 
The  mixture  is  diluted  to  200  cc.  with  hot  water. 

Titration.  To  about  two-thirds  of  the  sample,  the  standard-ammonium 
molybdate  is  added  from  a  burette  until  a  drop  of  the  solution,  brought  into 
contact  with  a  drop  of  the  tannin  indicator  upon  a  white  porcelain  tile  or  par- 
affined paper,  gives  a  brown  or  yellow  color.  Some  more  of  the  lead  solution  is 
added  to  this  titrated  sample  and  the  operation  is  repeated.  By  keeping  a  por- 
tion of  the  sample  in  reserve  it  is  possible  to  obtain  the  exact  end-point  and  avoid 
overrunning,  as  would  be  apt  to  occur  if  the  entire  sample  were  taken  at  one 
time. 

Cc.  molybdate  reagent  multiplied  by  value  in  terms  of  Pb  divided  by  wt.  of 
sample  =Pb. 

Blank.  Deduction  of  0.7  to  1  cc.  is  frequently  necessary.  The  exact  amount 
may  be  determined  by  taking  the  same  amount  of  reagents  as  are  present  in 
the  sample,  without  the  lead,  and  titrating  with  ammonium  molybdate,  as  above, 
on  a  boiled  sample. 

Interferences:  Antimony,  bismuth,  barium,  strontium  and  calcium  have  a 
slight  effect  on  the  results. 

The  lead  is  obtained  in  solution  in  a  comparatively  pure  form  by  extraction 
of  the  sulphate  with  ammonium  acetate.  The  more  tedious  method  of  isolation 
as  directed  in  the  procedure  may  not  be  necessary. 

Reduction  and  Titration  of  Lead  Peroxide  Deposited  Electrolytically 

The  electrolytic  deposition  of  lead  as  the  peroxide,  PbO2,  has  been  given  on  page 
238.  To  avoid  error  that  may  result  from  imperfect  drying,  a  volumetric  procedure  is 
suggested.  The  peroxide  is  dissolved  from  the  electrode  ;with  a  hot  mixture  of  25  cc. 
N/5  oxalic  acid  and  10  cc.  nitric  acid  (sp.gr.  1.2).  The  excess  of  oxalic  acid  is  titrated 
hot  with  N/10  potassium  permanganate. 

1  cc.  N/5  oxalic  acid  is  equivalent  to  0.02071  gram  lead. 


LEAD  241 


DETERMINATION   OF  SMALL  AMOUNTS   OF  LEAD 

The  determination  of  minute  quantities  of  lead  is  required  in  baking  powders 
canned  goods  and  like  products  in  which  small  amounts  of  lead  are  objection- 
able. Traces  of  lead  ranging  from  5  to  100  parts  per  million  (0.0005  to  0.01%  Pb) 
are  best  determined  colorimetrically  on  0.5  to  1  gram  samples;  larger  amounts 
of  lead  should  be  determined  gravimetrically. 

Gravimetric  Methods  for  Determining  Traces  of  Lead 

The  determination  of  extremely  small  amounts  of  lead  cannot  be  accom- 
plished by  the  usual  methods  of  precipitation,  as  the  lead  compounds  remain  in 
solution  in  a  colloidal  state.  The  addition,  however,  of  certain  substances, 
which  form  amorphous  precipitates  with  the  reagents  used  for  throwing  out  lead 
causes  the  removal  of  lead  from  the  solution  by  occlusion.  For  example,  the 
addition  of  a  sufficient  quantity  of  a  soluble  salt  of  mercury,  copper,  or  arsenic 
to  a  solution  containing  a  trace  of  lead,  and  then  saturating  the  solution  with 
H2S,  will  cause  the  complete  removal  of  lead  from  the  solution.  Iron  and 
alumina  thrown  out  of  the  solution  as  hydroxides  will  carry  down  small  amounts 
of  lead,  and  completely  remove  it  from  the  solution,  if  they  are  present  in 
sufficient  quantity.  Lead  may  be  extracted  from  finely  pulverized  substances 
by  means  of  hot  ammonium  acetate  and  precipitated  from  the  extract  as  lead 
sulphide.  Advantage  may  be  taken  of  these  facts  in  determining  traces  of 
lead  in  presence  of  large  amounts  of  other  substances. 

Amount  of  the  Sample.  It  is  advisable  to  have  the  final  isolated  lead 
compound  over  0.01  gram  in  weight,  hence,  in  a  sample  containing  10  parts  of 
lead  per  million,  800  to  1000  grams  of  the  material  should  be  taken,  since  a  kilo- 
gram of  the  material  would  contain  0.01  gram,  Pb  or  0.0156  gram  PbCr04, 
or  0.01464  gram  PbS04,  or  0.0177+  gram  PbMo04.  Large  samples  should  be 
divided  into  several  portions  of  100  to  250  grams  each,  the  lead  isolated  in  each, 
and  the  final  extracts,  containing  the  lead,  combined.  For  the  given  amount  of 
occluding  agent,  stated  in  the  procedure,  the  treated  portion  should  contain  not 
over  0.01  gram  lead. 

I. — Extraction  of  Lead  with  Ammonium  Acetate  and 
Subsequent  Precipitation 

It  is  frequently  desirable  to  extract  the  lead  from  the  mass  of  material  and 
precipitate  it  from  the  liquor  thus  obtained.  The  procedure  worked  out  by  the 
writer  is  applicable  to  determining  traces  of  lead  in  aluminum  salts,  but  with 
modifications  may  be  applied  to  a  wide  range  of  substances. 

Extraction  of  Lead.  The  desired  weight  of  finely  powdered  substance,  in  100- 
gram  portions,  is  placed  in  6-inch  porcelain  casseroles  (1000  cc.  capacity) .  To  each 
portion  are  added,  with  vigorous  stirring,  500  cc.  of  lead-free,  boiling  hot  ammi- 
nium  acetate  solution  (33%). 1  The  reaction  is  apt  to  be  energetic,  so  that 

1  The  reagent  must  be  boiling,  when  added,  to  obtain  best  results.  Experiments 
have  shown  that  considerable  alumina  and  iron  dissolve  if  the  proportion  of  the  reagent 
falls  much  below  5  cc.  of  33%  acetate  per  gram  of  sample.  With  twice  this  amount  of 
reagent  the  extract  is  free  from  iron  and  alumina.  Small  amounts  of  alumina  and  iron, 
however,  do  not  interfere  in  the  lead  determination. 


242  LEAD 

care  must  be  exercised  to  avoid  boiling  over.  The  residue  from  aluminum  sails 
is  crystalline  and  may  be  separated  from  the  extract  very  readily  by  filtering 
through  two  filter  papers  in  a  large  Buchner  funnel  and  applying  suction.1 
The  residue  is  tamped  down  to  squeeze  out  the  adhering  extract  and  washed 
with  100  cc.  more  of  hot  ammonium  acetate  followed  by  100  to  200  cc.  of  hot 
water,  again  tamped  down  and  sucked  as  dry  as  possible.  The  lead  extracts 
are  now  combined  and  lead  precipitated  as  sulphide. 

The  reagent  is  made  by  dissolving  one  part  of  lead-free  ammonium  acetate 
in  two  parts  of  distilled  water.  The  purity  of  the  reagent  should  be  tested. 

Precipitation  of  Small  Amounts  of  Lead.  To  the  solution  containing  lead  is 
added  2-3  cc.  of  a  10%  copper  sulphate  or  cadmium  sulphate  reagent.  Hydrogen 
sulphide  is  passed  into  the  liquor  until  it  is  saturated.  The  copper  or  cadmium  sul- 
phide assists  the  settling  of  lead  sulphide.  Gently  warming  on  the  steam  bath  for 
half  an  hour  coagulates  the  precipitate  and  facilitates  settling.  The  liquor  is 
decanted  through  a  double  filter  in  a  small  Buchner  funnel  and  the  residue  washed 
onto  the  filter  with  water  saturated  with  H2S  gas. 

The  precipitate  is  washed  several  times  with  ammonium  sulphide  to  remove 
sulphides  of  the  arsenic  group  and  the  residue  then  dissolved  in  a  hot  mixture  of 
hydrochloric  and  nitric  acids  (1  part  HC1.  5  parts  HN03  and  15  parts  H20).  Ten  cc. 
of  strong  sulphuric  acid  are  added  to  the  solution,  and  the  mixture  is  evaporated 
to  S03  fumes  but  not  to  dryness.  The  residue  is  taken  up  with  100-125  cc.  of  water 
containing  2  cc.  of  sulphuric  acid  and  boiled  to  dissolve  the  soluble  salts  of  iron, 
alumina,  copper,  etc.  After  cooling,  one-third  the  volume  of  95%  alcohol  is 
added  (30-40  cc.),  the  lead  sulphate  allowed  to  settle  for  an  hour  or  more,  then 
filtered  and  washed  several  times  with  30%  alcohol.  The  residue  is  extracted 
with  hot  ammonium  acetate  and  lead  chromate  precipitated  from  the  filtrate,2 
made  slightly  acid  with  acetic  acid,  by  adding  10  cc.  of  potassium  dichromate 
reagent  and  boiling,  according  to  the  standard  procedure.  (Page  236.) 

PbCr04X0.641  =Pb. 

II. — Precipitation  of  Lead  by  Occlusion  with  Iron  Hydroxide 

Wilkie  found  3  that  ferric  hydroxide  has  the  property  of  occluding  lead,  five 
parts  of  Fe(OH)3  removing  one  part  of  lead  from  solution.  Advantage  is  taken 
of  this  property  of  iron  hydroxide  in  precipitating  small  amounts  of  lead.4 

Procedure.  The  required  amount  of  material  is  weighed  out  in  50-gram  lots 
and  brushed  into  No.  8  beakers.  If  the  material  contains  organic  matter,  it  is 
treated  with  200-cc.  portions  of  concentrated  hydrochloric  acid,  the  mixture  heated 
just  below  the  boiling-point  of  HC1  solution,  and  potassium  chlorate  added,  a  few 
crystals  at  a  time,  until  the  organic  matter  is  decomposed  (hood).  If  the  material 
dissolves  in  water,  the  water  solution  is  treated  with  5  cc.  of  concentrated  hydro- 
chloric acid  and  a  few  crystals  of  potassium  chlorate  and  the  liquor  boiled. 

1  200  to  300  grams  of  material  may  be  handled  in  a  6-inch  Buchner  funnel. 

2  Should  lead  chromate  fail  to  precipitate,  the  solution  should  be  treated  with 
H2S   to   complete  saturation,   the  sulphide   collected   on   a  filter,  then  dissolved  in 
acid  and  the  procedure  described  above  repeated.     If  the  solution  still  remains  clear, 
the  absence  of  lead  is  confirmed. 

3  J.  M.  Wilkie  C.  N.,  2597,  117,  1909. 

4  Occlusion  of  lead  by  zinc  sulphide,  precipitated  by  H2S  from  a  formic  acid  solu- 
tion, is  suggested;  iron  and  alumina  would  not  interfere. 


LEAD  243 

Addition  of  Ferric  Iron.  If  sufficient  iron  is  not  already  present,  ferric 
chloride  is  added  in  such  quantity  that  the  iron  content  of  the  sample  will  be  from 
twenty  to  fifty  times  that  of  the  lead  (larger  amounts  of  iron  will  do  no  harm) 
present  in*  the  solution.  Five  to  10  cc.  of  concentrated  nitric  acid  are  added 
and  the  sample  boiled  for  ten  to  fifteen  minutes. 

Precipitation  of  Iron  and  Lead.  If  alumina  is  present,  iron  is  precipi- 
tated by  addition  of  a  large  excess  of  potassium  hydroxide,  the  alumina  going 
into  solution  as  potassium  aluminate.  In  absence  of  alumina,  ammonia  may 
be  used  to  precipitate  the  ferric  hydroxide.  Lead  is  completely  occluded  by  the 
precipitate  and  carried  down.  The  solution  is  filtered  hot  through  Baker  arid 
Adamson's  fast  filters,  threefold.  The  filtering  must  be  rapid  and  the  liquid  kept 
hot  to  prevent  clogging  of  the  filters. 

Separation  of  Lead  from  Iron.  The  precipitate  is  dissolved  in  hot  hydro- 
chloric acid  (free  from  lead).  The  solutions  are  combined,  if  several  portions 
of  the  sample  are  taken.  Concentrated  sulphuric  acid  is  added  and  the  sample 
evaporated  to  small  volume  and  heated  until  the  white  sulphuric  acid  fumes 
appear.  The  usual  procedure  is  now  followed  for  separation  of  the  lead  sulphate, 
acetate  extraction  of  lead  and  final  precipitation  of  lead  chromate. 

PbCr04X0.641  =Pb. 

NOTE.  In  place  of  using  alcohol  to  decrease  the  solubility  of  lead  sulphate,  many 
prefer  to  add  sulphuric  acid  so  that  the  acidity  of  the  solution  will  be  2-10%  free 
H2S04. 

III.  Modification  of  Seeker=Clayton   Method   for  Traces  of  Lead 

in  Baking  Powder 

One  hundred  grams  of  baking  powder  are  treated  with  25  cc.  of  water  followed 
by  75  cc.  of  strong  hydrochloric  acid  added  in  small  portions  to  avoid  excess  frothing. 
The  mixture  is  heated  until  the  starch  has  decomposed  (iodine  test  gives  blue  color 
with  starch),  the  solution  becoming  clear  and  turning  yellow.  The  free  acid  is 
neutralized  and  when  the  solution  is  cold,  400  cc.  of  lead-free  ammonium  citrate, 
saturated  with  H2S,  are  added.  Additional  H2S  is  passed  into  the  slightly  alkaline 
solution,  the  sulphides  of  iron  and  lead  allowed  to  settle,  the  clear  supernatant 
liquor  decanted  off,  the  sulphides  collected  on  a  filter  and  washed.  The  precipitate 
is  dissolved  in  nitric  acid,  lead  separated  as  a  sulphate,  extracted  with  acetate  and 
precipitated  as  dichromate  according  to  the  procedure  recommended  under  the 
acetate  extraction  method  I.1 


COLORIMETRIC  ESTIMATION   OF  SMALL  AMOUNTS 

OF  LEAD 

Introduction.  Estimation  of  small  amounts  of  lead  by  the  intensity  of  the 
brown  coloration  produced  by  the  sulphide  in  colloidal  solution  was  first  proposed 
by  Pelouze.2  The  procedure  was  modified  by  Warington 3  and  by  Wilkie  4 

1  See  Referee's  modification  Jour.  Assoc.  Off.  Ag.  Chemists,  1,  3,  512  (Nov.,  1915.) 

2  T.  J.  Pelouze,  Ann.  Chim.  Phys.,  3,  79-108, 1841. 

3  R.  Warington,  Jour.  Soc.  Chem.  Ind.,  12,  97,  1893. 

4  J.  M.  Wilkie,  Jour.  Soc.  Chem.  Ind.,  28,  636,  1909. 


244  LEAD 

to  overcome  the  color  produced  by  accompanying  impurities,  among  these,  of 
iron,  which  is  almost  invariably  associated  with  lead.  The  method  is  useful  in 
determining  traces  of  lead  in  drinking  water,  in  food  products,  baking  powders, 
canned  goods,  phosphates,  alums,  acids  such  as  sulphuric,  hydrochloric,  citric, 
tartaric  and  the  like.  By  this  procedure  on  a  gram  sample  one  part  of  lead  per 
million  may  be  detected  and  as  high  as  50  parts  may  be  estimated.  For  larger 
amounts  of  lead,  a  smaller  sample  must  be  taken.  Nickel,  arsenic,  antimony, 
silver,  zinc,  tin,  iron,  and  alumina,  present  in  amounts  such  as  commonly  occur 
in  these  materials,  do  not  interfere.1 

In  order  to  obtain  accurate  results  it  is  necessary  to  have  the  solutions  under 
comparison  possess  the  same  general  character.  "  It  must  be  remembered  that 
the  tint  depends,  .to  a  large  extent  on  the  size  of  the  colloidal  particles  of  lead, 
which  in  turn  depend  upon  the  nature  of  Che  salts  in  the  solution  and  upon  the 
way  that  the  solution  has  been  prepared."  2  Vigorous  agitation,  salts  of  the 
alkalies  and  alkaline  earths  tend  to  coagulate  the  colloidal  sulphide. 

Reagents  Required.  Standard  Lead  Solution.  A  convenient  solution 
may  be  made  by  dissolving  0.1831  gram  of  lead  acetate,  Pb(C2H3O2)2*3H20 
in  100  cc.  of  water,  clearing  any  cloudiness  with  a  few  drops  of  acetic  acid  and 
diluting  to  1000  cc.  If  10  cc.  of  this  solution  is  diluted  to  1000  cc.  each  cc. 
will  contain  an  equivalent  of  0.000001  gram  Pb. 

Harcourt  suggests  a  permanent  standard  made  by  mixing  ferric,  copper  and 
cobalt  salts.3  For  example  12  grams  of  FeCl3  together  with  8  grams  of  CuCl2 
and  4  grams  of  Co(N03)2  are  dissolved  in  water,  400  cc.  of  hydrochloric  acid 
added  and  the  solution  diluted  to  4000  cc.  150  cc.  of  this  solution  together 
with  115  cc.  of  hydrochloric  acid  (1  :  2)  diluted  to  2000  cc.  will  give  a 
shade  comparable  to  that  produced  by  the  standard  lead  solution  above,  when 
treated  with  the  sulphide  reagent.  The  exact  value  per  cc.  may  be  obtained  by 
comparison  with  the  lead  standard. 

Alkaline  Tartrate  Solution.  Twenty-five  grams  of  C.P.  sodium  potassium 
tartrate,  NaKC4H406'4H20,  is  dissolved  in  50  cc.  of  water.  A  little  ammonia  is 
added  and  then  sodium  sulphide  solution.  After  settling  some  time  the  reagent 
is  filtered.  The  filtrate  is  acidified  with  hydrochloric  acid,  boiled  free  of  H2S  and 
again  made  ammoniacal  and  diluted  to  100  cc. 

Ammonium  Citrate  Solution.  Ammonium  citrate  solution  is  prepared  in 
the  same  way  as  the  tartrate  solution  above,  25  grams  of  the  salt  being  dissolved 
in  50  cc.  of  water. 

Potassium  Cyanide.     Ten  per  cent  solution.     The  salt  should  be  lead-free. 

Sodium  Sulphide.  Ten  per  cent  solution,  made  from  colorless  crystals. 
Sodium  sulphide  may  be  made  by  saturating  a  strong  solution  of  sodium  hydroxide 
with  hydrogen  sulphide  gas,  and  then  adding  an  equal  volume  of  the  sodium 
hydroxide.  The  solution  is  diluted  to  required  volume,  allowed  to  stand  several 
days,  and  filtered. 

Sodium  metabisulphite.    Solid  salt  of  Na2S206.  * 

Apparatus.  The  color  comparison  may  be  made  in  Nessler  tubes,  or  in  a 
colorimeter.  The  Campbell  and  Hurley  modification  of  the  Kennicott-Sargent 

1  Ni  up  to  0.1%,  As  up  to  0.2%,  Zn  0.2%,  Sb  0.05%,  Cu  0.25%,  Fe  1.0%,  Al  10%, 
Sn  up  to  1.4%  do- not  interfere. 

2  J.  W.  Mellor,  "  A  Treatise  on  Quantitative  Inorganic  Analysis." 
8  A.  G.  V.  Harcourt,  Jour.  Chem.  Soc.,  97,  841,  1900. 

4  Recommended  by  W.  S.  Allen  for  reduction  of  iron. 


LEAD 


245 


colorimeter  is  excellent  for  this  purpose,1  Fig.  43.    The  colorimeter  is  simple  in 
construction  and  operation. 

The  tubes  for  holding  the  solutions  to  be  compared  are  those  of  one  of  the 
well-known  colorimeters,  in  which  the  unknown  solution  is  placed  in  the  left-hand 
tube  while  the  color  is  matched  by 
raising  or  lowering  the  level  of  a 
standard  solution  in  the  right-hand 
tube  by  means  of  a  glass  plunger 
working  in  an  attached  reservoir. 

The  accompanying  diagram 
shows  the  essential  features  of  con- 
struction of  the  colorimeter  em- 
ployed in  the  tests  described  below. 
The  unknown  solution  is  placed  in 
the  left-hand  tube  A,  which  is  19  cm. 
long,  3  cm.  in  diameter,  and  gradu- 
ated for  15  cm.  The  standard  solu- 
tion is  placed  in  the  right-hand 
tube  B,  which  is  the  same  size  as 
A,  the  graduated  portion  being 
divided  into  100  divisions  of  1.5  mm. 
each.  The  tube  B  is  permanently 
connected  by  a  glass  tube  with  the 
reservoir  C  in  which  the  glass 
plunger  D  works,  so  that  the  level 
of  the  liquid  in  B  can  be  readily 
controlled  by  raising  or  lowering  the 
plunger.  As  the  tube  B  and  reser- 
voir C  are  made  in  one  piece,  the 
liquid  used  for  the  standard  solution 
comes  in  contact  with  glass  only, 
thus  preventing  any  possibility  of 
chemical  change  due  to  contact  with  the  container.  The  plunger  is  provided 
with  a  rubber  collar  E,  so  placed  as  to  prevent  the  plunger  from  accidentally 
striking  and  breaking  the  bottom  of  the  reservoir.  The  tubes  A  and  B,  with 
the  connecting  reservoir,  rest  on  wooden  supports,  the  one  under  A  and  B  being 
provided  with  holes  for  the  passage  of  the  light,  and  are  held  in  position  by 
spring  clips  F  F.  This  arrangement  allows  the  glass  parts  to  be  readily  removed 
for  cleaning  and  filling.  The  light  for  illuminating  the  solution  is  reflected 
upward  through  the  tubes  A  and  B  by  means  of  the  adjustable  mirror  G.  The 
best  results  are  obtained  by  facing  the  colorimeter  toward  a  north  window  in  order 
to  get  reflected  skylight  through  the  tubes,  care  being  taken  to  avoid  light  reflected 
from  adjacent  objects.  The  black  wooden  back  of  the  colorimeter  serves  the 
double  purpose  of  a  support  for  the  parts  of  the  instrument  and  of  a  screen,  as 
it  is  interposed  between  the  color  tubes  and  the  source  of  light. 

The  light,  passing  upward  through  the  tubes  A  and  B,  impinges  on  the  two 

mirrors  H  and  I  cemented  to  brass  plates  sliding  in  grooves  cut  ?t  an  angle  of 

45°  in  the  sides  of  the  wooden  box  J.    This  box  is  supplied  with  a  loosely-fitting 

cover,  thus  allowing  easy  access  for  the  purpose  of  removing  and  cleaning  the 

1  Jour.  Am.  Chem.  Soc.,  33,  1112,  July,  1911. 


FIG.  43. — Hurley's  Colorimeter. 


246  LEAD 

mirrors.  The  mirror  H  is  cut  vertically  and  cemented  in  such  a  position  as  to 
reflect  one-half  of  the  circular  field  of  light  coming  through  the  tube  A.  The 
light  passing  upward  through  B  is  reflected  horizontally  by  the  mirror  /,  through 
a  hole  in  the  brass  plate  supporting  the  mirror  H.  One-half  of  the  circular  field 
of  light  from  the  tube  B  is  cut  off  by  the  mirror  H,  the  vertical  edge  of  which 
acts  as  a  dividing  line  between  the  two  halves  of  the  circular  field.  The  image 
of  one-half  of  the  tube  B  is  then  observed  in  juxtaposition  to  the  opposite  half 
of  the  image  of  the  tube  A. 

The  juxtaposed  images  are  observed  through  a  tube  K,  2.5  cm.  in  diameter 
and  16  cm.  long,  lined  with  black  felt  and  provided  with  an  eye-piece  having  a 
hole  1.5  mm.  in  diameter.  At  the  point  M  in  the  tube  K  is  placed  a  diaphragm 
having  an  aperture  8  mm.  in  diameter.  All  parts  inside  the  box  J  except  the 
mirrors  are  painted  black  so  that  no  light  except  that  coming  through  the  tubes 
A  and  B  passes  through  the  tube  K.  By  having  the  apertures  in  the  eye-piece 
and  diaphragm  properly  proportioned  only  the  image  of  the  bottoms  of  the 
tubes  A  and  B  can  be  seen,  thus  preventing  interference  of  light  reflected  from 
the  vertical  sides  of  the  tubes  A  and  B. 

A  person  looking  through  the  eye-piece  observes  a  single  circular  field  divided 
vertically  by  an  almost  imperceptible  line  when  the  two  solutions  are  of  the  same 
intensity.  By  manipulating  the  plunger  D,  the  level  of  the  liquid  in  B  can  be 
easily  raised  or  lowered,  thus  causing  the  right  half  of  the  image  to  assume  a 
darker  or  lighter  shade  at  will.  In  matching  colors  with  an  ascending  column 
in  B,  that  is,  gradually  deepening  the  color  of  the  right  half  of  the  field,  the 
usual  tendency  is  to  stop  a  little  below  the  true  reading  while  in  a  comparison 
with  a  descending  column  the  opposite  is  the  case. 

Procedure.  If  lead  is  between  10  to  50  parts  per  million  a  1-gram  sample 
is  taken.  If  it  is  above  or  below  these  extremes  the  amount  of  sample  is  regu- 
lated accordingly.  In  materials  containing  organic  matter  it  is  not  advisable 
to  take  more  than  a  1-gram  sample. 

Substances  containing  organic  matter,  such  as  starch  in  baking  powder, 
should  be  decomposed  by  fusion  with  sodium  peroxide,  sodium  or  potassium 
sulphate  containing  a  few  drops  of  sulphuric  acid.  A  Kjeldahl  digestion  with 
concentrated  sulphuric  acid  and  potassium  bisulphate  may  occasionally  be 
advisable.  Sulphuric  acid  discolored  by  organic  matter  should  be  mixed  with 
4  to  5  grams  of  potassium  bisulphate,  taken  to  fumes  and  then  diluted  with 
water.  The  material  may  be  extracted  with  ammonium  acetate  and  lead 
determined  in  the  extract.  See  notes. 

To  the  solution  containing  the  sample  are  added  10  cc.  of  tartrate  solution 
(or  20  cc.  of  citrate  solution  with  phosphates  of  lime,  etc.),  lOcc.  of  hydrochloric 
acid  and  the  mixture  brought  to  boiling.  Small  amounts  of  ferric  iron  are  now 
reduced  by  adding  0.5  gram  sodium  metabisulphite.  Sufficient  ammonium 
hydroxide  is  added  to  neutralize  the  free  acid  and  5  cc.  in  excess;  then  3  cc.  potas- 
sium cyanide  (to  repress  any  copper  color  that  may  be  present  to  reduce  higher 
oxides),  and  the  mixture  heated  until  the  solution  becomes  colorless.  The  entire 
solution  or  an  aliquot  portion  is  placed  in  the  comparison  cylinder,  and  diluted 
to  nearly  100  cc.  If  the  Kennicott-Sargent  apparatus  is  used  the  standard  color 
solution  is  forced  into  the  adjacent  cylinder,  until  the  color  in  this  cylinder  matches 
the  one  containing  the  sample.  The  number  of  cc.  of  the  standard  is  noted.  This 
blank  is  due  to  the  slight  color  that  the  solutions  of  the  samples  invariably  have. 
Four  drops  of  the  sulphide  reagent  are  added  to  the  sample  and  this  is  mixed 


LEAD  247 

by  means  of  a  plunger,  avoiding  any  more  agitation  than  is  absolutely  necessary 
to  make  the  solution  homogeneous.  After  one  minute  the  comparison  is  again 
made,  the  colored  standard  being  forced  into  the  cylinder  until  its  color  matches 
the  sample.  It  is  advisable  to  take  several  readings  with  ascending  and  descend- 
ing column  of  standard  reagent,  taking  the  average  as  the  true  reading. 

Calculation.  Suppose  the  standard  =0.000001  gram  Pb  per  cc.,  blank  =5  cc., 
total  reading  =22  cc.,  one  gram  of  sample  being  taken  for  analysis.  Then 
22-5  =17  cc.  =0.0017%  Pb  or  17  parts  per  million. 

NOTES.  Iron  must  be  completely  reduced  before  adding  ammonium  hydroxide 
and  potassium  cyanide. 

Allen's  method  of  reducing  iron  with  sodium  metabisulphite  is  excellent.  The  salt 
may  be  made  by  passing  SO2  into  a  saturated  solution  of  sodium  carbonate  at 
boiling  temperature,  until  the  liquor  is  just  acid  to  methyl  orange.  The  water 
evaporated  during  the  treatment  is  replaced  during  the  action.  Na2S2O5  separates 
and  may  be  filtered  off  and  the  water  removed  by  centrifuging. 


FIG.  44. — Cooper  Hewitt  Mercury  Light. 

The  Cooper  Hewitt  Mercury  light  is  excellent  for  colorimetric  lead  determina- 
tions, where  an  artificial  light  is  desired.  The  yellow  shades  appear  yellowish- 
green  and  may  be  matched  more  readily  than  the  yellows  obtained  by  daylight. 

The  illustration,  Fig.  44,  shows  the  type  of  light  recommended  for  this  work. 

If  a  separation  from  iron  is  desired,  the  lead  may  be  extracted  with  ammonium 
acetate  solution.  Ten  grams  of  the  powdered  material  are  mixed  with  75  cc.  of 
a  33%  ammonium  acetate  solution  l  (25  grams  of  the  salt  dissolved  in  50  cc.  H20), 
the  reagent  being  added  boiling  hot.  The  mixture  is  diluted  to  500  cc.,  a  portion 
filtered,  and  the  determination  made  on  an  aliquot  part  of  the  total,  following 
the  directions  above. 

1  The  ammonium  acetate  should  be  free  from  lead. 


248  LEAD 

ANALYSIS   OF   METALLIC   LEAD 
Determination  of  Impurities  in  Pig  Lead — Complete  Analysis  l 

The  following  substances  are  generally  estimated  in  the  complete  analysis 
of  lead:  silver,  bismuth,  copper,  cadmium,  arsenic,  antimony,  tin,  iron,  cobalt, 
nickel,  manganese  and  zinc. 

Determination  of  Silver 

This  is  determined  by  assay  of  100  grams  of  lead.  The  substance  is  placed 
in  a  3-in.  scorifier  and  heated  in  a  muffle  furnace  until  the  assay  "  covers."  It 
is  then  poured  into  a  mould,  allowed  to  cool  and  the  button  thus  obtained  again 
scorified  until  a  final  button  weighing  about  20  grams  is  obtained.  This  is 
cupeled  and  silver  determined  as  usual.  If  the  silver  bead  is  large  it  should  be 
parted  for  gold. 

Determination  of  Bismuth 

In  determining  bismuth  three  cases  arise:  A.  The  ordinary  method.  B. 
Procedure  for  determining  minute  amounts  of  bismuth.  C.  Method  in  presence 
of  comparatively  large  amounts  of  antimony  and  tin. 

A.  Twenty  grams  of  lead  are  dissolved  in  100  cc.  of  hot  dilute  nitric  acid 
(1  :  4).     If  the  solution  is  complete,  dilute  ammonium  hydroxide  is  added,  drop 
by  drop,  until  a  faint  opalescence  is  observed  in  the  solution.     If  a  precipitate  is 
formed,  this  must  be  dissolved  by  addition  of  nitric  acid  and  the  ammonia 
treatment  repeated.     Now  5  cc.  of  dilute  hydrochloric  acid  are  added  (1:9) 
and  the  solution  diluted  to  400  cc.  and  heated  to  boiling.     The  bismuth  oxy- 
chloride  is  allowed  to  settle  on  the  steam  bath  for  several  hours,  the  clear  solu- 
tion is  then  decanted  through  a  7  cm.  filter  (S.  &  S.  No.  589),  the  precipitate 
transferred  to  the  paper  and  washed  with  hot  water.     (The  solution  is  refiltered 
if  cloudy.)     The  precipitate  is  dissolved  with  5  cc.  hot  hydrochloric  acid  (1  :  9), 
the  acid  being  added  around  the  edge  of  the  filter  with  a  pipette.     The  pa] XT 
is   washed   and   the   solution   diluted   to   400  cc.   and  brought  to  boiling.     The 
precipitate  is  filtered  into  a  weighed  Gooch  crucible,  washed  several  times  with 
water,  then  once  with  alcohol  and  finally  with  ether.     It  is  dried  in  the  oven  and 
weighed  as  BiOCl. 

BiOClX.802=Bi. 

B.  Determination  of  minute  amounts  of  bismuth  is  made  as  follows:    100 
grams  of  lead  are  dissolved  in  500  cc.  of  dilute  nitric  acid  (1  :  4),  and  the  cooled 
solution  treated  with  sufficient  saturated  solution  of  sodium  carbonate  to  pro- 
duce a  heavy  precipitate.    After  settling,  then  decanting  off  the  clear  solution, 
the  precipitate  is  filtered  onto  a  filter  and  drained.    Without  washing  this  is 
dissolved  with  the  least  amount  of  nitric  acid  that  is  required.     The  solution  is 
then  neutralized  with  ammonia  as  before  (method  A),  litmus  paper  being  used 
as  an  indicator,  and  bismuth  determined  as  directed  under  the  first  procedure. 

C.  In  presence  of  considerable  amounts  of  antimony  and  tin,  the  bismuth  is 
precipitated  as  in  case  A,  the  precipitate  dissolved  in  hot  hydrochloric  acid 
(1  :  2),  and  the  solution  diluted  to  200  cc.    The  sulphides  of  antimony,  tin,  etc., 

1  Method  of  the  National  Lead  Company,  modified. 


LEAD  249 

are  precipitated  with  H2S,  antimony  and  tin  dissolved  out  with  a  solution  of 
potassium  hydroxide  and  sulphide  water  (1  part  20%  KOH  to  4  parts  H2S  water), 
and  the  residue  washed.  This  is  dissolved  in  20  cc.  of  hot  nitric  acid  (1  :  4),  and 
bismuth- determined  as  usual  in  the  nitrate. 

Determination  of  the  Remaining  Elements 

222.23  grams  of  the  sample  of  lead  are  dissolved  in  1100  cc.  of  dilute  nitric 
acid  (1  :  4)  in  a  large  beaker.  If  the  solution  is  turbid,  appreciable  amounts 
of  antimony  and  tin  are  indicated  with  possible  sulphur  combined  as  PbS04. 
In  this  case  it  is  filtered  into  a  2000-cc.  flask.  If  the  solution  is  clear  it  is 
transferred  directly  to  the  flask. 

Residue  I.     May  contain  As,  Sb,  Sn,          Filtrate  I.    Contains  all  the  elements 
PbSC>4.  present  in  the  sample. 

Residue  I.  The  residue  and  filter  is  treated  with  20  cc.  of  tartaric  acid 
mixture  (50  grams  tartaric  acid,  250  cc.  of  water  and  250  cc.  of  concentrated 
hydrochloric  acid).  After  boiling  the  mixture  is  digested  on  the  steam  bath  for 
half  an  hour,  then  50  cc.  of  hot  water  added  and  the  solution  filtered.  The  filter 
paper  is  ignited  and  any  residue  is  dissolved  by  fusion  with  1  gram  of  potassium 
hydroxide  in  a  silver  dish.  The  water  extract  of  this  fusion  is  added  to  the  tar- 
trate  solution.  Now  ammonia  is  added  until  the  solution  is  alkaline  and  then 
hydrochloric  acid  until  it  is  slightly  acid.  Hydrogen  sulphide  is  now  passed  in 
to  saturation,  the  precipitate  digested  on  the  steam  bath  for  fifteen  to  twenty 
minutes  and  hydrogen  sulphide  again  passed  into  the  solution  about  fifteen 
minutes.  The  sulphides  are  filtered  off,  arsenic,  antimony  and  tin  sulphides  dis- 
solved with  5  cc.  (1  :  5)  potassium  hydroxide  in  25  cc.  of  saturated  H2S  water. 
The  solution  is  diluted  to  111  cc.,  and  100  cc. — equivalent  to  200  grams  of  sam- 
ple— preserved  for  subsequent  analysis.  This  solution  is  marked  "  Extract  C." 

Filtrate  I.  This  solution,  containing  practically  all  of  the  material,  is 
treated  with  150  cc.  of  dilute  sulphuric  acid  (1  :  1),  and  the  solution  made  to 
volume — 2000  cc.  It  is  now  transferred  to  a  3-liter  flask,  the  graduated  flask 
rinsed  out  into  the  main  solution  with  50  cc.  of  water.  (The  PbS04  precipitate 
found  to  occupy  space  of  50  cc.)  When  the  precipitate  has  settled,  1800  cc. 
are  decanted  off.  This  represents  200  grams  of  the  sample.  The  solution  is 
boiled  down  in  a  No.  9  porcelain  evaporating  dish,  heating  first  over  the  free 
flame  and  finally  on  the  steam  bath  until  only  a  moist  residue  remains.  Fifty 
cc.  of  water  is  added,  the  residue  transferred  to  a  beaker  and  digested  for  several 
hours,  preferably  overnight,  and  then  filtered. 

Residue  II.    This  may  contain  PbS04,        Filtrate    II.    This  may  contain  Cu, 
As,  Sb,  Sn  salts.  Bi,   Cd,   Sn,   Sb,  As,   Fe,   Co,   Ni 

and  Zn. 

Residue  II.  This  is  treated  as  has  been  described  for  residue  I.  The 
entire  solution  is  added  to  the  Extract  C.  The  residue,  consisting  of  PbS04,  is 
rejected. 

Filtrate  II.  This  is  made  neutral  with  ammonium  hydroxide  and  then  con- 
centrated hydrochloric  acid  added  in  such  an  amount  that  the  solution  will 
contain  4%  free  acid.  (HC1  sp.gr.  1.2,  4  cc.  per  100  of  solution.)  Hydrogen 
sulphide  is  now  passed  into  the  hot  solution  until  it  is  saturated,  the  precipitate 


250  LEAD 

settled  on  the  steam  bath  for  half  an  hour  and  hydrogen  sulphide  again  passed 
in  for  fifteen  minutes.  The  precipitate  is  filtered  off  and  washed  with  H2S 
water  slightly  acidified  with  hydrochloric  acid. 

Residue     III.    May     contain     CuS,        Filtrate    III.     May  contain  ions   of 
Bi2S3,  CdS,  As2S3,  Sb2S3,  SnS.  Fe,  Al,  Co,  Ni,  Mn  and  Zn.    This 

filtrate  is  marked  "  B." 

Residue  III.  The  sulphides  are  extracted  with  potassium  hydroxide  and 
hydrogen  sulphide  solution.  This  dissolves  out  arsenic,  antimony  and  tin.  This 
extract  is  combined  with  the  extract  marked  "  C." 

The  residue  remaining  is  marked  "  Residue  A." 

The  constituents  of  the  sample  have  now  been  isolated  in  the  groups. 

Residue  "  A  "  contains  the  sulphides  of  copper,  bismuth  and  cadmium. 

Filtrate  "  B  "  contains  such  elements  as  do  not  precipitate  as  sulphides  in 
acid  solution — iron,  aluminum,  manganese,  cobalt,  nickel  and  zinc. 

Extract  "  C  "  includes  the  elements  arsenic,  antimony  and  tin. 

Determination  of  Arsenic,  Antimony,  and  Tin  in  Pig  Lead 

The  combined  alkali  sulphide  solutions:  "Extract  C"  is  washed  into  a 
beaker  and  acidified  with  20  cc.  of  nitric  acid  and  5  cc.  of  hydrochloric  acid. 
The  solution  is  evaporated  to  dryness  on  the  steam  bath.  The  residue  is  dissolved 
in  200  cc.  of  water  and  10  grams  of  oxalic  acid  added,  together  with  10  grams 
of  ammonium  oxalate,  and  the  solution  heated  until  clear. 

Hydrogen  sulphide  gas  is  now  passed  into  the  hot  solution  for  forty-five 
minutes. 

Precipitate.    As2S3,  Sb2S3.  Filtrate  contains  Sn. 

Arsenic.  The  precipitate  containing  arsenic  and  antimony  is  placed  in  a 
distilling  flask,  strong  hydrochloric  acid  added  and  arsenic  separated  from 
antimony  by  distillation  with  a  current  of  HC1  gas  according  to  the  regular  pro- 
cedure. If  a  precipitate  of  arsenic  sulphide  forms  in  the  distillate,  it  is  advis- 
able to  precipitate  the  arsenic  as  sulphide,  oxidize  the  compound  to  form 
sulphate  and  arsenic  acid,  and  after  reduction  of  the  arsenic  to  titrate  it  with 
standard  iodine.  This  oxidation  may  be  accomplished,  before  distillation  with 
hydrochloric  acid.  For  details  of  the  procedure  see  chapter  on  Arsenic,  page  33. 

Antimony  is  determined  in  the  residue  in  the  flask  by  titration  with  N/10 
potassium  bromate  or  by  the  potassium  iodide  method. 

I.  2KBr03+2HCl+3Sb203  =2KCl+2HBr+3Sb206. 
II.  (a)  Sb2Cl6+2KI=Sb2Cl3+2KCl+I2. 
(6)  I2+2Na2S203=2NaI+Na2S406. 

For  details  of  the  procedure  see  chapter  on  Antimony,  pages  25  and  26. 

Determination  of  Copper  and  Cadmium  in  Pig  Lead 

The  residue  "  A  "  is  taken  for  this  analysis.  If  copper  exceeds  0.0025% 
method  I  is  used.  If  the  copper  percentage  is  below  this  amount  the  procedure 
II  is  followed. 


LEAD  251 

Method  I.  The  residue  is  dissolved  by  heating  with  20  cc.  of  nitric  acid 
(1:4)  and  the  solution  filtered  into  a  beaker.  The  filter  is  ignited  and  the 
residue  dissolved  in  nitric  acid  (1:1)  and  the  solution  added  to  the  first  por- 
tion. Xhe  volume  should  not  exceed  100  cc.  Ammonium  hydroxide  is  added 
until  the  solution  is  strongly  ammoniacal  and  then  5  grams  of  potassium  cyanide. 
Hydrogen  sulphide  is  passed  into  the  cold  solution  to  saturation,  and  the 
solution  filtered. 

Precipitate  =AgS,  Bi2S3,  CdS.  Filtrate  =Cu  in  solution. 

The  filtrate  containing  the  copper  is  evaporated  on  the  steam  bath  to  a 
volume  of  20  to  30  cc.  in  a  4-in.  casserole.  Now  20  cc.  of  sulphuric  acid  (1  :  1) 
are  added  (hood),  and  the  solution  evaporated  until  S03  fumes  are  evolved. 
The  cooled  concentrate  is  diluted  with  water  and  filtered,  if  necessary.  Three  cc. 
of  nitric  acid  are  added  per  100  cc.  of  solution  and  the  copper  deposited  by 
electrolysis  according  to  the  regular  procedure  and  weighed  as  metallic  copper. 
For  detailed  method  see  chapter  on  Copper,  page  155. 

The  precipitate  containing  silver,  bismuth  and  cadmium  is  dissolved  in  20  cc. 
of  nitric  acid  (1  :  4),  1  cc.  of  1%  sodium  chloride  solution  is  added,  the  solution 
digested  half  an  hour  and  then  filtered  and  the  filter  washed  with  water. 

Precipitate -AgCl,  reject.  Filtrate  -Cd(NO3)2  and  Bi(N03)3. 

The  filtrate  is  made  slightly  alkaline  with  sodium  carbonate  added  in  slight 
excess,  and  5  grams  of  potassium  cyanide  are  then  added.  After  digesting  on  the 
steam  bath  for  half  an  hour  the  solution  is  filtered  and  the  residue  washed  with 
5%  sodium  carbonate  solution. 

Precipitate  contains  bismuth,  reject.  Filtrate  contains  cadmium. 

The  filtrate  is  now  treated  with  a  few  cc.  of  ammonium  sulphide  and  the 
yellow  cadmium  sulphide  is  filtered  into  a  weighed  Gooch  crucible,  then  washed, 
dried  and  finally  weighed  as  CdS. 

CdS  X  0.778  =Cd. 

Method  II.  Small  amounts  of  copper.  The  filter  containing  the  sulphides 
is  ignited  in  a  porcelain  crucible  and  the  residue  dissolved  in  5  to  10  cc.  of  nitric 
acid  (1  :  1),  and  the  solution  evaporated  to  pastiness.  One  cc.  of  sulphuric  acid 
(1  :  1)  is  added  together  with  a  few  drops  of  10%  sodium  chloride  solution  and  the 
mixture  evaporated  to  S03  fumes,  the  cooled  product  then  diluted  with  water 
and  filtered  from  the  lead  and  silver  precipitates. 

Ammonia  is  now  added  to  the  filtrate  together  with  5  grams  of  potassium 
cyanide  and  CdS  and  Bi2S3  are  precipitated  with  H2S,  as  in  case  I,  and  filtered  off. 

Precipitate — CdS    and    Bi2S3.    Bis-  Filtrate.    The  solution  is  made  acid 

muth    is    removed    as    before    and  in  the  hood  with  H2S04,  then  taken 

cadmium    sulphide    again    precipi-  to  S03  fumes  and  copper  determined 

tated    and    the  compound   titrated  by  the  potassium  iodide  method, 
with  N/10  iodine  solution. 
1  cc.  N/10  1=0.00562  gram  Cd. 


252 


LEAD 


Determination  of  Iron,  Cobalt,  Nickel,  Manganese  and 
Zinc  in  Pig  Lead 

Iron  and  Alumina.  The  filtrate  "  B  "  from  members  of  the  Hydrogen 
Sulphide  Group  is  evaporated  to  100  and  the  iron  oxidized  with  a  few  drops  of 
nitric  acid  as  usual.  Iron  (and  alumina)  hydroxide  is  now  precipitated  by  addition 
of  ammonia.  It  is  advisable  to  dissolve  this  precipitate  in  hydrochloric  acid  and 
reprecipitate  the  iron  to  recover  the  occluded  manganese  and  zinc.  The  com- 
bined filtrates  are  reserved  for  the  determination  of  the  remainder  of  the  elements. 
The  hydroxide  of  iron  is  ignited  and  weighed  as  Fe203.  If  alumina  is  suspected, 
the  residue  is  dissolved  in  hydrochloric  acid  and  iron  determined  volume trically. 
Fe203  thus  obtained  is  subtracted  from  the  weight  of  the  first  determination, 
the  difference  being  due  to  the  alumina  present. 


Fe203X  0.6994  =Fe 
A1.0.X  0.5303   =A1 


Reciprocal  factor  =  1 .4298 
Reciprocal  factor  =  1.8856 


Zinc.  The  filtrate  from  iron  precipitate  is  made  neutral  with  hydrochloric 
acid  and  then  15  drops  of  2N.  HC1  added  in  excess  and  zinc  precipitated  in  the 
pressure  flask  with  H2S.  (See  Figs.  3  and  4  in  chapter  on  Arsenic.)  The 
sulphide  of  zinc  is  filtered  off,  and  either  ignited  to  the  oxide  ZnO  and  so  weighed 
or  determined  by  a  volumetric  procedure.  See  chapter  on  Zinc. 

ZnO  X  0.8034  =Zn. 
H2S04X0.6665=Zn. 

Cobalt  and  Nickel.  These  are  best  determined  by  electrolysis,  being  deposited 
from  an  ammonium  sulphate  solution  according  to  the  procedure  described  for 
these  elements. 

If  a  separation  of  the  elements  is  desired  the  deposit  is  dissolved  in  acid, 
nickel  determined  by  0.  Brunck's  dimethylglyoxime  method,  and  cobalt  deter- 
mined by  difference. 

Manganese.  The  solution  from  nickel  and  cobalt  is  taken  to  dryness,  and  the 
residue  heated  to  expel  the  ammonium  salts  and  destroy  any  organic  matter 
present.  This  is  taken  up  with  a  little  hydrochloric  acid,  then  2  to  3  cc.  of 
sulphuric  acid  added  and  the  mixture  evaporated  to  S03  fumes  to  expel  the  hydro- 
chloric acid.  When  nearly  all  the  free  acid  is  driven  off,  the  moist  residue,  cooled, 
is  treated  with  50  cc.  of  nitric  acid  (1  :  3),  and  manganese  determined  in  the 
solution  preferably  by  the  bismuthate  method.  For  minute  amounts  of  man- 
ganese the  colorimetric  procedure  is  used.  See  chapter  on  Manganese,  page  267. 


MAGNESIUM 

WILFRED  W.  SCOTT 
Mg,  at.wt.  24.33;  sp.gr.  1.69-1.75;  m.p.  651°  *;  b.p.  1120°  C.2;  oxide  MgO. 

DETECTION 

In  the  usual  course  of  analysis  magnesium  is  found  in  the  nitrate  from  the 
precipitated  carbonates  of  barium,  calcium,  and  strontium.  The  general  procedure 
for  removal  of  the  preceding  groups  may  be  found  in  the  section  on  Separa- 
tions given  on  the  following  page,  254.  Magnesium  is  precipitated  as  white 
magnesium  ammonium  phosphate,  MgNH4P04,  by  an  alkali  phosphate,  Na2HP04, 
NaNH4HP04,  etc.,  in  presence  of  ammonium  chloride  and  free  ammonia.  The 
precipitate  forms  slowly  in  dilute  solution.  This  is  hastened  by  agitation  and 
by  rubbing  the  sides  of  the  beaker  during  the  stirring  with  a  glass  rod.  Crystals 
soon  appear  on  the  sides  of  the  beaker  in  the  path  of  contact,  and  finally  in 
the  solution. 

Baryta  or  lime  water  added  to  a  solution  containing  magnesium  produces 
a  white  precipitate  of  magnesium  hydroxide. 

Both  the  phosphate  and  the  hydroxide  of  magnesium  are  soluble  in  acids. 

ESTIMATION 

The  element  is  determined  in  the  complete  analysis  of  a  large  number  of 
substances;  in  the  analysis  of  ores,  minerals,  rocks,  soils,  cements,  water,  etc. 
The  following  are  the  more  important  ores  in  which  the  element  occurs:  Mag- 
nesite,  MgC03;  dolomite,  CaC03-MgC03;  kieserite,  MgS04-H20;  kainite, 
MgS04-KCl-6H20;  carnallite,  MgCl2  •  KC1  •  6H20 ;  in  the  silicates,  enstatite, 
MgSi03;  talc,  H2Mg3(Si02)4;  meerschaum,  forsterite,  Mg2Si04;  titanate,  MgTi03; 
olivine,  Mg2Si04-Fe2Si04;  serpentine,  H4Mg3Si204.  It  occurs  as  boracite, 
4MgB407-2MgO-MgCl2.  It  is  found  in  sea-water,  and  in  certain  mineral  waters. 
It  occurs  as  a  phosphate  and  carbonate  in  the  vegetable  and  animal  kingdoms, 
especially  in  seeds  and  bones. 

Preparation  and  Solution  of  the  Sample 

In  solution  of  the  material  it  will  be  recalled  that  the  metal  is  soluble  in 
acids  and  is  also  attacked  by  the  acid  alkali  carbonates.  It  is  soluble  in  am- 
monium salts.  The  oxide,  hydroxide,  and  the  salts  of  magnesium  are  soluble 
in  acids.  Combined  in  silicates,  however,  the  substance  requires  fusion  with 
alkali  carbonates  to  bring  it  into  solution. 

General  Procedure  for  Ores.  One  gram  of  the  ore  is  treated  with  20  cc.  of 
strong  hydrochloric  acid  and  heated  gently  until  the  material  is  decomposed. 
If  sulphides  are  present,  5  to  10  cc.  of  strong  nitric  acid  are  added  and  the  material 
decomposed  by  the  mixed  acids.  If  silicates  are  present  and  the  decompo- 

1  Circular  35  (2d  Ed.)  U.  S.  Bureau  of  Standards. 

2  Van  Nostrand's  Chem.  Annual — Olsen. 

253 


254 


MAGNESIUM 


sition  is  not  complete  by  the  acid  treatment,  the  insoluble  material  is  decom- 
posed by  fusion  with  sodium  carbonate,  or  the  entire  sample  may  be  fused  with 
the  alkali  carbonate,  the  fusion  is  dissolved  in  hydrochloric  acid  and  taken  to 
dryness.  Silica  is  dehydrated  as  usual  by  heating  the  residue  from  the  evaporated 
solution.  This  is  taken  up  with  50  cc.  of  water  containing  about  5  cc.  strong 
hydrochloric  acid,  the  silica  filtered  off  and,  after  removal  of  the  interfering  sub- 
stances according  to  procedures  given  under  the  next  section  on  Separations, 
magnesium  is  determined  as  directed  in  the  sections  on  Methods. 

SEPARATIONS 

Removal  of  Members  of  the  Hydrogen  Sulphide  Group.  Copper,  Lead, 
Bismuth,  Cadmium,  Arsenic,  etc.  The  filtrate  from  silica 1  is  diluted  to  about 
200  cc.  and  hydrogen  sulphide  gas  passed  in  until  the  members  of  this  group 
are  completely  precipitated.  The  sulphides  are  filtered  off  and  washed  with  H2S 
water  and  the  filtrate  and  washings  concentrated  by  boiling.  This  treatment 
is  seldom  necessary  in  analysis  of  many  silicates  and  carbonates  in  which  these 
elements  are  absent. 

Removal  of  Iron,  Aluminum,  Manganese,  Zinc,  etc.  The  concentrated 
nitrate  from  the  hydrogen  sulphide  group,  or  in  case  the  treatment  with  hydro- 
gen sulphide  was  not  required,  the  nitrate  from  silica,  is  boiled  with  a  few  cc. 
of  nitric  acid  to  oxidize  the  iron  (solution  turns  yellow),  about  5  cc.  of  concentrated 
hydrochloric  acid  added,  and  if  manganese  is  present,  15  to  20  cc.  of  a  saturated 
solution  of  bromine  water,  and  the  solution  made  alkaline  to  precipitate  iron, 
aluminum,  manganese.  If  zinc,  cobalt,  and  nickel  are  present,  these  are  best 
removed  as  sulphides  by  passing  hydrogen  sulphide  into  the  ammoniacal  solu- 
tion under  pressure.  (See  Fig.  3  and  Fig.  4,  pages  38  and  39.) 

Separation  of  Magnesium  from  the  Alkaline  Earths.  The  alkaline 
earths  are  precipitated  either  as  oxalates,  recommended  when  considerable 
calcium  is  present,  or  as  sulphates,  recommended  in  presence  of  a  large  pro- 
portion of  barium,  the  magnesium  salts  being  soluble.  Magnesium  is  pre- 
cipitated from  the  filtrates  as  a  phosphate,  according  to  directions  given  later. 
Details  of  the  separation  of  magnesium  from  the  alkaline  earths  may  be  found 
in  the  chapter  on  Barium,  page  53. 

An  excellent  procedure  for  the  separation  by  means  of  sulphuric  acid  is 
to  evaporate  the  solution  to  dryness,  concentrating  first  in  a  porcelain  dish  and 
finally  to  dryness  in  a  platinum  dish,  and  then  adding  about  50  cc.  of  80% 
alcohol  and  sufficient  sulphuric  acid  to  combine  with  the  alkaline  earths  and 
magnesium,  with  slight  excess.  This  precipitates  barium,  strontium,  and  cal- 
cium as  sulphates,  while  the  greater  part  of  the  magnesium  is  in  solution. 
After  settling,  the  precipitate  is  filtered  and  washed  free  of  sulphuric  acid  by 
means  of  absolute  alcohol,  then  with  40%  alcohol  to  remove  any  magnesium 
sulphate  remaining  with  the  precipitate.  Magnesium  is  determined  in  the 
filtrate  by  expelling  the  alcohol  by  evaporation,  and  then  precipitating  as  mag- 
nesium ammonium  phosphate  according  to  directions  given  for  the  determination 
of  this  element. 

NOTE.  Magnesium  is  prevented  from  precipitation  as  a  hydroxide  by  the  presence 
of  ammonium  salts.  See  note,  bottom  of  page  8. 

1  See  previous  paragraph. 


MAGNESIUM  255 


GRAVIMETRIC  DETERMINATION   OF   MAGNESIUM 

Precipitation  of  Magnesium  by  a  Soluble  Phosphate  as 
Ammonium  Magnesium  Phosphate 

Magnesium  is  determined  in  the  nitrate  from  calcium  oxalate  by  the  addition 
of  sodium  ammonium  phosphate  to  a  hot  slightly  acid  or  neutral  solution  followed 
by  a  definite  amount  of  ammonia.  The  practice  of  precipitating  magnesium  from 
a  cold  solution  necessitates  a  double  precipitation  as  the  composition  of  the 
phosphate  is  considerably  modified  by  that  of  the  solution  in  which  the  precipi- 
tation takes  place,  so  that  it  is  necessary  to  adjust  conditions  by  having  a 
definite  amount  of  ammonia,  ammonium  salts  and  phosphate  for  the  approxi- 
mate amount  of  magnesium  present.1  Accurate  results  are  obtained  by  pre- 
cipitation of  the  compound  from  a  hot  solution  by  the  method  of  B.  Schmitz,2 
by  addition  of  the  soluble  phosphate  to  a  slightly  acid  solution  and  then  mak- 
ing ammoniacal,  or  that  of  W.  Gibbs,3  by  precipitation  of  the  amorphous 
magnesium  hydrogen  phosphate  in  a  neutral  solution  and  transforming  the  pre- 
cipitate to  magnesium  ammonium  phosphate  by  addition  of  ammonia  to  the  hot 
solution.  Upon  ignition  of  the  precipitate,  magnesium  pyrophosphate  (Mg2P207) 
is  formed. 

Reactions. 

A.  Na2NH4P04+MgCl2=2NaCl+MgNH4P04  (B.  Schmitz). « 

B.  NaHNH4P04+Mga2=NaCl+NH4Cl+MgHP04  and 
MgHP04+NH3=MgNH4P04  (W.  Gibbs).* 

Decomposition  with  Heat. 

2MgNH4P04  =  2NH3+H20+Mg2P207. 

The  following  procedure  gives  accurate  results. 

Procedure.  The  neutral  or  slightly  acid  solution,  containing  magnesium  in 
presence  of  ammonium  salts,  is  heated  to  boiling  and  treated,  drop  by  drop,  with 
an  excess  of  sodium  or  ammonium  phosphate,  or  microcosmic  salt  (10%  solutions), 
stirring  constantly  during  the  addition.  Then  ammonium  hydroxide  (sp.gr.  0.96) 
is  added,  its  volume  measuring  one-third  that  of  the  magnesium  solution.  The 
crystalline  precipitate  is  allowed  to  cool  and  settle  for  two  hours  or  more.  The 
supernatant  liquid  is  filtered  off,  the  precipitate  washed  by  decantation  two  or 
three  times,  then  transferred  to  the  filter,  using  dilute  ammonia  water  (2%).  The 
precipitate  is  dried  and  then  transferred  as  completely  as  possible  to  a  weighed 
platinum  crucible,  the  ash  of  the  filter  paper,  burned  separately,  is  added  and  the 
compound  heated  gently  at  first,  the  crucible  being  covered  until  the  ammonia 
is  driven  off,  and  then  more  strongly  until  the  mass  is  snow  white.  The  residue 
is  cooled  in  a  desiccator  and  weighed  as  Mg2P20/.  The  ammonium  magnesium 
phosphate  may  be  filtered  directly  into  a  weighed  Gooch  crucible  and  ignited, 
thus  avoiding  the  carbon  of  the  filter  paper,  and  shortening  the  period  of  ignition, 
less  heat  being  required  to  obtain  the  white  magnesium  pyrophosphate. 

1  F.  A.  Gooch  and  M.  Austin,  Am.  Jour.  Sci.  (4),  7,  187,  1899.  W.  Gibbs,  C.  N.  28, 
51, 1873.     H.  Struve,  Zeit,  anal.  Chem.,  36,  289,  1897. 

2  Z.  anal.  Chem.,  512,  1906.  3  Am.  Jour.  Sci.  (3),  5,  114,  1873. 

4  Details  of  the  two  methods  maybe  found  inTreadwell  &  Hall,  "Analytical  Chemistry." 


256 


MAGNESIUM 


Factors.1    Mg2P207X 0.3621  =MgO  or  0.2184  =Mg  or  X0.7572 

=  MgC03or  XI. 0811  =MgS04  or  X 2.2143  =  MgS04-7H20. 

Notes  on  Magnesium 

The  ignition  is  conducted  gently  at  first  to  gradually  oxidize  the  carbon  that  the 
precipitate  contains.  With  rapid  ignition  the  particles  are  inclosed  in  the  mass  in  a 
form  that  it  is  almost  impossible  to  completely  oxidize,  so  that  the  final  residue  is 
gray  instead  of  white.  L.  L.  de  Koninck  2  considers  that  the  blackening  of  the  precipi- 
tate is  frequently  due  to  the  presence  of  organic  bases  in  commercial  ammonia  and 
its  salts,  rather  than  to  the  fibers  of  filter  paper  occluded  in  the  mass.  With  caution, 
the  filter  and  residue  may  be  ignited  wet,  the  heat  being  low  until  the  filter  completely 
chars  and  then  being  increased,  with  the  cover  removed,  until  the  residue  is  white. 

Impurities.  The  precipitate  may  contain  traces  of  lime  that  remained  soluble 
in  ammonium  oxalate.  This  may  be  determined  by  dissolving  the  pyrophosphate 
in  dilute  sulphuric  acid  followed  by  addition  of  9  to  10  volumes  of  absolute  alcohol. 
Calcium  sulphate,  CaSO4,  precipitates  and  settles  out  on  standing  several  hours.  It 
may  be  filtered  off,  dissolved  in  hydrochloric  acid  and  precipitated  as  oxalate  in  the 
usual  way  and  so  determined. 

A  residue  remaining  after  treating  the  pyrophosphate  with  acid  is  generally  SiO2. 

The  presence  of  manganese  may  be  detected  by  dissolving  the  magnesium  pyro- 
phosphate, Mg2P2Oy,  in  nitric  acid  and  oxidizing  with  sodium  bismuthate.  (See 
method  under  Manganese.) 

Properties  of  Ammonium  Magnesium  Phosphate.  Readily  soluble  in  dilute 
acids.  One  hundred  cc.  of  pure  water  at  10°  C.  will  dissolve  0.0065  gram.  The 
presence  of  ammonia  greatly  decreases  the  solubility  of  the  salt,  e.g.,  2.5%  ammonia 
decreases  the  solubility  to  0.00006  gram  MgO  per  100  cc.  The  presence  of  ammonium 
salts  increase  the  solubility  of  the  precipitate,  e.g.,  1  gram  of  ammonium  chloride 
will  increase  the  solubility  to  0.0013  gram  MgO.3 


VOLUMETRIC   DETERMINATION    OF    MAGNESIUM 

Titration  of  the  Ammonium  Magnesium  Phosphate  with 
Standard  Acid 

The  procedure  known  as  Handy's  volumetric  method  for  magnesium,4  depends 
upon  the  reaction  MgNHJXX+ILSO^MgSO.+NHJ^PO,.  An  excess  of 
standard  sulphuric  acid  is  added  to  the  precipitate  and  the  excess  of  acid  titrated 
back  with  standard  ammonium  hydroxide. 

Procedure.  The  method  of  precipitation  of  the  magnesium  ammonium 
phosphate  is  the  same  as  has  been  described  under  the  gravimetric  method.  The 
precipitate  is  washed  several  times  by  decantation  with  10%  ammonium  hydrox- 
ide solution  (1  part  NH4OH,  sp.gr.  0.90  to  9  parts  water),  and  finally  on  the 
filter.  After  draining,  the  filter  is  opened  out,  the  moisture  removed  as  much  as 
possible  by  means  of  dry  filter  papers.  The  residue  may  be  dried  in  the  room 
for  about  forty-five  minutes  or  in  the  air  oven  at  50  to  60°  C.  for  fifteen  to 
twenty  minutes.6  When  the  filter  has  dried,  ammonia  will  have  been  expelled. 
The  substance  is  placed  in  a  dry  beaker,  N/10  sulphuric  acid  added  in  excess 
(methyl  orange  indicator),  the  solution  diluted  to  100  cc.  and  the  excess  of  acid 
titrated  with  N/10  sodium  hydroxide. 

One  cc.  N/10  H2S04  =0.002  gram  MgO. 

1  Based  on  atomic  weights  of  1916. 

2Zeit.  analy.  Chem.,  29, 165,  1890. 

3Mellor,  "Quantitative  Inorganic  Analysis,"  J.  B.  Lippincott  Co.,  Pub. 

4  James  Otis  Handy,  Jour.  Ani.  Chem.  Soc.,  22,  31. 

6  Low,  "Technical  Methods  of  Ore  Analysis,"  Wiley  &  Sons,  Pub. 


MANGANESE 

WILFRED  W.  SCOTT 

Mn,  at.wt.  54.93;  sp.gr.  7.431;  m.p.  1260°  2;  b.p.  1900°  C  l  ;  oxides,  MnO, 
Mn2O3,  (Mn3O4  ignition  in  air],  MnO2,  MnO3,  Mn2O7. 

DETECTION 

In  the  usual  course  of  analysis  manganese  is  found  in  the  nitrate  from  the 
hydroxides  of  iron,  aluminum  and  chromium,  the  previous  groups  having  been 
removed  with  hydrochloric  acid,  hydrogen  sulphide  and  ammonium  hydroxide  in 
presence  of  ammonium  chloride.  Manganese,  cobalt,  nickel  and  zinc  are  pre- 
cipitated as  sulphides  in  an  ammoniacal  solution.  The  sulphides  of  manganese 
and  zinc  are  dissolved  by  cold  dilute  hydrochloric  acid,  H2S  expelled  by  boiling 
and  manganese  precipitated  as  the  hydroxide  by  addition  of  potassium  hydroxide 
in  sufficient  amount  to  dissolve  the  zinc  (sodium  zincate).  Manganese  is  now 
confirmed  by  dissolving  this  precipitate  in  nitric  acid  and  adding  red  lead  or 
lead  peroxide  to  the  strong  nitric  acid  solution.  A  violet-colored  solution  is  pro- 
duced in  presence  of  manganese.  Chlorides  should  be  absent. 

Manganese  in  soils,  minerals,  vegetables,  etc.,  is  detected  by  incinerating 
the  substance,  treating  the  ash  with  nitric  acid  and  taking  to  dryness,  the  residue 
is  taken  up  with  water  and  the  mixture  filtered.  To  the  filtrate  is  added  a  few 
cc.  of  40%  ammonium  persulphate  and  a  little  2%  silver  nitrate  solution.  A 
pink  color  is  produced  in  presence  of  manganese. 

Manganese  compounds  heated  with  borax  in  the  oxidizing  flame  produce 
an  amethyst  red  color.  The  color  is  destroyed  in  the  reducing  flame. 

Fused  with  sodium  carbonate  and  nitrate  on  a  platinum  foil  manganese 
compounds  produce  a  green-colored  fusion  ("robin  egg  blue")- 

ESTIMATION 

Manganese  may  be  determined  accurately  gravimetrically  or  volumetrically. 
The  former  methods  may  be  used  for  high-grade  manganese  ores,  the  latter  are 
generally  preferred  for  determining  manganese  in  steel  and  in  alloys  and  are 
applicable  to  a  wide  range  of  substances. 

The  most  important  ore  of  manganese  is  pyrolusite,  Mn02.  Other  ores  are 
braunite,  Mn203;  hausmannite,  Mn304;  manganite,  Mn203-H20;  albanite, 
MnS;  haurite,  MnS2;  dialogite,  MnC03;  rhodonite,  MnSi03. 

Speigeleisen  or  ferromanganese  is  an  important  alloy  for  the  steel  industry. 
In  addition  to  the  requirement  of  the  element  in  the  analysis  of  the  above  sub- 
stances it  is  determined  in  certain  paint  pigments  —  green  and  violet  manganous 
oxides,  in  dryers  of  oils,  etc.  It  occurs  in  a  number  of  alloys. 


Nostrand's  Chem.  Annual  —  Olsen. 
2  Circular  35  (2d  Ed.)  U.  S.  Bureau  of  Standards, 
257 


258  MANGANESE 


Preparation  and  Solution  of  the  Sample 

In  dissolving  the  sample  the  following  facts  will  be  recalled:  The  metal 
dissolves  in  dilute  acids,  forming  manganese  salts.  The  oxides  and  hjrdroxides 
of  manganese  are  soluble  in  hot  hydrochloric  acid.  Manganous  oxide  is  soluble 
in  nitric  or  in  sulphuric  acid;  the  dioxide  is  insoluble  in  dilute  or  concentrated 
nitric  acid,  but  is  soluble  in  hot  concentrated  sulphuric  acid. 

Ores  of  Manganese.  A  sample  of  powdered  ore  weighing  1  gram  is  brought 
into  solution  by  digesting  with  25  to  50  cc.  of  strong  hydrochloric  acid  for  fifteen 
to  thirty  minutes  on  the  steam  bath.  If  much  silica  is  present  5  to  10  cc.  hydro- 
fluoric acid  will  assist  solution.  Five  cc.  of  sulphuric  acid  are  added  and  the 
mixture  evaporated  and  heated  until  fumes  of  sulphur  trioxide  are  evolved. 
The  residue  is  taken  up  with  a  little  water  and  warmed  until  the  sulphates  have 
dissolved.  If  decomposition  is  incomplete  and  a  colored  residue  remains,  this 
is  filtered  off,  ignited  in  a  platinum  dish  and  fused  with  a  little  potassium  bisul- 
phate.  The  fusion  is  dissolved  in  water  containing  a  little  nitric  acid  and  the 
solution  added  to  the  bulk  of  the  sample. 

If  manganese  is  to  be  determined  volumetrically  the  removal  of  iron  is  not 
necessary.  If,  however,  a  gravimetric  procedure  is  to  be  followed,  iron  and 
alumina  are  removed  by  the  basic  acetate  method  given  under  separations 
and  manganese  precipitated  in  the  filtrate.  In  presence  of  small  amounts  of 
iron  and  alumina,  precipitation  with  ammonia  in  presence  of  ammonium  chloride 
will  remove  these  elements  without  appreciable  loss  of  manganese,  a  double 
precipitation  being  usually  advisable.  For  volumetric  procedures  in  ores  con- 
taining over  2%  manganese  an  aliquot  portion  of  the  sample  is  taken  for  the 
determination.  The  portion  should  not  contain  over  0.01  gram  of  manganese. 

Sulphide  Ores — Pyrites,  etc.  The  sample  is  either  roasted  to  oxidize  the 
sulphide  and  then  dissolved  in  hydrochloric  acid  as  above  stated  or  it  is  treated 
according  to  the  procedure  given  for  iron  pyrites  under  sulphur. 

Slags.  These  may  be  decomposed  with  hydrofluoric  and  hydrochloric  acid 
with  final  expulsion  of  these  acids  with  sulphuric  acid.  Manganese  is  best  deter- 
mined in  the  extract  by  a  volumetric  method. 

Iron  Ores.  The  treatment  is  the  same  as  that  recommended  for  ores  of 
manganese.  The  residue  remaining  upon  evaporation  with  sulphuric  acid  is 
dissolved  in  a  little  water  and  about  30  cc.  of  nitric  acid  (sp.gr.  1.135)  added. 
Manganese  is  now  determined  by  the  bismuthate  method. 

Alloys.  Manganese  Alloys.  One  gram  of  ferromanganese  is  dissolved  in 
50  cc.  of  dilute  nitric  acid  (sp.gr.  1.135)  and  oxidized  with  sodium  bismuthate 
with  boiling.  The  cooled  solution  is  diluted  to  500  cc.  and  10  to  25  cc.  is  treated 
with  about  30  cc.  of  dilute  nitric  acid  and  manganese  determined  by  the  bis- 
muthate method.  The  amount  of  sample  taken  is  governed  by  the  manganese 
content.  This  should  not  exceed  0.01  gram  of  the  element  if  the  volumetric  pro- 
cedure is  to  be  followed. 

Manganese  Bronze.  Five  grams  of  drillings  are  dissolved  in  dilute  nitric 
acid  (1.2),  in  a  large  beaker,  using  only  sufficient  acid  to  cause  solution.  If  much 
free  acid  is  present  evaporation  to  small  volume  is  necessary  to  expel  the  nitric 
acid.  The  concentrate  is  diluted  to  200  cc.  and  hydrogen  sulphide  passed  in  to 
precipitate  copper.  The  solution  is  diluted  to  250  cc.  and  50  cc.  filtered  off 
( =  1  gram).  The  H2S  gas  is  expelled  by  boiling,  the  solution  being  concentrated 
about  15  cc.  Twenty-five  cc.  of  nitric  acid  are  added  and  manganese  precipitat 


MANGANESE  259 

by  adding  potassium  chlorate  in  small  portions.  The  chlorine  is  boiled  off  and  the 
precipitate  filtered  onto  asbestos  and  washed  with  concentrated  nitric  acid.  This 
is  now  determined  volumetrically  by  treating  with  an  excess  of  ferrous  sulphate 
of  known  strength  and  titrating  the  excess  with  standard  permanganate. 

Ferro-titanium  Alloy.  This  is  best  decomposed  by  fusion  with  sodium  carbon- 
ate, to  which  a  pinch  of  sodium  peroxide  has  been  added.  The  fusion  is  extracted 
with  water  and  the  residue  containing  iron,  manganese  and  nickel  filtered  onto 
asbestos.  Manganese  is  dissolved  in  25  to  30  cc.  of  nitric  acid  by  treating  with 
S02  gas  or  hydrogen  peroxide  and  manganese  determined  by  the  bismuthate 
method. 

Ferro-chromium,  Metallic  Chromium.  These  are  best  decomposed  by  fusion 
with  sodium  peroxide  (five  times  the  weight  of  sample  taken),  the  fusion  being 
made  in  a  nickel  crucible.  The  treatment  is  now  the  same  as  that  recom- 
mended for  ferro-titanium. 

Ferro-aluminum,  Vanadium  Alloys.  The  method  used  for  steel  is  suitable 
to  either  of  these  substances. 

Molybdenum  Alloys.  The  alloy  is  decomposed  with  hydrochloric  acid,  and 
iron  separated  by  the  basic  acetate  method,  a  large  excess  of  acetate  being  used. 
Manganese  is  precipitated  as  the  dioxide  by  means  of  bromine  and  ammonia  by 
the  detailed  procedure  given  later.  Manganese  is  dissolved  in  nitric  acid  after 
reduction  in  the  acid  solution  by  addition  of  a  little  sodium  thiosulphate  or  S02 
gas.  It  is  now  oxidized  to  permanganate  by  means  of  red  lead  and  determined 
either  colorimetrically  or  by  titration  with  a  standard  solution  of  sodium  arsenite. 

Tungsten  Alloys.  These  are  best  decomposed  by  treating  1  gram  of  the 
substance  with  5  to  10  cc.  of  hydrofluoric  acid  and  a  few  cc.  of  strong  nitric  acid 
and  digesting  until  the  solution  is  complete.  The  hydrofluoric  acid  is  expelled  1 
by  taking  to  dryness,  a  few  drops  of  sulphuric  acid  having  been  added.  The 
residue  is  taken  up  with  water  and  boiled  with  S02  water.  The  solution  is 
made  to  definite  volume  and  manganese  determined  volumetrically  on  an  aliquot 
portion. 

Silicon  Alloys.  One  gram  of  the  alloy  is  treated  with  50  cc.  of  dilute  nitric 
acid  (sp.gr.  1.2)  and  5  cc.  of  hydrofluoric  acid.  The  graphite  is  filtered  off  and 
the  hot  solution  treated  with  sodium  bismuthate  and  kept  boiling  for  about  fifteen 
minutes  after  the  manganese  dioxide  has  been  precipitated.  The  bismuthate 
method  for  estimating  manganese  is  recommended. 

Iron  and  Steel.  0.5  to  1  gram  of  steel  is  dissolved  by  heating  with  30  to 
50  cc.  of  dilute  nitric  acid  (1.135).  The  volumetric  method  by  oxidation  with 
sodium  bismuthate  is  generally  recommended,  no  separations  of  other  substances 
being  required,  as  manganese  may  be  determined  directly  in  the  sample. 

Pig  Iron.  One  gram  of  the  drillings  is  dissolved  in  30  cc.  of  dilute  nitric  acid 
(1.135  sp.gr.),  and  as  soon  as  the  action  has  ceased  the  sample  is  filtered  through  a 
7-cm.  filter  and  the  residue  washed  with  30  cc.  more  of  the  acid.  The  filtrate 
containing  the  manganese  is  now  treated  according  to  the  procedure  for  steel. 

1  Brearly  and  Ibbotson  state  that  although  neither  tungsten  nor  hydrofluoric  acid 
interfere  with  the  bismuthate  method  of  determining  manganese,  the  two  combined 
lead  to  erratic  results,  hence  the  removal  of  hydrofluoric  acid  is  necessary. 


260  MANGANESE 


SEPARATIONS 

This  section  includes  methods  of  special  separations  of  manganese  from 
elements  that  may  interfere  in  its  determination.  As  is  frequently  the  case, 
isolation  of  manganese  is  not  necessary,  since  it  may  be  determined  volumetri- 
cally  in  presence  of  a  number  of  elements,  which  would  interfere  in  its  gravimetric 
determination.  The  analyst  should  be  sufficiently  familiar  with  the  material 
to  avoid  needless  manipulations,  which  not  only  waste  time,  but  frequently  lead 
to  inaccurate  results. 

Removal  of  Elements  of  the  Hydrogen  Sulphide  Group.  This  sepa- 
ration may  be  required  in  the  analysis  of  certain  alloys  where  a  separation  of 
manganese  from  copper  is  required. 

The  acid  solution  containing  about  4%  of  free  hydrochloric  acid  (sp.gr.  1.2), 
is  saturated  with  hydrogen  sulphide  and  the  sulphides  filtered  off.  Manganese 
passes  into  the  filtrate.  This  treatment  will  effect  a  separation  of  manganese 
from  mercury,  lead,  bismuth,  cadmium,  copper,  arsenic,  antimony,  tin  and  the 
less  common  elements  of  the  group. 

Separation  of  Manganese  from  the  Alkaline  Earths  and  the  Alkalies. 
The  separation  is  occasionally  required  in  the  analysis  of  clays,  limestone, 
dolomite,  etc.  It  is  required  in  the  complete  analysis  of  ores.  In  the  usual 
course  of  a  complete  analysis  of  a  substance,  the  filtrate  from  the  hydrogen 
sulphide  group  is  boiled  free  of  H2S  and  is  treated  with  a  few  cc.  of  nitric  acid 
to  oxidize  the  iron.  The  solution  is  made  slightly  ammoniacal  with  ammonia, 
in  presence  of  ammonium  chloride,  whereby  iron,  aluminum  and  chromium  are 
precipitated  as  hydroxides.  The  filtrate  is  treated  with  hydrogen  sulphide  or 
colorless  ammonium  sulphide,  whereby  manganese,  nickel,  cobalt  and  zinc  are 
thrown  out  as  sulphides  and  the  alkaline  earths  and  alkalies  remain  in  solution. 

Separation  of  Manganese  from  Nickel  and  Cobalt 

The  free  acid  of  the  sulphate  or  chloride  solution  of  the  elements  is  neutralized 
with  sodium  carbonate  and  a  slight  excess  added.  It  is  now  made  strongly  acid 
with  acetic  acid  and  5  grams  of  ammonium  acetate  added  for  every  gram  of  nickel 
and  cobalt  present.  The  solution  is  now  diluted  to  about  200  cc.  and  saturated 
with  hydrogen  sulphide,  whereby  nickel  and  cobalt  are  precipitated  as  sulphides 
and  manganese  remains  in  solution. 


Separation  of  Manganese  from  Iron  and  Aluminum,  Basic 

Acetate  Method 

* 

The  procedure  effects  a  separation  of  iron,  aluminum,  titanium,  zirconium 
and  vanadium  from  manganese,  zinc,  cobalt  and  nickel. 

The  separation  depends  upon  the  fact  that  solutions  of  acetates  of  iron, 
aluminum,  titanium,  zirconium  and  vanadium  are  decomposed  when  heated 
and  the  insoluble  basic  acetates  precipitated,  whereas  the  acetates  of  manganese, 
zinc,  cobalt  and  nickel  remain  undecomposed  when  boiled  for  a  short  time. 

Fe(C2H802)8+2HOH=2HC2H302+Fe(OH)2.C2H302. 


MANGANESE  261 

The  solvent  action  of  the  liberated  acetic  acid  is  prevented  by  the  addition  of 
sodium  acetate  x  which  checks  ionization  of  the  acid.  The  method  requires  care 
and  is  somewhat  tedious,  but  the  results  attained  are  excellent. 

Procedure.  To  the  cooled  acid  solution  of  the  chlorides  is  added  a  concen- 
trated aqueous  solution  of  sodium  carbonate  from  a  burette  with  constant  stir- 
ring until  the  precipitate  that  forms  dissolves  slowly.  A  dilute  solution  of  the 
carbonate  is  now  added  until  a  slight  permanent  opalescence  is  obtained.  With 
the  weak  reagent  and  careful  addition  of  the  carbonate  drop  by  drop  the  proper 
neutralization  of  the  free  acid  is  obtained.  With  considerable  iron  present  the 
solution  appears  a  dark  red  color,  fading  to  colorless  as  the  quantity  of  iron 
decreases  to  a  mere  trace  in  the  solution.  Three  cc.  of  acetic  acid  (sp.gr.  1.044) 
are  added  to  dissolve  the  slight  precipitate.  The  more  perfect  the  neutralization 
before  heating  the  less  amount  of  reagent  required  for  precipitating  iron — an 
excess  of  reagent  does  no  harm.  If  this  does  not  clear  the  solution  in  two 
minutes,  more  acetic  acid  is  added  a  drop  at  a  time  until  the  solution  clears, 
allowing  a  minute  or  so  for  the  reaction  to  take  place  with  each  addition.  The 
solution  is  diluted  to  about  500  cc.  and  heated  to  boiling  and  6  cc.  of  a  30%  sodium 
acetate  solution  added.  The  solution  is  boiled  for  one  minute  and  removed 
from  the  flame.  (Longer  boiling  will  form  a  gelatinous  precipitate,  difficult  to 
wash  and  filter.)  The  precipitate  is  allowed  to  settle  for  a  minute  or  so,  then 
filtered,  while  the  liquid  is  hot,  through  a  rapid  filter  and  washed  with  hot,  5% 
sodium  acetate  solution  three  times.  The  apex  of  the  filter  is  punctured  with  a 
glass  stirring  rod  and  the  precipitate  washed  into  the  original  beaker  in  which 
the  precipitation  was  made  with  a  fine  stream  of  hot,  1  :  1  hydrochloric  acid 
solution  from  a  wash  bottle.  (Dilute  HN03  may  be  used  in  place  of  HC1.) 

A  second  precipitation  with  neutralization  of  the  acid  and  addition  of  sodium 
acetate  is  made  exactly  as  directed  above.  It  is  advisable  to  evaporate  the  solu- 
tion to  small  volume  to  expel  most  of  the  free  mineral  acid  before  addition  of 
Na2C03  to  avoid  large  quantities  of  this  reagent.  The  filtrates  contain  man- 
ganese, zinc,  cobalt  and  nickel;  the  precipitate  iron,  aluminum,  titanium,  zirco- 
nium, vanadium. 

Separation  of  Manganese  as  the  Dioxide,  MnO2 

The  procedure  is  of  special  value  in  the  complete  analysis  of  ores  where  a  basic 
acetate  separation  of  iron  and  aluminum  has  been  made,  and  a  gravimetric  esti- 
mation of  other  constituents  in  the  solution  are  desired. 

The  procedure  depends  upon  the  principle  that  manganese  in  a  dilute  solu- 
tion of  manganous  salt  is  oxidized  to  manganese  dioxide  and  so  precipitated, 
when  boiled  with  bromine  or  certain  other  oxidizing  agents : 

MnCl2+Br2+2H20  =  Mn02+2HCl+2HBr. 

The  free  acid  formed  by  the  reaction  must  be  neutralized  either  by  ammonia 
or  by  the  presence  of  a  salt  of  a  weak  acid  such  as  sodium  acetate,  otherwise 
the  precipitation  of  manganese  will  be  incomplete.  In  presence  of  ammonium 
salts  much  of  the  bromine  is  used  up  reacting  with  ammonia, 

MnCl2+Br2+3NH3+2H20  =  Mn02+2NH4Cl+NH4Br+HBr. 

1  Sodium  acetate  is  preferred  to  ammonium  acetate,  though  the  latter  may  be  used. 


262  MANGANESE 

At  the  same  time  an  acid  is  formed,  which  reacts  with  the  free  ammonia.  It 
is  necessary  to  have  the  solution  ammoniacal  throughout  the  reaction  to  pre- 
vent resolution  of  the  manganese. 

Procedure.  To  the  solution  containing  manganese  is  added  4  to  5  grams  of 
sodium  acetate  (unless  already  present  in  excess),  the  solution  being  diluted 
to  about  200  cc.  Bromine  water  is  added  until  a  distinct  color  of  bromine  is 
evident.  The  mixture  is  boiled  and  kept  boiling  for  ten  to  fifteen  minutes, 
additional  bromine  being  added  in  small  portions.  The  precipitate  is  allowed 
to  settle  and  filtered  off.  The  filtrate  is  boiled  with  additional  bromine  to 
ascertain  whether  the  manganese  has  been  completely  removed  from  the  solution. 

If  ammonia  is  present,  as  is  frequently  the  case,  it  is  advisable  to  add  more 
of  the  reagent  from  time  to  time,  the  solution  having  a  distinct  odor  of  ammonia 
after  the  last  portion  of  bromine  has  been  added.  When  large  amounts  of 
manganese  are  present,  several  separations  may  be  required  to  remove  the  element 
from  the  subsequent  filtrates. 

The  precipitated  dioxide  may  be  dissolved  in  sulphuric  acid  and  manganese 
determined  volumetrically  or  gravimetrically. 

It  may  be  ignited  directly  and  weighed  as  Mn304. 

It  may  be  evaporated  with  sulphuric  acid  and  manganese  determined  as 
MnS04. 

Manganates  of  zinc  or  calcium  will  be  precipitated  if  present  in  large  amounts. 

Manganese  may  also  be  precipitated  by  ammonium  persulphate  in  an  ammoniacal 
solution,  potassium  chlorate  and  chloride  of  lime  in  presence  of  zinc  chloride  in  a 
neutral  solution.1 


GRAVIMETRIC   METHOD 
Determination  of  Manganese  as  Pyrophosphate 

Manganese  is  precipitated  as  ammonium  manganese  phosphate,  NH4MnP04, 
and  then  ignited  to  pyrophosphate,  Mn2P207.  The  method  is  known  as  Gibbs' 
Phosphate  Process.2 

Procedure.  The  cold  solution  of  manganese  chloride  3  obtained  as  directed 
in  previous  sections,  should  be  diluted  so  as  to  contain  not  over  0.1  gram  of 
manganese  oxide  equivalent  per  100  cc.  of  solution.  A  cold  saturated  solution 
of  ammonium  sodium  phosphate  (microcosmic  salt,  170  grams  per  liter;  9  cc. 
precipitates  an  equivalent  of  0.1  gram  of  the  oxide)  is  now  added  in  slight  excess. 
The  solution  is  made  strongly  ammoniacal  and  heated  to  boiling,  the  boiling  being 
continued  until  the  precipitate  becomes  crystalline.  After  allowing  to  settle 
until  cold,  the  precipitate  is  filtered  off  (the  filtrate  being  tested  with  more  of  the 
precipitating  reagent  to  assure  that  an  excess  had  been  added),  and  dissolved 
in  a  little  dilute  hydrochloric  or  sulphuric  acid. 

Reprecipitation  of  the  phosphate.  The  free  acid  is  neutralized  with  ammonia 
added  in  slight  excess  until  the  odor  is  quite  distinct,  the  solution  heated  to 
boiling,  and  a  few  cc.  of  additional  phosphate  reagent  added.  The  crystalline 

1 J.  Pattinson's  Method,  Jour.  Chem.  Soc.,  35,  365,  1899. 
2Gibbs'C.N.,  17,  195,  1868. 

1  Some  analysts  prefer  to  add  the  phosphate  reagent  to  the  strongly  ammoniacal 
solution,  boiling  hot. 


MANGANESE  263 

precipitate  is  filtered  into  a  weighed  Gooch  crucible,  washed  free  of  chlorides 
with  very  dilute  ammonia  (AgN03+HN03  test),  dried  and  ignited  to  the  pyro- 
phosphate.  The  ignition  is  conducted,  as  in  case  of  magnesium,  by  heating  first 
over  a  low  flame  and  gradually  increasing  the  heat  to  the  full  power  of  the 
burner.  The  final  residue  will  appear  white  or  a  pale  pink. 

Mn2P207X0.4996=MnO, 
Mn2P207X  0.3869  =Mn. 

NOTES.  Zinc,  nickel,  copper  and  other  elements  precipitated  as  phosphates  should 
be  absent  from  the  solution.  The  separation  from  iron  is  generally  made  by  the  basic 
acetate  method  and  manganese  precipitated  from  the  filtrate,  free  of  other  elements, 
as  the  peroxide  MnO2,  by  means  of  bromine  added  to  the  ammoniacal  solution.  Other 
oxidizing  reagents  may  be  used,  as  has  been  stated.  The  dioxide  is  dissolved  in 
strong  hydrochloric  acid  and  the  above  precipitation  effected. 


VOLUMETRIC   METHODS 
Bismuthate  Method  for  Determination  of  Manganese  x 

The  method  is  based  on  the  fat  t  that  a  manganous  salt  in  the  presence  of  an 
excess  of  nitric  acid  is  oxidized  to  permanganic  acid  by  bismuth  tetroxide.  The 
permanganic  acid  formed  is  very  stable  in  nitric  acid  of  1.135  sp.gr.,  when  the  solu- 
tion is  cold,  but  in  hot  solutions  the  excess  of  the  bismuth  tetroxide  is  rapidly 
decomposed,  and  then  the  nitric  acid  reacts  with  the  permanganic  acid,  and,  as 
soon  as  a  small  amount  of  manganous  salt  is  formed,  the  remainder  of  the  per- 
manganic acid  is  decomposed,  manganous  nitrate  dissolves,  and  manganese 
dioxide  precipitates. 

In  the  cold,  however,  the  excess  of  the  bismuth  salt  may  be  filtered  off,  and 
to  the  clear  filtrate  an  excess  of  ferrous  sulphate  added,  and  the  amount  necessary 
to  deoxidize  the  permanganic  acid  determined  by  titrating  with  permanganate. 
The  end  reactions  are  very  sharp  and  the  method  is  extremely  accurate,  but  the 
presence  of  even  traces  of  hydrochloric  acid  utterly  vitiates  the  results.  As 
pointed  out  by  Reddrop  and  Ramage,  bismuth  tetroxide,  which  was  used  by 
Schneider,  is  difficult  to  obtain  free  from  chlorides,  and  they  recommended  sodium 
bismuthate,  which  they  prepare  as  follows :  Heat  20  parts  of  caustic  soda  nearly 
to  redness  in  an  iron  or  nickel  crucible,  and  add,  in  small  quantities  at  a  time, 
10  parts  of  basic  bismuth  nitrate,  previously  dried  in  a  water  oven.  Then 
add  2  parts  of  sodium  peroxide  and  pour  the  brownish-yellow  fused  mass  on  an 
iron  plate  to  cool;  when  cold,  break  it  up  in  a  mortar,  extract  with  water,  and 
collect  on  an  asbestos  filter.  The  residue,  after  being  washed  four  or  five  times 
by  decantation,  is  dried  in  the  water  oven,  then  broken  up  and  passed  through 
a  fine  sieve. 

Nitric  acid  (sp.gr.  1.135).  A  mixture  of  3  parts  of  water  and  1  part  of 
strong  nitric  acid. 

Nitric  acid  (3%).     Thirty  cc.  of  strong  acid  to  the  liter. 

Permanganate  Solution  and  Ferrous  Sulphate  Solution.  One  gram  of 
potassium  permanganate  to  the  liter  gives  a  solution  of  convenient  strength, 
and  12.4  grams  of  ferrous  ammonium  sulphate  and  50  cc.  of  strong  sulphuric  acid, 

1A.  A.  Blair,  "Chemical  Analysis  o'f  Iron,"  J.  B.  Lippincott  Co.,  Pub. 


264  MANGANESE 

made  up  to  1  liter,  gives  a  solution  which  is  almost  exactly  equal  to  the  per- 
manganate solution.  As  the  strength  of  the  ferrous  sulphate  solution  changes 
quite  rapidly  while  the  permanganate  remains  unaltered  for  months,  it  is 
unnecessary  and  troublesome  to  keep  them  of  the  same  strength.  By  using  a 
constant  volume  of  the  ferrous  sulphate  solution  and  testing  it  against  the  per- 
manganate solution  every  day,  the  calculation  of  the  results  is  very  simple. 
It  is  necessary  that  the  conditions  should  be  the  same  in  getting  the  strength 
of  the  ferrous  solution  as  in  titrating  a  solution  for  manganese,  and  after  many 
experiments  the  following  method  was  adopted:  Measure  into  a  200-cc.  flask 
50  cc.  of  nitric  acid  (1.135),  cool,  and  add  a  very  small  amount  of  bismuthate, 
dilute  with  50  cc.  of  3%  nitric  acid,  filter  into  a  300-cc.  flask,  and  wash  with  50  cc. 
of  3%  nitric  acid.  If  the  felt  is  well  coated  with  bismuthate  it  is  unnecessary  to 
add  any  to  the  nitric  acid  in  the  flask,  as  filtration  through  the  mass  of  bis- 
muthate on  the  felt  will  answer  the  purpose.  Run  in  from  the  pipette  (see  Fig. 
46)  25  cc.  of  ferrous  sulphate  solution  and  titrate  with  the  permanganate  to  a  faint 
pink.  This  gives  the  value  in  permanganate  of  the  ferrous  sulphate  solution. 

The  permanganate  solution  may  be  standardized  in  three  ways: 

First,  by  getting  its  value  in  iron,  in  the  usual  way,  and  calculating  its  value 
in  manganese.  The  proportion  is  5Fe  :  Mn  or  279.2  :  54.93  =0.1967. 

Second,  by  titrating  a  steel  containing  a  known  amount  of  manganese  and 
getting  the  value  of  the  solution  by  dividing  the  percentage  of  manganese  by  the 
number  of  cc.  of  the  permanganate  used. 

Third,  by  making  a  solution  of  pure  manganese  sulphate  and  determining 
the  manganese  in  it  by  evaporating  a  weighed  amount  of  the  solution  to  dry  ness, 
heating  to  dull  redness,  and  weighing  as  manganese  sulphate,  which,  multiplied 
by  0.36377,  gives  the  amount  of  manganese.  Five  grams  of  C.P.  manganese  sul- 
phate dissolved  in  500  cc.  of  water  and  filtered  will  give  a  solution  containing 
about  0.0035  gram  of  manganese  to  the  gram  of  solution.  Weigh  1  to  3  grams 
of  the  solution  in  a  crucible,  transfer  to  a  200-cc.  flask,  using  50  cc.  of  nitric  acid 
(sp.gr.  1.135),  cool,  and  add  0.5  to  1  gram  bismuthate,  and  allow  it  to  stand  for 
three  or  four  minutes,  shaking  at  intervals.  Add  50  cc.  of  3%  nitric  acid  and 
filter  through  the  asbestos  filter  and  wash  with  50  or  60  cc.  of  the  same  acid. 
Run  25  cc.  of  the  ferrous  sulphate  solution  into  the  flask  from  the  pipette  and 
titrate  with  the  permanganate  solution  to  a  faint  pink.  Subtract  the  number 
of  cc.  of  the  permanganate  solution  ob tamed  from  the  value  of  the  25  cc.  of  the 
ferrous  sulphate  solution  in  permanganate,  and  the  result  is  the  number  of  cc. 
of  the  permanganate  corresponding  to  the  manganese  in  the  manganese  sul- 
phate solution  used.  Divide  the  wreight  of  the  manganese  in  the  manganese 
sulphate  used  by  the  number  of  cc.  of  permanganate  and  the  result  is  the  value 
of  1  cc.  of  the  permanganate  solution  in  manganese. 

Example.  One  gram  manganese  sulphate  solution  contains  0.003562  gram 
manganese;  2.0372  grams  manganese  sulphate  solution  equal  0.0072565  gram 
manganese;  25  cc.  ferrous  sulphate  solution  equal  24.5  cc.  permanganate  solution; 
2.0372  grams  manganese  sulphate  solution,  after  oxidation  and  addition  of  25  cc. 
ferrous  sulphate  solution,  require  3.6  cc.  permanganate  solution;  24.5  cc.  —3.6  cc. 
=  20.9  cc.;  0.0072565  divided  by  20.9=0.0003472,  or  1  gram  permanganate 
equals  0.0003472  gram  manganese.  If,  then,  1  gram  of  steel,  after  oxidation 
and  addition  of  25  cc.  ferrous  sulphate  solution,  requires  6.2  cc.  permanganate 
solution  to  give  the  pink  color,  24.5-6.2=18.3X0.0003472=0.006354  gram, 
or  the  sample  contains  0.635%  manganese. 


MANGANESE 


265 


•10  C£. 


FIG.  45. 


FIG.  46. 


Procedure.  The  nitric  acid  solution  of  the  sample  placed  in  a  200-cc. 
Erlenmeyer  flask  is  treated  as  follows: 

Cool,  and  add  about  0.5  gram  of  bismuthate.  The  bismuthate  may  be 
measured  in  a  small  spoon,  and  experience  will  soon  enable  the  operator  to  judge 
of  the  amount  with  sufficient  accu- 
racy. Heat  for  a  few  minutes,  or 
until  the  pink  color  has  disappeared, 
with  or  without  the  precipitation  of 
manganese  dioxide.  Add  sulphurous 
acid,  solution  of  ferrous  sulphate,  or 
sodium  thiosulphate,  in  sufficient 
amount  to  clear  the  solution,  and 
heat  until  all  nitrous  oxide  has  been 
driven  off.  Cool  to  about  15°  C., 
add  an  excess  of  bismuthate,  and 
agitate  for  a  few  minutes.  Add  50  cc. 
of  water  containing  30  cc.  of  nitric 
acid  to  the  liter,  and  filter  through 
an  asbestos  felt  on  a  platinum  cone 
into  a  300-cc.  Erlenmeyer  flask,  using 
suction  (see  Fig.  45),  and  wash  with 
50  to  100  cc.  of  the  same  acid.  Run 
into  the  flask  from  a  pipette  (Fig.  46) 
a  measured  volume  of  ferrous  sulphate 

solution  and  titrate  to  a  faint  pink  color  with  permanganate.  The  number  of 
cc.  of  the  permanganate  solution  obtained,  subtracted  from  the  number  corre- 
sponding to  the  volume  of  ferrous  sulphate  used,  will  give  the  volume  of  per- 
manganate equivalent  to  the  manganese  in  the  sample,  which,  multiplied  by  the 
value  of  the  permanganate  in  manganese,  gives  the  amount  of  manganese  in  the 
sample. 

NOTE.  In  the  analysis  of  white  irons  it  may  be  necessary  to  treat  the  solution 
several  times  with  bismuthate  to  destroy  the  combined  carbon.  The  solution,  when 
cold,  should  be  nearly  colorless;  if  not,  another  treatment  with  bismuthate  is  necessary. 

Notes  and  Precautions 

Special  Steels..  Steels  containing  chronium  offer  no  special  difficulties,  except 
that  it  must  be  noted  that  while  in  hot  solutions  the  chromium  is  oxidized  to  chromic 
acid,  which  is  reduced  by  the  addition  of  sulphurous  acid,  the  oxidation  proceeds  so 
slowly  in  cold  solutions  that  if  there  is  no  delay  in  the  nitration  and  titration  the 
results  are  not  affected.  Steels  containing  tungsten  are  sometimes  troublesome  on 
account  of  the  necessity  for  getting  rid  of  the  tungstic  acid.  Those  that  decompose 
readily  in  nitric  acid  may  be  filtered  and  the  filtrate  treated  like  pig  iron,  but  when 
it  is  necessary  to  use  hydrochloric  acid  it  is  best  to  treat  with  aqua  regia,  evaporate 
to  dryness,  redissolve  in  hydrochloric  acid,  add  a  few  drops  of  nitric  acid,  dilute, 
boil,  and  filter.  Get  rid  of  every  trace  of  hydrochloric  acid  by  repeated  evaporations 
with  nitric  acid,  and  proceed  as  with  an  ordinary  steel. 

The  delicacy  of  the  reaction  of  manganese  in  nitric  acid  solution  with  sodium 
bismuthate  is  extraordinary;  0.000005  gram  of  manganese  gave  an  appreciable  color 
in  50  cc.  of  solution. 

As  will  be  seen  in  the  description  of  the  various  methods  of  solution,  the  use  of 
hydrochloric  acid  has  been  avoided,  because  the  presence  of  even  traces  of  this 
reagent  is  fatal  to  the  accuracy  of  the  method.  Where  it  is  impossible  to  avoid  its 
use,  and  its  presence  is  suspected  in  the  final  nitric  acid  solution,  the  addition  of  a 


266  MANGANESE 

drop  or  two  of  silver  nitrate  will  overcome  the  difficulty,  but  the  filter  must  be 
rejected  after  using  it  for  filtering  a  solution  so  treated. 

Any  form  of  asbestos  filtering  tube  may  be  used  for  filtering  off  bismuthate,  but 
the  perforated  cone  with  bell  jar  is  the  most  satisfactory,  because  it  has  the  largest 
area  of  filtering  service.  One  filter  may  be  used  for  fifty  or  more  determinations, 
and  the  time  occupied  in  filtering  and  washing  one  determination  is  only  from  one 
minute  and  a  half  to  three  minutes.  The  filtrate  must  be  clear,  for  the  least  par- 
ticle of  bismuthate  carried  through  will  vitiate  the  result  by  reacting  with  the  excess 
of  ferrous  sulphate.  As  soon  as  the  filtration  and  washing  are  completed,  the  ferrous 
sulphate  should  be  added,  and  the  excess  titrated  with  the  permanganate  solution, 
as  the  permanganic  acid  gradually  decomposes  on  standing,  and  the  warmer  the 
solution  the  more  rapid  is  the  decomposition.  At  a  temperature  of  5°  C.  the  solu- 
tion will  remain  unaltered  for  several  hours,  but  at  40°  C.,  fifteen  minutes  will  show 
an  appreciable  change.  The  larger  the  amount  of  manganese  the  more  rapid  the 
change. 

It  is  especially  important  not  to  allow  the  solution  to  stand  after  adding  the 
ferrous  sulphate,  as  the  excess  of  this  reagent  reacts  with  the  nitric  acid  in  a  few 
minutes  and  the  formation  of  the  smallest  amount  of  nitrous  oxide  is  fatal  to  the 
accuracy  of  the  determination.  For  this  reason  it  is  important  to  boil  off  every  trace 
of  nitrous  oxide  when,  in  the  earlier  part  of  the  operation,  sulphurous  acid  or  other 
deoxidizing  agent  is  added. 

When  working  with  steels  of  unknown  manganese  content,  it  may  often  happen 
that  25  cc.  of  ferrous  sulphate  solution  are  insufficient  to  entirely  reduce  the  perman- 
ganic acid,  in  which  case  an  additional  amount  of  ferrous  sulphate  must  be  added. 
It  will  be  noticed  that  the  solution  of  permanganic  acid  upon  the  addition  of  an 
insufficient  amount  of  ferrous  sulphate  does  not  necessarily  retain  its  pink  or  purple 
color,  but  usually  changes  to  a  dirty  brown.  When  this  occurs  10  cc.  more  of  ferrous 
sulphate  is  added  to  the  flask  and  the  value  of  the  two  additions  taken  as  the  amount 
from  which  the  number  of  cc.  of  permanganate,  corresponding  to  the  excess  of  fer- 
rous sulphate,  must  be  subtracted.  When  the  sample  is  low  in  manganese,  the  10  cc. 
ferrous  sulphate  alone  may  be  used. 

These  is  no  advantage  in  using  permanganate  solutions  differing  in  strength  from 
the  one  given  above,  but  the  strength  of  the  ferrous  sulphate  solution  may  be 
changed  to  meet  special  cases. 

Volhard's  Method  for  Manganese l 

The  method  is  based  on  the  principle  that  when  potassium  permanganate  is 
added  to  a  neutral  manganese  salt  all  of  the  manganese  is  oxidized  and  pre- 
cipitated. When  this  stage  is  reached  any  excess  of  permanganate  is  imme- 
diately evident  by  the  color  produced.  The  calculation  of  results  may  be  based 
on  the  reaction, 

3MnS04+2KMn04+2H20=5Mn02+K2S04+2H2S04, 
or 

5ZnS04+6MnS04+4KMn04+14H2O=4KHS04H-7H2S04+5ZnH2.2Mn03, 

the  ratio  in  either  case  being  2KMn04=3Mn. 

Procedure.  The  material  decomposed  with  hydrochloric  and  nitric  acid 
and  taken  to  fumes  with  sulphuric  acid,  as  stated  for  the  preparation  of  the 
sample,  is  cooled  and  boiled  with  25  cc.  of  water  until  the  anhydrous  ferric 
sulphate  has  dissolved  and  continue  as  follows:  Transfer  the  mixture  to  a  500-cc. 
graduated  flask  and  add  an  emulsion  of  zinc  oxide  in  slight  excess  to  precipitate 
the  iron  (C.P.  ZnS04  precipitated  by  KOH  added  to  slight  alkalinity.  The 
washed  precipitate  is  kept  in  a  stoppered  bottle  with  sufficient  water  to  form 
an  emulsion). 

1  A.  H.  Low,  "Technical  Methods  of  Ore  Analysis,"  7th  Ed.,  John  Wiley  &  Sons, 
Pub.  (See  procedure  for  Analysis  of  Spiegel  Iron.) 


MANGANESE  267 

Agitate  the  flask  to  facilitate  the  precipitation  and  see  that  a  slight  excess  of 
zinc  oxide  remains  when  the  reaction  is  complete.  Now  dilute  the  contents  of 
the  flask  up  to  the  mark  with  cold  water,  mix  thoroughly  and  allow  to  stand  a 
short  time  and  partially  settle.  By  means  of  a  graduated  pipette  draw  off 
100  cc.  of  the  clear  supernatant  liquid  and  transfer  it  to  an  8-oz.  flask.  While 
the  precipitate  in  the  500-cc.  flask  may  appear  large,  it  actually  occupies  but  a 
very  small  space,  and  any  error  caused  by  it  may  consequently  be  neglected. 
Likewise  the  error  in  measurement  due  to  change  of  temperature  during  the 
manipulation  is  insignificant.  Heat  the  solution  in  the  small  flask  to  boiling, 
add  two  or  three  drops  of  nitric  acid  (which  causes  the  subsequent  precipitate 
to  settle  more  quickly)  and  titrate  with  a  standard  solution  of  potassium  per- 
manganate. The  permanganate  causes  a  precipitate  which  clouds  the  liquid 
and  it  is  therefore  necessary  to  titrate  cautiously  and  agitate  the  flask  after 
each  addition,  and  then  allow  the  precipitate  to  settle  sufficiently  to  observe 
whether  or  not  the  solution  is  colored  pink.  A  little  experience  will  enable 
one  to  judge  by  the  volume  of  the  precipitate  formed,  about  how  rapidly  to 
run  in  the  permanganate.  The  final  pink  tinge,  indicating  the  end  of  the  reac- 
tion, is  best  observed  by  holding  the  flask  against  a  white  background  and 
observing  the  upper  edges  of  the  liquid.  When  this  point  is  attained,  bring  the 
contents  of  the  flask  nearly  to  a  boil  once  more  and  again  observe  if  the  pink 
tint  still  persists,  adding  more  permanganate  if  necessary.  In  making  this  end- 
test  avoid  actually  boiling  the  liquid,  as  a  continual  destruction  of  the  color  may 
sometimes  thus  be  effected  and  the  true  end-point  considerably  passed.  When 
the  color  thus  remains  permanent  the  operation  is  ended.  Observe  the  number 
of  cc.  of  permanganate  solution  used  and  calculate  the  result. 

It  is  customary  to  use  the  same  permanganate  solution  for  both  iron  and  man- 
ganese. Having  determined  the  factor  for  iron,  this  may  be  multiplied  by  0.2952 
to  obtain  the  factor  for  manganese.  It  will  be  observed  that  2KMnO4  are  required 
for  3Mn,  and  in  the  reaction  for  iron  that  2KMnO4  are  required  for  lOFe.  There- 
fore 558.4  parts  of  iron  are  equivalent  to  164.79  parts  of  manganese,  or,  1  part  of  iron 
to  0.2951  part  of  manganese. 

3MnS04  +2KMnO4  +2H2O  =  5MnO2  +K2SO4  +2H2SO4, 

=  5Fe2(SO4)3+2MnSO4+K2SO4+8H2O. 


Ammonium  Persulphate  Method  for  Determining  Small  Amounts 
of  Manganese  by  Colorimetric  Comparison  or  by  Titration 

The  process  depends  upon  the  oxidation  of  manganous  salts  to  perman- 
ganate by  ammonium  persulphate  in  presence  of  a  catalytic  agent  such  as  silver 
nitrate  : 

2Mn(N03)2-f-5(NH4)2S208+8H20=5(NH4)2S04+5H2S04+4HN03+2HMn04. 

The  reaction  takes  place  equally  well  in  sulphuric  or  in  nitric  acid  solution, 
or  in  a  mixture  of  the  two.  The  essential  point  is  the  presence  of  a  sufficient 
amount  of  silver  nitrate  catalyst. 

Procedure.  One  gram  of  ore  is  dissolved  in  hydrochloric  acid,  followed  by 
sulphuric  and  taken  to  fumes  as  directed  under  Preparation  and  Solution  of  the 
Sample.  The  sulphate  taken  up  with  water  is  made  to  a  volume  of  100  cc.  If 
the  color  comparison  is  to  be  made  the  solution  should  be  filtered  through  a 
dry  filter,  otherwise  the  filtration  may  be  omitted.  Twenty  cc.  (equal  to  0.2 


268  MANGANESE 

gram)  of  the  material  is  taken  for  the  test.  In  the  case  of  steel,  0.1  to  0.2  gram 
of  the  drilling,  dissolved  in  dilute  nitric  acid,  is  taken. 

Oxidation.  The  solution  is  transferred  to  a  test-tube,  IX 10  ins.,  if  the 
color  comparison  is  to  be  made,  or  into  a  150-cc.  Erlenmeyer  flask,  if  the  sample 
is  to  be  titrated.  Fifteen  cc.  of  silver  nitrate  solution  (1.5  grams  AgN03  per 
liter  of  water),  are  added;  the  solution  heated  to  80  to  90°  C.  by  placing  the 
receptacle  in  hot  water,  and  then  1  gram  of  ammonium  persulphate  added.  When 
the  color  commences  to  develop  the  sample  is  cooled  in  cold  water,  while  the 
evolution  of  oxygen  continues.  The  sample  is  poured  into  the  comparison  tube 
and  the  color  compared  with  that  obtained  from  an  ore  or  steel  sample  of  known 
manganese  content,  run  in  the  same  way. 

In  the  titration  method  the  solution  in  the  Erlenmeyer  flask  is  diluted  to 
about  100  cc.,  10  cc.  of  0.2%  salt  solution  added,  and  the  sample  titrated  with 
standard  sodium  arsenite  until  the  permanganate  color  is  destroyed.  The  cc. 
of  the  reagent  used  multiplied  by  the  factor  per  cc.  in  terms  of  manganese 
equals  weight  of  manganese  in  the  sample  titrated. 

NOTE.  Arsenious  acid  reagent  is  made  by  dissolving  10  grams  of  arsenious  oxide 
in  water  containing  30  grams  of  sodium  carbonate.  The  solution  is  diluted  to  1  liter. 
125  cc.  of  this  solution  are  diluted  to  2000  cc.  This  latter  reagent  is  standardized  against 
an  ore  or  sample  of  steel  of  known  manganese  content,  following  the  directions  given 
under  the  procedure  outlined. 

Oxidation  of  Manganese  to  Permanganate  by  Red  Lead 

Red  lead  oxidizes  manganese  in  nitric  acid  solution  to  permanganate.  The 
method  is  suitable  for  determining  this  element  in  steel  and  iron  in  presence 
of  molybdenum,  aluminum,  tungsten,  copper  and  nickel,  in  amounts  such  as 
are  apt  to  be  present.  The  method  is  given  in  the  chapter  on  Iron  in  the 
Analysis  of  Iron  and  Steel,  page  227. 

ANALYSIS  OF  SPIEGEL  IRON  FOR  MANGANESE1 

Procedure.  Weigh  0.5  gram  of  the  sample  in  a  250-cc.  beaker,  add  40  cc. 
dilute  HN03  (1-2),  cover  with  a  watch-crystal,  heat  over  Bunsen  burner  and 
finally  expel  nitrous  fumes  by  boiling  down  to  a  small  volume  (5  cc.).2  Wash 
into  a  500-cc.  graduated  flask,  fill  about  half  full,  neutralize  with  an  emulsion  of 
zinc  oxide,  adding  enough  to  precipitate  the  iron  and  a  slight  excess.3  Dilute  to 
the  mark,  shake  well,  pour  into  a  600-cc.  beaker  and  mix  by  pouring  back  into  the 
flask  and  then  into  beaker.  Allow  the  precipitate  to  settle,  decant  off  two  100-cc. 
portions  of  clear  solution  into  350-cc.  casseroles.  Add  100  cc.  water,  heat  to 
boiling  and  titrate  with  standard  KMnO4,  stirring  thoroughly  with  heavy  glass 
rod.  Run  in  about  1  cc.  at  a  time  until  the  end-point  is  passed.4  Titrate  the 
second  portion,  running  it  up  to  within  1  cc.  of  the  end-point,  and  finishing  a  drop 
or  two  at  a  time,  stirring  thoroughly  between  each  addition.6  The  burette 
reading  gives  percentage  of  Mn  directly. 

1  Procedure  communicated  to  the  author  by  Dr.  Breyer. 

2  It  is  necessary  to  boil  off  nitrous  fumes,  as  they  will  consume  KMnO4. 
8  Always  test  the  zinc  oxide  for  reducing  substances. 

4  In  samples  in  which  the  percentage  of  Mn  is  known  approximately,  almost 
the  full  amount  of  KMnO4  can  be  added  at  once. 

6  Do  not  mistake  the  reflection  of  precipitated  MnC>2  for  excess  of  KMn<Y 
If  properly  carried  out  the  MnO2  should  collect  in  center  of  casserole. 


MANGANESE  269 

Preparation  and  Standardization  of  Permanganate.1  Dissolve  23.23 
grams  C.P.  KMn04  in  12  liters  of  distilled  water,  shake  thoroughly  and  allow  to 
stand  a  week  or  two  before  using. 

Standardization.  Weigh  .15  gram  C.P.  sodium  oxalate  (Bureau  of  Standards) 
into  a  400-cc.  beaker.  Dissolve  in  200  to  250  cc.  hot  water  (80  to  90°),  add  10  cc. 
(1:1)  sulphuric  acid.  Titrate  at  once  with  KMn04,  until  1  drop  gives  a  per- 
manent pink. 

When  .15  gram  sodium  oxalate  is  taken,  it  should  consume  36.87  cc.  KMn04, 
if  the  permanganate  is  of  correct  strength,  i.e.,  1  cc.  =1%  in  .1  gram  sample 
titrated. 

JThe  Standardization  of  KMnO4  solution  by  Sodium  Oxalate,  McBride,  J.A.C.S., 
34,  393.  Miller,  "  Quantitative  Analysis  for  Mining  Engineers." 


MERCURY 

WILFRED  W.  SCOTT 

Hg,  at.wt.  200.6;  sp.gr.  13.595;  l  m.p.  —  38.9° ;2  6.p.  357.33°  C; l  oxides, 

Hg20,  HgO. 

DETECTION 

Metallic  mercury  is  recognized  by  its  physical  properties.  It  is  the  only 
metal  which  is  a  liquid  at  ordinary  temperatures.  The  element  forms  a  convex 
surface  when  placed  on  glass. 

Mercury  in  the  mercurous  form  is  precipitated  by  hydrochloric  acid  as  white 
mercurous  chloride,  HgCl.  This  compound  is  changed  by  ammonium  hydroxide 
to  the  black  precipitate  of  metallic  mercury  and  nitrogen  dihydrogen  mercuric 
chloride.3 

Mercury  in  the  mercuric  form  is  not  precipitated  by  hydrochloric  acid.  The 
sulphide  of  the  element  is  thrown  out  from  an  acid  solution  as  black  HgS. 
The  precipitate  first  appears  white,  changing  to  orange-yellow,  then  brown 
and  finally  to  black,  as  the  H2S  gas  is  passed  into  the  solution.  The  element 
is  distinguished  from  the  other  members  of  the  group  by  the  insolubility  of 
its  sulphide  in  yellow  ammonium  sulphide  and  in  dilute  nitric  acid. 

If  the  mercury  sulphide  is  dissolved  in  aqua  regia,  the  nitric  acid  expelled 
by  taking  to  dryness,  then  adding  hydrochloric  acid  and  evaporating  again  to 
dryness,  the  residue  taken  up  with  a  little  hydrochloric  acid,  diluted  with  water, 
and  treated  with  a  solution  of  stannous  chloride,  a  white  precipitate  of  mer- 
curous chloride  is  first  formed,  which  is  further  reduced  to  metallic  mercury  by 
an  excess  of  the  reagent. 

ESTIMATION 

The  metal  is  found  free  in  the  upper  portions  of  cinnabar  deposits.  As 
an  amalgam  with  silver  it  occurs  in  horn  silver.  Cinnabar,  HgS,  is  the  only  ore 
of  mercury  of  commercial  importance.  The  element  has  been  found  in  quartz, 
sandstone,  schists,  iron  pyrites,  bituminous  substances,  eruptive  and  sedimentary 
rocks  of  all  ages.  It  occurs  in  sulphide  ores  of  other  metals — especially  in  zinc 
ores. 

Preparation  and  Solution  of  the  Sample 

It  will  be  recalled  that  nitric  acid  is  the  best  solvent  for  the  metal  and  its 
amalgams.  The  oxides  are  insoluble  in  alkalies.  Mercuric  oxide  is  dissolved 
by  acids.  Hydrochloric  acid  forms  mercurous  chloride  with  the  lower  oxide, 
insoluble  in  dilute  hydrochloric  acid. 

1Van  Nostrand's  Chem.  Annual — Olsen. 
2 Circular  35  (2d  Ed.)  U.  S.  Bureau  of  Standards. 
*  Prescott  and  Johnson,  "Qualitative  Chemical  Analysis." 
270 


MERCURY  271 

Ores.  If  mercury  is  to  be  determined  by  the  dry  procedure,  the  finely 
ground  sample  may  be  mixed  directly  with  the  flux  and  determined  as  directed 
later. 

For  the  wet  methods  the  ore  is  decomposed  in  a  covered  porcelain  dish  with 
aqua  regia,  heating  gently.  The  solution  is  evaporated  to  dryness  on  the  water 
bath.  The  residue  is  taken  up  with  hydrochloric  acid  and  again  evaporated  to 
dryness  to  expel  the  nitric  acid.  The  residue  is  again  dissolved  by  adding  a  little 
hydrochloric  acid.  Mercury  will  now  be  in  solution  and  may  be  determined  by 
precipitation  as  mercuric  sulphide  by  the  gravimetric  procedure. 

For  opening  up  the  ore  for  the  volumetric  method  by  Seamon  see  method 
at  close  of  the  chapter,  page  274. 

SEPARATIONS 

Separation  of  Mercury  from  the  Iron  and  Zinc  Groups,  or  from  the 
Alkaline  Earths  and  the  Alkalies.  Mercury  is  precipitated  as  a  sulphide 
from  an  acid  solution  of  the  mercuric  salt  by  hydrogen  sulphide,  together  with  the 
members  of  the  hydrogen  sulphide  group.  Sufficient  acid  should  be  present 
to  prevent  the  precipitation  of  zinc  sulphide.  Iron,  aluminum,  chromium, 
manganese,  cobalt,  nickel,  zinc,  the  alkaline  earths  and  the  alkalies  remain  in 
solution. 

Separation  of  Mercury  from  Arsenic,  Antimony,  and  Tin.  The  sul- 
phides obtained  by  passing  hydrogen  sulphide  into  an  acid  solution,  preferably 
of  the  chlorides,  are  digested  with  yellow  ammonium  sulphide  solution.  Arsenic, 
antimony  and  tin  dissolve,  whereas  mercury  sulphide  remains  insoluble.  Sul- 
phides of  the  fixed  alkalies  dissolve  mercury  as  well  as  arsenic,  antimony  and  tin, 
so  cannot  be  used  in  effecting  a  separation. 

Separation  from  Lead,  Bismuth,  Copper  and  Cadmium.  These  elements 
remain  with  mercury  upon  removal  of  arsenic,  antimony  and  tin  as  their  sul- 
phides are  insoluble  in  ammonium  sulphide.  (CuS  slightly  soluble.)  The  pre- 
cipitated sulphides  are  transferred  to  a  porcelain  dish  and  boiled  with  dilute 
nitric  acid,  sp.gr.  1.2  to  1.3.  After  diluting  slightly  with  water  the  solution  is- 
filtered  and  the  residue  of  mercuric  sulphide  washed  with  dilute  nitric  acid  and 
finally  with  water.  If  much  lead  is  present  in  the  solution  it  is  apt  to  contami- 
nate the  residue  by  a  portion  being  oxidized  to  lead  sulphate  and  remaining  insol- 
uble. In  this  case  the  residue  is  treated  with  aqua  regia,  the  solution  diluted  and 
mercury  chloride  filtered  from  PbS04  and  free  sulphur.  Mercury  is  best  deter- 
mined as  HgS  by  the  ammonium  sulphide  method  described  later.  Traces  of 
lead  do  not  interfere,  as  lead  is  completely  removed  by  remaining  insoluble  in 
potassium  hydroxide,  whereas  mercury  sulphide  dissolves.  See  method. 

Separation  from  Selenium  and  Tellurium.  The  mercury  selenide  or  telluride 
is  dissolved  in  aqua  regia,  chlorine  water  added  and  the  solution  diluted  to 
600  to  800  cc.,  phosphorous  acid  is  added  and  the  solution  allowed  to  stand  for 
some  time;  mercurous  chloride  is  precipitated,  selenium  and  tellurium  remain- 
ing in  solution.  Selenium  and  tellurium  will  precipitate  in  hot  concentrated 
solutions  when  treated  with  phosphorous  acid,  but  not  in  dilute  hydrochloric 
acid  solutions. 

Mercury  in  Organic  Substances.  The  material  is  decomposed  by  heating 
in  a  closed  tube  with  concentrated  nitric  acid.  Mercury  is  now  precipitated  as 
,a  sulphide  with  ammonium  sulphide  as  directed  in  the  procedure  given  later. 


272 


MERCURY 


GRAVIMETRIC   METHODS 

Determination  of  Mercury  by  Precipitation  with  Ammo- 
nium Sulphide1 

The  following  method,  suggested  by  Volhard,  is  generally  applicable  for 
determination  of  mercury.  The  element  is  precipitated  by  ammonium  sul- 
phide as  HgS.  The  precipitate  dissolved  in  caustic  is  again  thrown  out  by  addi- 
tion of  ammonium  nitrate  to  the  sulpho  salt  solution  of  mercury. 

Hg(SNa),+2NH4NO,=2NaNO,+(NHO.S+Hg& 

Procedure.  The  acid  solution  of  the  mercuric  salt  is  nearly  neutralized  by 
sodium  carbonate,  and  is  then  heated  with  a  slight  excess  of  ammonium  sulphide 

reagent,  freshly  prepared.  Sodium  hydroxide  solu- 
tion is  added  until  the  dark-colored  liquid  begins  to 
lighten.  The  solution  is  now  heated  to  boiling  and 
more  sodium  hydroxide  added  until  the  liquid  is 
clear.  If  lead  is  present  it  will  remain  undissolved 
and  should  be  filtered  off.  Ammonium  nitrate  is 
now  added  to  the  solution  in  excess  and  the  mix- 
ture boiled  until  the  greater  part  of  the  ammonia 
has  been  expelled.  The  clear  liquid  is  decanted 
from  the  precipitate  through  a  weighed  Gooch 
crucible  and  the  precipitate  washed  by  decantation 
with  hot  water  and  finally  transferred  to  the  cruci- 
ble and  washed  two  or  three  times  more.  The 
mercuric  sulphide  is  dried  at  110°  C.  and  weighed  as 
HgS. 

HgSX0.8622=Hg    or     X0.9307=HgO. 

FIG.  47.  NOTES.     Alumina  and  silica  are  apt  to  be  present  in 

caustic. 

Free  sulphur  may  be  removed,  if  present,  by  boiling  with  sodium  sulphite, 
Na2SO3+S  =  Na2S2O3.  The  sulphur  may  be  extracted  with  carbon  disulphide. 
The  Gooch  crucible  is  placed  upon  a  glass  tripod  in  a  beaker,  containing  carbon  di- 
sulphide, and  a  round-bottomed  flask  filled  with  cold  water  is  placed  over  the  mouth 
of  the  beaker  to  serve  as  a  condenser,  Fig.  47.  By  gently  heating  over  a  water  bath 
for  an  hour  the  sulphur  is  completely  extracted  from  the  sulphide.  Carbon  disul- 
phide is  removed  from  the  precipitate  by  washing  once  with  alcohol  followed  by 
ether.  The  residue  is  now  dried  and  weighed. 

Determination  of  Mercury  by  Electrolysis 

Mercury  is  readily  deposited  as  a  metal  from  slightly  acid  solutions  of  its  salts. 

Procedure.  The  neutral  or  slightly  acid  solution  of  mercuric  or  mercurous 
salt  is  diluted  in  a  beaker  to  150  cc.  with  water  and  2  to  3  cc.  of  nitric  acid  added. 
The  solution  is  electrolyzed  with  a  current  of  0.5  to  0.1  ampere,  and  an  E.M.F. 
of  3.5  to  5  volts.  A  gauze  cathode  is  recommended,  or  a  platinum  dish  with 
dulled  inner  surface  may  be  used.  One  gram  of  mercury  may  be  deposited  in 
about  fifteen  hours  (or  overnight).  The  time  may  be  shortened  to  about  three 
hours  by  increasing  the  current  to  0.6  to  1  ampere. 

1  Treadwell  and  Hall,  "Analytical  Chemistry,"  Vol.  2,  4th  Ed,    J,  Wiley  &  Sons. 


MERCURY 


273 


The  metal  is  washed  with  water  without  interrupting  the  current  and  then 
with  alcohol.  After  removing  the  adhering  alcohol  with  a  filter  paper,  the 
cathode  is  placed  in  a  desiccator  containing  fused  potash  and  a  small  dish  of 
mercury.  The  object  of  this  mercury  is  to  prevent  loss  of  the  deposit  by 
vaporization. 

The  increased  weight  of  the  cathode  is  due  to  metallic  mercury. 

NOTES.  In  the  electrolysis  of  mercuric  chloride  turbidity  may  be  caused  by 
formation  of  mercurous  chloride  by  reduction,  but  this  does  no  harm,  as  the  reduction 
to  metallic  mercury  follows. 

Mercury  may  be  electrolyzed  from  its  sulpho  solutions,  obtained  by  dissolving 
its  sulphide  in  concentrated  sodium  sulphide. 

Determination  of  Mercury  by  the  Holloway=Eschka  Process 

Modified 

When  mercury  sulphide  is  heated  with  iron  filings  metallic  mercury  is  vol- 
atilized, iron  sulphide  being  formed.  The  mercury  vapor  is  condensed  on  a 
silver  or  gold  plate.  The  use  of  iron  for  this  reduction  was  suggested  by  Eschka 
and  his  method  modified  by  Holloway.  In  ores  containing  arsenic  the  addition 
of  zinc  oxide  is  recommended.  Erdmann  and  Marchand  use  lime  for  decomposing 
the  mercury  compound.  The  reactions  may  be  represented  as  follows: 

HgS+Fe=FeS+Hg   or   HgX+CaO=CaX+Hg+0. 

Apparatus.  This  consists  of  a  deep  glazed  porcelain  crucible,  the  size 
depending  upon  the  charge  of  the  sample  to  be  taken.  Generally  a  30-cc.  cru- 
cible is  used  for  a  2-gram  sample  with  4  grams  of  flux.  The  crucible  is  covered 
by  a  silver  or  gold  plate  that  lies 
perfectly  flat  and  fits  snugly 
around  the  edges  of  the  crucible. 
It  may  be  necessary  to  grind  the 
top  of  the  receptacle  on  emery 
paper  to  obtain  a  perfectly  level 


The  crucible  is  suspended  in  a 
hole  through  an  asbestos  board  or 
quartz  plate,  to  prevent  the  flame 
heating  the  upper  portion  of  the 
vessel. 


— 

1     f 

Condenser 
Co/d  Hater' 

•                                    — 

-Silver  Cover 

^1 

Asbestos  Board 

\fe-P'::;^-  ;;::'.fev: 

^nn^ 

'•^J Crucible  mth. 
Sample 


FIG.  48. 


The  lid  of  the  crucible  is  kept  cool  by  a  cylindrical  condenser  of  metal  through 
which  a  stream  of  water  passes.  A  small  Erlenmeyer  flask  may  be  used,  with 
a  tube  passing  to  the  bottom  of  the  flask  through  ar  rubber  stopper,  and  a 
second  tube  just  passing  through  the  stopper. 

Holloway  has  a  weight  placed  on  the  metal  condenser  to  hold  the  lid  firmly 
against  the  crucible.  The  illustration  (Fig.  48)  shows  the  form  of  the  apparatus 
set  up  for  the  run. 

Procedure.  The  sample  containing  not  over  0.1  gram  of  mercury  is  placed 
in  the  crucible  with  5  to  10  grams  of  fine  iron  filings  and  intimately  mixed.  Addi- 
tional filings  are  put  over  the  charge.  Sulphide  ores  containing  arsenic  are 
best  mixed  with  about  twice  the  weight  of  a  flux  of  zinc  oxide  and  sodium  car- 
bonate in  the  proportion  4  to  1,  and  about  five  times  the  weight  of  iron  filings 


added. 


\ 


274  MERCURY 

The  weighed  silver  cover  is  placed  on  the  crucible  and  the  apparatus  set  up  as 
shown  in  the  illustration,  Fig.  48. 

The  bottom  of  the  crucible  is  gradually  heated  with  a  small  Me"ker  flame 
until  it  glows  slightly.  Overheating  should  be  avoided.  The  upper  portion  of 
the  crucible  should  never  become  hot  and  the  lid  should  remain  cold.  After 
heating  for  about  thirty  minutes  the  system  is  allowed  to  cool  without  discon- 
necting the  condenser.  The  disk  is  now  removed,  dipped  in  alcohol  and  dried 
in  a  desiccator  over  fused  potash  or  soda.  The  increase  of  weight  of  the  dried 
disk  is  due  to  metallic  mercury. 

NOTES.  If  the  sample  contains  less  than  1%  mercury,  take  2  grams;  if  1  to  2% 
mercury,  take  1  gram ;  if  the  sample  contains  2  to  5%,  take  0. 5-gram  sample.  If  high  in 
mercury,  grind  sample  with  sand  and  take  an  aliquot  portion. 

It  is  advisable  to  repeat  the  test  with  a  clean  foil  to  be  sure  that  all  the  mer- 
cury has  been  driven  out  of  the  sample.  The  foil  may  be  freed  from  mercury  by 
heating. 

VOLUMETRIC  DETERMINATION   OF   MERCURY 
Seamen's  Volumetric  Method  1 

Seamen's  Volumetric  Method.2  Weigh  0.5  gram  of  the  finely  ground  ore 
into  an  Erlenmeyer  flask  of  125  cc.  capacity.  Add  5  cc.  of  strong  hydrochloric 
acid  and  allow  it  to  act  for  about  ten  minutes  at  a  temperature  of  about  40 °C., 
then  add  3  cc.  of  strong  nitric  acid  and  allow  the  action  to  continue  for  about 
ten  minutes  longer.  The  mercury  should  now  all  be  in  solution.  Now  if  lead  be 
present,  add  5  cc.  of  strong  sulphuric  acid;  it  may  be  omitted  otherwise.  Dilute 
with  15  cc.  of  water  and  then  add  ammonia  cautiously  until  the  liquid  is  slightly 
alkaline.  Bismuth,  if  present,  will  be  precipitated.  Acidify  faintly  with  nitric 
acid,  filter,  receiving  the  filtrate  in  a  beaker,  and  wash  thoroughly. 

Add  to  the  filtrate  1  cc.  of  strong  nitric  acid  that  has  been  made  brownish 
in  color  by  exposure  to  the  light,  and  titrate  with  a  standard  solution  of  potassium 
iodide  until  a  drop  of  the  liquid  brought  into  contact  with  a  drop  of  starch 
liquor,  on  a  spot-plate,  shows  a  faint  bluish  tinge.  It  is  a  good  plan  to  set  aside 
about  one-third  of  the  mercury  solution  and  add  it  in  portions  until  the  end- 
point  is  successively  passed,  finally  rinsing  in  the  last  portion  and  titrating  to 
the  end-point  very  carefully. 

Deduct  0.5  cc.  from  the  burette  reading  and  multiply  the  remaining  cc.  used 
by  the  percentage  value  of  1  cc.  in  mercury  to  obtain  the  percentage  in  ^he  ore. 

The  standard  potassium  iodide  solution  should  contain  8.3  grams  of  the 
salt  per  liter.  Standardize  against  pure  mercuric  chloride.  Dissolve  a  weighed 
amount  of  the  salt  in  water,  add  2  cc.  of  the  discolored  nitric  acid  and  titrate 
as  above.  One  cc.  of  standard  solution  will  be  found  equivalent  to  about  0.005 
gram  of  mercury,  or  about  1%  on  the  basis  of  0.5  gram  of  ore  taken  for  assay. 

The  precipitate  of  red  mercuric  iodide  which  forms  during  the  titration  may 
not  appear  if  the  amount  of  mercury  present  is  very  small,  but  this  failure  to 
precipitate  does  not  appear  to  affect  the  result. 

Iron,  copper,  bismuth,  antimony,  and  arsenic,  when  added  separately  to 
the  ore,  did  not  influence  the  results  in  Seamen's  tests.  Silver  interferes.  Dupli- 
cate results  should  check  within  0.1  to  0.2  of  1%. 

1  A.  H.  Low,  "Technical  Methods  of  Ore  Analysis." 
a  "  Manual  for  Assayers  and  Chemists,"  p.  112. 


MOLYBDENUM 

WILFRED  W.  SCOTT 
Mo,a*.urt.96.0;  sp.gr.  8.6  -9.01;  m.p.2500°C;  oxides,  Mo2O3,  MoO2,  MoOc 

DETECTION 

Molybdenum  appears  in  the  hydrogen  sulphide  group,  being  precipitated  by 
H2S  in  acid  solution  as  the  sulphide.  It  passes  into  solution  by  digestion  with 
ammonium  sulphide  or  sodium  sulphide  along  with  arsenic,  antimony,  tin,  gold 
and  platinum.  By  addition  of  metallic  zinc,  antimony,  together  with  tin,  gold 
and  platinum  are  precipitated  as  metals  while  molybdenum  remains  in  solution. 
Arsenic,  that  has  not  volatilized  as  arsine,  is  expelled  by  evaporation.  Nitric 
acid  is  now  added  and  the  solution  taken  to  dryness.  Molybdenum  is  extracted 
from  the  residue  with  ammonium  hydroxide. 

A  dilate  solution  of  ammonium  molybdate  treated  with  a  soluble  sulphide 
gives  a  blue  solution. 

Sodium  thiosulphate  added  to  a  slightly  acid  solution  of  ammonium  molyb- 
date produces  a  blue  precipitate  with  a  supernatant  blue  solution.  With  more 
acid  a  brown  precipitate  is  formed. 

Sulphur  dioxide  produces  a  bluish-green  precipitate  if  sufficient  molybdenum 
is  present,  or  a  colored  solution  with  small  amounts.  The  reducing  agents,  stan- 
nous  chloride,  or  zinc  in  acid  solution,  produce  a  play  of  colors  when  they  react 
with  molybdenum  solutions,  due  to  the  formation  of  the  lower  oxides.  The  solu- 
tion becomes  blue,  changing  to  green,  brown  and  yellow. 

Molybdenum  present  as  molybdate  is  precipitated  by  disodium  phcsphate 
as  yellow  ammonium  phosphomolybdate  from  a  nitric  acid  solution.  The  pre- 
cipitate is  soluble  in  ammonium  hydroxide. 

A  pinch  of  powdered  mineral  on  a  porcelain  lid,  moistened  with  a  few  drops 
of  strong  sulphuric  acid,  stirred  and  heated  to  fumes,  then  cooled,  will  produce 
a  blue  color  when  breathed  upon.  The  color  disappears  on  heating,  but  reappears 
on  cooling.  Water  destroys  the  color. 

Molybdenite  is  very  similar  to  graphite  in  appearance.  It  is  distinguished 
from  it  by  the  fact  that  nitric  acid  reacts  with  molybdenite,  MoS2,  leaving  a 
white  residue,  but  has  no  action  upon  graphite.  The  blowpipe  gives  S02  with 
molybdenite  and  C02  with  graphite. 

ESTIMATION 

The  determination  is  required  in  the  ores — molybdenite,  MoS2,  (60%  Mo); 
molybdite,  Mo03  (straw  yellow);  wulfenite,  PbMo04  (yellow,  bright  red,  olive 
green  or  colorless);  Ilsemannite,  Mo03+Mo02;  powellite,  CaMo04;  pateraite, 
CoMo04;  belonesite,  MgMo04;  eosite,  lead-vanado-molybdate;  achromatite, 

275 


276  MOLYBDENUM 

lead  molybdate  and  arsenate  with  tin  oxide  and  lead  chloride.  Some  iron  and 
copper  ores  also  contain  molybdenum. 

The  metal  is  determined  in  certain  self -hardening  steels  and  alloys. 

The  reagents  ammonium  molybdate  and  the  oxide-molybdic  acid,  Mo03, 
are  valuable  for  analytical  purposes.  Tests  of  their  purity  may  be  required. 

Preparation  and  Solution  of  the  Sample 

In  dissolving  the  substance  the  following  facts  should  be  kept  in  mind: 
The  metal  is  easily  soluble  in  aqua  regia;  soluble  in  hot  concentrated  sulphuric 
acid,  soluble  in  dilute  nitric  acid,  oxidized  by  excess  to  Mo03.  It  is  dissolved 
by  fusion  with  sodium  carbonate  and  potassium  nitrate  mixture.  It  is  insol- 
uble in  hydrochloric,  hydrofluoric  and  dilute  sulphuric  acids. 

The  oxide  Mo03  is  but  slightly  soluble  in  acids  and  alkalies;  Mo02  is  insol- 
uble in  hydrochloric  and  hydrofluoric  acids.  Mo03,  as  ordinarily  precipitated, 
is  soluble  in  inorganic  acids  and  in  alkalies.  The  oxide  sublimed  is  difficultly 
soluble. 

Molybdates  of  the  heavy  metals  are  insoluble  in  water,  the  alkali  molybdates 
are  soluble. 

Ores.  Molybdenum  ores  are  best  decomposed  by  fusion  with  a  mixture  of 
sodium  carbonate  and  potassium  nitrate.  The  cooled  fusion  is  then  extracted 
with  hydrochloric  acid  and  molybdenum  determined  according  to  one  of  the 
procedures  described  later. 

Steel  and  Iron.  One  to  2  grams  of  the  drillings  are  dissolved  in  a  mixture 
of  hydrochloric  and  nitric  acid  (25  cc.  HCl-fl  cc.  HN03),  with  gentle  heating. 
Additional  nitric  acid  is  added  if  required  or  potassium  chlorate  may  be  used 
to  oxidize  the  iron. 

SEPARATION   OF  MOLYBDENUM   FROM  OTHER  ELEMENTS 

Separation  from  Iron.  Procedure  in  Presence  of  Large  Amounts  of 
Iron.  The  occurrence  of  molybdenum  with  iron  and  its  commercial  importance 
in  iron  materials  calls  for  this  procedure  as  one  commonly  required  in  the  deter- 
mination of  molybdenum. 

The  solution  is  nearly  neutralized  with  a  2N.  NaOH  solution,  added  from  a 
burette  cautiously,  avoiding  an  amount  that  would  produce  a  color  with  iron  or 
form  a  basic  molybdate.  If  tungsten  is  present  or  if  molybdic  acid  has  precip- 
itated in  the  solution  or  is  suspected,  the  sample  should  be  filtered  and  the 
residue  treated  as  directed  below.  Sufficient  2N.  NaOH  to  precipitate  all  the 
iron  present  in  the  sample  (27  cc.  of  2N.  NaOH  will  precipitate  1  gram  Fe)  with 
about  40  cc.  in  excess  is  poured  into  a  500-cc.  flask.  If  filtration  is  necessary, 
the  paper  and  residue  are  dropped  in  the  flask,  the  filter  broken  up,  and  the 
caustic  heated  to  boiling  to  dissolve  the  molybdic  acid.  The  solution  contain- 
ing the  molybdenum  is  also  heated  to  boiling  and  added  to  the  hot  NaOH  solu- 
tion, through  a  funnel  with  a  constricted  stem,  agitating  the  sodium  hydroxide 
during  the  addition.  Iron  hydroxide,  Fe(OH)3,  is  precipitated  free  from  molyb- 
denum, which  remains  in  solution.  The  volume  is  made  up  to  exactly  500  cc. 
and  the  precipitate  allowed  to  settle;  250  cc.  are  filtered  off  and  taken  for  the 
presHtation  of  molybdenum.  Methyl  orange  is  added  as  an  indicator  and 
the  caustic  neutralized  with  HC1.  If  barium,  strontium,  uranium,  arsenic,  cad- 
miiui  and  aluminum  are  present,  10  to  15  cc.  strong  hydrochloric  acid  are  added 


MOLYBDENUM  277 

in  excess,  followed  by  sufficient  ammonium  acetate  to  combine  with  the  free 
mineral  acid. 

This  method,  followed  by  the  lead  molybdate  precipitation  as  given  in  the 
gravimetric  methods,  will  effect  a  separation  of  molybdenum  from  barium, 
calcium,  strontium,  arsenic,  cadmium,  phosphorus,  aluminum,  uranium,  man- 
ganese, cobalt,  nickel,  zinc,  chromium,  magnesium,  mercury,  copper  as  well  as  iron. 

Separation  from  the  Alkalies.  Molybdenum,  precipitated  as  mercurous 
molybdate,  by  adding  mercurous  nitrate  to  the  slightly  acetic  acid  solution,  or  as 
molybdenum  sulphide  by  H2S  passed  into  the  sulphuric  acid  solution,  is  separated 
from  the  alkalies. 

If  hydrogen  sulphide  is  passed  into  the  sulphuric  acid  solution,  separation  of 
molybdenum  from  the  members  of  the  ammonium  sulphide  group  is  effected,  as 
well  as  from  members  of  subsequent  groups. 

Separation  from  the  Alkaline  Earths.  Fusion  of  the  substance  with  sodium 
carbonate  and  extraction  of  the  melt  with  water  gives  a  solution  of  molybdenum, 
whereas  the  carbonates  of  barium,  calcium  and  strontium  remain  undissolved 
as  carbonates. 

Separation  from  Lead,  Copper,  Cadmium  and  Bismuth.  The  sulphides 
of  the  elements  are  treated  with  sodium  hydroxide  and  sodium  sulphide  solution 
and  are  digested  by  gently  heating  in  a  pressure  flask.  Molybdenum  dissolves, 
whereas  lead,  copper,  cadmium  and  bismuth  remain  insoluble.  If  the  solution 
of  the  above  elements  is  taken,  made  strongly  alkaline,  and  treated  with  H2S, 
the  sulphides  of  the  latter  elements  are  precipitated  and  molybdenum  remains 
in  solution.  The  precipitates  are  filtered  off  and  the  filtrate  containing  molyb- 
denum is  placed  in  the  pressure  flask,  the  solution  made  slightly  acid  with  sul- 
phuric acid  and  the  mixture  heated  under  pressure,  until  the  liquid  appears  colorless, 
MoS2  is  precipitated  and  may  be  converted  into  the  oxide  as  described  later. 

Separation  from  Vanadium  is  effected  by  a  molybdenum  sulphide  precipi- 
tation in  acid  solution. 

Separation  from  Arsenic.  Arsenic,  present  in  the  higher  state  of  oxida- 
tion, is  precipitated  by  magnesia  mixture,  added  to  a  slightly  acid  solution  (5  cc. 
of  concentrated  hydrochloric  acid  per  100  cc.  of  solution  for  each  0.1  gram 
arsenic).  The  solution  is  neutralized  with  ammonia  (methyl  orange),  and  the 
arsenic  salt  filtered  off.  MoS2  is  now  precipitated  with  H2S  in  presence  of  free 
sulphuric  acid  in  the  pressure  flask. 

Separation  from  Phosphoric  Acid.  Phosphoric  acid  is  precipitated  from  an 
ammoniacal  solution  as  magnesium  ammonium  phosphate.  Molybdenum  may 
then  be  precipitated  as  the  sulphide  from  the  filtrate. 

Separation  from  Titanium.  The  metals  of  the  ammonium  sulphide  group 
are  precipitated  by  adding  ammonium  hydroxide  and  ammonium  sulphide. 
Molybdenum  remains  in  solution  and  passes  into  the  filtrate.  H2S  is  passed  into 
the  solution  until  it  appears  red;  sulphuric  acid  is  then  added  until  the  solution 
is  acid,  when  molybdenum  sulphide  precipitates. 

Separation  from  Tungsten.  Molybdenum,  precipitated  with  tungsten  by 
the  lead  molybdate  method,  is  ignited  and  the  mixture  then  treated  with  hydro- 
chloric acid  and  a  few  drops  of  nitric  acid  and  evaporated  nearly  to  dryness. 
Dilute  hydrochloric  acid  is  added  and  the  solution  filtered.  Tungsten  remains 
undissolved. 

Molybdenum  may  be  precipitated  by  H2S  as  MoS2  in  presence  of  tartaric 
acid.  Tungsten  does  not  precipitate. 


278  MOLYBDENUM 

GRAVIMETRIC   METHODS   FOR   THE   DETERMINATION 
OF   MOLYBDENUM 

Precipitation  as  Lead  Molybdate 

Preliminary  Remarks.  This  method,  suggested  by  Chatard,  has  been 
pronounced  by  Brearly  and  Ibbotson  to  be  "  one  of  the  most  stable  processes 
found  in  analytical  chemistry."  "It  is  not  interfered  with  by  the  presence  of 
large  amounts  of  acetic  acid,  lead  acetate,  or  alkali  salts  (except  sulphates). 
The  paper  need  not  be  ignited  separately  and  prolonged  ignition  at  a  much  higher 
temperature  than  is  necessary  to  destroy  the  paper  does  no  harm.  From  faintly 
acid  solution  lead  molybdate  may  be  precipitated  free  from  impurities  in  the 
presence  of  copper,  cobalt,  nickel,  manganese,  zinc,  magnesium  and  mercury 
salts."  It  may  be  readily  separated  from  iron  and  chromium.  Barium,  stron- 
tium, uranium,  arsenic,  cadmium  and  aluminum  do  not  interfere  if  an  excess  of 
hydrochloric  acid  has  been  added  to  the  solution  followed  by  lead  acetate  and 
sufficient  ammonium  acetate  to  destroy  the  free  mineral  acid. 

The  precipitate  is  granular,  easily  filtered  and  washed. 

Vanadium  and  tungsten,  if  present,  must  be  removed,  by  separating  from 
molybdenum  by  one  of  the  procedures  given. 

Special  Reagents.  Lead  Acetate.  A  4%  solution  is  made  by  dissolving 
20  grams  of  the  salt  in  500  cc.  of  warm  water.  A  few  cc.  of  acetic  acid  are  added 
to  clear  the  solution. 

Precipitation  of  Lead  Molybdate.  An  excess  of  lead  acetate  is  added  to 
the  acetic  acid  solution,  containing  molybdenum  (see  Separation  in  Presence 
of  Large  Amounts  of  Iron),  (10  cc.  of  4%  solution  of  the  crystallized  lead  acetate 
salt  will  precipitate  0.01  gram  of  molybdenum).  The  solution  is  heated  to  boil- 
ing, the  crystalline  precipitate  allowed  to  settle  for  a  few  minutes  on  the  steam 
bath,  then  filtered  hot  onto  an  ashless  filter  (S.  &  S.  No.  590  quality)  and  washed 
free  of  chlorides  with  hot  water. 

The  precipitate  dried  and  ignited  in  a  porcelain  crucible  at  red  heat  for  about 
twenty  minutes  is  weighed  as  PbMo04. 

PbMo04X0.2615  =Mo.    PbMo04X0.3923  =Mo03. 
MoX3.8241  =PbMo04.     Mo03X2.5491  =PbMo04. 

Determination  of  Molybdenum  as  the  Oxide,  MoO3 
Determination  by  Precipitating  with  Mercurous  Nitrate 

Especially  applicable  where  fusion  with  an  alkali  carbonate  has  been  required. 

Decomposition  of  Ore.  One  gram  of  the  ore  is  fused  with  4  grams  of  fusion 
mixture,  (Na2C03+K2C03+KN03),  and  the  cooled  melt  extracted  with  hot  water. 

If  manganese  is  present,  indicated  by  a  colored  solution,  it  may  be  removed 
by  reduction  with  alcohol,  the  manganese  precipitate  filtered  off  and  washed  with 
hot  water,  the  solution  evaporated  to  near  dryness  and  taken  up  with  water, 
upon  addition  of  nitric  acid  as  stated  below. 

The  solution  containing  the  alkaline  molybdate  is  nearly  neutralized  by 
adding  HN03,  the  amount  necessary  being  determined  by  a  blank,  and  to  the 
cold,  slightly  alkaline  solution,  a  faintly  acid  solution  of  mercurous  nitrate  is 


MOLYBDENUM  279 

added  until  no  further  precipitation  occurs.  The  precipitate  consists  of  mer- 
curous  molybdate  and  carbonate  (chromium,  vanadium,  tungsten,  arsenic  and 
phosphorus  will  also  be  precipitated  if  present).  The  solution  containing  the 
precipitate  is  boiled  and  allowed  to  stand  ten  to  fifteen  minutes  to  settle,  the  black 
precipitate  is  filtered  off  and  washed  with  a  dilute  solution  of  mercurous  nitrate. 
The  precipitate  is  dried,  and  as  much  as  possible  transferred  to  a  watch-glass. 
The  residue  on  the  filter  is  dissolved  with  hot  dilute  nitric  acid,  and  the  solution 
received  in  a  large  weighed  porcelain  crucible.  The  solution  is  evaporated  to 
dryness  on  the  water  bath  and  the  main  portion  of  the  precipitate  added  to  this 
residue,  and  the  product  heated  cautiously  over  a  low  flame  l  until  the  mercury 
has  completely  volatilized.  The  cooled  residue  is  weighed  as  Mo03. 

Mo03X0.6667=Mo. 

NOTE.  If  Cr,  V,  W,  As  or  P  are  present  a  separation  must  be  effected.  Molyb- 
denum should  be  precipitated  in  an  H2SO4  solution  in  a  pressure  flask  as  the  sulphide 
by  H2S  as  given  in  the  following  method,  and  arsenic  if  present  removed  by  magnesia 
mixture  as  indicated  in  the  procedure  for  separation  of  arsenic  from  molybdenum. 
If  these  impurities  are  present  the  molybdenum  oxide  may  be  fused  with  a  very  little 
Na2CO3,  and  leached  with  hot  water  and  the  filtrate  treated  with  H2S  as  directed. 


Precipitation  of  Molybdenum  as  the  Sulphide  by  h^S 

A.  Precipitation   from   Acid   Solution.     By    this    procedure  molybdenum 
is  precipitated  along  with  members  of  the  hydrogen  sulphide  group,  if  present, 
but  free  from  elements  of  the  following  groups. 

The  cold  molybdenum  solution  slightly  acid  with  sulphuric  acid  (in  presence 
of  Ba,  Sr  or  Ca  an  HC1  solution  is  necessary)  is  placed  in  a  small  pressure 
flask  and  saturated  with  H2S,  the  flask  closed  and  heated  on  the  water  bath  until 
the  precipitate  has  settled.  The  solution  is  cooled  and  filtered  through  a  weighed 
Gooch  crucible. 

B.  Precipitation  from  an  Ammoniacal  Solution.     By  this  procedure  molyb- 
denum is  precipitated  with  antimony,  arsenic,  tin  if  present,  but  is  free  from 
mercury,  lead,  bismuth,  copper  and  cadmium. 

Hydrogen  sulphide  is  passed  into  the  cold  ammoniacal  solution  of  molybdenum 
until  it  assumes  a  bright  red  color,  it  is  now  acidified  with  dilute  sulphuric  acid, 
the  precipitate  allowed  to  settle  and  the  solution  filtered  through  a  weighed 
Gooch  crucible. 

In  either  case  A  or  B  the  precipitate  is  washed  into  the  Gooch  crucible 
with  very  dilute  sulphuric  acid  followed  by  several  washings  with  the  acid  and 
then  with  alcohol  until  free  from  acid.  The  Gooch  is  placed  within  a  larger 
nickel  crucible  and  covered  with  a  porcelain  lid.  After  drying  at  100°  C.  it  is 
placed  over  a  small  flame  and  carefully  heated  until  the  odor  of  S02  can  no  longer 
be  detected.  The  cover  is  now  removed  and  the  open  crucible  heated  to  constant 
weight.  The  residue  consists  of  Mo03. 

Mo03X0.6667=Mo. 

NOTE.  Arsenic  will  contaminate  the  residue  if  present.  The  method  for  its 
removal  has  been  given. 

1  The  oxide,  MoO3,  sublimes  at  bright  red  heat. 


280  MOLYBDENUM 

VOLUMETRIC  METHODS   FOR  THE   DETERMINATION 
OF  MOLYBDENUM   OR  MOLYBDIC  ACID 

The  lodometric  Reduction  Method  1 

Principle.  When  a  mixture  of  molybdic  acid  and  potassium  iodide  in  pres- 
ence of  hydrochloric  acid  is  boiled,  the  volume  having  denned  limits,  free  iodine 
is  liberated  and  expelled  and  the  molybdic  acid  reduced  to  a  definite  lower  oxide; 
by  titrating  with  a  standard  oxidizing  agent  the  molybdic  acid  is  determined. 

Reaction.    2Mo03+4KI+4HCl  =2Mo02I+I2+4KCl+2H20. 

Reagents.  N/10  solutions  of  iodine,  sodium  arsenite,  potassium  permanga- 
nate, sodium  thiosulphate. 

Analytical  Procedure.2  Reduction.  The  soluble  molybdate  in  amount 
not  exceeding  an  equivalent  of  0.5  gram  Mo03  is  placed  in  a  150-cc.  Erlenmeyer 
flask,  20  to  25  cc.  of  hydrochloric  acid  (sp.gr.  1.2)  added  together  with  0.2  to  0.6 
gram  potassium  iodide.  A  short  stemmed-funnel  is  placed  in  the  neck  of  the 
flask  to  prevent  mechanical  loss  during  the  boiling.  The  volume  of  the  solution 
should  be  about  60  cc.  The  solution  is  boiled  until  the  volume  is  reduced  to 
exactly  25  cc.  as  determined  by  a  mark  on  the  flask.  The  residue  is  diluted 
immediately  to  a  volume  of  125  cc.  and  cooled.  Either  process  A  or  B  may 
now  be  followed. 

A.  Reoxidation  by  Standard  Iodine.  A  solution  of  tartaric  acid,  equiv- 
alent to  1  gram  of  the  solid,  is  now  added,  and  the  free  acid  nearly  neutralized 
with  sodium  hydroxide  solution  (litmus  or  methyl  orange  indicator)  and  finally 
neutralized  with  sodium  acid  carbonate,  NaHC03,  added  in  excess.  A  measured 
amount  of  N/10  iodine  is  now  run  in.  The  solution  is  set  aside  in  a  dark  closet 
for  two  hours,  in  order  to  cause  complete  oxidation,  as  the  reaction  is  slow.  The 
excess  iodine  is  now  titrated  with  N/10  sodium  arsenite. 

One  cc.  N/10  iodine  =  .0144  gram  Mo03  =  .0096  gram  Mo. 

On  long  standing  a  small  amount  of  iodate  is  apt  to  form.  This  is  determined 
by  making  acid  with  dilute  HC1  and  titrating  with  N/10  sodium  thiosulphate. 

B.  Reoxidation  of  the  Residue  by  Standard  Permanganate.  To  the 
reduced  solution  about  0.5  gram  of  manganese  sulphate  in  solution  is  added, 
followed  by  a  measured  amount  of  N/10  permanganate  solution,  added  from  a 
burette  until  the  characteristic  pink  color  appears.  A  measured  amount  of 
standard  N/10  sodium  arsenite,  equivalent  to  the  permanganate  is  then  run  in 
and  about  3  grams  of  tartaric  acid  added.  The  acid  is  neutralized  by  acid  sodium 
or  potassium  carbonate,  the  stopper  and  the  sides  of  the  flask  rinsed  into  the  main 
solution.  The  residual  arsenite  is  now  titrated  by  N/10  iodine,  using  starch 
indicator. 

NOTES.  Tartaric  acid  prevents  precipitation  during  the  subsequent  neutraliza- 
tion with  NaHCO,.  A  and  B. 

The  addition  of  manganese  salt  in  B  is  to  prevent  the  liberation  of  free  chlorine 
by  the  action  of  KMnO4  on  HC1. 

In  addition  to  the  oxidation  of  the  lower  oxides  to  molybdic  acid,  potassium  per- 
manganate added  in  B  liberates  free  iodine  from  HI,  it  produces  iodic  acid,  and  forms 
the  higher  oxides  of  manganese.  The  standard  arsenite,  on  the  other  hand,  converts 
free  iodine  and  the  iodate  to  HI  and  reduces  the  higher  oxides  of  manganese. 

1  F.  A.  Gooch  and  Charlotte  Fairbanks,  Am.  Jour.  Sc.  (4),  2,  160. 
*F.  A.  Gooch  and  O.  S.  Pulman,  Jr.  Am.  Jour.  Sc.  (4),  12,  449. 


MOLYBDENUM 


281 


Estimation  by  Reduction  with  Jones  Reductor  and  Oxidation  by 
Standard  Permanganate  Solution 

Principle.  The  procedure  depends  upon  the  reduction  of  molybdic  acid 
to  Mo203  by  passing  its  solution  through  a  column  of  amalgamated  zinc  into  a 
solution  of  ferric  alum,  and  subsequent  oxidation  to  Mo03  by  standard  potas- 
sium permanganate  solution. 

Reactions.     2Mo03+3Zn  =Mo203+3ZnO. 

5Mo203+6KMn04+9H2SO4  =  10Mo03+3K2S04+6MnS044-9H20. 


approximately    N/10    standardized 


Reagents.     Potassium     permanganate 
against  a  standard  molybdic  acid  solution. 
10%  solution  of  ferric  alum. 
2.5%  solution  of  sulphuric  acid. 
Apparatus.    Jones  Reductor. 

12  =  reductor  tube   50   cm.    long,   2  cm.   inside 
diameter.     Smaller  tube  prolongation  length 
20  cm.  inside  diameter  0.5  cm. 
Zn  =  column  of  zinc  40  cm.  long.     Zn  shot  8  mesh 

to  sq.cm.; 
F  =  receiving  flask; 

P  =  pressure  regulator  with  gauge,  set  to  give 
pressure  in  receiving  flask  of  less  than  20  cm. 
water; 

G  =  platinum  cone  or  gauze  with  mat  of  fine  glass 
wool  2  cm.  thick; 

The  zinc  in  reductpr  should  be  protected  from 
the  air  by  covering  with  water,  stop-cock  S  being 
closed  when  not  in  use. 

Procedure.  The  receiving  flask  of  the 
Jones  reductor,  Fig.  49,  is  charged  with  about 
30  cc.  of  10%  ferric  alum  and  4  cc.  of  phosphoric 
acid.2  Through  the  40-cm.  column  of  amalga- 
mated zinc  in  the  reductor  are  passed  in  suc- 
cession 100  cc.  of  hot  dilute  sulphuric  acid 
(2.5%  sol.),  the  molybdic  a?id  in  the  form  of 
ammonium  molybdate  dissolved  in  10  cc.  of 
water  and  acidified  with  100  cc.  of  hot  dilute 
sulphuric  acid  followed  by  200  cc.  more  of  the 
hot  dilute  sulphuric  acid  and  100  cc.  of  hot  water.  The  reduced  green  molybdic 
acid  upon  coming  in  contact  with  the  ferric  alum  solution  produces  a  bright  red 
color. 

The  hot  solution  is  titrated  with  N/10  KMn04  solution. 


Rubber 


Hg  Gage 


Suction . 


FIG.  49. — Jones  Reductor. 


Oi44  0096 

One  cc.  of  N/10  KMn04  =— -  -  gram  Mo03  =—   —  gram  molybdenum. 


1 W.  A.  Noyes  and  Frohman,  Jr.  Am.  Chem.  Soc.,  35,  919. 

See  Method  by  C.  R.  Dudley,  D.  L.  Randall,  Am.  Jr.  Sc.  (4),  24,  313. 
*C.  Reinhardt,  Chem.  Ztg.,  13,  33. 


282  MOLYBDENUM 

Method   for  Determining   Molybdenum  and  Vanadium  in  a 
Mixture  of  their  Acids 

Principle  of  the  Method.  The  procedure  depends  upon  the  fact  that 
vanadic  acid  alone  is  reduced  by  S02X  in  a  sulphuric  acid  solution,  whereas  both 
vanadic  and  molybdic  acids  are  reduced  by  amalgamated  zinc,  in  each  case  the 
reducing  agents  forming  definite  lower  oxides  which  are  readily  oxidized  to 
definite  higher  oxides  by  KMn04. 

Reactions. 

S02  Reduction: 

1.  V205+S02  = V204+S03.     (No  action  on  Mo03.) 

Zn  Reduction : 

2.  V205+3Zn=V202+3ZnO. 

3.  2Mo03+3Zn=Mo203+3ZnO. 

KMn04  Oxidation: 

4.  5V204+2KMn04+3H2S04  =5V205+K2S04+MnS04+3H20. 

5.  5V202+6KMn04+9H2S04  =5V205+3K2S04+6MnS04+9H20. 

6.  5Mo203+6KMn04+9H2S04  =  10Mo03+3K2S04+6MnS04+9H20. 

From  the  reactions  "  4  "  and  "  5  "  it  is  seen  that  three  times  the  amount 
of  KMn04  is  required  to  oxidize  V202  to  V206  as  is  required  in  the  case  of  V204, 
hence — total  cc.  KMn04  required  in  oxidation  of  the  zinc-reduced  oxides  minus 
three  times  the  cc.  KMn04  required  in  oxidizing  the  tetroxide  of  vanadium 
formed  by  the  sulphur  dioxide  reduction  =cc.  KMn04  required  to  oxidize  Mo203 
to  Mo03.  From  these  data  molybdenum  and  vanadium  may  readily  be  calculated. 

Method  of  Procedure.  A.  Vanadic  Acid.  The  solution  containing  the 
vanadic  and  molybdic  acids  in  a  250-  to  300-cc.  Erlenmeyer  flask,  is  diluted  to 
75  cc.  acidified  with  2  to  3  cc.  of  strong  sulphuric  acid,  heated  to  boiling  and  the 
vanadic  acid  reduced  by  a  current  of  S02  passed  into  the  solution  until  the  clear 
blue  color  indicates  the  complete  reduction  of  the  vanadic  acid  to  V204.  The 
boiling  is  now  continued  and  C02  passed  into  the  flask  to  expel  the  last  trace  of  S02. 

Standard  N/10  KMnO4  is  now  run  into  the  reduced  solution  to  the  character- 
istic faint  pink.  From  reaction  "  4,"  vanadic  acid  may  be  calculated. 

One  cc.  N/10  KMn04  =  .0182  gram  V205  =  .0051  gram  vanadium. 

B.  Molybdic  Acid.  The  reduction  by  Jones'  reductor,  and  titration  of  the 
combined  acids  reduced  by  amalgamated  zinc  with  N/10  potassium  permanganate 
solution,  is  carried  out  exactly  as  described  in  the  determination  of  molybdic 
acid  alone.  In  this  case  50  cc.  of  10%  ferric  alum  and  8  cc.  of  the  phosphoric 
acid  is  placed  in  the  receiving  flask. 

Calculation.  Total  permanganate  titration  in  B  minus  three  times  the  titration 
in  A  gives  the  permanganate  required  to  oxidize  Mo203  to  Mo03.  From  equation 
6  the  molybdic  acid  may  now  be  calculated. 


C\~\  A  \ 

One  cc.  N/10  KMn04=^-;    -  gram  Mo03=:— - —  gram  molybdenum. 
3  3 

1  Reduction  of  vanadium  by  SO2  in  presence  of  molybdenum,  Graham  Edgar, 
Am.  Jour.  Sc.,  (4)  25,  332.  No  reduction  of  MoO3  when  0.4  gram  is  present  with  5  cc. 
H2SO4  in  25  cc.  volume. 

For  theoretical  considerations  and  data  on  accuracy  of  method  see  "  Methods 
in  Chemical  Analysis,"  F.  A.  Gooch. 


NICKEL 

W.  L.  SAVELL 
Ni,  at.  wt.  58.68;  sp.  gr.  8.6-8.9;  m.p.  1452°  C.;  oxides,  NiO,  Ni2O3,  Ni3O4. 

DETECTION 

After  bringing  the  sample  into  solution  by  one  of  the  methods  described  under 
Preparation  and  Solution  of  the  Sample,  silica  is  removed,  if  present,  in  the  usual 
manner,  by  evaporating  the  solution  to  dryness  in  the  presence  of  an  excess  of 
hydrochloric  acid,  dissolving  the  residue  and  boiling  with  hydrochloric  acid  and 
filtering  off  the  silica. 

Hydrogen  sulphide  is  then  passed  through  the  solution  to  remove  the  elements 
precipitated  by  this  reagent.  The  filtrate  from  this  precipitation  is  then  boiled 
to  expel  the  excess  of  hydrogen  sulphide  and  a  little  nitric  acid  added  to  oxidize 
any  ferrous  iron  to  the  ferric  state.  (See  page  285,  Separations.)  Ammonium 
hydroxide  is  then  added  to  precipitate  iron,  aluminum  and  chromium.  Cobalt, 
nickel,  manganese  and  zinc  are  precipitated  from  the  filtrate  by  adding  a  solution 
of  colorless  ammonium  sulphide  or  by  passing  hydrogen  sulphide  through  the 
ammoniacal  solution.  Manganese  and  zinc  are  separated  from  the  precipitate 
by  washing  with  cold  hydrochloric  acid  of  about  1.035  sp.gr.  A  small  quantity 
of  the  precipitate  is  fused  with  borax  in  the  loop  of  a  clean  platinum  wire.  A 
green  color  in  the  cool  bead  indicates  nickel.  Fairly  small  quantities  of  cobalt 
interfere  with  this  test,  so  if  the  bead  is  colored  blue  it  will  be  necessary  to  make 
further  tests  for  nickel. 

Dimethylglyoxime  will  precipitate  nickel  as  oxime  from  an  acetic  acid  solution 
containing  sodium  acetate  and  in  this  manner  separate  it  from  cobalt,  manganese 
and  zinc.  After  precipitating  iron,  aluminum  and  chromium  and  filtering  them 
off,  the  solution  is  slightly  acidified  with  hydrochloric  acid,  then  is  neutralized 
with  sodium  hydroxide,  and  acidified  with  acetic  acid.  A  solution  of  dimethyl- 
glyoxime  is  added,  when  nickel,  if  present,  will  be  precipitated  as  a  flocculent  red 
precipitate. 

Nickel  may  be  detected  in  the  presence  of  cobalt  by  adding  a  solution  of 
sodium  hydroxide  to  the  solution  of  cobalt  and  nickel  until  a  slight  precipitate 
is  formed,  then  somewhat  more  potassium  cyanide  than  is  necessary  to  redissolve 
the  precipitate  and  finally  two  volumes  of  bromine  water.  Warm  gently  and 
allow  to  stand  for  some  time.  If  a  precipitate  of  nickel  hydroxides  separates, 
filter,  wash  and  test  with  the  borax  bead. 

Nickel  may  also  be  detected  in  the  presence  of  cobalt  by  precipitating  the 
cobalt  as  nitrite,  as  described  in  the  chapter  on  cobalt,  and  then  precipitating  the 
nickel  as  hydroxide  with  sodium  hydroxide  and  bromine  water  and  testing  the 
precipitate  with  the  borax  bead. 

Alpha  benzildioxime  added  to  an  ammoniacal  solution  of  nickel  precipitates 
an  intensely  red  salt  having  the  composition  C28H22N404Ni.  This  precipitate 
is  very  voluminous.  Silver,  magnesium,  chromium,  manganese  and  zinc  do  not 
interfere  with  this  reaction. 

283 


284  NICKEL 


ESTIMATION 

The  determination  of  nickel  is  required,  principally,  in  the  analysis  of  ores, 
metallic  nickel  and  its  alloys,  but  is  also  required  in  the  analysis  of  metallic 
cobalt  and  cobalt  products  as  well  as  in  a  host  of  miscellaneous  materials. 

In  the  majority  of  cases  the  results  of  a  nickel  determination  are  calculated 
in  terms  of  metallic  nickel.  Even  in  the  determination  of  nickel  in  nickel-plating 
solution  the  results  are  calculated  in  terms  of  metallic  nickel  since  this  is  the 
factor  by  which  the  solutions  are  controlled. 

Preparation  and  Solution  of  the  Sample 

The  materials  in  which  nickel  occurs  ordinarily,  may,  in  general,  be  brought 
into  solution  by  treatment  with  acids,  but  in  the  case  of  some  refractory  ores  and 
alloys,  a  fusion  is  required  first  to  make  the  acid  treatment  effective.  When 
treating  ores  containing  sulphides  or  arsenides  a  strong  oxidizing  treatment  is 
necessary  to  break  up  these  compounds.  Metallic  nickel  may  be  dissolved  easily 
in  nitric  acid,  more  slowly  in  hydrochloric  acid  and  still  more  slowly  by  sulphuric. 
Nickel  alloys  may  be  dissolved  in  a  mixture  of  hydrochloric  acid  and  nitric  acid. 

General  Procedure  for  Ores.  One  gram  of  the  finely  powdered  ore  is  weighed 
into  a  porcelain  dish  and  mixed  intimately  with  3  grams  of  powdered  potassium 
chlorate.  The  dish  is  covered  with  a  watch-glass  and  40  cc.  concentrated  nitric 
acid  added  slowly.  The  dish  is  allowed  to  stand  in  a  cool  place  for  a  few  minutes, 
then  placed  on  a  water  bath  and  digested  until  the  sample  is  completely  decom- 
posed, stirring  the  mixture  frequently  with  a  glass  stirring  rod,  and  adding  a  little 
potassium  chlorate  from  time  to  time  until  the  decomposition  is  complete.  The 
watch-glass  is  then  removed  and  any  particles  that  may  have  spattered  on  ifc 
are  washed  back  into  the  dish  and  the  evaporation  continued  to  dryness.  This 
evaporation  to  dryness  is  repeated  with  the  addition  of  10  cc.  of  concentrated 
hydrochloric  acid,  and  the  silica  dehydrated  by  heating  for  an  hour  or  more  in  an 
air  oven  at  110°  C.  The  dry  residue  is  moistened  with  concentrated  hydrochloric 
acid  and  the  sides  of  the  dish  washed  down  with  hot  water,  the  mixture  heated 
to  boiling  and  allowed  to  boil  for  a  few  minutes,  then  withdrawn  from  the  heat 
and  filtered,  hot,  after  the  insoluble  matter  has  settled. 

Treat  the  filtrate  for  the  removal  of  interfering  elements  as  directed  under 
Separations. 

Fusion  Method.  The  above  method  is  used  where  it  is  desired  to  determine 
insoluble  matter  or  "  gangue."  As  a  method  of  bringing  the  nickel  in  the  sample 
into  solution  it  is  quite  satisfactory  and  when  the  insoluble  matter  burns  to  a 
pure  white  ash  the  ignited  residue  may  be  weighed  as  silica,  but  in  some  cases 
this  method  does  not  give  sufficient  information  regarding  the  composition  of 
the  gangue. 

If  it  is  necessary  to  make  a  complete  analysis  it  is  usually  better  to  fuse  the 
sample  with  the  sodium  and  potassium  carbonate  mixture  containing  a  little 
potassium  nitrate  and  then  treat  in  the  usual  manner  to  determine  silica. 

Potassium  Bisulphate  Fusion.  In  the  treatment  of  nickel  and  cobalt  oxides 
these  are  ground  to  a  fine  powder  and  a  representative  sample  of  1  gram  is  fused 
with  10  grams  of  potassium  bisulphate.  This  may  be  done  in  a  porcelain  or 
plica  crucible  or  dish.  The  melt  is  extracted  with  water  and  the  silica  filtered  off. 

A  small  casserole  has  been  found  to  be  very  useful  for  this  fusion. 


NICKEL  285 

Solution  of  Metallic  Nickel  and  Its  Alloys.  From  1  to  5  grams  of  the  well- 
mixed  drillings  are  treated  with  a  minimum  quantity  of  nitric  acid  and  20  cc. 
1  :  1  sulphuric  acid  added  and  the  solution  evaporated  to  fumes  of  sulphur  tri- 
oxide.  Allow  the  fuming  to  continue  for  ten  minutes.  Dilute  carefully  with  a 
little  water  and  filter  off  the  insoluble.  Continue  as  directed  in  the  following 
detailed  analyses. 

It  may  be  necessary  to  use  a  mixture  of  nitric  and  hydrochloric  acids  to  bring 
certain  alloys  into  solution,  after  which  the  procedure  is  the  same  as  above. 

SEPARATIONS 

Separation  of  the  Ammonium  Sulphide  Group,  Containing  Nickel  from 
the  Hydrogen  Sulphide  Group.  Mercury,  Lead,  Bismuth,  Copper,  Cadmium, 
Arsenic,  Antimony,  Tin,  Gold,  Molybdenum,  etc. 

The  hydrogen  sulphide  group  elements  are  precipitated  from  an  acid  solution 
(HC1)  by  H2S,  and  removed  by  nitration,  nickel,  etc.,  passing  into  the  filtrate. 

Separation  of  the  Ammonium  Sulphide  Group  from  the  Alkaline  Earths 
and  Alkalies.  Nickel  is  precipitated  with  other  members  of  the  group  by 
passing  H2S  into  its  ammoniacal  solution,  or  by  adding  (NH4)2S  solution.  The 
alkaline  earths  and  alkalies  are  not  precipitated. 

Separation  of  Nickel  from  Cobalt.  This  procedure  can  be  carried  out  in 
exactly  the  same  manner  as  the  method  given  for  the  determination  of  nickel 
by  precipitation  of  nickel  with  dimethylglyoxime,  since  cobalt  is  soluble  as  oxime. 
In  case  more  cobalt  is  present  than  nickel  a  larger  excess  of  the  reagent  must  be 
used.  The  excess  of  acid  is  best  neutralized  with  ammonium  hydroxide.  If 
both  metals  are  to  be  determined,  cobalt  may  be  determined  electrolytically 
in  the  filtrate. 

An  alternate  method  is  to  determine  the  cobalt  and  nickel  as  oxides,  or  metal 
by  electrolysis,  together.  The  oxides,  or  plate,  are  dissolved  in  nitric  acid  and 
the  nickel  determined  in  the  solution,  cobalt  being  found  by  difference. 

For  other  methods  see  Separation  of  Cobalt  from  Nickel,  under  Cobalt,  page  142. 

Separation  of  Nickel  from  Manganese.  Nickel  is  precipitated  by  dimethyl- 
glyoxime from  an  acetic  acid  solution  containing  sodium  acetate,  manganese 
being  determined  in  the  filtrate. 

Separation  of  Nickel  from  Zinc.  Zinc  does  not  interfere  in  the  dimethyl- 
glyoxime precipitation  of  nickel  when  ammonium  salts  are  present.  It  is  advis- 
able to  precipitate  the  nickel  in  a  dilute  acetic  acid  solution,  thus  avoiding  the 
addition  of  a  large  amount  of  ammonium  salts  as  would  be  necessary  if  the  pre- 
cipitation took  place  in  an  ammoniacal  solution.  Zinc  readily  remains  in  solution, 
and  may  be  determined  in  the  filtrate  from  the  nickel  oxime  precipitate.  The 
following  procedure  is  recommended: 

The  solution  containing  the  two  metals  is  neutralized  with  ammonium  hydrox- 
ide and  then  made  just  slightly  acid  with  acetic  acid  and  sodium  acetate  added. 
Dimethylglyoxime  solution  is  now  added  to  the  solution,  which  is  nearly  boiling, 
and  the  procedure  given  for  the  determination  of  nickel  by  this  reagent  is  followed. 

Separation  of  Nickel  from  Iron.  Nickel  cannot  be  separated  satisfactorily 
from  iron  by  precipitating  the  latter  with  ammonium  hydroxide,  as  some  of  the 
nickel  is  invariably  occluded  by  the  ferric  hydroxide  precipitate.  Two  modi- 
fications of  the  oxime  method  may  be  used. 

(1)  The  iron,  if  present  as  a  ferric  salt,  is  converted  into  a  complex  salt  by 


286  NICKEL 

adding  from  1  to  2  grams  of  tartaric  acid,  and  the  solution  diluted  to  200  or  300 
cc.,  boiled  and  the  nickel  precipitated  as  the  oxime  in  an  ammoniacal  solution 
by  the  prescribed  method.  Iron  forms  no  oxime  under  these  conditions. 

The  iron  may  be  precipitated  from  this  filtrate  by  colorless  ammonium  sul- 
phide and  the  sulphide  converted  to  ferric  oxide  (Fe203)  by  ignition. 

(2)  Ferric  iron  is  reduced  to  the  ferrous  condition  by  warming  with  sulphurous 
acid,  in  a  nearly  neutral  solution.  If  the  original  solution  has  an  excess  of  acid, 
it  is  treated  with  a  solution  of  sodium  hydroxide  until  a  permanent  precipitate 
is  formed.  This  is  dissolved  with  a  few  drops  of  hydrochloric  acid  and  the  iron 
reduced  by  adding  from  5  to  10  cc.  of  a  saturated  solution  of  sulphur  dioxide  or 
by  passing  dioxide  through  the  solution.  The  solution  is  diluted  to  200  or  300  cc. 
and  the  solution  of  dimethylglyoxime  added  in  slight  excess,  followed  by  sodium 
acetate  until  a  permanent  precipitate  of  nickel  oxime  is  formed.  After  adding  2 
grams  more  of  sodium  acetate  the  solution  is  filtered  immediately.  The  iron 
is  precipitated  from  the  filtrate  by  oxidizing  with  bromine  water  and  adding 
ammonium  hydroxide  to  precipitate  the  basic  acetate  of  iron. 

Procedure  (1)  is  suitable  for  the  determination  of  nickel  in  iron  and  steel. 

Separation  of  Nickel  from  Aluminum.  This  method  is  the  same  as  pro- 
cedure (1)  given  above. 

Separation  of  Nickel  from  Chromium.  This  separation  cannot  be  carried  out 
in  an  acetic  acid  solution.  From  1  to  2  grams  of  tartaric  acid  are  added  and  from 
5  to  10  cc.  of  a  10%  ammonium  chloride  solution,  subsequently.  The  solution 
is  made  ammoniacal,  but  no  precipitate  should  form.  If  the  solution  becomes 
cloudy,  it  is  acidified  with  hydrochloric  acid  and  additional  ammonium  chloride 
added  and  again  made  ammoniacal  and  the  nickel  precipitated  as  oxime  accord- 
ing to  directions  given  from  this  precipitation. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 

OF  NICKEL 

Precipitation  of  Nickel  by  Alpha  Benzildioxime 

The  alcoholic  solution  of  alpha  benzildioxime  gives  an  intensely  red  precipi- 
tate of  C^H^N^Ni,  when  added  to  ammoniacal  solutions  containing  nickel. 
The  reaction  is  more  characteristic  for  nickel  than  is  that  with  dimethylgly- 
oxime and  is  more  delicate.  In  a  volume  of  5  cc.  (according  to  F.  H.  Atack), 
1  part  of  nickel  in  2,000,000  parts  of  water  may  be  detected.  In  the  presence  of 
100  times  as  much  as  cobalt  only  a  faint  yellow  color  is  produced  by  the  cobalt. 
One  port  of  nickel  per  million  of  water  will  cause  precipitation  with  the  compound, 
whereas  no  precipitate  is  formed  with  dimethylglyoxime  under  the  same  condi- 
tions. With  glyoxime  iron  produces  a  pink  color,  with  alpha  benzildioxime 
ferrous  salts  give  a  faint  violet  color,  hence  do  not  interfere  in  the  detection  of 
nickel.  Silver,  magnesium,  chromium,  manganese,  and  zinc  do  not  interfere. 
Since  the  nickel  precipitate  with  this  reagent  is  exceedingly  voluminous  it  is 
advisable  to  have  not  more  than  0.025  gram  of  nickel  in  the  solution  in  which  the 
nickel  is  being  determined.  •  The  method  is  adapted  to  the  detection  and 
determination  of  minute  traces  of  the  element  up  to  small  amounts  of  less  thai) 
10%  nickel. 


NICKEL  287 

Reagent,  Alpha  Benzildioxime.  This  may  be  prepared  by  boiling  10  grams  of 
benzil  (not  necessarily  pure)  with  8  to  10  grams  of  hydroxylamine  hydrochloride 
in  methyl  alcohol  solution.  After  boiling  for  three  hours  the  precipitate  is 
filtered  off  and  dried,  washed  with  hot  water  and  then  with  a  small  amount  of 
50%  alcohol,  and  dried.  This  dried  precipitate  consists  of  pure  benzildioxime 
(m.p.  237°  C.).  A  further  yield  may  be  obtained  by  boiling  the  nitrate  with 
hydroxylamine  hydrochloride.  The  reagent  is  prepared  by  dissolving  0.2  gram 
of  the  salt  per  liter  of  alcohol  to  which  is  added  ammonium  hydroxide  to  make 
5%  solution,  sp.gr.  0.96  (50  cc.  per  liter). 

Procedure.  A  slight  excess  of  the  warmed  solution  of  the  above  reagent  is 
stirred  into  the  ammoniacal  solution  containing  nickel  and  the  whole  heated 
on  the  water  bath  for  a  few  moments  to  coagulate  the  precipitate.  Quantitative 
precipitation  is  complete  after  one  minute.  The  liquid  is  filtered  through  a 
Gooch  crucible,  with  suction,  or  onto  a  filter  paper,  for  which  a  counterpoise 
has  been  selected.  The  counterpoise  paper  is  treated  in  exactly  the  same  manner 
as  the  one  containing  the  precipitate.  The  precipitate  is  washed  with  50% 
alcohol,  followed  by  hot  water,  and  is  then  dried  at  110°  C.  In  weighing  the 
precipitate  the  counterpoise  filter  is  placed  in  the  weight  pan  of  the  balance.  The 
precipitate  contains  10.93%  nickel.  Weight  of  C28H22N404NiX0.1093  =  Ni. 

NOTES.  Acetone  may  be  used  instead  of  alcohol  as  a  solvent  of  the  reagent.  The 
compound  is  more  soluble  in  acetone  than  in  alcohol. 

The  precipitate  does  not  pass  through  the  filter  as  does  the  compound  with  dimethyl- 
glyoxime. 

The  method  is  affected  by  the  presence  of  nitrates,  hence  these  must  be  removed 
by  evaporation  of  the  solution  with  sulphuric  acid  to  fumes,  before  the  addition  of 
the  reagent  to  the  nickel  solution. 

In  the  presence  of  cobalt  an  excess  of  the  reagent  must  be  used,  as  in  the  case  of 
the  dime  thy  Iglyoxime  precipitation. 

In  the  presence  of  iron  and  chromium  Rochelle  salt,  sodium  citrate  or  tartaric 
acid  are  added  to  prevent  precipitation  of  the  hydroxides  of  these  metals  upon  making 
the  solution  alkaline. 

In  the  presence  of  manganese  a  fairly  large  excess  of  the  reagent  is  required,  the 
solution  being  slightly  acid  with  acetic  acid. 

Zinc  and  magnesium  are  kept  in  solution  by  addition  of  ammonium  chloride. 

Large  amounts  of  copper  must  be  removed  by  precipitating  with  hydrogen  sul- 
phide before  addition  of  the  reagent. 

The  nickel  salt  with  the  reagent  forms  an  extremely  voluminous  precipitate  so  that 
a  concentration  of  0.09  gram  of  nickel  per  250  cc.  is  as  high  as  is  desirable.  The 
process  is  applicable  to  the  determination  of  nickel  in  the  filtrate  obtained  in  the 
separation  of  zinc  after  the  removal  of  the  hydrogen  sulphide,  formic  acid,  etc. 

Method  by  F.  W.  Atack,  The  Analyst,  38,  448,  318.  Cockburn,  Gardiner  and 
Black,  Analyst,  38,  439,  443. 

Precipitation  of  Nickel  by  Dimethylglyoxime 

Preliminary  Considerations.  This  method  has  been  demonstrated  by  0. 
Brunck  to  be  the  most  accurate  and  expeditious  procedure  known  for  nickel.1 
By  this  method  1  part  of  nickel  may  be  detected  when  mixed  with  5000  parts  of 
cobalt  or  1  part  of  nickel  may  be  detected  in  400,000  parts  of  water.  The 
nickel  precipitate  with  this  reagent  is  almost  completely  insoluble  in  water  and  is 
only  very  slightly  soluble  in  acetic  acid,  but  is  easily  decomposed  by  strongly 
dissociated  acids,  so  that  the  precipitation  is  incomplete  in  neutral  solutions  of 
nickel  chloride,  sulphate  or  nitrate.  If,  however,  the  free  acid  formed  is  neutral- 

.  f.  ang.  Chem.,  20,  1844. 


288  NICKEL 

ized  with  sodium,  potassium  or  ammonium  hydroxides  or  by  addition  of  the  ace- 
tate salts  of  these  bases,  nickel  will  be  completely  precipitated,  not  even  a  trace 
being  found  in  the  filtrate. 

"  The  quantitative  determination  of  nickel  in  the  presence  of  other  metals 
is  a  simple  operation.  The  nickel  should  be  in  the  form  of  a  convenient  salt. 

"  The  concentration  of  the  solution  does  not  matter;  the  precipitation  can 
take  place  either  in  a  solution  of  the  greatest  concentration,  or  in  a  very  dilute 
solution.  The  reaction  is  not  hindered  by  the  presence  of  ammonium  salts." 

Iron,  aluminum,  chromium,  cobalt,  manganese  and  zinc  do  not  interfere. 
Theoretically  4  parts  of  dimethyl glyoxime,  added  as  a  1%  alcoholic  solution, 
are  necessary;  a  certain  excess  does  no  harm  provided  the  alcohol  volume  does 
not  exceed  more  than  half  that  of  the  water  solution  containing  the  nickel  salt, 
as  alcohol  has  a  solvent  action  on  the  oxime.  The  compound  is  very  stable  and 
volatilizes  undecomposed  at  250°  C. 

An  excess  of  ammonium  hydroxide  is  also  to  be  avoided  in  the  solution  in  which 
the  precipitation  takes  place. 

It  has  been  observed  that  the  precipitate  of  nickel  with  dimethylglyoxime 
may  be  safely  ignited  to  the  oxide  NiO  without  loss,  if  the  filter  is  first  care- 
fully charred  without  allowing  it  to  take  fire,  then  gradually  heated  to  redness. 

Procedure.  Such  an  amount  of  the  sample  should  be  taken  that  the  nickel 
be  not  over  0.1  gram,  as  glyoxime  of  nickel  is  very  voluminous  and  a  larger  amount 
would  be  difficult  to  filter.  If  cobalt  is  present  it  should  not  exceed  0.1  gram 
in  the  sample  taken.1 

If  hydrogen  sulphide  has  been  used  to  precipitate  members  of  the  second 
group,  it  is  expelled  by  boiling  the  acid  solution  and  the  volume  brought  to  250  cc. 

One  or  2  grams  of  tartaric  acid  are  added  to  prevent  the  precipitation  of 
the  hydroxides  of  iron,  aluminum  and  chromium  by  ammonium  hydroxide 
(this  treatment  is  omitted  if  these  are  absent),  and  5  to  10  cc.  of  a  10%  solu- 
tion of  ammonium  chloride  added  to  keep  zinc  and  manganese  in  solution,  should 
they  be  present.  Ammonium  hydroxide  is  now  added  until  the  solution  is  slightly 
alkaline.  If  a  precipitate  forms,  ammonium  chloride  is  added  to  clear  the 
solution,  followed  by  ammonium  hydroxide  to  neutralize  the  acid.  The  solu- 
tion should  remain  clear  after  this  treatment,  otherwise  the  ammonium  chloride 
is  added  in  solution  or  as  salt  until  the  solution  of  the  sample  will  remain  clear. 
It  is  then  heated  to  nearly  boiling  and  the  alcoholic  solution  of  dimethylglyoxime 
added  until  the  reagent  is  approximately  seven  times,  by  weight,  the  weight  of 
nickel  present.  Ammonium  hydroxide  is  now  added  until  the  solution  has  a  dis- 
tinct odor  of  this  reagent.  The  precipitation  of  the  scarlet  red  nickel  salt  is  hast- 
ened by  stirring.  It  is  advisable  to  place  the  mixture  on  the  steam  bath  for 
fifteen  to  twenty  minutes  to  allow  the  reaction  to  go  to  completion  before  filter- 
ing. The  precipitate  is  filtered  off,  into  a  platinum  sponge  Gooch  crucible,  some- 
times known  as  a  Neubauer  Gooch  crucible.  (Other  forms  of  Gooch  crucible 
are  used  for  this  purpose,  but  the  Neubauer  crucible  has  been  found  to  be  most 
satisfactory.)  The  precipitate  is  dried  for  about  two  hours  at  110  to  120°  C. 
and  weighed  as  C8HHN404Ni,  which  contains  20.32%  Ni. 

Weight  of  precipitate  multiplied  by  0.2032  =  weight  of  nickel. 

1  If  the  sample  contains  more  than  0.1  gram  of  cobalt,  a  large  excess  of  ammo- 
nium hydroxide  and  dimethylglyoxime  is  necessary  to  prevent  its  precipitation, 
hence  it  is  advisable  to  take  such  weights  of  samples  that  the  cobalt  content  will  be  less 
than  this  weight. 


NICKEL  289 

In  place  of  a  H«och  crucible  a  tared  filter  paper  may  be  used.  It  must  be  remem- 
bered, however,  that  a  blank  filter  paper  of  the  same  kind  as  used  for  the  precipitate 
must  be  used  as  a  counterbalance,  after  treating  in  exactly  the  same  manner  as  the 
one  containing  the  precipitate.  This  is  necessary  because  it  has  been  found  that  filter 
paper  loses  weight  during  washing  and  drying. 

Precipitation  of  Nickel  by  Electrolysis l 

This  precipitation  is  conducted  in  exactly  the  same  manner  as  the  one 
described  under  Cobalt  for  the  Precipitation  of  Cobalt  by  Electrolysis,  and 
requires  that  the  same  precautions  be  exercised  in  the  practice  of  the  method. 

In  the  presence  of  cobalt  the  two  elements  may  be  determined  together 
by  electrolysis  as  described  below  and  the  deposited  metal  redissolved  and  the 
two  elements  separated  by  one  of  the  methods  given  under  Cobalt  or  Nickel. 

Procedure.  After  the  sample  has  been  brought  into  solution  by  one  of  the 
methods  outlined  under  Preparation  and  Solution  of  the  Sample,  the  solution 
is  evaporated  with  20  cc.  of  1  :  1  sulphuric  acid  for  every  gram  of  metal  in  the 
sample.  The  evaporation  is  continued  until  the  solution  has  fumed  strongly 
for  ten  minutes.  Cool  carefully  and  dilute  with  20  cc.  of  water.  Heat  the  solu- 
tion to  nearly  boiling  and  pass  hydrogen  sulphide  for  one  hour  to  precipitate 
members  of  the  second  group.  This  long  treatment  is  necessary  to  insure  com- 
plete precipitation  of  arsenic.  Filter  and  boil  to  expel  hydrogen  sulphide.  Add 
5  cc.  nitric  acid  to  insure  oxidation  of  iron  compounds  to  the  ferric  state  and  add 
ammonium  hydroxide  until  just  slightly  alkaline.  Filter  off  the  ferric  hydroxide 
and  wash  with  water  containing  a  small  quantity  of  ammonium  hydroxide.  To 
recover  occluded  nickel  dissolve  the  precipitate  in  hydrochloric  acid  and  repre- 
cipitate  the  iron  with  addition  of  a  little  hydrogen  peroxide.  Combine  the 
filtrates.  Evaporate  to  about  250  cc.  and  add  50  cc.  of  strong  ammonium 
hydroxide  and  electrolyze  as  described  under  Cobalt,  page  144. 

The  increase  in  weight  of  the  electrode  is  the  weight  of  cobalt  and  nickel 
in  the  sample.  The  percentage  of  cobalt  and  nickel  in  the  sample  is  found  by 
multiplying  the  increase  in  weight  of  the  electrode  by  100  and  dividing  by  the 
weight  of  the  sample. 

NOTE.  The  deposition  of  cobalt  and  nickel  by  the  above  method  has  been  found 
to  be  the  most  accurate  of  the  electrolytic  methods.  In  the  solutions  containing  the 
organic  acids  there  is  always  more  or  less  carbide  deposited  on  the  cathode  with  the 
metal.  This  causes  high  results. 

Nickel  in  Metallic  Nickel 

This  determination  may  be  made  in  the  manner  described  under  Precipitation 
of  Nickel  by  Electrolysis,  separating  cobalt  before  or  after  the  electrolysis  or  by 
the  method  described  under  Precipitation  of  Nickel  by  Dimethylglyoxime.  The 
latter  method  is  recommended. 

Nickel  in  Cobalt  and  Cobalt  Oxide 

The  dimethylglyoxime  precipitation  is  used  in  combination  with  the  elec- 
trolytic precipitation.  See  chapter  on  Cobalt. 

1 W.  J.  Marsh,  J.  Phys.  Chem.,  18,  705-16,  1914. 


290  NICKEL 

VOLUMETRIC  DETERMINATION  OF  NIcKEL 
Determination  of  Nickel  in  Alloys 

This  method,  as  described  by  S.  W.  Parr  and  J.  M.  Lindgren,1  consists  of 
fi  modification  of  the  dimethylgloxime  method.  The  precipitation  takes  place 
in  the  usual  manner  and  the  precipitate  is  dissolved  in  sulphuric  acid  and  the 
excess  titrated  with  a  standard  solution  of  potassium  hydroxide. 

Procedure.  The  alloy  is  dissolved  in  nitric  or  hydrochloric  acids  and  if  iron, 
aluminum  or  chromium  are  present  twice  their  weight  of  tartaric  acid  is  added 
to  prevent  their  precipitation.  If  chromium  is  present  ammonium  chloride  is 
also  added.  If  manganese  or  zinc  is  present  hydrochloric  acid  should  be  used  and 
paost  of  the  free  acid  evaporated.  Add  a  few  cc.  of  hydrogen  peroxide  to  oxidize 
any  ferrous  iron  to  the  ferric  state.  Dilute  to  300  or  400  cc.  and  neutralize  the 
free  acid  by  sodium  acetate.  Heat  the  solution  to  nearly  boiling  and  add  five  times 
as  much  dimethylglyoxime,  in  1%  alcoholic  solution,  as  the  nickel  present.  Then 
completely  neutralize  with  ammonium  hydroxide,  using  a  very  slight  excess  (or 
the  solution  may  be  neutralized  with  sodium  acetate).  Heat  until  all  the  nickel 
is  precipitated.  Filter  and  wash.  Place  the  precipitate  and  filter  in  a  beaker, 
add  an  excess  of  0.05N  sulphuric  acid,  dilute  to  200  cc.,  heat  until  solution  is 
complete  and  titrate  back  with  0.1N  potassium  hydroxide  solution,  taking  the 
first  faint  yellowish  tinge  as  the  end-point.  The  solutions  are  standardized 
against  pure  nickel. 

NOTE.  Cobalt  should  not  exceed  0.1  gram  per  100  cc.  and  an  excess  should  be 
used  of  the  dimethylglyoxime. 

Nickel  in  Nickel-plating  Solutions 

In  most  cases  it  is  quite  unnecessary  to  separate  the  cobalt  from  the  nickel 
in  making  this  determination  and,  as  the  principal  impurity  is  usually  iron,  the 
best  practice  is  to  follow  the  method  given  under  Precipitation  of  Cobalt  by 
E'ectrolysis,  page  144. 

If  chlorides  or  organic  matter  are  present  in  the  solution  the  preparation 
of  the  solution  for  electrolysis  is  accomplished  in  the  following  manner: 

From  the  well-stirred  solution  in  the  plating  tank,  withdraw  about  200  cc. 
and  place  in  a  small  beaker.  Prepare  a  100-cc.  burette  by  thoroughly  clean- 
ing it  with  the  sulphuric  acid  and  potassium  bichromate  mixture  and  distilled 
water.  Wash  finally  with  a  few  cc.  of  the  nickel  solution  and  fill  the  burette  with 
the  solution  from  the  plating  tank. 

Run  66.7  cc.  into  an  evaporating  dish  and  add  2  cc.  1:1  sulphuric  acid. 
Evaporate  to  fumes  of  sulphur  trioxide  and  allow  to  fume  strongly  for  ten  min- 
utes. Dissolve  in  a  little  water.  Dilute  to  200  cc.  carefully,  neutralize  with  a 
solution  of  ammonium  hydroxide  and  add  50  cc.  of  strong  ammonium  hydroxide 
and  electrolyze.  (See  Precipitation  of  Cobalt  by  Electrolysis.) 

The  increase  in  weight  of  the  cathode  in  grams  multiplied  by  2  gives  the 
weight  in  ounces  of  nickel  in  one  United  States  gallon  of  the  plating  solution. 

1  S.  W.  Parr  and  J.  M.  Lindgren,  Trans.  Am.  Brass  Founders'  Assoc.,  6,  120-9. 


NITROGEN 

WILFRED  W.  SCOTT 

Element.  N2,  af.wtf.  14.01;  D.  (air)  0.9674;  m.p.  -210°;  b.p.  -195.5°  C.; 
oxides,  N2O,  N2O2,  N2O3,  N2O4,  N2O5. 

Ammonia.  NH3,  m.w.  17.03;  D.  (air)  O.5971;  sp.gr.  liquid  0.6234;  m.p. 
-77.3°;  b.p.  -38.5°  C.  Crit.  temp.  130°;  liquid  at  0°  with  4.2  atmospheres 
pressure.  Commercial  28%  NH3,  sp.firr.  0.90. 

Nitric  Acid.  HNO3,  m.w.,  63.02;  sp.^r.  1.53;  m.p.  -41.3;  6.p.  86°  C. 
Boiling-point  of  commercial  95%  acid  is  a  little  above  86°,  6ut  gradually 
rises  to  126°  and  Me  strength  of  acid  falls  to  68.9%,  sp.gr.  is  then  1.42. 
The  acid  now  remains  constant,  the  distillate  being  of  the  same  strength. 

DETECTION 

Element.  Organic  Nitrogen.  Organic  matter  is  decomposed  by  heating 
in  a  Kjeldahl  flask  with  concentrated  sulphuric  acid  as  described  under  prepara- 
tion and  solution  of  the  sample.  Ammonia  may  now  be  liberated  from  the  sul- 
phate and  so  detected. 

Nitrogen  in  Gas.  Recognized  by  its  inertness  towards  the  reagents  used 
in  gas  analysis.  The  element  may  be  recognized  by  means  of  the  spectroscope. 

Ammonia.  Free  ammonia  is  readily  recognized  by  its  characteristic  odor. 
A  glass  rod  dipped  in  hydrochloric  acid  and  held  in  fumes  of  ammonia  produces 
a  white  cloud  of  ammonium  chloride,  NH4C1. 

Moist  red  litmus  paper  is  turned  blue  by  ammonia.  Upon  heating  the  paper 
the  red  color  is  restored,  upon  volatilization  of  ammonia  (distinction  from  fixed 
alkalies) . 

Nessler's  Test.1  Nessler's  reagent  added  to  a  solution  containing  ammonia, 
combined  or  free,  produces  a  brown  precipitate,  NHg2I  •  H20.  If  the  ammoniacal 
solution  is  sufficiently  dilute  a  yellow  or  reddish-brown  color  is  produced,  accord- 
ing to  the  amount  of  ammonia  present.  The  reaction  is  used  in  determining 
ammonia  in  water. 

Salts  of  ammonia  are  decomposed  by  heating  their  solutions  with  a  strong 
base  such  as  the  hydroxides  of  the  fixed  alkalies  or  the  alkaline  earths.  The 
odor  of  ammonia  may  now  be  detected. 

Nitric  Acid.  Ferrous  Sulphate  Test.  About  1  to  2  cc.  of  the  concentrated 
solution  of  the  substance  is  added  to  15  to  20  cc.  of  strong  sulphuric  acid  in  a 
test-tube.  After  cooling  the  mixture,  the  test-tube  is  inclined  and  an  equal 
volume  of  a  saturated  solution  of  ferrous  sulphate  is  allowed  to  flow  slowly  down 
over  the  surface  of  the  acid.  The  tube  is  now  held  upright  and  gently  tapped. 
In  the  presence  of  nitric  acid  a  brown  ring  forms  at  the  junction  of  the  two 
solutions. 

\  The  reagent  is  made  by  dissolving  20  grams  of  potassium  iodide  in  50  cc.  of  water, 
adding  32  grams  of  mercuric  iodide  and  diluting  to  200  cc.  To  this  is  added  a  solution 
of  potassium  hydroxide — 134  grams  KOH  per  260  cc.  H2O. 

291 


292 


NITROGEN 


The  test  for  nitrate  may  be  made  according  to  the  quantitative  procedure 
given  for  determining  of  nitric  acid  (see  later).  It  should  be  remembered  that 
ferrous  sulphate  should  be  present  in  excess,  otherwise  the  brown  color  is 
destroyed  by  the  free  nitric  acid.  Traces  of  nitric  acid  in  sulphuric  produce 
a  pink  color  with  the  sulphuric  acid  solution  of  ferrous  sulphate.  (See  Deter- 
mination of  Nitric  Acid— Ferrous  Sulphate  Method.) 

Ferro-  and  ferricyanides,  chlorates,  bromides  and  bromates,  iodides  and 
iodates,  chromates  and  permanganates  interfere. 

Diphenylamine  Tests  for  Nitrates.  (C6H5)2NH  dissolved  in  sulphuric  acid 
is  added  to  2  or  3  cc.  of  the  substance  in  solution  on  a  watch-glass.  Upon  gently 
warming  a  blue  color  is  produced  in  presence  of  nitrates.  Nitric  acid  in  sul- 
phuric acid  is  detected  by  placing  a  crystal  of  diphenylamine  in  3  or  4  cc.  of  the 
acid  and  gently  warming.  Cl',  Clv,  Brv,  F,  Mn™,  Cr™,  Se™,  Fe'"  interfere. 

Copper  placed  in  a  solution  containing  nitric  acid  liberates  brown  fumes. 

Phenolsulphonic  Acid  Test.     See  chapter  on  Water  Analysis. 

Detection  of  Nitrous  Acid.  Acetic  Acid  Test.  Acetic  acid  added  to  a 
nitrite  in  a  test-tube  (inclined  as  directed  in  the  nitric  acid  test  with  ferrous 
sulphate),  produces  a  brown  ring.  Nitrates  do  not  give  this.  If  potassium  iodide 
is  present  in  the  solution,  free  iodine  is  liberated.  The  free  iodine  is  absorbed 
by  chloroform,  carbon  tetrachloride  or  disulphide,  these  reagents  being  colored 
pink.  Starch  solution  is  colored  blue. 

Nitrous  acid  reduces  iodic  acid  to  iodine.  The  iodine  is  then  detected  with 
starch,  or  by  carbon  disulphide,  or  carbon  tetrachloride. 

Potassium  Permanganate  Test.  A  solution  of  the  reagent  acidified  with  sul- 
phuric acid  is  decolorized  by  nitrous  acid  or  nitrite.  The  test  serves  to  detect 
nitrous  acid  in  nitric  acid.  Other  reducing  substances  must  be  absent. 

ESTIMATION 

Occurrence.  Element.  Free  in  air  to  extent  of  78%+  by  volume  and 
76%  -  by  weight. 

Air  weight  of  1  liter  =  1.293  grams.    With  oxygen  as  32,  air  =28.95. 

COMPOSITION  OF  AIR.     ON  THE  BASIS  OF  1000  LITERS  OF  ATMOSPHERE 


Element. 

Liters  per 
10001. 

Weight  p-r 
1000  1.  gran.s 

Per  cent  by 
Vol. 

Per  cent  by 
Wt. 

Nitrogen  

780  3 

975  .  80 

78    1 

75.47  — 

Oxygen 

209  9 

299  84 

21  0 

23  19  — 

Argon. 

9  4 

16  76 

0  9 

1  296  + 

Carbon  dioxide 

0  3 

0  59 

0  04 

0  045 

Hydrogen 

0  1 

0  01 

Neon        

0  015 

0  01339 

Helium  

0  0015 

0  00027 

,_ 

Krypton  

0.00005 

0.00018 

Xenon  

0.000006 

0.00003 

Water-saturated  air  contains  2.4  grams  H20  at  -10°;  4.9  grams  at  0°;  17.2 
grams  at  20°  and  55  grams  H20  at  40°  C.  Ordinarily  50  to  70%  of  this  is  present. 

Nitrogen  is  found  combined  in  nature  as  potassium  nitrate  (saltpeter),  KNOsj 
sodium  nitrate  (Chili  saltpeter),  NaN03,  and  to  a  less  extent  as  calcium  nitrate, 


NITROGEN"  293 

Ca(N03)2.  It  occurs  in  plants  and  in  animals,  in  the  substances  proteids,  blood, 
muscle,  nerve  substance,  in  fossil  plants  (coal),  in  guano,  ammonia  and  ammo- 
nium salts. 

Free  nitrogen  is  estimated  in  the  complete  analysis  of  gas  mixtures.  In 
illuminating  gas  the  other  constituents  are  removed  by  combustion  and  absorp- 
tion and  the  residual  gas  measured  as  nitrogen. 

Total  nitrogen  in  organic  substances  is  best  determined  by  decomposition 
of  the  materials  with  sulphuric  acid  as  described  later,  and  estimating  the  nitro- 
gen from  the  ammonia  formed. 

Combined  nitrogen  in  the  form  of  ammonia  and  nitric  acid  specially  concerns 
the  analyst.  In  the  evaluation  of  fertilizers,  feedstuffs,  hay,  fodders,  grain, 
etc.,  the  nitrogen  is  estimated  after  conversion  to  ammonia.  Ammonia,  nitrates 
and  nitrites  may  be  required  in  an  analysis  of  sewages,  water,  and  soils.  Nitric 
acid  is  determined  in  Chili  saltpeter,  in  the  evaluation  of  this  material  for  the 
manufacture  of  nitric  acid  or  a  fertilizer,  the  nitrate  being  reduced  to  ammonia 
and  thus  estimated. 

We  will  take  up  a  few  of  the  characteristic  substances  in  which  nitrogen 
estimations  are  required,  e.g.,  in  organic  substances  as  proteids,  in  soils  and 
fertilizers;  in  ammonium  salts,  nitrates,  and  nitrites,  free  ammonia  in  ammonia- 
cal  liquors,  nitric  acid  in  the  evaluation  of  the  commercial  acid  and  in  mixed  acids. 

In  general  nitrogen  is  more  accurately  and  easily  measured  as  ammonia,  to 
which  form  it  is  converted  by  reduction  methods.  Large  amounts  are  determined 
by  titration,  whereas  small  amounts  are  estimated  colorimetrically.  Nitric 
acid  and  nitrates  may  be  determined  by  direct  titration  by  the  Ferrous  Sulphate 
Method  outlined  later.  The  procedure  is  of  value  in  estimation  of  nitrates  in 
mixed  acids.  The  nitrometer  method  for  determining  nitrates  (including 
nitrites),  and  the  free  acid  in  mixed  acids,  is  generally  used  by  manufacturers 
of  explosives. 

Preparation  of  the  Sample 

It  will  be  recalled  that  compounds  of  ammonia  and  of  nitric  acid  are  generally 
soluble  in  water.  All  nitrogen  compounds,  however,  are  not  included.  Among 
those  which  are  not  readily  soluble  the  following  deserve  mention:  compounds 
of  nitrogen  in  many  organic  substances;  nitrogen  bromophosphide,  NPBr2; 
nitrogen  selenide,  NSe;  nitrogen  sulphide,  N4S4;  nitrogen  pentasulphide,  N2S5; 
ammonium  antimonate,  NH4Sb03-2H20;  ammonium  iodate,  HN4I03  (2.6  grams 
per  100  cc.  H20);  ammonium  chlorplatinate,  (NH4)2PtCl6  (0.67  gram);  ammo- 
nium chloriridate,  (NH4)2IrCl6  (0.7  gram);  ammonium  oxalate,  (NH4)2C204-H20 
(4.2  grams);  ammonium  phosphomolybdate,  (NH4)3P04-12Mo03  (0.03  gram); 
nitron  nitrate,  C20Hi6N4  •  HN03. 

Organic  Substances 

By  oxidation  of  nitrogenous  organic  substances  with  concentrated  sulphuric 
acid,  containing  mercuric  oxide,  or  potassium  permanganate,  the  organic  matter  is 
destroyed  and  the  nitrogen  is  changed  to  ammonia,  which  is  held  by  the  sul- 
phuric acid  as-  sulphate.  Nitrates  are  reduced  by  addition  of  salicylic  acid, 
zinc  dust,  etc.,  previous  to  the  oxidation  process.  Practically  all  the  procedures 
are  based  on  the  Kjeldahl  method  of  acid  digestion.  The  modification,  com- 
monly known  as  the  Kjeldahl-Gunning-Arnold  Method,  is  as  follows: 


294 


NITROGEN 


Method  in  Absence  of  Nitrates.  Weight  of  Sample.  Fertilizers  0.7  to 
3.5  grams.  Soils  7  to  14  grams.  Meat  and  meat  products  2  grams.  Milk  5 
grams.  The  amount  of  the  substance  to  be  taken  should  be  governed  by  its 
nitrogen  content. l 

Acid  Digestion.2  The  material  is  placed  in  a  Kjeldahl  flask  of  about  550  cc. 
capacity.  Approximately  0.7  gram  of  mercuric  oxide  or  an  equivalent  amount 

of  metallic  mercury  together  with  10 
grams  of  powdered  potassium  sulphate 
followed  by  20  to  30  cc.  of  concentrated 
sulphuric  acid  (sp.gr.  1.84)  are  added. 
The  flask  is  placed  in  an  inclined  posi- 
tion, resting  in  a  large  circular  opening 
of  an  asbestos  board.  The  flask  is  heated 
with  a  small  flame  until  the  frothing  has 
ceased.  (A  piece  of  paraffin  may  be 
added  to  prevent  extreme  frothing.) 
The  heat  is  then  raised  and  the  acid 
brought  to  brisk  boiling,  the  heating 
being  continued  until  the  solution  be- 
comes a  pale  straw  color,  or  practically 
water  white.  (In  case  of  leather,  scrap, 
cheese,  milk  products,  etc.,  a  more  pro- 
longed digestion  may  be  required.  With 
a  good  flame  from  one-half  to  one  hour 
of  acid  digestion  is  generally  sufficient 
to  completely  decompose  the  material.) 
The  flask  is  now  removed  from  the  flame 
and  after  cooling  the  solution  is  diluted 
with  about  200  cc.  of  water  and  a  few 
pieces  of  granulated  zinc  added  to  pre- 
vent "  bumping  "  (50  mg.  or  so  of  No. 
80  granulated  zinc).  The  solution  is 
now  alkalized  strongly  by  addition  of  a 
mixture  of  sodium  hydroxide  and  sodium  sulphide  solution  (about  75  cc.  of  a 
mixture  containing  25  grams  of  NaOH  and  1  gram  Na2S).  Phenolphthalein 
indicator  added  to  the  solution  will  show  when  the  acid  is  neutralized.  The 
flask  is  connected  by  means  of  a  Hopkins  distillation  tube  (Fig.  53)  to  a  con- 
denser and  about  150  cc.  of  the  solution  distilled  into  an  excess  of  standard  sul- 
phuric acid  and  the  excess  of  the  acid  determined  by  titration  with  standard 
sodium  hydroxide.  (Methyl  red  indicator.) 

The  ammonia  may  be  absorbed  in  a  saturated  solution  of  boric  acid  and 
titrated  directly  with  standard  acid.  (Methyl  orange  indicator.)3 

One  cc.  N/10  H2S04=  0.001704  gram  NH3. 

1  See  data  of  approximate  nitrogen  content  in  certain  nitrogenous  substances,  Jour. 
Ind.  Eng.  Chem.,  7,  357,  1915. 

2  Fig.  50  shows  a  compact  apparatus  with  several  sets  of  flasks  and  condensers, 
which  enable  half  a  dozen  or  more  determinations  to  be  made  at  one  time. 

» L.  W.  Winkler,  Z.  angew.  Chem.,  27,  1,  630-2,  191 4.  E.  Bernard,  ibid.,  27,  1, 
664,  1914. 


FIG.  50. 
Apparatus  for  Determining  Nitrogen. 


NITROGEN  295 

In  Presence  of  Nitrates.  The  procedure  differs  from  the  former  in  the 
preliminary  treatment  to  reduce  the  nitrates.  The  material  in  the  flask  is 
treated  with  a  mixture  of  30  to  35  cc.  of  strong  sulphuric  acid  containing  1  gram 
of  salicylic  acid  and  the  mixture  shaken  and  allowed  to  stand  for  five  to  ten 
minutes  with  frequent  agitation.  About  5  grams  of  sodium  thiosulphate  are  now 
added  and  the  solution  heated  for  five  minutes.  After  cooling,  mercuric  oxide 
or  metallic  mercury  and  potassium  sulphate  are  added,  and  the  solution  treated 
as  directed  above. 

NOTES.  Mercuric  oxide  or  metallic  mercury  are  added  as  a  catalyzer  to  assist  the 
oxidation  of  the  organic  matter.  The  digestion  process  is  shortened  considerably 
by  its  use.  In  place  of  mercuric  oxide  or  the  metal,  copper  sulphate  may  be  used. 
In  this  case  the  addition  of  sodium  sulphide  is  omitted.  Copper  sulphate  acts  as  an 
indicator  in  the  neutralization  of  the  sample  with  caustic. 

Potassium  sulphide  is  added  to  remove  the  mercury  from  the  solution  and  prevent 
the  formation  of  mercur-ammonium  compounds,  which  are  not  completely  decomposed 
by  sodium  hydroxide. 

A  blank  determination  should  be  made  on  the  reagents  used  with  sugar  as  the 
organic  substance. 

Soils.  Available  Nitrates.  Five  hundred  to  1000  grams  of  the  air-dried 
soil  is  extracted  with  1  to  2  liters  of  water  containing  10  to  20  grams  of  dextrose. 
Fifteen  to  twenty  hours  of  leaching  is  sufficient.  An  aliquot  portion  is  taken 
for  analysis. 

Ammonium  Salts.  The  sample  is  placed  in  the  distillation  flask  with  splash 
bulb  as  described  in  the  modified  Kjeldahl  procedure  for  organic  substances, 
and  the  material  decomposed  with  ammonia-free  caustic  solution.  The  ammonia 
is  distilled  into  an  excess  of  standard  acid  or  a  saturated  solution  of  boric  acid 
(neutral  to  methyl  orange),  and  the  ammonia  determined  as  usual,  either  by 
titration  of  the  excess  of  acid,  or  by  direct  titration  with  acid,  according  to  the 
absorbent  used. 

Nitrates.  The  sample,  broken  down  as  fine  as  possible,  is  dissolved  in 
water,  decomposed  with  Devarda  alloy  and  distilled  as  described  by  the  modi- 
fied Devarda  methods  given  later. 

Nitrites.  The  material,  dissolved  in  water,  is  titrated  with  standard  perman- 
ganate solution  according  to  the  procedure  described  later. 

Mixtures  of  Ammonium  Salts,  Nitrates,  and  Nitrites.  Ammonia  is 
determined  by  distillation  with  caustic  as  usual.  The  nitrite  is  titrated  with 
permanganate.  Total  nitrogen  is  determined  by  the  modified  Devarda  methods. 
Nitric  acid  is  now  estimated  by  difference,  e.g.,  from  the  total  nitrogen  is  deducted 
the  nitrogen  due  to  ammonia  together  with  the  nitrogen  of  the  nitrite  and  the  dif- 
ference calculated  to  the  nitrate  desired.  The  nitrate  may  be  determined  in  pres- 
ence of  nitrite  and  ammonia  by  direct  titration  with  ferrous  sulphate.  The 
detailed  procedures  may  be  found  under  the  Volumetric  Methods. 

Nitric  Acid  in  Mixed  Acid.  This  is  best  determined  by  the  ferrous  sulphate 
method  for  nitric  acid.  The  nitrometer  method  is  also  excellent. 

SEPARATIONS 

Ammonia.  No  special  separation  need  be  considered  in  the  determination 
of  ammonia.  The  general  method  has  already  been  mentioned  by  which 
ammonia  is  liberated  from  its  salts  by  a  strong  base  and  volatilized  by  heat. 
This  effects  a  separation  from  practically  all  substances. 


296  NITROGEN 

Nitric  Acid.  The  compound  may  be  isolated  as  the  fairly  insoluble,  crys- 
talline nitron  nitrate,  C2oHi6N4-HN03  by  the  following  procedure. 

Such  an  amount  of  the  substance  is  taken  as  will  contain  about  0.1  gram 
nitric  acid,  and  dissolved  in  about  100  cc.  of  water  with  addition  of  10  drops 
of  dilute  sulphuric  acid.  The  solution  is  heated  nearly  to  boiling  and  about 
12  cc.  of  nitron  acetate  solution  added  (10  grams  of  nitron  in  100  cc.  of  5%  acetic 
acid).2  The  solution  is  cooled  and  placed  in  an  ice  pack  for  about  two  hours, 
and  the  compound  then  transferred  to  a  Gooch  or  Munroe  crucible  (weighed 
crucible  if  gravimetric  method  is  to  be  followed),  and  after  draining,  it  is  washed 
with  about  10  to  12  cc.  of  ice-water  added  in  small  portions.  The  nitrate  may 
now  be  determined  gravimetrically  by  drying  the  precipitate  to  constant  weight 
at  110°  C.,  16.53%  of  the  material  being  due  to  N03. 

The  base  diphenyl-endo-anilo-hydro-triazole  (nitron)  also  precipitates  the 
following  acids:  nitrous,  chromic,  chloric,  perchloric,  hydrobromic,  hydriodic, 
hydroferro-  and  hydroferricyanic,  oxalic,  picric  and  thiocyanic  acids.  Hence 
these  must  be  absent  from  the  solution  if  precipitation  of  nitric  acid  is  desired  for 
quantitative  estimation. 

Removal  of  Nitrous  Acid.  Finely  powdered  hydrazine  sulphate  is  dropped 
into  the  concentrated  solution.  (0.2  gram  substance  per  5  or  6  cc.) 

Chromic  acid  is  reduced  by  addition  of  hydrazine  sulphate. 

Hydrobromic  acid  is  decomposed  by  chlorine  water  added  drop  by  drop 
to  the  neutral  solution,  which  is  then  boiled  until  the  yellow  color  has  dis- 
appeared. 

Hydriodic  acid  is  removed  by  adding  an  excess  of  potassium  iodate  to 
the  neutral  solution  and  boiling  until  the  iodine  is  expelled. 


PROCEDURES   FOR  THE  DETERMINATION   OF  COMBINED 

NITROGEN 

Ammonia 

The  volumetric  procedures  for  determination  of  ammonia  are  preferred  to  the 
gravimetric  on  account  of  their  accuracy  and  general  applicability.  The  fol- 
lowing gravimetric  method  may  occasionally  be  of  use: 

Gravimetric    Determination    of    Ammonia    by    Precipitation    as 
Ammonium  Platinochloride, 


Ammonia  in  ammonium  chloride  may  be  determined  gravimetrically  by  pre- 
cipitation with  chlorplatinic  acid.  The  method  is  the  reciprocal  of  the  one  for 
determining  platinum. 

Procedure.  The  aqueous  solution  of  the  ammonium  salt  is  treated  with  an 
excess  of  chlorplatinic  acid  and  evaporated  on  the  steam  bath  to  dryness.  The 
residue  is  taken  up  with  absolute  alcohol,  filtered  through  a  weighed  Gooch  cru- 
cible, and  washed  with  alcohol.  The  residue  may  now  be  dried  at  130°  C.  and 
weighed  as  (NH4)2PtCl«,  or  it  may  be  gently  ignited  in  the  covered  crucible  until 

1  M.  Busch,  Ber.,  38,  861  (1905),  Treadwell  and  Hall,  "  Analytical  Chemistry." 

2  Keep  nitron  reagent  in  a  dark-colored  bottle. 


NITROGEN  297 

ammonium  chloride  has  been  largely  expelled  and  then  more  strongly  with  free 
access  of  air.  The  residue  of  metallic  platinum  is  weighed.  If  the  ignition 
method  is  to  be  followed,  the  ammonium  platinic  chloride  may  be  filtered  into  a 
small  filter,  the  paper  with  the  washed  precipitate  placed  in  a  porcelain  crucible 
and  then  gently  heated  until  the  paper  is  charred  (crucible  being  covered)  and  then 
more  strongly  with  free  access  of  air  until  the  carbon  has  been  destroyed. 

Factors.!     (NH4)2PtCl6X 0.2400  =NH4C1,    or    0.08095  =NH4,    or    X0.0767  = 
NH3.    PtXO.5453  =NH4C1,  or  X0.1839  =NH4,  or  X0.1736  =NH3. 


VOLUMETRIC   METHODS   FOR  DETERMINATION   OF 

AMMONIA 

Two  conditions  are  considered: 

A .  Estimation  of  free  ammonia  in  solution. 

B.  Determination  of  ammonia  in  its  salts — combined  ammonia. 

Analysis  of  Aqua  Ammonia 

Provided  no  other  basic  constituent  is  present,  free  ammonia  in  solution 
is  best  determined  by  direct  titration  with  an  acid  in  presence  of  methyl  orange 
or  methyl  red  as  indicator. 

Procedure.  About  10  grams  of  the  solution  in  a  weighing  bottle  with  glass 
stopper  is  introduced  into  an  800-cc.  Erlenmeyer  flask  containing  about  200  cc. 
of  water  and  sufficient  |  normal  sulphuric  acid  to  combine  with  the  ammonia 
and  about  10  cc.  in  excess.  The  flask  is  stoppered  and  warmed  gently.  This 
forces  out  the  stopper  in  the  weighing  bottle,  the  ammonia  combining  with 
the  acid.  Upon  thorough  mixing,  the  solution  is  cooled,  and  the  excess  of  acid 
is  titrated  with  half  normal  caustic. 

One  cc.  }  N.  H2S04  =0.0085  gram  NH3. 
Factor.    H2S04X0.3473  =NH3. 

NOTE.  The  aqua  ammonia  exposed  to  the  air  will  lose  ammonia,  hence  the  sample 
should  be  kept  stoppered.  This  loss  of  ammonia  is  quite  appreciable  in  strong 
ammoniacal  solutions. 

Determination  of  Combined  Ammonia.    Ammonium  Salts. 

Strong  bases  decompose  ammonium  salts,  liberating  ammonia.  This  may  be 
distilled  into  standard  acid  or  into  a  saturated  solution  of  boric  acid  (neutral  to 
methyl  orange)  and  titrated. 

Procedure.  About  1  gram  of  the  substance  is  placed  in  a  distillation  flask 
(see  Fig.  50)  and  excess  of  sodium  or  potassium  hydroxide  added  and  the 
ammonia  distilled  into  a  saturated  solution  of  boric  acid  or  an  excess  of  standard 
sulphuric  acid.  Ammonia  in  boric  acid  solution  may  be  titrated  directly  with 
standard  acid  (methyl  orange  or  methyl  red  indicator)  or  in  case  a  mineral  acid 

1  Factors  recpmmended  by  Treadwell  and  Hall,  "  Analytical  Chemistry,"  2,  John 
Wiley  &  Sons. " 


298  NITROGEN 

was  used  to  absorb  the  ammonia,  the  excess  of  acid  is  titrated  with  standard 
caustic  solution. 

One  cc.  half  normal  sulphuric  acid  =0.0085  gram  NH,. 

One  cc.  normal  acid  =0.01703  gram  NH3. 
Factors.    H2S04X  0.3473  =NH3    and    NH3X  2.8792  =H2S04. 


ANALYSIS   OF  AMMONIACAL  LIQUOR 

The  crude  liquor  by-product  from  coal  gas  in  addition  to  ammonia  contains 
hydrogen  sulphide,  carbon  dioxide,  hydrochloric  acid,  sulphuric  acid,  combined 
with  ammonia,  also  sulphites,  thiosulphates,  thiocyanates,  cyanides,  ferrocyanides, 
phenols. 

Determination  of  Ammonia 

Volatile  Ammonia.  This  is  determined  by  distillation  of  the  ammonia  into 
an  excess  of  standard  sulphuric  acid  and  titrating  the  excess  of  acid.  With  the 
exception  that  caustic  soda  is  omitted  in  this  determination,  the  details  are  the 
same  as  those  for  total  ammonia  as  stated  in  the  next  paragraph. 

Total  Ammonia.  The  true  value  of  the  liquor  is  ascertained  by  its  total 
ammonia  content.  Ten  to  25  cc.  of  the  sample  is  diluted  to  about  250  cc.  in 
a  distilling  flask  with  a  potash  connecting  bulb,  as  previously  described,  20  cc. 
of  5%  sodium  hydroxide  are  added  and  about  150  cc.  of  solution  distilled  into  an 
excess  of  sulphuric  acid.  The  excess  is  then  titrated  according  to  the  standard 
procedure  for  ammonia. 

One  cc.  N.  H2S04  =0.01703  gram  NH3. 
Fixed  Ammonia  is  the  difference  between  the  total  and  the  volatile  ammonia. 

Carbon  Dioxide 

Ten  cc.  of  the  liquor  are  diluted  to  400  cc.  and  10  cc.  of  10%  ammoniacal 
calcium  chloride  added  and  the  mixture,  placed  in  a  flask  with  Bunsen  valve,  is 
digested  on  the  water  bath  for  two  hours.  The  precipitated  calcium  carbonate 
is  washed,  placed  in  a  flask  and  an  excess  of  N/2  HC1  added  and  the  excess  acid 
titrated  with  N/2  NaOH. 

N/2  HC1=  0.011  gram  C02. 

Hydrochloric  Acid 

Ten  cc.  of  the  liquor  is  diluted  to  150  cc.  and  boiled  to  remove  ammonia. 
Now  hydrogen  peroxide  is  added  to  oxidize  organic  matter,  etc.,  the  mixture  being 
boiled  to  remove  the  excess  of  the  peroxide.  Chlorine  is  titrated  in  presence  of 
potassium  chromate  as  indicator  by  tenth  normal  silver  nitrate  after  neutraliz- 
ing with  dilute  nitric  acid. 

One  cc.  N/10  AgNO,  =0.00364  gram  HC1. 


NITROGEN  299 


Hydrogen  Sulphide 

To  10  cc.  of  the  liquor  are  added  an  excess  of  ammoniacal  zinc  chloride  or 
acetate,  the  mixture  diluted  to  about  80  cc.  and  warmed  to  40°.  After  settling 
for  half  an  hour  the  zinc  sulphide  is  filtered  off  and  washed  with  warm  water 
(40  to  50°);  the  precipitate  is  washed  from  the  filter  into  an  excess  of  N/10 
iodine  solution,  the  srlphide  clinging  to  the  paper  washed  into  the  main  solu- 
tion with  hydrochloric  acid.  The  mixture  is  acidified  and  the  excess  iodine 
titrated  with  N/10  sodium  thiosulphate. 

One  cc.  N/10  I  =0.0017  gram  H2S    or    0.0016  gram  S. 

Sulphuric  Acid 

250  cc.  of  the  liquor  is  concentrated  to  10  cc.,  2  cc.  of  concentrated  hydro- 
chloric added  and  the  mixture  heated  to  decompose  any  thiosulphate,  sulphide 
or  sulphite  present.  The  concentrate  is  extracted  with  water,  filtered  and  made 
to  250  cc.  The  sulphuric  acid  is  now  precipitated  in  an  aliquot  portion  with 
barium  chloride. 

BaS04X0.4202  =H2S04,     or     X0.1374  =S  present  as  H2S04. 

Total  Sulphur.  Fifty  cc.  of  the  liquor  is  run  by  means  of  a  pipette  into 
a  deep  beaker  (250  cc.  capacity),  containing  an  excess  of  bromine  covered  by 
dilute  hydrochloric  acid.  The  mixture  is  evaporated  to  dryness  on  the  steam 
bath  and  the  residue  taken  up  with  water  and  diluted  to  250  cc.  Sulphur  is 
now  precipitated  as  barium  sulphate  as  usual,  preferably  on  an  aliquot  portion. 

For  a  more  complete  analysis  of  crude  liquor  determining  sulphite,  thio- 
sulphate, thiocyanate,  hydrocyanic  acid,  ferrocyanic  acid,  and  phenols  the  analyst 
is  referred  to  Lunge,  "  Technical  Methods  of  Chemical  Analysis,"  Part  II,  Vol.  II, 
D.  Van  Nostrand  Co. 

Determination  of  Traces  of  Ammonia 

The  determination  of  traces  of  ammonia  is  best  accomplished  by  the  colori- 
metric  method  with  Nessler's  reagent.  Details  of  the  procedure  are  given  in  the 
chapter  on  water  analysis. 


NITRIC  ACID.     NITRATES 

The  alkalimetric  method  for  determining  free  nitric  acid,  and  the  complete 
analysis  of  the  commercial  product  are  given  in  the  chapter  on  Acids.  Special 
procedures  for  determining  the  combined  acid  are  herein  given. 

Gravimetric  Method  for  Determining  Nitric  Acid  by  Precipitation 
as  Nitron  Nitrate,  C20Hi6  N4-HNO3 

As  in  case  of  ammonia  the  volumetric  methods  are  generally  preferable  for 
determining  nitric  acid,  combined  or  free.  Isolation  of  nitric  acid  by  precipita- 
tion as  nitron  nitrate  may  occasionally  be  used.  The  fairly  insoluble,  crystalline 
compound,  CaoHieN^HNOs  is  formed  by  addition  of  the  base  diphenyl-endo- 


300  NITROGEN 

anilo-hydro-triazole  (nitron)  to  the  solution  containing  the  nitrate  as  directed 
under  Separations.  The  precipitate  washed  with  ice-water  is  dried  to  constant 
weight  at  110°  C.  16.53%  of  the  compound  is  N03. 

NOTE.  The  following  acids  should  not  be  present  in  the  solution,  since  their 
nitron  salts  are  not  readily  soluble :  nitrous,  chromic,  chloric,  perchloric,  hydrobromic, 
hydroiodic,  hydroferrocyanic,  hydroferricyanic,  oxalic,  picric  and  thiocyanic  acids. 

Solubility  of  less  soluble  nitron  salts  in  100  cc.  of  water.  Nitron  nitrate  =  0.0099 
gram,  nitron  bromide  =  0.61  gram,  iodide  =  0.01 7  gram,  nitrite  =  0.19  gram,  chromate 
=  0.06  gram,  chlorate  0.12  gram,  perchlorate  =  0.008  gram,  thiocyanate  =  0.04  gram. 
(Treadwell  and  Hall,  "Analytical  Chemistry,  Quantitative  Analysis.") 


VOLUMETRIC  METHODS 

Direct  Estimation  of  Nitrates  by  Reduction  to  Ammonia. 
Modified  Devarda  Method  1 

An  accurate  procedure  for  the  determination  of  nitrogen  in  nitrates  is  Allen's 
modification  of  the  Devarda  method.  The  method  is  based  upon  the  quantita- 
tive reduction  of  nitrates  to  ammonia  in  an  alkaline  solution  by  an  alloy  con- 
sisting of  45  parts  of  aluminum,  50  parts  of  copper  and  5  parts  of  zinc.  The 
ammonia  evolved  is  distilled  into  standard  sulphuric  acid  and  thus  estimated. 
The  method,  originally  designed  for  the  valuation  of  sodium  or  potassium  nitrates, 
is  also  of  value  in  the  determination  of  nitric  acid,  nitrites  or  ammonia.  In  the 
latter  case  the  alloy  is  omitted. 

Reagents  Required.  Devarda' s  Alloy.  Forty-five  parts  aluminum,  50  parts 
copper  and  5  parts  zinc.  The  aluminum  is  heated  in  a  Hessian  crucible  in  a  fur- 
nace until  the  aluminum  begins  to  melt,  copper  is  now  added  in  small  portions 
until  liquefied  and  zinc  now  plunged  into  the  molten  mass.  The  mix  is  heated 
for  a  few  moments,  covered  and  then  stirred  with  an  iron  rod,  allowed  to  cool 
slowly  with  the  cover  on  and  the  crystallized  mass  pulverized. 

Standard  Sulphuric  Acid.  This  is  made  from  the  stock  C.P.  acid  by  dilu- 
tion so  that  1  cc.  is  equal  to  0.0057  gram  H2S04,  100  cc.  of  acid  of  this  strength 
being  equivalent  to  approximately  1  gram  of  sodium  nitrate.  (A  tenth  normal 
acid  will  do,  a  smaller  sample  being  taken  for  analysis.)  Since  it  is  necessary  to 
standardize  this  acid  against  a  standard  nitrate,  it  is  advisable  to  have  an  acid 
especially  for  this  determination  rather  than  a  common  reagent  for  general  use. 

Standardization  of  the  Acid.  11.6  grams  of  standard  potassium  nitrate, 
equivalent  to  about  9.6  grams  of  NaN03,  is  dissolved  and  made  to  volume  in  the 
weighing  bottle  (100  cc.),  and  10  cc.  is  placed  in  the  Devarda  flask,  reduced  and 
the  ammonia  distilled  into  100  cc.  of  the  acid,  exactly  as  the  following  method 
describes.  The  temperature  of  the  acid  is  noted  and  its  value  in  terms  of  H2S04, 
KN03  and  NaN03  stated  on  the  container.  The  acid  expands  or  contracts 
0.029  cc.  for  every  degree  centigrade  above  or  below  the  temperature  of  stand- 
ardization. 

Standard  Potassium  Nitrate.  The  purest  nitrate  that  can  be  obtained  is 
recrystallized  in  small  crystals,  by  stirring,  during  the  cooling  of  the  supersatu- 
rated concentrated  solution,  and  dried  first  at  100°  C.  for  several  hours  and  then 

1  Paper  by  W.  S.  Allen,  General  Chemical  Company,  Eighth  International  Con- 
gress of  Applied  Chemistry. 


NITROGEN 


301 


at  210°  C.  to  constant  weight.  Chlorides,  sulphates,  carbonates,  lime,  magnesia 
and  sodium  are  tested  for  and  if  present  are  determined  and  allowance  made. 

Standard  Sodium  Hydroxide.  This  should  be  made  of  such  strength  that  1  cc. 
is  equal  to  1  cc.  of  the  standard  acid,  2  cc.  methyl  red  being  used  as  indicator. 
Ten  cc.  of  the  acid  are  diluted  to  500  cc.  and  the  alkali  added  until  the  color  of 
the  indicator  changes  from  a  red  to  a  straw  color. 

Methyl  Red  Solution.  0.25  gram  of  methyl  red  is  dissolved  in  2000  cc.  of 
95%  alcohol;  2  cc.  of  the  indicator  is  used  for  each  titration.  As  the  indicator 
is  sensitive  to  C02,  all  water  used  must  first  be  boiled  to  expel  carbonic  acid. 
(Baker  &  Adamson,  manufacturers  of  methyl  red.) 

Sodium  Hydroxide — Sp.gr.  1.3.  Pure  sodium  hydroxide  is  dissolved  in 
distilled  water  and  boiled  in  an  uncovered  casserole  with  about  1  gram  of 
Devarda's  alloy  to  remove  ammonia.  This  is  cooled  and  kept  in  a  well-stoppered 
bottle. 

Apparatus.  This  is  shown  in  the  accompanying  illustration,  Fig.  51 .  It  consists 
of  the  Devarda  flask  connected  to  the  scrubber  K,  filled  with  glass  wool.  This 


FIG.  51. — Devarda's  Apparatus. 

scrubber  is  heated  by  an  electric  coil  or  by  steam  passed  into  the  surrounding 
jacket.  The  scrubber  prevents  caustic  spray  from  being  carried  over  into  the 
receiving  flask  0.  The  form  of  the  apparatus  can  best  be  ascertained  from  the 
sketch. 

Weighing  bottle  with  graduation  at  100  cc.  and  a  10-cc.  dropper  with  rubber 
bulb  is  used  for  weighing  out  the  sample  in  solution.    See  Fig.  52. 


302  NITROGEN 

Preparation  of  the  Sample 

Weight.  It  is  advisable  to  take  a  large  sample  if  possible,  e.g.,  100  grams 
of  NaN03,  119  grams  of  KN03  or  about  80  grams  of  strong  HN03  (95%)  or  more 
if  the  acid  is  dilute.  Solids  are  taken  from  a  large  sample,  all 
lumps  being  broken  down.  After  dissolving  in  water  the  sample 
is  made  up  to  1  liter.  (Scum  is  broken  up  by  addition  of  a 
little  alcohol.)  One  hundred  cc.  of  this  solution  is  placed  in 
the  weighing  bottle,  which  has  been  previously  weighed,  being 
perfectly  clean  and  dry.  The  difference  is  the  weight  of  the 
100-cc.  sample. 

Manipulation.  All  parts  of  the  apparatus  are  washed  out 
with  C02-free  water.  All  water  used  in  this  determination 
should  be  boiled  to  expel  C02.  Ninety-eight  cc.  of  the  standard 
acid  is  placed  in  flask  0  and  washed  down  with  2  to  3  cc.  of 
water.  Two  cc.  of  the  standard  acid  is  placed  in  flask  P  and 
washed  down  with  10  cc.  of  water  and  13  to  14  drops  of  methyl 
FIG.  52.  red  indicator  added.  Connections  are  made  between  the  flasks 
Weighing  Bottle  an(*  tne  scrubDer-  (The  correction  is  made  for  the  acid,  the 
and  Drooner  temperature  being  noted  at  the  time  of  withdrawal.)  A  cas- 
serole, filled  with  cold  water,  is  placed  under  F  (see  illustration). 
The  stem  E  is  removed  from  the  Devarda  flask  and  10  cc.  (or  more)  of  the 
nitrate  added  by  means  of  the  dropper  in  the  weighing  bottle,  a  funnel  having  been 
inserted  in  the  flask.  The  bottle  reweighed  gives  the  weight  of  the  sample 
removed,  by  difference.  The  nitrate  is  washed  down  with  10  cc.  of  water  and 
25  cc.  of  20%  caustic  added  (free  from  NH3),  the  alkali  washed  down  with  10  cc. 
more  of  water  and  then  3  grams  of  Devarda  alloy  placed  in  the  flask  by  means  of 
dry  funnel.  The  stem  E  is  quickly  replaced,  the  stopcock  being  turned  to  close 
the  tube.  The  reaction  begins  very  soon.  If  it  becomes  violent,  the  reaction 
may  be  abated  by  stirring  the  water  in  the  casserole,  thus  cooling  the  sample. 
After  the  energetic  action  has  abated  (five  minutes),  the  casserole  with  the  cold 
water  is  removed  and  the  action  allowed  to  continue  for  twenty  minutes,  mean- 
time heat  or  steam  is  turned  on  in  the  scrubber.  E  is  connected  at  C  to  the 
flask  B  containing  caustic  to  act  as  a  scrubber.  It  is  advisable  to  have  a  second 
flask  containing  sulphuric  acid  attached  to  the  caustic  to  prevent  ammonia  from 
the  laboratory  entering  the  system.  A  casserole  with  hot  water  is  placed  under 
F  and  the  burner  lighted  and  turned  on  full.  A  gentle  suction  is  now  applied 
at  R,  the  stop-cock  D  being  turned  to  admit  pure  air  into  the  evolution  flask;  the 
rate  should  be  about  5  to  6  bubbles  per  second.  The  suction  is  continued  for 
thirty  minutes,  hot  water  being  replaced  in  the  casserole  as  the  water  evaporates. 
The  heat  is  now  turned  off  and  the  apparatus  disconnected  at  M  and  /.  The 
contents  of  this  elbow  and  the  condenser  are  washed  into  the  flask  0.  The  acid 
in  0  and  P  poured  into  an  800-cc.  beaker  and  rinsed  out  several  times.  The 
volume  in  the  beaker  is  made  up  to  500  cc.,  1  cc.  of  methyl  red  added,  and  the 
free  acid  titrated  with  the  standard  caustic.  The  end-point  is  a  straw  yellow. 
Calculation.  The  cc.  of  the  back  titration  with  caustic  being  deducted, 
the  volume  of  the  acid  remaining  (e.g.,  combined  with  ammonia)  is  corrected  to 
the  standard  condition.  Expansion  or  contraction  of  the  acid  is  0.029  cc.  per  each 
degree  C^  above  or  below  the  temperature  at  which  the  acid  was  standardized. 
If  the  acid  is  exactly  0.057  gram  H2S04  per  cc.,  the  result  multiplied  by  0.9S9  and 


NITROGEN"  303 

divided  by  the  weight  of  the  sample  taken  gives  per  cent  nitrate.     (In  terms  of 
NaN03.) 

The  Weight  of  the  Sample.  Ten  times  the  difference  of  the  weighings 
of  the  bottle  W  before  and  after  removal  of  the  10  cc.  and  the  product  divided 
by  the  weight  of  the  100  cc.  of  the  solution  equals  the  weight  of  solid  taken. 

Example.  Weight  of  the  bottle  + 100  cc.  sample  =  218  grams.  Weight  of  the  bottle 
=  112  grams,  therefore  weight  of  100  cc.  NaNO3  =  106  grams. 

Weight  of  the  bottle  +  100  cc.  sample  =  218.  Weight  after  removal  of  10  cc  =207.4 
grams,  therefore  sample  taken  =  10. 6  grams,  including  the  added  water.  Now  from 
above  the  weight  of  the  actual  sample  taken  =  10.6  X 10  •*• 106  =  1  gram. 

Temperature  Correction.  Temperature  of  standardization  =  20°  C.  Temperature 
of  the  sulphuric  acid  when  taken  for  the  analysis  =  31°  C.  Back  titration  of  the 
caustic  =  2  cc.  The  correct  volume  =  (100 -2) -((31-20)  X0.029)  =97.681  cc. 
H2SO4  combined  with  ammonia  from  the  reduced  nitrate.  97.681  X0.989  -*- 1  =96.62% 
NaNO3. 

Factors.    H2SO4X2.06107  =  KNO3  or  Xl.7334  =  NaNO3  or  Xl.2850  =  HNO3. 

H2SO4X  0.9587  =  HNO2     or     X0.3473=NH3. 

NH3X3.6995  =  HNO3     or     X4.9906  =  NaNO3     or     X  4.0513  =  NaNO2. 

NaNOaXl.l894=KNO,    and    KNO3X  0.8408  =  NaN03. 


ANALYSIS   OF  NITRATE  OF  SODA 

The  following  impurities  may  occur  in  nitrate  of  soda :  KN03,  NaCl,  Na2S04, 
Na2C03,  NaCIO,,  NaC104,  Fe203,  A1203,  CaO,  MgO,  Si02,  H20,  etc.  In  the 
analysis  of  sodium  nitrate  for  determination  of  NaN03  by  difference,  moisture, 
NaCl,  Na2S04  and  insoluble  matter  are  determined  and  their  sum  deducted 
from  100,  the  difference  being  taken  as  NaN03.  Such  a  procedure  is  far  from 
accurate,  the  only  reliable  method  being  a  direct  determination  of  niter  by  the 
Devarda  method  given  in  detail.  The  following  analysis  may  be  required  in  the 
valuation  of  the  nitrate  of  soda. 

Determination  of  Moisture 

Twenty  grams  of  sample,  are  heated  in  a  weighed  platinum  dish  at  205  to 
210°  C.  for  fifteen  minutes  in  an  air  bath  or  electric  oven.  The  loss  of  weight 
multiplied  by  5  =  per  cent  moisture.  (Save  sample  for  further  tests.) 

Insoluble  Matter 

Ten  grams  are  treated  with  50  cc.  of  water  and  filtered  through  a  tared 
Gooch.  The  increased  weight  dried  residue  (100°  C.)  multiplied  by  10=per 
cent  insoluble  matter.  (Save  filtrate.) 

Sodium  Sulphate 

The  moisture  sample  is  dissolved  in  20  cc.  hot  water  and  transferred  to  a 
porcelain  crucible.  It  is  evaporated  several  times  with  hydrochloric  acid  to 
dryness  to  expel  nitric  acid.  (Until  no  odor  of  free  chlorine  is  noticed  when  thus 
treated.)  Fifty  cc.  of  water  and  5  cc.  hydrochloric  acid  are  now  added  and  the 


304  NITROGEN 

sample  filtered.  Any  residue  remaining  is  principally  silica.  The  nitrate  is 
heated  to  boiling,  10  cc.  of  10%  barium  chloride  solution  added,  and  the  precipi- 
tated sulphate  filtered  off,  ignited  and  weighed. 

BaS04X  3.0445=  per  cent  Na2S04. 

Iron,  Alumina,  Lime,  and  Magnesia 

These  impurities  may  be  determined  on  a  20-gram  dried  sample,  the 
material  being  dried  and  evaporated  as  in  case  of  the  sodium  sulphate  determina- 
tion. The  filtrate  from  silica  is  treated  with  ammonium  hydroxide  and  Fe(OH)3 
and  A1(OH)3  filtered  off.  Lime  is  precipitated  from  the  iron  and  alumina  filtrate 
as  oxalate  and  magnesia  determined  by  precipitation  as  phosphate  from  the 
lime  nitrate  by  the  standard  procedures. 

Sodium   Chloride 

The  filtrate  from  the  insoluble  residue  is  brought  to  boiling  and  magnesia, 
MgO  (Cl  free),  is  added  until  the  solution  is  alkaline  to  litmus.  0.5  cc.  of  1% 
potassium  chromate  (K2Cr04)  solution  is  added  as  an  indicator  and  then  the 
solution  is  titrated  with  a  standard  solution  of  silver  nitrate  until  a  faint  red 
tinge  is  seen,  the  procedure  being  similar  to  the  determination  of  chlorides  in 
water  by  silver  nitrate  titration.  The  cc.  AgN03Xfactor  for  this  reagentX  10  =per 
cent  NaCl. 

Silver  nitrate  is  standardized  against  a  salt  solution. 

Carbonates 

This  determination  is  seldom  made.  C02  may  be  tested  for  by  addition  of 
dilute  sulphuric  acid  to  the  salt.  Effervescence  indicates  carbonates.  Any 
evolved  gas  may  be  tested  by  lime  water,  which  becomes  cloudy  if  C02  is  present. 
For  details  of  the  procedure  reference  is  made  to  the  chapter  on  Carbon. 


DETERMINATION  OF  NITRIC  NITROGEN  IN  SOIL  EXTRACTS 
Vamari-Mitscherlich-Devarda  Method 

Procedure.  Forty  cc.  of  water,  a  small  pinch  of  magnesia  and  one  of  mag- 
nesium sulphate  are  added  to  flask  D  of  the  Mitscherlich  apparatus  (Fig.  53). 
Twenty-five  cc.  of  standard  acid  and  60  cc.  of  neutral  redistilled  water  are  placed 
in  flask  F\  250  or  300  cc.  of  aqueous  soil  extract  are  placed  in  a  500-cc.  Kjeldahl 
flask,  2  cc.  of  50%  sodium  hydroxide  added,  the  mouth  of  the  flask  closed  with 
a  small  funnel  to  prevent  spattering,  and  the  contents  of  the  flask  boiled  for 
thirty  minutes.  The  water  which  has  boiled  off  is  replaced,  and,  after  cooling, 
1  gram  of  Devarda's  alloy  (60  mesh),  and  a  small  piece  of  paraffin  are  added 
and  the  flask  connected  with  the  apparatus;  reduction  and  distillation  are  carried 
on  for  forty  minutes.  The  receiver  contents  are  then  cooled,  4  drops  of  0.02% 


NITROGEN 


305 


solution  of  methyl  red  added,,  the  excess  acid  is  nearly  neutralized,  the  liquid 
boiled  to  expel  C02j  cooled  to  10  to  15°  and  the  titration  completed. 


Hopkins 
Tube 


500  c.c. 
Jena 
KjeldaM 

Flask 


200c.c. 

Jena 

Flask 


rHeavy  Waited 
Quartz  Tube 
4,5mm.  I.  D. 

E  I 


3cm, 


17cm. 


'SOOcc. 

Erlenmeyer^ 
Flask 


FIG.  53. — Mitscherlich's  Apparatus  for  Nitrogen  Determination. 


DETERMINATION   OF   NITROGEN   OF   NITRATES    (AND 
NITRITES)   BY   MEANS   OF  THE   NITROMETER 

The  nitrometer  is  an  exceedingly  useful  instrument  employed  in  the  accurate 
measurement  of  gases  liberated  in  a  great  many  reactions  and  has  therefore  a 
number  of  practical  applications.  It  may  be  used  in  the  determination  of  carbon 
dioxide  in  carbonates;  the  available  oxygen  in  hydrogen  dioxide;  in  the  valua- 
tion of  nitrous  ether  and  nitrites;  in  the  valuation  of  nitrates  and  nitric  acid 
in  mixed  acids. 

The  method  for  the  determination  of  nitrogen  in  nitrates,  with  which  we 
are  concerned  in  this  chapter,  depends  on  the  reaction  between  sulphuric  acid 
and  nitrates  in  presence  of  mercury: 

2KN03+4H2S04+3Hg=K2S04+3HgS04+4H20+2NO. 

The  simplest  type  of  apparatus  is  shown  in  the  illustration,  Fig.  54.  The 
graduated  decomposition  tube  has  a  capacity  of  100  cc.  It  is  connected  at  the 
base  by  means  of  a  heavy-walled  rubber  tubing  with  an  ungraduated  leveling 
tube  (6).  At  the  upper  portion  of  (a)  and  separated  from  it  by  a  glass  stop- 
cock (s)  is  a  bulb  (c)  of  about  5  cc.  capacity;  a  second  stop-cock  enables  com- 
pletely enclosing  the  sample,  as  may  be  necessary  in  volatile  compounds.  The 
glass  stop-cock  (s),  directly  above  the  graduated  chamber,  is  perforated  so  as 


306  NITROGEN 

to  establish  connection  with  the  tube   (d)   when  desired  and  the  graduated 
cylinder  (a). 

Procedure.  The  tube  (6)  is  filled  with  mercury  and  the  air  in  (a)  now  dis- 
placed by  mercury,  by  turning  the  stop-cock  to  form  an  open  passage  between 
(a)  and  (d)  and  then  raising  (b).  A  sample  of  not  over  0.35  gram  potassium 
nitrate  or  a  corresponding  amount  of  other  nitrates,  is  introduced  into  (c),  the 
material  being  washed  in  with  the  least  amount  of  water  necessary  (1  to  2  cc.). 
By  lowering  (b)  and  opening  the  stop-cock  s  the  solution  is  drawn  into  the 
decomposition  chamber,  taking  care  that  no  air  enters.  This  is  followed  by  about 
15  cc.  of  pure,  strong  sulphuric  acid  through  Si  and  s,  avoiding  admitting  air  as 
before.  NO  gas  is  liberated  by  the  heat  of  reaction  between  the  sulphuric  acid 
and  the  water  solution.  When  the  reaction  subsides,  the  tube  (a)  is  shaken 
to  mix  the  mercury  with  the  liquor  and  the  NO  completely  liberated.  The  gas 
is  allowed  to  cool  to  room  temperature  and  then  measured,  after  raising  or 
lowering  (b)  so  that  the  column  of  mercury  is  the  calculated  excess  of  height 
above  that  in  (a)  in  order  to  have  the  gas  under  atmospheric  pressure.  The 
excess  of  height  is  obtained  by  dividing  the  length  of  the  acid  layer  in  (d),  in 
millimeters,  by  7  and  elevating  the  level  of  the  mercury  in  (6)  above  that  in  (a) 
by  this  quotient;  i.e.,  if  the  acid  layer  =21  mm.  the  mercury  in  (b)  would  be 
3  mm.  above  that  in  (a).  The  volume  of  gas  is  reduced  to  standard  conditions 
by  using  the  formula 

V(P-w) 


F'  = 


760(1+0.003670' 


V  —  volume  under  standard  conditions;  V=  observed  volume;  P=  observed 
barometric  pressure  in  mm.;  w=  tension  of  aqueous  vapor  at  the  observed  tem- 
perature, expressed  in  millimeters;  t=  observed  temperature. 

One  cc.  gas  =4.62  milligrams  of  KN03,     or    3.8  milligrams  NaNOs 

or    2.816  milligrams  HN03.  ^^  V->^  > 

Du  Pont  Nitrometer  Method  l 

The  Du  Pont  nitrometer,  Fig.  55,  is  the  most  accurate  apparatus  for  the  volu- 
metric determination  of  nitrates.  By  use  of  this,  direct  readings  in  per  cent  may 
be  obtained,  without  recourse  to  correction  of  the  volume  of  gas  to  standard  con- 
ditions and  calculations  such  as  are  required  with  the  ordinary  nitrometers. 

The  apparatus  consists  of  a  generating  bulb  of  300  cc.  capacity  E  with  its 
reservoir  F  connected  to  it  by  a  heavy-walled  rubber  tubing.  E  carries  two 
glass  stop-cocks  as  is  shown  in  illustration.  The  upper  is  a  two-way  stop-cock 
connecting  either  the  cup  or  an  exit  tube  with  the  chamber.  D  is  the  chamber- 
reading  burette,  calibrated  to  read  in  percentages  of  nitrogen,  and  graduated 
from  10  to  14%,  divided  in  1/100%.  Between  171.8  and  240.4  cc.  of  gas  must 
be  generated  to  obtain  a  reading.  A  is  also  a  measuring  burette,  that  may  be 
used  in  place  of  D  where  a  wider  range  of  measurement  is  desired.  "  It  is  used 
for  the  measurement  of  small  as  well  as  large  amounts  of  gas.  It  is  most  com- 
monly graduated  to  hold  300.1  milligrams  of  NO  at  20°  C.  and  760  mm.  pressure  , 
and  this  volume  is  divided  into  100  units  (subdivided  into  tenths)  each  unit 
being  equivalent  to  3.001  milligrams  of  NO.  When  compensated,  the  gas  from 

iSee  paper  by  J.  R.  Pitman,  Jour.  Soc.  Chem.  Ind.,  p.  983,  1900. 


NITROGEN 


307 


ten  times  the  molecular  weight  in  milligrams  of  any  nitrate  of  the  formula  RN03 
(or  five  times  molecular  weight  of  R,(N03)2)  should  exactly  fill  the  burette.  This 
simplifies  all  calculations;  for  example  the  per  cent  nitric  acid  in  a  mixed  acid 
would  be  « 

#63.02 


R=  burette  reading,  W  =  grams  acid  taken."1    C  is  the  compensating  burette 
very  similar  in  form  to  the  chamber  burette  D.    B  is  the  leveling  bulb,  by  the 


FIG.  54. — Nitrometer. 


FIG.  55. — Du  Font's  Nitrometer. 


raising  or  lowering  of  which  the  standard  pressure  in  the  system  may  be  obtained. 
The  apparatus  as  shown  in  Fig.  55  is  mounted  on  an  iron  stand.  As  in  the  more 
simple  form  of  apparatus,  previously  described,  mercury  is  used  as  the  con- 
fining liquid.  The  parts  are  connected  by  heavy-walled  rubber  tubing,  wired 
to  the  glass  parts. 


1  A.  W.  Betts,  Chemist,  E.  I.  DuPont  de  Nemours  Powder  Co.,  in  letter  to  author, 


308  NITROGEN 

Standardizing  the  Apparatus.  The  apparatus  having  been  arranged  and  the 
various  parts  filled  with  mercury,  the  instrument  is  standardized  as  follows: 
20  to  30  cc.  of  sulphuric  acid  are  drawn  into  the  generating  bulb  through  the 
cup  at  the  top,  and  at  the  same  time  about  210  cc.  of  air;  the  cocks  are  then 
closed,  and  the  bulb  well  shaken;  this  thoroughly  desiccates  the  air,  which  is  then 
run  over  into  the  compensating  burette  until  the  mercury  is  about  on  a  level  with 
the  12.30%  mark  on  the  other  burette,  the  two  being  held  in  the  same  relative 
position,  after  which  the  compensating  burette  is  sealed  off  at  the  top.  A 
further  quantity  of  air  is  desiccated  in  the  same  manner  and  run  into  the  read- 
ing burette  so  as  to  fill  up  to  about  the  same  mark;  the  cocks  are  then  closed, 
and  a  small  piece  of  glass  tubing  bent  in  the  form  of  a  U,  half  filled  with  sul- 
phuric acid  (not  water),  is  attached  to  the  outlet  of  the  reading  burette;  when 
the  mercury  columns  are  balanced  and  the  enclosed  air  cooled  down,  the  cock 
is  again  carefully  opened,  and  when  the  sulphuric  balances  in  the  U-tube,  and 
the  mercury  columns  in  both  burettes  are  at  the  same  level,  then  the  air  in  each 
one  is  under  the  same  conditions  of  temperature  and  pressure.  A  reading  is  now 
made  from  the  burette,  and  the  barometric  pressure  and  temperature  carefully 
noted,  using  the  formula 


P<273 

the  volume  this  enclosed  air  would  occupy  at  29.92  ins.  pressure  and  20°  C.  is 
found.  The  cock  is  again  closed  and  the  reservoir  manipulated  so  as  to  bring 
the  mercury  in  both  burettes  to  the  same  level,  and  in  the  reading  burette  to  the 
calculated  value  as  well.  A  strip  of  paper  is  now  pasted  on  the  compensating 
burette  at  the  level  of  the  mercury,  and  the  standardization  is  then  complete. 

Another  rapid  method  of  standardizing  is  to  fill  the  compensating  chamber 
with  desiccated  air  as  stated  in  the  first  procedure  and  then  to  introduce  into  the 
generating  chamber  1  gram  of  pure  potassium  nitrate  dissolved  in  2  to  4  cc.  of 
water,  the  cup  is  rinsed  out  with  20  cc.  of  66°  Be*aume  sulphuric  acid,  making 
three  or  four  washings  of  it,  each  lot  being  drawn  down  separately  into  the  bulb. 
The  generated  gas  formed  after  vigorous  shaking  of  the  mixture,  as  stated  under 
procedure,  is  run  into  the  measuring  burette.  The  columns  in  both  burettes  are 
balanced  so  that  the  reading  burette  is  at  13.85  (=per  cent  N  in  KN03).  A 
strip  of  paper  is  pasted  on  the  compensating  burette  at  the  level  of  the  mer- 
cury, and  standardization  is  accomplished.  By  this  method  the  temperature 
and  pressure  readings,  and  the  calculations  are  avoided.1 

Procedure  for  Making  the  Test.  Salts.  One  gram  of  sodium  or  potassium 
nitrate,  or  such  an  amount  of  the  material  as  will  generate  between  172  to  240  cc. 
of  gas,  is  dissolved  in  a  little  water  and  placed  in  the  cup  of  the  generating  bulb. 

Liquid  Acids.  The  acid  is  weighed  in  a  Lunge  pipette  and  the  desired  amount 
run  into  the  funnel  of  the  generating  bulb,  the  amount  of  acid  that  is  taken 
being  governed  by  its  nitrogen  content. 

The  sample  is  drawn  into  the  bulb;  the  funnel  is  then  rinsed  out  with  three 
or  four  successive  washings  of  95%  sulphuric  acid,  the  total  quantity  being 
20  cc. 

To  generate  the  gas,  the  bulb  is  shaken  well  until  apparently  all  the  gas  is 

1  Standardization  with  "  C.  P.  KNO3  is  the  better,  as  it  is  less  tedious  and  is  not 
subject  to  the  correction  errors  that  cannot  be  escaped  when  standardizing  with 
The  KNOj  must  be  of  undoubted  purity."  —  A.  W.  Betts. 


NITROGEN  309 

formed,  taking  care  that  the  lower  stop-cock  has  been  left  open,  this  cock  is  then 
closed  and  the  shaking  repeated  for  two  minutes.  The  reservoir  is  then  lowered 
until  about  60  cc.  of  mercury  and  20  cc.  of  acid  are  left  in  the  generating  bulb. 
There  will  remain  then  sufficient  space  for  220  cc.  of  gas. 

NOTE.  If  too  much  mercury  is  left  in  the  bulb,  the  mixture  will  be  so  thick  that 
it  will  be  found  difficult  to  complete  the  reaction,  a  long  time  will  be  required  for  the 
residue  to  settle  and  some  of  the  gas  is  liable  to  be  held  in  suspension  by  the  mercury, 
so  that  inaccurate  results  follow. 

The  generated  gas  is  now  transferred  to  the  reading  burette,  and  after  wait- 
ing a  couple  of  minutes  to  allow  for  cooling,  both  burettes  are  balanced,  so  that 
in  the  compensating  tube  the  mercury  column  is  on  a  level  with  the  paper  mark 
as  well  as  with  the  column  in  the  reading  burette;  the  reading  is  then  taken. 

If  exactly  one  gram  of  the  substance  is  taken  the  percentage  of  nitrogen  may 
be  read  directly,  but  in  case  of  other  amounts  being  taken,  as  will  invariably  be 
the  case  in  the  analysis  of  acids,  the  readings  are  divided  by  the  weight  of  the 
substance  and  multiplied  by  4.5  to  obtain  the  per  cent  of  nitric  acid  mono- 
hydrate  present. 

The  procedure  may  be  used  for  determining  nitrites  as  well  as  nitrates. 

Determination  of  HNO3  in  Oleum  by  Du  Pont  Nitrometer  Method 1 

About  10  cc.  oleum  are  weighed  in  a  30-ce.  weighing  bottle,  10  cc.  95% 
reagent  sulphuric  acid  added  and  mixed  by  shaking.  This  mixture  is  transferred 
to  the  nitrometer  reaction  tube  and  the  weighing  bottle  and  nitrometer  cup 
rinsed  with  three  5-cc.  portions  of  the  reagent  sulphuric  acid  which  is  drawn  into 
the  reaction  tube.  This  is  vigorously  shaken  for  three  minutes  and  the  gas 
then  passed  to  the  measuring  tube  and  allowed  to  stand  for  about  five  minutes, 
after  which  the  mercury  levels  are  adjusted  and  the  reading  taken. 

It  is  obvious  that  this  determination  includes  any  nitrous  acid  in  the  oleum. 

Combined  Nitric  Acid 

The  nitric  acid  in  nitrates  may  be  determined  by  titration  with  ferrous 
sulphate.  The  nitrate  dissolved  in  a  little  water  is  run  into  strong  sulphuric  acid 
and  titrated  with  standard  ferrous  sulphate  according  to  the  procedure  described 
for  determining  free  nitric  acid  in  mixed  acids  on  page  515. 

1  By  courtesy  of  E.  I.  du  Pont  de  Nemours  Powder  Co. 


PHOSPHORUS 

WILFRED  W.  SCOTT 

(   yellow  1.831  (     44°  ,  „„„   v 

P4,  ar.M?r.31.O4;  sp.gr.  -\        ,          2Qfi*   fn.p.  J\  7oK°»    °-P'  }  »  oxides, 

P203,  P02,  P205;  acids,  H3PO2,  H3PO3,  HsPO4,  HPO3,  H4P2O7. 


290°  C 


.      DETECTION 

Element.  Phosphorus  is  recognized  by  its  glowing  (phosphorescence)  in 
the  air.  The  element  is  quickly  oxidized  to  P206;  if  the  yellow  modification  is 
slightly  warm  (34°  C.)  the  oxidation  takes  place  with  such  energy  that  the 
substance  bursts  into  flame.  The  red  form  is  more  stable.  It  ignites  at  260°  C. 

Boiled  with  KOH  or  NaOH  it  forms  phosphine,  PH3,  which  in  presence  of 
accompanying  impurities  is  inflammable  in  the  air. 

Phosphorus  oxidized  to  P205  may  be  detected  with  ammonium  molybdate, 
a  yellow  compound,  (NH4)3P04-12Mo03-3H20,  being  formed. 

Acids.  Hypophosphorous  Acid,  HsPOz,  heated  with  copper  sulphate  to 
55°  C.  gives  a  reddish-black  compound,  Cu2H2,  which  breaks  down  at  100°  to 
H  and  Cu.  Permanganates  are  reduced  immediately  by  hypophosphorous  acid. 
No  precipitates  are  formed  with  barium,  strontium  or  calcium  solutions.  Zinc 
in  presence  of  sulphuric  acid  reduces  hypophosphorous  acid  to  phosphine,  PH3. 

Phosphorous  Acid,  H3PO3.  Copper  sulphate  is  reduced  to  metallic  copper 
and  hydrogen  is  evolved,  no  Cu2H2  being  formed  as  in  case  of  hypophosphorous 
acid.  Permanganates  are  reduced  slowly.  Added  to  solutions  of  barium,  stron- 
tium or  calcium  white  phosphites  of  these  elements  are  precipitated.  Alkali 
phosphites  are  soluble  in  water,  while  hypophosphites  are  not  readily  soluble. 

Orthophosphoric  Acid,  HzPOt.  Ammonium  phosphomolybdate  precipi- 
tates yellow  ammonium  phosphomolybdate  from  slightly  nitric  acid  solutions. 
The  precipitate  is  soluble  in  ammonium  hydroxide. 

Metaphosphoric  Acid,  HPO3.  Converted  by  nitric  acid  in  hot  solutions 
to  the  ortho  form.  Metaphosphoric  acid  is  not  precipitated  by  ammonium 
molybdate. 

Pyrophosphoric  Acid,  H4P2O7.  Converted  to  Orthophosphoric  acid  in  hot 
solutions  by  nitric  acid.  No  precipitate  is  formed  with  ammonium  molybdate. 

COMPARISON  OF  ORTHO,  META  AND  PYROPHOSPHORIC  ACIDS 


Reagent. 

O  rthophosphoric 
acid. 

Metaphosphoric 
acid. 

Pyrophosphorio 
acid. 

Ammonium  molybdate 

Yellow  ppt 

No  ppt 

No  ppt 

Albumin 

Coagulated 

Not  coagulated 

Zinc  sulphate,  cold,  in  excess. 

No  ppt 

White  ppt 

Silver  nitrate  in  neutral  solution  
Magnesium  salts  

Yellow  ppt.. 
.Ag3P04 
White  ppt. 

White  ppt., 
AgP03 

No  DDt. 

White  ppt., 
Ag4P2O7 
No  ppt. 

310 


PHOSPHORUS 


311 


Phosphorous  acids  are  distinguished  from  phosphoric  acids  by  the  phosphine 
formed  with  the  former  when  acted  upon  with  zinc. 

Acid  phosphates  are  distinguished  from  normal  phosphates  as  follows: 
Neutral  silver  nitrate  added  to  an  acid  phosphate  liberates  free  nitric  acid  (Litmus 
test),  the  following  reaction  taking  place: 

3AgN03+Na2HP04=Ag3P04+2NaN03+HN03. 

The  solution  resulting  when  silver  nitrate  is  added  to  normal  phosphate 
solution  is  neutral. 

3AgN03+Na3P04  =  Ag3P04+3NaN03. 


ESTIMATION 

The  determination  of  the  pentoxide  of  phosphorus  is  required  in  a  large 
number  of  substances,  since  it  is  widely  distributed  in  the  form  of  phosphates — 
calcium  phosphate,  Ca3(P04)2;  fluor  apatite,  3Ca3(P04)2-CaF2;  chlor  apatite, 
3Ca3(P04)2-CaCl2;  vivianite, Fe3(P04)2-8H20;wavelite, 2A12(P04)2-A12(OH)6-9H20; 
pyromorphite,  3Pb3(P04)2-PbCl2;  phosphates  of  iron  and  calcium  in  phosphate 
ores,  hence  in  slags  of  the  blast  furnace.  It  occurs  in  fertile  soils,  bones,  plant 
and  animal  tissues. 

The  chemist  is  especially  concerned  in  the  determination  of  phosphoric 
acid  (P205),  in  the  evaluation  of  materials  used  for  the  manufacture  of  the  acid — 
bone  ash  and  phosphate  rock  (see  table  below).  Generally,  determinations 
of  lime,  iron  and  alumina  are  also  desired  and  frequently  a  more  complete 
analysis.  In  the  analysis  of  phosphoric  acid  certain  impurities  occurring  in 
the  crude  material  used  are  determined,  e.g.,  iron,  lime,  magnesia,  sulphuric, 
hydrochloric  and  hydrofluoric  acids,  etc.  Phosphoric  acid  is  determined  in 
the  evaluation  of  phosphate  fertilizers,  phosphates  used  in  medicine,  phosphate 
baking  powders,  etc. 

The  element  is  determined  in  iron,  steel,  phosphor  bronzes,  and  other  alloys. 

TYPICAL  ANALYSES* 


Substance. 

Bone  Ash. 

Charlestown 
Phosphate. 

Spanish 
Phosphorite. 

Sombrero 
Phosphate. 

Redonda 
Phosphates. 

Canadian 
Phosphate. 

Phosphoric  oxide  .... 
Sulphur  trioxide  
Carbon  dioxide 

39.55 
4  43- 

27.17 
3.30 
4  96 

33.38 
0.57 
4  10 

35.12 
7  40 

35.47 

37.68 

Lime 

52  46 

44  03 

47  16 

51.33 

51.04 

Magnesia 

1  02 

0  37 

trace 

Alumina. 

1  44 

0  89 

+Fe 

20.17 

FeaO3, 

Ferric  oxide 

0.17 

0  43 

2.59 

1.02 

8.85 

A12O3, 

Fluorine,  etc  

2  38 

4.01 

F.  etc. 

Alkaline  salts  

0.87 

0.42 

=  6.88 

Silica  —  sand,  etc  

0.51 

5.60 

3.71 

2.02 

9.70 

4.29 

*  Thorpe,  "  Dictionary  of  Applied  Chemistry,"  Longmans,  Green  &  Co. 

Preliminary  Remarks.  Practically  all  procedures  for  the  determination  of 
phosphorus  depend  upon  its  oxidation  to  ortho  phosphoric  acid  and  its  pre- 
cipitation by  ammonium  molybdate  from  a  nitric  acid  solution  as  ammonium 
phospho-molybdate.  It  may  now  be  determined  either  gravimetrically  or 
volumetrically.  Two  procedures  are  of  importance  in  the  gravimetric  deter- 


312  PHOSPHORUS 

mination  of  phosphorus;  the  first  depends  upon  the  direct  weighing  of  the 
yellow  phosphomolybdate,  dried  at  110°  C.;  the  second,  on  the  conversion  of  the 
yellow  precipitate  to  the  magnesium  salt  and  its  ignition  to  pyrophosphate. 
Two  volumetric  procedures,  which  are  of  special  value  in  the  determination  of 
small  amounts  of  phosphorus  as  in  case  of  phosphorus  in  iron  and  steel,  are  to  be 
recommended  for  their  rapidity  and  accuracy.  One  of  these  is  to  dissolve  the 
ammonium  phosphomolybdate  in  a  known  amount  of  standard  caustic,  titrate 
the  excess  of  alkali  with  standard  acid,  which  indicates  the  alkali  required  to 
neutralize  the  molybdic  acid  in  the  yellow  precipitate.  From  this  the 
amount  of  phosphorus  present  may  be  calculated.  A  second  procedure  of  equal 
accuracy  and  rapidity  is  to  dissolve  the  molybdate  in  ammonia,  add  an  excess 
of  sulphuric  acid,  pass  the  warm  solution  through  a  column  of  zinc  and  titrate 
the  reduced  molybdic  acid  with  standard  potassium  permanganate,  the  amount 
of  permanganate  required  being  a  measure  of  the  phosphorus  present. 

The  impurities  interfering  in  the  procedures  are  silica  and  arsenic  acid.  The 
first  may  be  eliminated  by  dehydration  of  the  silicic  acid  in  the  solution  and  its 
removal  as  insoluble  Si02  by  filtration.  Arsenic  in  small  quantities  does  not 
interfere  under  certain  conditions;  in  large  quantities  its  removal  is  imperative. 

Preparation  and  Solution  of  the  Sample 

Amount  of  the  Sample  Required.  For  accurate  results  it  is  advisable  to 
take  a  fairly  large  sample,  5  to  10  grams,  and  when  it  has  been  dissolved,  to 
dilute  to  a  definite  volume,  500  or  1000  cc.  Aliquots  of  this  solution  are  tal:en 
for  analysis. 

Iron  Ores,  Phosphate  Rock  and  Minerals.  Five  to  10  grams  of  the  pul- 
verized material  placed  in  a  3-in.  porcelain  dish  are  digested  for  an  hour  with 
50  to  100  cc.  of  concentrated  hydrochloric  acid  (sp.gr.  1.19),  the  dish  being  covered 
by  a  clock-glass  and  placed  on  a  steam  bath.  The  acid  is  now  diluted  with 
half  its  volume  of  water  and  the  solution  filtered  into  a  porcelain  dish  of  suf- 
ficient capacity  to  hold  the  filtrate  and  washings.  The  residue  is  washed  with 
dilute  hydrochloric  acid  (1  :  1)  until  free  of  visible  iron  discoloration.  The 
filtrate  and  washings  are  evaporated  rapidly  on  a  hot  plate  to  small  volume 
and  then  to  dryness  over  the  steam  bath.  Meanwhile  the  insoluble  residue  and 
filter  are  ignited  in  a  20-cc.  platinum  crucible  over  a  Me"ker  burner  or  in  a  muffle 
furnace  and  the  residue  fused  with  ten  times  its  weight  of  sodium  carbonate. 
The  fusion  is  removed  by  inserting  a  platinum  wire  into  the  molten  mass, 
allowing  to  cool  and  then  gently  heating  until  the  mass  loosens  from  the  cru- 
cible, when  it  may  be  removed  on  the  wire.  The  cooled  mass  on  the  wire  and  that 
remaining  in  the  crucible  are  dissolved  in  dilute  hydrochloric  acid,  and  the 
filtered  solution  added  to  the  main  solution.  The  combined  solutions  are 
evaporated  to  dryness,  and  heated  gently  to  dehydrate  the  silica.  The  residue 
is  taken  up  with  a  few  cc.  of  hydrochloric  acid,  the  solution  diluted,  filtered 
and  the  Si02  washed  with  dilute  nitric  acid  solution.  The  combined  filtrates 
are  made  up  to  500  or  1000  cc.  Aliquots  of  this  solution  are  taken  for  analysis. 

Iron  and  Steel.  Five  to  10  grams  of  the  drillings  or  filings  are  dissolved  in  an 
Erlenmeyer  flask  with  50  to  100  cc.  of  dilute  nitric  acid,  1:1,  more  acid  being 
added  if  necessary.  When  dissolved,  a  strong  solution  of  KMnOi  is  added 
until  a  pink  color  appears;  on  boiling  brown  manganese  dioxide  forms  in  the 
solution  if  a  sufficient  amount  of  permanganate  has  been  added.  This  is  dis- 


PHOSPHORUS  313 

solved  by  adding  2%  sodium  thiosulphate  solution  in  just  sufficient  quantity  to 
dissolve  the  precipitate.  The  solution  is  diluted  to  a  convenient  volume  for 
analysis.  Where  a  number  of  determinations  are  to  be  made,  it  is  advisable 
to  weigh  the  amount  of  sample  desired  for  the  determination  and  to  precipitate 
the  ammonium  phosphomolybdate  in  the  flask  in  which  the  drillings  have  been 
dissolved. 

Ores  Containing  Titanium.  Titanium  may  be  recognized  by  the  red  color 
produced  by  hydrogen  peroxide,  H202,  added  to  the  sulphuric  acid  extract;  also 
by  the  reduction  test  with  zinc,  which  causes  a  play  of  colors,  the  solution  becom- 
ing colorless  by  the  reduction  of  iron,  then,  in  presence  of  titanium,  pink,  purple 
and  finally  blue.  (Vanadium  gives  similar  tests.)  Solutions  containing  titanium 
frequently  appear  milky  when  the  solution  is  diluted  before  filtering  off  the  insol- 
uble residue.  Since  titanium  forms  an  insoluble  compound  with  phosphoric  acid 
and  iron  oxide  l  the  final  residue,  obtained  by  the  method  of  solution  for  ores, 
phosphate  rock  and  minerals,  should  be  moistened  with  sulphuric  acid  and  the 
silica  expelled  with  hydrofluoric  acid.  The  solution  is  evaporated  to  dryness  and 
to  S03  fumes,  the  residue  fused  with  sodium  carbonate  and  taken  up  with  boiling 
water.  Ti02  remains  insoluble,  while  P20o  passes  into  the  filtrate  as  the  sodium 
salt.  The  procedure  may  be  shortened  by  treating  the  original  sample  directly 
according  to  this  method  of  solution,  a  2-gram  sample  being  taken,  as  larger 
amounts  are  difficult  to  handle. 

Soluble  Phosphates,  Phosphate  Baking  Powder,  etc.  A  water  extract 
is  generally  sufficient  to  get  the  material  in  solution.  In  case  iron,  alumina,  lime 
and  magnesia  salts  are  present,  as  may  occur  in  baking  powders,  an  extraction 
with  dilute  3%  nitric  acid  is  necessary.  It  is  advisable  to  dissolve  a  5-  to  10-gram 
sample  and  take  an  aliquot  part  of  the  solution  made  up  to  a  definite  volume. 
Before  precipitating  with  ammonium  phosphomolybdate,  5  grams  of  ammonium 
nitrate  should  be  added  for  each  gram  of  the  sample  taken  for  analysis  and  the 
solution  boiled  to  oxidize  compounds  of  phosphorus  to  the  orthophosphate 
form. 

Precipitation  of  Ammonium  Phosphomolybdate 

Precipitation  of  ammonium  phosphomolybdate  is  common  to  all  subsequent 
methods  for  determination  of  phosphorus,  and,  as  in  case  of  preparation  and  solu- 
tion of  the  sample,  details  of  this  procedure  will  not  be  repeated. 

Reaction. 


Special  Reagents  Required.  Ammonium  Molybdate.  One  hundred  grams 
of  pure  molybdic  acid  are  thoroughly  mixed  with  400  cc.  of  cold  distilled  water 
and  80  cc.  of  strong  ammonia  (sp.gr.  0.90)  added.  When  the  solution  is  com- 
plete it  is  poured  slowly  and  with  constant  stirring  into  a  mixture  of  400  cc. 
of  strong  nitric  acid  (sp.gr.  1,42)  and  600  cc.  distilled  water.  This  order  of 
procedure  should  be  followed,  as  the  nitric  acid  poured  into  the  ammonium 
molybdate  solution  will  cause  the  precipitation  of  a  difficultly  soluble  oxide  of 
molybdenum  and  render  the  reagent  practically  worthless.  Fifty  milligrams 
(0.50  gram)  of  micro  cosmic  salt,  dissolved  in  a  little  water  are  added,  the  pre- 
cipitate agitated,  then  allowed  to  settle  for  twenty-four  hours  and  the  clear  solu- 

1  Blair  "  Chemical  Analysis  of  Iron." 


314 


PHOSPHORUS 


tion  decanted  through  a  filter  into  a  large  reagent  bottle.  Sixty  cc.  of  the  reagent 
should  be  used  for  every  0.1  gram  of  P206  present  in  the  solution  analyzed. 

Potassium  Permanganate.  For  oxidation  purposes.  Two  per  cent  solution 
filtered  free  of  dioxide  through  asbestos  is  required. 

Amount  of  Sample  Required  for  Analysis.  If  the  material  contains  over 
20%  P206,  0.1  to  0.5-gram  sample  should  be  taken;  if  the  product  contains 
5  to  20%  P206,  1.0  to  0.5  gram  should  be  taken;  for  a  sample  containing  0.5 
to  5%,  2.5  to  1-gram  sample  is  taken,  and  for  P205  less  than  0.5%,  a  5-gram  sam- 
ple is  taken. 

Precipitation.  The  free  acid  of  the  solution  is  nearly  neutralized  by  addi- 
tion of  ammonium  hydroxide.  In  analysis  of  phosphate  rock  or  materials  com- 
paratively low  in  iron,  it  is  advisable  to  add  ammonium  hydroxide  in  quantity 
sufficient  to  cause  a  slight  permanent  precipitate  followed  by  just  sufficient  HN08 
to  dissolve  the  precipitate.  In  iron  and  steel  analysis  ammonium  hydroxide  is 
added  until  the  precipitated  iron  hydroxide  dissolves  with  difficulty  and  the 
solution  becomes  a  deep  amber  color  or  cherry  red.  In  analysis  of  soluble  phos- 
phates, litmus  paper  dropped  into  the  solution  indicates  the  neutral  point. 
Nitric  acid  is  added  to  the  neutral  or  slightly  acid  solution,  5  cc.  of  acid  for  every 
100  cc.  of  solution.  A  volume  of  150  to  200  cc.  of  solution  is  the  proper  dilu- 
tion for  samples  taken  in  amounts  above  recommended.  To  the  warm  solu- 
tion (not  over  80°  C.)  ammonium  molybdate  is  added,  60  cc.  of  the  reagent  being 
required  for  every  0.1  gram  of  P205  present.  The  solution  is  stirred,  or  shaken, 
if  in  a  flask,  until  a  cloudy  precipitate  of  ammonium  phosphomolybdate  appears. 
It  is  then  allowed  to  settle  on  the  steam  bath  at  a  temperature  of  40  to  60°  C., 
for  one  hour,  then  again  agitated  and  allowed  to  settle  in  the  cold  for  an  hour 
longer.  The  filtrate  should  be  tested  with  additional  ammonium  molybdate  for 
phosphorus.  The  yellow  precipitate  is  filtered  and  washed  with  1%  HN03  solu- 
tion followed  by  a  1%  solution  of  KN03,  or  NH4N03  or  (NH4)2S04  as  the  special 
case  requires.  Filtration  through  asbestos  in  a  Gooch  crucible  is  to  be  recom- 
mended. When  a  large  number  of  determinations  are  to  be  made,  as  in  case  of 
iron  and  steel,  filter  paper  is  more  convenient. 


GRAVIMETRIC  METHODS  FOR  DETERMINATION  OF 
PHOSPHORUS 

A.  Direct  Weighing  of  the  Ammonium  Phosphomolybdate 

The  sample  being  dissolved  and  the  ammonium  phosphomolybdate  precipitated 
according  to  directions  already  given  above,  the  supernatant  solution  is  filtered 
through  a  weighed  Gooch  crucible  and  washed  twice  by  decantation  with 
dilute  nitric  acid  (1%),  the  precipitate  washed  into  the  Gooch,  followed  by  two 
washings  with  1%  KN03  or  NH4N03  (neutral  solutions)  and  finally  with  water. 
The  precipitate,  free  from  contaminating  impurities,  is  dried  for  two  hours  in  an 
oven  at  110°  C.,  then  cooled  in  a  desiccator  and  weighed.  Weight  of  precipi- 
tateX0.0165=P,  or  XO. 03784  =P206. 

NOTE.  If  this  procedure  is  to  be  followed  it  will  be  convenient  to  take  1.65  grams 
sample,  if  the  phosphorus  content  will  allow.  Each  0.01  grain  of  precipitate  will  then 
equal  1%  P. 


PHOSPHORUS  315 


B.  Determination  of  Phosphorus  as  Magnesium  Pyrophosphate 

Magnesia  Mixture.  For  precipitation  of  ammonium  magnesium  phos- 
phate, 110  grams  of  magnesium  chloride  (MgCl2-6H20)  are  dissolved  in  a  small 
amount  of  water.  To  this  are  added  280  grams  of  ammonium  chloride  and 
700  cc.  of  ammonia  (sp.gr.  0.90);  the  solution  is  now  diluted  to  2000  cc.  with 
distilled  water.  The  solution  is  allowed  to  stand  several  hours  and  then  filtered 
into  a  large  bottle  with  glass  stopper.  Ten  cc.  of  the  solution  should  be  used  for 
every  0.1  gram  PaOs  present  in  the  sample  analyzed.  As  the  reagent  becomes 
old  it  will  be  necessary  to  filter  off  the  silica  that  it  gradually  accumulates  from 
the  reagent  bottle. 

Procedure.  The  ammonium  phosphomolybdate,  obtained  as  directed  (page 
314),  is  filtered  onto  a  12|  S.  &  S.  No.  589  filter  paper  and  washed  four  or  five  tunes 
with  dilute  1%  HN03.  The  precipitate  is  now  dissolved  from  the  filter  by  a  fine 
stream  of  hot  ammonium  hydroxide,  1:1,  catching  the  solution  in  the  beaker  in 
which  the  precipitation  was  made.  The  solution  and  washings  should  be  not  over 
100  to  150  cc.  Hydrochloric  acid  is  added  to  the  cooled  solution  to  neutralize  the 
excess  of  ammonia,  the  yellow  precipitate,  that  forms  during  the  neutralization, 
dissolving  with  difficulty,  when  sufficient  acid  has  been  added.  To  the  cooled 
solution  cold  magnesia  mixture  is  added  drop  by  drop  (2  drops  per  second)  with 
constant  stirring.  Ten  cc.  of  the  reagent  will  precipitate  0.1  gram  P^Os.  When  the 
solution  becomes  cloudy  the  stirring  is  discontinued  and  the  precipitate  allowed 
to  settle  ten  minutes.  Ammonium  hydroxide  is  added  until  the  solution  con- 
tains about  one-fourth  its  original  volume  of  strong  ammonia  (e.g.  25  cc.  NH4OH, 
90  to  100  cc.  of  solution).  The  solution  is  stirred  during  the  addition  and  then 
allowed  to  settle  for  at  least  two  hours.  It  is  filtered  preferably,  through  a 
Gooch  crucible  (or  through  an  ashless  filter  paper),  and  the  precipitate  washed 
with  dilute  ammonium  hydroxide,  1  :  4,  then  placed  in  a  porcelain  crucible,  a 
few  drops  of  saturated  solution  of  ammonium  nitrate  added  and  the  precipitate 
heated  over  a  low  flame  till  decomposed  (or  until  the  paper  chars).  The  lumps 
of  residue  are  broken  up  with  a  platinum  rod  and  again  ignited  over  a  Scimatico 
or  Me*ker  burner,  the  heat  being  gradually  increased.  If  the  heating  is  properly 
conducted,  the  resultant  ash  will  be  white  or  light  gray,  otherwise  it  will  be 
dark.  The  addition  of  solid  ammonium  nitrate  aids  the  oxidation  in  obstinate 
cases,  but  there  is  danger  of  slight  mechanical  loss.  The  crucible  is  cooled  in  a 
desiccator  and  the  residue  weighed  as  magnesium  pyrophosphate. 

Mg2P207X0.2787=P    and    Mg2P207  X  0.6379  =P205. 

Direct  Precipitation  of  Magnesium  Ammonium  Phosphate 

In  the  absence  of  heavy  metals  whose  phosphates  are  insoluble  in  an  ammo- 
niacal  solution,  the  magnesia  mixture  may  be  added  directly  to  the  neutral  solu- 
tion containing  the  phosphate,  without  previous  precipitation  of  ammonium 
phosphomolybdate.  The  magnesium  ammonium  phosphate  is  washed  and 
ignited  according  to  directions  given  above,  and  weighed  as  magnesium  pyro- 
phosphate. 

The  use  of  the  Gooch  crucible  for  the  ammonium  phosphomolybdate  and  the 
ammonium  magnesium  phosphate  precipitates  is  recommended  in  preference 
to  filter  paper,  as  the  fibers  of  the  latter  invariably  are  occluded  in  the  precipi- 


316 


PHOSPHORUS 


tales,  and  produce  dark-colored  residues  of  magnesium  pyrophosphate,  which  are, 
frequently,  extremely  difficult  to  burn  white.  The  residue  on  the  asbestos  mat, 
the  other  hand,  is  easily  ignited  white,  and  does  not  require  repeated 


on 


addition  of  an  oxidizing  agent,  as  is  so  often  the  case  with  precipitates  filled 
with  paper  fiber. 


VOLUMETRIC  METHODS  FOR  THE  DETERMINATION 
OF  PHOSPHORUS 

C.  Alkalimetric  Method 

The  method  is  based  on  the  acid  character  of  ammonium  phosphomolybdate, 
the  following  reaction  taking  place  with  an  alkali  hydroxide: 

2(NH4)312Mo03P04+46NaOH+H20 

=2(NH4)2HP04+(NH4)2Mo04+23Na2Mo04+23H20. 

From  the  reaction  46  molecules  of  sodium  hydroxide  are  equivalent  to  one 
molecule  of  P205,  hence  1  cc.  of  a  N/10  solution  of  sodium  hydroxide  neutralizes 
the  yellow  precipitate  containing  an  equivalent  of  .000309  gram  of  P206. 

Special  Reagents 

Sodium  Hydroxide — Tenth  Normal  Solution.  For  determination  of  phos- 
phorus by  the  alkali  volumetric  method.  To  100  grams  of  the  pure  NaOH  sticks 
sufficient  water  is  added  to  just  dissolve  the  hydrate.  This  concentrated  solu- 
tion is  poured  into  a  tall  cylinder,  the  vessel  closed  and  the  insoluble  matter  allowed 
to  settle.  The  liquid  will  be  practically  free  of  carbonates.  A  portion  of  the  clear 
liquor  may  now  be  drawn  off  and  diluted  to  a  definite  volume  so  that  the  solu- 
tion is  slightly  stronger  than  tenth  normal,  as  determined  by  titration  against 
a  standard  N/10  acid.  It  may  now  be  diluted  to  the  required  amount  as  indi- 
cated by  the  acid  titration.  Freshly  boiled  distilled  water  should  be  used  in  the 
dilutions  of  the  standard  caustic  solution.  Phenolphthalein  indicator  is  required 
in  the  titration.  The  exact  value  of  the  caustic  solution  in  terms  of  phosphorus 
may  be  ascertained  by  standardizing  the  solution  against  a  steel  sample  of  known 
phosphorus  content,  the  sample  being  dissolved  in  nitric  acid,  the  phosphorus 
precipitated  as  ammonium  phosphomolybdate,  the  washed  precipitate  dissolved 
by  the  caustic  solution  and  the  excess  caustic  titrated  by  standard  nitric  acid 
according  to  the  procedure  given  later. 

Wt.  of  P  in  sample 

f  XT  „  „ —  -77—       .  ,  ,  .    =  amount  of  P  per  cc.  of  NaOH. 

cc.  of  NaOH  required  to  neutralize  molybdate 

Nitric  Acid — Tenth  Normal  Solution.  The  acid  is  standardized  against 
the  caustic  solution  and  should  be  of  such  "strength  that  1  cc.  of  HN03  is  equal 
to  1  cc.  of  NaOH.  Phenolphthalein  indicator  is  used.  Approximately  6.7  cc. 
of  95%  HN03  diluted  to  1000  cc.  =N/10  HN03  solution. 

Nitric  Acid  for  Washing  Precipitates.  One  per  cent  solution,  14  cc.  HNOs 
(sp.gr.  1.42)  per  liter  of  water. 

Acid  Ammonium  Sulphate  for  Washing  Precipitates.  Fifteen  cc.  strong 
NH4OH+25  cone.  H2S04  in  1000  cc.  solution. 


PHOSPHORUS  317 

Potassium  Nitrate  for  Washing  Precipitates.  Used  in  volumetric  analysis 
only.  Ten  grams  of  KN03  per  liter  of  solution.  Test,  to  be  sure  the  solution 
is  neutral. 

Other  reagents  required:  NH4OH  (sp.gr.  0.90);  H2S04  (sp.gr.  1.84);  HN03 
(sp.gr.  1.42);  Na2S203  solution,  2%;  amalgamated  zinc. 

Special  Apparatus  Required 

Jones'  Reductor.  Details  of  the  reductor  are  given  under  the  determination 
of  iron  by  the  permanganate  method,  also  under  the  Volumetric  Determination 
of  Molybdenum,  pages  220  and  281. 

Procedure.  The  ammonium  phosphomolybdate,  obtained  according  to  direc- 
tions already  given  on  page  313,  is  filtered  into  a  Gooch  crucible  containing 
asbestos,  and  washed  once  or  twice  with  water  containing  1%  nitric  acid,  and  then 
several  times  with  a  1%  neutral  solution  of  potassium  nitrate  until  the  washings 
are  free  of  acid,  as  indicated  by  testing  with  litmus  paper.  The  asbestos  mat  con- 
taining the  precipitate  is  transferred  to  a  No.  4  beaker,  100  cc.  of  C02  free  water 
added,  followed  by  about  20  cc.  of  N/10  NaOH  measured  from  a  burette.  The 
crucible  is  rinsed  out  with  5  to  10  cc.  of  N/10  NaOH,  the  exact  amount  being 
noted  and  then  with  water,  adding  the  rinsings  to  the  main  solution.  Phenol- 
phthalein  indicator  is  added,  and  the  excess  of  caustic  titrated  with  N/10  HN03. 
The  total  NaOH  added  minus  the  acid  titration  equals  the  cc.  of  the  caustic 
equired  to  react  with  the  yellow  precipitate. 

One  cc.  N/10  NaOH  =0.000136  gram  P    and     =0.000309  gram  P206. 
The  exact  factor  should  be  determined  as  directed  under  Reagents. 

D.  Zinc  Reduction  and  Titration  with  Potassium  Permanganate 

This  method  is  based  on  the  assumption  that  ammonium  phosphomolybdate, 
(NH4)3l2Mo03P04,  is  reduced,  in  acid  solution,  by  zinc,  the  molybdic  acid,  Mo03, 
forming  the  lower  oxide  Mo203,  in  which  form  it  reacts  with  ferric  iron  in  the 
receiving  flask,  reducing  a  corresponding  equivalent  of  ferric  salt  to  ferrous 
condition,  being  itself  oxidized  to  MoOs.1  When  the  ferric  solution  is  not  placed 
in  the  receiving  flask  a  slight  oxidation  takes  place,  the  oxide  Mo24037,  apparently 
being  formed.2 

Potassium  Permanganate  Decinormal  Solution.  For  volumetric  determina- 
tion of  phosphorus,  reduction  method,  3.161  grams  of  the  pure  salt  per  liter  is 
the  theoretical  amount  required  for  a  tenth-normal  solution.  It  is  necessary, 
however,  to  standardize  the  permanganate  solution  against  a  tenth-normal 
sodium  oxalate  solution.  The  exact  value  of  the  permanganate  solution  may  be 
accurately  and  rapidly  determined  in  terms  of  phosphorus  by  standardizing  against 
a  sample  of  standard  steel  containing  a  known  amount  of  phosphorus,  the 
ultimate  standard  being  steel  drillings  furnished  by  the  U.  S.  Bureau  of  Standards. 
The  drillings  are  dissolved  in  nitric  acid,  oxidized  with  KMn04,  the  excess  of  the 
reagent  being  destroyed  by  thiosulphate  solution.  Ammonia  is  added  until  the 
solution  becomes  a  deep  amber  color.  The  phosphorus  is  precipitated  as 
ammonium  phosphomolybdate.  The  following  procedure  is  the  same  as  is 

1  D.  L.  Randall,  Am.  Jour.  Sci.  (4),  24,  315. 

2  Blair,  "Chemical  Analysis  of  Iron,"  7th  Ed.,  p.  96. 


318 


PHOSPHORUS 


given  in  the  volumetric  method  following:  The  permanganate  titration  of  the 
reduced  molybdic  acid  divided  into  the  amount  of  phosphorus  known  to  be 
present  in  the  solution  will  give  the  value  of  the  permanganate  in  terms  of 
phosphorus. 

Wt.  of  P  in  sample  £^*^ 

-__,   -. : — r  =  amount  of  P  per  cc.  of  KMn04. 

cc.  KMn04  required 

Procedure.  The  ammonium  phosphomolybdate,  obtained  by  the  procedure 
given  on  page  313,  is  filtered  onto  an  asbestos  mat  in  a  Gooch  crucible  or  onto 
filter  paper,  and  washed  with  dilute  HN03  followed  by  acid  ammonium  sulphate 
(15  cc.  NH4OH,  sp.gr.  0.90+25  cc.  cone.  H,S04,  sp.gr.  1.84+1000  cc.  H20),  until 
2  or  3  cc.  of  the  wash  water  gives  no  reaction  for  molybdenum  with  a  drop  of 
ammonium  sulphide  solution.  Five  or  six  washings  should  suffice. 

Reduction.  The  precipitate  is  dissolved  by  adding  about  10  cc.  ammonium 
hydroxide,  sp.gr.  0.96,  to  the  precipitate,  catching  the  solution  in  the  beaker  or 
flask  in  which  the  precipitation  was  made.  About  10  cc.  of  strong  sulphuric 
acid  is  added  to  this  solution  after  diluting  to  about  100  cc.  The  Jones  reductor 
is  prepared  as  described  for  determination  of  molybdenum  by  reduction,  page  281. 
The  receiving  flask  is  charged  with  about  25  cc.  of  ferric  alum  (100  grams  per  liter) 
and  4  cc.  syrupy  phosphoric  acid.  In  iron  and  steel  analysis  this  mixture  is  omitted. 
One  hundred  cc.  of  hot  water  followed  by  100  cc.  of  hot  dilute  sulphuric  acid 
(2.50%)  are  passed  through  the  column  of  zinc  in  the  reductor  (previously  cleaned 
by  passing  hot  dilute  H2S04  through  it).  The  phosphomolybdic  solution  is  now 
poured  through  the  reductor,  followed  by  100  cc.  2%  sulphuric  acid  and  100  cc. 
hot  water.  The  solution  as  it  is  reduced  becomes  green,  but  upon  coming  in  con- 
tact with  the  ferric  solution  produces  a  bright  red  color.  In  absence  of  ferric  solu- 
tion in  the  receiver  the  reduced  solution  appears  green  and  should  remain  clear. 
The  hot  solution  is  titrated  immediately  with  N/10  KMn04. 

Titration.  The  reduced  solution  is  poured  into  a  No.  6  beaker  and  N/10 
KMn04  added  from  a  burette,  until  a  faint  permanent  pink  color  is  produced. 
During  the  titration,  the  solution  changes  in  color  to  a  brown,  a  pinkish  yellow 
and  finally  to  pink. 

Titration  of  reduced  ferric  solution,  1  cc.  N/10  KMn04=. 0000862  P. 

Titration  in  absence  of  ferric  sulphate,  1  cc.  N/10  KMn04  =  .0000887  P. 

Calculation.  CASE  1.  Ferric  sulphate  in  the  receiver  (6Mo203+18  0  =  12Mo03 
in  the  molecule  containing  IP);  18  0  are  equivalent  to  36  H,  hence  N/10  P 
according  to  this  reaction  equals  at.wt.  P  divided  by  (36X1000)=P  for  1  cc. 
N/10  KMn04  =.0000862  g.  P. 

CASE  2.  No  ferric  salt  in  receiver.  Mo24037+35  0=24Mo03+2P. 
(35  0=70  H).  Dividing  by  2  we  get  at.wt.  P  divided  by  (35X1000)=P  for 
1  cc.  N/10  KMn04  =  . 0000887. 


PHOSPHORUS  319 


Report  of  the  Committee  on  Research  and  Analytical  Methods — 

Phosphate  Rock l 

The  following  tentative  standard  methods  for  sampling  and  determination  of 
moisture,  phosphoric  acid  and  iron  and  alumina  in  phosphate  rock  are  recommended 
to  the  Division. 

Methods  of  Sampling  and  Determination  of  Moisture 

I.  Gross  Sample.     A.  Car  Shipments.     One  hundred  pounds  sample  per  car. 

1.  Sampling  from  the  Car.     In  sampling  car  shipments  in  the  car  at  least  ten 
scoopshovelsful,  aggregating  100  Ibs.,  shall  be  taken  from  each  car  at  approximately 
equal  distances  from  each  other  so  as  to  average  the  car.     Care  shall  be  taken  to 
see  that  each  scoopful  shall  cover  the  entire  face  of  the  pile  from  floor  to  top. 

2.  Sampling  from  the  Cart  or  Barrow.     A  small  hand  scoopful  of  1  to  2  Ibs.  shall 
be  taken  from  each  cart  or  barrow  either  as  it  is  being  loaded  or  as  it  leaves  the  car. 

B.  Cargo  Shipments.     One  hundred  pounds  minimum  sample  per  vessel. 

1.  Sampling  in  Hoisting  Tub.     In  sampling  cargoes  generally  running  from  1000 
tons  upward  a  small  hand  scoopful  shall  be  taken  from  approximately  every  tenth 
tub  before  it  is  hoisted  from  the  hold. 

2.  Sampling  from  Conveyor.     If  unloading  is  being  done  with  automatic  bucket 
and  conveyor,  periodical  sections  of  the  entire  discharge  of  the  conveyor  shall  be  taken 
of  such  intervals  and  quantity  as  to  give  a  sample  equivalent  to  approximately  1  Ib. 
per  each  10  tons  of  cargo. 

3.  Sampling  from  Conveying  Vehicle.     Samples  shall  be  taken  with  a  hand  scoop 
from  various  cars  at  such  regular  intervals  and  in  such  quantities  as  to  give  approx- 
imately 1  Ib.  for  each  10  tons  of  cargo. 

II.  Laboratory  Sample.     The  resulting  gross  sample  obtained  by  any  one  oi  the 
methods  outlined  shall  be  crushed  to  pass  a  four-mesh  screen,  thoroughly  mixed  on  a 
clean,  hard  surface  and  quartered  down  to  a  10-lb.  average  sample. 

A.  Crushing.     This    10-lb.  sample  shall   all  be    crushed  to   pass  an  eight-mesh 
screen. 

B.  Mixing  and  Quartering.     This  eight-mesh  sample  shall  be   carefully   mixed 
and  quartered  down  to  two  2-lb.  samples. 

C.  Grinding.     1.  Moisture  Sample.     One  of  these  2-lb.  samples  shall  be  held  in  an 
air-tight  container.     This  sample  is  to  be  used  for  the  determination  of  moisture. 

2.  Analytical  Sample.  The  other  2-lb.  sample  shall  be  further  mixed  and  quartered 
down  to  a  2-  or  4-oz.  sample  which  is  then  to  be  ground  to  pass  a  sixty-mesh  screen 
or  preferably  a  sixty-five  mesh  screen.  This  sample  is  to  be  used  for  the  analytical 
determination. 

NOTE.  It  is  essential  that  the  taking  of  the  gross  sample  be  done  with  small 
hand  scoops  and  that  the  practice  of  taking  the  sample  in  the  hand  be  absolutely 
prohibited,  for  it  has  been  found  that  there  is  considerable  selective  action  in  the 
finer  materials  sifting  through  the  fingers  while  a  scoop  retains  the  entire  sample. 

The  dimensions  of  the  screens  referred  to  above  are  to  be  as  follows: 

No.  of  Mesh 

4  0.185  0.065 

8  0.093  0.032 

65          0.0082        0.0072 

III.  Determination  of  Moisture.     Moisture  is  to  be  determined  on  both  the 
moisture  sample  and  analytical  sample.     Of  the  moisture  sample  not  less  than  100 
grams  are  to  be  weighed  out  for  each  determination.     Of  the  analytical  sample  approx- 
imately 2  grams  are  to  be  weighed  out  for  each  determination.     Both  are  to  be  dried 
to  constant  weight  at  a  temperature  of  105°  C.  in  a  well-ventilated  oven,  preferably 
with  a  current  of  dry  air  passing  through  the  oven.     The  containers  in  which  moist- 
ure is  determined  should  be  provided  with  well-fitting  covers  so  that  the    samples 
may  be  cooled  and  weighed  in  the  well-covered  container. 

1  Journ.  Ind.  and  Eng.  Chem. 


320 


PHOSPHORUS 


IV.  Calculation  of  Results.  The  percentages  of  phosphoric  acid  and  iron  and 
alumina  as  determined  on  the  analytical  sample  are  to  be  calculated  to  a  moisture- 
free  basis  and  subsequently  to  the  basis  of  the  original  sample  as  shown  by  the  moist- 
ure content  of  the  moisture  sample. 

Determination  of  Phosphoric  Acid 

Reagents.  To  be  prepared  as  in  Official  Methods,  A.  O.  A.  C.  Bureau  of  Chemistry, 
Bulletin  107  (Rev.),  1910,  p.  2.  Preparation  of  reagents  (c),  (d),  (e)  and  (/),  except 
that  the  ammonium  nitrate  solution  in  (d)  is  changed  to  5%  instead  of  10%. 

Method  of  Solution.  To  5  grams  of  the  sample  add  30  cc.  of  cone,  hydrochloric 
acid  (sp.gr.  1.20)  and  10  cc.  of  cone,  nitric  acid  (sp.gr.  1.42)  and  boil  down  to  a 
syrupy  consistency.  The  residue,  which  should  be  nearly  solid  after  cooling,  is  taken 
up  with  5  cc.  of  cone,  nitric  acid  and  50  cc.  of  water.  Heat  to  boiling,  cool,  filter 
and  make  up  to  500  cc.  through  the  filter.  This  procedure  eliminates  practically 
all  of  the  silica  and  it  is  necessary  to  filter  as  quickly  as  possible  after  digestion  so 
as  to  avoid  redissolving  the  silica. 

Determination.  Draw  off  an  aliquot  portion  of  50  cc.,  corresponding  to  0.5  gram, 
neutralize  with  ammonia,  then  add  nitric  acid  until  the  solution  is  just  clear.  Add 
15  grams  of  ammonium  nitrate  (free  from  phosphates),  heat  the  solution  to  50°  C. 
and  add  150  cc.  of  molybdate  solution.  Digest  at  50°  C.  for  fifteen  minutes  with 
frequent  stirring.  Filter  off  the  supernatant  liquid  and  test  the  filtrate  with  molyb- 
date solution  to  see  if  precipitation  has  been  complete.  (If  not,  add  more  molybdate 
to  the  filtrate  and  digest  for  fifteen  minutes  longer.)  Wash  with  5  per  cent  ammonium 
nitrate  solution  by  decantation,  retaining  as  much  of  the  precipitate  as.  possible  in  the 
beaker.  Dissolve  the  precipitate  in  the  beaker  in  the  least  possible  quantity  of  ammo- 
nium hydroxide  (sp.gr.  0.90)  and  dilute  this  solution  with  several  times  its  volume 
of  hot  water.  Dissolve  the  remainder  of  the  precipitate  on  the  filter  with  this  solu- 
tion, washing  beaker  and  filter  with  hot  water  and  keeping  the  volume  of  the  filtrate 
between  75  and  100  cc.  Neutralize  with  hydrochloric  acid,  cool  to  room  tempera- 
tuie  and  add  25  cc.  of  magnesia  mixture  from  a  burette,  drop  by  drop,  stirring 
vigorously  with  a  rubber-tipped  rod,  then  add  15  cc.  of  ammonium  hydroxide  (sp.gr. 
0.90)  and  allow  to  stand  for  four  hours  or  overnight  at  room  temperature.  The  time 
of  standing  may  be  reduced  to  two  hours  if  kept  in  a  refrigerator  or  still  better  in  an 
ice-water  bath.  Filter  through  a  platinum  or  porcelain  Gooch  crucible,  fitted  with 
a  platinum  or  asbestos  mat  carefully  made  and  ignited  to  constant  weight.  Wash 
with  2.5%  ammonium  hydroxide  until  practically  free  from  chlorides;  dry,  ignite, 
cool  and  weigh  as  magnesium  pyrophosphate.  If  desired,  filtration  may  be  made 
through  an  ashless  filter  paper,  igniting  in  the  usual  manner.  Calculate  to  P2O6  by 
multiplying  by  0.6378  (log  80468). 

Determination  of  Iron  and  Aluminum  together  as  Phosphates 

1.  Solutions  Required:     1.  Hydrochloric  acid  (1  :  1);   prepared  by  mixing  1  part 
by  volume  of  concentrated  HC1  (sp.gr.  1.19)  with  1  part  of  distilled  water. 

2.  A  saturated  solution  of  ammonium  chloride,  which  should  be  filtered  before 
use. 

3.  A  25%  solution  of  ammonium  acetate,  faintly  acid  to  litmus  paper. 

4.  A  solution  of  ammonium  phosphate  (10%),  prepared  by  dissolving  20  grams  of 
(NH4)2HPO4  in  180  cc.  of  distilled  water  and  filtering.     (This  should  be  prepared 
frequently  in  small  quantity,  as  it  attacks  glass  containers  on  standing.) 

5.  A  standard  solution  of  ferrous  ammonium  sulphate,  containing  iron  equivalent 
to  about  0.0100  gram  of  Fe2O3  in  10  cc.  and  50  cc.  cone.  HC1  per  liter. 

6.  A  solution  of  calcium  and  magnesium  phosphates  for  blank  determinations, 
prepared  as  follows:   Dissolve  4  grams  of  MgO  and  35  grams  of  CaCOs  (both  free 
of  iron  and  aluminum)  in  100  cc.  concentrated  HC1,  add  an  aqueous  solution  of  30 
grams  of  (NH4)2HPO4,  make  up  to  2  liters  and  filter. 

7.  A  solution  of  ammonium  nitrate  (5%)  for  washing  precipitates.     About  400  cc. 
are  required  for  each  determination. 

All  reagents  used  should  be  as  pure  as  practicable  and  all  solutions  should  be  free 
of  suspended  matter. 

II.  Preparation  of  Rock  Solution.  Place  2.5  grams  of  pulverized  rock  with  50  cc. 
of  1  :  1  HC1  in  a  graduated  250-cc.  flask,  the  glass  of  which  contains  less  than  1% 


PHOSPHORUS  321 

of  iron  and  aluminum  oxides.1  Boil  gently  with  occasional  shaking  for  one  hour  in 
such  a  manner  as  to  avoid  concentrating  the  solution  to  less  than  half  of  its  original 
volume,2  dilute,  cool  to  room  temperature,  make  up  to  volume  and  mix;  filter 
immediately  through  a  dry  filter  into  a  dry  flask,  discarding  the  first  few  cc.  of  the 
filtered  solution. 

Pipette  a  50-cc.  aliquot,  representing  0.5  gram  of  rock,  into  a  platinum  dish  and 
evaporate  nearly  to  dryness.3  Cool,  take  up  with  a  few  cc.  of  water  and  when  the 
salts  are  loosened  from  the  dish,  add  5  cc.  of  1:1  sulphuric  acid  and  evaporate  to 
fumes.  Increase  the  temperature  and  evaporate  nearly  to  dryness.4  Cool,  dilute 
with  about  50  cc.  of  distilled  water,  add  10  cc.  of  cone.  HC1  and  heat,  with  occasional 
stirring,  until  sulphates  are  dissolved.  Filter  into  a  600-cc.  Jena  glass  beaker  through 
a  9-cm.  paper  (S.  &  S.  No.  597),  washing  the  paper  thoroughly  with  dilute  HC1  and 
hot  water. 

III.  First  Precipitation  with  Ammonium  Acetate.  To  the  solution  in  the  beaker, 
add  25  cc.  of  the  standard  iron  solution  when  the  amount  of  combined  iron 
aluminum  oxides  in  the  rock  does  not  exceed  5%  and  50  cc.  of  the  standard  iron 
solution  when  the  combined  oxides  exceed  5%.5  Oxidize  with  about  3  cc.  of  bromine 
water  and  boil  in  covered  beaker  for  about  fifteen  minutes  to  expel  the  excess  of 
bromine.  Rinse  cover  and  sides  of  beaker  with  distilled  water  and  cool  to  room  tem- 
perature. 

(Run  a  blank  determination  containing  10  cc.  of  1  :  1  HC1,  25  cc.  of  the  calcium 
and  magnesium  phosphate  solution,  and  the  same  quantity  of  standard  iron  solution 
as  is  added  to  the  rock  solution.) 

Add  100  cc.  of  saturated  ammonium  chloride  solution,6  3  cc.  of  10%  ammonium 
phosphate  solution,  2  drops  of  methyl-orange  indicator  and  cone,  ammonium  hydrate 
(free  of  spangles  and  dissolved  mineral  matter)  to  alkaline  reaction.  Then  add 
dilute  HC1  (about  1  :  20)  drop  by  drop,  with  constant  stirring,  until  the  solution 
becomes  faintly  acid  and  the  pink  color  of  the  methyl  orange  is  just  restored.7 
Dilute  to  450  cc.8  with  distilled  water,  heat  to  boiling,  and  add  25  cc.  of  25%  ammo- 
nium acetate  solution.  Continue  heating  for  about  five  minutes,  after  adding  ammo- 
nium acetate,  filter  on  a  12.5  cm.  ashless  filter  paper  (S.  &  S.  No.  589  "  White  Ribbon  " 

1  Experiments  have  shown  that  the  solution  cannot  be  made  in  flasks  made  of  glass 
containing  a  higher  percentage  of  alumina,  because  the  fluorine  in  the  rock  partially 
dissolves  the  glass  and  adds  alumina  to  the  solution.     Neither  "  Nonsol,"  "  Jena  " 
nor  "  Weber's  "  resistant  glass     "  R  "  is  suitable.     Flasks  made  of  glass  containing 
little  alumina,  such  as  "  Kavalier,"    "  F  Z  resistant  glass  "   or  other  Bohemian  glass 
of  lower  alumina  content  have  proven  satisfactory.    See  "  Chemical  Glassware." 
P.  H.  Walker,  J.  Am.  Chem.  Soc.,  27,  865. 

2  This  may  be  accomplished  by  heating  the  flask  over  a  low  Bunsen  flame  or  on  a 
hot  plate  which  is  just  hot  enough  to  keep  the  solution  boiling.     A  glass  tube  about 
12  ins.  long  by  f  in.  in  diameter  with  a  bulb  in  the  middle  makes  a  very  satisfactory 
condenser  when  placed  in  the  neck  of  the  flask.  « 

3  It  is  advisable  to  remove  as  much  of  the  HC1  as  possible  before  adding  sulphuric 
acid  so  as  to  minimize  the  chances  of  loss  by  effervescence  or  bumping.     The  evapo- 
ration may  be  conducted  in  glass  beakers  of  low  alumina  content.     Kavalier  glass  has 
been  used  satisfactorily.    In  no  case  should  the  evaporation  be  conducted  in  por- 
celain. 

4  It  is  best  to  remove  as  much  sulphuric  acid  as  possible  so  that  the  calcium  sulphate 
which  might  hold  iron  will  dissolve  readily  in  HC1. 

5  It  has  been  found  that  when  iron  oxide  is  present  in  considerable  excess  over 
aluminum  oxide  the  precipitation  of  the  phosphates  is  more  complete,  the  combined 
phosphates  are  more  readily  ignited  to  constant  weight,  and  the  precipitate  does 
not  become  red  on  ignition. 

•Ammonium  chloride  in  large  quantity  increases  the  solubility  of  calcium  and 
magnesium  phosphates  and  decreases  the  solubility  of  iron  and  aluminum  phosphates. 

7  This  method  of  adjusting  acidity  was  suggested  by  F.  B.  Carpenter  and  was 
found  to  give  satisfactory  results. 

8  All  our  work  has  confirmed  Brown's  statement  (see  Wiley's  "  Principles  and 
Practice  of  Agricultural  Analysis,"  2d  edition,  1908,  Vol.  II,  p.  245)  that  the  sepa- 
ration from  calcium  under  the  conditions  of  the  method  depends  upon  sufficient 
dilution. 


322 


PHOSPHORUS 


is  suitable),  in  a  3-in.  rapid  filtering  funnel,  keeping  the  contents  of  the  beaker  and  fun- 
nel hot.1  Wash  three  times  with  hot  5%  ammonium  nitrate  solution,  each  time  cut- 
ting the  precipitate  loose  from  the  filter  and  stirring  it  thoroughly  with  the  stream 
from  the  wash  bottle  and  filling  to  within  about  i  in.  of  its  upper  edge.  About  30  cc. 
are  required  for  each  washing.  Return  the  precipitate  to  the  precipitating  beaker 
by  washing  it  out  of  the  filter  with  a  stream  of  hot  water.  Dissolve  the  precipitate 
with  dilute  HC1  (1  :  6),  pouring  about  50  cc.  through  the  filter  in  successive  washings 
and  using  about  25  cc.  to  wash  down  inside  the  beaker.  Finish  filter  paper  with 
distilled  water. 

IV.  Second  Precipitation  with  Ammonium  Acetate.    Cool  the  solution   to  room 
temperature,  add  50  cc.  saturated  ammonium  chloride  solution,  4  cc.  of  10%  ammo- 
nium phosphate  solution,  2  drops  of  methyl  orange,  and  adjust  acidity  as  before. 
Dilute  to  300  cc.  with  distilled  water.     Heat  to  boiling,  add  15  cc.  of  25%  ammonium 
acetate  solution  and  continue  heating  for  about  five  minutes.     Filter  on  the  same  paper 
as  used  for  the  first  filtration,  scrubbing  the  inside  of  the  beaker  with  a  rubber-tipped 
stirring  rod  and  rinsing  with  hot  5%  ammonium  nitrate  solution.     Wash  the  pre- 
cipitate ten  times  with  hot  5%  ammonium  nitrate  solution,  each  time  cutting  the 
precipitate  loose,  stirring  it  thoroughly  as  before  and  breaking  up  all  lumps  that  it  may 
contain.    About  300  cc.  of  wash  solution  are  required. 

As  a  precautionary  measure,  boil  the  filtrate  and  washings  from  both  the  first 
and  second  precipitates,  and  recover  any  additional  precipitate. 

V.  Ignition  of  Precipitate.    Transfer  filter  with  precipitate  to  a  weighed  deep- 
form  porcelain  crucible  (40  mm.  in  diameter  is  a  good  size)  and  heat  gently  over  a  low 
flame  until  the  contents  are  dry,  increase  the  temperature  a  little  and  continue  heating 
until  the  paper  is  charred,  increase  the  temperature  again  and  continue  heating  until 
the  paper  is  entirely  burned.     Ignite  the  uncovered  2   porcelain  crucible  for  one-hour 
periods  over  blast  lamp  No.  4  Meker  burner  to  constant  weight,  each  time  cooling  to 
room  temperature  in  desiccator  before  weighing.     Deduct  the  weight  of  blank  from 
each  determination,  and  after  subtracting  the  weight  of  FePO4  equivalent  to  the 
amount  of  iron  found  in  0.5  gram  of  rock  by  titration.  calculate  the  remainder  to 
A12O8.    A1PO4X0.4184=A12O3. 

Determination  of  Iron 

1.  Solutions    Required.     1.  Standard    Potassium    Permanganate,    N/40,    contain- 
ing 0.79015  gram  of  KMnO4  per  liter,  and  having  a  value  of  0.001996  (or  practically 
0.002)  gram  of  Fe2O3  per  cc.     Standardize  with  pure  sodium  oxalate   (Bureau  of 
Standards  standard  sample  No.  40.) 

2.  Stannous  Chloride.     Dissolve  50  grams  of  the  crystallized  salt  in  100  cc.  of 
hot  cone.  HC1  and  make  up  to  1  liter  with  distilled  water. 

3.  Mercuric  Chloride.    Prepare  a  cold  saturated  solution. 

4.  Manganese  Solution.     (Preventive  solution):    (a)  Dissolve  200  grams  of  crys- 
tallized manganese  sulphate  in  1000  cc.  of  water.     (6)  Pour  slowly,  with  constant 
stirring,  400  cc.  of  cone,  sulphuric  acid  into  600  cc.  of  water  and  add  1000  cc.  of  phos- 
phoric acid  of  1.3  sp.gr.     Mix  solutions  (a)  and  (6). 

II.  Analytical  Procedure.  Determine  iron  according  to  Jones'  and  Jeffrey's 
modification  of  the  Zimmermann-Reinhardt  method  3  as  follows:  Place  in  a  250-cc. 
beaker  an  aliquot  of  the  rock  solution,  containing  not  more  than  5  cc.  of  cone. 
HC1,  boil  and  reduce  with  the  smallest  possible  excess  of  stannous  chloride,  added 
drop  by  drop  while  agitating  the  solution.  Wash  sides  of  beaker  with  distilled 
water  and  cool  rapidly.  Add  10  cc.  of  mercuric  chloride  solution  and  stir  vigor- 
ously for  about  thirty  seconds.4  Pour  the  mixture  into  a  large  porcelain  casserole 
or  dish  containing  20  cc.  of  the  manganese  solution  in  about  500  cc.  of  water  which 
has  just  been  tinted  with  the  permanganate  solution. 

1  The  contents  of  the  funnel  will  remain  hot  if  the  solution  in  the  beaker  is  kept 
hot  over  a  low  flame  and  filtration  is  fairly  rapid. 

2  Heat  over  Bunsen  to  redness  before  placing  over  blast  in  order  to  prevent  loss 
of  precipitate  by  blowing  out  of  crucible. 

» Analyst,  34  (1909),  306. 

4  Barneby  has  shown  that  only  a  short  interval  of  time  is  necessary  between  the 
addition  of  mercuric  chloride  and  manganese  sulphate,  if  the  solution  is  thoroughly 
agitated.  J.  Am.  Chem.  Soc.,  36  (1914). 


PHOSPHORUS 


323 


Titrate  with  N/40  permanganate  solution,  to  original  tint  and  correct  result  by  the 
volume  of  KMnC>4  required  for  a  blank  containing  the  same  quantity  of  HC1  (diluted), 
adding  2  or  3  drops  of  stannous  chloride  to  the  hot  solution,  cooling,  adding  10  cc. 
of  mercuric  chloride  and  titrating  similarly. 

When,  the  rock  solution  contains  carbonaceous  matter  it  is  necessary  first  to 
oxidize  this  with  a  little  potassium  chlorate,  evaporate  to  dryness  to  eliminate  chlorine, 
and  redissolve  with  5  cc.  cone.  HC1  and  about  10  cc.  of  water. 

Calculate  the  Fe2O3  found  to  FePO4,  using  the  factor  1.8898,  and  after  deducting 
from  the  weight  of  combined  phosphates  found,  calculate  the  difference  (A1PO4) 
to  A12O3. 


FIG.  55a. — Christian  Becker  Chainomatic  Balance. 

The  chain  balance  shown  in  Fig.  55a  is  of  the  usual  construction  of  the  analytical  or 
laboratory  balances  as  far  as  knife  edges,  bearings,  etc.,  are  concerned,  with  the  exception 
that  there  is  no  rider  and  consequently  no  graduations  on  the  beam.  One  end  of 
the  weighing  chain  is  hung  from  an  arm  of  the  scale  beam,  and  the  other  end  from 
a  slide-block  which  is  moved  up  and  down  on  a  vertical  graduated  scale.  As  this 
block  is  raised,  more  of  the  weight  of  the  chain  is  taken  from  the  beam  and  hangs 
from  the  slide-block  which  forms  a  stationary  support  for  holding  the  inactive  part 
of  the  chain.  As  the  slide  is  lowered  a  greater  proportion  of  the  weight  of  the  chain 
is  transferred  to  the  beam.  By  means  of  this  chain  and  vernier  device,  after  all  the 
necessary  large  weights  up  to  50  milligrams  are  placed  on  the  pan,  the  weighing  from 
50  milligrams  to  TV  of  a  milligram  can  be  concluded  without  opening  the  balance  or 
using  the  arrest,  eliminating  the  necessity  of  reading  and  replacing  all  small  weights  or 
the  handling  of  a  rider,  with  a  consequent  enormous  saving  of  time.  The  editor  has  used 
the  Becker  chainomatic  balance  for  over  a  year  and  has  found  it  highly  satisfactory. 


PLATINUM 

R.    E.    HlCKMAN1 

Pt,af.tttf.l95.3;  sp.gr.  31.48;  m.p.!755°C.;  oxides  PtO,  PtO, 

DETECTION 

Platinum  is  a  gray,  lustrous,  soft  and  malleable  metal.  It  is  not  altered  by 
ignition  in  the  air,  but  fuses  in  the  oxy-hydrogen  flame.  It  does  not  dissolve  in 
any  of  the  single  acids,  but  a  fusion  with  acid  potassium  sulphate  attacks  the  metal 
slowly.  The  action  of  chlorine  in  general,  and  nitro-hydrochloric  acid  (aqua 
regia),  the  main  solvent,  converts  the  metal  to  hydrochlorplatinic  acid,  H2PtClc, 
which  forms  many  double  salts,  or  platinochlo rides.  If  platinic  chloride  is  gently 
heated  it  breaks  up  into  platinous  chloride,  PtCl2,  and  chlorine. 

If,  however,  the  platinum  is  alloyed  with  silver,  it  dissolves  in  nitric  acid  to  a 
yellow  liquid,  provided  sufficient  silver  is  present  in  the  alloy. 

The  oxides  can  be  formed  by  carefully  igniting  the  corresponding  hydroxides. 
These  are  very  unstable,  decomposing  into  metal  and  oxygen  by  gentle  ignition. 

The  chlorides  are  the  most  important  compounds  of  platinum.  Two  complex 
acids  are  formed  with  hydrochloric  acid  when  the  metal  is  dissolved  in  aqua 
regia. 

PtCl4-f2HCl=H2PtCl6  (hydrochlorplatinic  acid),  orange-red  crystals. 
PtCl2+2HCl=H2PtCl4  (hydrochlorplatinous  acid),  only  known  in  solution. 

An  aqueous  solution  of  the  former  is  yellowish-orange,  while  an  aqueous  solution 
of  the  latter  is  dark  brown,  the  former  being  by  far  the  more  important. 

Potassium  iodide  precipitates  platinum  iodide,  but  it  dissolves  quite  readily, 
giving  a  pink  to  a  dark  blood-red  liquid,  depending  on  the  concentration  of  the 
solution.  Nitric  acid  should  be  absent.  Heat  destroys  this  color,  as  well  as 
hydrogen  sulphide,  sodium  thiosulphate  and  sulphite,  sulphurous  acid,  mercuric 
chloride  and  certain  other  reagents. 

Hydrogen  sulphide  precipitates  black  platinum  disulphide,  PtS2,  with  the 
other  elements  of  the  hydrogen  sulphide  group.  The  solution  should  be  warm, 
as  precipitation  takes  place  more  quickly.  It  is  difficultly  soluble  in  ammonium 
sulphide.  It  will  be  found  in  the  extract  with  the  arsenic,  antimony,  tin,  gold, 
molybdenum,  etc.,  and  is  precipitated  with  these  elements  upon  addition  of  hydro- 
chloric acid.  Platinum  sulphide  is  soluble  in  aqua  regia. 

Ammonium  chloride  added  to  a  concentrated  solution  of  platinum  chloride 
precipitates  yellow  (NEU^PtCU,  which  is  slightly  soluble  in  water,  but  insoluble 
in  dilute  ammonium  chloride  solution  and  alcohol. 

Potassium  chloride  precipitates  yellow  K2PtCl6,  which  is  difficultly  soluble 
in  water,  but  insoluble  in  75%  alcohol. 

1  Chief  Chemist,  J.  Bishop  &  Co.  Platinum  Works. 
324 


PLATINUM  325 

Ferrous  sulphate  precipitates  metallic  platinum  on  boiling  from  a  neutral 
solution.  Neutralize  with  Na2C03.  Free  mineral  acids  prevent  the  precipita- 
tion (difference  from  gold). 

Stannous  chloride  does  not  reduce  platinum  chloride  to  metal,  but  reduces 
hydrochlorplatinic  acid  to  hydrochlorplatinous  acid. 

H2PtCl6+SnCl2  =H2PtCl4+SnCl4. 

Oxalic  acid  does  not  precipitate  platinum  (difference  from  gold). 

Sodium  hydroxide  with  glycerine  reduces  hydrochlorplatinic  acid  on  warm- 
ing to  black  metallic  powder. 

Formic  acid  precipitates  from  neutral  boiling  solutions  all  the  platinum  as 
a  black  metallic  powder. 

Thallium  protoxide  precipitates  from  the  platinum  bichloride  solution  a  pale 
yellow  salt,  thallium  platinochloride.  When  the  salt  is  heated  to  redness  it 
leaves  an  alloy  of  thallium  and  platinum. 

Rubidium,  caesium  and  thallium  chlorides  yield  similar  insoluble  salts 
with  platinum  chloride. 

Sodium  hydroxide  added  to  platinic  chloride  and  then  supersaturating  with 
acetic  acid  produces  a  reddish-brown  precipitate  of  platinic  hydroxide  Pt(OH)4. 
This  dissolves  in  acids  readily,  except  acetic  acid. 

Metallic  zinc,  magnesium,  iron,  aluminum  and  copper  are  the  most 
important  metals  that  precipitate  metallic  platinum. 

H2PtCl6-f  3Zn  =3ZnCl2-fH2+Pt. 

ESTIMATION 

Platinum  may  be  present  under  the  following  conditions: 

1.  Native  grains  usually  accompanied  by  the  other  so-called  platinum  metals, 
iridium,  palladium,  ruthenium,  rhodium,  osmium,  and  gold  and  silver  (alloyed 
with  one  or  more  of  the  allied  metals). 

Ore  concentrates  containing  the  native  grains  as  above  with  the  base  metals, 
iron,  copper,  chromium,  titanium,  etc.  The  associated  minerals  high  in  specific 
gravity  in  the  gravels  may  be  expected  to  appear  with  the  platinum  nuggets, 
such  as  chromite,  magnetite,  garnet,  zircon,  rutile,  small  diamonds,  topaz,  quartz, 
cassiterite,  pyrite,  epidote,  and  serpentine;  with  gold  in  syenite;  ores  of  lead  and 
silver. 

2.  Scrap  platinum   containing,  oftentimes,  palladium,   iridium,   gold,   silver 
and  iron. 

3.  Small  amounts  of  platinum  in  the  presence  of  large  amounts  of  iron, 
silica,   carbon,   magnesia:    platinum   residues,   nickel   and   platinum   contacts, 
photography  paper,  jewelers'  filings  and  trimmings,  dental  and  jewelers'  sweeps 
and  asbestos,  etc. 

4.  Platinum  alloyed  with  silver,  gold,  tungsten,  nickel,  copper,  lead,  etc. 

5.  Platinum  solutions  and  salts. 

Preparation  and  Solution  of  the  Sample 

The  best  solvent  for  platinum  is  aqua  regia.  The  metal  is  also  acted  upon  by 
fusion  with  the  fixed  alkalies — sodium  or  potassium  hydroxide  and  sodium  per- 
oxide or  potassium  or  sodium  nitrate;  also  by  fusion  with  acid  potassium  sul- 


326 


PLATINUM 


phate.  Platinum  alloys  when  highly  heated  with  other  metals,  as  lead,  tin,  bis- 
muth, antimony,  silver,  gold,  copper,  etc.  The  element  dissolves  in  nitric  acid 
when  alloyed  with  silver.  This  gives  a  method  for  the  determination  of  gold 
in  the  presence  of  silver  and  platinum  alloy. 

All  salts  of  platinum  are  soluble  in  water.  The  less  soluble  salts  are  the  chloro- 
platinates  of  potassium,  ammonium,  rubidium,  and  caesium.  Heat  increases 
the  solubility  while  the  presence  of  alcohol  decreases  the  solubility. 

Ores.  When  the  free  grains  of  platinum,  gold  and  osmiridium  are  desired 
the  following  method  is  recommended:  Five  to  10  grams  of  the  ore  are  taken 
from  a  well-mixed  pulverized  sample  and  placed  in  a  large  platinum  dish  that  has 
been  weighed.  Twenty-five  to  50  cc.  of  strong  hydrofluoric  acid  together  with 
5  to  10  cc.  of  concentrated  sulphuric  acid  is  mixed  with  the  ore  in  the  dish  and 
evaporated  on  the  water  bath,  when  SiF4  and  the  excess  of  HF  are  expelled. 
The  material  is  gently  heated  until  S03  fumes  are  given  off.  This  is  repeated 
with  HF  if  necessary.  The  material  is  washed  into  a  casserole  with  about  200  cc. 
of  hot  water  and  digested  over  a  water  bath  for  fifteen  or  twenty  minutes,  and  is 
then  washed  by  decantation,  several  times  pouring  the  supernatant  liquor  through 
a  filter  to  save  any  floating  material  that  might  be  washed  out.  The  filter  is 
cautiously  burned  and  the  residue  is  added  to  the  unattacked  material.  This  is 
transferred  from  the  dish  to  a  beaker  or  a  porcelain  dish  and  treated  with  aqua 
regia.  The  platinum  and  a  small  amount  of  iridium  that  dissolves  with  the 
platinum  on  account  of  its  being  alloyed  can  be  precipitated  with  ammonium 
chloride.  The  remaining  residue  in  the  dish  will  be  a  small  amount  of  sane!  and 
osmiridium.  The  silica  is  driven  off  with  HF  as  described  above  and  the  bright 
grains  weighed  as  osmiridium,  or  the  sand  and  osmiridium  are  run  down  in  a 
scorifier  with  lead,  and  the  lead  dissolved  in  dilute  nitric  acid,  leaving  the  osmirid- 
ium grains  free  from  sand. 

Platinum  Scrap.  One-half  gram  to  a  gram  is  dissolved  in  aqua  regia  and 
evaporated  with  HC1  to  get  rid  of  the  HN03. 

If  the  platinum  is  alloyed  with  a  large  amount  of  copper,  silver,  lead  and 
other  impurities,  a  sample  of  1  to  5  grams  is  dissolved  in  15  to  25  cc.  of  HN03, 
whereby  the  copper,  silver,  lead  and  other  impurities  alloyed  with  the  platinum 
as  well  as  a  large  amount  of  platinum  will  dissolve.  The  residue  after  washing 
will  be  platinum  and  gold.  These  are  dissolved  in  aqua  regia  as  described  above 
and  the  platinum  precipitated  with  ammonium  chloride.  The  platinum  is 
recovered  from  the  nitric  acid  solution  and  added  to  the  aqua  regia  solution  and 
the  whole  is  evaporated  to  get  rid  of  the  HN03. 

Small  Amounts  of  Platinum  in  the  Presence  of  Large  Amounts  of  Iron ; 
Iron  Scale,  Fe2O3;  Sulphate  of  Iron,  Magnesia,  Sulphate  of  Magnesia, 
Silica,  etc.  The  material  is  carefully  weighed  and  the  coarse  scales  are  sepa- 
rated from  the  finer  material  containing  the  platinum  by  passing  the  fines  through 
a  20-in.  mesh  or  finer  wire  sieve.  The  coarse  scale  seldom  contains  platinum, 
but  it  is  advisable  to  quarter  this  down  to  1  kilogram  or  a  fairly  good-sized  sample 
and  test  for  platinum  on  a  portion  of  the  ground  sample.  This  can  be  tested 
by  a  wet  or  a  fire  assay.  The  fines  are  quartered  down  to  about  1  kilogram  and 
ground  to  pass  a  60-  to  80-in.  mesh  sieve.  One  hundred  to  500  grams  of  the 
material  are  taken  for  analysis.  This  is  placed  in  one  or  more  casseroles,  depend- 
ing on  the  amount  taken.  Each  100-gram  portion  is  extracted  by  digestion  on 
the  steam  bath  with  about  300  to  400  cc.  of  10%  H2S04.  The  iron,  magnesia, 
etc.,  soluble  in  H2S04  will  go  into  solution,  leaving  the  platinum  with  the 


PLATINUM  327 

insoluble  residue.  Filter  (a  Biichner  funnel  may  be  necessary)  and  wash  the 
residue  with  water.  Test  the  filtrate  for  platinum  and  if  any  is  present  precipi- 
tate with  zinc  as  described  below. 

After -the  filter  is  ignited  in  a  large  platinum  dish,  the  residue  is  moistened 
with  H2S04,  and  HF  is  added  completely  covering  the  material.  The  solution 
is  evaporated  on  the  water  bath  until  S03  fumes  are  given  off.  If  necessary, 
repeat  the  treatment  with  H2S04  and  HF  until  all  the  silica  is  driven  off  as  SiF4. 
The  residue  is  transferred  to  a  casserole  and  digested  with  aqua  regia  according 
to  directions  given  under  Ores  and  Platinum  Scrap.  It  is  sometimes  very  dif- 
ficult to  precipitate  all  of  the  platinum  in  the  presence  of  a  large  amount  of 
iron,  magnesia,  etc.,  not  having  the  solution  concentrated  enough  for  the  plati- 
num. It  is  advisable  to  reduce  the  platinum  by  iron  or  zinc,  filter,  wash  with 
water  and  redissolve  the  black  metallic  platinum  in  aqua  regia.  The  HN08 
is  expelled  by  evaporation  and  adding  concentrated  HC1  from  time  to  time  and 
finally  the  platinum  is  precipitated  with  ammonium  chloride. 


SEPARATIONS 

A  careful  review  of  the  paragraph  on  Detection  will  be  very  helpful  often- 
times in  making  separations  from  other  metals  and  substances. 

Separation  of  Platinum  from  Gold.  The  platinum  is  precipitated  first  with 
ammonium  chloride,  as  (NH4)2PtCl6.  After  the  precipitate  has  settled  it  is 
filtered  and  washed  free  from  gold  with  dilute  ammonium  chloride  solution  and 
alcohol.  The  gold  is  precipitated  with  a  concentrated  solution  of  ferrous  sul- 
phate or  iron  protochloride  as  metallic  gold. 

Oxalic  acid  precipitates  the  gold,  leaving  the  platinum  in  solution.  The  oxalic 
acid  is  added  and  the  solution  boiled  until  the  gold  is  entirely  precipitated. 
Filter  and  wash  the  precipitate  of  metallic  gold  free  from  platinum.  The  filtrate 
is  evaporated  as  far  as  possible  without  crystallizing,  and  the  platinum  is  pre- 
cipitated with  ammonium  chloride  as  (NH4)2PtCl6,  or  it  may  be  reduced  with 
zinc  and  the  black  dissolved  in  aqua  regia  and  treated  as  described  above. 

Separation  of  Platinum  from  Iridium.  The  platinum  and  the  iridium  are 
precipitated  by  iron  or  zinc  and  the  black  residue  is  washed  free  from  impurities 
and  the  platinum  is  dissolved  in  dilute  aqua  regia  with  gentle  heating,  leaving 
the  iridium  as  metallic  iridium.  The  platinum  solution  is  evaporated  as  described 
above  and  precipitated  with  NH4C1  as  (NH4)2PtCl«. 

If  the  platinum  and  iridium  are  precipitated  together,  the  salt  is  filtered  and 
washed  with  ammonium  chloride  solution  and  finally  ignited.  The  sponge  is 
redissolved  and  evaporated  as  above  to  expel  the  HN03.  The  platinum  and  the 
iridium  are  precipitated  with  NaOH,  which  brings  down  the  platinum  and  iridium 
as  Pt(OH)4  and  Ir(OH)4.  Boil  this  mixture  with  alcohol,  which  reduces  the 
Ir(OH)4  to  Ir(OH)3,  but  does  not  affect  the  Pt(OH)4.  Dissolve  these  hydroxides 
in  HC1,  forming  PtCl4  and  IrCl3  in  solution,  and  the  platinum  is  precipitated  with 
NH4C1  free  from  iridium. 

Separation  of  Platinum  from  Palladium.  The  platinum  and  the  palladium 
are  reduced  with  zinc  and  the  black  residue  treated  with  HN03.  The  palladium 
goes  into  solution,  leaving  the  platinum  as  a  black  metallic  residue. 

The  black  residue  of  platinum  and  palladium  can  be  dissolved  in  aqua  regia 
and  the  solution  evaporated  with  additions  of  HC1  to  get  rid  of  the  nitric  acid. 


328  PLATINUM 

The  platinum  is  precipitated  with  NH4C1  and  filtered.  The  filter  is  washed  free 
from  palladium. 

Separation  of  Platinum  from  Ruthenium.  From  the  chloride  of  platinum 
and  ruthenium  the  metals  are  precipitated  with  ammonium  or  potassium  chloride 
wid  filtered.  The  filter  is  washed  with  dilute  ammonium  chloride  solution  or 
dilute  potassium  chloride  solution  and  alcohol  until  free  from  ruthenium.  If 
a  large  quantity  is  handled  it  may  be  necessary  to  ignite  to  platinum  sponge  and 
dissolve  in  aqua  regia,  expel  the  HN03  as  described  above,  and  reprecipitate 
with  NH4C1,  filter  and  wash  free  from  ruthenium. 

Separation  of  Platinum  from  Rhodium.  The  rhodium  salt,  like  the  ruthe- 
nium salt,  is  soluble  and  can  be  washed  from  the  platinum  salt,  (XH4)2PtCl6,  as 
under  Separation  of  Pt  from  Ru. 

Separation  of  Platinum  from  Osmium.  Both  metals  are  reduced  with 
zinc  as  a  fine  black  powder.  The  metallic  residue  is  washed  and  carefully  ignited 
at  a  high  temperature  under  a  hood,  as  the  fumes  are  poisonous  and  disagreeable 
like  chlorine.  The  osmium  will  be  converted  into  Os02  and  Os04,  which  are  very 
volatile.  The  residue  is  dissolved  in  aqua  regia  and  the  platinum  is  precipitated 
with  NH4C1. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 

OF   PLATINUM 

A.  Weighing  as  Metallic  Platinum 

1.  When  the  platinum  contains  only  a  small  amount  of  impurities  a  sample 
of  -fff  gram  or  more  is  taken  and  dissolved  in  aqua  regia.  The  solution  is  gently 
heated  until  all  is  dissolved,  adding  another  portion  of  aqua  regia  if  necessary. 
The  solution  is  evaporated,  adding  HC1  from  time  to  time  in  order  to  expel 
the  HN03.  Filter  and  evaporate  again  to  concentrate  the  solution.  Precipi- 
tate with  ammonium  chloride.  After  stirring,  let  stand  until  the  precipitate, 
(NH4)2PtCl«,  settles,  overnight  if  convenient.  Filter,  wash  with  alcohol  or 
ammonium  chloride  solution  and  alcohol,  and  ignite  to  metal,  which  will  be  in 
the  form  of  metallic  sponge.  Cool  in  a  desiccator  and  weigh  as  metallic  platinum. 

Wt.  of  Pt  found 

•X 100  =  per  cent  of  Pt  in  the  material. 


Wt.  of  sample  taken' 

2.  When  the  platinum  solution  contains  a  large  amount  of  impurities,  as 
iron,  nickel,  magnesia,  etc.,  it  is  advisable  to  reduce  the  platinum  to  black  metallic 
platinum  with  zinc,  iron  or  magnesium  as  follows:  The  solution  is  made  acid 
(2  to  5%  free  HC1)  by  adding  HC1.  The  Zn,  Fe  or  Mg  is  added  in  small  quanti- 
ties at  a  time  until  the  solution  becomes  colorless  or  until  the  platinum  is  com- 
pletely precipitated.1  After  action  has  ceased  the  platinum  black  metal  is 
filtered  onto  an  ashless  filter  paper  and  washed  with  warm  dilute  HC1  to  remove 
any  excess  Zn,  Fe,  or  Mg  that  might  be  present.  The  filter  and  its  contents  are 

1  FeCla  in  presence  of  HC1  has  a  solvent  action  on  platinum,  hence  the  iron  should 
be  completely  reduced. 


PLATINUM  329 

carefully  ignited  and  afterwards  dissolved  in  aqua  regia  and  treated  as  directed 
under  A,  I.1 

3.  If  none  of  the  other  Hydrogen  Sulphide  Group  metals  are  present  the 
platinum  can  be  precipitated  by  hydrogen  sulphide,  filtered,  washed  with  hot 
water  and  ignited  to  metal.  If  impurities  are  present  in  the  sulphide,  dissolve 
in  aqua  regia  and  proceed  as  under  A,  1. 

B.  Weighing  as  a  Salt 

1.  The  procedure  is  the  same  as  under  A.  The  (NH4)2PtCl«  precipitate 
is  washed  on  a  weighed  Gooch  crucible  with  alcohol.  The  crucible  and  con- 
tents are  dried  at  a  temperature  below  100°.  Cool  in  a  desiccator  and  weigh 
as  (XH4)2PtCl6. 


Wt.  of  (NH4)2PtCl.foundX 


Mol.  wt.  of  (NHOiPtCle    Wt.  of  sample 

=per  cent  of  Pt  in  material.2 


2.  After  proceeding  as  described  under  A,  the  platinum  is  precipitated  with 
potassium  chloride  as  K2PtCl6.  Transfer  to  a  weighed  Gooch  crucible  and  wash 
well  with  alcohol.  Dry  below  100°,  cool  in  a  desiccator  and  weigh  as  K2PtCl«. 

10°  %  of  Pt  in  material.' 


^^    ,          , 
Mol.  wt.  of  K2PtCU    Wt.  of  sample 

C.  Determination  of  Platinum  by  Electro-analysis 

When  platinum  solutions  are  acidulated  with  sulphuric  acid  and  acted  upon 
by  a  feeble  current  they  give  up  the  metal  as  a  bright  deposit  upon  the  elec- 
trode. If  platinum  is  used  as  the  electrode,  first  coat  it  with  a  layer  of  copper  and 
deposit  the  platinum  upon  the  copper.  Wash  with  water  and  alcohol  and  after 
drying  weigh. 

Wt.  of  electrode-j-Cu+Pt-Wt.  of  electrode  +Cu=Wt.  of  Pt. 

—  -  p  i'  °  ,  i   ,  —  X  100  =per  cent  of  Pt  in  material. 
Wt.  of  sample  taken 

Dr.  E.  F.  Smith,  in  his  work  on  "  Electro-Analysis  "  recommends  that  the 
K2PtCl«  be  dissolved  in  water  and  slightly  acidulated  with  H2S04  (2  or  3%  by 
vol.)  and  after  heating  to  about  60  to  65°  and  electrolyzing  with  N.D.ioo  =  .05 
ampere  and  1.2  volts,  the  platinum  will  be  completely  precipitated  in  from  four 
to  five  hours  in  a  perfectly  adherent  form.  A  rotating  anode  will  precipitate 
the  platinum  much  quicker. 

1  If  iron  and  lead  are  suspected,  the  platinum  residue  is  washed  with  10%  solution 
of  ammonium  chloride  and  then  with  10%  solution  of  ammonium  acetate  and  finally 
with  80%  alcohol. 

2  Factor  (XH4)2PtCl6  to  Pt  =  0.4393. 
•Factor  KaPtCl*  to  Pt  =  0.4013. 


RARER  ELEMENTS  OF  THE  ALLIED 
PLATINUM  METALS 

R.    E.    HlCKMAN.1 

IRIDIUM 

Element,   Iridium.     IT.  at.wt.  193.1;    sp.gr.  22.3;    m.p.  2350°  C.?   oxides 

IrO2,  Ir2O3. 

DETECTION 

Iridium  is  found  associated  with  platinum.  The  element  is  insoluble  in  all 
acids,  including  aqua  regia.  Chlorine  is  *he  best  reagent  which  forms  the  chlor- 
ides of  iridium  and  yields  compounds  with  other  chlorides  as  K3IrCl6,  which  is 
insoluble.  If  the  element  is  heated  in  a  stream  of  chlorine  in  the  presence  of 
potassium  chloride  there  forms  a  salt,  K2IrC]6,  which  is  sparingly  soluble  and  is 
used  in  the  separation  of  iridium. 

Caustic  Alkalies  produce  in  a  boiling  solution  a  dark-blue  precipitate  of 
Ir(OH)4  insoluble  in  all  acids  except  HC1. 

Potassium  chloride  forms  the  double  salt  of  K2IrCl6,  which  is  black  and  is 
difficultly  soluble  in  water. 

Ammonium  chloride  precipitates  black  (NH4)2IrCl6,  which  is  difficultly 
soluble  in  water. 

Hydrogen  sulphide  precipitates  black  Ir2S3,  soluble  in  (NH4)2S. 

Metallic  zinc  precipitates  from  an  acid  solution  black  metallic  iridium. 

Formic  acid  and  sulphurous  acid  precipitate  black  metallic  iridium  from 
hot  solutions. 

ESTIMATION 

Substances  in  which  iridium  is  determined  are  few,  namely:  platinum  scrap, 
jewelers'  sweeps,  contact  points,  ores,  etc. 

Preparation  and  Solution  of  the  Sample 

Platinum  scrap  and  contact  points,  etc.,  containing  iridium  dissolve  with 
difficulty  in  aqua  regia,  depending  on  the  amount  of  iridium  present.  The 
alloy  is  dissolved  quicker  if  it  is  rolled  or  hammered  to  a  very  thin  sheet  or 
ribbon.  The  alloy  of  platinum  and  iridium  with  an  iridium  content  up  to  10% 
dissolves  in  aqua  regia  slowly;  an  alloy  of  iridium  content  of  15%  dissolves  in 
aqua  regia  very  slowly  and  the  aqua  regia  will  likely  have  to  be  replenished  from 
time  to  time.  An  alloy  of  25%  iridium  is  practically  insoluble  in  aqua  regia. 
The  fillings  from  the  sweeps,  etc.,  can  be  dissolved  by  aqua  regia  the  same  as 
the  scrap.  After  expelling  the  HN03  the  platinum  and  the  iridium  are  precipi- 
1  Chemist,  J.  Bishop  &  Co.  Platinum  Works. 
330 


PLATINUM  GROUP  331 

tated  together  with  NH4C1  as  (NH4)2PtCl6  and  (NH4)2IrCl6.  When  the  pre- 
cipitate is  ignited  to  metal  it  forms  an  alloy  of  platinum  and  iridium.  The 
iridium  imparts  a  pinkish  to  a  scarlet  color  to  the  salt,  depending  on  the  amount 
of  indium" present. 

If  the  iridium  content  is  high  the  metal  can  be  mixed  with  Nad,  heated  to  a 
dull  red  heat  in  a  porcelain  or  silica  tube,  and  moist  chlorine  passed  over  the 
mixture.  The  iridium  will  be  in  the  form  of  a  chloride  which  dissolves  in 
water.  After  filtering  the  solution  and  evaporating  with  HC1,  the  iridium  as 
well  as  the  platinum  is  precipitated  with  NH4C1  or  H2S.  This  is  a  convenient 
way  on  a  larger  scale  to  dissolve  osmiridium  in  ores.  The  writer  has  had  good 
results  with  this  operation. 

When  the  iridium  is  contaminated  with  a  large  amount  of  impurities,  it  may 
be  reduced  from  the  solution  with  zinc,  and  the  impurities  dissolved  by  HN03 
and  dilute  aqua  regia;  the  residue  is  washed  and  dried  as  iridium. 

Clean  osmiridium  grains  are  also  brought  into  solution  by  a  fusion  of  KN03, 
NaN03  or  KC103  and  NaOH  or  KOH,  leaving  the  iridium  as  a  bluish  black 
oxide,  Ir203. 

Separations 

Separation  of  Iridium  from  Platinum.     See  Separation  of  Pt  from  Ir. 

If  the  platinum  and  iridium  are  alloyed  with  ten  times  their  weight  of  silver 
and  the  alloy  dissolved  in  HN03,  the  silver  and  the  platinum  dissolves,  leaving 
the  iridium  insoluble.  After  washing  the  residue,  treat  with  a  small  amount 
of  dilute  aqua  regia  to  dissolve  any  platinum  that  may  be  present. 

For  other  separations  see  Separations  under  Pt  and  the  other  metals. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 

OF    IRIDIUM 

Iridium  is  nearly  always  weighed  as  the  metal. 

1.  By  Reduction  with  Zinc 

The  solution  of  iridium  or  iridium  and  platinum  is  treated  with  C.P.  granulated 
zinc  and  5%  free  HC1.  The  iridium  and  the  platinum  are  precipitated  as  fine 
black  metal.  The  black  metal  is  washed  free  from  impurities  and  the  platinum 
is  dissolved  in  dilute  aqua  regia  as  described  under  the  Separations.  The 
insoluble  portion  is  dried  and  weighed  as  iridium. 

2.  By  Igniting  the  Salt  (NH4)2IrCl6 

When  the  iridium  content  is  low  and  the  platinum  and  the  iridium  are  pre- 
cipitated together  with  NH4C1,  the  iridium  imparts  a  pinkish  to  a  deep-red  color 
to  the  salt,  depending  on  the  amount  of  iridium  present.  The  percentage  of 
iridium  in  the  salt  can  be  judged  fairly  well  by  comparing  with  standard  iridio- 
platinum  salts.  The  salt  is  filtered,  washed  with  alcohol  and  carefully  ignited 
and  weighed  as  iridio-platinum  sponge  metal.  The  percentage  of  iridium  in 


332  PLATINUM  GROUP 

the  sample  can  be  obtained  from  the  weight  of  the  iridium  calculated  from  the 
percentage  of  iridium  in  the  salt. 

Per  cent  of  Ir  found  in  the  salt  XWt.  of  iridio-Pt  found  . 

i — —        .    ^  . X 100  =  %  of  Ir  in  material. 

Wt.  of  sample  taken 

When  the  iridium  is  in  solution  from  the  chlorine  method,  the  solution  is 
filtered  and  concentrated  with  HC1  and  the  iridium  precipitated  with  NH4C1. 
The  salt  (NH4)2IrCl6  is  filtered  and  washed  with  alcohol  and  carefully  ignited  to 
iridium  sponge.  Treat  with  a  few  drops  of  formic  acid  to  reduce  any  oxide  that 
may  form  or  reduce  with  hydrogen  and  weigh  as  metallic  iridium. 

Wt.  of  Ir  found  .  .  . 

- ; : — X  10(1= per  cent  of  Ir  in  material. 

Wt.  of  sample  taken 

3.  By  Obtaining  it  as  a  Residue 

The  iridium  and  the  platinum,  etc.,  are  alloyed  with  ten  times  its  weight  of 
silver  and  the  alloy  dissolved  in  HN03.  The  residue  will  be  a  small  amount  of 
platinum,  gold,  if  any  present,  and  iridium.  Add  a  small  amount  of  dilute  aqua 
regia,  which  will  dissolve  the  gold  and  the  rest  of  the  platinum,  leaving  the 
iridium  as  a  black  residue.  This  is  filtered,  washed  and  ignited  and  weighed  as 
metallic  iridium. 


PALLADIUM 

Element,  Palladium.    Pd.  at.wt.  106.7;   sp.gr.  11.9;   m.p.  1549°  C.;   oxides 

Pd20,  PdO,  Pd02. 

DETECTION 

This  metal  is  also  found  associated  with  platinum  and  iridium  as  well  as 
ruthenium,  rhodium,  and  osmium.  It  occurs  in  the  metallic  state  sometimes 
with  gold  and  silver.  It  resembles  platinum  as  to  luster  and  color.  Palladium 
sponge  when  heated  slightly  gives  a  rainbow  effect  due  to  the  formation  of 
oxides.  Hydrogen  passed  over  the  sponge  restores  it  to  the  original  color.  It 
dissolves  in  HN03  and  boiling  H2S04.  HC1  has  little  action  upon  it.  It  is 
readily  soluble  in  aqua  regia,  forming  PdCl2. 

Alkalies  precipitate  a  dark-brown  precipitate  soluble  in  an  excess  of  the 
reagent.  If  boiled  a  brown  palladous  hydroxide  is  precipitated.  The  anhydrous 
oxide  is  black. 

Ammonia  gives  a  flesh-red  precipitate,  PdCl2NH3,  soluble  in  excess  of 
ammonia.  If  HC1  is  added  to  this  solution  the  yellow  compound  of  pollad- 
ammonium  chloride,  Pd(NH3Cl)2,  is  deposited. 

Mercuric  cyanide  precipitates  a  yellowish-white  gelatinous  precipitate, 
Pd(CN)2,  insoluble  in  dilute  acids,  but  dissolving  in  ammonia  and  in  potassium 
cyanide  to  K2Pd(CN)4. 

Potassium  iodide  precipitates  black  palladous  iodide,  PdI2,  insoluble  in 
water,  alcohol,  and  ether,  but  soluble  in  an  excess  of  the  reagent. 


PLATINUM  GROUP  333 

Hydrogen  sulphide  precipitates  black  palladous  sulphide,  PdS,  soluble  in 
HC1  and  aqua  regia,  but  insoluble  in  (NH4)2S. 

Potassium  nitrite  precipitates  a  yellow  crystalline  powder,  K2Pd(N02)4. 

Ferrous  sulphate  slowly  produces  a  black  precipitate  of  metallic  palladium 
from  the  nitrate. 

Ammonium  chloride  precipitates  palladium  as  (NH4)2PdCl4  from  the 
nitrate. 

Formic  acid,  zinc  and  iron  reduce  to  metallic  palladium. 

ESTIMATION 

Palladium  is  determined  in  alloys,  ores,  jewelers'  sweeps,  etc. 

Preparation  and  Solution  of  the  Sample 

The  solubility  of  palladium  has  been  taken  up  under  Detection.  Palladium 
when  alloyed  with  platinum,  or  an  alloy  of  platinum,  iridium  and  palladium, 
dissolves  with  the  other  metals  in  aqua  regia  as  the  chloride.  When  palladium 
is  alloyed  with  silver  the  palladium  and  silver  are  dissolved  in  HN03,  from  which 
the  silver  can  be  separated. 

Separations 

Separation  of  Palladium  from  Platinum  and  Iridium.  The  chlorides  of 
palladium,  platinum  and  iridium  in  solution  must  be  free  from  HN03.  The 
platinum  and  the  iridium  are  precipitated  with  NH4C1,  leaving  the  palladium 
in  solution.  The  precipitate  is  put  on  a  filter  and  washed  free  from  Pd  with 
NH4C1  solution  and  alcohol. 

Separation  of  Palladium  from  Silver  and  Gold.  Three  times  the  weight  of 
the  gold  in  silver  should  be  present  in  the  alloy  in  order  to  separate  the  silver  and 
palladium  from  the  gold.  The  silver  and  the  palladium  will  dissolve  in  HN03, 
leaving  the  gold  as  the  residue.  This  is  filtered  off  and  the  silver  may  be  pre- 
cipitated with  HC1.  The  silver  chloride  is  filtered  off  and  washed  with  hot  water 
until  free  from  Pd. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 
OF   PALLADIUM 

1.  The  palladium  is  precipitated  from  the  solution  by  granulated  zinc,  the 
solution  having  a  small  amount  of  free  hydrochloric  acid.  The  residue,  after 
the  zinc  is  dissolved,  is  put  on  a  filter  and  washed  free  from  impurities.  Ignite 
the  filter  and  dissolve  in  a  small  amount  of  aqua  regia  and  evaporate  with  addi- 
tions of  HN03  to  get  rid  of  the  HC1.  Dilute  with  a  small  amount  of  water  and 
precipitate  the  palladium  with  NH4C1  crystals.  Heat  for  a  few  minutes  and  let 
cool.  Filter,  wash  with  alcohol,  and  ignite.  Moisten  with  formic  acid  to 
reduce  to  metal  any  oxide  that  may  have  formed.  Dry  and  weigh  as  metallic 
palladium. 

Wt.  of  Pd  found 

— — - — — : — X 100  =per  cent  of  Pd  in  material. 

Wt.  of  sampJe  taken 


334  PLATINUM  GROUP 

2.  With  the  solution  containing  about  one-fifth  the  volume  of  free  HC1,  the 
palladium  is  precipitated  with  10%  KI  solution.    Heat  to  nearly  boiling,  filter, 
wash  free  from  iron,  etc.,  with  1  :  4  HC1.    Ignite,  cool,  moisten  with  formic  acid, 
dry  and  weigh  as  metallic  Pd. 

3.  The  filtrate  from  the  platinum  precipitation  or  the  solution  containing  the 
Pd  is  made  to  about  150  cc.,  and  the  Pd  is  precipitated  by  adding  a  solution  of 
dimethylglyoxime  (1  gram  in  5  cc.  HC1).    Bring  to  boiling  and  let  stand  over- 
night if  convenient.    Filter  on  a  weighed  Gooch  crucible  and  wash  with  water 
acidified  with  HC1,  then  with  alcohol.    Dry  and  weigh  as  (CgHuN^OsPd,  which 
contains  31.68%  Pd. 

4.  The  nitric  acid  in  the  palladium  solution  is  expelled  by  evaporating  with 
HC1.    Neutralize  the  chloride  solution  almost  completely  with  sodium  carbonate 
and  mix  the  solution  with  a  solution  of  mercuric  cyanide,  Hg(CN)2,  and  heat  gently 
for  some  time.     Let  stand  until  cool,  overnight  if  convenient.    A  yellowish-white 
precipitate  of  Pd(CN)2  is  formed.    Filter,  wash  with  1%  Hg(CN)2  solution,  ignite 
and  reduce  in  hydrogen  to  metal,  or  reduce  with  formic  acid,  dry,  and  weigh 
as  metallic  Pd. 


RUTHENIUM 

Element,  Ruthenium.    Ru.  at.wt.  101.7;    sp.gr.  12;  .pm.  2450°  C.?  oxides 
RuO,  Ru2O3,  RuO3,  RuO4. 

DETECTION 

This  element  is  found  only  in  platinum  ores.  It  is  barely  soluble  in  aqua 
regia,  and  insoluble  in  acid  potassium  sulphate.  It  dissolves  when  fused  with  KOH 
and  KN03.  The  solution  of  the  fusion  when  dissolved  in  water  forms  potassium 
rutheniate,  K2Ru04,  from  which  HN03  precipitates  the  hydroxide,  which  is 
soluble  in  HC1.  The  treatment  with  chlorine  and  KC1  at  a  high  temperature 
yields  a  salt  of  K2RuCle.  The  salts  that  are  most  common  are  K2RuCl6  and 
K2RuCl6. 

Potassium  hydroxide  precipitates  a  black  hydroxide  easily  soluble  in  HC1. 

Hydrogen  sulphide  slowly  produces  black  Ru2S3. 

Ammonium  sulphide  precipitates  brownish  black  sulphide. 

Metallic  zinc  precipitates  metallic  ruthenium,  the  solution  first  turning 
blue. 

ESTIMATION 

Ruthenium  is  generally  estimated  in  alloys  and  ores  or  residues. 

Preparation  and  Solution  of  the  Sample 

When  ruthenium  is  alloyed  with  platinum  or  gold,  aqua  regia  dissolves  these 
metals,  forming  the  chlorides  of  platinum,  gold  and  ruthenium.  The  ruthenium 
in  ores  is  in  the  form  of  an  alloy  with  platinum  or  osmiridium.  This  is  fused  with 
KN03  and  KOH  in  a  silver  crucible,  the  osmium  and  the  ruthenium  forming  salts 
as  described  above,  while  the  iridium  remains  as  an  oxide. 


PLATINUM  GROUP  335 


Separations 

Separation  of  Ruthenium  from  Platinum.  The  two  metals  are  precipitated 
with  KCJ  and  the  potassium  rutheniochloride  is  dissolved  out  with  cold  water 
containing  a  very  small  amount  of  KC1  and  alcohol.  The  ruthenium  is  then 
precipitated  from  an  acid  solution  by  additions  of  granulated  zinc. 

A  separation  may  be  made  by  alloying  with  silver  and  dissolving  the  platinum 
and  silver  by  HN03,  the  ruthenium  remaining  as  the  residue. 

Separation  of  Ruthenium  from  Iridium.  The  two  metals  are  fused  with 
KOH  and  KN03  as  described  above,  the  ruthenium  forming  a  salt  soluble  in  water 
and  the  iridium  remaining  as  an  oxide. 

To  the  solution  of  the  two  metals,  sodium  nitrite  is  added  in  excess,  with 
sufficient  sodium  carbonate  to  keep  the  liquid  neutral  or  alkaline.  The  whole 
is  boiled  until  an  orange  color  appears.  The  ruthenium  and  the  iridium  are 
converted  into  soluble  double  nitrites.  Sodium  sulphide  is  then  added,  small 
quantities  at  a  time  until  the  precipitated  ruthenium  sulphide  is  dissolved  in  the 
excess  of  alkaline  sulphide.  At  first  the  addition  of  the  sulphide  gives  the  char- 
acteristic crimson  tint  due  to  ruthenium,  but  this  quickly  disappears  and  gives 
a  bright  chocolate-colored  precipitate.  The  solution  is  boiled  for  a  few  minutes, 
and  allowed  to  become  perfectly  cold  and  then  dilute  HC1  cautiously  added 
until  the  dissolved  ruthenium  sulphide  is  precipitated  and  the  solution  is  faintly 
acid.  The  solution  is  filtered  and  the  precipitate  washed  with  hot  water.  The 
filtrate  will  be  free  from  ruthenium.1 

Separation  of  Ruthenium  from  Rhodium.  The  mixed  solution  of  the  two 
metals  is  treated  with  potassium  nitrite  as  described  above.  The  orange-yellow 
solution  is  evaporated  to  dryness  upon  the  water  bath  and  treated  with  absolute 
alcohol.  The  rhodium  remains  undissolved  and  can  be  filtered  off  and  washed 
with  alcohol.  The  rhodium  salt  can  be  ignited  with  NH4C1  and  after  washing 
yields  metallic  rhodium. 


GRAVIMETRIC    METHODS    FOR    THE    DETERMINATION 
OF    RUTHENIUM 

Ruthenium  is  best  weighed  as  the  residue  after  the  other  metals  are  elimi- 
nated. It  may  be  precipitated  from  the  solution  with  zinc  and  after  filtering, 
washing  and  igniting  the  filter  the  impurities  are  dissolved  in  aqua  regia.  The 
residue  is  ruthenium.  The  metals  may  be  alloyed  with  silver  and  after  dis- 
solving out  the  silver,  platinum  and  palladium  with  HN03,  the  residue  is  treated 
with  aqua  regia,  leaving  the  residue  as  ruthenium.  If  iridium  is  present  in  the 
residue,  weigh  as  iridium  and  ruthenium.  Make  a  fusion  with  KOH  and 
KN03  as  described  under  iridium  and  filter  off  the  Ir203.  Calculate  the  weight 
of  Ir  which  is  to  be  subtracted  from  the  weight  of  the  ruthenium  and  iridium. 
The  difference  is  ruthenium. 

The  solution  of  Ru2Cl6  is  evaporated  to  drive  off  the  excess  acid  and  then 
taken  up  with  50  to  60  cc.  of  water  and  a  few  pieces  of  magnesium  added  gradually. 
The  solution  is  filtered  and  the  residue  washed  with  a  5%  H2S04  solution  to  get 
rid  of  any  magnesium  that  may  be  present.  Ignite  at  the  lowest  possible  tem- 
perature, and  heat  in  hydrogen  to  red  heat,  cool  and  weigh  as  metallic  ruthenium. 

1  "Select  Methods  in  Chemical  Analysis,"  Sir.  Wm.  Crookes. 


336  PLATINUM  GROUP 


RHODIUM 

Element,  Rhodium.    Rh,  at.wt.  102.9;  sp.gr.  12.1;  m.p.  1950°  C.;  oxides 

RhO,  Rh2O3,  RhO2. 

DETECTION 

Rhodium  is  found  only  in  platinum  ores.  It  is  a  white  metal,  difficultly  fusible, 
and  insoluble  in  acids.  Rhodium,  however,  dissolves  in  aqua  regia  when  alloyed 
with  platinum,  to  a  cherry  red  solution.  It  is  also  soluble  in  molten  phosphoric 
acid  and  dissolves  when  fused  with  acid  potassium  sulphate  with  the  formation 
of  K3Rh(S04)3.  If  the  metal  is  treated  with  chlorine  in  the  presence  of  sodium 
chloride  there  forms  a  soluble  salt,  Na3RhCl6. 

Hydrogen  sulphide  precipitates  from  a  hot  solution  and  incompletely  a 
brown  rhodium  sulphide,  Rh2S3. 

Potassium  hydroxide  precipitates  at  first  a  yellow  hydroxide,  Rh  (OH)  3+H20 
soluble  in  an  excess  of  the  reagent.  If  boiled,  a  gelatinous,  dark-brown  hydroxide, 
Rh(OH)3,  separates.  A  solution  of  Na3RhCl6  does  not  show  this  reaction  imme- 
diately, but  the  precipitate  appears  in  the  course  of  time.  An  addition  of  alcohol 
causes  a  black  hydroxide  to  be  precipitated  at  once. 

Ammonium  hydroxide  produces  a  yellow  precipitate  of  Rh(NH3)5Cl3  which 
is  insoluble  in  HC1. 

Potassium  nitrite  precipitates  from  hot  solutions  a  bright  yellow  precipi- 
tate of  double  nitrite  of  potassium  and  rhodium. 

Zinc,  iron  and  formic  acid  precipitate  rhodium  as  a  black  metal. 

Hydrogen  reduces  rhodium  salts. 

ESTIMATION 

Rhodium  is  estimated  mainly  in  ores,  thermo  couples  and  salts. 

Preparation  and  Solution  of  the  Sample 

When  rhodium  is  estimated  in  thermo  couples  or  other  alloys  of  platinum 
and  rhodium  the  wire  or  sample  is  rolled  to  a  thin  ribbon  and  dissolved  in  aqua 
regia.  Both  metals  will  go  into  solution,  forming  the  chlorides  of  rhodium  and 
platinum.  The  aqua  regia  will  have  to  be  replaced  from  time  to  time,  as  the 
alloy  dissolves  slowly. 

The  rhodium  from  salts  is  precipitated  with  zinc  and  the  black  metallic 
rhodium  cleaned  with  dilute  aqua  regia,  filtered,  washed,  ignited  and  reduced 
with  hydrogen. 

Some  alloys  and  ores  are  alloyed  with  silver  and  the  silver  and  platinum  are 
dissolved  in  HN03.  The  residue  is  cleaned  with  aqua  regia,  dried,  and  weighed 
as  metallic  rhodium.  If  the  residue  is  ignited  reduce  with  hydrogen. 

Separations 

Separation  of  Rhodium  from  Platinum.  The  alloys  of  platinum  and 
rhodium  (10%)  dissolve  slowly  in  aqua  regia  as  stated  above.  After  expelling 
the  HNOi  the  metals  are  precipitated  with  NH<C1.  The  precipitate  is  filtered 


PLATINUM  GROUP  337 

and  washed  with  dilute  ammonium  chloride  solution,  which  dissolves  the  rhodium 
salt.  A  very  small  amount  of  rhodium  will  color  the  filtrate  pink  to  a  rose-red 
color,  depending  on  the  amount  of  rhodium  present. 

Separation  of  Rhodium  from  Iridium.    See  Separation  of  Rh  from  Pt. 

A  separation  can  be  made  by  adding  sodium  nitrite  in  excess  to  the  solu- 
tion of  the  two  metals,  with  a  sufficient  quantity  of  sodium  carbonate  to  make 
the  solution  neutral  or  alkaline;  this  is  boiled  until  the  solution  assumes  a  clear 
orange  color.  The  rhodium  and  iridium  are  converted  into  soluble  double  nitrites. 
A  solution  of  sodium  sulphide  is  added  in  slight  excess  and  the  liquid  made  slightly 
acid.  The  rhodium  is  precipitated  as  dark-brown  rhodium  sulphide. 

Separation  of  Rhodium  from  Ruthenium.  The  solution  containing  the  two 
metals  is  treated  with  sodium  nitrite  as  above  and  evaporated  to  dryness.  The 
residue  is  powdered  and  treated  in  a  flask  with  absolute  alcohol.  After  filter- 
ing and  washing  with  alcohol  the  rhodium  remains  undissolved. 


GRAVIMETRIC   METHODS    FOR   THE    DETERMINATION 

OF  RHODIUM 

From  the  solution  of  platinum  and  rhodium,  the  platinum  is  precipitated 
with  NH4C1  and  the  precipitate  filtered  off  and  washed  free  from  rhodium  with 
dilute  ammonium  chloride  solution.  The  rhodium  is  precipitated  with  zinc 
and  the  residue  is  washed  well  with  hot  water  acidulated  with  HC1.  The  residue 
is  then  cleaned  with  dilute  aqua  regia  and  the  black  metallic  rhodium  is  filtered 
off,  dried,  and  weighed  as  metallic  rhodium.  If  the  filter  is  ignited  reduce  in 
hydrogen  before  weighing. 

The  alloy  may  be  melted  with  lead  or  silver  and  the  buttons  dissolved  in 
HN03,  leaving  a  residue  which  is  treated  with  aqua  regia  to  dissolve  any  platinum 
that  might  remain.  Wash  and  weigh  as  metallic  rhodium.  If  iridium  is  with 
the  rhodium  the  residue  is  treated  with  salt  and  chlorine  and  the  melt  dissolved 
in  water  as  described  under  Iridium.  The  iridium  is  precipitated  with  NH4C1 
and  the  rhodium  with  zinc.  The  rhodium  black  is  cleaned  with  dilute  aqua 
regia,  filtered,  washed  and  ignited.  Reduce  in  hydrogen  and  weigh  as  metallic 
rhodium. 


OSMIUM 

Element,  Osmium.    Os,  at .  wt .  190.9 ;  sp.gr.  22  A ;  m.p.  3700°  C.?  oxides  OsO, 

Os2O3,  OsO2,  OsO4. 

DETECTION 

Osmium  occurs  with  platinum  ores  and  alloyed  with  iridium.  The  chlorides, 
OsCli  and  OsCl4,  combine  with  the  alkali  chlorides.  Osmium  oxidizes  easily  and 
burns  in  the  flame.  Through  the  action  of  HN03,  aqua  regia  or  heating  in  a 
stream  of  moist  chlorine,  osmic  tetroxide  is  formed.  Osmium  is  very  volatile 
and  the  fumes  are  poisonous.  It  is  detected  readily  by  the  odor  when  heated, 
as  the  fumes  are  highly  corrosive  and  disagreeable  like  chlorine.  Chlorine  passed 
over  hot  osmium  mixed  with  KC1  gives  K2OsCl6,  which  dissolves  in  cold  water. 


338  PLATINUM  GROUP 

Hydrogen  sulphide  precipitates  brownish  black  osmium  sulphide,  OsS4, 
but  only  in  the  presence  of  some  strong  mineral  acid.  It  is  insoluble  in  ammonium 
sulphide. 

Potassium  hydroxide  precipitates  reddish-brown  osmium  hydroxide. 

Ammonium  hydroxide  precipitates  the  osmium  hydroxide. 

Zinc  and  formic  acid  precipitate  black  metallic  osmium. 

Hydrogen  reduces  osmium  compounds  to  the  metal. 


ESTIMATION 

Osmium  is  estimated  mainly  in  osmiridium  and  platinum  residues. 

Preparation  and  Solution  of  the  Sample 

After  the  platinum  is  extracted  the  residue  or  osmiridium  is  mixed  with  two 
or  three  times  its  weight  of  common  table  salt.  The  mixture  is  put  in  a  porce- 
lain or  silica  tube  and  heated  to  a  dull  red  heat;  moist  chlorine  is  then  passed 
through  the  tube  for  a  short  time.  The  mass  is  cooled  and  dissolved  with  water. 
After  several  treatments  the  entire  group  of  platinum  metals  will  be  in  solution. 

The  osmium  material  may  also  be  fused  with  KOH  and  KN03  and  the  melt 
dissolved  in  water.  The  osmium  will  be  in  solution  as  potassium  osmate,  K20s04, 
while  the  iridium  remains  as  residue. 

For  Separations  see  below. 


GRAVIMETRIC    METHODS    FOR   THE    DETERMINATION 

OF  OSMIUM 

The  osmium  is  very  difficult  to  ascertain  on  account  of  the  element  being 
very  volatile. 

The  potassium  osmate,  K20s04,  solution  is  put  in  a  small  retort,  and  boiled 
with  HNO3,  the  vapor  is  conducted  into  NaOH  solution  and  after  acidifying  with 
a  little  HC1  the  osmium  can  be  precipitated  with  Na2S203  as  a  brown  precipitate 
of  Os04  which  is  filtered,  washed,  dried  and  weighed  as  the  oxide. 

When  osmuim  is  in  the  form  of  osmate  of  sodium,  the  solution  is  heated  gently 
and  strips  of  aluminum  are  plunged  in  and  the  osmium  will  be  deposited  in 
metallic  form,  while  the  aluminum  dissolves  in  the  soda.  Care  must  be  taken 
n  jt  to  add  too  much  aluminum,  as  an  aluminate  might  be  precipitated  which  is 
troublesome.  When  the  solution  is  discolored  the  dense  precipitated  osmium 
is  washed  by  decantation  with  water  to  remove  the  sodium  aluminate,  and  then 
with  5%  H2S04  solution  to  remove  the  excess  aluminum.  The  osmium  is  dried 
in  a  bell-jar  filled  with  hydrogen,  then  heated  to  a  dull  redness  and  cooled  in  a 
current  of  hydrogen.  The  osmium  is  weighed  as  the  metal.  As  a  check  the 
osmium  may  be  driven  off  in  the  form  of  Os04  by  heating  to  redness  with  plenty 
of  air,  or  better,  in  a  current  of  oxygen  and  weighing  again.1 

1  "Select  Methods  in  Chemical  Analysis,"  Sir  Wm.  Crookes. 


PLATINUM  GROUP  339 


ANALYSIS  OF  PLATINUM  ORES 

Take  3  to  5  grams  of  the  ore  and  treat  with  aqua  regia.  After  diluting, 
the  osnliridium  and  gangue  are  filtered  out,  ignited  and  weighed.  The  insoluble 
portion  is  then  fused  in  an  assay  crucible  with  at  least  twice  the  weight  of 
granulated  silver  and  borax  glass.  Clean  the  button  and  treat  with  dilute  HN03, 
filter,  wash  free  from  silver,  ignite  and  weigh  as  osmiridium. 

The  aqua  regia  solution  is  evaporated  several  times  with  HC1  nearl/  to 
dryness.  Then  pass  in  a  current  of  chlorine  for  thirty  minutes,  cool  in  chlorine 
and  evaporate  at  40°  to  a  thick  paste.  Dilute  with  water,  getting  a  clear  solution 
of  PtCl4,  IrCl4,  RhCls,  AuCl3,  PdCl4,  CuCl2  and  FeCl3.  Saturate  the  solution 
with  NH4C1  and  after  forty-eight  hours  filter  off  the  (NH4)2PtCl6  and  (NH4)  JrCl6; 
ignite  in  a  porcelain  crucible,  adding  crystals  of  ash-free  oxalic  acid  toward  the 
end.  Digest  the  platinum  and  indium  sponge  with  10%  HC1,  filter,  ignite,  reduce 
in  hydrogen,  cool  in  C02  and  weigh  as  platinum  and  iridium  (Ru).  In  the 
filtrate  from  the  platinum  and  iridium,  separate  the  palladium  with  dimethyl- 
glyoxime.  Evaporate  the  filtrate  to  dryness  and  destroy  the  NH4C1  by  adding 
concentrated  HN03  followed  by  concentrated  HC1.  Dissolve  the  residue  in  water 
and  add  (NH4)2C?04  and  heat  from  four  to  six  hours  till  the  gold  is  reduced; 
add  dilute  H2S04,  filter  and  wash  with  dilute  H2S04,  then  with  dilute  HC1,  ignite 
and  weigh  as  gold.  Neutralize  the  excess  acid  with  NH4OH  and  precipitate  any 
palladium  in  a  boiling  acid  solution  with  dimethylglyoxime. 

Treat  the  filtrate  from  the  gold  and  palladium  with  50  grams  of  pure  zinc  and 
50  cc.  of  concentrated  HC1;  after  five  or  six  hours  the  solution  should  be  color- 
less, otherwise  add  more  HC1.  Filter  by  suction  and  wash  with  dilute  HC1, 
then  with  water  till  free  from  acid,  dry  the  filter  and  ignite  two  or  three  hours; 
grind  this  in  a  glass  mortar  and  digest  two  hours  with  HN03  (1  :  1),  filter  and 
wash  with  water;  the  residue  is  rhodium  with  traces  of  platinum  and  iridium. 
Evaporate  the  filtrate  to  dryness  repeatedly  with  HC1  and  determine  the  copper. 

Evaporate  the  filtrate  from  the  copper  to  dryness,  treating  with  HN03,  then 
HC1;  add  water,  HC1  and  zinc  as  above;  add  the  ash  to  the  main  rhodium  portion 
and  grind  in  a  glass  mortar  with  acid  potassium  sulphate,  KHS04,  and  fuse  in  a 
crucible;  the  rhodium  is  converted  into  a  soluble  sulphate,  the  iridium  is  oxi- 
dized and  the  platinum  remains  unaltered.  Digest  the  melt  with  water  and 
dilute  HC1 ;  a  metallic  residue  is  platinum  or  iridium.  Filter  and  wash  with  very 
dilute  HC1;  to  the  filtrate  add  zinc  to  precipitate  the  rhodium,  filter  and  wash 
with  5%  H2S04  solution,  ignite  and  let  cool.  Finally  ignite  in  hydrogen,  cool 
in  C02  and  weigh.  The  insoluble  residue  from  the  KHS04  fusion  is  ignited, 
reduced  and  weighed.  The  platinum  and  iridium  may  be  separated  as  described 
before. 

Make  up  the  filtrate  from  the  first  zinc  reduction  to  1  liter  and  treat  500  cc. 
with  HN03  or  H2O2;  make  two  basic  acetate  precipitations  and  finally  precipi- 
tate at  70°  with  NH4OH,  ignite  and  weigh  as  Fe203. 

Calculation. 

100  —per  cent  sand  =  A. 

100 

— p  =  factor  by  which  per  cent  found  is  to  be  multiplied. 
A. 

1 A  modification  of  the  Deville-Debray  Procedure,  by  Wiinder  and  Thuringer. 


340  PLATINUM  GROUP 


ASSAY  METHODS  OF  PLATINUM  ORES,  ETC. 

Take  from  10  to  30  grams  of  the  material  and  place  in  a  2|-  or  3-in.  scorifiei 
with  about  20  to  30  grams  of  test  lead  and  cover  with  litharge.  Fuse  in  a  muffle 
for  a  half  hour.  When  cool  clean  the  lead  button  thoroughly  and  dissolve  the 
lead  with  dilute  nitric  acid  (1  :  3).  When  the  lead  is  dissolved,  filter,  and  wash 
the  residue  with  hot  water  till  free  from  lead.  Dry  the  filter  and  remove  the 
residue  to  a  small  glass  beaker  and  burn  the  filter,  after  which  the  ash  is  added 
to  the  residue  in  the  small  glass  beaker.  This  is  treated  with  dilute  aqua 
regia  to  remove  any  gold,  platinum,  etc.,  that  may  be  present.  Filter  and  wash 
thoroughly  with  hot  water  and  ignite  at  a  low  temperature  for  a  short  time 
only,  as  osmium  will  volatilize.  Weigh  as  osmiridium. 

Take  another  portion  of  10  to  30  grams  of  the  material  and  treat  with  aqua 
regia  two  or  three  times.  This  will  bring  the  platinum  and  the  alloys  (except 
osmiridium)  into  solution.  After  filtering  make  up  the  volume  to  500  to  1000  cc., 
depending  on  the  amount  of  platinum  present.  Take  two  or  three  portions  of 
25  to  50  cc.  of  the  solution  and  evaporate  to  nearly  dryness  with  additions  of 
HC1  to  get  rid  of  the  HN03.  Take  up  with  a  small  amount  of  water  and  add 
ammonium  chloride.  Digest  on  the  water  bath  and  let  cool  overnight  if  con- 
venient. Filter  onto  an  ashless  filter  and  wash  with  dilute  ammonium  chloride 
solution  and  alcohol.  Ignite  cautiously  and  weigh  as  platinum.  The  iridium 
will  be  precipitated  with  the  platinum  and  weighed  with  the  platinum;  the 
color  of  the  pure  platinum  precipitate  is  yellow,  but  the  iridium  precipitate  will 
impart  a  pink  to  a  deep  red  color  to  the  platinum  precipitate,  and  the  per  cent 
of  iridium  present  can  easily  be  judged  by  comparing  with  standard  iridio-plati- 
num  salts. 

The  filtrate  from  the  platinum  precipitation  is  treated  with  ferrous  sulphate 
to  precipitate  the  gold.  Digest  and  filter  out  the  gold.  Ignite  and  alloy  with 
silver  and  part  for  gold. 

To  the  filtrate  from  the  gold  add  an  excess  of  HC1  and  precipitate  the  pal- 
ladium with  10%  solution  of  potassium  iodide  as  described  under  palladium. 
The  palladium  can  be  taken  out  before  the  gold  by  evaporating  the  filtrate  from 
the  platinum  precipitation  and  precipitating  the  palladium  with  nitric  acid  and 
ammonium  chloride  as  described  under  palladium. 

In  the  filtrate  from  the  palladium  precipitation  the  rhodium  is  precipitated 
with  zinc  until  the  solution  is  colorless.  Wash  well  with  hot  water  and  clean 
with  dilute  aqua  regia.  If  this  is  done  carefully  the  residue  will  be  clean  rhodium 
with  probably  a  trace  of  iridium.  Ignite  the  residue  and  reduce  in  hydrogen 
and  weigh  as  rhodium. 

If  ruthenium  and  the  total  iridium  content  are  to  be  estimated  the  separations 
are  the  same  as  described  under  these  elements. 


POTASSIUM,  SODIUM  AND  OTHER  ALKALIES 

W.  B.  HrcKS.1 

Sodium,  Na,  at.wt.  23.00;   sp.gr.  0.9735;  m.p.  97.6°;    b.p.  877.5°  C.;  oxides 

Na2O, 


Potassium,  K,  at.wt.  39.10;    sp.gr.  0.875;    m.p.  63.5°;  b.p.  757.5°  C.;    oxides 

K20,  K204. 

Lithium,  IA9at.wt.  6.94;  sp.gr.  0.534;  m.p.  186°;  b.p.  >1400°C.;  oxide  Li2O. 

Rubidium,  Rb,  at.wt.  85.45;  sp.flrr.  1.532;  m.p.  38.5°;    b.p.  696°  C.;    oxides 
Rb2O,  Rb2O2,  Rb2O3,  Rb2O4. 

Caesium,  Cs9  at.wt.  133.81;    sp.flrr.  1.87;    m.p.  26.37°;    b.p.  670°  C.;    oxides 
Cs2O,  Cs2O2,  Cs2O3,  Cs2O4. 

DETECTION 
Detection  of  Sodium 

Sodium  is  usually  identified  by  the  color  which  it  imparts  to  the  flame  or  by 
means  of  the  spectroscope.  The  solution  is  prepared  as  directed  under  Prepara- 
tion and  Solution  of  Sample,  and  is  freed  from  all  constituents  other  than  the 
chlorides  of  magnesium  and  the  alkalies  according  to  the  methods  given  under 
Separations.  With  exceedingly  small  amounts  of  sodium,  it  may  be  necessary 
to  remove  the  magnesium  also.  After  acidifying  with  hydrochloric  acid,  a  drop 
of  the  solution  is  brought  into  the  flame  by  means  of  a  loop  of  platinum  wire. 
In  the  presence  of  sodium,  the  flame  assumes  an  intense  yellow  color,  which  is 
usually  sufficient  to  identify  the  element.  The  results  may  be  confirmed  by 
examining  the  flame  in  the  spectroscope,  when  the  characteristic  yellow  sodium 
line  will  be  prominent  even  in  the  presence  of  traces  of  sodium.  As  a  matter  of 
fact,  the  ever-presence  of  the  sodium  line  is  a  hindrance  to  the  success  of  the 
method,  but  by  observing  the  sudden  change  in  the  intensity  of  the  line,  little 
trouble  will  be  experienced  in  detecting  exceedingly  small  amounts  of  the  metal. 

Sodium  may  also  be  detected  by  precipitation  as  sodium  pyroantimonate, 
H2Na2Sb207  •  H20,  from  a  sufficiently  concentrated  neutral  or  weakly  alkaline 
solution  by  means  of  a  solution  of  acid  potassium  pyroantimonate.  The  pre- 
cipitate comes  down  in  granular  or  crystalline  form,  and  its  formation  is  hastened 
by  rubbing  the  sides  of  the  vessel  with  a  glass  rod.  In  making  this  test,  mag- 
nesium must  also  be  previously  removed  from  the  solution. 

In  waters  and  soluble  salts,  it  is  usually  sufficient  to  test  directly  the  con- 
centrated solution  in  the  flame  or  spectroscope. 

Detection  of  Potassium 

For  the  detection  of  potassium  in  insoluble  compounds,  bring  the  sample 
into  solution  by  one  of  the  methods  given  under  Preparation  and  Solution  of 

1  Assistant  Chemist,  U.  S.  Geological  Survey,  Washington,  D.  C. 
341 


342     POTASSIUM,  SODIUM  AND   OTHER  ALKALIES 

Sample.  In  other  cases,  prepare  a  strong  solution  of  the  material  to  be  tested. 
Where  only  very  small  amounts  of  potassium  are  present,  remove  all  the  con- 
stituents from  the  solution  except  the  chlorides  of  magnesium  and  the  alkalies 
as  directed  under  Separations.  In  the  presence  of  considerable  amounts  of 
potassium,  small  quantities  of  other  constituents  will  not  materially  interfere 
with  the  flame  and  spectroscopic  tests.  After  acidifying  with  hydrochloric 
acid,  bring  a  drop  of  the  solution  to  be  tested  into  the  non-luminous  flame  and 
observe  the  color  produced  through  a  Merwin  color  screen.1  In  the  presence  of 
potassium,  a  distinct  reddish- violet  coloration  will  be  apparent.  This  must  not 
be  confused  with  the  color  caused  by  large  amounts  of  sodium,  which  appears 
bluish-violet  through  the  screen.  Comparison  with  the  coloration  produced  by 
pure  salts  is  advisable.  If  necessary,  confirm  the  results  by  examining  the  flame 
in  the  spectroscope.  In  the  presence  of  a  moderate  amount  of  a  volatile 
potassium  compound,  a  bright  red  line  will  be  readily  seen  in  the  red  portion  of 
the  spectrum,  and  a  less  distinct  violet  line  will  be  visible  far  out  in  the  violet 
rays. 

Potassium  may  also  be  identified  by  various  reactions,  such  as  precipitation 
from  a  strong  solution,  as  potassium  chloroplatinate,  perchlorate,  acid  tartrate, 
picrate,  cobaltic  nitrite,  silico-fluoride,  phosphotungstate,  etc.  These  compounds 
of  potassium  are  all  sparingly  soluble  in  water  while  the  corresponding  sodium 
salts  are  readily  soluble. 

Detection  of  Lithium 

Bring  the  sample  into  solution  as  directed  under  Preparation  and  Solution  of 
Sample,  and  separate  the  alkali  chlorides  from  other  constituents  according  to 
the  methods  under  Separations.  Digest  the  dry  chlorides  with  amyl  alcohol 
or  with  a  mixture  of  absolute  alcohol  and  ether,  filter,  and  evaporate  the  filtrate 
to  dryness.  Moisten  the  residue  with  dilute  hydrochloric  acid  and  examine 
it  in  the  spectroscope.  A  bright  red  band  and  a  faint  orange  line  make  up  the 
flame  spectrum  of  lithium.  These  lie  between  the  sodium  line  and  the  red  potas- 
sium line  and  are  easily  recognized. 

Lithium  salts  impart  a  carmine-red  color  to  the  flame,  which  is  obscured  by 
sodium,  and  by  large  amounts  of  potassium.  But  by  the  proper  use  of  a  color 
screen,  the  lithium  flame  may  be  recognized  in  the  presence  of  large  amounts 
of  sodium. 

Confirmation  of  the  presence  of  lithium  may  be  had  by  the  formation  of  the 
sparingly  soluble  lithium  phosphate  or  lithium  fluoride. 

Detection  of  Rubidium  and  Caesium 

In  the  usual  course  of  analysis,  these  rare  elements  are  separated  along  with 
sodium,  potassium,  and  lithium  from  all  other  bases.  In  order  to  detect  rubidium 
and  caesium,  extract  the  dry  chlorides  of  the  alkali  metals  with  a  few  drops  of 
hydrochloric  acid  and  90%  alcohol.  This  will  dissolve  most  of  the  rare  alkalies 
along  with  some  sodium  and  potassium.  Evaporate  the  solution  to  dryness, 
dissolve  in  a  very  small  amount  of  water,  and  add  chloroplatinic  acid  solution. 
Rubidium,  caesium,  and  potassium  chloroplatinates  will  be  precipitated.  Filter 

1  The  Merwin  color  screens  are  manufactured  and  sold  by  G.  M.  Flint,  84  Wendell 
Street,  Cambridge,  Mass.,  at  25  cents  apiece,  and  are  far  superior  to  the  ordinary 
cobalt  glass. 


POTASSIUM,   SODIUM   AND  OTHER  ALKALIES      343 

and  wash  the  residue  repeatedly  with  hot  water  to  remove  the  potassium  salt, 
which  is  much  more  soluble  than  rubidium  and  caesium  chloroplatinates.  During 
this  treatment,  examine  the  residue  from  time  to  time  in  the  spectroscope.  As  the 
rubidium  and  caesium  salts  are  concentrated  through  washing,  their  spectra 
will  gradually  become  visible. 

ESTIMATION 

The  estimation  of  sodium  and  potassium  is  required  in  the  analysis  of  rocks, 
clays,  soils,  ashes  of  plants,  waters,  brines,  saline  deposits,  salts  of  the  alkalies, 
many  technical  products,  and  in  other  cases.  The  determination  of  potassium 
is  of  special  importance  in  the  analysis  of  fertilizers.  The  estimation  of  lithium 
is  desired  in  the  analysis  of  lithium  minerals,  frequently  in  mineral  waters, 
occasionally  in  rocks,  and  in  certain  other  special  cases.  The  estimation  of 
rubidium  and  caesium  is  seldom  required. 

Preparation  and  Solution  of  Sample 

Procedure  for  Rocks  and  Other  Insoluble  Mineral  Products.  For  silicate 
rocks  and  other  silicious  material,  bring  the  alkalies  into  solution,  according  to 
the  J.  Lawrence  Smith  or  the  hydrofluoric  acid  method,  as  directed  on  pages  355 
and  356.  In  the  case  of  alunite  prepare  the  solution  as  directed  on  page  356. 
For  products  which  are  dissolved  by  hydrochloric  acid,  effect  the  solution  by  acid 
digestion,  expel  the  excess  of  acid  by  evaporation,  and  remove  other  constituents 
as  directed  under  Separations. 

Procedure  for  Soils.1  Digest  10  grams  of  moisture-free  soil  with  100  cc.  of 
hydrochloric  acid  of  a  constant  boiling-point  (sp.gr.  1.115)  in  a  300-cc.  Erlen- 
meyer  flask  fitted  with  a  ground-glass  or  rubber  stopper  and  a  reflux  condenser. 
Digest  continuously  for  ten  hours  on  the  steam  bath,  shaking  the  flask  every 
hour.  After  settling,  decant  the  solution  into  a  porcelain  dish.  Wash  the 
insoluble  residue  onto  a  filter  with  hot  water,  and  continue  the  washing  until 
free  from  chlorides,  adding  the  washings  to  the  original  solution  for  evaporation. 
Oxidize  the  organic  matter  present  in  the  solution  with  a  few  drops  of  nitric  acid 
and  evaporate  to  dryness  on  a  water  bath.  Moisten  with  hydrochloric  acid  and 
dissolve  in  hot  water  and  evaporate  a  second  time  to  complete  dryness  and 
until  the  excess  of  hydrochloric  acid  is  completely  removed.  Moisten  the  cooled 
residue  with  strong  hydrochloric  acid  and  dissolve  in  hot  water.  Filter  into  a 
250-cc.  graduated  flask,  wash  free  from  chlorides,  and  dilute  to  the  mark.  Use  an 
aliquot  of  100  cc.  for  the  determination  of  the  alkalies. 

Procedure  for  Fertilizers.2  Potash  salts.  Boil  10  grams  of  the  sample 
with  300  cc.  of  water  for  thirty  minutes,  wash  into  a  500-cc.  graduated  flask, 
cool,  dilute  to  the  mark,  mix  and  pass  through  a  dry  filter.  Determine  the 
potassium  in  a  25-cc.  aliquot  representing  0.5  gram  of  the  original  substance, 
according  to  either  the  modified  chloroplatinate  or  the  Lindo-Gl adding  method. 

Mixed  fertilizers.  Boil  10  grams  of  the  sample  with  300  cc.  of  water  for  thirty 
minutes,  and  wash  into  a  500-cc.  graduated  flask.  Add  to  the  hot  solution  a 
slight  excess  of  ammonia  and  sufficient  ammonium  oxalate  to  precipitate  all  the 
lime,  cool,  dilute  to  the  mark,  mix,  and  pass  through  a  dry  filter.  Evaporate 

1  U.  S.  Dept.  Agr.,  Bu.  of  Chem.,  Bull.  107  (revised),  14,  1907. 

2  U.  S.  Dept.  AgrL,  Bu.  Chem.  Bull.  107  (revised),  11,  1907. 


344     POTASSIUM,  SODIUM  AND  OTHER  ALKALIES 

60  cc.  of  the  filtrate  to  dryness  and  ignite  gently  to  remove  ammonium  salts. 
Dissolve  in  water,  filter,  and  determine  the  potassium  according  to  the  modified 
chlorplatinate  *  or  the  Lindo-Gladding  method. 

Organic  compounds.  When  it  is  desired  to  determine  the  total  potash  in 
organic  substances  such  as  cottonseed  meal,  tobacco  stems,  etc.,  saturate  10  grams 
with  strong  sulphuric  acid,  and  ignite  in  a  muffle  at  low  red  heat  to  destroy 
organic  matter.  Add  a  little  strong  hydrochloric  acid,  warm  slightly  to  loosen 
the  mass  from  the  dish,  dissolve  in  water,  filter,  and  determine  the  potassium 
according  to  the  modified  chloroplatinate  or  the  Lindo-Gladding  Tiethod.  * 

If  for  any  reason  it  is  desired  to  use  either  the  chloroplatinate  or  the  perchlorate 
method  in  the  determination  of  potassium,  interfering  substances,  including 
sulphates,  must  first  be  removed  from  the  solution. 

Procedure  for  Ashes  of  Plants.  Boil  20  grams  of  the  sample  with  30C  cc. 
of  water  for  thirty  minutes,  filter  into  a  500-cc.  flask,  and  wash  the  residue  thor- 
oughly with  hot  water.  Cool,  dilute  to  the  mark  and  mix.  Take  aliquots  for 
the  determination  of  the  alkalies.  The  solution  may  also  be  prepared  by  diges- 
tion with  hydrochloric  acid.2  This  treatment  is  preferable  when  all  the  constit- 
uents of  the  ash  are  to  be  determined. 

Procedure  for  Saline  Residues,  Soluble  Salts,  Brines,  etc.  In  the  case 
of  water-soluble  products,  the  convenience  of  the  analyst  usually  determines 
the  manner  of  preparing  the  solution.  Usually  it  is  preferable  to  weigh  out  a 
convenient  portion,  to  make  up  the  solution  to  definite  volume,  and  to  take  an 
aliquot  for  each  determination.  As  a  general  rule,  a  sample  should  be  taken 
sufficient  to  give  about  a  half  gram  of  solids.  Strong  brines  should  be  weighed 
and  not  measured. 

SEPARATIONS 
Separation  of  the  Alkali  Metals  from  other  Constituents 

Separation  from  the  Hydrogen  Sulphide  and  Ammonium  Sulphide 
Groups  of  Metals 

The  alkali  metals  are  usually  weighed  as  chlorides  or  sulphates,  and  in  gen- 
eral before  undertaking  their  determination,  all  other  bases  and  acids  must  first 
be  separated  from  them.  The  hydrogen  sulphide  and  the  ammonium  sulphide 
groups  of  metals  are  seldom  to  be  found  in  solutions  in  which  the  determination 
of  the  alkalies  is  desired.  If  these  are  present,  however,  they  may  be  readily 
precipitated  by  means  of  hydrogen  sulphide  and  ammonium  sulphide  as  detailed 
on  pages  142  and  254. 

^Separation  from  Silica 

*t  * 

Acidify  the  solution  with  hydrochloric  acid  and  evaporate  it  in  a  platinum 
or  porcelain  dish  on  the  water  bath  until  the  odor  of  hydrochloric  acid  in  the 
dry  residue  can  no  longer  be  detected.  Break  up  the  dry  mass  with  a  platinum 
or  glass  rod,  cool,  moisten  with  a  minimum  amount  of  concentrated  hydrochloric 

1  If  this  method  is  used,  it  will  not  be  absolutely  necessary  to  remove  the  calcium  by 
addition  of  ammonia  and  amonium  oxalate. 

a  Lunge,  "Technical  Methods  of  Analysis,"  2,  456, 1911.  D.  Van  Nostrand  Co., 
New  York. 


POTASSIUM,  SODIUM  AND  OTHER  ALKALIES     345 

acid,  dissolve  in  a  small   quantity   of  water,  filter  and  wash  the  residue  free 
from  chlorides.    In  the  presence  of  much  silica,  repeat  the  operation. 

Separation  from  Iron,  Aluminum,  Chromium,  Titanium,  Uranium, 
Phosphoric  Acid,  etc. 

If  phosphoric  acid  is  present  in  amounts  insufficient  to  combine  with  all  the 
iron,  alumina,  etc.,  or  is  absent  altogether,  heat  the  solution  to  boiling,  add  a  few 
drops  of  nitric  acid  to  oxidize  the  iron,  add  gradually  an  excess  of  ammonia, 
boil  for  a  minute  or  so,  allow  the  precipitate  to  settle,  and  filter.  Wash  the  pre- 
cipitate free  from  chlorides  with  hot  water. 

If  phosphoric  acid  is  present  in  the  solution  in  excess  of  that  required  to 
combine  with  the  iron,  alumina,  etc.,  heat  the  solution  to  boiling,  oxidize  with 
nitric  acid,  add  a  slight  excess  of  ferric  chloride  solution,  and  precipitate  with 
ammonia  as  described  above. 

When  the  precipitate  is  considerable,  it  should  be  dissolved  in  hydrochloric 
acid,  and  the  precipitation  repeated. 

If  chromates  are  present,  these  must  first  be  reduced  to  the  chromic  salt.  For 
this  purpose,  add  10  to  15  cc.  of  hydrochloric  acid  and  a  small  amount  of  alcohol 
to  the  solution  and  heat  on  the  water  bath  or  hot  plate  for  a  few  minutes.  Heat 
to  boiling  and  precipitate  with  ammonia  as  directed  above.  The  reduction 
may  also  be  done  by  boiling  with  sulphurous  acid. 

Separation  from  Sulphates 

Precipitate  the  sulphate  radical  as  BaS04  by  the  addition  of  a  slight  excess 
of  barium  chloride  to  the  hot  solution  as  directed  on  page  395  for  the  deter- 
mination of  S04.  Remove  the  excess  of  barium  chloride  by  addition  of  ammonia 
and  ammonium  carbonate. 

The  two  operations  may  be  combined  as  follows :  Add  a  slight  excess  of  bar- 
ium chloride  to  the  hot  solution  and  boil  for  a  few  minutes.  Then,  without 
filtering  off  the  BaS04,  add  an  excess  of  ammonia  and  ammonium  carbonate, 
allow  the  precipitate  to  settle,  filter,  and  wash  free  from  chlorides. 

Separation  from  Barium,  Calcium  and  Strontium 

To  the  not  too  concentrated  solution,  add  a  slight  excess  of  ammonia  and 
ammonium  carbonate,  heat  to  boiling,  allow  the  precipitate  to  settle,  filter  and 
wash  the  residue  a  few  times  with  hot  water.  Dissolve  the  precipitate,  which 
is  likely  to  contain  small  amounts  of  the  alkalies,  in  a  little  dilute  hydrochloric 
acid,  and  repeat  the  precipitation  with  ammonia  and  ammonium  carbonate. 
Filter  and  wash  the  residue.  Evaporate  the  combined  filtrates  to  dryness  in  a 
platinum  or  porcelain  dish  and  ignite  cautiously  at  a  very  faint  red  heat  to 
remove  ammonium  salts.  Dissolve  the  residue  in  a  little  water,  add  a  few  drops 
of  ammonia,  ammonium  carbonate,  and  ammonium  oxalate,  and  allow  to  stand 
for  several  hours  in  order  to  precipitate  the  last  traces  of  the  alkaline  earths. 
Filter  and  wash  the  residue  free  from  chlorides. 


346     POTASSIUM,   SODIUM  AND   OTHER  ALKALIES 


Separation  from  Iron,  Aluminum,  Chrominum,  Barium,  Calcium,  Strontium, 
Phosphates,  Sulphates,  etc.,  in  One  Operation 

To  the  hot  solution  add  a  slight  excess  of  barium  chloride  and  boil  for  a  few 
minutes.  Then,  without  filtering  off  the  BaS04,  add  an  excess  of  ammonia  and 
ammonium  carbonate,  heat  to  boiling,  and  allow  the  precipitate  to  settle.  Filter 
and  wash  free  from  chlorides  with  hot  water.  After  evaporating  the  filtrate  to 
dryness,  removing  the  ammonium  salts  by  ignition,  and  dissolving  the  residue 
in  a  little  water,  precipitate  the  last  traces  of  barium  and  calcium  by  addition  of 
a  few  drops  of  ammonia,  ammonium  carbonate,  and  ammonium  oxalate.  By  this 
procedure  a  small  portion  of  the  alkalies  is  retained  by  the  precipitate  and  lost. 

Separation  from  Boric  Acid 

Acidify  the  solution  strongly  with  hydrochloric  acid  and  evaporate  to  dry- 
ness.  Stir  up  the  residue  with  15  to  20  cc.  of  pure  methyl  alcohol  and  cau- 
tiously evaporate  on  a  water  bath  at  not  too  high  a  temperature.  Moisten  the 
residue  with  a  drop  or  two  of  concentrated  hydrochloric  acid,  add  15  cc.  of  methyl 
alcohol,  and  again  take  to  dryness.  Repeat  the  evaporation  with  methyl  alcohol 
a  third  time.  This  should  be  ample  for  the  complete  removal  of  half  a  gram 
of  B203. 

Separation  from  Magnesium 

Mercuric  Oxide  Method.1  After  removing  other  bases  and  acids,  evap- 
orate the  solution  of  the  chlorides  to  dryness,  expel  ammonium  chloride  by 
gentle  ignition,  .and  dissolve  the  residue — except  for  the  small  amount  of  mag- 
nesium oxide  present — by  warming  with  a  little  water.  Add  an  excess  of  mer- 
curic oxide  in  the  form  of  a  thin  paste  prepared  by  shaking  up  freshly  precipi- 
tated mercuric  oxide  in  water.  Evaporate  the  mixture  to  complete  dryness  on 
the  water  bath  with  frequent  stirring,  dry  thoroughly  and  ignite  gently  at  first 
and  then  more  strongly  until  all  the  mercuric  chloride  present  has  been  volatilized. 
(Be  careful  not  to  inhale  the  fumes.)  The  whole  of  the  unchanged  mercuric  oxide 
need  not  be  expelled  by  ignition.  Digest  the  residue,  composed  of  the  excess  of 
mercuric  oxide,  the  precipitated  magnesium  oxide,  and  the  alkali  chlorides,  with 
a  small  amount  of  hot  water,  filter  rapidly,  and  wash  with  successive  portions 
of  hot  water,  first  by  decantation  and  then  on  the  filter,  but  do  not  prolong  the 
operation  unnecessarily.  If  desired,  determine  the  magnesium  in  the  residue  by 
expelling  the  mercuric  oxide  by  ignition  and  weighing  the  magnesium  oxide. 
Acidify  the  filtrate,  which  contains  the  alkalies,  with  hydrochloric  acid,  evaporate 
to  dryness,  gently  ignite,  cool  and  weigh.  If  the  residue  contains  a  small 
amount  of  magnesium,  as  it  usually  does,  determine  the  magnesium  in  an  aliquot 
and  apply  the  necessary  correction.  The  mercuric  oxide  should  be  tested  for 
alkalies  by  volatilizing  a  portion  and  testing  the  residue. 

The  Barium  Hydroxide  Method.1  Evaporate  the  solution,  which  may  con- 
tain chlorides,  sulphates  or  nitrates,  to  dryness  and  gently  ignite  to  remove 
ammonium  salts.  Warm  the  residue  with  a  small  amount  of  water  and  treat 
the  hot  neutral  solution  so  obtained  with  baryta  water  until  no  more  precipitate 
is  formed  and  barium  hydroxide  remains  in  -slight  excess.  Boil,  filter  and  wash 

1  Fresenius,  "  Quantitative  Chemical  Analysis,"  1,  610,  1908,  John  Wiley  &  Sons, 
New  York. 


POTASSIUM,   SODIUM  AND   OTHER  ALKALIES     347 

the  precipitate  with  hot  water.  If  desired,  determine  the  magnesium  in  the 
residue.  Treat  the  nitrate,  which  contains  the  alkalies,  barium  and  a  trace 
of  magnesium,  with  an  excess  of  ammonia  and  ammonium  carbonate  to  remove 
the  barium.  Acidify  the  nitrate  with  hydrochloric  acid  and  evaporate  to  dry- 
ness,  ignite  and  weigh.  This  residue  will  contain  a  small  amount  of  magnesium 
which  may  be  determined  in  an  aliquot  and  a  correction  applied. 

Remark.  The  barium  hydroxide  method  is  applicable  in  the  presence  of 
lithium. 

The  Ammonium  Phosphate  Method.1  To  the  hot  solution,  add  an  excess  of 
ammonia  and  ammonium  chloride,  and  precipitate  the  magnesium  by  adding  a 
slight  excess  of  ammonium  phosphate.  Allow  the  mixture  to  stand  an  hour 
or  so,  filter  and  wash  the  residue  with  2%  ammonia  solution.  Expel  most  of  the 
free  ammonia  from  the  nitrate  by  evaporation,  acidify  very  slightly  with  hydro- 
chloric acid,  and  add  an  excess  of  ferric  chloride  solution,  which  should  color 
the  solution  slightly  yellow.  Neutralize  the  solution  with  ammonium  carbonate, 
heat  to  boiling,  and  filter  off  the  basic  ferric  phosphate,  washing  the  residue  with 
hot  water.  Evaporate  the  filtrate  to  dryness,  ignite  to  expel  ammonium  salts, 
and  determine  the  alkalies  in  the  residue.  Magnesium  may  also  be  separated  by 
precipitation  as  magnesium  ammonium  arsenate  2  or  magnesium  ammonium 
carbonate.1 

Separation  of  the  Alkali  Metals  from  One  Another 

Separation  of  Sodium  from  Potassium 

After  weighing  the  sodium  and  potassium  together  as  chlorides,  dissolve  the 
residue  in  water  and  precipitate  the  potassium  as  chloroplatinate  or  perchlorate 
according  to  one  of  the  methods  detailed  under  Determination  of  Potassium. 

Separation  of  Lithium  from  Sodium  and  Potassium 

Extract  the  dry  chlorides  with  amyl  alcohol  as  prescribed  under  the  Gooch 
method,  or  with  alcohol  saturated  with  hydrochloric  acid  gas  as  detailed  under 
the  Rammelsberg  method. 

Separation  of  Lithium  and  Sodium  from  Potassium,  Rubidium,  and  Caesium 

Precipitate  the  potassium,  rubidium,  and  caesium  as  chloroplatinates  as 
described  under  the  chloroplatinate  method  for  the  estimation  of  potassium. 
Evaporate  the  filtrate  to  dryness  and  ignite  gently  with  'a  little  oxalic  acid  to 
reduce  the  platinum,  or  else  dissolve  the  residue  in  water  and  pass  a  current  of 
hydrogen  through  the  hot  solution  to  reduce  the  platinum.  In  any  case,  filter 
off  the  reduced  platinum  and  determine  lithium  and  sodium  in  the  filtrate. 

1  Fresenius,  op.  cit. 

2  Browning  and  Drushel,  Am.  J.  Sci.  (4),  23,  293,  1907. 


348     POTASSIUM,   SODIUM  AND  OTHER  ALKALIES 

METHODS  FOR  DETERMINATION  OF  SODIUM 
Determination  as  Sodium  Chloride 

Sodium  is  commonly  weighed  as  NaCl  when  it  is  already  present  as  such  or 
after  conversion  of  other  forms  into  the  chloride.  In  the  case  of  salts  of  volatile 
acids,  such  as  nitrates  for  instance,  the  transformation  is  made  by  evaporating 
the  solution  to  dryness  with  hydrochloric  acid  repeatedly  or  until  only  the  chloride 
remains.  When  the  sodium  is  present  as  a  salt  of  a  non-volatile  acid,  the  latter 
is  removed  and  the  transformation  effected  according  to  the  methods  under 
Separations. 

Usually  the  solution  in  which  sodium  chloride  is  to  be  determined  will  con- 
tain ammonium  salts  from  some  previous  operation.  In  such  cases,  proceed  as 
follows:  Evaporate  the  sodium  chloride  solution,  which  must  contain  no  other 
non-volatile  substance,  in  a  platinum  dish  to  complete  dryness  on  the  water  bath. 
Cover  the  dish  with  a  watch-glass,  and  cautiously  dry  the  residue  in  an  air  bath 
at  110  to  130°  C.  Make  sure  that  no  loss  of  sodium  chloride  is  sustained  by 
decrepitation  during  drying  and  subsequent  ignition.  Heat  the  dish  and  contents 
over  a  free  flame  held  in  the  hand  and  moved  back  and  forth  under  the  dish  in 
Order  to  remove  ammonium  salts.  But  to  avoid  loss  of  sodium  chloride  by 
volatilization,  take  care  not  to  heat  the  dish  to  more  than  a  faint  redness  in  any 
one  spot  and  not  to  raise  the  temperature  of  the  salt  above  incipient  fusion.  Cool 
the  residue,  dissolve  it  in  a  little  water,  and  filter  from  the  carbonaceous  matter 
into  a  weighed  platinum  dish.  Acidify  the  filtrate  with  hydrochloric  acid  and 
evaporate  it  to  dryness  on  the  water  bath.  Dry  the  residue  at  100  to  130°  C.  in 
an  air  bath,  ignite  cautiously  over  a  free  flame,  taking  the  precautions  mentioned 
above  to  prevent  loss  of  sodium  chloride,  cool  in  a  desiccator,  and  weigh. 

Determination  as  Sodium  Sulphate 

Sodium  is  often  determined  by  weighing  as  Na2S04  when  it  is  present  as  such 
or  after  conversion  of  other  forms  into  the  sulphate.  In  the  case  of  salts  of  vola- 
tile acids,  the  change  into  the  sulphate  is  made  by  simply  evaporating  the  solu- 
tion with  a  slight  excess  of  sulphuric  acid.  With  salts  of  non-volatile  acids,  the 
transformation  is  effected  according  to  the  methods  under  Separations.  When 
the  sodium  is  present  as  an  organic  salt,  the  substance  is  moistened  with  con- 
centrated sulphuric  acid  and  carefully  heated  over  a  free  flame  until  fumes  cease 
to  come  off.  The  residue  is  dissolved  in  water  and  filtered  from  the  carbonaceous 
matter. 

As  a  rule  the  solution  in  which  sodium  sulphate  is  to  be  determined  will  con- 
tain an  excess  of  sulphuric  acid.  In  such  cases,  evaporate  the  solution  to  dryness 
in  a  weighed  platinum  dish,  and  cautiously  ignite  the  dry  residue  until  fumes 
cease  to  come  off.  Cool,  add  a  lump  of  ammonium  carbonate  to  the  contents  of 
the  dish,  and  ignite  a  second  time  at  dull  red  heat  until  no  more  fumes  are  given 
off.  Cool  in  a  desiccator  and  weigh  as  Na2S04.  Repeat  the  ignition  with  the 
addition  of  ammonium  carbonate  until  a  constant  weight  is  obtained. 

In  case  an  excess  of  sulphuric  acid  is  not  present,  evaporate  the  solution  to 
dryness  in  a  weighed  platinum  dish,  ignite,  cool  in  a  desiccator  and  weigh  as 
Na2S04. 


POTASSIUM,   SODIUM   AND   OTHER  ALKALIES     349 

Determination  by  Difference 

Ordinarily  sodium  and  potassium  are  weighed  together  as  chlorides  or  sul- 
phates as  detailed  above  for  sodium.  Potassium  is  then  determined  by  one  of 
the  methods  given  below,  and  the  value  for  sodium  obtained  by  difference. 


METHODS  FOR  DETERMINATION^  POTASSIUM 
Determination  as  Potassium  Chloride  or  Potassium  Sulphate 

Potassium  may  be  weighed  as  chloride  or  sulphate.  The  procedure  is  the  same 
as  that  described  for  sodium.  Observe,  however,  that  the  potassium  salts  are  a 
little  more  volatile  than  the  corresponding  sodium  salts,  so  that  greater  care 
must  be  taken  not  to  lose  potassium  by  volatilization. 

The  Chloroplatinate  Method 

Application.  This  method  is  applicable  in  the  presence  of  the  chlorides  of 
sodium,  lithium,  magnesium,  calcium,  and  strontium. 

Principle.  Potassium  chloroplatinate  is  practically  insoluble  in  strong  alcohol 
while  the  other  chloroplatinates  are  readily  soluble. 

Procedure.  Treat  the  aqueous  solution  of  the  alkali  chlorides  contained 
in  a  small  porcelain  dish  with  slightly  more  than  enough  chloroplatinic  acid  to 
convert  all  the  chlorides  present  into  the  corresponding  chloroplatinates.  The 
chloroplatinic  acid  solution  should  contain  the  equivalent  of  1  gram  of  platinum 
in  each  10  cc.1  Evaporate  the  solution  on  the  steam  bath  to  a  syrupy  consistency, 
i.e.,  until  solidification  occurs  on  cooling.  Flood  the  cooled  residue  with  a  small 
quantity  of  alcohol  of  at  least  80%  strength,  grind  thoroughly  with  a  pestle  made 
by  enlarging  the  end  of  a  glass  rod,  and  allow  to  stand  one-half  hour.  Pour  the 
liquid  through  a  previously  weighed  Gooch  crucible  containing  an  asbestos  mat, 
and  before  adding  more  alcohol,  rub  up  the  residue  again  with  the  glass  pestle. 
Now  continue  the  washing  by  decantation  with  small  portions  of  alcohol  until 
the  wash  liquid  becomes  colorless.  Transfer  the  precipitate  to  the  crucible  and 
wash  two  or  three  times  with  alcohol.  Dry  at  130°  C.,  cool  in  a  desiccator,  and 
weigh.  Repeat  the  drying  until  a  constant  weight  is  obtained.  Multiply  the 
weight  of  K2PtCle  by  0.161  to  obtain  the  weight  of  K;  by  0.194  to  obtain  K20; 
and  by  0.307  to  obtain  KC1. 

Remarks.  This  method  is  considered  to  be  the  most  accurate  known  for 
the  estimation  of  potassium.  Care  should  be  taken  not  to  conduct  the  evapora- 
tion at  too  high  a  temperature  nor  let  it  go  too  far,  as  this  may  cause  the  forma- 
tion of  anhydrous  sodium  chloroplatinate,  which  dissolves  slowly  in  alcohol. 
Too  large  a  volume  of  alcohol  for  washing  should  be  avoided,  as  K2PtCl6  is 
slightly  soluble  in  alcohol,  especially  that  of  80%.  For  this  reason  95%  alcohol 
is  preferable  for  the  washing. 

Instead  of  using  a  Gooch  crucible,  the  precipitate  may  be  filtered  on  paper, 
dried,  washed  through  the  filter  with  hot  water  into  a  weighed  platinum  dish, 
evaporated  to  dryness,  and  heated  at  130°  C.  to  constant  weight. 

1  For  methods  of  preparing  chloroplatinic  acid  from  scrap  platinum  and  from  plati- 
num residues,  see  Precht,  Z.  Anal.  Chem.,  18,  509,  1879;  Vogel  and  Haefcke,  Landw. 
Vers.  Sta.,  47,  134,  1896. 


350     POTASSIUM,  SODIUM  AND   OTHER  ALKALIES 


The  Modified  Chloroplatinate  Method  l 

Application.  The  method  is  applicable  in  the  presence  of  chlorides,  sul- 
phates, phosphates,  nitrates,  carbonates,  borates  and  silicates,  salts  of  sodium, 
barium,  calcium,  strontium,  magnesium,  iron  and  alumina,  and  is  especially 
suited  for  the  estimation  of  potassium  in  salines,  potassium  salts,  and  fertilizers 
in  which  only  the  potassium  is  desired. 

Principle.  On  evaporating  a  solution  containing  potassium  with  a  slight 
excess  of  chloroplatinic  acid,  the  potassium  is  completely  transformed  into 
potassium  chloroplatinate  which  is  insoluble  in  strong  alcohol,  while  any  of  the 
other  chloroplatinates  which  may  be  formed  are  either  dissolved  or  decomposed  by 
alcohol,  so  that  the  excess  of  chloroplatinic  acid  may  be  readily  removed.  After 
dissolving  the  K^PtCU  along  with  any  other  soluble  salts  contained  in  the  residue 
in  hot  water,  the  platinum  is  precipitated  from  the  solution  by  magnesium,  and 
from  the  weight  of  platinum  so  obtained,  the  amount  of  potassium  present  is 
calculated. 

Procedure.  To  the  solution  slightly  acidified  with  hydrochloric  acid,  add 
chloroplatinic  acid  solution  slightly  in  excess  of  that  necessary  for  the  complete 
precipitation  of  the  potassium  present  and  evaporate  the  solution  on  the  steam 
bath  to  a  syrupy  consistency,  i.e.,  until  solidification  occurs  on  cooling.  Flood 
the  cooled  residue  with  a  small  quantity  of  alcohol  of  at  least  80%  strength,  grind 
thoroughly  with  a  pestle  made  by  enlarging  the  end  of  a  glass  rod,  and  allow  to 
stand  one-half  hour.  The  alcoholic  solution  should  be  colored  if  an  excess  of 
chloroplatinic  acid  has  been  used.  Pour  the  liquid  through  a  small  filter,  using 
suction  if  desired,  and  before  adding  more  alcohol,  rub  up  the  residue  again  with  the 
pestle.  Now  continue  the  washing  by  decantation  with  small  portions  of  alcohol 
until  the  wash  liquid  becomes  colorless.  Three  or  four  washings  usually  suffice. 
Transfer  the  precipitate  to  the  filter  and  wash  two  or  three  times  with  alcohol. 

Dissolve  the  precipitate  of  K2PtCle  along  with  any  other  soluble  salts  present 
in  hot  water,  washing  it  through  the  filter  into  a  beaker  of  convenient  size.  To 
the  hot  solution  add  about  1  cc.  of  concentrated  HC1  and  approximately  0.5 
gram  magnesium  ribbon  pressed  into  the  form  of  a  ball  for  every  0.2  gram  potas- 
sium present,  stirring  the  solution  and  holding  the  magnesium  at  the  bottom  of 
the  beaker  by  means  of  a  glass  rod.  When  the  action  has  practically  ceased,  add 
a  few  cc.  of  hydrochloric  acid  and  allow  the  fluocculent  platinum  to  settle,  pref- 
erably by  allowing  the  beaker  to  set  for  an  hour  on  the  hot  plate.  The  super- 
natant liquid  should  be  perfectly  clear  and  limpid  like  water  if  reduction  is  com- 
plete. To  make  sure,  add  more  magnesium,  in  which  case  the  solution  will  darken 
if  reduction  be  incomplete.  To  the  completely  reduced  solution,  add  concentrated 
hydrochloric  acid,  and  boil  to  dissolve  any  basic  salts,  filter  on  paper  or  a  Gooch, 
wash  thoroughly  with  hot  water,  ignite  in  platinum  or  porcelain  and  weigh.  Mul- 
tiply the  weight  of  the  platinum  so  obtained  by  0.4006  to  obtain  the  weight 
ofK;  by  0.4826  to  obtain  K20;  and  by  0.7639  to  obtain  KC1. 

Remarks.  If  the  solution  contains  very  large  amounts  of  iron,  alumina, 
or  silica,  it  is  perferable  to  remove  the  greater  part  of  these  before  proceeding  to 
the  determination  of  potassium.  Care  should  be  taken  to  insure  the  complete 
removal  of  the  soluble  chloroplatinates  from  the  residue  without  the  use  of  an 

1  Hicks,  J.  Ind.  Eng.  Chem.?  5,  650,  1913.  A  good  bibliography  on  reduction 
methods  is  contained  in  this  article. 


POTASSIUM,   SODIUM  AND   OTHER  ALKALIES     351 

excessive  amount  of  alcohol,  and  also  that  the  subsequent  reduction  of  the  potas- 
sium chloroplatinate  with  magnesium  be  complete. 

Lindo=Qladding  Method  1 

Application.  This  method  is  applicable  in  the  presence  of  chlorides,  sul- 
phates, and  phosphates  of  the  alkalies  and  magnesium. 

Principle.  The  potassium  is  precipitated  as  K2PtCl6,  and  the  soluble  chloro- 
platinates  removed  by  washing  with  80%  alcohol.  The  impurities  in  the  precip- 
itate are  then  washed  out  by  a  strong  solution  of  ammonium  chloride  saturated 
with  K2PtCl6,  and  the  wash  solution  is  removed  by  again  washing  with  alcohol. 
The  purified  K2PtCl6  is  finally  dried  and  weighed. 

Procedure.  To  the  solution,  slightly  acidified  with  hydrochloric  acid,  add 
an  excess  of  chloroplatinic  acid  solution,  and  evaporate  on  the  water  bath  to  a  thick 
paste.  Treat  the  residue  with  80%  alcohol,  avoiding  the  absorption  of  ammonia. 
Wash  the  precipitate  thoroughly  with  80%  alcohol  both  by  decantation  and  on 
the  filter,  continuing  the  washing  after  the  filtrate  is  colorless.  Wash  finally 
with  10  cc.  of  ammonium  chloride  solution  prepared  as  follows:  Dissolve  100 
grams  of  pure  ammonium  chloride  in  500  cc.  of  water,  add  from  5  to  10  grams  of 
potassium  chloroplatinate,  and  shake  at  intervals  of  six  to  eight  hours.  Allow 
the  mixture  to  settle  over  night  and  filter.  Repeat  the  washing  with  successive 
portions  of  the  ammonium  chloride  solution  five  or  six  times  in  order  to  remove 
the  impurities  from  the  precipitate.  Wash  again  thoroughly  with  80%  alcohol, 
dry  for  thirty  minutes  at  100°  C.  and  weigh  as  K2PtCls.  The  precipitate  should 
be  perfectly  soluble  in  water.  Multiply  the  weight  of  K2PtCl6  by  0.161  to  obtain 
the  weight  of  K;  by  0.194  to  obtain  K20;  and  by  0.307  to  obtain  KC1. 

The  Perchlorate  Method2 

Application.  This  method  is  applicable  in  the  presence  of  chlorides  and 
nitrates  of  barium,  calcium,  magnesium  and  the  alkali  metals,  and  also  in  the 
presence  of  phosphates.  Sulphates  should  not  be  present. 

Principle.  The  separation  depends  on  the  insolubility  of  potassium  perchlor- 
ate,  and  the  solubility  of  sodium  and  other  perchlorates  in  97%  aclohol. 

Procedure.  To  the  neutral  or  slightly  acidified  solution,  add  twice  as  much 
perchloric  acid 3  as  is  required  to  convert  all  the  bases  present  into  perchlorates 
and  evaporate  on  the  water  bath  with  stirring  to  a  syrupy  consistency.  Add  a 
little  hot  water  and  continue  the  evaporation  with  constant  stirring  until  all  the 
hydrochloric  acid  is  expelled  and  heavy  fumes  of  perchloric  acid  are  given  off.  If 
necessary,  replace  the  perchloric  acid  lost  by  volatilization.  Stir  up  the  cooled 
mass  thoroughly  with  20  cc.  of  97%  alcohol  to  which  0.2%  perchloric  acid  has 
been  added,  but  avoid  breaking  up  the  potassium  perchlorate  crystals  too  finely 
or  else  they  may  pass  through  the  filter.  Allow  the  mixture  to  settle,  and  decant 
the  alcohol  off  through  a  Gooch  crucible.  Wash  several  times  with  wash-alcohol, 
and  transfer  the  precipitate  to  the  filter.  Wash  with  50  to  75  cc.  of  pure  97% 
alcohol,  dry  at  130°  C.,  and  weigh.  Multiply  the  weight  of  KC104  by  0.2825  to 
obtain  the  weight  of  K;  by  0.3402  to  obtain  K20;  and  by  0.5382  to  obtain  KC1. 

'U.  S.  Dept.  Agri.,  Bu.  Chem.  Bull.  107  (revised),  11,  1907. 

2  Wense,  Zeit.  Angew.  Chem.,  691,  1891;  233,  1892.    Caspari,  Zeit.  Angew,  Chem., 
38,  1893. 

3  For  the  preparation  of  perchloric  acid  see  Willard,  J.  Am.  Chem.  Soc.,  34,  1480, 
1912;  Kreider,  Am.  J.  Sci.,  (3),  49,  443,  1895.     3.  Anorg.  Chem.,  9,  342,  1895. 


352     POTASSIUM,   SODIUM  AND   OTHER  ALKALIES 


Other  Methods 

Among  the  more  important  of  other  methods  which  have  been  proposed 
and  used  for  the  determination  of  potassium,  may  be  mentioned  the  cobaltinitrite 
method, 1  which  has  been  studied  by  the  Association  of  Official  Agricultural  Chem- 
ists and  considered  to  be  unreliable; 2  the  bitartrate  method; 3  the  colorimetric 
method; 4  and  the  spectroscopic  method.6 

Determination  of  Sodium  and  Potassium  by   Indirect  Method 

After  removing  all  other  constituents,  weigh  the  sodium  and  potassium  as  chlor- 
ides. Dissolve  the  weighed  residue  in  water  and  determine  the  chlorine  gravi- 
metrically  by  precipitation  as  AgCl  or  volumetrically  by  titration  with  standard 
silver  nitrate  (potassium  chromate  indicator).  From  the  weight  of  the  combined 
salts  and  the  weight  of  the  chlorine,  calculate  the  amount  of  sodium  and  potas- 
sium as  follows: 

Let  x  =weight  of  NaCl+KCl- 

y  =  weight  of  Cl. 

Then  Na  =3.00%  -  1.428z; 

K=2.428z-4.004?/. 

The  method  is  satisfactory  when  sodium  and  potassium  are  present  in  about 
equal  quantities. 

Determination  of  Magnesium,   Sodium   and   Potassium   in   the 
Presence  of  One  Another 

In  the  usual  course  of  analysis,  magnesium,  sodium  and  potassium  are  sepa- 
rated as  chlorides  from  all  other  constituents.  Instead  of  going  through  the 
tedious  process  of  separating  the  magnesium  from  the  alkalies,  the  magnesium, 
sodium,  and  potassium  may  be  accurately  determined  in  the  presence  of  each 
other  as  follows: 

Treat  the  solution  containing  these  constituents  with  slightly  more  than 
enough  sulphuric  acid  to  convert  all  three  bases  into  sulphates,  evaporate  it  to 
dryness  on  the  water  bath,  and  ignite  gently  at  first  and  then  at  dull  red  heat  to 
break  up  bisulphates  and  expel  the  excess  of  sulphuric  acid.  To  hasten  the 
decomposition  of  the  bisulphates,  cool,  add  a  lump  of  ammonium  carbonate, 
and  heat  a  second  time.  Cool  in  a  desiccator  and  weigh.  Repeat  the  heating 
with  the  addition  of  ammonium  carbonate  until  a  constant  weight  is  obtained. 
Dissolve  the  residue  in  water  and  dilute  to  definite  volume.  Determine  the 
potassium  in  one  portion  according  to  one  of  the  methods  described  above,  and 
the  magnesium  in  a  second  portion  as  described  on  page  255.  Deduct  the 
weight  of  magnesium  and  potassium  sulphates  from  the  weight  of  the  combined 
sulphates  to  obtain  the  amount  of  sodium  sulphate. 

^ddie  and  Wood,  J.  Chem.  Soc.,  77,  1076,  1900;  Drushel,  Am.  J.  Sci.  (4),  24, 
433,  1907;  26,  329,  555,  1908;  Bowser.  J.  Am.  Chem.  Soc.,  33,  1752,  1911. 

1 U.  S.  Dept.  Agri.  Bu.,  Chem.,  Bull.  132,  137,  152,  159. 

'Bayer,  Chem.  Zeit.,  17,  686,  1893. 

4  Cameron  and  Failyer,  J.  Am.  Chem.  Soc.,  25,  1063,  1903;  Hill,  J.  Am.  Chem.  Soc., 
25,  990,  1903. 

'Gooch  and  Hart,  Am.  J.  Sci.  (3),  24,  448,  1891. 


POTASSIUM,  SODIUM  AND  OTHER  ALKALIES     353 

METHODS  FOR  DETERMINATION  OF  LITHIUM 
Determination  as  Lithium  Chloride 

Lithium  may  be  weighed  as  LiCl.  The  procedure  is  practically  the  same 
as  that  described  for  sodium,  but  since  lithium  chloride  is  very  hygroscopic,  this 
salt  must  be  weighed  out  of  contact  with  the  air.  For  this  purpose  the  lithium 
chloride  is  ignited  in  a  platinum  crucible,  cooled  in  desiccator,  and  the  crucible 
and  contents  weighed  in  a  glass-stoppered  weighing  bottle. 

Determination  as  Lithium  Sulphate 

Lithium  is  weighed  preferably  as  Li2S04.  The  procedure  is  the  same  as  that 
described  for  sodium,  but  since  lithium  bisulphate  is  easily  broken  up  on  heating, 
it  is  not  necessary  to  ignite  with  ammonium  carbonate. 

The  Qooch  Method1 

Principle.  Lithium  chloride  is  readily  soluble  in  amyl  alcohol,  while  sodium 
and  potassium  chlorides  are  not. 

Procedure.  Concentrate  the  solution  as  far  as  possible  by  evaporation, 
transfer  it  to  a  50-cc.  Erlenmeyer  flask,  add  a  small  amount  of  amyl  alcohol  and 
heat  cautiously  on  an  asbestos  plate  until  the  water  has  been  expelled  and  the  boil- 
ing-point of  the  solution  rises  to  about  that  of  pure  amyl  alcohol  (132°  C.). 
To  prevent  bumping  during  this  treatment,  pass  a  current  of  dry  air  through  the 
solution.  When  all  the  water  has  been  removed,  the  sodium  and  potassium 
chlorides,  together  with  some  LiOH  will  separate  from  the  solution.  Decant  the 
solution  through  a  filter  and  wash  the  residue  several  times  with  hot  amyl 
alcohol.  Moisten  the  residue  with  dilute  hydrochloric  acid,  dissolve  in  a  little 
water  and  repeat  the  extraction  with  amyl  alcohol.  If  much  lithium  chloride 
is  present,  it  will  be  necessary  to  repeat  the  extraction  with  amyl  alcohol  three  or 
four  times.  Evaporate  the  combined  filtrates  and  washings  to  dryness  and  dis- 
solve in  a  little  dilute  sulphuric  acid.  Filter  from  the  carbonaceous  matter  into 
a  weighed  platinum  dish,  evaporate  to  dryness,  and  remove  the  excess  of  sulphuric 
acid  by  gentle  heating.  Ignite  the  residue  at  dull  redness,  cool  in  a  desiccator, 
and  weigh  as  Li2S04. 

Remarks.  For  very  accurate  work,  account  must  be  taken  of  the  fact  that 
the  lithium  sulphate  obtained  according  to  the  procedure  just  described  always 
contains  small  amounts  of  potassium  and  sodium  sulphates,  if  these  metals 
were  originally  present.  To  correct  for  this,  deduct  0.00041  gram  for  every  10  cc. 
of  the  filtrate  exclusive  of  the  washings  in  case  only  sodium  chloride  was  present, 
or  0.00051  if  only  potassium  chloride  was  present,  and  0.00092  if  both  sodium  and 
potassium  chlorides  were  present. 

1  Proc.  Am.  Acad.  Arts.  Sci.,  22  (N.  S.  14),  177,  1886. 


354     POTASSIUM,  SODIUM  AND  OTHER  ALKALIES 

The  Rammelsberg  Method  1 

Principle.  Anhydrous  lithium  chloride  is  soluble  in  equal  parts  of  alcohol 
and  ether  which  have  been  saturated  with  hydrochloric  acid  gas,  while  the 
chlorides  of  sodium  and  potassium  are  practically  insoluble  in  this  mixture. 

Procedure.  Evaporate  the  solution  of  the  chlorides  to  dryness  in  a  small 
flask  provided  with  a  two-hole  stopper.  During  the  evaporation,  pass  a  current 
of  dry  air  through  the  flask.  Place  the  flask  containing  the  dry  residue  in  an  oil 
or  air  bath  and  heat  for  half  an  hour  at  140  to  150°  C.,  during  which  time  pass 
dry  hydrochloric  acid  gas  through  the  flask.  Cool  in  a  current  of  hydrochloric 
acid  gas,  treat  the  residue  with  a  few  cc.  of  absolute  alcohol  which  has  been  satu- 
rated with  hydrochloric  acid  gas,  and  add  an  equal  volume  of  absolute  ether. 
Close  the  flask  tightly  and  allow  it  to  stand  with  frequent  shaking  for  twelve 
hours.  Pour  the  solution  through  a  filter,  wet  with  the  alcohol-ether  mixture  and 
wash  the  residue  three  times  by  decantation  with  the  alcohol-ether  mixture. 
Add  a  few  more  cc.  of  the  alcohol-ether  saturated  with  hydrochloric  acid  gas 
to  the  contents  of  the  flask  and  allow  to  stand  again  for  twelve  hours.  Pour  the 
liquid  through  a  filter,  and  wash  the  residue  by  decantation  with  the  alcohol- 
ether  mixture  until  the  residue  tested  in  the  spectroscope  shows  the  complete 
absence  of  lithium.  Carefully  evaporate  the  combined  alcohol-ether  extract  to 
dryness  on  a  lukewarm  water  bath.  Dissolve  the  residue  in  sufficient  dilute 
sulphuric  acid  to  convert  all  the  lithium  into  the  sulphate,  transfer  the  solution 
to  a  weighed  platinum  dish,  evaporate  to  dryness  on  the  water  bath,  and  finally 
ignite  gently.  Cool  the  residue  in  a  desiccator  and  weigh  as  lithium  sulphate. 

NOTE.  Lithium  may  also  be  precipitated  and  weighed  as  Li3PO4,2  or  it  may  be  pre- 
cipitated as  LiF 3  and  then  changed  into  the  sulphate  and  weighed. 

Spectroscopic  Method  4 

Dissolve  the  lithium  salt  containing  small  amounts  of  sodium  and  potassium 
resulting  from  the  separation  by  the  Gooch  or  Rammelsberg  methods  in  5  or  10  cc. 
of  water,  depending  on  the  amount  of  lithium  present.  Gradually  add  measured 
amounts  of  this  solution  to  a  known  volume  of  water — testing  the  solution  from 
time  to  time  in  the  spectroscope — until  the  lithium  line  appears.  When  only 
traces  of  lithium  are  present,  it  is  better  to  dissolve  the  lithium  salt  in  a  little 
water  and  dilute  to  the  vanishing  point  of  the  lithium  line.  Make  the  spectro- 
scopic  examination  as  follows:  Prepare  a  loop  by  winding  a  platinum  wire  four 
times  around  a  No.  10  wire.  Plunge  the  loop  into  the  solution,  and  remove 
with  the  axis  parallel  to  the  surface  of  the  water.  Evaporate  the  drop  to  dry- 
ness  carefully,  ignite  in  the  Bunsen  flame,  and  observe  through  a  good  spectro- 
scope. 

Before  undertaking  the  determination,  standardize  the  instrument  and  plati- 
num loop  by  carrying  out  the  determination  with  known  amounts  of  lithium. 

The  method  gives  satisfactory  results  when  only  an  approximation  is  desired. 
For  weighable  amounts  of  lithium,  the  Gooch  method  is  preferable. 

1  Treadwell,  "Analytical  Chemistry,"  2,  55, 1911.     John  Wiley  &  Sons,  N.  Y. 

2  Mayer,  Ann.  Chem.  Pharm.,  98,  193,  1856.      Merling,  3  Anal.  Chem.,  18,  563, 
1879. 

3  Carnot,  3  Anal.  Chem.,  29,  332,  1890. 

4  Skinner  and  Collins,  U.  S.  Dept.  Agri.  Bu.  Chem.,  Bull.  153.     A  good  bibliography 
is  included  in  this  bulletin. 


POTASSIUM,   SODIUM   AND   OTHER  ALKALIES     355 


Determination  of  Sodium,  Potassium,  and  Lithium  in  the  Pres= 
ence  of  One  Another 

Weigh  the  combined  bases  as  sulphates,  observing  the  precautions  detailed 
under  Determination  of  Sodium,  dissolve  in  water  and  dilute  to  definite  vol- 
ume. In  one  portion  determine  the  potassium  and  in  a  second  portion  determine 
the  lithium  by  the  Gooch  or  Rammelsberg  method.  Obtain  the  value  for  the 
sodium  by  difference. 


ft  re  c /ay 
Cylinder 


Crucible 
8c/7?.x  /.Scrr?. 


Determination  of  the  Alkalies  in  Silicates 

J.  Lawrence  Smith  method * 

Principle.  By  heating  the  substance  with  1  part  ammonium  chloride  and 
8  parts  calcium  carbonate,  and  leaching  the  sintered  mass  with  water,  the  alka- 
lies are  obtained  in  solution  in  the  form  of  chlorides  along  with  some  calcium, 
while  the  remaining  metals  are  for  the  most  part  left  behind  as  insoluble  oxides, 
and  the  silica  is  changed  to  calcium  silicate. 

Procedure.  Triturate  0.5  gram  of  the  finely  powdered  mineral  with  an  equal 
quantity  of  pure  ammonium  chloride  in  an  agate  mortar,  add  3  grams  of  pre- 
cipitated calcium  carbonate  2  and  mix  intimately  with  the  former.  Transfer  the 
mixture  to  a  platinum  crucible  (pref- 
erably the  J.  Lawrence  Smith  alkali 
crucible),  rinse  the  mortar  with  1 
gram  of  calcium  carbonate  and  add 
to  the  contents  of  the  crucible. 
Place  the  covered  crucible  in  a 
slightly  |  inclined  position  with  the 
top  protected  from  the  heat  of  the 
flame.  This  can  be  done  by  setting 
the  crucible  in  a  hole  in  a  cylinder 
of  fire  clay,  as  shown  in  Fig.  56. 
Gradually  heat  the  crucible  over  a 
small  flame  until  no  more  ammonia 
is  evolved,  but  avoid  heating  suffi- 
ciently to  cause  the  evolution  of 
ammonium  chloride.  This  should 
require  about  fifteen  minutes.  Then 
raise  the  temperature  until  finally 
the  lower  three-fourths  (and  no 
more)  of  the  crucible  is  brought  to 
a  red  heat,  and  maintain  this  tem- 
perature for  one  hour.  Allow  the  crucible  to  cool  and  remove  the  sintered  cake 
by  gently  tapping  the  inverted  crucible.  Should  this  not  be  possible,  digest 
the  mass  a  few  minutes  with  water  to  soften  the  cake,  and  then  wash  it  into 
a  large  porcelain  or  platinum  dish.  Heat  the  covered  dish  with  50  to  75  cc. 
of  water  for  half  an  hour,  reduce  the  large  particles  to  a  fine  powder  by  rubbing 

1  Am.  J.  Sci.  (3),  1,  269,  1871;  Hillebrand,  U.  S.  Geol.  Survey  Bull.  422,  171,  1910. 

2  Blank  determinations  should  be  run  on  the  calcium  carbonate,  and  corrections 
made  for  its  alkali  content. 


356     POTASSIUM,   SODIUM   AND   OTHER  ALKALIES 

with  a  pestle  in  the  dish,  and  decant  the  clear  solution  through  a  filter. 
Wash  the  residue  four  times  by  decantation,  transfer  it  to  a  filter,  and  wash 
with  hot  water  until  a  few  cc.  of  the  washings  give  only  a  slight  turbidity  with 
silver  nitrate.  To  make  sure  the  decomposition  of  the  mineral  has  been  com- 
plete, treat  the  residue  with  hydrochloric  acid.  No  trace  of  undecomposed  min- 
eral should  remain  undissolved. 

The  aqueous  extract  obtained  in  the  above  operation  contains  the  chlorides 
of  calcium  and  the  alkalies.  To  remove  the  calcium,  treat  the  solution  with 
ammonia  and  ammonium  carbonate,  heat  to  boiling,  filter  and  wash  the  residue. 
As  this  precipitate  invariably  retains  some  alkali  salts,  it  should  be  dissolved  in 
hydrochloric  acid  and  the  precipitation  repeated.  Evaporate  the  filtrate  to  dry- 
ness  in  a  platinum  or  porcelain  dish,  and  expel  the  ammonium  salts  by  gentle 
ignition  over  a  moving  flame.  After  cooling,  dissolve  the  residue  in  a  little 
water,  and  add  a  few  drops  of  ammonia  and  ammonium  oxalate  to  remove  the 
last  trace  of  calcium.  After  standing  several  hours,  filter  off  the  calcium  oxalate, 
receive  the  filtrate  in  a  weighed  platinum  dish,  evaporate  to  dryness  and  ignite 
gently  to  remove  ammonium  salts.  Moisten  the  cooled  mass  with  hydrochloric 
acid  to  transform  any  carbonate  into  chloride,  and  again  evaporate  to  dryness 
and  ignite.  Cool  in  a  desiccator  and  weigh  the  combined  chlorides.  Dissolve 
in  water,  and  if  an  insoluble  residue  remains,  filter  off,  weigh  and  deduct  from 
the  weight  of  the  chlorides.  Determine  the  potassium  by  one  of  the  methods 
already  described,  and  obtain  the  value  for  sodium  by  difference. 

The  Hydrofluoric  Acid  Method1 

Procedure.  Weigh  about  0.5  gram  of  the  finely  powdered  mineral  into  a  plati- 
num dish,  add  3  or  4  cc.  of  dilute  sulphuric  acid,  and  stir  up  the  mixture  with  a  plati- 
num rod.  After  cooling,  add  about  5  cc.  of  pure  concentrated  hydrofluoric  acid, 
and  evaporate  the  solution  on  the  water  bath,  frequently  stirring  with  the  plati- 
num rod,  until  the  hydrofluoric  acid  is  expelled  and  no  more  hard  particles  can  be 
felt  at  the  bottom  of  the  dish.  Volatilize  the  greater  part  of  the  sulphuric  acid 
by  heating  to  make  sure  of  the  complete  removal  of  the  hydrofluoric  acid,  but  do 
not  remove  all  the  sulphuric  acid  in  order  to  avoid  the  formation  of  insoluble 
basic  salts.  Cover  the  cooled  mass  with  200  cc.  of  water,  and  digest  until  all  the 
residue  has  gone  into  solution.  Precipitate  the  sulphate  by  addition  of  a  slight 
excess  of  barium  chloride  solution,  and  without  filtering  off  the  barium  sul- 
phate, precipitate  the  aluminum,  calcium  and  excess  of  barium  by  treatment  with 
ammonia  and  ammonium  carbonate.  Allow  the  precipitate  to  settle,  filter, 
wash  four  times  by  decantation  and  then  on  the  filter  until  free  from  chlorides. 
Evaporate  the  filtrate  to  dryness,  and  remove  the  ammonium  salts  by  gentle 
ignition.  Dissolve  the  residue  in  a  little  water,  and  separate  the  magnesium 
according  to  one  of  the  methods  described  above.  Finally  weigh  the  alkalies  as 
chlorides  or  sulphates.  Determine  the  potassium  in  the  residue  and  obtain  the 
value  for  sodium  by  difference. 

Determination  of  the  Alkalies  in  Alunite 

Thoroughly  mix  the  finely  powdered  mineral  with  an  equal  weight  of  pure 
silica,  and  proceed  as  directed  under  the  J.  Lawrence  Smith  method  for  the 

1  Treadwell,  op.  cit.,  p.  499. 


POTASSIUM,   SODIUM   AND   OTHER  ALKALIES      357 

determination  of  the  alkalies  in  silicates.  In  this  case,  however,  the  water  extract 
will  contain  a  large  amount  of  sulphate,  which  should  be  removed  by  precipita- 
tion with  barium  chloride  solution  before  undertaking  to  separate  the  calcium. 

For  an  approximate  determination,  ignite  a  half  gram  of  the  powdered  mineral 
for  an  hour  or  so  at  low  red  heat,  cool,  leach  out  with  water,  evaporate  to  dryness, 
and  weigh  the  residual  sulphates.  If  sodium  is  present,  determine  the  potassium 
in  the  residue. 

Determination  of  the  Alkalies  Volumetrically 

Titration  with  Standard  Acid 

When  sodium  or  potassium  is  present  as  a  hydroxide  or  salt  of  a  weak  acid 
such  as  carbonate  or  borate,  either  metal  when  present  alone  may  usually  be  de- 
termined by  titration  with  standard  acid  and  methyl  orange. 

Titration  with  Standard  Silver  Nitrate 

The  alkalies  may  be  determined  when  present  alone  as  chloride  by  titration 
with  standard  silver  nitrate,  potassium  chromate  indicator. 


SELENIUM  AND  TELLURIUM 

WILFRED  W.  SCOTT 

{  amorphous  4.26;  m.p.  217°;)  , 
Se8,  at.wt.  79.3;  sp.gr.  }  ^^  ^  \  b.p.  690°  C.;   ox.de 

SeO2;  acids,  H2SeO3,  H2SeO4. 

Te,  at.  wt.  137.5;  sp.gr.  6.27;  m.p. 452°; l   b.p.  139O°C.;  ojcidesTeO,TeO2, 
TeO3;  acids,  H2TeO3,  H2TeO4. 

DETECTION 

Selenium  and  tellurium  appear  with  the  hydrogen  sulphide  subgroup  ele- 
ments in  the  ordinary  course  of  qualitative  analysis.  The  acid  solution  of  the 
material  is  treated  cold  with  H2S,  as  the  lemon-yellow  SeS,  formed  in  a  cold  solu- 
tion is  more  readily  soluble  in  alkaline  sulphide  solutions  than  the  orange-yellow 
SeS2  precipitated  from  hot  solutions.  Although  only  a  partial  separation  takes 
place  the  extract  will  contain  sufficient  selenium,  if  present  in  the  sample,  to  give  a 
qualitative  test.  By  precipitation  from  an  acid  solution  by  H2S,  selenium  and 
tellurium  are  separated  from  members  of  subsequent  groups.  The  sulphides  pre- 
cipitated are  extracted  with  sodium  or  ammonium  sulphide  and  the  extract  exam- 
ined for  selenium  and  tellurium. 

Detection  of  Selenium 

The  sodium  or  ammonium  extract  is  acidified  with  hydrochloric  acid,  whereby 
selenium  together  with  the  other  members  of  the  group  are  precipitated.  The 
washed  dried  precipitate  is  mixed  with  twice  its  weight  of  a  flux  containing  equal 
parts  of  sodium  carbonate  and  nitrate,  and  the  mixture  added  to  an  equal  amount 
of  the  flux  which  has  been  previously  fused.  The  fluid  mass  is  poured  on  to  a 
slab  of  porcelain  and  the  cooled  melt  placed  in  a  beaker  and  extracted  with 
water,  whereby  selenic,  telluric,  molybdic  and  arsenic  acids  dissolve,  stannic  oxide, 
sodium  antimonate,  gold  and  the  platinum  group  remaining  insoluble.  The 
extract  is  treated  with  an  excess  of  hydrochloric  acid  and  boiled  to  reduce  sodium 
selenate,  Na2Se04,  to  selenious  acid,  H2Se03.  A  reducing  agent  such  as  sulphur- 
ous acid,  ammonium  sulphite,  hydrazine  sulphate  or  hydroxylamine  is  added 
and  the  solution  boiled.  Selenium,  if  present,  is  precipitated  in  its  red  or  brown 
colored  metallic  form.  The  red  color  darkens  on  boiling. 

Selenium  is  an  odorless  and  tasteless  solid.  Its  vapor  has  a  putrid  horseradish 
odor.  The  element  burns  with  a  reddish-blue  colored  flame. 

Dissolved  in  concentrated  sulphuric  acid  a  fine  green-colored  solution  is  ob- 
tained, from  which  solution  selenium  may  be  precipitated  by  dilution  with  water, 
the  suspended  substance  giving  a  reddish  tint  to  the  acid. 

1  Circular  35  (2d  Ed.),  U.  S.  Bureau  of  Standards. 
358 


SELENIUM  AND  TELLURIUM  359 

Hydrochloric  acid  decomposes  selenates  with  evolution  of  chlorine  gas  on 
boiling. 

Barium  chloride  precipitates  white  BaSe03,  soluble  in  dilute  HC1,  when  added 
to  selenites,  and  white  BaSe04,  insoluble  in  dilute  HC1,  when  added  to  selenates. 

Hydrogen  sulphide  produces  no  precipitate  with  a  selenate.  This  reduced, 
however,  by  heating  with  HC1,  a  lemon-yellow  to  orange-yellow  precipitate  of 
SeS2  is  obtained. 

The  gas  passed  into  a  solution  of  selenite  gives  an  immediate  precipitation  of 
the  sulphide,  SeS2. 

Detection  of  Tellurium 

Tellurium  dissolved  in  concentrated  sulphuric  acid  colors  the  acid  purple  or 
carmine.  The  color  disappears  on  dilution.  The  mineral  may  be  treated 
directly  with  hot  concentrated  sulphuric  acid  and  the  color  obtained  in  presence 
of  tellurium. 

Heated  in  a  test-tube  tellurium  compounds  sublime  and  fuse  to  colorless, 
transparent  drops  of  Te02. 

Hydrogen  sulphide  precipitates  metallic  tellurium  mixed  with  sulphur  when 
passed  into  acid  solutions  containing  the  element.  The  precipitate  resembles 
SnS  in  appearance.  It  is  readily  soluble  in  (NH^S. 

Tellurium  burns  with  a  greenish  flame. 

Reducing  agents  added  to  acid  solutions  of  tellurium  precipitate  black 
metallic  tellurium. 

Tellurium  compounds  are  not  as  readily  reduced  as  are  those  of  selenium. 
In  solutions  having  an  acidity  of  over  80  per  cent,  S02  gas  causes  the  precipita- 
tion of  metallic  selenium  alone.  Upon  dilution  with  an  equal  volume  of  water 
tellurium  is  precipitated.  A  separation  may  be  effected  in  this  way. 

Tellurates  boiled  with  HCl  evolve  chlorine  gas  and  are  reduced  to  H2Te03. 
Dilution  of  the  solution  will  cause  the  precipitation  of  Te02  (distinction  from  Se) . 

Potassium  iodide  added  to  a  tellurite  in  dilute  sulphuric  acid  solution  (1  :  4) 
precipitates  black  TeI4,  soluble  in  excess  of  KI. 


ESTIMATION 

Selenium  and  tellurium  closely  resemble  sulphur  in  chemical  properties. 
They  have  crystalline  and  amorphous  forms.  The  elements  occur  in  nature 
frequently  associated  with  sulphur.  Selenium  is  frequently  present  in  iron 
pyrites,  hence  is  found  in  the  flue  dust  of  lead  chambers  of  the  sulphuric  acid  plant, 
and  as  an  impurity  in  sulphuric  acid,  prepared  from  pyrites  containing  selenium. 

Ores — Selenium.  In  copper  and  iron  pyrites;  meteoric  iron.  In  the  rare 
minerals  clausthalite,  PbSe;  lehrbachite,  PbSe-HgSe;  onofrith,  HgSe*4HgS; 
eucairite,CuSe-Ag2Se;  crookesite,  (CuTlAg)Se.1 

Tellurium.  Occurs  in  tellurides  and  arsenical  iron  pyrites.  Frequently 
associated  with  gold,  silver,  lead,  bismuth  and  iron.  In  the  minerals — altaite, 
PbTe;  calaverite,  AuTe2;  coloradolite,  HgTe;  nagyagite,  (AuPb)2(TeSSb)3; 
petzite,  AgsAuTe2;  sylvanite,  AuAgTe4;  telluride,  Te02  (tellurium  ochre); 
tetradymitejBi/Tea.1 

1  Thorpe,  "  Dictionary  of  Applied  Chemistry." 


360  SELENIUM  AND   TELLURIUM 


Preparation  and  Solution  of  the  Sample 

The  following  facts  regarding  solubilities  of  these  elements  and  their  com- 
pounds may  be  useful  in  the  analysis  of  these  substances. 

Selenium.  Amorphous  selenium  is  soluble  in  carbon  disulphide;  the  crys- 
taUine  hexagonal  form  is  insoluble  in  this  reagent.  The  metal  is  soluble  in 
hydrochloric  acid  in  the  presence  of  nitric  acid.  It  is  soluble  in  cold  concen- 
trated sulphuric  acid,  giving  a  green-colored  liquid,  which  diluted  with  water 
deposits  selenium.  The  dioxide,  Se02,  is  readily  soluble  in  hot  water. 

Tellurium.  The  element  dissolves  in  hot  concentrated  hydrochloric  acid. 
On  dilution  of  the  solution  a  precipitation  of  H2Te03-Te02  occurs.  Treated 
with  concentrated  nitric  acid  or  aqua  regia  H2Te04  forms.  With  sulphuric  acid 
the  compound  H2Te03  forms  and  S02  is  evolved.  The  element  dissolves  in 
concentrated  potassium  cyanide,  from  which  solution  hydrochloric  acid  precip- 
itates all  of  the  tellurium.  Tellurium  is  insoluble  in  carbon  disulphide.  The 
oxides  TeO  and  Te02  are  soluble  in  acids,  Te03  being  not  readily  soluble.  All 
the  oxides  dissolve  in  hot  potassium  hydroxide  solutions. 

Care  must  be  exercised  to  avoid  overheating  acid  extracts  in  the  preparation  of  the 
sample,  since  loss  by  volatilization  is  apt  to  occur;  this  is  especially  true  of  the  halogen 
compounds  of  selenium  and  tellurium,  the  former  being  more  volatile  than  the  latter. 
(B.p.  SeCl2  =  145°;  Se2Br2=225°-230°:  SeOCl2  =  179.5°;  TeCl2=327°;  TeCl4=414°; 
TeBr2  =  339°;  TeBr4  =  420°  C.)1 

Fusion  Method.  The  finely  powdered  substance  is  intimately  mixed  with 
about  five  tunes  its  weight  of  a  flux  of  sodium  carbonate  and  nitrate  (4:1)  and 
heated  gently  in  a  nickel  crucible,  gradually  increasing  the  heat,  until  the  charge 
has  fused.  When  the  molten  mass  appears  homogeneous,  it  is  cooled  and  ex- 
tracted with  water.  Sodium  selenate  and  tellurate  pass  into  solution  and  are 
separated  from  most  of  the  heavy  metals.  The  water  extract  is  acidified  with 
hydrochloric  acid  and  boiled  until  no  more  free  chlorine  is  evolved.  (Test 
with  starch  iodide  paper.  Cl=blue  color.)2  Metallic  selenium  and  tellurium 
may  be  precipitated  by  passing  sulphur  dioxide  into  the  hydrochloric  acid  solution. 

Keller  has  shown  that  tellurium  is  not  precipitated  by  S02  in  strong  hydro- 
chloric acid  solutions  (sp.gr.  1.175),  whereas  selenium  is  precipitated.  Diluted 
with  an  equal  volume  of  water  (acidity  30  to  50%  of  above)  both  tellurium  and 
selenium  are  precipitated  by  S02. 

SEPARATIONS 

One  or  more  of  the  following  procedures  may  be  required  according  to  the 
material  that  is  being  analyzed. 

Separation  of  Selenium  and  Tellurium  from  the  Iron  and  Zinc  Groups, 
from  the  Alkaline  Earths  and  the  Alkalies.  If  sulphur  dioxide  is  passed  into 
a  solution  containing  30  to  50%  of  hydrochloric  acid  (sp.gr.  1.175),  selenium  and 
tellurium  will  be  precipitated,  the  other  elements  remaining  in"  solution.  If  the 
acidity  is  over  80%  of  the  above  strength  of  hydrochloric  acid,  only  selenium 
is  precipitated. 

1  Van  Nostrand's  Chem.  Annual. 

2  According  to  B.  Rathke,  Zeit.  anal.  Chem.,  9,  484,  1870;  no  appreciable  loss  of 
selenium  occurs  in  the  presence  of  sodium  or  potassium  chlorides.     Rose  claims  that 
an  appreciable  loss  occurs  when  solutions  of  selenium  are  heated  above  100°  C. 


SELENIUM  AND  TELLURIUM  361 

The  presence  of  nitric  and  of  sulphuric  acid  prevents  the  copmlete  precipita- 
tion of  tellurium. 

Separation  of  Selenium  and  Tellurium  from  Cadmium,  Copper  and  Bis- 
muth. Sulphur  dioxide  passed  into  an  acid  solution  containing  30  to  50% 
hydrochloric  acid  (sp.gr.  1.175)  precipitates  selenium  and  tellurium  free  from 
cadmium,  and  the  greater  part  of  bismuth,  copper,  antimony,  etc.  Complete 
separation  of  selenium  and  tellurium  may  be  effected  by  the  distillation  process 
described  under  Separation  of  Selenium  and  Tellurium,  see  below. 

Separation  from  Silver.  Silver  is  precipitated  as  the  chloride,  AgCl,  se- 
lenium and  tellurium  remaining  in  solution. 

Separation  from  Gold.  The  slightly  acid  solution,  free  from  nitric  acid, 
is  diluted  with  water,  ammonium  oxalate  or  oxalic  acid  added  and  the  precipitated 
gold  allowed  to  settle  several  hours  (preferably  twenty-four  hours  or  more).  The 
gold  is  filtered  off  and  the  selenium  and  tellurium  precipitated  in  the  filtrate  with 
sulphur  dioxide. 

In  the  absence  of  selenium,  gold  may  be  separated  from  tellurium  by  precipi- 
tation with  ferrous  sulphate  added  to  the  solution  strongly  acidified  with  hydro- 
chloric acid.  Tellurium  remains  in  solution.  (Selenium  is  also  precipitated 
with  ferrous  sulphate.) 

Separation  of  Selenium  from  Tellurium  in  Strong  Hydrochloric  Acid  by  Di- 
rect Precipitation  with  Sulphur  Dioxide — Keller's  Method.1  The  procedure  has 
already  been  mentioned.  Advantage  is  taken  of  the  fact  that  tellurium  is  not  precipi- 
tated by  SO2  in  strong  hydrochloric  acid  solutions,  whereas  selenium  is  precipitated. 

Procedure.  The  two  elements  are  precipitated  by  sulphur  dioxide  from  an 
acid  solution  containing  30  to  40%  of  strong  hydrochloric  acid.  The  precipitate 
is  dissolved  in  nitric  acid  and  the  solution  evaporated  to  dryness  on  the  steam 
plate.  The  residue  is  treated  with  200  cc.  of  hydrochloric  acid  (sp.gr.  1.175) 
and  boiled  to  free  the  solution  of  nitric  acid,  since  the  presence  of  this  acid  pre- 
vents complete  precipitation  of  tellurium.  A  little  sodium  chloride  is  previously 
added  to  minimize  the  loss  through  volatilization  during  the  heating.  The  hot 
solution  is  saturated  with  sulphur  dioxide,  whereupon  selenium  is  quantitatively 
precipitated  and  may  be  filtered  off,  washed  with  a  90%  solution  of  strong  hydro- 
chloric acid  (sp.gr.  1.175,  i.e.,  9  parts  HC1  to  1  part  by  volume  H20),  followed  by 
dilute  acid,  then  by  water  until  free  of  acid,  and  finally  by  alcohol.  Weigh  as 
metallic  selenium  after  drying  at  105°  C.  The  tellurium  is  precipitated  from  the 
filtrate  by  diluting  this  with  an  equal  volume  of  water,  heating  to  boiling  and 
again  saturating  with  sulphur  dioxide.  The  precipitate  is  washed  with  dilute 
hydrochloric  acid  (1  :  1),  followed  by  water  and  alcohol,  then  dried  and  weighed 
as  tellurium. 

Separation  of  Selenium  and  Tellurium.     Distillation  Method 

The  following  method  is  excellent  for  determining  selenium  and  tellurium  in 
alloys. 

Procedure.  The  apparatus  having  been  set  up  as  is  shown  in  the  cut,  Fig.  57, 
0.5  gram  of  the  alloy  containing  selenium  and  tellurium  is  placed  in  the  distilling 
flask  D  and  30  cc.  of  H2S04  (sp.gr.  1.84)  added.  All  connections  are  made  tight. 

A  current  of  dry  HC1  gas  is  allowed  to  flow  into  the  distilling  flask  and  the 
contents  of  the  flask  heated  to  300°  C.  (The  H2S04  should  not  fume  and  the 
temperature  should  be  kept  below  the  boiling  point  of  this  acid,  otherwise  the 
1  Jour.  Am.  Chem.  Soc.,  19,  771. 


362 


SELENIUM   AND    TELLURIUM 


acid  distilling  into  the  reservoir  R  would  interfere  with  the  precipitation  of 
selenium  by  S02.)  Selenium  distills  as  selenium  chloride  into  R,  while  tellurium 
remains  in  the  distillation  flask.  During  the  distillation,  S02  gas  is  passed  into 
R,  to  reduce  the  selenic  salt  in  solution  and  precipitate  metallic  selenium. 

The  distillation  is  continued  for  two  or  three  hours,  keeping  the  temperature 
of  the  distillation  flask  at  about  300°  C.  (i.e.,  below  the  boiling-point  of  H2S04). 
The  contents  of  the  receiver  R  is  transferred  to  a  400-cc.  beaker,  and  the  dis- 
tillation continued  into  fresh  HC1  to  assure  complete  volatilization  of  selenium 
from  the  flask  D.  The  contents  of  the  receiver  and  any  of  the  metal  adhering 
to  the  glass  wool,  or  the  glass  of  the  vessel,  are  combined.  (The  adhering  selenium 
is  dissolved  off  with  a  little  Bromine-Potassium  Bromide  solution.) 


Thee-Ytay 
Stopcock 


To  Hood 


Concentrated 
Hydrochloric 
*  Acid 


Mercury  Pressure 

Gauge 
Blows  out 'into  V        <£ 
with  3Lb.  Pressure   j 

HCl. 
Gen 


Distillation  Flash 
containing  Se  and 
Te  Samoie 


5  Concentrated 
Sulphuric  Acid 


FIG.  57. — Apparatus  for  Determining  Selenium  and  Tellurium. 

Fig.  57  shows  a  convenient  apparatus  for  routine  determinations  of  selenium 
and  tellurium  in  alloys.  Hydrochloric  acid  gas  is  generated  by  allowing  strong 
hydrochloric  acid  to  flow  into  concentrated  sulphuric  acid  (see  A  and  B  in  draw- 
ing Fig.  57).  The  gas  is  dried  by  passing  it  through  strong  sulphuric  acid  (C  in 
figure).  A  mercury  pressure  gauge,  arranged  to  allow  gas  to  blow  out  at  a  pressure  of 
3  or  4  pounds,  prevents  accident  occurring  due  to  stoppage  in  the  system. 


Determination  of  Selenium.  The  solution  in  the  beaker  is  saturated  with  S02, 
then  heated  to  boiling  and  the  precipitated  selenium  allowed  to  settle  several 
hours,  or  overnight.  The  precipitate  is  filtered  into  a  weighed  Gooch  crucible, 
then  washed  with  hot  water  and  finally  with  alcohol.  The  residue  is  dried  for  an 
hour  at  100°  C.  and  weighed. 


Weight  of  Se  XI 00 
0.5 


%Se. 


SELENIUM  AND   TELLURIUM  363 

Determination  of  Tellurium.  The  residue  in  the  distilling  flask  is  transferred 
fco  a  600-cc.  beaker  containing  150  cc.  of  cold  water.  Ten  cc.  of  3%  Fe(N03)3  solu- 
tion is  added,  and  made  ammoniacal,  and  then  heated  to  boiling;  the  precipitate 
filtered  off  on  a  large  filter  and  washed  with  hot  water.  The  precipitate  is  dis- 
solved in  hot  dilute  HC1  and  the  solution  nearly  neutralized  with  NH4OH.  The 
slightly  acid  solution  is  saturated  with  H2S,  the  precipitated  tellurium  filtered  off 
on  an  S.  and  S.  No.  589,  12|  cm.  filter,  and  washed  with  H2S  water. 

The  precipitate  is  dissolved  off  the  paper  into  a  small  beaker  with  a  mixture 
of  equal  parts  of  HC1  and  bromine-potassium  bromide  solution.1  The  paper  is 
washed  with  water  keeping  the  volume  of  the  solution  as  small  as  possible.  The 
filtrate  should  contain  20%  HC1. 

Tellurium  is  precipitated  by  saturating  the  solution  with  S02.  The  pre- 
cipitate, after  heating  to  boiling,  is  allowed  to  settle  for  several  hours  and  filtered 
onto  a  weighed  Gooch.  It  is  washed  with  hot  water  and  then  with  alcohol  and 
dried  for  an  hour  at  100°  C.,  cooled  in  a  desiccator  and  weighed. 

Weight  of  TeX  100 


GRAVIMETRIC    METHODS    FOR    DETERMINING    SELENIUM 

AND  TELLURIUM 

The  sections  on  Preparation  and  Solution  of  the  Sample  and  Separations 
should  be  carefully  studied,  as  details  for  the  precipitation  of  selenium  and 
tellurium  are  given. 

SELENIUM 
Precipitation  of  Selenium  by  Sulphur  Dioxide 

The  procedure  for  isolation  of  selenium  by  precipitation  with  sulphur  dioxide 
gas,  passed  into  the  hydrochloric  acid  solution,  has  been  given  already  in  detail. 
For  matter  of  convenience  the  procedure  is  briefly  outlined  here. 

Procedure.  The  sample  obtained  in  solution  according  to  the  procedure  out- 
lined under  Preparation  and  Solution  of  the  Sample  and  freed  from  nitric  acid, 
is  saturated  with  sulphur  dioxide,  whereupon  selenium  is  precipitated  in  its 
elemental  condition.  If  the  solution  is  strongly  acid  with  hydrochloric  acid 
(HCl=sp.gr.  1.175),  tellurium  remains  in  solution,  if  present.  It  is  advisable 
to  wash  the  precipitated  selenium  with  moderately  strong  hydrochloric  acid, 
followed  by  the  dilute  acid,  then  with  water  until  free  of  acid,  and  finally  with 
alcohol.  The  residue  is  dried  at  105°  C.  and  weighed  as  metallic  selenium. 

The  filtrate  should  be  tested  for  selenium  by  saturating  again  with  S02. 
Tellurium  precipitates  quantitatively  from  hydrochloric  acid  solution  of  half  the 
above  strength,  hence  will  be  evident  in  the  filtrate,  if  present. 

irThe  potassium  bromide  solution  is  made  by  adding  200  cc.  of  liquid  bromine  to 
320  grams  of  potassium  bromide  salt  dissolved  in  just  sufficient  water  to  form  a  satu- 
rated solution. 


364  SELENIUM   AND   TELLURIUM 


Reduction  to  Metallic  Selenium  Potassium  Iodide  Method 

The  method  worked  out  by  Peirce  x  is  useful  in  determining  selenium  in  sam- 
ples containing  less  than  0.1  gram  selenium.  Larger  amounts  are  apt  to  occlude 
iodine,  giving  high  results. 

Procedure.  The  sample  containing  selenious  acid  or  a  selenite  is  diluted  to 
400  cc.  and  acidified  with  hydrochloric  acid.  Potassium  iodide  is  added  in  excess, 
about  3  grams  more  than  is  required  to  effect  reduction,  and  the  solution  boiled 
about  twenty  minutes.  The  precipitate  is  filtered  and  washed  as  usual,  then 
dried  and  weighed  as  metallic  selenium. 


TELLURIUM 
Precipitation  of  Tellurium  by  Sulphur  Dioxide 

The  procedure  has  been  given  under  the  section  on  Separations.  The  fol- 
lowing method  is  useful  for  determining  tellurium  in  samples  in  which  selenium 
estimations  are  not  desired. 

Procedure.  A  sample  of  1  to  5  gramsis  taken  for  analysis  and  placed  in  a 
No.  5  porcelain  crucible.  Ten  cc.  of  cone.  HN03  are  added  very  cautiously  and, 
when  the  apparent  action  has  ceased,  the  sample  is  placed  on  the  steam  bath  until 
all  N02  fumes  have  been  expelled.  Four  to  5  drops  of  cone.  H2S04  are  now  added 
and  the  solution  evaporated  to  dryness  on  the  steam  bath.  About  15  cc.  of  cone. 
HC1  are  added  and  the  solution  again  evaporated  to  dryness.  By  this  latter  pro- 
cedure any  selenium  that  may  be  present  is  converted  to  the  easily  volatile 
chloride.  The  crucible  is  placed  on  a  triangle  on  a  wire  gauze  over  a  low  flame 
and  heated  cautiously 2  until  all  white  fumes  have  disappeared  and  then  at  dull 
red  heat  until  all  signs  of  crystallized  selenious  chloride  have  disappeared.  The 
residue  in  the  crucible  is  tellurious  dioxide  and  ferric  oxide. 

The  crucible  is  cooled  and  the  residue  dissolved  in  cone.  HC1  in  a  No.  4  beaker 
and  the  solution  diluted  to  250  cc.  with  distilled  water.  H2S  is  passed  into  the 
solution  until  tellurium  is  completely  precipitated.  The  precipitate  is  filtered 
onto  a  Vl\  cm.  filter,  S.  &  S.  589  quality,  and  washed  with  H2S  water. 

The  precipitate  is  dissolved  in  a  250-cc.  beaker  by  adding  a  mixture  of  bro- 
mine-potassium bromide  (200  cc.  of  liquid  bromine  added  to  320  grams  of  KBr 
salt  that  has  been  dissolved  in  just  sufficient  water  to  form  a  saturated  solution), 
1  part  and  cone.  HC1,  1  part,  using  the  least  amount  of  the  mixture  necessary  to 
dissolve  the  precipitate  and  wash  with  a  little  water.  The  filtrate  should  con- 
tain 20%  HC1. 

The  solution  is  thoroughly  saturated  with  S02  gas,  and  then  heated  to  boiling. 
The  precipitated  tellurium  is  allowed  to  settle  for  several  hours,  preferably  over 
night,  and  filtered  into  a  weighed  Gooch  crucible,  then  washed  with  hot  water 
and  finally  with  alcohol.  After  drying  for  an  hour  at  100°  C.,  the  tellurium  is 
cooled  and  weighed. 

Weight  of  the  residue  multiplied  by  100  divided  by  weight  taken  gives  per 
cent  telurium. 

1  A.  W.  Peirce,  Am.  Jour.  Sci.  (4),  1416.     Gooch,  "  Methods  of  Chemical  Analysis," 
376. 

2  Cautious  heating  is  necessary  to  prevent  mechanical  loss  of  tellurium  during  the 
volatilization  of  selenium. 


SELENIUM  AND   TELLURIUM  365 


Determination  as  Tellurium  Dioxide 

The  following  procedure  worked  out  by  Browning  and  Flint *  provides  for  the  di- 
rect estimation  of  tellurium  in  the  form  of  its  dioxide,  Te02,  in  presence  of  selenium. 
The  oxide  is  not  affected  by  the, air,  it  is  anhydrous,  non-hydroscopic  and  may  be 
obtained  in  pure  form.  Selenium  and  tellurium  are  precipitated  by  sulphur 
dioxide  from  a  hydrochloric  acid  solution  according  to  the  procedures  given. 
The  elements  are  filtered  off,  dissolved  in  hydrochloric  acid  containing  sufficient 
nitric  acid  to  cause  solution  and  carefully  taken  to  dryness  on  the  water  bath. 
The  mixture  is  then  treated  as  follows: 

Procedure.  The  material  is  dissolved  in  hydrochloric  acid,  or  in  a  10% 
solution  of  potassium  hydroxide,  using  about  2  cc.  per  0.2  gram  of  dioxide.  The 
solution,  if  alkaline,  is  slightly  acidified  with  hydrochloric  acid  and  then  diluted 
to  200  cc.  with  boiling  water.  Dilute  ammonium  hydroxide  is  now  added  in  faint 
excess,  followed  by  the  faintest  possible  excess  of  acetic  acid,  whereby  the 
finely  crystalline  tellurium  dioxide  is  precipitated.  The  precipitate  is  transferred 
to  the  perforated  crucible  containing  an  asbestos  mat,  and  washed  rapidly  with 
cold  water,  then  dried  to  constant  weight  at  105°  C.  and  weighed  as  Te02. 

NOTES.  The  addition  of  a  few  drops  of  acetic  acid,  as  recommended,  causes  the 
precipitation  to  become  quantitative  when  the  solution  has  cooled. 

Hot  water  is  used  for  the  dilution,  since  cold  water  induces  a  flocky  precipitation 
with  inclusion  of  selenious  acid. 


VOLUMETRIC  DETERMINATION  OF  SELENIUM  AND 

TELLURIUM 

lodometric  Determination  of  Selenic,  or  Telluric  Acid  —  Reduction 
with  Hydrochloric  Acid  and  Distillation 

The  method  depends  upon  the  reduction  of  selenic  or  telluric  acid  to  selenious 
or  tellurious  acid  by  heating  with  hydrochloric  acid,  the  evolved  chlorine  being 
a  measure  of  the  acids  in  question.  The  chlorine  absorbed  in  potassium  iodide 
solution  liberates  its  equivalent  of  iodine,  which  may  readily  be  determined  by 
titration  with  standard  thiosulphate.  The  following  reactions  illustrate  the 
change  that  takes  place  : 

K2Se04+4HCl=2KCl+H2Se03+H20+Cl*, 
K2Te04+4HCl=2KCl+H2Te03+H20+Cl2, 

1  Cl.  =1  I  =—  or  —  =63.75  grams  Te  or  39.6  grams  Se  per  liter  normal  solution. 

~i         2i 

According  to  Gooch  and  Evans  2  over  30%  of  strong  hydrochloric  acid  (sp.gr. 
1.20)  should  be  present.  Dilute  hydrochloric  acid  having  a  strength  of  10%  of 
HC1,  sp.gr.  1.2,  does  not  react  with  liberation  of  chlorine.  Care  must  be  taken 
not  to  prolong  the  boiling  after  the  solution  reaches  a  concentration  of  half 
strength,  since  over  reduction  may  take  place  and  the  metals  be  liberated. 

1  Philip  E.  Browning  and  Wm.  R.  Flint,  Am.  Jour.  Sci.  (4),  28X  112.      F.  A.  Gooch, 
"  Methods  in  Chemical  Analysis,"  John  Wiley  &  Sons,  Pub. 

2  F.  A.  Gooch  and  P.  S.  Evans,  Jr.,  Am.  Jour.  Sci.,  (3),  1,  400. 


366  SELENIUM  AND   TELLURIUM 

Procedure.  The  sample  containing  the  selenate  or  tellurate  is  treated  with 
75  cc.  of  hydrochloric  acid,  containing  25  cc.  of  strong  HC1,  sp.gr.  1.20,  per  0.2 
gram  of  the  oxides,  in  a  distillation  flask  connected  with  a  Drexel  wash  bottle 
receiver,  water  cooled,  and  charged  with  potassium  iodide  solution.  A  current 
of  CO2  is  passed  into  the  flask  to  sweep  the  liberated  chlorine  into  the  iodide 
solution.  The  sample  is  boiled  until  nearly  one-third  its  volume  has  distilled 
into  the  receiver.  The  liberated  iodine  is  titrated  with  standard  thiosulphate. 
One  cc.  N/10  Na2S203  =0.00396  gram  Se  or  0.006375  gram  Te. 


SILICON 

WILFRED  W.  SCOTT 
Si,  at.  wt.  28.3 ;  sp.gr.  amor.  3.00. ;  crys.  2.49 ;  m.p.  1420°  C. ;  oxides  SiO,1  SiO2 

DETECTION 

The  finely  ground  sample  together  with  a  small  quantity  of  powdered  calcium 
fluoride  is  placed  in  a  small  lead  cup  1  cm.  in  diameter  and  depth  (see  Fig. 
58),  and  a  few  drops  of  concentrated  sulphuric  acid  added.  A  lead  cover,  with 

a  small  aperture,  is  placed   on   the  cup,  and  the   opening _. 

covered    with   a    piece    of    moistened   black   filter    paper.     ^- 

Upon  this  paper  is   placed  a  moistened  pad  of  ordinary 

filter  paper.    The  cup  is  now  gently  heated  on  the  steam 

bath.    At  the  end  of  about  ten  minutes  a  white  deposit 

will  be  found  on  the  under  side  of  the  black  paper,  at  the 

opening  in  the  cover,  if  an  appreciable  amount  of  silica  is  j^    53 

present  in  the  material  tested.2 

A  silicate,  fused  with  sodium  carbonate  or  bicarbonate  in  a  platinum  dish 
and  the  carbonate  decomposed  by  addition  of  hydrochloric  acid  with  subsequent 
evaporation  to  dryness,  will  liberate  silicon  as  silicic  anhydride,  Si02.  The 
silica  placed  in  a  platinum  dish  is  volatilized  by  addition  of  hydrofluoric  acid, 
the  gaseous  silicon  fluoride  being  formed.  A  drop  of  water  placed  in  a  platinum 
loop,  held  in  the  fumes  of  SiF4,  will  become  cloudy  owing  to  the  formation  of 
gelatinous  silicic  acid  and  fluosilicic  acid, 

3SiF4+3H20  =H2Si03+2H2SiF6. 

If  a  silicate  is  fused  in  a  platinum  loop  with  microcosmic  salt,  the  silica  floats 
around  in  the  bead,  producing  an  opaque  bead  with  weblike  structure  upon  cooling. 

ESTIMATION 

The  gravimetric  procedure  is  the  only  satisfactory  method  for  the  estimation 
of  silica.  The  substance  in  which  the  element  is  combined  as  an  oxide  or  as  a 
silicate  is  decomposed  by  acid  treatment  or  by  fusion  with  an  alkali  carbonate 
or  bicarbonate,  the  material  taken  to  dryness  with  addition  of  hydrochloric  acid, 
whereby  the  compound  silica  is  liberated.  If  other  elements  are  present  the 
silica  is  volatilized  by  addition  of  hydrofluoric  acid  and  estimated  by  the  loss 
of  weight  of  the  residue. 

The  element  silicon  has  no  important  application.  Its  use  for  electrical 
resistance  has  been  suggested.  A  rod  10  cm.  long  with  cross  section  of  40  sq.mm. 
has  a  resistance  of  200  ohms  against  a  carbon  rod  of  the  same  dimensions  of  0.15 

1  Dictionary  of  Applied  Chemistry.    Thorpe,  page  671. 

2  Philip  E.  Browning,  Am.  Jour.  Sci.  (4),  32,  249. 

367 


368  SILICON 

ohm.  Impure  silica  finds  use  in  fluxes  in  manufacture  of  glass;  pure  silica  for 
the  manufacture  of  silica  ware.  With  caustic  it  forms  an  adherent  sodium 
silicate.  Silicon  carbide,  carborundum,  is  used  for  refractory  purposes,  fire 
brick,  zinc  muffles,  coke  ovens.  Crystolon,  the  crystalline  form,  is  used  as  an 
abrasive,  in  making  grinding  wheels,  sharpening  stones,  etc. 

Combined  as  Si02  and  in  silicates  the  element  is  very  widely  distributed  in 
nature  and  is  a  required  constituent  in  practically  every  complete  analysis  of 
ores,  minerals,  soils,  etc.  It  is  present  in  certain  alloys,  ferro-silicon,  silicon 
carbide,  etc. 

The  element  is  scarcely  attacked  by  single  acids,  but  is  acted  upon  by  nitric- 
hydrofluoric  acid  mixture.  It  dissolves  in  strong  alkali  solutions.  Silica  is 
decomposed  by  hydrofluoric  acid  and  by  fusion  with  the  fixed  alkali  carbonates 
or  hydroxides. 

Preparation  and  Solution  of  the  Sample 

General  Considerations.  The  natural  and  artificially  prepared  silicates  may 
be  grouped  under  two  classes:  1.  Those  which  are  decomposed  by  acids.  2. 
Silicates  not  decomposed  by  acids.  The  minerals  datolite,  natrolite,  olivine 
and  many  basic  slags  are  representative  of  the  first  class,  and  feldspar,  ortho- 
clase,  pumice  and  serpentine  are  representative  of  silicates  not  decomposed  by 
acids.  (See  more  complete  list  under  List  of  More  Important  Silicates,  page  369.) 
The  first  division  simply  require  an  acid  treatment  to  isolate  the  silica,  the  latter 
class  require  fusion  with  a  suitable  flux. 

In  technical  analysis,  in  cases  where  great  accuracy  is  not  required,  the  residue 
remaining,  after  certain  conventional  treatments  with  acids,  is  classed  as  silica. 
This  may  consist  of  fairly  pure  silica  or  a  mixture  of  silica,  undecomposed  sili- 
cates, barium  sulphate  and  certain  acid  insoluble  compounds.  For  accurate 
analyses  this  insoluble  residue  is  not  accepted  as  pure  silica,  unless  impurities, 
which  are  apt  to  be  found  with  the  silica  residue,  are  known  to  be  absent  from  the 
material  under  examination. 

Although  the  procedure  for  isolation  of  silica  is  comparatively  simple,  errors 
may  arise  from  the  following  causes: 

1.  Imperfect  decomposition  of  the  silicate. 

2.  Loss  of  the  silica  by  spurting  when  acid  is  added  to  the  carbonate  fusion. 

3.  Slight  solubility  of  silica,  even  after  dehydration,  especially  in  presence 
of  sodium  chloride  and  magnesia. 

4.  Loss  due  to  imperfect  transfer  of  the  residue  to  the  filter  paper. 

5.  Mechanical  loss  during  ignition  of  the  filter  and  during  the  blasting,  due 
to  the  draft  whirling  out  the  fine,  light  silica  powder  from  the  crucible. 

6.  Error  due  to  additional  silica  from  contaminated  reagents  or  from  the  porce- 
lain dishes  or  glassware  in  which  the  solution  was  evaporated.    A  blank  of  0.01% 
on  the  sodium  carbonate  will  make  an  error  of  0.1%  per  gram  sample  in  an 
ordinary  fusion  where  10  grams  of  the  flux  are  required. 

7.  Error  due  to  loss  of  weight  of  the  platinum  crucible  during  the  blasting. 

8.  Incomplete  removal  of  water,  which  is  held  tenaciously  by  the  silica. 
Furthermore,  weighing  of  the  residue  should  be  done  quickly,  as  the  finely  divided 
silica  tends  to  absorb  moisture. 

Two  general  procedures  will  be  given  for  treatment  of  the  acid  decomposa- 
ble and  undecomposable  silicates.  It  is  frequently  advisable  to  use  these  two 
procedures  in  conjunction,  extracting  the  material  first  with  acid,  and  then  fusing 


SILICON  369 

the  insoluble  residue  with  sodium  carbonate;  this  procedure  is  used  when  a 
gritty  residue  remains  after  the  acid  extraction.  Following  the  general  procedures 
for  decomposition  of  silicates,  certain  special  methods  will  be  given. 

List  of  Most  Important  Silicates.  Silicates  decomposed  by  acids.  Allanite;  allo- 
phane;  analcite;  botryolite;  brewsterite;  calamine;  chabasite;  croustedtitite;  datolite 
(hydrated  silicate  and  borate  of  Ca  with  Al  and  Mg);  dioptase;  eulytite;  gadolin- 
ite;  gahlenite;  helvite;  ilvaite  (silicate  ferrous  and  ferric  iron  with  Al^Os,  CaO  and 
MgO);  laumonite;  melinite;  natrolite  (hydrated  silicate  of  Al  and  Na  with  Fe  and 
CaO);  okenite;  olivine  (silicate  of  Fe  and  Mg);  pectolite;  prehenite  (hydrated  Al  and 
Ca  silicate  with  Fe,  Mn,  K,  Na,  etc.);  teproite;  wernerite;  woolastonite;  zaolite. 

Silicates  undecomposed  by  acids.  Albite;  audalusite;  augite;  axinite;  beryl; 
carpholite;  cyanite;  diallage,  epidote  (silicate  of  Fe,  Al  and  Ca  with  FeO,  Mn;  Mg, 
K,  Na);  euclase;  feldpsar  (silicate  of  K,  Na,  Al,  Fe,  Ca  and  Mg);  garnet;  lolite; 
labradorite;  (micas  of  K  and  Mg);  orthoclase;  petalite;  pinite,  prochlorite;  pumice; 
serpentine;  sillimanite,  talc,  topaz,  tourmaline  (Fe2O3,  FeO,  Mn,  Al,  Ca,  Mg,  K,  Na, 
Li,  SiO2,  B2O3,  P2O5,  F);  vesuvianite. 

Preparation  of  the  Substance  for  Decomposition 

If  the  material  is  an  ore  or  mineral  it  is  placed  on  a  steel  plate  within  a  steel 
ring  and  broken  down  by  means  of  a  hardened  hammer  to  small  lumps  and  finally 
to  a  coarse  powder.  A  quartered  portion  of  this  is  air  dried  and  ground  as  fine 
as  possible  in  an  agate  mortar  and  preserved  in  a  glass-stoppered  bottle  for 
analysis. 

Analyses  are  based  on  this  air-dried  sample.  If  moisture  is  desired  it  may  be 
determined  on  a  large  sample  of  the  original  material.  Hygroscopic  moisture 
is  determined  on  the  ground,  air-dried  sample,  by  heating  for  an  hour  at  105 
to  107°  C. 

Decomposition  of  the  Material,  General  Procedures 

Silicates  Decomposed   by  Acids 

Acid  extraction  of  the  silicates.  0.5  to  1  gram  of  the  finely  pulverized 
material  placed  in  a  beaker  or  casserole  is  treated  with  10  to  15  cc.  of  water  and 
stirred  thoroughly  to  wet  the  powder.1  It  is  now  treated  with  50  to  100  cc.  of 
strong  hydrochloric  acid  and  digested  on  the  water  bath  for  fifteen  or  twenty 
minutes  with  the  beaker  or  casserole  covered  by  a  watch-glass.  If  there  is 
evidence  of  sulphides  (pyrites),  etc.,  10  to  15  cc.  of  concentrated  nitric  acid  are 
now  added  and  the  containing  vessel  again  covered.  After  the  reaction  has 
subsided,  the  glass  cover  is  raised  by  means  of  riders  and  the  mixture  evaporated 
to  dryness  on  the  water  bath.  (This  evaporation  may  be  hastened  by  using  a 
sand  bath,  boiling  down  to  small  bulk  at  comparatively  high  temperature,  then 
to  dryness  on  the  water  bath.  Decomposition  is  complete  if  no  gritty  particles 
remain.  A  flocculent  residue  will  often  separate  out  during  the  digestion,  due 
to  partially  dehydrated  silicic  acid,  hydrated  silicic  acid,  Si(OH)4  is  held  in 
solution.)  The  silicic  acid  is  converted  to  silica,  Si02,  the  residue  taken  up  with 
dilute  hydrochloric  acid,  silica  filtered  off,  washed  with  water  acidified  with  hydro- 
chloric acid,  and  estimated  according  to  the  procedure  given  later. 

1  Water  is  added  to  the  sample  and  then  acid,  as  strong  acid  added  directly  would 
cause  partial  separation  of  gelatinous  silicic  acid,  which  would  form  a  covering  on  the 
undecomposed  particles,  protecting  them  from  the  action  of  the  acid. 


370  SILICON 


Silicates  Not  Decomposed  by  Acids 

Fusion  with  Sodium  Carbonate  or  Sodium  Bicarbonate.  0.5  to  1  gram 
of  the  air-dried,  pulverized  sample  is  placed  in  a  large  platinum  crucible  or  dish 
in  which  has  been  placed  about  5  grams  of  anhydrous  sodium  carbonate.  The 
sample  is  thoroughly  mixed  with  the  carbonate  by  stirring  with  a  dry  glass  rod, 
from  which  the  adhering  particles  are  brushed  into  the  crucible.  A  little  car- 
bonate is  sprinkled  on  the  top  of  the  mixture  and  the  receptacle  covered.  It 
is  heated  to  dull  redness  for  five  minutes  and  then  gradually  heated  up  to  the 
full  capacity  of  a  Me"ker  burner.  When  the  mix  has  melted  to  a  quite  clear  liquid, 
which  generally  is  accomplished  with  twenty  minutes  of  strong  heating,  a  platinum 
wire  with  a  coil  on  the  immersed  end  is  inserted  in  the  molten  mass,  and  this 
allowed  to  cool.  The  fusion  is  removed  by  gently  heating  the  crucible  until  the 
outside  of  the  mass  has  melted,  when  the  charge  is  lifted  out  on  the  wire,  and  after 
cooling  disintegrated  by  placing  it  in  a  beaker  containing  about  75  cc.  dilute  HC1 
(1  partHCl  to  2  parts  H20),  covering  the  beaker  to  prevent  loss  by  spattering. 
The  crucible  and  lid  are  cleaned  with  dilute  hydrochloric  acid,  adding  this  acid 
to  the  main  solution.  When  the  disintegration  is  complete,  the  solution  is 
evaporated  to  dryness  and  silica  is  estimated  according  to  directions  given  later. 

If  decomposition  is  incomplete,  gritty  material  will  be  found  in  the  beaker 
upon  treatment  of  the  fusion  with  dilute  acid.  If  this  is  the  case,  it  should  be 
filtered  off  and  fused  with  a  second  portion  of  sodium  carbonate,  and  the  fusion 
treated  as  directed  above. 

NOTES.  Fusions  with  soluble  carbonates  are  generally  best  effected  with  the 
sodium  salt,  except  in  fusions  of  niobates,  tantalates,  tungstates,  where  the  potas- 
sium salt  is  preferred  on  account  of  the  greater  solubility  of  the  potassium  compounds. 
Sodium  alone  has  an  advantage  over  the  mixed  carbonates,  Na2CO3+K2COa,  as  silica 
has  a  high  melting-point  and  a  flux,  which  fuses  at  810°  C.,  is  more  apt  to  cause  dis- 
integration of  the  silicate  than  the  mixture,  which  melts  at  690°  C. 

Prolonged  blasting  is  undesirable,  as  it  renders  the  fusion  less  soluble.  Aluminum 
and  iron  are  also  rendered  difficultly  soluble,  when  their  oxides  are  heated  to  a  high 
temperature  for  some  tune. 

If  the  melt  is  green,  it  is  best  to  dissolve  out  the  adhering  melt  from  the  crucible 
with  dilute  nitric  acid,  as  a  manganate  (indicated  by  the  color),  if  present,  will  evolve 
free  chlorine  by  its  action  on  HC1  and  this  would  attack  the  platinum. 

Fluorides.1  In  presence  of  fluorides  the  melt  is  extracted  with  water  (an 
acid  extraction  would  volatilize  some  of  the  silica),  and  the  extract  filtered  off 
from  the  insoluble  carbonates.  To  the  filtrate  is  added  about  5  grams  of  solid 
ammonium  carbonate,  and  the  mix  warmed  to  40°  C.  and  allowed  to  stand  for 
several  hours.  The  greater  part  of  the  silica  is  precipitated.  This  is  filtered  off 
and  washed  with  water  containing  ammonium  carbonate.  Preserve  this  with 
the  insoluble  carbonate  for  later  treatment.  The  filtrate,  containing  small 
amounts  of  silicic  acid,  is  treated  with  1  to  2  cc.  of  ammoniacal  zinc  oxide  solu- 
tion (made  by  dissolving  C.P.  moist  zinc  oxide  in  ammonia  water).  The  mix- 
ture is  boiled  to  expel  ammonia  and  the  precipitate  of  zinc  silicate  filtered  off. 
The  precipitate  is  washed  into  a  beaker  through  a  hole  made  in  the  filter,  and  the 
adhering  material  dissolved  off  with  dilute  HC1,  enough  being  added  to  dissolve 
the  remaining  residue.  This  is  evaporated  to  dryness  and  silica  separated  as 
usual.  Meantime  the  insoluble  carbonate  is  dissolved  with  HC1,  evaporated  to 

1  Sodium  bicarbonate  may  be  used  in  place  of  the  carbonate  with  excellent  results. 


SILICON  371 

dryness  and  any  silica  it  contains  recovered.    Finally  all  three  portions  of 
silica  are  combined,  ignited  and  silica  estimated  as  usual. 

Special  Procedures  for  Decomposing  the  Sample 

Treatment  of  Iron  and  Steel  for  Silica.  One  gram  of  pig-iron  castings, 
or  5  grams  of  steel  are  taken  for  analysis,  both  the  fine  and  coarse  drillings  being 
taken  in  about  equal  proportion.  (Fine  particles  contain  more  silicon  than 
the  coarse  chips.)  Twenty  to  50  cc.  of  dilute  nitric  acid  (sp.gr.  1.135)  are  added 
to  the  sample  in  a  250-cc.  beaker  or  small  casserole,  and  this  covered.  If  the 
action  is  violent,  cooling,  by  placing  the  beaker  in  cold  water  until  the  violent 
action  has  subsided,  is  advisable.  Twenty  cc.  of  50%  sulphuric  acid  are  added 
and  the  solution  evaporated  on  the  hot  plate  to  S03  fume's.  After  cooling, 
150  cc.  of  water  are  added  and  2  to  5  cc.  dilute  sulphuric  acid.  The  mixture  is 
heated  until  the  iron  completely  dissolves  and  the  silica  is  filtered  off  onto  an 
ashless  filter,  washed  with  hot  dilute  hydrochloric  acid  (sp.gr.  1.1),  and  with 
hot  water  until  free  from  iron.  The  residue  is  ignited  and  the  silica  estimated 
according  to  the  procedure  given  later. 

Pig  iron  and  cast  iron  may  be  decomposed  by  digestion  with  a  mixture  of  8  parts 
by  volume  of  HN03  (sp.gr.  1.42),  5  parts  of  H2S04  (sp.gr.  1.84),  and  17  parts  of  water. 

Steel  and  wrought  iron  may  be  disintegrated  by  a  mixture  of  8  parts  by  volume 
of  HN03  (sp.gr.  1.42),  4  parts  H2S04  (1.84),  and  15  volumes  of  water. 

Ferro  Silicons.  Dilute  hydrochloric  acid,  1  volume  of  acid  (sp.gr.  1.19), 
with  2  volumes  of  water  is  a  better  solvent  than  the  strong  acid. 

Steels  Containing  Tungsten,  Chromium,  Vanadium  and  Molybdenum. 
Fusion  with  potassium  acid  sulphate,  KHS04,  in  a  platinum  dish,  or  sodium  per- 
oxide in  a  nickel  crucible  will  generally  decompose  the  material.  Sodium  per- 
oxide is  of  special  value  in  decomposing  chromium  alloys. 

Silicon  Carbide,  Carborundum.  This  is  best  brought  into  solution  by 
fusion  with  potassium  hydroxide  in  a  nickel  crucible.  Sulphuric,  hydrochloric, 
nitric  acids,  or  aqua  regia  have  no  effect  upon  this  refractory  material. 

Sulphides,  Iron  Pyrites,  etc.  These  require  oxidation  with  strong  nitric  acid  or 
a  mixture  of  bromine  and  carbon  tetrachloride,  followed  by  nitric,  exactly  accord- 
ing to  the  procedure  given  for  solution  of  pyrites  in  the  determination  of  sulphur. 
The  sample  is  taken  to  dryness  and  then  hydrochloric  acid  added  and  the  solution 
again  evaporated.  The  residue  is  dehydrated  and  silica  determined  as  usual. 

Slags  and  Roasted  Ores.  Digestion  with  hydrochloric  acid  according  to  the 
first  general  procedure  is  best.  The  addition  of  nitric  acid  to  decompose  sul- 
phides may  be  necessary. 

Decomposition  of  silicates  by  fusion  with  lead  oxide  (method  of  Jannasch), 
and  calcium  carbonate  and  ammonium  chloride  (method  of  Hillebrand),  are  of 
value  when  sodium  is  desired  on  the  same  sample.  The  procedures  are  given 
under  chapters  on  Sodium  and  Potassium. 

NOTE.  K2CO3  is  preferred  to  Na2CO3  for  fusion  of  tungstates,  niobates  and  tan- 
talates  on  account  of  the  greater  solubility  of  the  potassium  salts.  For  corundum 
and  alumina  silicates  Na2CO3  is  preferred  as  double  salt  of  potassium  and  aluminum 
are  less  soluble  than  the  sodium  salt.1 

Fluorides  of  silicon  are  fused  with  boric  acid,  BF3  is  volatilized,  SiF4  is  not  formed. 
P.  Jannasch,2 

1 J.  L.  Smith,  Am.  Jour.  Sci.  (2),"40,  248,  1865.    C.  N.,  12,  220,  1865. 
2  Ber.,  28,  2822,  1896. 


372  SILICON 

PROCEDURE   FOR  THE  DETERMINATION  OF  SILICON 

AND  SILICA 

As  has  been  stated,  the  gravimetric  method  for  determination  of  silica 
is  the  only  satisfactory  procedure  for  estimation  of  this  substance.  The  oxida- 
tion of  the  element  and  its  isolation  have  been  dealt  with  in  the  section  Prepara- 
tion and  Solution  of  the  Sample.  The  following  directions  are  for  purification 
and  final  weighing  of  the  element  in  the  form  of  its  oxide,  silica,  Si02. 

Extraction  of  the  Residue — First  Evaporation.  The  residue,  obtained 
by  evaporation  of  the  material  after  decomposition  of  the  silicate,  by  acids  or  by 
fusion,  as  the  case  required,  is  treated  with  15-25  cc.  of  hydrochloric  acid  (sp.gr. 
1.1)  covered  and  heated  on  the  water  bath  10  minutes.  After  diluting  with  an 
equal  volume  of  water,  filtration  is  proceeded  with  immediately,  and  the  silica 
is  washed  with  a  hot  solution  consisting  of  5  cc.  hydrochloric  acid  (sp.gr.  1.2) 
to  95  cc.  of  water  and  finally  with  water.  This  nitration  may  be  performed 
with  suction.  The  filtrate  and  washings  are  evaporated  to  small  volume  on  a 
sand  bath  and  then  to  dryness.  This  contains  the  silica  that  dissolved  in  the 
first  extraction. 

Second  Evaporation.  The  residue  obtained  from  evaporation  of  the  filtrate 
is  dehydrated  for  2  hours  at  105-110°  C.1  and  extracted  with  10  cc.  of  hydrochloric 
acid  (sp.gr.  1.1)  covered  and  heated  on  the  water  bath  for  ten  minutes  diluted  to 
50  cc.  with  cold  water  and  filtered  immediately,  without  suction.  The  residue  is 
washed  with  cold  water  containing  1  cc.  concentrated  hydrochloric  acid  to  99  cc. 
water,  the  washed  residue  containing  practically  all 2  the  silica,  that  went  into  solu- 
tion in  the  first  extraction,  is  combined  with  the  main  silica  residue.  This  is  gently 
heated  in  a  platinum  crucible  until  the  filters  are  thoroughly  charred,  and  then 
ignited  more  strongly  to  destroy  the  filter  carbon  and  finally  blasted  over  a  Me"ker 
burner  for  at  least  thirty  minutes,  or  to  constant  weight,  the  crucible  being  covered. 
After  cooling  the  silica  is  weighed.  For  many  practical  purposes  this  residue  is 
accepted  as  silica,  unless  it  is  highly  colored.  For  more  accurate  work,  especially 
where  contamination  is  suspected  (silica  should  be  white),  this  residue  is  treated 
further. 

Estimation  of  True  Silica.  Silica  may  be  contaminated  with  BaS04,  Ti02, 
A1203,  Fe203,  P205  combined  (traces  of  certain  rare  elements  may  be  present). 
The  weighed  residue  is  treated  with  3  cc.  of  water,  followed  by  several  drops  of 
concentrated  sulphuric  acid  and  5  cc.  of  hydrofluoric  acid,  HF  (hood).  After 
evaporation  to  dryness,  the  crucible  is  heated  to  redness  and  again  cooled  and 
weighed.  The  loss  of  weight  represents  silica,  Si02.8 

1  Dehydration  of  silica  is  aided  by  the  presence  of  lime  and  retarded  by  magnesia. 
In  presence  of  the  latter  a  soluble  magnesium  silicate  will  form  if  the  dehydration 
is  conducted  at  a  temperature  much  above  110°  C.,  hence  it  is  better  to  avoid  this 
by  taking  more  time  and  heating  to  100  or  105°  as  recommended. 

Sodium  chloride  has  a  solvent  action  on  silica,  the  reaction  of  HC1  on  sodium 
silicate  being  reversible;  2HC1+ Na2SiO3£+2NaCl+H2SiO3.  An  evaporation  of 
the  filtrate  to  dryness  will  recover  the  greater  part  of  the  silica  thus  dissolved. 

2  Not  more  than  0.1%  of  the  original  SiO2  may  still  be  in  solution. 

3  Silicic  acid  cannot  be  completely  dehydrated  by  a  single  evaporation  and  heating, 
nor  by  several  such  treatments,  unless  an  intermediate  filtration  of  silica  is  made. 
If,  however,  silica  is  removed  and  the  filtrate  again  evaporated  to  dryness  and  the 
residue  heated,  the  amount  of  silica  remaining    in  the  acid  extract  is  negligible. 
(See  Article  by  Dr.  W.  E.  Hillebrand,  Jour.  Am.  Soc.,  24.) 


SILICON  373 

NOTES.     Lenher  and  Truog  make  the  following  observations  for  determining  silica:1 

1.  In  the  sodium  carbonate  fusion  method  with  silicates,  there  is  always  a  non- 
volatile residue  when  the  silica  is  volatilized  with  hydrofluoric  and  sulphuric  acids. 

2.  The  non-volatile  residue  contains  the  various  bases,  and  should  be  fused  with 
sodium  carbonate  and  added  to  the  filtrate  from  the  silica  when  the  bases  are  to  be 
determined. 

3.  In  the  dehydration  of  the  silica  from  the  hydrochloric  acid  treatment  of  the 
fusion,  the  temperature  should  never  be  allowed  to  go  above  110°. 

4.  Dehydrated  silica  is  appreciably  soluble  in  hydrochloric  acid  of  all  strengths. 
With  the  dilute  acid  used,  this  error  is  almost  negligible. 

5.  Dehydrated  silica  is  slightly  soluble  in  solutions  of  the  alkaline  chlorides.     As 
sodium  chloride  is  always  present  from  the  sodium  carbonate  fusion,  an  inherent  error 
is  obviously  thus  introduced. 

6.  The  dehydrated  silica  along  with  the  mass  of  anhydrous  chlorides  must  not  be 
treated  first  with  water,  since  hydrolysis  causes  the  formation  of  insoluble  basic  chlorides 
of  iron  and  aluminum,  which  do  not  dissolve  completely  in  hydrochloric  acid. 

7.  Hydrochloric  acid  (sp.gr.  1.1)  in  minimum  amount  should  be  used  first  to  wet 
the  dehydrated  chlorides  and  should  be  followed  by  water  to  bring  the  volume  to 
about  50  cc.,  after  which  the  silica  should  be  filtered  off  as  quickly  as  possible. 

8.  Pure  silica  comes  quickly  to   constant  weight  on  ignition.     Slightly  impure 
silica  frequently  requires  long  heating  with  the  blast  flame  in  order  to  attain  constant 
weight,  and  is  then  commonly  hydroscopic. 

9.  Evaporations  of  the  acidulated  fusion  in  porcelain  give  practically  as  good  results 
as  when  platinum  is  used. 

10.  Filtration  of  the  main  bulk  of  the  silica  after  one  evaporation  is  desirable,  inas- 
much as  the  silica  is  removed  at  once  from  the  solutions  which  act  as  solvents. 

11.  Dehydration  of  the  silica  under  reduced  pressure  has  no  advantages  over  the 
common  evaporation  at  ordinary  atmospheric  pressure. 

12.  Excessive  time  of  dehydration,  viz.,  four  hours,  possesses  no  advantages. 

13.  Excessive  amounts  of  sodium  carbonate  should  be  avoided,  since  the  sodium 
chloride  subsequently  formed  exerts  a  solvent  action  on  the  silica.     The  best  propor- 
tions are  4-5  sodium  carbonate  to  1  of  silicate.     Less  than  4  parts  of  sodium  carbonate 
is  frequently  insufficient  completely  to  decompose  many  silicates. 

14.  The  non-volatile  residue  has  been  found  to  be  invariably  free  from  sodium. 
Pure  silica,  on  fusion  with  sodium,  carbonate,  subsequently  gives  no  non-volatile  residue. 

ANALYSIS  OF  SILICATE  OF  SODA 
Determination  of  Na2O 

Five  grams  of  the  sample  are  dissolved  in  about  150  cc.  of  water  and  heated; 
1  cc.  of  phenolphthalein  is  added  and  then  an  excess  of  standard  sulphuric  acid 
from  a  burette.  The  excess  acid  is  titrated  with  standard  sodium  hydroxide 
to  a  permanent  pink. 

H2S04X0.6321=Na20. 

Silica.  Ten  grams  of  the  sample  are  acidified  with  hydrochloric  acid  and 
evaporated  to  dryness  on  the  steam  bath.  The  treatment  is  repeated  with  addi- 
tional hydrochloric  acid  and  then  the  residue  taken  up  with  5  cc.  of  the  acid  and 
200  cc.  of  water.  The  residue  is  digested  to  dissolve  the  soluble  salts,  filtered, 
washed  and  ignited.  Silica  is  determined  by  loss  of  weight  by  volatilization 
of  the  silica  with  hydrofluoric  and  sulphuric  acids.  The  filtrate  is  made  to  1  liter. 

Iron  and  Alumina.    Five  hundred  cc.  (5  grams)  of  the  filtrate  from  the  silica 

determination  are  oxidized  with  HN03  and  the  iron  and  alumina  precipitated 

with  ammonia,  washed,  ignited  and  weighed  as  A1203  and  Fe203.    The  residue 

is  dissolved  by  digestion  with  hydrochloric  acid  or  by  fusion  with  sodium  acid 

1  Victor  Lenher  and  Emil  Truog,  Jour.  Am.  Chem.  Soc.,  38,  1050,  May,  1916. 


374  SILICON 

sulphate,  and  subsequent  solution  in  hydrochloric  acid.  Iron  is  determined  by 
titration  in  a  hot  hydrochloric  acid  solution  with  standard  stannous  chloride, 
SnCl2,  solution  as  usual.  If  only  a  small  amount  of  precipitate  of  iron  and 
alumina  is  present,  as  is  generally  the  case,  solution  by  hydrochloric  acid  is  prefer- 
able to  the  fusion  with  the  acid  sulphate.  The  latter  is  used  with  larger  amounts 
of  the  oxides. 

Lime,  CaO.  This  is  determined  in  the  filtrate  from  iron  and  alumina  by 
precipitation  as  the  oxalate  and  ignition  to  CaO. 

Magnesia,  MgO.  This  is  determined  in  the  filtrate  from  lime  by  precipita- 
tion with  sodium  ammonium  phosphate.  The  precipitate  is  ignited  and  weighed 
as  Mg2P207  and  calculated  to  MgO.  Precipitate X 0.3621  =MgO. 

Combined  Sulphuric  Acid.  One  hundred  cc.  of  the  filtrate  from  the  silica 
determination  ( =  1  gram)  is  treated  with  BaCl2  solution  and  sulphuric  acid 
precipitated  as  BaS04. 

BaS04X0.4202=H2S04    or     X0.3430=S03. 

Sodium  Chloride.  Ten  grams  of  the  silicate  of  soda  are  dissolved  in  100  cc. 
of  water  and  made  acid  with  HN03  in  slight  excess  and  then  alkaline  with  MgO. 
Cl  is  titrated  with  standard  AgN03  solution. 

Water.  This  is  determined  either  by  difference  or  by  taking  10  grams  to 
dryness  and  then  heating  over  a  flame  and  blasting  to  constant  weight. 

NOTE.     For  detailed  procedures  for  each  of  the  above  see  special  subject. 

ANALYSIS  OF  SAND,  COMMERCIAL  VALUATION 

Silica.  Two  grams  of  the  finely  ground  material  are  fused  in  a  platinum  cru- 
cible with  10  grams  of  fusion  mixture  (K2C03+Na2C03)  by  heating  first  over  a 
low  flame  and  gradually  increasing  the  heat  to  the  full  blast  of  a  Me*ker  blast 
lamp.  When  the  fusion  has  become  clear  it  is  cooled  by  pouring  on  a  large  plati- 
num cover.  The  fused  mass  on  the  cover  and  that  remaining  in  the  platinum 
crucible  are  digested  in  a  covered  beaker  with  hot  hydrochloric  acid  on  the  steam 
bath.  The  solution  is  now  evaporated  to  dryness,  taken  up  with  a  little  water 
and  25  cc.  of  concentrated  HC1  and  again  taken  to  dryness.  Silica  is  now  deter- 
mined by  the  procedure  outlined  under  the  general  method  on  page  372. 

Ferric  Oxide  and  Alumina.  The  filtrate  is  oxidized  with  crystals  of  solid 
potassium  chlorate,  KC103,  and  iron  and  aluminum  hydroxides  precipitated 
with  ammonia.  The  precipitate  is  filtered,  washed,  ignited  and  weighed  as 
Al203+Fe203. 

Calcium  Oxide.  To  the  ammoniacal  filtrate  10  cc.  of  ammonium  oxalate 
solution  are  added,  the  solution  heated  to  boiling  and  the  precipitate  allowed 
to  settle  until  cold.  The  solution  should  not  be  over  200  cc.  The  calcium 
oxalate  is  filtered  off,  washed  and  ignited.  The  residue  is  weighed  as  CaO. 

Magnesium  Oxide.  The  filtrate  from  the  lime  is  made  strongly  ammoniacal 
and  10  cc.  of  sodium  ammonium  phosphate  added.  The  solution  during  the 
addition  is  allowed  to  stand  cold  for  some  time,  three  to  four  hours.  The  pre- 
cipitate is  filtered  and  washed  with  dilute  ammonia  (1  of  reagent  to  3  parts  of 
water),  then  ignited  and  weighed  as  Mg2P207.  This  weight  multiplied  by 
0.3621=  MgO. 

For  more  detailed  directions  see  the  individual  subjects  under  the  chapters 
devoted  to  the  element. 


SILVER 

W.  G.  DERBY 

Ag,  at.wt.  107.88;  sp.  gr.  10.50-10.57;  m.p.  960.5°  C.;    b.p.  about  1950°  C.; 
oxides,  Ag2O,  Ag4O,  Ag2O2 

DETECTION 

A  trace  of  silver  in  most  substances  is  detected  with  greatest  certainty  by 
furnace  assay  methods. 

The  wet  method  of  detection  of  silver  most  commonly  practiced,  depends  upon 
observation  of  the  properties  of  the  precipitate  formed  by  the  addition  of  a  not 
excessive  amount  of  alkaline  chloride  to  a  cold  nitric  or  sulphuric  acid  solution  of 
the  substance  undergoing  examination.  One-tenth  milligram  of  silver  precipi- 
tated as  silver  chloride  in  a  cold  200-cc.  acid  solution  gives  a  very  perceptible 
opalescence  to  the  liquid. 

Silver  chloride  is  white  when  freshly  precipitated,  tinted  pink  when  palladium 
is  present;  in  colorless  liquids  on  exposure  to  light  turns  brown,  violet,  blue  or 
black.  By  agitation,  heating  or  long  standing  the  precipitate  becomes  coagulated 
or  granular  and  in  such  a  state  is  retained  by  an  ordinary  filter.  The  presence  of 
some  forms  of  organic  matter  prevents  coagulation. 

Silver  chloride  is  dissolved  by  concentrated  hydrochloric  acid;  raising  the  tem- 
perature of  the  acid  assists  the  action.  It  is  dissolved  by  sodium  thiosulphate, 
alkali  cyanides,  mercuric  nitrate,  and  alkaline  chlorides. 

From  mercurous  chloride,  silver  chloride,  except  when  constituting  a  small 
proportion  of  the  precipitate,  is  distinguished  by  its  solubility  without  decomposi- 
tion in  ammonia.  Precipitation  from  its  ammoniacal  solution  is  accomplished  by 
acidifying.  Lead  chloride,  precipitable  also  by  hydrochloric  acid,  is  not  flocculent, 
does  not  coagulate,  but  dissolves  quite  freely  by  heating.  Addition  of  hydro- 
chloric acid  to  a  solution  of  silicon,  tellurium,  thallium,  tungsten  or  molybdenum 
may  produce  a  precipitate,  in  each  case,  easily  distinguishable  from  that  of  silver 
chloride,  but  may  mask  traces  of  the  salt. 

Silver,  in  a  cold  solution  containing  free  nitric  acid,  only  a  small  amount  of 
colored  salts  and  no  mercury,  may  be  detected  through  the  formation  of  a  white 
precipitate,  similar  in  appearance  to  silver  chloride,  by  addition  of  a  slight 
excess  of  an  alkaline  thiocyanate. 

When  a  solution  of  silver  salt l  is  added  to  a  mixture  of  20  cc.  ammonium 
salicylate  (20  gr.ims.  salicylic  acid  neutralized  with  ammonia,  a  slight  excess  added 
and  the  whole  made  up  to  1000  cc.)  and  20  cc.  of  a  5%  solution  of  ammonium  per- 
sulphate added,  an  intense  brown  color  is  produced,  which  will  detect  the  presence 
of  a  0.01  milligram  of  silver.  Lead  does  not  affect  the  test. 

When  it  appears  that  the  chloride  or  thiocyanate  test  for  silver  is  not  positive 
on  account  of  the  presence  of  other  precipitable  elements,  the  precipitate,  after  it 

1  A.  W.  Gregory,  Chem.  Soc.  Proc.,  24, 125,  1908. 
375 


376  SILVER 

settles,  is  filtered  through  the  finest  quality  of  paper,  and  the  mixture  of  the  ash  of 
the  incinerated  filter  with  dry  potassium  carbonate  heated  on  charcoal  with  a 
mouth  blowpipe.  If  silver  is  present  and  not  associated  with  a  large  amount  of 
palladium,  there  will  be  found  on  the  charcoal  pellicles  of  the  color  characteristic 
of  silver,  which  have  no  white  or  yellow  sublimate  when  melted  in  the  oxidizing 
flame  of  the  blowpipe.  The  pink  palladium  salts  of  silver  precipitated  by  a  chloride 
or  thiocyanate  before  the  blowpipe  produces  metal  which  is  dull  in  appearance  and 
not  readily  melted. 

NOTES.  Silver  may  be  recognized  in  a  solution  of  concentration  1  to  240,000  by 
the  reduction  of  its  salts  with  alkaline  formaldehyde.1  Whitby's2  method  of  detec- 
tion and  estimation  of  small  amounts  of  silver  depends  upon  the  formation  of  a 
yellow  color  through  addition  of  sucrose  and  sodium  hydrate.  Ammonium  hydrate 
interferes,  but  bismuth,  cadmium,  copper,  mercury  of  either  valence,  lead  or  zinc,  in 
amounts  equal  to  that  of  the  silver,  do  not.3  Maletesta  and  DeNola  add  to  the  solu- 
tion to  be  tested  a  few  drops  of  a  solution  of  nitrate  of  chromium  and  then  potassium 
hydrate  to  alkalinity.  A  brownish  turbidity  or  black  precipitate  of  silver  oxide  forms. 
The  limit  of  sensitiveness  is  0.5  milligram  in  100  cc. 

ESTIMATION 

Silver  is  determined  in  copper,  lead,  silver,  sulphur  or  other  ores,  in  copper  and 
lead  furnace  by-products,  and  in  lead  by  furnace  assay  methods,  in  which  a  prelim- 
inary acid  treatment  of  the  sample  is  rarely  employed;  in  native  copper  ore,  in 
copper,  copper  alloys,  gold,  gold  alloys  and  in  the  slime  from  the  electrolytic  refin- 
ing of  copper  or  lead  by  furnace  methods,  in  which  a  preliminary  acid  treatment  of 
the  sample  is  employed,  in  silver  alloys  by  volumetric  or  gravimetric  methods; 
in  mercury  by  a  gravimetric  method;  in  cyanide  mill  solution  or  solutions  contain- 
ing much  organic  matter  by  furnace  process  on  the  residue  obtained  by  evaporation 
or  precipitation;  in  silver  plating  electrolyte  by  electrolysis. 

Solubility.  Nitric  acid,  dilute  or  concentrated,  attacks  silver  rapidly  when  hot. 
The  presence  of  a  soluble  chloride,  iodide  or  bromide  in  the  solvent  or  substance 
will  retard  and  may  prevent  solution.  Unless  oxidizing  agents  are  present,  dilute 
sulphuric  acid  has  practically  no  action  on  massive  silver,  but  hot,  strong  acid 
commences  to  be  an  active  solvent  at  a  concentration  of  75%  H^SO-i.  Hydro- 
chloric acid  attacks  silver  superficially.  The  action  of  alkaline  hydrates  or  car- 
bonates in  solution  is  inappreciable;  in  a  state  of  fusion,  slight. 

Furnace  Assay  Methods.  These  will  be  described  in  the  chapter  devoted  to 
that  subject. 

GRAVIMETRIC   METHODS 
Determination  as  Silver  Chloride 

The  method  is  not  of  extreme  accuracy  in  the  presence  of  much  antimony, 
mercury  or  lead.  By  precipitating  silver  chloride  in  a  well-diluted  solution  by  a 
weak  solution  of  the  precipitant,  the  error,  on  account  of  its  property  of  tenaciously 
retaining  salts,  may  be  made  very  small.  Because  of  its  tendency  to  decompose, 
the  precipitate  of  silver  chloride  should  not  be  exposed  to  direct  sunlight  or  allowed 
to  stand  for  many  hours. 

1  Armani  and  Barboni,  Zeit.  Chem.  Ind.  Kolloide,  6,  290. 

2  Zeit.  Anorg.  Chem.,  67,  62;  C.A.,  4,  1444. 
«  Bull.  Chim.  Farm.,  52,  533. 


SILVER  377 

To  the  hot  nitric  or  sulphuric  acid  solution  of  silver,  diluted  to  about  500  cc., 
is  added,  with  constant  stirring,  a  few  cc.  at  a  time,  and  to  only  slight  excess,  a 
solution  of  hydrochloric  acid  containing  -^  the  per  cent  HC1. 

The -precipitate  of  silver  chloride  is  coagulated  by  heating,  or  brisk  stirring, 
the  liquid  cooled  to  room  temperature  and  filtered  through  a  tared  Gooch  crucible, 
which  has  been  thickly  bottomed  with  fiber  asbestos.  The  precipitate  is  washed 
with  water  containing  a  little  nitric  acid.  The  dried  crucible  is  heated  over  a 
flame  until  the  edges  of  the  precipitate  begin  to  fuse. 

AgClX  0.7526  =Ag. 

NOTE.  Alifeld  x  adds  5  cc.  ether  to  the  halide  solution,  before  precipitation,  to 
hasten  coagulation. 

Determination  as  Silver  Cyanide 

In  the  analysis  of  mercury,  the  nitric  acid  solution  of  the  metal  is  nearly  neu- 
tralized with  a  solution  of  sodium  carbonate.  Potassium  cyanide  solution  is  then 
added  until  the  precipitate,  which  first  forms,  is  dissolved.  Then  under  a  hood 
with  strong  draft,  dilute  nitric  acid  is  added  in  slight  excess  of  the  quantity  required 
to  combine  with  the  base  in  the  amount  of  potassium  cyanide  present.  The 
precipitate  of  silver  cyanide,  practically  insoluble  in  dilute  nitric  or  hydrocyanic 
acid,  is  coagulated  by  stirring  or  long  standing  and  filtered  from  the  cold  solution 
of  mercuric  nitrate  by  use  of  a  tared  paper-bottomed  Gooch  crucible.  The  pre- 
cipitate is  washed  with  cold  dilute  nitric  acid  (1-10)  until  a  test  of  the  washings  with 
hydrogen  sulphide  shows  the  absence  of  mercury.  The  crucible  is  dried  at  212° 
to  constant  weight. 

AgCNX  0.8057  =Ag. 

NOTES.  Determination  of  silver  as  metal  through  precipitation  with  hypophos- 
phorous  acid  2  as  silver  sulphide  or  as  silver  chromate  3  are  methods  of  doubtful 
technical  application. 

Electrolytic  Method  4 

According  to  the  strength  of  the  silver  bath  10  or  20  cc.  are  filtered  into  a  tared 
200-cc.  platinum  dish  and  according  to  the  greater  or  smaller  excess  of  cyanide 
present,  f  to  1  gram  of  potassium  cyanide  in  solution  is  added.  The  electrolyte 
diluted  to  about  a  half  inch  from  the  edge  of  the  dish  is  kept,  by  a  flame  under- 
neath, at  a  temperature  of  140  to  149°  F.  during  the  period  of  electrolysis  at 
N.D.ioo  =0.08  amp. 

Complete  precipitation,  which  requires  three  to  three  and  a  half  hours,  is 
recognized  by  test  with  ammonium  sulphide.  Without  interruption  of  the  cur- 
rent, by  use  of  a  siphon,  displacement  of  the  electrolyte  with  water  is  accomplished. 
The  dish  is  rinsed  with  alcohol  and  ether,  dried  at  212°,  weighed  and  silver  obtained 
calculated  to  grams  per  liter  or  cubic  foot. 

NOTES.  Benner  and  Ross  5  deposit  0.15  gram  in  twenty  minutes  with  a  current  of 
3  amperes  from  50  cc.  of  electrolyte  containing  8  grams  potassium  cyanide  and  2 
grams  potassium  hydrate  on  a  9-gram  platinum  gauze  cathode. 

1  Z.  anal.  Chem.,  48,  79. 

2  Mawrow  and  Mellow,  Zeit  anorg.  Chem.,  61,  96. 

3  Gooch  and  Bosworth,  Am.  J.  Sci.,  27,  241. 

4  Langbein,  "  Electro-Deposition  of  Metals,"  6th  Ed. 

5  J.  A.  C.  S.,  July,  1911,  1106. 


378  SILVER 

Exner  l  using  a  platinum  dish  as  the  cathode  and  a  2-in.  diameter  bowl-shaped 
spiral  anode  revolving  700  R.P.M.,  deposited  0.4900  gram  from  about  125  cc.  of  a 
hot  electrolyte  containing  2  grams  potassium  cyanide  in  ten  minutes  at  N.D.ioo  2 
amps. 

The  above  methods  presume  the  absence  of  other  metals  precipitable  under  the  con- 
ditions mentioned. 

VOLUMETRIC  METHODS 

Volhard's  Thiocyanate  Method.  This  method  is  especially  adapted  to  de- 
termination of  moderate  quantities  of  silver  in  cold  dilute  nitric  acid  solutions 
which  contain  no  mercury,  nitrous  acid,  or  a  greater  amount  of  yellow,  red  or 
brown-colored  salts  than  will  give  an  appreciable  tint  to  the  solution,  and  not  so 
large  amount  of  blue  salts  as  will  mask  the  end-point. 

The  presence  of  palladium  and  silver  chloride  interfere  with  the  accuracy  of 
the  detemination.  Bromide  or  iodide  of  silver  2  may  be  present. 

The  method  is  based  on  the  greater  affinity  of  silver  than  ferric  for  thiocyanate 
ions.  When  silver  thiocyanate  has  been  completely  precipitated,  the  excess  of 
alkali  thiocyanate,  in  the  presence  of  free  nitric  acid,  reacts  with  a  ferric  salt  with 
formation  of  a  reddish-brown  solution  of  ferric  thiocyanate. 

The  ferric  indicator  may  be  made  from  ferric  ammonium  sulphate,  ferric 
nitrate  or  from  ferrous  sulphate  by  adding  a  large  excess  of  nitric  acid  to  its  con- 
centrated solution  and  boiling  to  decompose  nitrous  acid.  Whatever  salt  is  used 
for  indicator  it  should  be  free  of  chlorine,  its  solution  made  of  constant  ferric 
strength  and  used  in  quantities  graduated  according  to  the  volume  of  the  liquid 
titrated.  A  saturated  solution  of  ferric  ammonium  sulphate  (1  cc.  to  each  20  cc. 
of  the  liquid  to  be  titrated),  is  a  convenient  form  of  indicator.  The  standard 
solution  commonly  employed  for  the  determination  of  silver  in  silver  plate,  for 
the  trial  assay  of  Dore*  metal  and  for  the  assay  of  silver  bullion  by  the  Gay-Lussac 
pipette  method  has  a  silver  value  of  10  milligrams  per  cc.  Since  both  the  com- 
monly employed  thiocyanate  salts  are  deliquescent,  it  is  unnecessary  to  weigh 
out  the  exact  quantity.  Ammonium  is  less  likely  to  contain  chlorine  than 
potassium  thiocyanate.  In  the  decimal  solution  (silver  value  1  milligram  per 
cc.),  the  liter  content  is  0.7-0.8  gram  of  ammonium  or  0.9-1.0  gram  of  po- 
tassium thiocyanate.  Solution  is  made  with  chlorine-free  water. 

For  standardizing  the  decimal  solution,  1  gram  of  standard  silver  is  dissolved 
in  a  funnel-closed  liter  flask  by  20  cc.  of  equal  volumes  of  nitric  acid  and  water. 
After  boiling  to  decompose  nitrous  acid  the  solution  is  made  up  to  mark  with 
water  at  room  temperature. 

When  using  the  standard  thiocyanate  solution  with  the  object  of  obtaining  very 
accurate  results,  it  is  good  practice,  instead  of  using  a  standard  solution  of  silver, 
to  obtain  the  standard  by  titrating,  simultaneously  with  the  assays,  solutions  of 
known  quantities  of  standard  silver  approximately  equal  in  amount  and  dissolved 
in  the  same  manner  as  the  assays. 

In  the  operation  of  titration,  after  addition  of  the  prescribed  proportion  of  ferric 
indicator,  standard  thiocyanate  solution  is  added  from  a  burette  to  the  cold  silver 
solution  in  500-cc.  Erlenmeyer  flask,  until  the  rate  of  bleaching  of  the  reddish- 
brown  color  slackens;  then  cautiously,  with  vigorous  agitation  after  each  addition, 

1  J.  A.  C.  S.,  Sept.,  1903,  900. 

'  Rosanoff  and  Hill,  J.  A.  C.  S.,  March,  1907,  273. 


SILVER  379 

until  the  liquid  shows  a  tendency  to  become  clear  above  the  settled  precipitate  and 
a  reddish,  tint  persists.  The  end-point  tint  obtained  in  standardizing  the  thio- 
cyanate  should  be  matched  in  titrating  the  assay  solutions.  In  case  the  end-point 
is  overrun,  standard  silver  solution  may  be  added  until  the  correct  tint  is  obtained, 
allowance  being  made  for  silver  so  added. 

Since  the  shade  of  color  at  the  end-point  is  dependent  upon  the  concentration 
of  ferric  salt  and  inasmuch  as  volume,  temperature,  amount  of  free  nitric  acid  and 
amount  of  silver  present  are  conditions  which  have  more  or  less  influence  upon 
the  determination,  such  conditions  as  prevailed  during  the  standardization  of  the 
thiocyanate  solution  should  be  maintained  in  the  operation  of  the  assay. 

NOTES.  Separation  from  colored  salts  may  be  brought  about  by  precipitating  the 
silver  with  a  very  slight  excess  of  thiocyanate,  allowing  the  precipitate  to  settle  until 
the  residual  liquor  is  clear,  washing  by  decantation  through  an  alundum  filter  cone 
or  asbestos-bottomed  Gooch  crucible,  placing  the  filter  and  contents  in  the  flask  in  which 


precipitation  took  place,  adding  strong  nitric  acid  and  heating  until  all  silver  thiocyanate 
is  decomposed.     Tit 


Itration  is  made  on  the  cold  dilute  solution. 


Palladium,  in  quantity  sufficient  to  color  the  solution,  can  be  eliminated  by  re- 
moval of  free  acid  through  evaporation  just  to  dryness,  immediately  taking  up 
with  water  and  adding  a  drop  or  two  of  a  saturated  solution  of  sodium  acetate, 
(free  of  chlorine) .  Pure  carbon  monoxide  is  passed  until  the  hot  liquid  is  decolor- 
ized. The  filtrate  from  the  palladium  after  addition  of  an  excess  of  nitric  acid  is 
titrated  when  cold. 

When  part  of  the  silver  is  present  as  silver  chloride,  as  an  unavoidable  product 
of  the  analysis,  it  should  be  removed  by  filtration  and  reduced  on  the  filter  with 
zinc  dust  after  removal  of  the  filtrate.  The  reduced  silver  is  washed  free  of  chlor- 
ide, dissolved  with  hot  20%  nitric  acid,  the  solution  washed  from  the  filter,  con- 
centrated by  boiling  and  added  to  the  filtrate  from  the  silver  chloride.  Titration 
may  then  be  made  on  the  silver  solution. 

In  the  application  of  the  Volhard  method  to  the  assay  of  a  cyanide  mill  solution,1 
a  measured  volume  of  the  solution  is  run  through  a  £-in.  layer  of  zinc  dust  in  a 
Gooch  crucible  with  care  to  keep  the  zinc  always  covered  with  the  solution.  The 
zinc  washed  into  beaker,  is  cautiously  dissolved  with  nitric  acid,  the  solution 
boiled,  diluted  and,  when  cold,  titrated  with  a  thiocyanate  solution  which  has 
been  standardized  by  a  silver  solution  which  contains  an  amount  of  zinc  the  same 
as  used  in  the  process  of  reduction. 

Qay-Lussac  Method 

This  very  accurate  method  is  especially  adapted  to  the  valuation  of  silver 
bullion,  but  may  be  applied  in  principle  to  the  determination  of  silver  in  a  nitric 
acid  solution  which  contains  as  little  as  100  milligrams  of  the  metal,  providing  the 
volume  of  the  solution  is  not  so  large  or  color  so  deep  as  to  make  a  precipitate  of 
silver  chloride  equivalent  to  0.1  milligrams  of  silver  indistinguishable.  Metals 
whose  presence  interfere  are  mercury  and  tin. 

The  method  is  founded  upon  the  almost  absolute  insolubility  of  silver  chloride 
or  bromide  in  cold  dilute  nitric  acid  and  the  property  of  the  precipitate  becoming 
so  completely  coagulated  through  agitation  that  it  settles  speedily,  leaving  a 

1  Clevenger,  Eng.  and  Min.  J.,  95,  892,  1913. 


380  SILVER 

liquid  sufficiently  clear  to  permit  of  observance  of  any  precipitate  produced  by 
further  addition  of  precipitant. 

The  presence  of  free  sulphuric  acid  is  prejudicial  to  a  very  close  determination, 
because  of  the  volume  of  liquid  required  to  keep  silver  sulphate  in  solution,  and 
also  because  the  result  of  agitation  after  addition  of  precipitant,  is  apt  to  be  a 
fine  precipitate  which  does  not  readily  settle. 

The  use  of  a  bromide  is  preferable  to  a  chloride  salt  as  a  reagent,  because  its 
silver  salt  is  less  affected  by  light,  coagulates  and  settles  more  readily,  will  suffer 
more  agitation  before  formation  of  a  fine,  slowly  settling  precipitate,  but  chiefly 
because  on  account  of  the  greater  insolubility  of  silver  bromide,  the  end-point  of 
the  operation  of  titration  is  more  sharply  defined. 

The  reagents  required  consist  of  chlorine-free  nitric  acid,  as  standard  solution 
of  an  alkali  bromide  or  chloride  of  approximately  decinormal  strength,  a  decimal 
solution  of  the  same  salt  having  a  silver-precipitating  value  of  1  milligram  per  cc., 
and  a  decimal  silver  solution  containing  1  milligram  of  silver  per  cc.  in  the 
form  of  silver  nitrate. 

In  the  assay  of  silver  bullion,  the  standard  solution  may  contain  5.42  grams  of 
sodium  chloride  or  11.03  grams  of  potassium  bromide  or  9.54  grams  of  dry  so- 
dium bromide  per  liter,  and  should  have  a  silver  precipitating  value,  as  indicated 
by  the  method,  of  about  1  gram  per  100  cc. 

The  factor  of  volume  change  per  degree  change  of  temperature  from  15  to  21°  C. 
is  approximately  0.00012;  from  20  to  26°,  0.00019;  from  25  to  31°  C.,  0.00024. 

Although  the  approximate  precipitating  value  should  be  known  by  previous 
test,  it  is  the  better  practice  to  determine  the  exact  value  by  running  two  or  more 
checks  of  pure  silver  simultaneously  with  each  batch  of  assays  than  to  apply 
the  temperature  correction  factor. 

The  decimal  salt  solution  is  best  made  from  C.P.  salts,  either  0.5149  gram 
sodium  chloride  or  1.1033  grams  potassium  bromide  per  liter. 

The  decimal  silver  solution  is  made  by  dissolving  1  gram  of  pure  silver  with  a 
few  cc.  of  nitric  acid  and  making  up  to  1  liter  with  distilled  water.  (See  Method 
for  Preparation  of  Pure  Silver,  page  384.) 

The  apparatus  required  consists  of  a  pipette  which  will  deliver  approximately 
100  cc.  with  an  accuracy  of  not  over  5  milligrams  variation  in  weight  of  the  stand- 
ard solution  at  constant  temperature  between  successive  deliveries,  10-cc.  burettes 
with  glass  stopcocks;  and  8-oz.  narrow  mouth,  round,  flint-glass  bottles  with  high, 
tightly  fitting  stoppers;  the  assay  bottles  should  be  of  a  quality  which  will  endure 
heating  in  a  steam  bath  or  in  a  hot  plate. 

The  Stas  or  Ricketts  overflow  pipette,  listed  by  all  laboratory  supply  firms,  is 
the  type  most  commonly  used.  This  pipette  is  filled  by  gravity  flow  through 
a  rubber  tube  from  the  standard  solution  reservoir  connected  to  the  discharge- 
end.  When  the  liquid  overflows,  the  top  is  closed  by  finger,  the  pinchcock  closed, 
the  supply  tube  removed  and  the  hanging  drop  wiped  off. 

Care  to  avoid  introduction  of  air  bubbles  into  the  pipette,  uniform  habit  in 
respect  to  pressure  of  the  finger  on  the  top,  and  method  of  wiping  off  the  hanging 
drop,  must  be  practiced  to  obtain  good  results. 

The  automatic  dividing  pipette  with  three-way  stopcock  shown  in  the  illustra- 
tion, will  give  remarkably  accurate  deliveries  when  properly  constructed  and 
manipulated.  This  type  of  pipette  of  the  form  ordinarily  furnished  by  supply 
houses,  will  rarely  deliver  with  sufficient  accuracy  for  bullion  assays. 

Since  the  end-point  by  the  Gay-Lussac  method  depends  upon  the  observance 


SILVER 


381 


of  cessation  of  precipitation,  it  is  evident,  in  order  to  avoid  undue  tediousness 
in  its  operation,  that  the  silver  content  of  the  amount  of  sample  taken  for  assay 
should  be  known  within  a  few  milligrams. 

This  may  be  ascertained  by  assay  of  1  gram  of  the  sample  by  the  Volhard 
method,  using  a  thiocyanate  solution  of  decinormal  strength,  or  by  cupellation  with 
application  of  a  correction  for  cupel  absorption. 

The  approximate  silver  value  having  been  determined,  such  an  amount  of 
the  sample  is  weighed  out  and  placed  in  an  assay  bottle,  as  will  contain  silver  in 
slight  excess  of  the  silver  equivalent  of  the  pipette  full  of  standard  salt  solution. 
Ten  to  15  cc.  of  nitric  (1.26  sp.gr.)  acid  are  added  and  the  bottle  kept  in  a  steam 
bath  or  on  a  moderately  hot  plate  until  solution  of  silver  is  complete. 


FIG.  59. — Apparatus  for  Determining  Silver.     Gay-Lussac  Method. 

To  the  cold  solution  of  the  sample  is  added  a  pipette  full  of  the  standard  salt 
solution  and  the  tightly  stoppered  bottle  agitated  until  the  precipitate  will  settle 
with  sufficient  completeness  to  permit  of  observance  of  any  turbidity  produced 
by  addition  of  either  of  the  decimal  solutions. 

More  agitation  than  is  absolutely  necessary  should  be  avoided,  because  of  the 
increasing  tendency  of  the  precipitate  toward  the  fine  granular  form,  which  settles 
slowly. 

On  account  of  alteration  of  the  character  01  cne  precipitate  by  sunlight, 
the  titration  should  be  carried  out  in  a  shaded  place  and  as  expeditiously  as 
possible. 

One-tenth  cc.  of  the  decimal  salt  solution  is  dropped  into  the  bottle,  and  holding 
the  bottle  against  a  dark  background,  the  appearance  of  the  cloud  of  precipitate 
is  noted. 


382  SILVER 

From  the  character  of  the  precipitate,  after  some  practice,  it  is  possible  to  judge 
whether  a  single  cc.  or  more  may  be  added  at  once,  or  whether  the  titration  must 
be  continued  by  one-tenth  cc.  additions. 

Until  the  non-appearance  of  cloudiness  indicates  the  end-point,  the  bottle 
should  be  agitated  after  each  addition  of  decimal  salt  solution. 

If  the  pipette  full  of  standard  solution  is  more  than  sufficient  to  precipitate  the 
silver,  or  in  case  the  end-point  has  been  run  over,  decimal  silver  solution  is  added 
in  1  cc.  portions  until  precipitation  ceases.  Decimal  salt  solution  is  then  added 
cautiously  until  the  end-point  is  reached.  Completion  of  the  titration  should 
always  be  with  the  decimal  salt  solution.  Some  confusion  in  judgment  of  the  end- 
point  may  arise,  on  account  of  the  fact  that  an  excess  of  sodium  chloride  produces 
turbidity.  The  appearance  of  the  cloud  so  produced  is  characteristic,  and  can  be 
distinguished  after  some  practice  from  that  exhibited  when  silver  is  still  in  excess. 
If  bromide  standard  and  decimal  solutions  are  used,  excess  of  the  reagent  produces 
a  turbid  film  only  after  long  standing. 

The  silver  value  in  milligrams  of  the  standard  solution,  plus  the  number  of  cc. 
of  decimal  salt  solution  which  produced  a  precipitate,  minus  the  number  of  cc. 
of  decimal  silver  solution  added,  gives  the  amount  of  silver  in  the  quantity  of  sam- 
ple weighed  out. 

The  result  calculated  to  milligrams  silver  per  gram  of  sample  is  customarily 
reported  in  the  case  of  silver  bullion  as  points  fineness. 

The  accuracy  of  the  method  is  limited  by  the  quality  of  pipette  and  the  skill  of 
the  operator.  With  a  pipette  which  delivers  accurately  an  experienced  operator 
can  speedily  make  analyses  in  which  the  error  is  only  of  the  order  of  plus  or  minus 
0.1  milligram  of  silver.  In  the  comparison  of  purity  of  samples  of  pure  silver, 
it  is  customary  to  carry  out  determinations  to  the  limit  of  the  known  accuracy 
of  the  pipette  delivery. 

NOTES.  If  the  amount  of  mercury  present  is  very  small,  addition  of  20  cc.  of  a 
saturated  solution  of  sodium  acetate  and  several  cc.  of  acetic  acid  before  introduction 
of  the  standard  salt  solution  will  prevent  precipitation  of  chloride  of  mercury.  When 
the  quantity  of  mercury  is  so  large  that  this  method  fails,  the  quantity  of  silver  weighed 
out  is  heated  several  nours  at  a  red  heat  in  a  small  covered  crucible  surrounded  by 
coarsely  powdered  charcoal  within  a  covered  crucible  of  larger  size. 

When  tin  is  known  to  be  present 1  in  the  bullion  to  the  extent  of  less  than  5%, 
2  crams  tartaric  are  added  to  the  assay  bottle  and  dissolved  with  3  or  4  cc.  hot  water. 
When  the  liquid  is  cool,  10  cc.  nitric  acid  (1.26  sp.gr.)  are  added  and  solution  of  the 
bullion  effected  by  the  action  of  acid  without  the  aid  of  heat.  Unless  prevented  from 
forming  by  addition  of  tartaric  acid,  metastannic  acid  stays  in  suspension  and  obscures 
the  end-point.  If  more  than  5%  of  tin  is  present,  such  an  amount  of  the  sample  should 
be  weighed  out  which  will  make  the  tin  content  of  the  assay  less  than  50  milligrams. 
A  weighed  amount  of  pure  silver  is  added  sufficient  to  make  the  total  silver  present  in 
the  assay  slightly  more  than  the  silver  value  of  the  standard  salt  solution  and  the 
method  of  solution  carried  out  as  described. 

No  pipette  is  of  use  in  the  practice  of  the  Gay-Lussac  method  which  shows  any 
tendency  to  spatter  at  the  beginning  or  ending,  or  yields  a  quickly  following  or  cling- 
ing drop  at  the  completion  of  discharge.  The  film  of  liquid  adherent  to  the  inner  sur- 
face of  the  body  of  a  good  pipette  will  drain  without  sign  of  rivulet  effect  and  be 
retained  by  the  capillary  of  the  discharge  tube  for  at  least  a  minute. 

Determinations  can  be  made  without  the  use  of  the  pipette  by  introducing  the 
precipitant  in  the  form  of  a  weighed  amount  of  the  standard  solution  or  of  finely 
powdered  pure  dry  salt,  after  dilution  of  the  silver  solution  to  about  125  cc.  The 
i  L.  E.  Salas,  Bull.  A.  I.  M.  E.,  63,  267.* 

*I  am  informed  by  the  author  that  this  method  is  used  at  the  Royal  Mint,  London,  for  silver  bul- 
lion containing  tin. — NOTE_BY_EDITOR. 


SILVER  383 

silver  value  of  the  salt  should  be  determined  by  carrying  out  the  operations  of 
the  method  on  pure  silver. 

Combination  Methods 

Combination  of  the  operations  of  the  Gay-Lussac  and  Volhard  methods  have 
been  devised  to  avoid  the  tediousness  incident  to  the  performance  of  the  Gay- 
Lussac  method  by  the  unexperienced.  By  the  modified  methods  the  amount  of 
sample  to  be  weighed  out  is  determined  by  preliminary  assay,  and  is  dissolved  in 
the  same  manner  as  in  the  practice  of  the  Gay-Lussac  method,  but  with  the  added 
precaution  to  decompose  nitrous  acid  in  the  silver  solution  by  gentle  boiling  when 
completion  of  the  titration  is  to  be  accomplished  by  the  Volhard  method. 

The  operation  of  the  combination  methods  consists  briefly  of  precipitation  of 
all  but  a  few  milligrams  of  silver  by  a  standard  solution  of  alkali  thiocyanate, 
chloride  or  bromide  added  from  the  Stas  pipette  and  estimation  of  the  excess  of 
silver  with  a  decimal  solution  of  thiocyanate  or  by  a  colorimetric  or  nephelometric 
method. 

The  procedure  favored  by  the  writer  is  to  use  a  standard  solution  of  potassium  bro- 
mide as  the  pipette  precipitant.  After  the  liquid  is  cleared  by  shaking,  it  is  decanted 
as  completely  as  possible  into  a  500-cc.  Erlenmeyer  flask.  The  precipitate  is  washed 
by  five  30-cc.  portions  of  water  containing  a  little  nitrous-free  nitric  acid,  each  por- 
tion being  shaken  before  decanting.  Using  the  same  amount  of  ferric  indicator  as  in 
the  check  assays,  decimal  thiocyanate  solution  is  added  until  not  a  very  deep  tint  remains 
permanent  after  vigorous  agitation.  Decinormal  silver  solution  is  then  added  until 
the  tint  is  discharged.  When  the  assay  is  sufficiently  free  of  copper  or  other  colored 
salts  to  permit  accurate  matching  of  tints,  the  decanted  liquid,  which  may  contain 
particles  of  silver  bromide  without  interference,  is  titrated  with  decimal  thiocyanate 
to  the  appearance  of  a  tint  which  will  match  that  of  the  check  assays.  Except  when 
colored  salts  are  present  in  such  quantity  as  to  make  recognition  of  the  point  of  bleach- 
ing of  the  ferric  thiocyanate  coloration  uncertain,  the  extreme  range  of  error  is  0.3 
part  per  1000. 

For  colorimetric  method,  see  Smith,  I.M.M  Bull.  No.  28.  Determination  of  the 
residual  silver  in  the  filtrate  from  the  thoroughly  washed  silver  bromide  precipitate  is 
practicable  by  use  of  a  suitable  nephelometric  apparatus.1 

Denige's  Cyanide  Method 2 

Silver  which  has  been  precipitated  as  chloride  may  be  determined  volumetric- 
ally  by  dissolving  the  precipitate  with  a  measured  quantity  of  a  standard  solution 
of  potassium  cyanide  of  about  decinormal  strength. 

AgCl+2KCN  =KAg(CN)2+KCl. 

Potassium  iodide  is  then  added  and  the  excess  of  standard  potassium  cyanide 
solution  determined  by  addition  of  potassium  iodide  and  titration  to  the  first  ap- 
pearance of  a  permanent  precipitate  with  decimormal  silver  nitrate. 

AgN03+KI  =AgI+KN03;  AgI+2KCN  =KAg(CN)2+KI. 

NOTES.  If  the  last  portion  of  the  precipitate  of  silver  chloride  dissolves  with  diffi- 
culty in  the  potassium  cyanide,  the  liquid  may  be  decanted  into  another  beaker  and 
solution  completed  with  ammonia.  The  solutions  are  combined. 

1  Richards  and  Wells,  Am.  Chem.  J.,  235,  1903;  Richards,  ibid.,  510,  1906:  Rich- 
ards, Com.  8th  Int.  Cong.  Ap.  Chem.,  Sec.  1,  423. 

2  Clennell,  "  The  Cyanide  Handbook,"  433. 


384  SILVER 

Extreme  sensitiveness  is  claimed  for  the  method  if  centinormal  solutions  be 
used  and  the  opalescence  indicating  the  end-point  be  detected  by  a  beam  of  light  across 
the  liquid. 

Miscellaneous  Volumetric  Methods 

Silver  may  be  determined  by  addition  from  a  burette  of  a  portion  of  a  known 
volume  of  its  neutral  or  slightly  acid  solution  to  a  standard  solution  of  sodium 
chloride  which  contains  a  little  potassium  chromate  or  bichromate  and  sufficient 
chlorine-free  magnesium  oxide  emulsion  to  neutralize  free  acid.  The  end-point 
is  indicated  by  the  formation  of  a  reddish  or  brown  precipitate. 

By  Pisani's  Method  1  a  standard  solution  of  iodide  of  starch  is  added  to  a  very 
dilute  neutral  solution  of  nitrate  of  silver  until  the  fluid  becomes  permanently  blue. 

By  Vogel's  Modification  of  Pisani's  Method,2  the  silver  solution,  which  may 
contain  free  acid,  is  titrated  with  standard  starch  iodide  solution  after  addition  of 
nitric  acid  containing  nitrous  acid. 

By  Andrews'  Modification,3  the  standard  solution  of  starch  iodide  is  added  to 
a  solution  of  silver  nitrate  which  contains  so  much  ferrous  nitrate  or  sulphate  that 
iron  will  be  in  excess  of  the  silver  present. 

2AgN03+2Fe(N03)2+I2=2AgI+2Fe(N03)3 

By  Gooch  and  Bosworth's  Method,4  silver  is  determined  by  precipitating  with 
an  excess  of  potassium  chromate,  dissolving  the  precipitate  in  ammonia,  repre- 
cipitating  by  boiling  to  low  volume  and  determining  iodometrically  either  the 
chromate  ion  combined  with  the  silver,  or  that  remaining  after  precipitating  the 
silver  with  a  known  amount  of  standard  potassium  chromate.5 

Nephelometric  Method 

This  method  is  practicable  for  the  determination  of  a  small  concentration  of 
silver  in  a  clear  and  colorless  liquid.  Less  than  2  milligram 3  of  silver  can  be  esti- 
mated with  considerable  accuracy  by  matching  the  opalescence  produced  by  a  drop 
of  hydrochloric  acid  with  that  from  a  known  quantity  in  a  liquid  of  the  same  volume, 
depth  and  temperature.  Intensity  of  opalescence  attains  the  maximum  in  about 
five  minutes  after  precipitation.  Standard  silver  solution  is  made  by  dissolving 
500  mill-'g  -ams  standard  silver  (see  Preparation  at  close  of  chapter)  with  several  cc. 
of  dilute  nitric  in  a  liter  flask  and  making  the  solution  up  to  the  mark.  For  most 
technical  determinations  the  apparatus  may  consist  of  clear  glass  cylinders  (color 
tubes)  of  suitable  size.  More  accuracy  can  be  arrived  at  by  use  of  a  nephelometer 
of  refined  construction,  for  example6  the  combination  of  a  projection  lantern 
and  a  Duboscq  colorimeter. 

Preparation  of  Pure  Silver.  The  volumetric  methods  used  for  the  determination 
of  high  percentages  of  silver,  employ  solutions  which  should  be  standardized  by  metal 
of  the  highest  purity.  For  the  preparation  of  this  metal,  the  electrolytic  method  as 
described  below  is  preferred  by  laboratories  which  are  suitably  equipped. 

1  Robiere,  Bull.  Soc.  Chim.,  17,  306,  1915;  J.  S.  C.  I.,  Oct.  30,  1915,  1073. 

2  Fresenius,  "  Quantitative  Analysis." 

3  Zeit.  fur  Anorg.  Chem.,  26,  175. 

4  Am.  J.  Sci.,  27,  302. 

6  Am.  Chem.  Soc.  Chem.  Abs.,  Aug.  10,  1909,  1735. 

6  Wells,  Am.  Chem.  J.,  35,  99,  508;  Richards,  Am.  Chem.  J.,  35,  510;  Dienert,  Compt. 
rend.,  158,  1117. 


SILVER  385 

For  the  manufacture  of  a  large  quantity — several  pounds — a  basket-like  support 
for  the  anode  is  made  of  several  glass  rods  bent  so  that  they  will  hang  from  the  rim  of 
a  tall  1000-cc.  or  larger  beaker  or  battery  jar  and  dip  into  the  receptacle  about  an  inch. 

Smaller  anodes  may  be  supported  by  the  positive  wire  or  by  a  cloth  bag  fixed  in 
place  by  "a  string  under  the  flare  of  the  rim  of  the  beaker.  In  any  arrangement  for  the 
support  of  the  anode,  allowance  of  room  should  be  made  for  the  introduction  and 
free  movement  of  an  L-shaped  stirring  rod. 

The  cathode  may  consist  of  sheet  silver  or  of  platinum  foil,  and  lies  flat  on  the  bot- 
tom of  the  beaker.  The  immersed  length  of  the  silver  or  platinum  wire  leading  from 
the  cathode  should  be  covered  with  rubber  tubing. 

Commercial  silver,  usually  about  999  fine,  may  be  used  for  the  anode,  but  by  retreat- 
ment  of  the  deposit,  very  impure  silver  may  be  used,  providing  that  the  quantity 
of  tellurium  present  is  very  low.  The  presence  of  tellurium  will  exhibit  itself  in  the 
impossibility  of  obtaining  the  desired  coarsely  crystalline  deposit. 

Tellurium  in  moderate  quantities  may  be  removed  by  melting  the  silver  in  a  crucible 
or  scorifier,  adding  niter,  permitting  the  silver  to  nearly  freeze,  raising  the  temperature 
and  pouring  into  a  hot  crucible  or  scorifier  in  which  the  operation  is  repeated,  preferably 
in  a  muffle  furnace,  until  the  surface  of  the  silver  is  without  streaks  or  spots  when  cooled 
to  near  freezing.  An  oxidizing  atmosphere  about  the  molten  metal  should  be  main- 
tained. On  the  basis  of  172  grams  silver  per  cubic  inch  an  anode  mould  for  any  con- 
venient amount  of  silver  may  be  shaped  from  4-in.  pieces  of  1-in.  square  rod  on  a  smooth 
iron  plate.  Just  before  the  anode  bar  sets  in  the  mould,  a  silver  terminal  strip  or  wire 
is  plunged  into  it. 

After  coating  the  contact  wire  or  strip  and  the  surface  of  the  anode  about  it  with 
sealing  wax,  the  anode  is  wrapped  with  filter  paper,  held  firmly  in  place  by  string  or 
rubber  bands.  If  the  anode  weighs  half  a  pound  or  more,  the  anode  is  also  wrapped 
with  cotton  flannel  which  has  been  washed  with  water  until  free  of  chloride.  A  porous 
dish,  cylinder  or  filter  cone  can  be  used  instead  of  filter  paper  and  cloth. 

The  electrolyte  contains  about  4%  of  C.P.  silver  nitrate  and  half  a  per  cent  of  chlor- 
ine-free nitric  acid  in  distilled  water,  and  fills  the  beaker  or  jar  so  it  wets  only  the  lower 
surface  of  the  anode. 

The  current,  of  about  0.1  ampere  per  square  inch  of  cathode  surface  at  the  start, 
is  raised  after  deposition  has  proceeded  for  a  few  minutes  to  the  limit  at  which  a  coarsely 
crystalline  deposit  can  be  maintained. 

Inasmuch  as  the  electrolysis  proceeds  at  a  rate  of  4  grams  per  ampere  hour,  some 
attention  is  required  to  break  up  short  circuits  and  to  pack  down  the  rather  bulky 
deposit.  The  deposit,  if  coarse,  can  be  washed  very  easily  free  of  electrolyte,  and  after 
heating  to  near  redness  is  in  the  form  preferred  for  use  by  many  assayers. 

Other  methods  which  may  be  employed  consist  of  dissolving  the  crude  silver  with 
nitric  acid  about  1.20  sp.gr.  or  with  hot  concentrated  sulphuric  acid,  if  platinum  is  pres- 
ent, separating  the  gold  and  platinum  by  filtration,  precipitating  AgCl  with  not  too 
large  an  excess  of  HC1,  stirring  the  precipitate  until  it  coagulates,  washing  repeatedly 
with  hot  water  until  a  washing  is  obtained  which  shows  no  precipitate  with  H2S, 
reducing  the  silver  chloride  by  contact  with  pure  zinc,  wrought  iron  or  the  silver  ter- 
minal of  a  carbon-silver  couple  aluminum  foil,  and  washing  with  hot  dilute  HC1  until 
a  test  of  the  decanted  liquid  indicates  absence  of  the  precipitating  element.  The 
dried  silver,  mixed  with  about  1%  of  dry  sodium  carbonate,  is  packed  into  a  clay 
crucible,  the  inside  of  which  has  been  glazed  with  borax  glass  and  covered  with  a 
layer  of  crushed  charcoal. 

The  sodium  carbonate  is  omitted  in  case  it  is  desired  to  melt  silver  refined  by 
electrolysis. 

The  silver  melted  in  the  tightly  covered  crucible  is  poured  into  an  iron  mould  which 
has  been  chalked  or  black  leaded. 

By  Knorr's  method,1  a  solution  of  silver  nitrate  from  which  excess  of  nitric  acid  has 
been  removed  by  evaporation  is  freed  of  metallic  impurities  by  adding  enough  sodium 
carbonate  to  precipitate  one-tenth  of  the  silver,  boiling  and  filtering.  The  silver  in  the 
filtrate  is  precipitated  by  sodium  carbonate  and  the  precipitate  decomposed  without 
addition  of  reducing  reagent,  by  melting  in  a  crucible.  Excess  sodium  carbonate 
carried  down  with  the  precipitate  of  silver  carbonate  will  cover  the  fusion  and  such  as 
adheres  tightly  to  the  metal  is  readily  removed  by  hydrochloric  acid.  The  metal 
should  be  smelted  under  charcoal. 

i  Liddell,  "  Metallurgists  and  Chemists'  Handbook." 


386  SILVER 

If  tne  cover  of  the  charcoal  is  omitted  or  burned  away  during  the  fusion,  the  molten 
metal  is  capable  of  absorbing  oxygen  from  the  atmosphere  to  the  extent  of  about  0  25% 
of  its  weight.  This  gas  is  expelled  during  the  passage  of  the  metal  into  the  solid  state 
and  produces  a  casting  which  cannot  be  rolled  into  smooth  sheets 

The  most  convenient  size  and  shape  of  castings  for  rolling  is  but  little  larger  than  a 
lead  pencil.  Before  rolling,  the  casting  is  cleaned  of  particles  of  the  mould  wash  After 
rolling  to  about  cardboard  thickness,  the  sheets  may  be  cut  up  into  strips  of  convenient 
size  and  length,  then  digested  with  dilute  hydrochloric  acid  (1  to  5  of  water)  washed 
with  ammonia  and  finally  with  pure  water. 

The  silver  then  should  be  dried  and  annealed  by  heating  to  redness.  It  is  best 
preserved  in  a  glass-stoppered,  salt-mouth  bottle  and  should  be  exposed  to  laboratory 
atmosphere  as  little  as  possible. 

The  purity  of  each  batch  of  silver  made  should  be  compared  by  use  of  the  Gay-Lussac 
method  with  standard  silver,  the  purity  of  which  has  been  determined  by  analysis  of 
a  50-  or  100-gm.  portion  for  Se  and  Te,  As,  Sb,  Pb,  Cu,  Au,  and  the  element  employed 
in  reducing  silver  chloride,  if  the  reduction  method  was  followed  in  the  manufacture 
of  the  metal. 


STRONTIUM 

WILFRED  W.  SCOTT 
Sr",  at.wt.  87.63;  sp.gr.  2.54;  m.p.  900°  C;  oxides  SrO  and  SrO,. 

DETECTION 

Strontium  is  precipitated  with  barium  and  calcium,  in  the  nitrate,  from  the 
ammonium  sulphide  group,  by  addition  of  ammonium  carbonate  to  the  ammo- 
niacal  solution.  The  precipitate  is  dissolved  in  acetic  acid  and  treated  with  potas- 
tassium  dichromate,  and  the  barium  filtered  off  as  BaCr04.  Strontium  and  cal- 
cium in  the  filtrate  are  separated  from  the  excess  of  potassium  chromate  by 
reprecipitation  as  carbonates  by  the  addition  of  ammonium  carbonate,  the 
precipitate  again  dissolved  in  acetic  acid  and  the  excess  of  free  acid  neutralized 
with  ammonia.  Strontium  may  now  be  precipitated  from  the  concentrated  solu- 
tion by  boiling  with  an  equal  volume  of  a  saturated  solution  of  calcium  sulphate. 

Sodium  Sulphate  Test.  A  saturated  solution  of  the  salt  added  to  a  solution 
containing  strontium  chloride,  made  strongly  acid  with  acetic  acid,  and  the 
mixture  boiled,  will  produce  a  distinct  precipitate  if  strontium  exceeds  0.0015 
normal.  Calcium  does  not  precipitate  until  1.3  normality  is  reached.1 

Flame  Test.  Strontium,  preferably  in  the  form  of  the  chloride  in  a  hydro- 
chloric acid  solution,  placed  on  a  platinum  loop  and  held  in  a  colorless  flame, 
colors  the  flame  crimson.  (Lithium  gives  a  red  color,  calcium  a  yellowish-red.) 
The  test  is  best  confirmed  by  means  of  the  spectroscope. 

The  Spectra  of  Strontium.  Eight  bright  bands;  6  are  red,  1  orange,  1  blue. 
Two  of  these,  known  as  strontium  /3  and  y,  are  red,  the  orange  is  strontium  a  and 
the  blue  strontium  6.  The  delicacy  of  the  test  is  0.6  milligram  Sr  per  cc.  The 
test  is  very  much  more  delicate  with  the  arc  spectra,  e.g.,  0.03  milligram  Sr  per 
cc.  See  chapter  on  barium,  Preliminary  Tests  under  Separations. 

ESTIMATION 

Strontium  never  occurs  free  in  nature.  It  is  found  principally  in  the  ores 
celestine,  SrS04,  and  strontianite,  SrC03.  It  generally  accompanies  calcium 
in  the  various  forms  of  calcite  and  aragonite.  It  occurs  with  barium  in  bary- 
tocelestine,  and  is  found  in  barytes.  It  also  occurs  associated  with  barium  as 
a  silicate  in  brewsterite,  Al203-H4(BaSr)03 -(SiC^o-SH^O.  It  is  found  in  traces 
in  certain  mineral  waters  and  in  sea-water. 

The  compounds  of  strontium  are  used  for  medicinal  purposes;  for  red  fire  in 
pyrotechnics;  for  the  manufacture  of  iridescent  glass;  the  dioxide  for  bleaching 
purposes;  the  sulphide  for  luminous  paint;  the  hydroxide  for  refining  of  beet- 
root sugar,  being  preferable  to  lime,  as  the  saccharate  of  strontia  is  more  granular. 

1 J.  D.  Hinds,  Jour.  Am.  Chem.  Soc.,  36,  301,  1911. 
387 


388  STRONTIUM 


Preparation  and  Solution  of  the  Sample 

The  following  facts  regarding  solubility  may  be  of  value  in  the  determination  of 
strontium.  100  cc.  of  water  dissolves  1.74  grams  Sr(OH)2-H2O  at  20°  C.  The 
hydroxide  is  less  soluble  than  that  of  barium.  The  peroxide  dissolves  to  the 
extent  of  only  0.008  gram  per  100  cc.  20°  C.  One  hundred  cc.  of  water  dissolves 
0.0011  gram  l  SrC03  (18°);  0.0114  gram  SrS04  at  18°  and  0.0104  at  100°;  the 
presence  of  sulphuric  acid  decreases  this  solubility,  i.e.,  0.00083  gram  SrS04; 
0.0051  gram  SrC204-H2O  at  18°  and  5  grams  at  100°  C.;  the  presence  of  oxalic 
acid  decreases  this  solubility.  The  sulphate  dissolves  in  concentrated  sulphuric 
acid,  and  is  appreciably  soluble  in  HC1,  HN03,  HC2H302,  NH4C1,  NH4N03, 
NaCl,  MgCl2.  The  carbonate  and  oxalate  are  soluble  in  mineral  acids. 

The  procedure  for  the  treatment  of  ores  and  strontium  products  is  the  same 
as  those  described  for  barium  and  calcium.  We  refer  to  the  chapters  on  these 
elements  for  the  preparation  of  the  strontium  solution. 

SEPARATIONS 

Separation  of  Strontium  from  Magnesium  and  the  Alkalies.  The  pro- 
cedure is  the  same  as  the  one  given  in  detail  under  barium  for  the  separation  of 
the  alkaline  earths  from  magnesium  and  the  alkalies.  Either  the  oxalic  acid 
method  or  precipitation  of  strontium  as  a  sulphate  in  presence  of  alcohol  will 
accomplish  this  separation.  If  a  sulphate  precipitation  is  made  it  will  be  neces- 
sary to  fuse  the  sulphate  with  sodium  carbonate  to  get  it  into  solution  or  to  effect 
further  separation  from  members  of  the  ammonium  carbonate  group,  should 
these  be  present. 

Separation  of  Strontium  from  Calcium.2  Strontium  and  calcium  are  con- 
verted into  the  nitrates  and  taken  to  dryness  and  all  water  expelled  by  heating 
to  140°  C.  for  an  hour  or  more.  The  nitrates  are  now  extracted  with  equal 
parts  of  absolute  alcohol  and  anhydrous  ether  or  by  boiling  with  amyl  alcohol 
at  130°  C.  (hood).  Strontium  remains  insoluble  and  calcium  goes  into  solu- 
tion as  the  nitrate.  Strontium  nitrate  may  require  further  solution  in  water, 
evaporation  to  dryness,  heating  and  extraction  to  remove  calcium  completely, 
should  this  be  present  in  large  excess.  The  nitrate  of  strontium  is  dissolved 
in  water  and  strontium  determined  by  one  of  the  procedures  given  later.  See 
detailed  procedure  for  separation  under  Barium. 

Separation  of  Strontium  from  Barium.  The  procedure  is  given  in  detail 
under  chapter  on  Barium.  In  brief  one  of  the  following  methods  may  be  used: 
Strontium  and  barium  in  a  mixture  of  the  nitrates  are  separated  from  calcium 
by  treatment  with  ether-alcohol  mixture,  in  which  Ba(N03)2  and  Sr(N03)2  are 
insoluble.  The  nitrates  dissolved  in  water  are  separated  by  precipitating  barium 
as  BaCKX  from  a  faintly  acetic  acid  solution,  strontium  remaining  in  solution. 

If  preferred,  barium  may  be  first  removed  as  a  chromate,  strontium  and  cal- 
cium precipitated  from  an  ainmoniacal  solution  by  (NH4)2C03  as  carbonates, 
the  carbonates  converted  to  nitrates  and  Sr(N03)2  separated  from  Ca(N03)2 
in  an  ether-alcohol  solution  or  by  amyl  alcohol.  Details  of  the  separations  are 
given  under  Barium. 

irrreadweli  claims  solubility  =  0.00055,  i.e.,  1  part  SrCOs  in  18,045  parts  of  water. 
2  Advantage  may  be  taken  of  the  insolubility  of  strontium  sulphate  in  ammonium 
sulphate  in  separating  it  from  the  soluble  calcium  salt. 


STRONTIUM  389 


GRAVIMETRIC  METHODS 

Strontium  may  be  conveniently  determined  either  as  the  sulphate,  the  car- 
bonate or  as  the  oxide.  The  first  procedure  is  considered  the  best  by  authorities. 

Determination  as  Strontium  Sulphate,  SrSO4 

Procedure.  A  slight  excess  of  dilute  sulphuric  acid  is  added  to  the  neutral 
solution  of  strontium,  and  then  an  equal  volume  of  alcohol.  The  mixture  is 
stirred  well  and  settled  for  several  hours,  or  overnight,  if  more  convenient.  The 
precipitate,  SrS04,  is  filtered  onto  a  small  ashless  filter  and  washed  first  with 
50%  alcohol  containing  a  little  sulphuric  acid,  then  with  alcohol  until  free  of 
acid.  The  precipitate  is  dried  and  the  paper  and  the  greater  part  of  the  salt 
ignited  separately,  then  combined  and  weighed  as  SrS04. 

Factors.    SrS04X 0.477  =  Sr,     or     X 0.8037  =SrC03,     or     X0.5642=SrO. 

Determination  as  Strontium  Carbonate 

Strontium  carbonate  is  not  readily  decomposed  by  ignition  as  is  calcium 
carbonate,  so  that  its  determination  in  this  form  may  be  satisfactorily  made. 

Procedure.  The  carbonate  is  precipitated  by  adding  ammonium  carbonate 
in  slight  excess x  to  the  ammoniacal  solution  of  strontium,  heated  nearly  to  boiling. 
The  solution  is  allowed  to  stand  for  several  hours  and  filtered  cold.  The  washed 
strontium  carbonate  and  filter  are  ignited  gently  and  the  cooled  residue  weighed 
as  SrC03. 

Factors.    SrC03X0.5935=Sr,     or     X  1.2443  =SrS04,     or     X0.702=SrO. 

Determination  as  Oxide,  SrO 

Strontium  is  precipitated  as  the  oxalate  by  addition  of  ammonium  oxalate 
to  the  slightly  ammoniacal  solution.  The  precipitate  is  filtered  and  washed  with 
water  containing  ammonium  oxalate.  The  residue  is  ignited  and  weighed  as 
SrO. 

Factors.    SrO  X  0.8456  =Sr,     or     Xl.7726=SrS04,     or     X  1.4245  =SrC03. 


VOLUMETRIC  METHODS 

The  volumetric  methods  for  determining  strontium  presuppose  its  isolation 
from  other  elements. 

Alkalimetric  Method,  Titration  with  Standard  Acids 

Either  the  carbonate  or  the  oxide  of  strontium  may  be  titrated  with  standard 
hydrochloric  or  nitric  acids.  The  compound  is  treated  with  a  known  amount 
of  standard  acid  added  in  excess,  using  methyl  orange  indicator.  The  solution 
is  heated  below  boiling  to  complete  the  reaction  and,  upon  cooling,  the  excess  of 
acid  is  titrated  with  standard  alkali. 

One  cc.  normal  acid  =0.04381  gramSr,  or  0.05181  gram  SrO,  or  0.07381  gramSrC03. 
1 N.  B.    Avoid  a  large  excess  of  (NH4)2COS.     NH4C1  has  a  solvent  action  on  SrCOi. 


390  STRONTIUM 


Titration  of  the  Chloride  with  Silver  Nitrate 

Strontium  chloride,  free  from  other  chlorides,  may  be  determined  indirectly 
by  titration  of  its  combined  chlorine  with  silver  nitrate  by  Mohr's  method,  using 
potassium  chromate  indicator.  One  cc.  N.  AgN03=  0.04381  gram  Sr. 

The  oxide  or  carbonate  is  slightly  supersaturated  with  hydrochloric,  then 
taken  to  dryness  and  heated  at  120°  C.  in  the  air  bath  to  expel  the  excess  of  acid. 
Chlorine  is  determined  on  an  aliquot  portion. 


SULPHUR 

WILFRED  W.  SCOTT 

S,  at.wt.  33.07;    sp.gr.  3.035;    m.p.  111°;    b.p.  444.53°;   oxides  S2O3,  SO2, 
SO3,  S2O7;  principal  acids  H2S2O4,  H2SO3,  H2SO4,  H2S2O3,  and  H2S2O'8. 

DETECTION 

The  following  tests  include  the  detection  of  free  sulphur  and  its  more  important 
combined  forms. 

Element.  Sulphur  is  a  polymorphous,  yellow,  brittle,  odorless  and  tasteless 
solid;  existing  in  the  rhombic,  monoclinic  and  triclinic  crystalline  forms,  and 
also  in  an  amorphous  state.  At  111°  r  it  melts  to  a  pale  yellow  liquid;  at  180° 
it  thickens  to  a  dark  gum-like  material,  containing  a  large  percentage  of  amor- 
phous sulphur;  at  260°  it  becomes  a  liquid  again,  and  at  444.53°  it  boils,  giving 
off  a  brownish-red  vapor. 

Heated  in  the  air  sulphur  burns  with  a  blue  flame,  and  is  oxidized  to  S02,  a 
gas  with  a  characteristic  pungent  odor.  This  gas  passed  into  a  solution  of 
potassium  permanganate  will  decolorize  it,  if  S02  is  in  excess  of  the  amount  that 
will  react  with  the  KMn04  in  the  solution. 

If  sulphur  is  dissolved  in  a  hot  alkali  solution  and  a  drop  of  this  then  placed 
on  a  silver  coin,  a  stain  of  black  Ag2S  will  be  evident,  due  to  the  action  of  the 
sulphur. 

Sulphides.  Hydrogen  sulphide,  H2S,  is  liberated  when  a  sulphide  is  treated 
with  a  mineral  acid.  This  gas  blackens  moist  lead  acetate  paper.  H2S  has  a 
very  disagreeable  odor,  which  is  characteristic. 

Sulphates.  A  white  compound,  BaSOi,  is  precipitated  in  presence  of  free 
hydrochloric  acid  when  a  solution  of  barium  chloride  is  added  to  a  solution  of 
a  sulphate. 

Insoluble  sulphates  are  decomposed  by  boiling  or  fusion  with  alkali  carbonates, 
forming  water-soluble  alkali  sulphates. 

Sulphites.  Sulphur  dioxide,  S02,  is  evolved  when  a  sulphite  is  treated  with 
hydrochloric  acid.  The  odor  of  the  gas  is  characteristic. 

Sulphur  dioxide  decolorizes  a  solution  of  potassium  permanganate.  (Use 
very  dilute  solution.) 

Sulphites  are  distinguished  from  sulphates  by  their  failure  to  form  a  white 
precipitate,  when  barium  chloride  is  added  to  the  solution  acidified  with  hydro- 
chloric acid;  also  by  the  fact  that  H2S  is  formed  when  zinc  is  added  to  a  solu- 
tion of  a  sulphite,  acidified  by  hydrochloric  acid. 

Thiosulphates.  Sulphur  dioxide  is  evolved  and  free  sulphur  precipitated 
when  a  thiosulphate  is  acidified  with  dilute  mineral  acids.  In  presence  of 
oxidizing  agents  sulphides  will  also  liberate  free  sulphur. 

Thiosulphates  are  strong  reducing  agents. 

1U.  S.  Bureau  of  Standards  gives  the  following  melting-points:  Si=  112.8°,  82=  119.2, 
S8=  106.8.  Circular  35  (2d  Ed.) . 

391 


392  SULPHUE 


ESTIMATION 

The  determination  of  sulphur  may  be  required  in  a  great  variety  of  substances, 
minerals,  rocks,  sulphur  ores,  acids,  salts,  water,  gas,  coal  and  other  organic 
matter. 

The  substance  occurs  in  nature  principally  in  the  following  forms: 

Element.  Found  free,  generally  mixed  with  earthy  matter.  The  commer- 
cial product  is  exceedingly  pure  and  may  contain  over  99.5%  S. 

Sulphur  Dioxide.  The  gas,  together  with  free  sulphur,  is  found  in  volcanic 
regions. 

Hydrogen  Sulphide.  Occurs  in  mineral  waters  and  in  the  air,  from  decaying 
organic  matter. 

Sulphide  Ores.  Iron  pyrite,  FeS2  (30  to  50%  S) ;  ferro  ferric  sulphide, 
Fe203-5FeS;  pyrrhotite,  Fe7S8;  copper  pyrites,  CuFeS2;  realgar,  As2S2;  orpi- 
ment,  As2S3;  galena,  PbS;  cinnabar,  HgS;  zinc  blende,  ZnS. 

Sulphate  Ores.  Gypsum,  CaS04  •  2H20,  very  abundant;  barytes,  or  heavy 
spar,  BaS04;  celestite,  SrS04;  kieserite,  MgS04-H20;  bitter  spar  or  Epsom 
salts,  MgS04-7H20;  Glauber  salt,  Na2S04-10H20;  sulphates  of  alkalies  hi  animal 
and  plant  fluids. 

The  gravimetric  determination  of  sulphur,  by  procedures  of  technical  impor- 
tance, depends  upon  its  precipitation  as  barium  sulphate,  BaS04,  after  converting 
it  into  sulphuric  acid,  or  a  soluble  sulphate,  if  not  already  in  this  form.  Oxida- 
tion of  free  sulphur,  sulphides,  sulphites,  metabisulphites,  thiosulphates  may  be 
accomplished  by  either  dry  or  by  wet  methods,  details  of  which  are  given  under 
subsequent  procedures.  When  present  as  a  sulphide,  or  having  been  converted 
to  this  form,  the  substance  may  be  evolved  as  hydrogen  sulphide,  the  gas  absorbed 
by  a  suitable  agent,  and  after  oxidation  it  may  be  determined  by  precipitation  as 
BaS04  and  thus  weighed. 

The  volumetric  methods  of  determining  sulphur  depend  upon  titration  with 
oxidizing  agents,  or  by  acids,  or  by  alkalies,  according  to  the  form  of  the  sulphur 
compound,  or  by  means  of  a  substance  forming  an  insoluble  compound  with  sul- 
phuric acid.  For  example  sulphides  are  treated  with  a  strong  mineral  acid  (HC1), 
the  evolved  H2S  absorbed  in  a  suitable  reagent,  and  the  sulphide  formed  is 
titrated  with  standard  iodine.  Sulphites  may  be  determined  either  by  oxida- 
tion with  iodine  or  by  titration  with  an  acid  in  presence  of  methyl  orange.  Acid 
sulphites  or  metabisulphites  may  be  determined  by  the  iodine  titration  or  by 
titration  with  an  alkali  in  presence  of  phenolphthalein.  Thiosulphates  are 
titrated  with  iodine.  Soluble  sulphates  may  be  titrated  with  standard  barium 
chloride  or  chromate,  added  in  slight  excess,  and  the  excess  estimated  by 
titration. 

Standard  procedures  are  given,  covering  the  more  important  forms  which 
commonly  concern  the  analyst. 

Preparation  and  Solution  of  the  Sample 

In  the  preparation  of  the  sample  the  following  facts  regarding  solubility  of 
sulphur  and  its  combination  should  be  kept  in  mind. 

Element.  The  crystalline  forms  are  soluble  in  CS2,  the  monoclinic  form 
is  soluble  also  in  alcohol,  chloroform  and  benzol.  Yellow  amorphous  and 
plastic  sulphur  are  insoluble  in  CS2.  Sulphur  precipitated  by  the  action  of  HC1 


SULPHUR  393 

upon  (NH4)2Sa;  is  soluble  in  benzol.  The  element  is  soluble  in  hot  hydrates  of 
sodium,  potassium,  barium  and  calcium,  forming  polysulphides  and  thiosulphates. 

Sulphide.  Sulphides  of  Na,  K,  Cs,  Rb,  Ca,  Sr,  Ba,  Mg,  Mn,  Fe  are  soluble 
hi  dilute  mineral  acids.  The  sulphides  of  Ag,  Hg,  Pb,  Cu,  Bi,  Cd,  Co,  Ni 
require  strong  acids  for  decomposition.  These  are  also  insoluble  in  sodium 
hydroxide  and  potassium  hydroxide  solutions.  As,  Sb  and  Sn  sulphides  are 
insoluble  in  dilute  acids,  but  soluble  in  alkalies. 

Sulphate.  With  exception  of  BaS04,  CaS04,  SrS04  and  PbS04,  sulphates 
are  soluble  in  water. 

Thiosulphate.    Nearly  all  are  soluble  in  water. 

Sulphite.  With  exception  of  the  sulphites  of  the  alkalies,  sulphites  of  the 
metals  are  difficultly  soluble  in  water,  but  readily  decomposed  by  acids. 

Decomposition  of  Sulphur  Ores 

The  wet  procedure  for  oxidation  and  decomposition  of  sulphur  ores  is  given 
hi  detail  under  the  Gravimetric  Methods,  page  396.  This  process  is  used  for  the 
valuation  of  the  ore,  and  is  applicable  to  a  wide  range  of  substances. 

Fusion  Method.  One  gram  of  the  finely  ground  ore  (80  mesh)  is  intimately 
mixed  with  6  grams  of  zinc  oxide-sodium  carbonate  mixture  (4  parts  ZnO+l 
part  Na2C03),  placing  2  grams  more  of  the  mixture  over  the  charge.  The  material 
is  fused  and  sulphur  extracted  according  to  the  procedure  described  for  coal — 
Eschka's  method. 

Sulphur  in  Coal,  Eschka's  Method 

One  gram  of  coal  is  intimately  mixed  with  3  grams  of  Eschka's  compound, 
consisting  of  2  parts  of  porous,  calcined  magnesia  and  1  part  of  anhydrous  sodium 
carbonate.  The  mixture,  placed  in  a  platinum  crucible,  is  covered  with  about 
2  grams  more  of  Eschka's  compound.  The  charge  is  placed  in  an  open  platinum 
crucible,  which  is  protected  from  the  flame  by  a  shield,  as  shown  in  Fig.  65.  If 
possible,  a  sulphur-free  flame  should  be  used  to  avoid  contaminating  the  material. 
With  proper  precautions,  the  shield  will  prevent  this.  Heating  in  a  crucible 
electric  furnace  completely  avoids  sulphur  contamination.  The  mixture  is 
heated  very  gradually,  to  drive  off  the  volatile  matter,  the  charge  being  stirred 
frequently  with  a  platinum  wire  to  allow  free  access  of  air.  The  heat  is 
increased,  after  half  an  hour,  to  a  dull  redness.  When  the  carbon  has  burned  out, 
the  gray  color  having  changed  to  a  yellow  or  light  brown,  the  heat  is  removed 
and  the  crucible  cooled. 

The  powdered  fusion  is  digested  with  100  cc.  of  hot  water  for  half  an  hour, 
and  the  clear  liquor  decanted  through  a  filter  into  a  beaker.  The  residue  is 
washed  twice  more  with  hot  water,  by  decantation,  and  finally  on  the  filter, 
until  the  volume  of  the  total  filtrate  amounts  to  about  200  cc.  About  5  cc.  of 
bromine  and  a  little  hydrochloric  acid  are  added,  and  the  solution  boiled.  Sul- 
phuric acid  is  now  precipitated  as  BaS04  by  addition  of  barium  chloride  to  the 
hot  solution,  and  sulphur  determined  by  the  first  of  the  gravimetric  procedures. 

Sulphur  in  Rocks,  Silicates,  and  Insoluble  Sulphates 

The  material  in  finely  powdered  form  is  fused  in  a  large  platinum  crucible 
with  about  six  times  its  weight  of  sodium  carbonate  (sulphur  free)  mixed  with 
about  0.5  gram  of  potassium  nitrate.  The  charge  is  protected  from  the  flame 


394  SULPHUR 

by  an  asbestos  board  or  silica  plate  with  an  opening  to  accommodate  the  cru- 
cible snugly,  as  shown  in  Fig.  65.  The  fusion  is  extracted  with  water,  the  filtrate 
evaporated  to  dryness  and  silica  dehydrated.  The  residue  is  moistened  with 
strong  hydrochloric  acid,  then  taken  up  with  a  little  water,  boiled  free  of  C02, 
and  silica  filtered  off.  The  filtrate  contains  the  sulphate,  which  is  now  precipi- 
tated as  barium  sulphate  according  to  one  of  the  standard  procedures. 

Barium  Sulphate.  This  is  transposed  by  fusion  with  sodium  carbonate, 
as  stated  above.  Barium  carbonate  remains  in  the  water-insoluble  residue.  It 
is  advisable  to  wash  the  residue  in  this  case  with  hot  sodium  carbonate  solution,  to 
insure  complete  removal  of  the  sodium  sulphate.  The  filtrate  is  acidified  with 
HC1,  boiled  free  of  C02  and  BaS04,  then  precipitated. 

Lead  Sulphate.  This  may  be  transposed  by  digesting  the  compound  with 
a  strong  solution  of  sodium  carbonate  saturated  with  C02,  keeping  the  solution 
at  boiling  temperature  for  half  an  hour  or  more.  The  sulphate  will  be  in  solution 
and  the  lead  is  precipitated  as  the  water-insoluble  carbonate. 

Strontium  or  calcium  sulphates  may  be  transposed  by  the  procedure  described 
for  lead. 


SEPARATIONS 

Substances  Containing  Iron 

In  precipitating  barium  sulphate,  in  presence  of  ferric  salts,  from  hot  solu- 
tions by  the  gravimetric  procedure  commonly  followed,  considerable  iron  is 
carried  down  by  the  precipitate.  Since  Fe2(S04)3  loses  S03  upon  ignition,  and 
since  Fe203  weighs  much  less  than  BaS04,  low  results  will  be  obtained.  Hence 
the  removal  of  iron  is  necessary,  or  a  method  should  be  followed  in  which  iron 
does  not  interfere.  It  is  found  that  barium  sulphate  precipitated  from  a  large 
volume  of  cold  solution,  in  which  the  iron  has  been  reduced  to  ferrous  condition, 
is  free  from  iron.  Details  of  this  procedure  are  given  in  the  second  of  the  gravi- 
metric methods,  page  396. 

If  sulphur  is  to  be  precipitated  from  hot  solution  of  comparatively  small 
volume  (200  to  400  cc.),  it  is  necessary  to  remove  iron.  This  is  accomplished 
by  precipitating  this  as  Fe(OH)3  by  addition  of  ammonium  hydroxide  in  decided 
excess  (5  to  10  cc.  excess  of  strong  NH4OH,  sp.gr.  0.90).  If  the  solution  is 
barely  neutralized  with  ammonia,  the  iron  hydroxide  carries  down  considerable 
of  the  sulphate.  Even  with  the  precaution  recommended  some  of  the  combined 
sulphuric  acid  is  occluded  by  the  precipitate,  so  that  it  is  necessary  to  recover 
this  by  dissolving  the  precipitate  with  hydrochloric  acid  and  reprecipitating  the 
ferric  hydroxide  with  an  excess  of  ammonia.  The  combined  filtrates  are  now 
treated  with  barium  chloride,  upon  acidification  with  hydrochloric  acid,  accord- 
ing to  the  procedure  first  given,  page  395,  and  the  sulphate  determined. 

Separation  of  Sulphur  from  Metals  Forming  an  Insoluble  Sulphate 

This  is  accomplished  by  fusion  of  the  compound  with  sodium  carbonate  and 
extraction  of  the  mass  with  water.  The  metal  remains  with  the  residue  and 
the  sulphate  of  the  alkali  passes  into  solution.  For  details  see  subject  under 
Preparation  and  Solution  of  the  Sample,  page  392. 


SULPHUR  395 

Nitrates  and  Chlorates.  These  are  carried  down  with  the  precipitate  as 
barium  salts  if  they  are  present  in  appreciable  amount.  They  may  be  removed 
from  the  solution  by  evaporation  to  dryness  with  hydrochloric  acid. 

Silica.  Silica  will  be  carried  down  with  the  barium  sulphate  precipitate 
if  present  in  appreciable  amounts.  It  is  removed  by  evaporation  of  the  solution 
with  hydrochloric  acid,  dehydrating  the  silicic  acid,  taking  up  with  HC1  and 
water  and  filtering. 

Ammonium  and  Alkali  Salts.  These  have  a  negligible  effect  on  the  precipi- 
tate of  BaS04  if  this  is  precipitated  from  a  large  volume,  according  to  the  second 
gravimetric  procedure. 


GRAVIMETRIC  DETERMINATION  OF  SULPHUR 
Precipitation  as  Barium  Sulphate 

Preliminary  Remarks.  The  procedure  depends  upon  the  insolubility  of 
barium  sulphate,  BaS04,  in  neutral  or  slightly  acid  solutions.  It  was  formerly 
the  general  practice  to  precipitate  the  sulphur  by  adding  a  10%  barium  chloride 
solution  to  the  hot  sulphate  solution,  which  had  been  diluted  from  200  to  400  cc., 
according  to  the  amount  of  sulphur  that  was  present  (not  over  0.2  gram  sulphur 
per  100  cc.),  containing  1  to  3  cc.  of  free  concentrated  hydrochloric  acid  per  100  cc. 
of  solution.  Special  precautions  were  given  to  have  the  solution  boiling  hot,  and  to 
avoid  having  a  volume  of  over  400  cc.,  a  smaller  sample  being  taken  in  high  sulphur 
ores,  rather  than  increase  the  volume.  Extended  experiments  have  shown  that 
it  is  preferable  to  precipitate  the  sulphate  from  a  large  volume  of  cold  solution. 
The  product  obtained  is  less  apt  to  occlude  impurities,  the  crystals  are  larger  than 
those  obtained  in  hot  concentrated  solutions,  and  do  not  pass  through  the  filter. 
Precipitation  may  be  made  in  presence  of  large  amounts  of  iron,  copper  and 
other  impurities.  The  procedure  requires  large  beakers  of  2-  to  2|-liter  capacity, 
special  precipitating  cups,  and  a  suction  apparatus,  as  shown  in  Figs.  60,  61,  62 
and  63.  This  apparatus  may  not  always  be  available,  and  occasionally  it  is 
advantageous  to  precipitate  the  sulphur  in  a  small  volume,  specially  when  the 
sulphur  content  of  the  material  is  low,  hence,  although  the  second  procedure 
is  generally  recommended,  the  older  method  is  also  included. 

I.  Precipitation  of  Barium  Sulphate  from  HotJSolutions 

Procedure.  The  sulphur  should  be  present  in  solution  either  as  free  sulphuric 
acid  or  as  a  sulphate  salt.  The  solution  is  made  acid  by  addition  of  hydrochloric 
acid  (phenolphthalein  indicator),  and  then  4  cc.  added  in  excess  (HC1,  sp.gr.  1.2). 
After  diluting  to  a  volume  of  400  cc.  with  hot  water,  the  mixture  is  heated  to  boil- 
ing, and  a  10%  solution  of  barium  chloride  added  in  a  fine  stream,1  through  a 
funnel  with  a  capillary  stem,  or  from  a  burette,  at  the  rate  of  10  cc.  in  two  to  ten 
minutes.  The  reagent  is  added  in  slight  excess  of  that  required  to  react  with  the 
sulphuric  acid  or  sulphate.  (Ten  cc.  of  10%  barium  chloride  solution  will  precip- 
itate 0.1416  gram  of  sulphur.)  The  beaker  is  placed  on  a  steam  bath  and  the  pre- 

1 E.  Hintz  and  H.  Weber  recommend  adding  100  cc.  of  N/10  BaCl2  solution,  boiling 
hot,  to  the  hot  sulphate  solution  all  at  once  in  place  of  slowly,  as  recommended  in  general 
practice.  (See  Treadwell  and  Hall,  "Analytical  Chemistry,"  2,  3d  Edition,  p.  469.) 


396  SULPHUR 

cipitate  allowed  to  settle  for  about  two  hours.  The  solution  is  filtered  through 
a  fine  grade  of  filter  paper  (B.  &  A.  grade  A,  or  S.  &  S.  grade  No.  90),  or 
through  a  tared  Gooch  crucible.  Since  the  precipitate  frequently  passes  through 
the  filter  it  is  advisable  always  to  pass  the  solution  through  the  same  filter  a 
second  time.  The  precipitate  is  washed  ten  times  with  hot  water,  then  dried, 
and  ignited  gently  over  a  Bunsen  burner,  or  in  a  muffle,  for  half  an  hour. 
(Blasting  is  not  necessary,  nor  desirable.)  The  white  BaS04  is  cooled  in  a 
desiccator,  and  then  weighed.  If  a  filter  paper  has  been  used  in  place  of  a 
Gooch  crucible,  the  ignition  is  best  made  in  a  porcelain  crucible,  with  free  access 
of  air,  the  ignited  sulphate,  upon  cooling,  is  brushed  out  of  the  crucible  and  so 
weighed. 

Factors.      BaS04X0.1373=S,    or     X  0.4202  =H2S04,    or     X0.3766=FeS, 

or   X0.2744=S02,    or    0.3430  =S03,    or     X0.4115=S04. 

NOTE.  If  much  iron  or  alumina  is  present  it  is  advisable  to  precipitate  the  sul- 
phate from  a  large  volume,  by  the  second  method,  rather  than  attempt  to  remove 
these  substances.  If  BaSO4  is  present  in  the  original  material  its  weight  should  be 
included  with  that  of  the  precipitate. 

II.  Precipitation  of  Barium  Sulphate  from  Cold  Solutions — 

Large  Volume 

Introduction.  The  method  worked  out  by  Allen  and  Bishop,  General  Chem- 
ical Company,1  is  especially  adapted  to  the  determination  of  sulphur  in  iron 
pyrites  and  materials  high  in  sulphur,  30  to  50%  sulphur,  but  by  varying  the 
amount  of  material  used  the  range  may  be  extended  from  smaller  to  greater 
amounts.  The  finely  ground  sample  is  oxidized  by  means  of  a  mixture  of  bro- 
mine and  potassium  bromide,  followed  by  nitric  acid.  The  nitric  acid  is  expelled 
by  evaporation  to  dryness,  followed  by  a  second  evaporation  with  hydrochloric 
acid,  which  dehydrates  the  silica.  Iron  is  now  reduced  to  the  ferrous  condition 
and  the  silica  and  residue,  undissolved  by  addition  of  hot  water  and  HC1,  is  filtered 
off.  The  sulphur  is  precipitated  in  a  large  volume  of  cold  solution,  by  barium 
chloride  solution,  as  BaS04  and  so  weighed. 

Reagents.  Bromine — Potassium  Bromide  Solution.  320  grams  of  potas- 
sium bromide  are  dissolved  in  just  sufficient  water  to  cause  solution  and  mixed 
with  200  cc.  of  bromine,  the  bromine  being  poured  into  the  saturated  bromide 
solution.  After  mixing  well  the  solution  is  diluted  to  2000  cc. 

Bromine — Carbon  Tetrachloride  Solution.  Carbon  tetrachloride  saturated 
with  bromine. 

Barium  Chloride,  anhydrous,  5%  solution;  or  crystals,  6%  solution. 

Procedure.  Preparation  of  Sample.  The  sample  ground  to  pass  80-mesh 
sieve  is  carefully  mixed  and  quartered  down  to  10  grams.  This  is  dried  for  one 
hour  at  100°  C.  and  then  placed  in  a  weighing  tube. 

A  factor  weight,  1.3738  grams  of  the  sample,  is  placed  in  a  deep  beaker,  300  cc. 
capacity,  2|  by  4£  ins. 

Oxidation  of  Sulphur.  Ten  cc.  of  the  bromine-potassium  bromide  mixture 
for  pyrrhotite  ore,  or  bromine — carbon  tetrachloride  reagent  for  pyrites  ores, 
are  added  and  the  beaker  covered  with  a  dry  watch-glass  cover.  After  standing 

1  Paper  before  Eighth  International  Congress  of  Applied  Chemistry:  "An  Exact 
Method  for  the  Determination  of  Sulphur  in  Pyrites  Ores,"  W.  S.  Allen  and  H.  B. 
Bishop. 


SULPHUR 


397 


Watch  Glass  Cover 
.-Glass  Rider 


FIG.  60. 


fifteen  minutes  in  the  cold  bath  (a  casserole  of  water  will  do),  with  occasional 
shaking  of  the  beaker,  15  cc.  of  strong  nitric  acid  are  added  and  the  mixture 
allowed  to  stand  fifteen  minutes  longer, 
at  room- temperature,  and  then  warmed 
on  an  asbestos  board  on  the  steam  bath 
until  the  reaction  has  apj^rently  ceased 
and  the  bromine  has  been  volatilized. 
The  beaker  is  now  placed  within  the  ring 
of  the  steam  bath  so  that  the  lower 
portion  is  exposed  to  steam  heat.  The 
solution  is  evaporated  to  dryness,  the 
cover  of  the  beaker  being  raised  above  the 
rim  by  means  of  riders  (U-shaped  glass 
rods),  Fig.  60,  10  cc.  of  strong  hydro- 
chloric acid  are  now  added  and  the  solution  again  evaporated  to  dryness  to  expel 
the  nitric  acid.  The  silica  is  dehydrated  by  heating  in  the  air  oven  at  100°  C.  for 
one  hour,  or  overnight  if  preferred. 

Reduction  of  Iron.  Four  cc.  of  hydrochloric  acid  (sp.gr.  1.20),  followed 
five  minutes  later  by  100  cc.  of  hot  water,  are  added,  the  sides  of  the  beaker  and 
the  cover  being  rinsed  into  the  solution.  The  riders  being  removed,  the  sample 
is  gently  boiled  for  five  minutes  to  insure  the  solution  of  the  sulphate.  After 
cooling  for  about  five  minutes,  approximately  0.2  gram  powdered  aluminum 
is  stirred  into  the  solution,  keeping  covered  during  the  intervals  between  stir- 
ring. When  the  iron  has  been  reduced,  the  solution  becoming  colorless,  the 
sample  is  filtered  into  a  2500-cc.  beaker,  through  a  12£  cm.  filter  paper  (S.  & 
S.  No.  590  or  B.  &  A.  No.  A).  The  beaker  should  be  copped  out  and  the 
residue  on  the  filter  washed  nine  times  with  hot  water,  filling  the  filter  funnel  and 
draining  each  time. 

Precipitation  of  the  Sulphur.  The  solution  in  the  large  beaker  is  diluted  to 
1600  cc.  with  cold  water  and  6  cc.  HC1  (sp.gr.  1.20)  added,  and  mixed  by 

stirring.  The  barium  chloride  solu- 
tion is  now  added  by  means  of  a 
special  delivering  cup  (Figs.  61  and 
62),  which  should  drain  at  the  rate 
of  5  cc.  per  minute.  125  cc.  of 
barium  chloride  solution  are  added 
for  ores  containing  30  to  50%  sul- 
phur, the  factor  weight  being  taken. 
The  solution  is  not  stirred  while 
the  barium  chloride  is  being  added, 
FIG.  62. 


Precipitation 
Cup-  ISOc.c. 


Beaker-* 
2500o.c 


FIG.  61. 
Apparatus  for  Precipitating  Sulphur. 


but  when  the  cup  has  drained,  the 
solution  is  mixed  by  stirring.     The 
BaS04  is  allowed  to  settle,  two  or 
three  hours  being  advisable,  overnight  being  preferred. 

Filtration.  The  clear  solution  is  filtered  through  a  weighed  Gooch  crucible 
(35  cc.),  using  suction.  This  is  best  done  by  the  automatic  arrangement 
shown  in  Fig.  63.  The  beaker  containing  the  solution  is  placed  on  a  shelf; 
a  siphon  dipping  to  within  half  an  inch  of  the  precipitate  at  the  bottom  of  the 
beaker  is  connected  to  the  Gooch  crucible  by  means  of  a  tightly  fitting  stopper. 
The  Gooch  and  thistle  tube  are  best  connected  by  heavy  rubber  tubing.  The 


398 


SULPHUR 


Clock  Glass  Cover 


suction  flask,  or  bottle,  should  have  a  capacity  of  about  3  liters.    A  Geissler 
stop-cock  passes  through  the  rubber  stopper  in  the  suction  flask  to  relieve  the 

pressure  when  the  Gooch  is  to  be  removed. 
The  precipitate  is  washed  onto  the  asbestos 
mat  in  the  crucible  and  washed  with  cold 
water  six  times,  the  beaker  being  copped 
, .  out  as  usual. 

Ignition.    The    precipitate  is    dried   by 
placing  the  crucible  on   an    asbestos  board 
Rubber Sto  per      over  a  ^ame  ^or  twenty-five  minutes  and 
Gooch  Crucible      then  heated  over  a  direct  flame  for  thirty 

•Stopcock  minutes. 

-•Rabbet'0"        Calculation.       BaS04X10=per  cent   S. 
u  stopper     (If  factor  weight  is  taken.) 

Factor.      BaS04X0.1374  =gram  S. 

Notes  and  Precautions 

Although  barium  sulphate  is  only  slightly 
soluble  in  water,  it  is  appreciably  soluble  in  the 
salts  of  the  alkalies  (Na,  K  and  NH4),  and  in  a 
large  excess  of  hydrochloric  acid. 

Barium  sulphate  occludes  salts,  especially 
nitrates  and  chlorides.  Ferric  chloride  is  carried 
down  with  this  precipitate,  though  ferrous  chlo- 
ride is  not;  hence  the  reduction  of  iron  is  necessary.  Occlusion  of  iron  causes  low 
results,  as  will  be  seen  from  the  fact  that  with  heating  of  Fe2(SO4)3,  SO3  is  volatilized, 
the  salt  decomposing  to  Fe2O3+SO3.  With  the  iron  reduced  the  precipitate  burns 
perfectly  white,  whereas  with  ferric  iron  present  the  precipitate  is  invariably  red  or 
yellow.  Aluminum  powder  used  by  W.  H.  Seamon,1  for  reduction  of  iron  in  determi- 
nation of  sulphur,  suggested  its  value  in  the  method  above  given. 

Potassium  bromide  is  added  to  the  bromine  mix  as  a  diluent  to  prevent  too  vigor- 
ous a  reaction.  Cooling  the  solution  is  for  the  same  purpose  as  a  loss  of  sulphur  will 
result  if  the  reaction  is  violent.  This  is  especially  the  case  in  pyrrhotite  ore. 

Otto  Folin  2  shows  that  precipitation  of  BaSO4  in  a  large  volume  of  cold  solution 
produces  large  crystals. 

Mechanical  loss  and  reduction  of  BaSO4  is  avoided  by  the  Gooch  crucible. 
The  method  has  been  thoroughly  tested  in  the  laboratories  of  the  Gen.  Chem. 
Co.  and  has  become  9,  standard  method  for  sulphur, 


FIG.  63. — Apparatus  for  Filtering 
Barium  Sulphate. 


Evolution  Method  for  Determining  Sulphur  in  Iron,  Steel,  Ores, 
Cinders,  Sulphides  and  Metallurgical  Products 

Introduction.  The  method  depends  upon  the  fact  that  hydrogen  sulphide 
is  evolved  when  a  sulphide  is  acted  upon  by  a  strong  acid  such  as  hydrochloric 
acid.  This  gas,  absorbed  by  a  suitable  reagent,  may  be  determined  gravimetri- 
cally 8  by  weighing  directly  the  precipitated  sulphide,  or  by  oxidation  of  either 
the  hydrogen  sulphide  evolved  or  the  sulphide  formed  in  the  absorbing  reagent, 

1  Chemical  Engineer,  September,  1908. 

2  Journal  of  Biological  Chem.,  1,  131-159. 

8  Gravimetrically.  (a)  Evolution  of  H2S  into  solutions  of  ZnCl2,  KOH,  KMnO4, 
AgNOs,  Hg(CN)2,  H2O2,  Br  +  HCl  and  subsequent  oxidation  to  sulphate  when 
necessary,  and  precipitation  as  BaSO4.  (6)  Absorption  of  H2S  by  neutral  or  alkalinft 
solutions  of  lead,  oxidation  of  PbS  to  PbSO4  and  weighing  as  such,  (c)  Absorption  of 
H2S  in  solutions  of  AgNO3,  CdCl2,  and  weighing  the  precipitated  sulphide. 


SULPHUR 


399 


and  precipitating  sulphur  as  BaS04.  It  may  be  determined  volumetrically  l 
by  titrating  the  precipitated  sulphide  with  iodine  or  by  titrating  the  acid,  formed 
by  the  reaction,  with  standard  caustic.  The  iodine  and  caustic  titrations  may  be 
made  on  the  same  run,  or  the  sulphide  may  be  weighed  and  the  filtrate  containing 
the  free  acid  titrated,  thus  double  checking  results.  The  following  reaction 
takes  place  when  the  gas  is  evolved  and  absorbed  by  neutral  cadmium  sulphate: 

H2S+CdS04  =  CdS  precipitate+H2S04  free  acid. 

The  method  is  especially  adapted  to  the  determination  of  sulphur  in  iron  and 
steel  or  in  metallurgical  products  containing  small  amounts  of  sulphide.  It 
may  be  applied  to  products  containing 
larger  amounts  of  sulphur  as  sulphides 
or  sulphates,  the  latter  condition  requir- 
ing a  special  preliminary  treatment. 

The  method  is  not  applicable  for 
determining  free  sulphur  or  sulphur  in 
iron  pyrites. 

Reagents.  Iodine  Solution.  Two 
strengths  of  this  reagent  should  be  at 
hand  for  general  work: 

For  iron  and  steel  and  low  sul- 
phur briquettes,  etc.  =  .01  to 
0.5%  S N/30I 

For  sulphur  products  containing 
over  0.5%  S N/10  I 

Starch  Solution.  Made  from  a 
good  grade  of  [soluble  starch,  1  gram 
per  200  cc.  of  water.  Fresh  solutions 
are  desirable,  as  the  deteriorated  material 
produces  a  greenish-brown  color  in  place 
of  the  delicate  blue  desired.  Flocks  of 
insoluble  starch  will  cause  the  same 
difficulty. 

Cadmium  Chloride  or  Cadmium 
Sulphate  Solutions.  Ammoniacal  Solu- 
tion. Fifty-five  grams  of  CdCl2-2H20 
or  70  grams  of  the  sulphate  are  dissolved 
in  500  cc.  of  distilled  water.  To  this 

are  added  1200  cc.  NH4OH  (sp.gr.  0.90)    FIG.  64.— Scott's  Apparatus  for  Determin- 
and  the   solution  diluted  to   2500   cc. 
The  solution  is  of  such  strength  that 
50  cc.   will  precipitate  approximately  0.175  gram  sulphur 
This  is  equivalent  to  about  3.5%  sulphur  on  a  5-gram  sample. 

1  Volumetrically.     (a)  Absorption  in  a  solution  of  KOH,  CdCl2  or  CdSO4,  ZnCl2 
or  ZnSO4,  Na2HAsO3  and  titration  with  iodine  solution.     (6)  Absorption  in  iodized 
KI  and  titration  of  the  excess  of  iodine  with  Na2S2O3  solution,     (c)  Absorption  in  a 
neutral  solution  of  a  metallic  salt  and  titration  of  the  liberated  acid,     (d)  Absorption 
in  caustic  alkali  and  addition  to  an  acid  solution  of  a  reducible  salt,  e.g.,  Fe2O3  and 
titration  of  the  lower  oxide,  FeO. 

2  Apparatus  designed  by  W.  W.  Scott. 


ing  Sulphur  in  Iron  and  Steel.2 

evolved    as    H2S. 


400  SULPHUR 

Neutral  Solution.  To  be  used  where  titration  with  caustic  is  desired. 
Seventy  grams  of  CdS04  are  dissolved  in  water  and  made  up  to  2500  cc.  The 
solution  should  be  neutral  to  methyl  orange,  otherwise  add  the  requisite  amount 
of  H2S04  or  NaOH  necessary,  determined  by  titration  of  an  aliquot  portion. 

Hydrochloric  Acid.  One  part  concentrated  acid  to  an  equal  volume  of  dis- 
tilled water. 

Sulphuric  Acid.  One  volume  of  concentrated  acid  to  four  volumes  of  dis- 
tilled water. 

Reducing  Mixture  for  Reduction  of  Sulphates.  Five  parts  of  NaHC03, 
2  parts  of  C.P.  aluminum  powder  and  1  part  of  pure  carbon,  best  made  by 
charring  starch.  A  blank  should  be  determined  on  this  material  and  allowance 
made  accordingly. 

Stannous  Chloride.    Ten-per  cent  solution. 

Fine  Granular  Aluminum  or  Zinc  Metal.     Sulphur  free,  20  mesh. 

Apparatus.  The  apparatus  shown  in  the  illustration,  Fig.  64,  is  the  author's  J 
modification  of  the  form  used  at  Baldwin  Locomotive  Works.  This  consists  of 
an  Erlenmeyer  flask  A  of  about  500-cc.  capacity  with  large  base.  With  material 
in  which  violent  foaming  occurs,  during  the  evolution  of  hydrogen  sulphide,  it 
is  advisable  to  use  a  wash  bottle  with  large  base,  in  preference  to  an  Erlenmeyer 
flask.  Through  a  rubber  stopper  is  inserted  a  thistle  tube  with  glass  stop- 
cock D,  by  which  the  acid  is  introduced  into  the  flask.  The  hydrogen  sulphide 
passes  through  a  potash  connecting  bulb  with  trap  as  shown.  A  hole  blown 
in  the  side  of  the  tube  prevents  liquid  being  swept  through.  Connected  to  the 
potash  bulb  is  the  absorption  bulb  C,  which  is  suspended  by  a  wire  attached  to 
the  thistle  tube.  The  apparatus  is  compact,  so  that  on  a  large  hot  plate, 
30  by  20  ins.,  a  dozen  outfits  may  readily  be  accommodated.  With  the  use  of 
this  apparatus  the  writer  has  been  able  to  make  over  seventy-five  determinations 
of  sulphur  in  steel  in  an  ordinary  day's  run. 

Preparation  and  Amount  of  Sample 

The  amount  of  material  to  be  taken  for  the  determination  depends  upon  the 
sulphur  content  as  shown  by  the  following  table: 

Approximate  %  of  Sulphur  Present.  Amount  to  take  for  Analysis. 

0.01  to    1  5       grams 

1.0    to  10  1 

10. 00  to  30  0.5 

Above  30  0.25 

The  class  of  material  will  govern  the  method  of  procedure. 

Iron  and  Steel.  A  5-gram  sample  of  drillings  or  finely  divided  material  is 
treated  directly  in  the  evolution  flask  with  hydrochloric  acid,  1:1,  and  the 
hydrogen  sulphide  absorbed  in  ammoniacal  cadmium  chloride.  The  sulphide 
formed  is  titrated  with  iodine. 

Iron  Ore  Briquettes  and  Materials  Containing  Sulphates.  Low  Sulphur. 
Preliminary  Reduction.  A  5-gram  sample  is  intimately  mixed  with  an  equal 
weight  of  reducing  mixture  (NaHC03+Al+C)  and  wrapped  in  a  9-cm.  ashless 
filter.  The  charge  is  placed  in  a  50-cc.  nickel  crucible  with  cover.  The  crucible 

1 W.  W.  Scott. 


SULPHUR 


401 


is  inserted  half  way  into  an  asbestos  board  or  perforated  silica  plate  (see  Fig.  65) 
and  after  covering,  placed  over  a  low  flame  of  a  Me*ker  blast  burner.  The 
flame  of  the  blast  is  gradually  increased  during  the  first 
five  minutes  and  the  charge  blasted  for  about  twenty 
minutes.  The  crucible  will  appear  a  bright  red  and  car- 
bon monoxide  gas  escaping  from  under  the  crucible  lid 
will  burn.  The  loss  of  sulphur,  however,  is  not  appreci- 
able. The  crucible  is  cooled  without  removing  the  cover. 
When  cold  the  fused  mass  is  quickly  pulverized  and 
placed  in  the  dry  evolution  flask  containing  a  mat  of 
aluminum  granules  or  C.P.  zinc  dust  or  granulated  tin. 
Hydrogen  sulphide  is  best  evolved  with  hydrochloric 
acid  to  which  4  or  5  cc.  of  10%  stannous  chloride  has 
been  added  to  reduce  ferric  iron.  The  gas  is  absorbed 
in  ammonical  cadmium  chloride  and  the  cadmium  sulphide 
formed  titrated  with  iodine. 

Iron  Sulphide  for  Available  H2S.  Since  this  product 
runs  over  20%  available  hydrogen  sulphide  not  over  0.5 
gram  sample  should  be  taken.  The  H2S  is  evolved  by 
addition  of  dilute  sulphuric  acid,  1  :  4,  in  place  of  hydro- 
chloric acid,  and  is  absorbed  by  neutral  cadmium  sulphate. 
The  acid  formed  by  the  reaction  is  titrated  by  standard 
N/10  NaOH. 

Sodium  Sulphide    or  Water-soluble    Sulphides   for 
Available  H2S.     Ten  grams  dissolved  in  water  and  diluted  to  1000  cc.;   50  cc. 
=  (0.5  gram)  taken  for  analysis. 


FIG.  65. 


Details  of  Procedure 

Evolution  of  Hydrogen  Sulphide.  One-half  to  1  gram  of  aluminum  or  zinc 
granules,  20  mesh,  is  placed  over  the  bottom  of  the  evolution  flask  and  the 
sample  placed  above  this  mat  of  metal.  The  stopper  with  the  thistle  tube  and 
condenser  is  inserted  snugly  into  the  neck  of  the  flask.  An  absorption  bulb 
containing  about  20  cc.  of  distilled  water  is  attached  to  the  condenser.  This 
bulb  serves  as  a  trap  for  the  HC1  that  is  driven  out  of  the  flask  during  the  boil- 
ing. To  this  bulb  is  attached  a  second  bulb  containing  50  cc.  of  ammoniacal 
cadmium  chloride.  A  third  bulb  may  be  attached  if  the  sulphur  content  of  the 
material  examined  is  high;  this,  however,  is  seldom  necessary  when  ammoniacal 
cadmium  chloride  is  used.  The  rubber  stopper  and  all  rubber  connections 
being  air  tight,  100  cc.  of  warm  HC1,  1  :  1,  is  poured  into  the  flask  through  the 
thistle  tube,  the  stem  of  which  should  now  dip  well  below  the  acid.  The  stop- 
cock is  closed  during  the  violent  action  of  the  acid  on  the  sample  and  opened 
when  this  has  subsided.  The  acid  trap  prevents  loss  of  H2S  through  the  thistle 
tube.  The  apparatus  is  now  placed  on  the  hot  plate  and  the  sample  boiled 
vigorously  for  about  twenty  minutes.  The  flask  is  taken  off  the  hot  plate  and  the 
contents  allowed  to  cool.  At  this  stage  it  may  be  advisable  to  draw  a  current 
of  air  through  the  apparatus  to  sweep  out  any  residual  H2S  that  may  remain  in 
the  flask.  Hydrogen  gas  is  preferable  to  air. 

Titration.  (a)  The  contents  of  the  bulbs  are  poured  into  a  600-cc.  beaker 
containing  about  400  cc.  of  distilled  water.  The  bulbs  are  washed  out  first 


402  SULPHUR 

with  water  and  then  with  dilute  acid.  The  excess  of  ammonia  is  neutralized  with 
concentrated  HC1,  5  cc.  of  starch  solution  added  and  the  sulphide  immediately 
titrated  with  standard  iodine,  additional  hydrochloric  acid  being  added  from  time 
to  time  during  the  titration  to  insure  complete  decomposition  of  the  sulphide. 
The  liquid  appears  yellowish  red,  orange,  purplish  red  and  finally  a  deep  blue. 
Since  the  sulphide,  when  present  in  appreciable  quantity,  decomposes  slowly, 
the  solution  should  be  strongly  acid  at  the  completion  of  the  titration,  and  five 
minutes  should  be  allowed  for  a  permanent  end-point. 

Knowing  the  amount  of  iodine  necessary,  a  check  run  may  be  made  by 
adding  to  the  neutral  solution  an  excess  of  iodine  followed  by  5  cc.  of  starch 
solution  and  a  large  excess  of  concentrated  hydrochloric  acid.  The  excess  of 
iodine  is  titrated  with  N/10  thiosulphate,  Na2S203,  solution.  (Arsenous  acid  will 
not  do.)  This  procedure  will  prevent  the  loss  of  H2S,  which  is  apt  to  occur  in 
samples  high  in  sulphide. 

(6)  An  alternate  method  is  frequently  advisable  in  high  sulphurs.  The  precip- 
itate is  separated  from  the  solution  containing  ammonia  by  filtration.  The 
cadmium  sulphide  is  now  placed  in  the  600-cc.  beaker  with  water  and  an  excess 
of  iodine  run  in.  Starch  is  added,  followed  by  hydrochloric  acid.  The  excess 
of  iodine  is  titrated  with  sodium  thiosulphate,  Na^Oa.  By  this  method  the 
heat  action  during  the  neutralization  of  ammonia  is  avoided  and  only  the  pre- 
cipitate is  titrated. 

When  the  iodine  titration  exceeds  50  cc.  of  N/10  iodine,  a  smaller  amount 
of  the  sample  should  be  taken  for  analysis;  the  iodine  titration  for  amounts 
of  sulphur  exceeding  0.1  gram  is  not  satisfactory,  owing  to  a  fading  end-point. 
The  method  for  determining  available  hydrogen  sulphide  in  high  sulphide 
products,  dealing  with  the  titration  of  the  free  acid  formed  during  the  reaction, 
permits  of  larger  samples  being  taken.  Details  of  this  method  are  given  on  page  407. 

One  cc.  N/10  iodine  =0.001604  gram  S. 

Tenth  Normal  Equivalents 

One  cc.  of  N/10  iodine  =0.001 704  gram  H2S 
"  "  =0.004396  gram  FeS 

=0.003904  gram  Na2S 
"  "  =0.003607  gram  CaS 

11  "  =0.008471  gram  BaS 

"  "  =0.00561    gramSb2S3 

"  "  =0.011959  gram  PbS 

=0.011634  gram  HgS 
"  "  =0.004782  gram  CuS 

=0.007224  gram  CdS 
"  "  =0.004872  gram  ZnS 

11  "  =0.003269  gram  Zn 

Combustion  Method  for  Evaluation  of  Sulphide  Ores.  When  a  sulphide  ore 
(pyrrhotite)  is  heated  to  redness  in  presence  of  oxygen  both  sulphur  dioxide 
and  trioxide  are  evolved.  The  first  may  be  absorbed  in  suitable  reagents  and  esti- 
mated volumetrically  or  gravimetrically.  The  trioxide  mist  is  best  retained 
by  asbestos  and  weighed.  The  combustion  furnace  with  silica  tube  used  for 
determinations  of  carbon  is  adapted  for  sulphide  ores.  The  finely  powdered 


SULPHUR  403 

dry  sample,  spread  in  a  thin  layer  in  a  3-inch  porcelain  boat,  is  placed  in  the  red 
hot  tube  and  burned  in  a  current  of  oxygen,  which  has  been  purified  by  passing 
through  sodium  hydroxide,  strong  sulphuric  acid  and  phosphorus  pentoxide. 
The  trioxide  mist  is  removed  by  passing  the  evolved  gases  through  an  asbestos 
filter  (P205  bulb  with  asbestos  in  one  arm  adjacent  to  the  combustion  tube  and 
P205  in  the  other).  The  S02  is  absorbed  in  a  mixture  of  bromine  and  nitric  acid, 
and  the  sulphuric  acid  formed  is  titrated  after  removing  the  reagent  by  evapora- 
tion; or  it  is  absorbed  in  an  excess  of  standard  iodine,  the  excess  titrated  with 
sodium  arsenite  or  thiosulphate,  and  sulphur  calculated.  The  iodine  method  is 
preferable  to  the  bromine,  as  it  is  more  rapid  and  the  reagent  less  disagreeable 
to  handle.  The  gravimetric  method  is  the  most  reliable.  The  dioxide  is  absorbed 
in  chromic  acid  (caustic  will  not  give  correct  results  owing  to  its  affinity  for  carbon 
dioxide,  a  product  of  combustion  of  the  free  and  combined  carbon,  that  are  gen- 
erally present  in  sulphide  ores.  Pyrrhotite  frequently  contains  as  much  as  1% 
carbon)  and  weighed.  The  combustion  method  cannot  be  recommended  for 
extreme  accuracy.  The  procedure  may  be  used  for  the  estimation  of  available 
sulphur,  but  does  not  give  the  total  sulphur  of  the  ore,  since  .2  to  .5%  remains 
in  the  cinder.  Error  may  result  from  the  following  causes:  (1)  Incomplete 
combustion  of  the  sulphur — due  to  sublimation  of  the  sulphur  to  cooler  zones 
of  the  combustion  tube,  and  to  a  fine  mist  of  sulphur  passing  unburned  into  the 
asbestos,  where  it  is  retained  with  S03  and  weighed  as  such.  (2)  Error  due  to 
combined  water  of  the  ore.  The  results  are  apt  to  be  .05  to  0.5%  lower  than  those 
obtained  by  the  barium  sulphate  procedures,  the  sulphur  of  the  cinder  being  in- 
cluded with  the  available  sulphur. 


VOLUMETRIC  METHODS  FOR  DETERMINING  SOLUBLE 

SULPHATES 

Combined  sulphuric  acid  in  soluble  sulphates  is  best  determined  gravi- 
metrically;  occasionally,  however,  a  volumetric  procedure  is  of  technical  value. 
A  number  of  volumetric  methods  are  based  on  the  insolubility  of  barium  sul- 
phate. Two  general  procedures  deserve  mention:  addition  of  barium  chloride 
in  known  amount  in  slight  excess  of  that  required  by  the  sulphate,  and  titrating 
the  excess  either  with  a  soluble  carbonate  or  a  chromate;  or  addition  of  barium 
chromate  and  titrating  the  alkali  chromate  formed  by  the  reaction.  The  sul- 
phate is  also  determined  by  precipitation  with  a  weak  organic  base  benzidine, 
added  in  form  of  the  hydrochloride  salt;  the  benzidine  sulphate,  filtered  off,  is 
titrated  with  caustic.  The  typical  procedures  given  below  will  meet  general 
requirements  for  the  volumetric  determination  of  sulphates. 

Determination  of  Sulphur  by  Titration  with  Barium  Chloride 
and  Potassium  Chromate— Wildenstein's  Method  Modified  1 

Reaction. 

Na2S04+BaCl2  =BaS04+2NaCl  and  excess  BaCl2+K2Cr04  =BaCr04+2KCl. 

Procedure.  The  substance  containing  the  sulphate  in  solution  is  diluted  to 
50  cc.  in  a  small  flask,  acidified  with  hydrochloric  acid,  if  necessary,  heated  to 

1  See  "  Volumetric  Analysis,"  Sutton,  10th  Ed.,  p.  350. 


404  SULPHUR 

boiling,  and  precipitated  with  a  slight  excess  of  N/4  barium  chloride  added  from 
a  burette  (1  cc.  BaCl2  =0.01  gram  S03).  The  precipitate  settles  rapidly,  so  that  a 
large  excess  of  the  reagent  may  readily  be  avoided.  The  mixture  is  cautiously 
neutralized  with  ammonia,  free  from  carbonate  (C02  may  be  precipitated  with 
CaCl2  solution),  the  solution  heated  to  boiling,  and  N/4  potassium  chromate 
added  from  a  burette  in  .5  cc.  portions,  each  time  removing  the  flask  from  the 
heat,  allowing  the  precipitate  to  settle  and  examining  the  clear  solution.  A 
faint  yellow  color  will  appear  as  soon  as  the  excess  of  barium  has  been  precipitated 
and  a  few  drops  of  the  chromate  in  excess  are  present  in  the  solution.  The  value 
of  the  chromate  being  equivalent  to  the  barium  chloride  cc.  per  cc.,  the  difference 
between  the  two  titrations  is  due  to  the  barium  chloride  required  by  the  sulphate. 

One  cc.  N/4  BaCl2  =0.01  gram  S03. 

NOTES.  Salts  of  the  alkalies,  alkaline  earths  (Sr  and  Ca)  and  zinc  and  cadmium 
do  not  interfere.  Nickel,  cobalt  and  copper,  however,  give  colored  solutions  which 
prevent  the  yellow  chromate  being  seen.  Should  the  latter  be  present,  the  end-point 
may  be  recognized  by  using  ammoniacal  lead  acetate  as  an  outside  indicator  (1  vol. 
NH4OH+4  vols.  PbC2H3O2-3H3O,  5%  sol.),  the  indicator  and  titrated  solution  being 
mixed  drop  per  drop  on  a  white  tile.  A  yellowish  red  color  indicates  the  presence  of 
chromate. 

Precipitation  of  the  Sulphate  with  Barium  Chromate  and  Titra= 
tion  of  Equivalent,  Liberated  Chromate  with  Iodine  and 
Thiosulphate,  Hinman's  Method.1 

The  sulphate,  precipitated  by  barium  chromate,  liberates  an  equivalent 
amount  of  chromic  acid,  which  is  determined  by  treating  with  potassium  iodide 
and  titrating  the  liberated  iodine  with  thiosulphate. 

Reactions.  Na2S04+BaCr04  =BaS04+Na2Cr04, 

Na2Cr04+3KI+8HCl=2NaCl+3KCl+CrCl3+4H20+3I, 

2Na2S203+I2  =2NaI+Na2S406. 

Procedure.2  The  solution  of  the  sulphate,  containing  not  over  2  per  cent 
of  S03,  if  acid,  is  almost  neutralized  with  potassium  hydroxide,  then  heated  to 
boiling,  and  an  excess  of  barium  chromate  solution  added.3  After  boiling  for 
one  to  five  minutes,  the  hot  solution  is  neutralized  by  adding  calcium  car- 
bonate 4  until  no  further  effervescence  occurs.  The  precipitate  is  filtered  off  and 
washed  with  hot  water.  The  combined  filtrates  containing  the  chromate  liberated 
by  the  sulphate  through  double  decomposition,  is  acidified  with  5  cc.  strong 

1  Treadwell  and  Hall,  "  Analytical  Chemistry,"  2,  4th  Ed.,  p.  716.    Am.  Jour.  Sci. 
and  Arts,  114,  478. 

2  See  p.  716. 

8  The  barium  chromate  used  should  be  free  from  soluble  chromate,  barium  car- 
bonate or  soluble  barium  salt.  The  compound  may  be  prepared  by  precipitating  with 
potassium  chromate  added  to  a  boiling  solution  of  barium  chloride.  The  precipitate 
is  washed  with  boiling  water  containing  a  little  acetic  acid,  and  finally  with  pure  water, 
and  then  dried.  Four  grams  of  the  dry  salt  are  dissolved  in  a  liter  of  normal  hydro- 
chloric acid. 

4  In  presence  of  iron,  zinc  and  nickel,  the  solution  is  neutralized  with  ammonium 
hydroxide  and  an  excess  added;  after  boiling,  the  solution  is  filtered.  By  using  calcium 
carbonate  insoluble  basic  chromates  of  these  elements  would  be  formed,  and  low 
results  for  SO3  would  follow.  This  is  avoided  by  the  use  of  ammonia. 


SULPHUR  405 

hydrochloric  acid  per  each  100  cc.  of  filtrate  and  an  excess  of  potassium  iodide 
added.  Iodine  equivalent  to  the  chromic  acid  is  liberated.  This  is  titrated  with 
N/10  sodium  thiosulphate. 

One  cc.  of  N/10  thiosulphate  =0.003269  gram  H^.1 

Benzidine  Hydrochloride  Method2 

Benzidine  sulphate,  Ci2H8(NH2)2-H2S04,  is  scarcely  soluble  in  water  con- 
taining hydrochloric  acid.  The  weak  base  benzidine  is  neutral  to  phenolphthalein 
and  the  acid  in  its  sulphate  may  be  titrated  with  an  alkali.2  The  method  gives 
reliable  results  in  the  analysis  of  all  sulphates,  provided  no  substances  are  present 
which  attack  benzidine,  and  provided  the  amount  of  other  acids  and  salts  present 
is  not  too  great.3 

Reaction.     Na2S04+Ci2H8(NH2)2.2HCl  =2NaCl+Ci2H8(NH2)2.H2S04    and 
C12H8(NH2)2.H2S04+2NaOH=C12H8(NH2)2.2H20+Na2S04. 

Reagent.  Benzidine  hydrochloride  is  prepared  by  taking  6.7  grams  of  the 
free  base,  or  the  corresponding  amount  of  the  hydrochloride  and  mixing  into  a 
paste  with  20  cc.  of  water  in  a  mortar.  Twenty  cc.  of  hydrochloric  acid  (sp.gr. 
1.12)  are  added  and  the  mixture  diluted  to  exactly  1000  cc.  One  cc.  of  this 
solution  corresponds  to  0.00357  gram  H2S04.  The  solution  has  a  brown  color. 
Brown  flakes  are  likely  to  separate  out  on  standing,  but  these  do  no  harm. 

Procedure.  The  sulphate  solution  is  diluted  with  water  so  that  there  is  at 
least  a  50-cc.  volume  for  each  0.1  gram  sulphuric  acid  present.  An  equal  volume 
of  the  reagent  is  vigorously  stirred  in,  and  the  precipitate  allowed  to  settle  for 
ten  minutes.  The  solution  is  filtered  onto  a  double  filter,  placed  on  a  porcelain, 
perforated  plate  in  a  funnel  (a  Btichner  is  O.K.),  gentle  suction  being  applied. 
The  last  portions  of  the  precipitate  are  transferred  to  the  filter  by  means  of  small 
portions  of  the  clear  nitrate,  and  the  compound  then  washed  with  20  cc.  of  cold 
water  added  in  small  portions  and  sucked  dry  with  each  addition.  The  precipi- 
tate and  filter  are  placed  in  an  Erlenmeyer  flask,  50  cc.  of  water  added,  and  the 
mixture  shaken  until  homogeneous.  Phenolphthalein  indicator  is  now  added, 
the  mixture  heated  to  about  50°  C.  and  titrated  with  N/10  sodium  hydroxide. 
When  the  end-point  is  nearly  reached,  the  liquid  is  boiled  for  five  minutes,  and 
the  titration  then  completed. 

One  cc.  N/10  =0.004904  gram  H2S04. 

1  N/10  Na2S203=  ^j^4=  98.08  -5-30=  3.269. 

2  Method  suggested  by  Raschig,  Z.  a.  Chem.,  617  and  818,  1903. 

8  Friedheim  and  Nydegger  (Z.  a.  Chem.,  9,  1907)  have  found  that  there  should 
not  be  more  than  10  mol.  HC1,  15  mol.  HNO3,  20  mol.  HC2H3O2,  5  mol.  alkali  salt, 
or  2  mol.  ferric  iron  present  to  1  mol.  H2SO4.  See  Treadwell  and  Hall,  "  Analytical 
Chemistry,"  pp.  714-716. 


406  SULPHUR 

DETERMINATION  OF  PERSULPHATES 
Ferrous  Sulphate  Method 

Ferrous  salts  in  cold  solutions  are  oxidized  to  ferric  form  by  persulphates. 
Advantage  is  taken  of  this  action  in  the  quantitative  determination  of  persul- 
phates. 

Reaction.    2FeS04+H2S208  =  Fe2(S04)3+H2S04. 

Procedure.1  About  2.5  grams  of  the  persulphate  are  dissolved  in  water  and 
diluted  to  100  cc.  Ten  cc.  of  this  solution,  equivalent  to  one-tenth  of  the  sample, 
weighed  out,  are  placed  in  a  flask  and  a  considerable  excess  of  standard  ferrous 
sulphate  solution 2  added,  say  100  cc.  measured  out  from  a  burette.  The  solution 
is  diluted  with  an  equal  volume  of  hot,  distilled  water  (70  to  80°  C.),  and  the 
excess  ferrous  sulphate  titrated  with  N/10  potassium  permanganate.  This  titra- 
tion  is  deducted  from  the  permanganate  equivalent  of  100  cc.  of  the  ferrous 
solution  taken  (if  this  amount  was  used).  The  difference  is  due  to  persulphate 
oxidation. 

One  cc.  N/10  KMn04  =0.009708  gram  H2S208;  or  =0.0114  gram  (NH4)2S208; 
or  =0.01352  gram  K2S208. 

Oxalic  Acid  Method  3 

Oxalic  acid,  in  presence  of  silver  sulphate,  reduces  parsulphates  in  accordance 
with  the  reaction, 

H2C204+H2S208  =2H2S04+2C02. 

Procedure.  About  0.5  gram  of  the  persulphate  is  placed  in  an  Erlenmeyer 
flask,  50  cc.  of  N/10  oxalic  acid  added,  together  with  0.2  gram  silver  sulphate 
in  20  cc.  of  10%  sulphuric  acid  solution.  The  mixture  is  heated  on  the  water 
bath  for  about  half  an  hour  to  expel  carbon  dioxide.  When  the  evolution  ceases  the 
liquid  is  diluted  to  100  cc.  with  warm  water  and  titrated  warm  (about  40°  C.) 
with  N/10  potassium  permanganate.  The  excess  of  oxalic  acid  is  titrated,  the 
difference  is  due  to  oxidation  by  the  persulphate. 

For  calculation  see  factors  in  previous  method. 

1  Method  suggested  by  Le  Blanc  and  Eckardt,  C.  N.,  81,  38. 

2  About  30  grams  of  ferrous  sulphate  or  ferrous  ammonium  sulphate  crystals  are 
dissolved  in  900  cc.  of  water  and  the  volume  made  to  1000  cc.  with  concentrated  sul- 
phuric acid.    The  reagent  is  standardized  against  N/10  potassium  permanganate 
and  the  value   per  cc.  in  terms  of  the  standard  permanganate  noted,  the  cc.  per- 
manganate solution  required  divided  by  the  cc.  of  ferrous  sulphate  solution  taken 
for  titration,  gives  value  of  the  reagent  in  terms  of  the  permanganate. 

The  solutions  are  beet  verified  upon  a  persulphate  of  known  purity. 
*  R.  Kcmpf,  Ber  ,  38,  3965,  1905. 


SULPHUR  407 

DETERMINATION  OF  SULPHUR  IN  COMBINATION  AS  SUU 
PHIDES,  SULPHITES,  BISULPHITES,  METABISULPHITES, 
THIOSULPHATES,  SULPHATES. 

Available  Hydrogen  Sulphide  in  Materials  High  in  Sulphide  Sul= 
phur.     Iron  Sulphide,  Sodium  Sulphide,  etc. 

Evolution  Method.  Since  it  is  desired  to  obtain  the  H2S  that  ordinarily 
would  be  obtained  when  the  sulphide  is  treated  with  a  strong  acid,  the  mat  of 
metallic  aluminum  or  zinc  and  the  addition  of  stannous  chloride  solution  used 
in  the  procedure  given  on  page  401  is  omitted  here. 

Procedure.  0.5  to  1  gram  of  the  sulphide  is  placed  in  the  dry  evolution  flask. 
All  connections  are  now  made  as  directed  in  the  general  procedure.  Three 
absorption  bulbs  containing  neutral  solution  of  cadmium  sulphate  are  connected 
to  the  condenser,  and  supported  by  wires  attached  to  the  thistle  tube  and  the 
arm  of  the  condenser.  All  connections  being  tight,  100  cc.  of  dilute  sulphuric 
acid,  1  :  4  are  added  through  the  thistle  tube  and  H2S  evolved.  The  procedure 
is  now  the  same  as  described  on  page  401. 

Titration.  When  the  evolution  of  the  H2S  is  complete,  the  bulbs  containing 
the  precipitate  are  emptied  into  a  beaker  and  carefully  washed  out.  The  pre- 
cipitate is  now  filtered  and  washed  five  or  six  times  until  free  of  acid.  Methyl 
orange  is  added  to  the  filtrate  and  the  free  acid  titrated  with  N/10  NaOH. 

The  precipitate  may  be  titrated  with  iodine  according  to  (6)  under  general 
method  of  procedure,  using  an  excess  of  iodine,  followed  by  starch  and  acid  and 
then  titrating  back  with  sodium  thiosulphate  solution.  A  double  check  may  thus 
be  obtained.  See  page  402. 

If  it  is  desired  to  weigh  the  CdS  precipitate,  it  is  best  to  evolve  the  H2S  into  a 
neutral  solution  of  cadmium  salt.  The  precipitate  formed  in  a  neutral  or  slightly 
acid  solution  is  crystalline  and  easily  filtered,  whereas  that  formed  in  an  ammoni- 
acal  solution  is  gelatinous. 

When  a  neutral  CdS04  or  CdCl2  solution  is  used,  H2S  should  be  evolved  by 
sulphuric  acid  and  not  by  hydrochloric  acid,  as  the  latter  is  volatile,  and  will  pass 
through  the  condensing  bulb  recommended  in  the  general  procedure. 

One  cc.  N/10  NaOH  =  .001704  gram  H2S 
=  .004396  gram  FeS 
=  .003904  gram  Na2S. 

Hydrogen  Sulphide  and  Soluble  Sulphides 

Direct  titration  of  hydrogen  sulphide  water,  and  soluble  sulphides  in  solution 
may  be  made  in  absence  of  other  substances  acted  upon  by  iodine.  The  solution 
containing  the  sulphide  is  added  to  an  excess  of  N/10  iodine  solution,  made  acid 
with  hydrochloric  acid,  and  the  excess  iodine  titrated  with  N/10  sodium  thio- 
sulphate. The  following  reaction  takes  place: 

H2S+I2=2HI+S.  The  cc.  Na2S2O3  are  subtracted  from  cc.  1=1  reacting 
with  H2S.  One  cc.  N/10  iodine  =0.00174  gram  H2S. 

NOTE.  The  soluble  sulphide  may  be  determined  gravimetrically  by  oxidizing 
with  bromine,  the  reagent  being  added  until  the  solution  is  colored  brownish  red> 
the  excess  of  the  halogen  removed  by  boiling  and  the  sulphate  precipitated  as  BaSOi, 


408  SULPHUR 


Determination  of  a  Sulphide  and  a  Sulphydrate  in  Presence  of 

Each  Other 

When  a  mixture  of  sulphide  and  sulphydrate  is  treated  with  iodine  the  follow- 
ing reactions  take  place: 

H2S+I2=2HI-hS    and    NaHS+2I2=NaI+HI+S. 

It  will  be  noticed  that  the  acidity  produced  by  the  first  reaction  is  twice  that 
caused  by  the  iodine  action  on  the  sulphydrate,  and  that  the  acidity  in  the  latter 
titration  remains  unaffected.  The  reactions  with  the  alkali  salts  is  effected  by 
addition  of  a  standard  iodine  solution  containing  a  known  amount  of  hydrochloric 
acid.  The  reactions  in  this  case  are  as  follows: 

Na2S+2HCl  =  2NaCl+H2S  and  NaSH+HCl  =  NaCl+H.8.  The  iodine  reacts 
with  the  H2S  as  follows:  H2S+I2  =2HI+S. 

From  the  second  set  of  reactions  it  is  evident  that  the  quantity  of  hydriodic 
acid  formed  by  the  action  of  iodine  on  the  sulphide  is  equivalent  to  the  hydro- 
chloric acid  required  to  decompose  the  sulphide,  so  that  the  acidity  remains 
unchanged.  On  the  other  hand  with  sulphydrate,  NaSH,  the  hydriodic  acid 
formed  by  the  iodine  oxidation,  is  twice  the  equivalent  of  hydrochloric  acid  required 
to  decompose  the  acid  salt.  Hence  it  is  evident  that  the  acidity  is  a  measure 
of  the  quantity  of  sulphydrate  present  in  the  mixture.  From  the  second  set  of 
reactions  the  following  procedure  is  devised. 

Procedure.  To  a  measured  amount  of  N/10  iodine  solution  containing  a 
measured  amount  of  N/10  hydrochloric  acid  (the  mixture  diluted  to  400  cc.) 
is  added  the  solution  containing  the  sulphide  and  sulphydrate  from  a  burette, 
until  the  stirred  solution  becomes  a  pale  yellow  color.  (The  cc.  of  solution  added 
is  noted  and  its  equivalent  of  the  sample  calculated.)  Starch  is  now  added  and 
the  excess  of  the  iodine  titrated  with  N/10  sodium  thiosulphate.  The  cc.  of 
thiosulphate  in  terms  of  N/10  solution  subtracted  from  the  cc.  N/10  iodine 
solution  taken  give  cc.  iodine  required  by  the  sample  added.  The  acidity  of  the 
solution  is  now  determined  by  titration  with  N/10  sodium  hydroxide.  The  cc. 
NaOH  required  by  the  HI  give  total  NaOH  minus  cc.  N/10  HC1  present  in  the 
iodine  solution. 

Calculation.  A.  Cc.  N/10  iodine  required  by  the  sample  minus  twice  the 
cc.  of  N/10  NaOH  required  by  HI  formed  by  the  reaction  multiplied  by  0.003903 
give  weight  of  Na2S,  (i.e.,  cc/I  -2  cc.  NaOH)  X 0.003904  =gram  Na2S. 

B.  Cc.  N/10  NaOH  required  by  the  HI  multiplied  by  0.00560  gives  gram 
weight  of  NaHS.  Or  in  brief:  cc.  NaOH  X 0.005608  =  gram  NaHS. 

The  above  weights  multiplied  by  100  and  divided  by  the  weight  of  sample 
used  in  the  iodine  titration  give  per  cent  of  constituents  in  the  sample. 

The  method  is  of  value  in  the  analysis  of  alkali  sulphides  in  absence  of  other 
compounds,  which  are  decomposed  by  hydrochloric  acid  and  which  react  with 
iodine. 

Determination    of   Thiosulphate    in    Presence    of   Sulphide 
and   Sulphydrate 

The  sulphide  and  sulphydrate  sulphur  is  removed  from  the  solution  by  adding 
an  excess  of  freshly  precipitated  cadmium  carbonate.  The  solution  is  filtered 
and  diluted  to  a  definite  volume  and  the  thiosulphate  determined  on  an  aliquot 


SULPHUR  409 

portion  by  running  it  into  an  excess  of  N/10  iodine  solution  and  titrating  the 
excess  of  iodine  with  N/10  thiosulphate  solution. 

One  cc.  N/10  iodine  =0.024822  gram  Na2S203-5H20. 

Determination  of  Sulphates  and  Sulphides  in  Presence  of 

One  Another 

In  one  portion  of  the  sample  the  sulphide  is  decomposed  and  the  hydrogen 
sulphide  expelled  by  boiling  the  solution  (in  presence  of  C02  replacing  air  in  the 
flask)  after  acidifying  with  hydrochloric  acid.  The  sulphate  sulphur  may  now  be 
precipitated  as  BaS04  by  the  usual  methods. 

In  a  second  portion  total  sulphur  is  determined  after  oxidizing  the  sulphide 
with  an  excess  of  bromine  and  boiling  out  the  excess  of  halogen.  Total  sulphur 
minus  sulphate  sulphur  =  sulphide  sulphur. 

The  sulphide  may  be  oxidized  with  fuming  nitric  acid  by  boiling  the  solution 
in  a  flask  with  reflux  condenser.  The  nitric  acid  is  expelled  by  evaporating  the 
solution  down  to  a  moist  residue.  The  sulphate  is  now  precipitated  by  taking  up 
the  residue  with  water,  adding  HC1  and  then  sufficient  BaCk  to  cause  complete 
precipitation. 

Determining   the   Sulphur   in   Thiocyanic    (Sulphocyanic) 
Acid   and  its  Salts 

Oxidation  of  the  sulphur  may  be  accomplished  as  described  for  sulphides  in 
the  preceding  method  either  by  means  of  bromine  or  by  fuming  nitric  acid.  The 
sulphur  is  then  precipitated  as  BaS04  as  usual. 

Determination  of  Sulphurous  Acid  (SO2  in  Solution)  Free,  or 
Combined  in  Sulphites,  Acid  Sulphites,  Metabisulphites  and 
Thiosulphates 

Gravimetric  Method,  Oxidation  to  Sulphate  and  Precipitation  as  BaSO4. 

Sulphur  dioxide,  free  or  combined  in  a  soluble  salt,  may  be  oxidized  to  S03  or 
sulphate  by  means  of  an  oxidizing  agent  such  as  chlorine,  or  bromine,  or  hydrogen 
peroxide  (alkaline  solution).  The  sulphuric  acid  or  sulphate  may  be  then  pre- 
cipitated and  determined  as  BaS04  in  the  usual  way. 

Procedure.  The  halogen  (bromine  preferred)  is  added  (in  a  water-saturated 
solution)  in  large  excess  to  the  sample,  the  free  halogen  then  boiled  out,  and  sul- 
phuric acid  precipitated,  from  a  solution  made  slightly  acid  with  hydrochloric 
acid,  by  addition  of  a  solution  of  barium  chloride,  according  to  the  standard 
procedure. 

If  hydrogen  peroxide  is  used,  the  solution  should  be  made  alkaline  with 
ammonia  and  the  peroxide  added,  the  excess  boiled  out,  and  the  solution  then 
made  acid  as  directed  above. 

BaS04X0.3517=H2S03,  or  X 0.5401  =Na2S03,  or  X 0.4458  =NaHS03,  or 
X0.3387=Na2S.03,  or  X0.2745=S02. 

NOTE.  If  hydrogen  peroxide  is  used,  it  should  be  tested  for  H2SO4  and  allowance 
made  accordingly. 


410  SULPHUR 


Volumetric  Methods 

Titration  with  Iodine.  Sulphurous  Acid,  Sulphites,  Metabisulphites,  Thio- 
sulphates.  Sulphurous  acid,  combined  or  free,  may  be  titrated  with  iodine  solu- 
tion, the  following  reaction  taking  place: 

S02-f-2I+2H20  =H2S04+2HI. 

The  titration  is  accomplished  by  adding  the  solution  of  sulphurous  acid,  sulphite, 
or  thiosulphate  to  the  iodine,  not  in  the  reverse  order,  since  in  the  latter  order  low 
results  are  obtained,  unless  the  solution  is  very  dilute  (less  than  0.04%  SO^).1 

Procedure.  Five  grams  of  the  sample  (sulphurous  acid  solution  titrated 
directly)  are  dissolved  in  a  little  water  and  transferred  to  a  500-cc.  graduated 
flask,  then  made  to  volume.  Each  cc.  of  this  solution  contains  0.01  gram  of  the 
sample;  100  cc.  of  N/10  iodine,  or  their  equivalent  if  the  solution  is  stronger  or 
weaker,  are  placed  in  a  beaker  together  with  a  few  drops  of  hydrochloric  acid.  A 
portion  of  the  sample  in  a  100-cc.  burette  is  now  run  into  the  iodine,  with  con- 
stant stirring,  until  the  color  of  the  free  iodine  has  almost  faded  out;  a  little 
starch  solution  is  now  added  and  the  titration  continued  to  the  complete  fading 
of  the  blue  color. 

Since  each  cc.  of  the  sample  contains  0.01  gram  of  the  material,  it  follows 
that  the  100-cc.  iodine  equivalent  in  terms  of  the  material  titrated  expressed  to 
the  fourth  decimal  place  as  a  whole  number,  if  divided  by  the  cc.  of  the  sample 
required,  will  give  the  per  cent  of  the  substance  sought,  provided  other  titratable 
substances  are  absent. 

Example.  Suppose  sodium  sulphite  is  being  titrated,  then  since  100  cc.  of 
N/10  iodine  are  equivalent  to  0.6304  gram  Na2S03,  6304  divided  by  the  cc. 
Na2S03  solution  required  gives  per  cent  Na2S03.  If  63  cc.  were  required  the  salt 
would  be  100%  pure. 

NOTE.  When  the  iodine  equivalent  is  over  unity,  it  is  necessary  to  take  a  larger 
sample  per  500-cc.  volume  to  avoid  having  a  titration  of  over  100  cc.  For  example 
in  the  analysis  of  sodium  thiosulphate,  a  20^gram  sample  is  diluted  to  500  cc.  and  a 
portion  of  this  added  to  100  cc.  of  N/10  iodine  solution.  In  this  case  it  must  be  kept 
m  mind  that  each  cc.  of  the  sample  contains  0.04  gram  of  thiosulphate  and  the  per- 
centage calculated  accordingly  upon  completing  the  titration. 

If  the  titration  of  the  iodine  is  made  in  a  casserole,  the  end-point  may  readily  be 
recognized  without  the  addition  of  starch. 

Equivalents.     100  cc.  N/10  iodine  solution  will  oxidize: 

Sodium  sulphite  (anhydrous),  Na2S03  =0.6304  gram,  or  0.3203  gram  SOZ. 

Sodium  sulphite,  Na2S03.7H20  =  1.2606  grams. 

Acid  sodium  sulphite,  NaHS03=  0.5204  gram. 

Sodium  metabisulphite,  Na2S206  (anhydride  of  NaHS03)  =0.47535  gram. 

Sodium  thiosulphate,  Na2S203-5H20  =2.4822  grams. 

NOTE.  Hydrogen  sulphide  or  sodium  sulphide  are  also  titrated  with  iodine. 
Equivalents  for  100  cc.  N/10  iodine  =  0.1704  gram  H2S,  or  0.3904  gram  Na2S. 

1 A  secondary  reaction  takes  place,  the  hydriodic  acid  formed  reducing  the  SO2 
to  S,  e.g.,  SO2+4HI  =  2H2O+2I2+S.  (J.  Volhard,  Ann.  d.  Chem.  u.  Pharm.,  242, 
94.)  The  solution,  if  notjtoo  dilute,  will  show  a  distinct  separation  of  sulphur.  (Tread- 
well  and  Hall,  "  Analytical  Chemistry,"  2,  3d  Ed.)  Raschig  believes  that  a  loss  of 
SOz  occurs,  due  to  evaporation.  (Z.  Angew.  Chem.,  580,  1904.)  See  Sutton,  "Vol- 
umetric Analysis,"  10th  Ed.,  pp.  128, 129.  Gooch,  "  Methods  in  Chemical  Analysis," 
1st  Ed.,  pp.  364^368. 


SULPHUR  411 

Determination  of  Sodium  Thiosulphate.  The  iodine  titration  is  described 
on  page  410.  See  also  the  chapter  on  iodine. 

Acidimetric  and  Alkalimetric  Methods 

Titration  of  Sulphites,  Acid  Sulphites  (Metabisulphite)  or  Sulphurous 
Acid.  The  choice  of  indicator  is  important  as  the  titration  with  one  may  be 
different  from  that  obtained  in  presence  of  another.  For  example  the  titration 
of  sulphurous  acid  by  an  alkali  in  presence  of  phenolphthalein  is  twice  the  titration 
necessary  to  obtain  an  alkaline  reaction  with  methyl  orange.  The  reason  for 
this  is  evident  by  the  fact  that  Na2S03  is  neutral  to  phenolphthalein  and  alkaline 
to  methyl  orange,  whereas  NaHS03  is  neutral  to  methyl  orange  but  is  acid  to 
phenolphthalein.  Advantage  is  taken  of  this  in  the  analysis  of  salts  containing 
a  mixture  of  the  normal  and  acid  salts. 

Reaction.    With  phenolphthalein    H2S03+2NaOH  =Na2S03+2H20. 
With  methyl  orange       H2S03+NaOH  =  NaHS03+H20. 

On  the  other  hand  if  a  salt  is  being  titrated,  methyl  orange  cannot  be  used 
for  the  titration  of  metabisulphite  or  acid  sulphite,  since  these  salts  are  neutral 
to  this  indicator,  here  phenolphthalein  is  required  and  an  alkali  titration  made. 
Reaction.    NaHS03+NaOH  =Na2S03.     (Na2S205+H20  =  2NaHS03.) 
Again  if  sodium  sulphite,  Na2S03,  is  to  be  titrated,  phenolphthalein  would  not 
do  as  an  indicator,  since  Na2S03  is  neutral  to  this  indicator.    Here  an  acid  titra- 
tion is  required  with  methyl  orange  indicator  present : 

2Na2S03+H2S04  =  2NaHS03+Na2S04. 

A.  Sulphurous  Acid 

For  the  alkali  titration  of  this  acid  it  is  advisable  to  use  methyl  orange  as 
indicator,  since  this  is  not  affected  by  carbon  dioxide,  which  is  very  frequently 
present. 

Reaction.    H2S03+NaOH=NaHS03. 

One  cc.  N/l  NaOH  =0.06407  gram  S02,  or  =0.08209  gram  H2S03. 

B.  Sodium  Metabisulphite 

Sodium  acid  sulphite  does  not  exist  in  dry  form,  since  the  salt  loses  water 
and  the  anhydride  Na2S2Oa  results.  This  is  analogous  to  sulphurous  acid,  which 
exists  only  in  water  solution.  It  has  been  found  that  the  acid  sulphite  solution 
evaporated  to  crystallization  yields  a  product,  which  though  dried  with  extreme 
care,  forms  the  anhydride  salt,  Na2S205.  For  correct  report,  therefore,  the  solid 
should  be  reported  as  metabisulphite,  and  the  solution  of  the  salt  as  acid  sulphite. 

Since  metabisulphite  in  solution,  or  acid  sulphite,  is  neutral  to  methyl  orange, 
phenolphthalein  indicator  must  be  used  and  an  alkali  titration  made.  Carbon 
dioxide-free  water  and  reagents  should  be  used. 

Reaction.    Na2S205+H2O=2NaHS03  and  NaHS03+NaOH=Na2S03-t-H20. 

Procedure.  9.507  grams  of  the  finely  ground  powder  are  dissolved  in  about 
50  cc.  of  cold  saturated  salt  solution,  to  which  has  been  added  from  a  burette 
50  cc.  of  normal  sodium  hydroxide.  The  salt  solution  should  be  made  neutral  to 


412  SULPHUR 

phenolphthalein.  One  cc.  of  0.1%  solution  of  the  indicator  is  added  and  the 
excess  acid  sodium  sulphite  titrated  with  normal  sodium  hydroxide  until  a  per- 
manent faint  pink  color  is  obtained. 

Since  the  normal  equivalent  of  the  salt  has  been  taken  for  analysis  the  cc. 
alkali  titration,  including  the  50  cc.  originally  present,  will  give  the  percentage 
directly  in  terms  of  Na2S206. 

NOTE.  The  NaCl  serves  to  give  a  sharp  and  more  permanent  end-point.  It 
may  be  necessary  to  add  more  of  the  indicator  towards  the  end  of  the  titration. 

C.  Sodium  Sulphite,  NasSOs 

Sodium  sulphite,  Na2S03,  is  neutral  to  phenolphthalein  and  alkaline  to 
methyl  orange.  The  titration  of  this  salt  is  accomplished  by  addition  of  standard 
acid  in  presence  of  methyl  orange. 

Reaction.    2Na2S03-f-H2S04  =Na2S04-f  2NaHS03. 

Procedure.  The  normal  factor  weight  (12.6  grams)  of  the  salt  is  dissolved 
in  about  250  cc.  of  distilled  water,  1  cc.  of  methyl  orange  added,  followed  by 
normal  sulphuric  acid,  added  from  a  burette  until  a  faint  orange  end-point  is 
obtained.  As  in  the  case  of  the  metabisulphite,  each  cc.  of  normal  sulphuric 
acid  equals  1%  Na2S03.  Hence  the  percentage  is  obtained  directly  from  the 
burette  reading. 

NOTES.  Organic  coloring  matter  may  be  removed  from  the  solution  by  filtering 
through  charcoal. 

If  sodium  carbonate  is  present,  it  will  also  be  titrated.  A  correction  must  be 
applied  for  this.  In  the  presence  of  sodium  carbonate  the  solution  will  be  alkaline 
to  phenolphthalein.  An  approximate  estimation  of  this  may  be  obtained  by  titra- 
tion with  normal  acid  in  presence  of  this  indicator,  remembering  that  sodium  bicar- 
bonate, NaHCO3,  is  neutral  to  phenolphthalein,  hence  twice  this  titration  must  be 
deducted  from  the  total  methyl  orange  titration,  i.e.,  NaoCO3+H2SO4  (M.O.)  = 
Na£O4+H«COi  and  2Na2SO3+H2SO4  (P.)  =2NaHSO4+2NaHCO3.  (Alkaline  hydrox- 
ides will  also  be  titrated.)  CO2  may  also  be  obtained  by  the  standardprocedure  under 
carbon,  the  SO2  being  oxidized  by  addition  of  chromic  acid.  Na2CfOaX  1.5=  equiv- 
alent 


Sodium  carbonate  may  be  detected  in  a  sulphite  or  metabisulphite  by  adding 
cold,  dilute  acetic  acid  (25%)  to  the  dry  powdered  salt.  An  effervescence  is  due 
to  the  presence  of  carbonate,  since  a  sulphite  or  metabisulphite  does  not  effer- 
vesce under  similar  conditions. 


Determination  of  Sulphites,  Metabisulphites,  Thiosulphates, 
Sulphates,  Chlorides  and  Carbonates  in  Presence  of  One 
Another 


i.  Sodium  Sulphite, 

This  is  determined  by  titration  with  standard  acid  in  the  presence  of  methyl 
orange  indicator  according  to  the  standard  procedure  previously  described.  If 
a  carbonate  is  present,  allowance  must  be  made  for  this  as  stated 

One  cc.  N/l  H2S04  =0.126  gram  NazSOs.    Calculate  to  per  cent. 
Na2C03Xl.5  =  equivalent  Na2SO«. 


SULPHUR  413 


2.  Sodium  Metabisulphite, 

This  is  determined  by  titration  with  a  standard  alkali  in  the  presence  of 
phenolphthalein  indicator  according  to  the  procedure  previously  described. 

One  cc.  N/l  NaOH  =0.09507  gram  Na2S205.    Calculate  to  per  cent. 

3.  Sodium  Thiosulphate,  Na2$2O3 

One  gram  of  the  mixed  salts  is  placed  in  100  cc.  of  N/10  iodine  solution,  and 
the  excess  of  iodine  titrated  with  N/10  sodium  thiosulphate  according  to  the 
standard  procedure. 

Calculation.     {  (cc.  N/10  I  -cc.  N/10  Na2S203)  -[(%  Na2S206X2.104) 

Na2S03X  1.5864)]}  Xl.5814  =  %  Na2S203. 


4.  Sodium  Sulphate 

The  sample  is  dissolved  in  a  little  water,  hydrochloric  acid  added,  and  the 
solution  boiled  to  expel  all  of  the  S02.  Barium  sulphate  is  now  precipitated 
and  determined  according  to  the  standard  procedure. 

BaS04X0.6086  =Na2S04. 

NOTE.  The  amount  of  the  sample  required  is  governed  by  the  per  cent  Na2SOt 
present. 

5.  Sodium  Chloride 

The  sample  is  dissolved  in  water,  nitric  acid  added  and  the  solution  boiled 
until  all  the  S02  has  either  been  volatilized  or  oxidized.  The  chlorine  of  the 
chloride  is  now  precipitated  with  silver  nitrate  from  a  hot  solution  by  the  usual 
procedure. 

AgClX0.4078=NaCL 

NOTE.  The  amount  of  the  sample  taken  is  governed  by  the  per  cent  of  NaCl 
present. 

6.  Sodium  Carbonate,  Na2COs 

Carbon  dioxide  is  evolved  from  the  mixture  by  means  of  chromic  and  sul- 
phuric acids,  the  former  being  used  to  oxidize  the  S02  of  the  sample.  The  evolved 
gas  is  bubbled  through  a  mixture  of  strong  sulphuric  and  chromic  acids  to  remove 
any  S02  that  may  have  escaped  oxidation.  Fig.  20.  The  C02  is  absorbed  either 
in  caustic  and  weighed  or  is  passed  into  a  standard  solution  of  barium  hydroxide 
and  titrated  according  to  the  standard  procedures  given  under  carbon. 

NOTE.  The  amount  of  the  sample  taken  is  governed  by  the  per  cent  of  Na2CO3 
present. 


414 


SULPHUR 


DETERMINATION  OF  FREE  SULPHUR  IN  A  MIXTURE 

From  1  to  10  grams  of  the  material,  depending  upon  the  amount  of  sulphur 
present,  is  extracted  in  a  Soxhlet  extractor  (see  modified  form  Fig.  66)  with  carbon 

tetrachloride,  or  carbon  bisulphide  (freshly  dis- 
tilled) for  twelve  hours.  The  extract  is  evapor- 
ated to  dryness,  adding  10  cc.  of  bromine-carbon 
tetrachloride  mixture  together  with  15  cc.  of  nitric 
acid.  The  residue  is  taken  up  with  10  cc.  of 
hydrochloric  acid,  diluted  with  150  cc.  of  distilled 
water,  heated  to  boiling  and  the  sulphuric  acid 
precipitated  with  10%  barium  chloride  solution, 
washed,  dried,  ignited  and  weighed  according  to 
the  procedure  for  sulphur. 


BaS04X0.58851  =Ba. 


BaS04X  100X0.13738 
Weight  of  sample 


=per  cent  free  sulphur. 


FIG.  66.— Sanders 

Apparatus. 

desired. 


Sanders'  extraction  apparatus1  has  several 
advantages  that  make  this  apparatus  desirable  for 
laboratory  use,  where  a  number  of  daily  extractions 
are  required.  As  may  be  seen  from  Fig.  66,  by 
simply  removing  the  glass  stopper  D  the  cylinder 
may  be  charged  without  disconnecting  the  appara- 
tus, as  is  necessary  with  the  Soxhlet  type  of  appa- 
ratus. The  extraction  is  carried  on  with  the  traps 
A  and  B  closed,  the  siphon  t-tf  acting  automati- 
cally as  in  case  of  the  Soxhlet.  With  A  closed 
and  B  open  the  apparatus  may  be  used  as  a  reflux 
condenser.  The  solvent  liquid  may  be  drawn  off 
/"[]  ~7  by  opening  A.  With  B  closed  and  A  open  the 

/      /  apparatus  may  be  used  as  a  condenser  and  the 

Extraction  e^her,  chloroform,  carbon  disulphide,  etc.,  distilled 
from  C.    The  globe-shaped  Soxhlet  condenser  may 
be  replaced   by  Allihn's  or  Liebig's  condenser,  if 
The  ball  form,  however,  is  more  compact. 


EVALUATION  OF  SPENT  OXIDE  FOR  AVAILABLE  SULPHUR 

Spent  oxide  is  the  by-product  of  gas  works,  and  refers  to  the  spent  Fe203  used 
in  the  scrubber  for  the  removal  of  hydrogen  sulphide  from  the  gas.  The  FeS, 
as  in  case  of  pyrites,  is  used  in  the  manufacture  of  sulphuric  acid,  and  is  evalued 
by  its  available  sulphur  content. 

Total  Sulphur.    The  oxide  is  sampled,  brought  into  solution  and  the  sulphur 


1910. 


J.  McC.  Sanders,  Proc.  Chem.  Soc.,  26,  227-228,  1910.     The  Analyst,  35,  556, 


SULPHUR  415 

determined  exactly  as  is  given  under  the  standard  method  for  determination  of 
sulphur  in  pyrites  ore. 

Residual  Sulphur.  Two  grams  of  the  material  are  ignited  to  expel  volatile 
sulphur,  €i  porcelain  crucible  being  used.  The  residue  is  treated  with  strong 
hydrochloric  acid  and  after  digestion  on  the  steam  or  water  bath  is  diluted  with 
water  and  filtered.  (If  Si02  is  present  evaporation  to  dryness  is  necessary.) 
Sulphur  is  determined  in  the  nitrate  as  usual. 

Available  Sulphur.  The  per  cent  of  residual  sulphur  is  subtracted  from  the 
per  cent  total  sulphur,  the  difference  being  available  sulphur. 

Iron.  This  may  be  determined  on  an  ignited  sample  according  to  a  standard 
procedure  for  iron.  See  chapter  on  Iron. 


ANALYSIS  OF  BRIMSTONE 

The  impurities  in  brimstone  are  seldom  more  than  a  few  tenths  per  cent.  In 
the  usual  analysis,  moisture,  available  sulphur,  ash,  arsenic,  and  chlorine  are 
required. 

Moisture.  The  powdered  sample,  weighing  50  grams,  is  spread  out  on  a 
watch-glass  and  dried  for  an  hour  at  100°  C.,  then  cooled  in  a  desiccator  and 
weighed. 

Loss  of  weight  in  grams  multiplied  by  2  =per  cent  moisture. 

Available  Sulphur.  Ten  grams  of  the  sulphur  taken  from  the  dried  material 
are  heated  in  a  silica  or  porcelain  dish  until  the  sulphur  ignites.  The  heating  is 
discontinued  during  the  burning  of  the  substance,  but  renewed  for  a  minute  or 
so  after  the  sulphur  has  burned  away.  Loss  of  weight  of  the  cooled  residue  is 
due  to  the  available  sulphur. 

NOTE.     Organic  matter  in  brimstone  is  not  appreciable. 

Ash.  This  is  the  residue  that  remains  in  the  dish.  The  increase  of  weight 
of  the  tared  dish  is  due  to  the  ash. 

Arsenic.  Ten  grams  of  the  material  are  treated  with  30  cc.  of  carbon  tetra- 
chloride  mixture  (3  parts  CCl4+2  parts  Br)  and  after  standing  for  ten  minutes 
25  cc.  strong  nitric  acid  are  added  in  small  portions  (a  watch-glass  covering  the 
beaker  during  the  intervals  of  addition).  The  mixture  is  taken  to  dryness  on  the 
steam  bath.  Water  is  added  and  the  evaporation  repeated.  Arsenic  is  now 
determined  on  the  residue  by  the  Gutzeit  Method  for  arsenic. 

NOTE.    Arsenic-free  reagents  should  be  employed. 

Chlorine.  One  hundred  grams  of  the  brimstone  are  extracted  with  hot  water, 
the  filtered  extracts  oxidized  with  10  to  15  cc.  of  nitric  acid  and  a  few  crystals 
of  ammonium  persulphate  by  boiling  and  treated  with  5  cc.  of  10%  solution 
of  silver  nitrate.  The  solution,  brought  to  boiling,  is  placed  in  a  dark  place  and 
the  silver  chloride  allowed  to  settle.  This  is  now  filtered  off  in  a  weighed  Gooch 
crucible  and  chlorine  calculated  from  the  AgCl. 

AgClX  0.2474  =C1  or  =  0.4078  =NaCl. 


THORIUM 

R.  STUART  OWENS  l 
Th,  at.wt.  232 .4;  sp.gr.  7.7;  11.00;  m.p.  1700°;  oxides  ThO2. 

DETECTION 

(1)  By  means  of  the  spectroscope.    Thorium  shows  lines  of  greatest  intensity 
in  the  arc  spectrum  at  4863.3,  and  4919.9.    In  the  spark  spectrum  lines  of  great- 
est intensity  at  3221.4,  3300.6,  4382.1,  4391.1. 

(2)  By  the  addition  of  H202  to  a  neutral  solution  of  the  nitrates  containing 
ammonium  nitrate.    See  page  418. 

(3)  By  radio  activity.    Thorium  compounds  possess  the  power  of  continu- 
ally emitting  Becquerel  rays  and  radio  active  emanations. 

ESTIMATION 

The  estimation  of  thorium  is  required  chiefly  in  the  fabrication  of  incandescent 
gas  mantles.  Raw  materials  such  as  monazite  P04(Ca,La,Di,Th))  and  thorite 
(ThSi04)  are  generally  used.  The  former  usually  contains  from  2  to  4%  of 
thorium  while  the  latter  runs  as  high  as  81.5%.  Thorium  nitrate  in  a  rather 
impure  state  is  the  chief  intermediate  product.  The  finished  mantles  generally 
contain  99%  Th02  and  1%  Ce02. 

Preparation  and  Solution  of  the  Sample 

"  A  "  Silicates  (as  thorite,  etc.)2  are  decomposed  by  treatment  with  ten  times 
their  weight  of  fuming  hydrochloric  acid.  This  treatment  usually  suffices,  but 
in  cases  where  an  insoluble  residue  still  remains  it  is  fused  with  ten  times  its 
weight  of  sodium  carbonate  in  a  large  platinum  crucible.  The  fusion  is  dissolved 
in  hydrochloric  acid  and  added  to  the  solution  obtained  from  the  first  extraction. 
After  the  silica  and  the  metals  of  the  first  group  are  removed  in  the  usual  way 
the  solution  is  freed  from  H2S  by  boiling.  The  thorium  together  with  the  other 
rare  earths,  calcium,  magnesium,  etc.,  are  then  present  as  chlorides  and  the  neces- 
sary separations  made  as  detailed  under  gravimetric  determination. 

"  B  "  Phosphates  (as  Monazite,  etc.)  (1)  By  Fusion  with  Potassium  Acid 
Sulphate.3  0.5  gram  of  the  finely  pulverized  material  is  mixed  with  10  grams  of 
potassium  acid  sulphate  in  a  large  platinum  crucible,  covered  and  heated  until 
gentle  fusion  takes  place  and  no  further  gas  is  given  off.  Then  ignite  over  free 
flame  for  a  few  minutes,  cool  and  treat  with  a  little  water  and  hydrochloric  acid, 
until  complete  decomposition  takes  place.  Boil  for  a  few  minutes,  allow  to  cool 
and  settle  and  decant  off  the  clear  liquid.  The  residue  is  treated  with  concen- 

1  Research  Chemist,  New  York  City. 

2  Lunge,  "  Technical  Methods  of  Analysis." 

» Benz,  "  Zeit.  fur  angew.  Chem.,  p.  297,  1902. 
416 


THORIUM  417 

trated  hydrochloric  acid.  Dilute  and  filter  from  the  residue  of  silicic  and  tantalic 
acids.  The  filtrate  then  contains  the  thorium,  etc.,  as  chlorides.  Determinations 
are  made  as  detailed  under  gravimetric  methods  following. 

(2)  By*Sulphuric  Acid  Extraction.  The  finely  pulverized  sample  is  mixed  with 
sufficient  H2S04  to  form  a  paste  and  the  mass  heated  gently  at  first,  then  gradually 
increasing  the  heat  to  low  redness.  After  cooling  the  rare  earths  are  dissolved 
from  the  mass  with  cold  water.  The  thorium  is  then  present  in  the  solution  as 
sulphate.  After  removal  of  the  base  metals  in  the  usual  way  determinations  are 
carried  out  as  detailed  below. 

"  C  "  Oxides  (as  gas  mantles,  etc.).  In  the  case  of  gas  mantles  the  organic 
matter  is  first  burned  off  and  the  resulting  oxides  heated  with  three  times  their 
weight  of  strong  H2S04  in  a  porcelain  casserole.  The  mixture  is  heated  on  the 
sand  bath  at  a  temperature  slightly  below  that  required  to  drive  off  fumes  of 
S03  for  a  few  minutes.  After  cooling  the  contents  are  diluted  with  a  small 
quantity  of  water  and  allowed  to  stand  for  several  hours.  The  sulphates  com- 
pletely dissolve  and  the  sample  is  ready  for  the  gravimetric  estimation  as  detailed. 


SEPARATIONS 

(1)  The  hydroxide  is  insoluble  in  an  excess  of  the  precipitant. 

(2)  The  sulphate  forms  double  salts  with  K2S04,  which  are  insoluble  in  an 
excess  of  the  reagent. 

(3)  Thorium  oxalate  readily  forms  a  double  oxalate  with  ammonium  oxalate 
in  an  excess  of  the  reagent. 

(4)  Thorium  is  precipitated  together  with  the  rare  earths  by  oxalic  acid. 

(5)  Thorium  and  cerium  may  be  separated  from  all  of  the  other  earthy  metals 
if  the  hydroxides  recently  precipitated  are  suspended  in  water  containing  4  to  5 
times  their  weight  of  caustic  soda  and  a  current  of  chlorine  gas  passed  through  the 
solution.    All  of  the  other  metals  dissolve.    The  insoluble  residue  left  under 
these  conditions  is  gelatinous  like  aluminum  hydroxide. 

(6)  Thorium  may  be  completely  separated  from  cerium  by  precipitation  with 
H202  from  a  neutral  solution  containing  10%  of  ammonium  nitrate.    The  thorium 
being  precipitated  as  the  peroxide  which  on  ignition  readily  changes  to  the 
oxide  Th02. 


GRAVIMETRIC  METHOD  FOR  DETERMINING  THORIUM 

The  solution  of  the  chlorides  or  sulphates  after  being  freed  from  the  base 
metals,  silica,  etc.,  is  made  nearly  neutral  with  ammonium  hydroxide  and  the 
rare  earths  precipitated  by  the  addition  of  oxalic  acid  in  solution.  In  the  case 
of  monazite  sands  where  0.5  gram  sample  was  used  1  gram  of  oxalic  acid  is  gener- 
ally sufficient,  but  in  any  case  the  precipitate  should  be  allowed  to  settle  and  the 
clear  solution  tested  by  the  further  addition  of  oxalic  acid.  Allow  to  stand  at 
least  twenty-four  hours,  then  filter  and  wash  thoroughly  with  water.  The  pre- 
cipitate is  then  washed  into  a  casserole  and  treated  with  strong  nitric  acid,  adding 
a  little  at  a  time  until  complete  decomposition  has  taken  place.  Then  evaporate 
to  dryness  on  the  steam  bath  to  remove  the  excess  acid.  A  second  evaporation 
with  water  should  follow  in  cases  where  the  precipitate  is  appreciable.  Take  up 


418  THORIUM 

with  10%  ammonium  nitrate  in  sufficient  quantity  to  cause  a  dilution  of  one  part 
of  thorium  nitrate  in  100  parts  of  water.  Heat  to  60°-80°  C.  and  precipitate  the 
thorium  with  20  cc.  of  pure  3%  H202  solution  for  each  100  cc.  solution.  The 
precipitate  which  is  usually  colored  yellow  by  traces  of  cerium  peroxide  is  fil- 
tered at  once,  washed  with  hot  water  containing  ammonium  nitrate.  By  repre- 
cipitation  after  solution  in  nitric  acid  and  neutralizing  the  excess  acid  with 
ammonia  pure  thorium  peroxide  may  be  obtained.  The  precipitate  is  ignited 
in  a  platinum  crucible  and  weighed  as  ThCX 

Thorium  nitrate  is  assayed  by  precipitating  the  thorium  as  peroxide  accord- 
ing to  the  details  given  above. 


DETERMINATION  OF  MINUTE  AMOUNTS  OF  THORIUM 
JOLLY'S  METHOD1 

Solids  after  pulverizing  are  fused  with  an  alkali  carbonate  at  1000°  C.  and 
the  fusion  extracted  with  water.  The  residue  is  dissolved  in  dilute  hydrochloric 
acid  and  set  aside  for  some  days  in  order  to  allow  thorium  disintegration  products 
to  develop.  The  thorium  is  then  determined  by  boiling  off  the  emanations  in  a 
constant  stream  of  air  which  is  passed  through  an  electroscope.  The  rate  of 
discharge  of  the  electroscope  is  compared  with  that  produced  when  a  known 
amount  of  thorianite  was  tested.  It  is  necessary  to  boil  the  solutions  befoie 
testing  to  expel  any  radium  emanation  that  may  be  present. 

1J.  S.C.I.,  8,  Vol.  34,422. 


TIN 

H.  A.  BAKER  x  and  B.  S.  CLARK  2 
Sn,  at.wt.  118.7;  sp.gr.  6.56;  m.p.  232°;  b.p.  2375°;  oxides  SnO2  and  SnO. 

DETECTION 

Tin  is  separated,  together  with  arsenic,  antimony,  gold  and  platinum,  from  the 
hydrogen  sulphide  precipitate  of  the  metals  of  the  second  group,  by  the  action  of 
yellow  ammonium  sulphide.  (Normal  ammonium  sulphide  does  not  readily  dis- 
solve the  sulphides  of  tin.)  If  the  ammonium  sulphide  solution  is  acidulated  with 
hydrochloric  acid  and  the  acid  solution  reduced  with  iron,  antimony,  arsenic, 
platinum  and  gold  are  precipitated  in  the  metallic  form.  The  presence  of  tin, 
which  is  present  as  stannous  chloride,  is  indicated  by  the  reducing  action  of  the 
solution  on  mercuric  chloride,  a  white  precipitate  of  HgCl  or  a  gray  precipitate 
of  Hg  being  thrown  down. 

Reduce  the  hydrochloric  acid  solution  of  the  sample  by  means  of  a  small  piece 
of  iron  wire.  Treat  with  an  excess  of  cold  potassium  hydroxide.  Filter  if  the 
solution  is  not  clear.  Add  an  ammoniacal  solution  of  silver  nitrate.  (One  part 
AgNOj  :  16  parts  NH4OH.)  A  brown  precipitate  of  metallic  silver  indicates  the 
presence  of  tin.  Antimony,  arsenic,  platinum  and  gold  are  precipitated  by  the 
iron,  while  all  of  the  heavy  metals  remaining,  except  lead,  tin,  aluminum,  chro- 
mium, and  zinc,  are  removed  by  the  treatment  with  potassium  hydrate. 

Welch  and  Weber3  recommend  the  following  method  for  detection  of  tin: 
Add  10  cc.  concentrated  hydrochloric  acid  to  the  superficially  dried  precipitated  sul- 
phides from  the  ammonium  sulphide  separation.  Filter  off  arsenic  which  does  not 
decompose.  Dilute  nitrate  to  70  cc.  volume.  Saturate  with  H2S.  Heat  to  expel 
excess  H2S.  Add  5  cc.  of  hydrogen  peroxide  and  heat  until  precipitate  is  redis- 
solved.  Add  5  to  10  grams  of  oxalic  acid  and  pass  H2S  into  the  hot  solution.  Anti- 
mony separates  as  a  red  sulphide.  Filter.  Filtrate  contains  the  tin.  Reduce 
with  test  lead  and  add  mercuric  chloride.  White  or  grayish  precipitate  indicates 
presence  of  tin. 

ESTIMATION 

The  estimation  of  tin  is  required  in  connection  with  the  analysis  of  tin  ores, 
dross,  ashes,  dust,  tin  plate,  alloys  such  as  solder,  canned  foods,  and  general 
analysis. 

Opening  Up  Tin  Ores 

As  the  oxides  of  tin  are  not  readily  soluble  in  acids  the  tin  can  be  most  easily 
removed  by  assay.  Ores,  slags,  dross,  and  ashes  are  first  subjected  to  the  assay 
process.  The  button  obtained  is  then  analyzed  either  volumetrically  or  gravi- 

1  Chief  Chemist,  American  Can  Company. 
2Fir3t  Assistant  Chemist,  American  Can  Company. 
3  Jour.  Am.  Chem.  Soc.,  38,  5,  1011,  1916. 
419 


420  TIN" 

metrically  by  one  of  the  methods  given  below.  Having  the  weight  of  the  button 
and  the  per  cent  of  tin  in  it,  the  per  cent  of  tin  in  the  sample  as  received  can  be 
calculated. 

There  are  two  general  processes  of  assaying,  namely,  the  Cyanide  Process  and 
the  Carbonate  of  Soda  Process. 

The  Cyanide  Process 

The  theory  of  this  method  is  that  the  oxides  are  reduced  to  the  metal  by  the 
action  of  potassium  cyanide,  the  reaction  being  represented  as  follows: 

Sn02+2KCN  =Sn+2KCNO. 

Potassium  cyanide  reduces  other  metals  also  so  that  the  button  obtained  is  not 
pure. 

Procedure.  Take  100  grams  of  the  sample  which  has  been  dried  and  finely 
powdered.  (For  complete  analysis  the  moisture  should  be  determined  in  the 
usual  way.)  Mix  thoroughly  with  four  times  its  weight  of  powdered  potassium 
cyanide.  Place  about  1  in.  of  potassium  cyanide  in  the  bottom  of  a  number  H 
(height  5|  ins.,  diameter  3J  ins.)  Battersea  clay  crucible.  Place  the  mixture 
of  sample  and  cyanide  on  top  of  the  cyanide  in  the  crucible  and  cover  with  enough 
more  cyanide  to  fill  the  crucible  to  within  1  in.  of  the  top. 

Place  the  crucible  in  the  assay  furnace  and  heat  slowly  until  it  has  been 
thoroughly  warmed  and  the  cyanide  begins  to  melt.  Then  increase  the  heat 
gradually  to  a  pure  white,  taking  care  that  the  cyanide  does  not  boil  over.1 
Grasp  the  crucible  with  the  tongs  and  tap  it  gently  on  the  hearth  to  assist  in 
settling  the  metal.  Continue  the  heating  until  all  of  the  organic  matter  has  dis- 
appeared, adding  more  cyanide  from  time  to  time  if  necessary.  Near  the  end  of 
the  process  the  molten  mass  becomes  clear  and  transparent  and  finally  pasty  and 
translucent.  When  this  last  condition  appears,  remove  the  crucible  from  the 
furnace  and  allow  it  to  cool  slowly  at  the  temperature  of  the  room. 

When  cool,  break  the  crucible  and  slag  away  from  the  button.  The  appear- 
ance of  the  button  and  the  slag  immediately  surrounding  it  indicates  whether 
or  not  the  process  has  been  properly  manipulated.  The  button  itself  should  be 
firm  and  compact  and  the  slag  around  it  should  be  white  or  greenish  in  color.  If 
the  button  is  spongy  or  if  the  slag  has  a  dirty  black  color,  the  assay  should  be 
discarded  and  a  new  determination  made,  using  a  fresh  sample.2 

Weight  of  Button  =per  cent  Metal  in  Sample. 

Weight  of  Metal  X  per  cent  Sn 

=per  cent  Sn  in  the  bample. 

.LUU 

NOTE.  This  process  should  be  carried  on  under  a  hood  in  a  segregated  room,  and 
every  precaution  should  be  taken  to  avoid  breathing  the  poisonous  fumes  of  potassium 
cyanioe. 

1  Lunge  advises  that  the  cyanide  should  not  be  allowed  to  boil.     He  uses  a  small 
sample  (10  grams).     "  Technical  Methods  of  Chemical  Analysis  "  1,  Part  1,  p.  256. 
It  is  our  experience  that  satisfactory  results  are  not  obtained  unless  the  extreme  heat 
of  the  furnace  is  used. 

2  See  also  Mellor,  "  A  Treatise  on  Chemical  Analysis,"  p.  270,  1913. 


TIN  421 


The  Sodium  Carbonate  Method 

The  sample  is  fused  with  equal  parts  of  sodium  carbonate  and  sulphur.1  The 
fusion  is  then  dissolved  in  water.  The  tin  goes  into  solution  as  a  thiostannate  of 
sodium.  Iron  and  copper  are  then  separated  by  the  addition  of  sodium  sulphite, 
leaving  arsenic,  antimony  and  tin  in  solution.2 

Other  Methods  of  Opening  Tin  Ores 

Fusion  with  Sodium  Hydrate.  The  sample  of  ore  is  fused  with  ten  times 
its  weight  of  sodium  hydrate.  The  process  is  carried  out  in  an  iron  crucible  and 
then  transferred  to  nickel.  The  fused  mass  is  dissolved  in  water  and  the  tin 
determined  in  the  usual  way.3 

Reduction  by  Means  of  Hydrogen.  The  ore  may  be  reduced  by  strongly 
igniting  in  a  porcelain  tube  in  a  current  of  hydrogen.  The  reduced  metal  is  then 
dissolved  in  hydrochloric  acid  and  the  tin  estimated  by  a  standard  method. 

Fusion  with  Sodium  Peroxide.  J.  Darroch  and  C.  Meiklejohn4  opened  ores, 
slags,  etc.,  by  fusing  with  sodium  peroxide  in  a  nickel  crucible.  They  dissolve  the 
fused  mass  in  hot  water  and  acidify  with  hydrochloric  acid.  The  sample  is  then 
ready  for  the  necessary  separations. 


SEPARATIONS 

Tin  is  separated  from  iron,  aluminum,  chromium,  etc.,  by  the  insolubility  of 
its  sulphide  in  dilute  hydrochloric  acid.  Tin,  together  with  antimony,  arsenic, 
platinum  and  gold,  is  separated  from  lead,  mercury,  copper,  cadmium  and  bismuth, 
by  the  solubility  of  its  sulphide  in  yellow  ammonium  sulphide.  Antimony, 
arsenic,  platinum  and  gold  are  precipitated  as  metals  from  a  hydrochloric  acid 
solution  by  the  action  of  metallic  iron,  leaving  tin  in  solution. 

A  few  special  separations  are  of  interest. 

Tin  and  Lead.  For  the  analysis  of  an  alloy  of  Jead  and  tin,  it  is  usually  prefer- 
able to  make  the  estimations  on  different  samples.  In  this  case,  lead  is  estimated 
by  Thompson's  method  and  the  tin  by  Baker's  modification  of  the  iodine  method. 
Lead  can  also  be  separated  from  tin  by  the  method  given  below  for  the  separation 
of  tin  and  copper. 

Tin  and  Copper.  This  alloy  can  be  dissolved  in  concentrated  hydrochloric 
acid  by  the  addition  of  potassium  chlorate.  A  large  excess  of  ammonium  tar- 
trate  is  added  and  the  solution  made  alkaline  with  ammonia.  Copper  is  then 
precipitated  as  sulphide  by  the  addition  of  hydrogen  sulphide  water  until  no  more 
precipitate  is  formed. 

1Very  finely  divided  carbon  is  sometimes  preferred.  Air  must  not  be  allowed 
to  enter  the  crucible.  Else  decomposition  is  not  complete.  Mellor,  "  A  Treatise  on 
Chemical  Analysis,"  1913,  p  270.  If  carbon  is  used  instead  of  sulphur  the  process 
becomes  one  of  reduction  to  the  metal  and  is  carried  out  in  the  assay  furnace.  The 
details  of  operation  are  similar  to  the  cyanide  process.  The  metal  separates  as  a  button 
in  the  bottom  of  the  crucible.  The  button  contains  other  metals  with  the  tin  and  must 
be  analyzed  further  for  exact  percentages. 

2  Meilor  objects  to  the  method  as  being  tedious  and  dirty. 

»  Low,  "  Technical  Methods  of  Ore  Analysis,"  3d  Ed.,  pp.  208-213,  1908. 

4  Engineering  and  Mining  Journal,  81,  1177,  1906. 


422  TIN 

Tin  and  Antimony.  Antimony  is  separated,  in  the  metallic  form,  from  the 
hydrochloric  acid  solution  of  the  alloy,  by  the  action  of  metallic  iron  placed  in  the 
solution.  The  tin  may  be  determined  by  the  iodine  method  without  the  removal 
of  the  antimony.  If  the  antimony  is  desired,  it  may  be  filtered  off  and  deter- 
mined in  the  usual  way. 

As  in  the  case  of  lead,  it  is  usually  quicker  and  more  accurate  to  make  these 
determinations  on  separate  samples.  The  tin  can  be  determined  by  the  iodine 
method.  The  antimony  can  be  determined  volumetrically  by  various  methods, 
preferably  the  bromate.  (See  chapter  on  Antimony.) 

Tin  and  Phosphorus.  One-half  gram  of  the  alloy  is  dissolved  in  15  cc.  of 
concentrated  hydrochloric  acid  containing  potassium  chlorate.  This  is  diluted 
to  200  cc.  with  water  and  warmed.  It  is  then  treated  for  a  long  time  with 
hydrogen  sulphide  gas.  The  tin  is  all  precipitated  as  sulphide  while  the  phos- 
phorus remains  in  solution. 

Tin  and  Iron  and  Aluminum.  Tin  is  separated  from  iron  and  aluminum  by 
precipitation,  as  sulphide,  from  the  hydrochloric  acid  solution. 

Iron  may  also  be  separated  from  tin  with  copper,  and  lead  by  precipitation 
as  sulphide  from  the  alkaline  ammonium  tartrate  solution. 

Tin  and  Tungstic  Acid.  Donath  and  Mullner l  separate  tin  oxide  from  tung- 
stic  acid  by  mixing  the  sample  with  zinc  dust  and  strongly  igniting  in  a  covered 
crucible  for  fifteen  minutes — boiling  with  dilute  hydrochloric  acid;  oxidizing  with 
potassium  chlorate  to  change  the  blue  tungstic  oxide  to  tungstic  acid  and  diluting 
with  water.  It  is  then  allowed  to  stand  overnight  and  filtered.  The  tin  is  in 
solution. 


GRAVIMETRIC    METHODS    FOR    THE    DETERMINATION 

OF   TIN 

Determination  of  Tin  or  the  Oxides  of  Tin  by  Hydrolysis 

This  method  depends  upon  the  precipitation  of  meta-stannic  acid  in  the 
presence  of  ammonium  nitrate  when  the  stannic  chloride  is  diluted  to  considerable 
volume  and  heated  to  boiling.  It  is  especially  applicable  to  the  determination 
of  tin  oxide  in  tin  paste,  but  may  be  extended  to  all  chloride  solutions  of  the 
higher  oxides.  The  reaction  involved  proceeds  as  follows: 

SnCl4+4NH4N03+3H20 

=H2Sn03+4NH4Cl+4HN03.2 

Stannous  tin  may  be  determined  by  oxidizing  the  chloride  solution  to  the 
stannic  form.  The  method  gives  concordant  results  and  is  rapid. 

Procedure.  For  the  analysis  of  tin  paste  take  a  catch  weight  of  about  10 
grams  for  a  sample.  Dissolve  this  sample  by  heating  it  in  a  No.  6  beaker  with 
300  cc.  of  concentrated  hydrochloric  acid.  Transfer  the  acid  solution  to  a  500-cc. 
volumetric  flask  and  make  up  to  the  mark  with  dilute  (1  :  1)  hydrochloric  acid. 

» J.  Chem.  Soc.  Abate.,  54,  531,  1888. 

2Fresenius,  "Quantitative  Chemical  Analysis,"  1,  406.  1903.  Sodium  sulphate 
may  be  used  instead  of  ammonium  nitrate.  In  that  case  the  reaction  is 


TIN  423 

Take  50  cc.  (approximately  1  gram)  for  a  working  sample.  (If  the  deter- 
mination is  to  be  made  on  tin  paste,  the  sample  may  be  obtained  directly  by  one 
of  the  methods  described  under  Opening  Tin  Ores.)  Dilute  to  100  cc.  with  cold 
water.  Nearly  neutralize  with  strong  ammonia  and  finish  by  adding  drop  by 
drop  from  a  burette,  dilute  ammonia  until  a  slight  permanent  precipitate  is  formed. 
A  large  amount  of  ammonia  will  tend  to  precipitate  iron,  if  present,  as  a  hydrate 
and  to  re-dissolve  the  meta-stannic  acid.1  Add  50  cc.  of  a  saturated  solution  of 
ammonium  nitrate.  Dilute  to  400  cc.  with  boiling  water,  stirring  constantly. 
Bring  the  solution  to  an  incipient  boil,  remove  from  the  flame  and  allow  the 
beaker  to  stand  on  the  steam  bath  until  the  precipitate  has  settled.2  The  solu- 
tion above  the  precipitate  should  be  clear.  Decant  the  supernatant  liquor  through 
a  12|  cm.  S.  &  S.  590  filter  paper  and  wash  the  precipitate  by  decantation 3  six 
times,  using  200  cc.  of  boiling  water  and  allowing  the  precipitate  to  settle  thor- 
oughly at  each  washing.  Transfer  the  precipitate  to  the  filter,  "  cop  "  out  the 
beaker  and  wash  down  with  hot  water  in  the  usual  way.  After  the  precipitate 
has  been  allowed  to  drain,  transfer  to  a  porcelain  or  a  silica  crucible  and  dry 
carefully  on  an  asbestos  board  over  a  Bunsen  flame.4  When  dry,  ignite  at  a  low 
temperature  until  the  filter  paper  has  been  consumed.  Increase  the  heat  and 
finally  blast  to  constant  weight. 

Weight  Sn02 X 100 X  .7877 

. =per  cent  Sn. 

Weight  of  sample 

Determination  of  Tin  as  Sulphide 

The  determination  of  tin  as  a  sulphide  involves  many  difficulties  and  should 
be  avoided  if  possible.  Better  results  can  be  obtained  by  the  volumetric  methods 
and  in  most  cases  without  the  necessity  of  preliminary  separations  of  interfering 
metals.  If  tin  must  be  separated  as  a  sulphide,  better  results  would  be  obtained 
if  the  precipitate  were  dissolved  and  the  tin  content  determined  by  the  iodine 
method. 

Having  the  hydrochloric  acid  solution  of  tin  after  the  interfering  metals  have 
been  separated,  to  precipitate  tin  sulphide,  neutralize  with  ammonia  and  then 
acidify  with  acetic  acid.  Pass  hydrogen  sulphide  until  the  solution  is  saturated. 
Allow  the  precipitate  to  settle  overnight.  Pour  the  supernatant  liquor  off 
through  a  Gooch  crucible  and  wash  the  precipitate  six  times  by  decantation,  using 
a  solution  of  ammonium  nitrate 5  for  wash  water.  Finally  transfer  to  the  crucible 
and  wash  free  from  chlorides.  Dry  the  crucible  in  an  oven  at  100°  C.  Heat  slowly 
in  a  Bunsen  flame  until 6  all  the  sulphur  has  been  expelled.  Care  should  be  taken 
at  this  point  to  avoid  forming  fumes  of  stannic  sulphide  by  heating  too  rapidly. 

1  Some  practice  is  required  to  judge  accurately  the  exact  point  when  the  necessary 
amount  of  ammonia  has  been  added.     The  precipitate  should  appear  white. 

2  If  the  boiling  continues  more  than  a  few  seconds  the  precipitate  will  not  settle 
properly.     Time  will  be  saved  in  this  case  if  the  sample  is  discarded  and  a  new  deter- 
mination commenced. 

3  If  meta-stannic  acid  is  washed  over  onto  the  filter  at  this  point,  clogging  will 
result  and  a  great  deal  of  time  will  be  lost. 

4  Spattering  is  likely  to  occur  here,  causing  loss. 

5  Sulphide  of  tin  separates  as  a  slimy  mass  which  tenaciously  retains  alkaline  salts, 
especially  in  the  absence  of  ammonium  salts.     Mellor,  "  Treatise  on  Chemical  Analysis," 
p.  308,  1913. 

6  Bichloride  of  tin,  Acker  process,  page  425. 


424  TIN 

Remove  the  lid  of  the  crucible,  which  should  be  kept  in  place  during  the  first  part 
of  the  heating,  and  raise  the  temperature  gradually,  finally  finishing  with  the 
blast.  As  sulphuric  acid  is  usually  present  in  some  quantity,  the  crucible  should 
be  cooled  and  a  small  piece  of  ammonium  carbonate  should  be  placed  in  it.  Repeat 
the  ignition  to  drive  out  the  acid.  Cool  and  weigh  as  Sn02.1 


BICHLORIDE  OF  TIN 

Bichloride  of  tin  is  of  great  importance  in  some  of  the  industries,  especially 
the  textile.  It  is  necessary  to  have  exact  analytical  control  of  the  processes  in 
which  this  compound  is  used  in  order  to  insure  uniform  results  and  to  certify  the 
efficiency  and  economy  of  the  process.  Several  methods  have  been  developed  for 
this  purpose.  The  ones  given  below  have  had  practical  application  and  have 
proven  to  be  satisfactory. 

Stannic  Acid  Method. — Hot-water  Precipitation.  In  the  textile  industry 
where  bichloride  of  tin  is  used,  the  efficiency  of  the  process  depends  directly  on 
the  neutrality  of  the  tin  liquor.  If  there  is  more  than  enough  chlorine  present 
in  the  bichloride  solution  to  exactly  oxidize  all  the  tin  to  the  stannic  form,  this 
excess  is  called  "  free  HC1."  If  there  is  not  enough  chlorine  present  to  do  this, 
the  deficiency  is  spoken  of  as  "  basic  HC1."  The  difficulty  of  determining  the 
"  free  "  or  "  basic  "  HC1  is  apparent  when  it  is  known  that  SnCl4  readily  decom- 
poses in  water,  liberating  free  acid.  The  following  method  has  been  developed 
especially  for  this  purpose  and  has  given  good  results. 

The  important  point  in  this  analysis  is  to  determine  whether  the  liquor  has 
"  free  "  HC1  present  or  whether  it  is  "  basic  "  in  nature.  It  has  been  found  that 
hot  water  precipitates  tin  from  the  SnCl4  solution  as  stannic  hydroxide  and  at  the 
same  time  liberates  the  chlorine  as  free  HC1. 

SnCl4+4H20  =Sn(OH)4+4HCl.2 

The  Sn(OH)4  separates  in  a  colloidal  precipitate  which  may  be  filtered  off  and 
the  tin  estimated  as  Sn02.  The  liberated  acid  may  be  determined  in  the  filtrate, 
and  from  this  data  the  "  free  "  or  "  basic  "  HC1  can  be  calculated. 

Procedure.  For  accurate  work  about  20  grams  of  the  liquor  should  be  weighed 
out  in  a  tared  weighing  bottle,  but  for  works  control,  where  time  is  an  important 
factor,  it  is  sufficiently  accurate  to  get  the  specific  gravity  of  the  liquor  by  means 
of  a  hydrometer  and  take  a  measured  quantity  for  a  sample,  calculating  the  weight 
from  these  data. 

Transfer  the  sample  to  a  100-cc.  volumetric  flask.  Make  up  to  volume  with 
cold  distilled  water.  Draw  out  of  this  solution  10  cc.  (approximately  2  grams) 
and  place  in  a  150-cc.  tall  beaker.  Fill  the  beaker  nearly  full  with  boiling  hot 
water,  stirring  continuously  while  the  water  is  being  poured  in.3  Place  the  beaker 
on  top  of  the  steam  bath  and  allow  the  precipitate  to  settle.  Decant  the  liquor 

1  This  method  is  generally  used  only  when  minute  traces  of  tin  are  present,  and 
then  it  is  considered  best  to  dissolve  the  sulphide  in  hydrochloric  acid  and  make  the 
final  determination  by  the  iodine  method.     (See  analysis  of  Canned  Foods  for  "  Salts 
of  Tin,"  page  430.) 

2  Holleman  and  Cooper,  "  Text  Book  9f  Inorganic  Chemistry,"  4th  Ed.,  1912. 

1  If  the  solution  is  not  stirred  at  this  point,  the  precipitate  will  not  settle  and 
trouble  will  be  experienced  during  the  filtering  process. 


TIN  425 

through  an  11  cm.  590  S.  &  S.  filter  l  and  wash  the  precipitate  six  times  by  decanta- 
tion,  using  hot  water.  Now  transfer  the  precipitate  to  the  filter  and  continue 
the  washing  until  1  drop  of  the  filtrate  gives  no  test  for  chlorine.  After  most  of 
the  wate*r  has  drained  out  of  the  filter,  place  the  paper  and  precipitate  in  a  tared 
silica  crucible.  If  there  is  plenty  of  time,  dry  the  contents  of  the  crucible  on  an 
asbestos  board  over  a  low  Bunsen  flame.  In  case  the  analysis  must  be  made  in 
a  hurry,  cover  the  crucible  2  and  heat  it  very  carefully  over  a  low  flame  until  all 
the  water  has  been  driven  out  and  the  paper  has  been  charred.  Then  remove 
the  cover  and  increase  the  heat  to  the  full  Bunsen  flame  and  finally  blast  to  con- 
stant weight.  Weigh  as  Sn02.  Titrate  the  filtrate  with  N/l  NaOH,  using  methyl 
orange  as  the  indicator. 
Calculation: 

Sn02X.7877=Sn 

SnX2.1945=SnCl4 
SnCl4-Sn=  Cl  equiv.  to  Sn 
C1X1.0282=HC1  equiv.  to  Sn 

TT/^1 

•      .  ,.     , —  — ; —     =per  cent  HC1  equiv.  to  Sn 
Weight  ot  sample 

cc.  N/l  NaOH X. 03646 


Weight  of  sample 


=per  cent  HC1  (actual). 


The  difference  between  these  last  two  figures  equals  "  free  "  or  "  basic  "  HC1. 

The  Acker  Process  Method.3  The  theory  of  this  method  is  practically  the 
same  as  that  of  the  hot-water  method,  except  that  in  this  case  the  liberated  acid 
is  neutralized  with  ammonia  before  the  stannic  hydroxide  has  been  filtered  off, 
the  advantage  being  that  any  solution  of  the  stannic  hydroxide,  by  either  acid 
or  alkali,  is  prevented.  The  method  is  not  applicable  for  the  determination 
of  "  free  "  or  "  basic  "  HC1. 

Procedure.  Weigh  out  25  cc.  of  the  bichloride  of  tin  solution.  Transfer 
to  a  500-cc.  flask  (volumetric)  and  make  up  to  volume  with  cold  water.  With  a 
standardized  pipette,  transfer  25  cc.  of  this  solution  to  a  No.  4  beaker.  Dilute 
with  hot  water  to  precipitate  most  of  the  tin  as  stannic  hydrate.  Add  10  drops 
of  phenolacetolin4  (1  gram  of  phenolacetolin  dissolved  in  200  cc.  of  water).  Titrate 
very  carefully  with  dilute  ammonia  until  the  appearance  of  a  rose-red  color.  Boil 
a  few  minutes  on  the  hot  plate.  Allow  the  tin  precipitate  to  settle.  Decant 
through  an  11 -cm.  filter  paper  (S.  &  S.  589,  black  ribbon  brand).  Wash  rapidly 
with  hot  water  without  allowing  the  precipitate  to  cake  down  in  the  filter  until 
the  washings  are  free  from  chlorine.  Dry  the  precipitate  in  an  oven  at  100°  C. 
When  dry,  invert  the  filter  into  a  tared  porcelain  crucible  and  heat  on  a  gauze 
until  the  paper  has  disappeared.  Remove  the  gauze  and  heat  with  the  full 

1  Time  may  be  saved  by  using  a  platinum  cone  with  the  filter  and  applying  a  gentle 
vacuum.     This  can  be  done  with  very  little  danger  of  breaking  the  paper. 

2  This  precaution  must  be  taken,  else  there  will  be  a  loss  by  decrepitation. 

3  Kindness  of  W.  F.  Dorflinger,  chief    chemist  of    Perry-Austin    Manufacturing 
Company. 

4  Luteol  may  be  used  as  indicator,  giving  a  yellow  color  at  the  end-point.     It  is 
slightly  more  delicate  but  much  more  expensive. 


426  TIN 

Bunsen  flame  for  a  few  minutes.    Finally  blast  to  constant  weight.1    Weigh  as 
Sn02. 

Take  the  filtrate  and  washings  and  dilute  them  to  a  volume  of  1000  cc.  Warm 
500  cc.  of  this  solution  and  saturate  it  with  hydrogen  sulphide.  If  any  tin  sepa- 
rates, filter  and  ignite  in  a  tared  porcelain  crucible.  Moisten  with  a  little  nitric 
acid  and  heat  very  slowly  to  drive  out  the  acid.  Ignite  to  constant  weight. 
Weigh  as  Sn02.  Add  this  result  to  the  Sn02  obtained  above  when  calculating  the 
final  result. 

Determination  of  Tin  in  Bichloride  of  Tin  as  Sulphide 

This  method  is  given  as  an  alternative  for  the  Acker  Process  Method  and  may 
be  used  as  a  check  on  that  process.  Uniform  and  concordant  results  have  been 
obtained  by  the  use  of  the  two  methods.2 

Procedure.  Weigh  out  25  cc.  of  bichloride  and  dilute  to  500-cc.  volume 
with  cold  distilled  water.  Take  25-cc.  portions  of  this  solution  for  analysis. 
Dilute  the  sample  to  250  cc.  Saturate  with  hydrogen  sulphide.  Warm  the 
mixture  on  a  hot  plate  at  a  temperature  of  about  65°  C.  until  the  precipitate  is 
coagulated.  Test  the  clear  supernatant  liquor  for  unprecipitated  tin  by  adding 
a  little  hydrogen  sulphide  water.  Filter  on  an  ashless  filter  and  wash  free  from 
chlorides.  Make  the  filtrate  and  washings  up  to  1000  cc.  volume  for  further 
determinations.  Dry  the  tin  sulphide  precipitate  on  the  filter  in  an  oven  at 
100°  C.  Remove  the  precipitate  from  the  paper  as  completely  as  possible.  Ignite 
the  paper  in  a  weighed  porcelain  crucible.  Cool  and  add  a  few  drops  of  nitric 
acid.  Repeat  the  ignition,  heating  very  carefully  at  first  until  the  acid  has  nearly 
all  been  driven  out.  Now  place  the  main  tin  precipitate  in  the  crucible.  Cover, 
heat  gently  for  a  few  minutes,  moisten  with  fuming  nitric  acid,  ignite  very  care- 
fully for  one-half  hour  and  then  blast  for  fifteen  minutes.  Weigh  as  Sn02.3 


VOLUMETRIC  DETERMINATION  OF  TIN 

Volumetric  methods  for  the  determination  of  tin  are  based  upon  the  reducing 
power  of  stannous  compounds.  They  vary  according  to  the  oxidizing  agent 
used  and  the  details  of  manipulation. 

Lenssen's  Iodine  Method  as  Modified  by  Baker.4  This  method  is  a  modi- 
fication of  Lenssen's  Iodine  Method  for  the  determination  of  tin  in  alkaline  solu- 
tions. It  is  especially  applicable  to  the  determination  of  "  salts  of  tin  "  in  canned 
foods  and  to  the  estimation  of  tin  coating  on  tin  plate,  but  is  accurate,  rapid 
and  very  satisfactory  for  alloys  and  general  analysis. 

The  method  is  based  on  the  action  of  iodine  in  the  presence  of  stannous  chloride 
in  hydrochloric  acid  solution.  The  reaction  involved  is: 

SnCl2+I2+2HCl  =SnCl4+2HI. 

1  If  there  has  been  any  reduction,  a  few  drops  of  nitric  acid  may  be  added  and  the 
ignition  repeated,  heating  slowly  at  first  to  prevent  loss  by  decrepitation. 

2  W.  F.  Dorflinger,  Perry-Austin  Manufacturing  Company. 

8  Pure  ammonium  carbonate  may  be  added  at  the  end  to  drive  off  the  sulphuric 
acid  more  rapidly. 

4  The  details  of  this  method  as  given  were  developed  by  Mr.  H.  A.  Baker  at  this 
laboratory  and  have  been  modified  in  accordance  with  the  findings  of  several  years  of 
experience. 


TIN  427 

Iron,  lead  and  antimony  do  not  interfere  with  the  reaction.  Copper  in  small 
quantities  does  not  interfere  with  the  determination,  but  if  it  is  present  in  large 
quantities  as  a  salt,  it  is  likely  to  produce  low  results.  Determinations  made  by 
the  writer1  show  that  results  are  accurate  when  less  than  10%  of  copper,  as  copper 
chloride,  is  present.  Larger  amounts  gave  consistently  low  results.  The  reason 
for  this  fact  centers  around  the  difficulty  of  reducing  all  the  copper  to  the  cuprous 
form.  If  any  CuCl2  is  left  in  the  solution,  it  reacts  with  the  potassium  iodide 
of  the  iodine  solution,  causing  the  precipitation  of  Cul  and  the  liberation  of  free 
iodine. 

CuCl2+2KI  =CuI+2KCl+I. 

Copper  present  as  the  metal  is  not  easily  soluble  or  goes  into  solution  in  the 
reduced  form  and  is  not  likely  to  disturb  the  determination.2 

Solutions — Standard  Tin  Solution.  Dissolve  5.79  grams  of  Kahlbaum's 
C.  P.  tin  in  C.  P.  hydrochloric  acid.  The  solution  of  the  tin  is  effected  by  placing 
about  150  cc.  HC1  in  an  Erlenmeyer  flask,  together  with  the  tin,  and  boiling. 
After  the  tin  has  all  been  dissolved,  transfer  to  a  volumetric  liter  flask  and  make 
up  to  the  mark  with  dilute  hydrochloric  acid. 

1  cc.  =.00579  gramSn. 

Standard  Iodine  Solution.  Dissolve  12.7  grams  of  C.  P.  iodine  in  a  water 
solution  of  20  grams  of  potassium  iodide.  Make  up  to  one  liter  and  standardize 
against  the  standard  tin  solution.  For  tin  plate  analysis,  it  is  convenient  to 
adjust  the  iodine  solution  so  that  1  cc.  equals  exactly  .00579  gram  of  tin.  Then, 
if  a  sample  of  the  plate  having  a  total  surface  of  8  sq.ins.  is  taken,  1  cc.  of  the 
iodine  solution  is  the  equivalent  of  one-tenth  of  a  pound  per  base  box. 

Indicator.    Dissolve  5  grams  of  pure  soluble  starch  in  1  liter  of  water. 

Air-free  Water.  Dissolve  12  grams  of  bicarbonate  of  soda  in  1  liter  of  water. 
Add  20  cc.  HC1  and  allow  the  resulting  gas  to  escape.  Keep  in  a  stoppered  bottle.3 

Procedure.  For  practical  purposes,  take  a  sample,  such  that  the  tin  content 
will  be  between  .2  gram  and  .5  gram.  A  larger  sample  should  be  taken  for 
extreme  accuracy  in  order  to  decrease  the  possible  technical  error.  Place  the 
sample  in  flask  A  of  the  Sellars  apparatus,  Fig.  68,  together  with  100  cc.  of 
cone.  C.  P.  HC1.  Stopper  the  flask  and  connect  tubes  B  and  D,  as  shown  in 
the  illustration.  Boil  until  the  metal  is  all  dissolved.  This  point  is  indicated 
by  the  cessation  of  the  hydrogen  evolution  and  the  appearance  of  large  well- 
developed  bubbles.  If  a  sufficient  amount  of  metallic  iron  is  present  in  the 
sample,  complete  reduction  is  assured.  If  no  iron  was  present  in  the  sample, 
or  if  there  was  not  enough  to  reduce  all  of  the  tin,  make  sure  that  the  tin  is  all 
converted  to  the  stannous  form  by  adding  aluminum  foil  (about  1  gram).  Replace 
the  stopper  and  connect  as  originally.  Boil  until  normal  bubbles  reappear. 
Open  cock  C  to  allow  C024  gas  to  enter.  Place  the  flask  in  cooling  bath  F  with- 
out disconnecting  the  apparatus.  After  the  solution  has  become  thoroughly 

1  Mr.  B.  S.  Clark. 

2  Sulphates  must  not  be  present.     They  tend  to  have  an  oxidizing  effect  and  spoil 
the  results. 

3  There  should  always  be  an  excess  of  bicarbonate  of  soda  present  in  order  that 
carbon  dioxide  will  be  generated  during  the  washing  process,  thus  preventing  air 
from  entering  the  flask  at  any  time  during  the  analysis. 

4  Carbon  dioxide  generated  in  a  Kipp  apparatus  is  likely  to  contain  oxygen.     It 
is  much  better  to  use  liquid  CO2  such  as  can  be  purchased  in  the  open  market. 


428 


TIK 


cool,  disconnect  tubes  Bl  and  D1  from  the  splash  bulbs.  Wash  the  bulbs  with 
"  air  free  "  water,  allowing  the  washings  to  drain  into  the  bulk  of  the  sample. 
Remove  the  stopper  and  wash  down  the  sides  of  the  flask.  About  50  cc.  of  water 
should  be  used  in  the  washing  so  that  the  final  sample  contains  about  25%  HC1. 
Add  5  cc.  starch  solution  and  titrate  with  the  standard  iodine  solution. 


or 


cc.iodineX. 00579X100 
Weight  of  Sample 

cc.  iodine 


=per  cent  Sn, 


10 


= pounds  per  "  base  box."2 


The  Sellars  Apparatus.  This  apparatus  is  a  device  designed  by  Mr.  W.  S, 
Sellars  of  this  laboratory  for  the  purpose  of  facilitating  the  solution  of  tin  samples 
out  of  contact  with  air.  Added  to  this  advantage,  it  is  equipped  with  a  water 


FIG.  67. — Sellars'  Apparatus. 


cooler.    It  is  also  constructed  so  that  the  tubes  and  scrubbing  bottles  can  be 

cleaned  by  flushing  with  water.    The  use  of  this  apparatus  practically  eliminates 

the  usual  sources  of  error  in  connection  with  the  iodine  method,  and  at  the  same 

time   greatly  increases   the   speed   of   the   determination.     Fig.  67  shows  the 

apparatus  in  operation. 

A.1  300-cc.  Erlenmeyer  flask. 

B.1   Connection  with  reduced  pressure  line  from  liquid  carbon  dioxide  cylinder. 

C.1    Glass  manifold. 

D.1  Exit  connection  to  trap. 

E.1   Water  trap  to  prevent  escape  of  HC1  fumes  and  to  prevent  air  from  backing 

into  the  flask. 
F.1    Cooling  tank. 

G.1    Low-pressure  water  wash-out  manifold. 
H.1  Perforated  feed  pipe  to  water  cooler. 
K.1  Outlet  for  cooler. 
L.1   Electric  hot  plate. 
M.1  Lead  drain  pipe. 

1  See  Fig.  68,  page  429. 

' "  Basebox  "—112  sheets  of  tin,  14X20  ins. 


TIN 


429 


Ferric  Chloride  Method.1    This  method  depends  upon  the  reduction  of  ferric 
chloride  by  stannous  chloride  in  hot  solution. 

SnCl2+2FeCl3  =SnCl4+2FeCl2. 


J  I 

FIG.  68. — Sellars'  Apparatus. 

i  C.  Mene,  Dinglers  Journal,  117,  230,  1850.  K.  Pallet  and  A.  Allart,  Bui.  Soc. 
Chim.  (2)  27,  43,  438,  1877.  H.  J.  B.  Rawlins,  Chem.  News,  107,  53,  1913.  H. 
Nelsmann,  Zeit.  Anal.  Chem.,  16,  50,  1877. 


430  TIN 

Antimony,  copper,  arsenic,  bismuth,  mercuric  chloride,  tungsten  and  titanium 
must  be  absent.1 

The  Standard  Solution  of  Ferric  Chloride  is  made  by  dissolving  pure  iron 
wire  in  hydrochloric  acid.  To  standardize  this  solution,  dissolve  1  gram  of  pure 
tin  in  200  cc.  of  C.  P.  HC1,  preventing  air  from  coming  in  contact  with  the  solu- 
tion by  means  of  a  trap,  or  by  passing  carbon  dioxide  over  it.2  Titrate  this 
standard  sample  with  the  ferric  chloride  solution.  The  end-point  is  indicated 
by  the  yellow  color,  due  to  a  slight  excess  of  the  iron  solution. 

Procedure.  Tin  is  first  separated  from  the  interfering  metals  in  the  usual 
way.  If  lead,  copper,  arsenic,  antimony  or  bismuth  are  present,  the  sample  is  first 
reduced,  in  the  hydrochloric  solution,  with  iron  wire.  The  solution  is  then 
filtered.  Lead  and  tin  remain  in  the  filtrate.  Neutralize  by  adding  strips  of 
zinc  until  the  action  ceases.  Tin  and  lead  are  precipitated.  The  clear  liquid 
should  show  no  trace  of  tin  with  hydrogen  sulphide.  Allow  the  precipitate  to 
settle  and  wash  by  decantation,  keeping  the  precipitated  metals  in  the  flask. 
Add  150  cc.  of  concentrated  hydrochloric  acid,  keeping  the  contents  of  the  flask 
protected  from  the  air,  and  bring  to  a  boil.  When  everything  is  dissolved,  titrate 
to  a  yellow  color  with  the  ferric  chloride  solution.3  This  part  of  the  analysis 
should  be  done  very  quickly  to  prevent  oxidation  by  the  oxygen  of  the  air. 


ELECTROLYTIC  DETERMINATION  OF  TIN 

Henz  and  Classen's  Method.  Results  with  this  method  at  this  laboratory 
have  not  been  satisfactory. 

Procedure.  The  tin  is  obtained  as  sulphide,  dissolved  in  sodium  sulphide 
solution  and  acidified  with  dilute  acetic  acid.  It  is  then  heated  to  boiling,  and 
a  boiling  solution  of  equal  parts  of  ammonium  oxalate  and  oxalic  acid  added. 
The  amount  of  this  solution  added  should  be  such  that  the  final  mixture  will 
contain  thirty-five  parts  of  oxalate  and  oxalic  acid  to  one  part  tin.  Use  a  current 
of  .2  to  .3  amp.  having  a  voltage  of  two  to  three  volts.  After  six  hours  add  more 
oxalic  acid  and  continue  the  electrolysis  for  another  twenty-four  hours. 


ESTIMATION  OF  TIN  IN  CANNED  FOOD  PRODUCTS4 

The  tin  in  the  canned  food  products  is  obtained  as  a  sulphide  precipitate  from 
wet  combustion,  with  nitric  and  sulphuric  acids,  of  100  grams  food  product. 

The  clear  sulphuric  acid  residue  is  diluted,  neutralized  with  ammonia  and 
then  rendered  about  2%  acid  with  hydrochloric  acid,  after  which  it  is  thoroughly 
saturated  with  hydrogen  sulphide  gas.  This  precipitate  is  then  filtered  on  a 
Gooch  crucible  with  a  false  bottom.  The  precipitate  may  contain  foreign  sub- 
stances, such  as  lime,  phosphorus,  and  silica,  some  lead,  or  even  small  amounts  of 

1  Lunge,  "  Technical  Methods  of  Chemical  Analysis,"  2,  Part  I,  p.  267. 

2  The  Sellars  apparatus  can  be  used  with  advantage  for  this  purpose. 

8  The  end-point  can  be  easily  identified  by  looking  at  a  blue  Bunsen  flame  through 
the  solution.  When  a  small  quantity  of  ferric  chloride  is  present,  the  flame  appears 
green.  Mellor,  "  A  Treatise  on  Chemical  Analysis,"  p.  310,  1913. 

4  H.  A.  Baker,  Eighth  International  Congress  of  Applied  Chemistry. 


TEST  431 

iron,  but  none  of  these  will  cause  any  trouble  subsequently  in  the  titration,  so  that 
the  labor  of  separating  the  tin  completely  from  the  precipitate  is  obviated. 

After  washing  the  precipitate  three  or  four  times  in  a  Gooch  crucible,  it  is 
transferred  to  a  small  porcelain  dish  by  simply  forcing  out  the  false  bottom  of  the 
Gooch  crucible  and  its  asbestos  pad  and  rinsing  off  the  crucible. 

The  precipitate,  mixed  with  asbestos,  is  now  transferred  to  a  300-cc.  Erlen- 
meyer  flask  and  boiled  with  strong  hydrochloric  acid,  potassium  chlorate  being 
added  from  time  to  time  to  insure  the  complete  breaking  up  and  solution  of  the 
tin  sulphide,  as  well  as  the  elimination  of  the  sulphur.  This  is  accomplished  in 
a  very  few  minutes.  A  few  strips  of  pure  aluminum  foil,  free  from  tin,  are  then 
added  to  the  flask  until  all  of  the  chlorine  is  eliminated.  The  flask  is  then  attached 
to  the  Sellars  apparatus  and  the  determination  completed,  according  to  the 
details  given  under  the  Iodine  Method. 

Gravimetric  Method.1  The  sample  is  first  digested  to  a  colorless  or  pale 
yellow  solution  as  described  under  Baker's  method. 

Add  200  cc.  water  to  the  digested  solution  and  pour  into  a  600-cc.  beaker. 
Rinse  out  the  Kjeldahl  flask  with  three  portions  of  boiling  water  so  that  the  total 
volume  of  the  solution  is  about  400  cc.  Allow  to  cool  and  add  100  cc.  concentrated 
ammonia.  This  amount  of  ammonia  should  render  the  solution  nearly  neutral, 
un'ess  more  than  50  cc.  sulphuric  acid  have  been  used  for  digestion.  The  solution 
should  be  tested  to  see  that  it  is  still  somewhat  acid.  In  case  of  a  large  excess  acid, 
add  ammonia  until  just  alkaline  and  then  make  about  2%  acid  with  hydrochloric 
or  sulphuric  acid.  Pass  in  a  slow  stream  of  hydrogen  sulphide  for  an  hour,  having 
the  covered  beakers  on  an  electric  hot  plate  at  about  95°  temperature.  Allow  to 
digest  on  the  hot  plate  for  an  hour  or  two. 

Filter  the  tin  sulphide  on  an  11-cm.  filter.  Wash  with  three  portions  of 
wash  solution  alternated  with  three  portions  of  hot  water.  The  wash  solution 
is  made  up  of  100  cc.  saturated  ammonium  acetate,  50  cc.  glacial  acetic  acid,  and 
850  cc.  water.  The  filter  papers  used  in  this  method  are  C.  S.  &  S.  No.  590,  white 
ribbon. 

Place  the  filter  and  precipitate  in  a  50-cc.  beaker  and  digest  with  three  succes- 
sive portions  of  ammonium  polysulphide,  bringing  to  a  boil  each  time  and  filtering 
through  a  9-cm.  filter.  Wash  with  hot  water.  Acidify  with  acetic  acid,  digest 
on  the  hot  plate  for  an  hour  and  filter  through  a  double  11-cm.  filter.  Wash  with 
two  portions  of  wash  solution  alternated  with  hot  water  and  dry  thoroughly  in  a 
weighed  porcelain  crucible.  Thorough  drying  is  essential  to  the  success  of  the 
determination.  Ignite  very  gently  at  first  and  later  at  full  heat  of  Bunsen  flame. 
Finally  heat  strongly  with  large  burner,  or  Meker  burner,  having  the  crucible 
partly  covered.  Stannic  sulphide  must  be  gently  roasted  to  the  oxide,  but  the 
oxide  may  be  heated  strongly  without  loss,  due  to  volatilization. 

Weigh  the  stannic  acid  and  convert  to  metallic  tin  by  the  factor  .7877. 

1 E.  L.  P.  Treuthardt,  Association  of  Official  Agricultural  Chemists,  August  15, 1915. 


TITANIUM 

WILFRED  W.  SCOTT  and  L.  E.  BARTON  * 

Tl9mat.wt.  48.1;  sp.gr.  4.5  2;  m.p.  1795°  C.  (±15°)3;  oxides  TiO,  Ti2O,, 

TiO2,  Ti03. 

DETECTION 

The  powdered  ore  is  fused  with  potassium  bisulphate,  KHS04,  until  effer- 
vescence ceases.  The  cooled  mass  is  dissolved  in  dilute  sulphuric  acid  by 
boiling.  Hydrogen  peroxide,  H202,  added  to  this  titanium  solution,  produces 
a  yellow  to  orange  color,  according  to  the  amount  of  titanium  present.  Hydro- 
fluoric acid,  or  fluorides,  destroys  the  color.  Vanadium  also  produces  this  color 
with  hydrogen  peroxide,  but  the  color  is  not  destroyed  by  HF.  The  yellow 
color,  according  to  Weller 4  is  due  to  Ti03  formed. 

Morphine  produces  a  crimson  color  with  solutions  of  titanium  in  sulphuric 
acid. 

Zinc  added  to  hydrochloric  acid  solutions  of  titanium  produces  a  blue  color,8 
tin  a  fine  violet  solution.6 

If  sulphur  dioxide,  S02,  is  passed  into  the  solution  of  titanium  to  reduce  the 
iron,  and  the  slightly  acid  solution  then  boiled,  yellowish  white  metatitanic 
acid,  TiO(OH)2,  is  precipitated. 

Bead  Test  on  Charcoal.  A  small  portion  of  the  powdered  mineral  heated 
on  charcoal  with  microscosmic  salt  and  tin  produces  a  violet-colored  bead  if 
titanium  is  present. 

ESTIMATION 

The  element  is  widely  distributed  in  minerals,  soils,  clays  and  titaniferous 
iron,  FeTi03.  It  is  found  in  granite,  gneiss,  mica,  slate,  syenitic  rocks,  granu- 
lar limestone,  dolomite,  quartz,  feldspars  and  a  large  number  of  other  minerals. 
The  principal  commercial  minerals  are: 

Ilmenite,  FeTi03,  containing  about  52.7%  Ti02. 

Rutile,  Ti02,  containing  90  to  100%  Ti02. 

Titanite,  CaTiSi06,  containing  34  to  42%  Ti02. 

Perovskite,  CaTi03,  containing  about  60%  Ti02  and  5  to  6%  Yt203. 

Titaniferous  ores  of  variable  titanic  oxide  content. 

By  far  the  most  important  application  of  titanium  at  the  present  tune  is  the 
use  of  ferrotitanium  in  the  iron  and  steel  industry.  The  function  of  the  titanium 

1  Chief  Chemist  Titanium  Alloy  Manufacturing  Co. 

2  Hunter,  Eighth  Int.  Congress  Applied  Chem.,  2,  125. 
1  Burgess  and  Waltenburg,  U.  S.  Bureau  of  Standards. 
4  J.  S.  C.  L.  1882,  506-508. 

6Deville,  C.  N.,  4,241. 

•  Cahen  and  Wootton,  "  The  Mineralogy  of  the  Rarer  Metali." 

432 


TITANIUM  433 

is  to  deoxidize  the  steel  and  consequently  to  yield  a  product  free  from  blow- 
holes and  segregation  of  impurities.  In  a  steel  thus  purified  the  natural  strength 
and  resistant  properties  of  the  material  are  developed  in  the  highest  degree. 

Next  in  importance  is  the  application  of  titanium  compounds  to  the  textile 
industry.  For  use  as  a  mordant  in  dyeing,  the  alkali  titanium  salts  of  organic 
acids,  especially  potassium  titanium  oxalate,  have  found  extensive  application. 
The  use  of  titanous  chloride  and  titanous  sulphate  for  bleaching  or  discharging 
colors  is  increasing.  Such  bleaching  agents  are  particularly  applicable  for  silk 
and  wool,  which  are  injured  by  the  action  of  those  bleaching  agents  in  which 
chlorine  is  the  active  element.  Titanium  compounds  have  also  attained  con- 
siderable importance  in  the  dyeing  of  leather. 

Titanium  compounds  are  also  used  for  electric  light  filaments,  arc  carbons, 
ceramics,  fine  brown  glazes,  paint  for  iron  and  steel,  etc. 

Preparation  and  Solution  of  the  Sample 

A  knowledge  of  the  solubility  of  the  element  and  its  oxides  is  of  value  in  the 
solution  of  the  sample. 

Element.  This  is  feebly  soluble  in  cold  dilute  hydrochloric,  or  sulphuric 
acids;  more  readily  so  when  the  acids  are  heated.  It  is  soluble  in  cold,  con- 
centrated hydrochloric  acid;  readily  soluble  in  hot,  concentrated  hydrochloric, 
or  sulphuric  acids.  It  is  scarcely  acted  upon  by  nitric  acid,  but  readily  dissolves 
in  hydrofluoric  acid.  It  is  soluble  by  fusion  with  the  alkalies. 

Oxides.  Ti203  is  soluble  in  concentrated  hydrochloric  or  sulphuric  acids; 
forming,  in  the  latter  case,  a  violet-colored  solution.1  The  oxide  is  insoluble  in 
water  and  in  ammonium  hydroxide. 

Ti02  is  difficultly  soluble  in  concentrated  sulphuric  acid,  less  soluble  if 
Wrongly  ignited.  The  metatitanic  acid,  TiO(OH)2,  requires  strong  hydrochloric 
or  sulphuric  acid  to  effect  solution,  the  orthotitanic  acid,  Ti(OH)4,  however,  is 
readily  soluble  in  hot  or  cold,  dilute  and  concentrated  acids.  From  titanic  solutions 
orthotitanic  acid  is  precipitated  by  ammonia,  the  precipitation  being  assisted  by 
warming.  Boiling  a  slightly  acid  solution  precipitates  the  metatitanic  acid, 
TiO(OH)2.  TiO,  is  soluble  upon  fusing  with  alkalies.  Ti02  is  soluble  in  hydro- 
fluoric acid,  forming  TiF4,  which  is  volatile,  unless  an  excess  of  sulphuric  acid  is 
present  (distinction  from  silica).  The  ignited  oxide  is  best  dissolved  by  fusion 
with  KHS04  and  heating  the  fused  mass  with  dilute  sulphuric  acid  solution.  Titan- 
ous oxides  have  a  black  or  blue  color. 

Salts.  Many  titanic  salts  are  decomposed  in  the  presence  of  water,  pre- 
cipitating titanic  acid,  the  extent  of  the  decomposition  depending  on  the  quantity 
of  water  used.  Titanic  sulphate  is  readily  soluble  in  water  and  the  solution 
is  remarkably  stable  unless  largely  diluted  with  water.  Some  of  the  double 
salts  are  readily  soluble  and  their  solutions  stable,  i.e.,  potassium  titanium 
oxalate. 

General  Considerations 

Solution  of  Steel.  The  sample  may  be  dissolved  in  hydrochloric  acid 
(1:2).  If  a  residue  remains  it  is  treated  with  a  mixture  of  equal  parts  of 
hydrofluoric  and  sulphuric  acids  and  a  few  drops  of  nitric  acid,  in  a  platinum 

i  Ebelmen,  A.  Ch.,  (3),  20,  392,  1847. 


434  TITANIUM 

dish,  and  the  mixture  evaporated  to  sulphuric  anhydride  fumes  and  to  complete 
expulsion  of  hydrofluoric  acid.  The  colorimetric  procedure  is  now  used  for 
estimating  titanium.  For  determination  of  titanium  in  hydrochloric  acid  solution 
see  page  443. 

NOTE.  Titanium  in  steel  treated  with  ferrq  carbon-titanium  exists  in  two  condi- 
tions: (1)  Titanium  soluble  in  hydrochloric  acid.  (2)  Titanium  insoluble  in  hydro- 
chloric acid.  Of  the  very  small  amount  of  titanium  in  treated  steel  the  greater  part 
will  usually  be  found  in  the  second  form.  When  the  amount  of  titanium  in  the  steel 
is  exceedingly  small,  the  soluble  titanium  frequently  exceeds  the  insoluble,  and  it  is 
then  occasionally  desirable  to  determine  also  that  existing  in  the  second  form. 

Alloys.  These  are  dissolved  in  concentrated  nitric  acid,  aqua  regia  or  a 
mixture  of  the  dilute  acids.  Should  nitric  acid  be  used,  the  excess  is  expelled 
by  evaporation  to  dryness  with  hydrochloric  acid.  The  metals  of  the  hydrogen 
sulphide  group  are  removed  in  an  acid  solution  by  precipitation  with  H2S,  and 
titanium  determined  colorimetric  ally  in  the  filtrate. 

Ores.  One  to  5  grams  of  the  ore  are  treated  with  10  to  50  cc.  of  a  mixture 
of  sulphuric  and  hydrofluoric  acids  (1  to  5),  a  few  drops  HN03  added,  and  the 
solution  evaporated  to  fumes  to  expel  HF.  If  a  residue  remains  upon  taking 
up  with  water  containing  a  little  sulphuric  acid,  it  is  filtered  off  and  fused  with 
KHS04  as  directed  under  the  fusion  method. 

Fusion  Method  for  Ores.  The  finely  powdered  sample  is  fused  with  four 
to  five  times  its  weight  of  potassium  bisulphate,  KHS04,  and  the  cooled  fusion 
dissolved  with  dilute  sulphuric  or  hydrochloric  acid.  In  the  presence  of  silica 
potassium  fluoride  is  added  to  assist  in  the  decomposition  of  the  material. 

(See  Analysis  of  Titaniferous  Ores,  page  445.) 

Titaniferous  Slags.  One-half  gram  of  the  finely  ground  sample  is  decomposed 
in  a  platinum  dish  by  a  mixture  of  5  cc.  water,  5  cc.  concentrated  sulphuric 
acid,  2  cc.  nitric  acid,  and  10  cc.  of  hydrofluoric  acid,  the  reagents  being  added 
in  the  order  named.  The  solution  is  evaporated  rapidly  to  S03  fumes  to  expel 
fluorides  and  the  excess  sulphuric  acid  until  residue  is  left  nearly  dry.  After 
cooling  it  is  taken  up  with  40  cc.  of  dilute  hydrochloric  acid  (1  :  3),  which  will 
give  a  clear  solution  containing  all  the  constituents  of  the  slag  except  silica,  which 
has  been  volatilized  as  SiF4.  The  solution  is  diluted  to  200  cc.  with  cold  water. 
Iron  and  titanium  are  precipitated  by  ammonia  in  slight  excess  and  filtered 
at  once  without  boiling.  The  precipitate  is  dissolved  in  cold  dilute  hydrochloric 
acid  and  reprecipitated  with  ammonia.  Titanium  is  now  separated  from  iron 
by  reducing  iron  with  S02  and  precipitating  titanium  from  a  boiling  acid  solu- 
tion as  described  on  page  436. 


SEPARATIONS 

Details  of  the  isolation  of  titanium  are  given  in  the  methods  for  its  esti- 
mation. 

Separation  of  Titanium  from  the  Alkaline  Earths,  etc.  The  hydroxide  is 
precipitated  when  a  titanium  solution  containing  ammonium  chloride  is  treated 
with  ammonium  sulphide,  whereas  barium,  strontium,  calcium  and  magnesium 
remain  in  solution.  Titanium  hydroxide  may  be  precipitated  by  making  the 
solution  containing  titanium  slightly  ammoniacal  with  HN4OH. 

Separation  from  Copper,  Zinc,  Aluminum   Iron,  etc.     Titanium  is   pre- 


TITANIUM  435 

cipitated  from  a  slightly  acid  solution  1  by  boiling,  passing  sulphur  dioxide  through 
the  solution  to  keep  the  iron  reduced  and  prevent  its  precipitation. 

Separation  from  the  Bivalent  Metals,  Manganese,  Nickel,  Cobalt,  Zinc. 
Titanium  is  precipitated  along  with  aluminum  and  iron  by  hydrolysis  of  its 
acetate  in  a  hot,  dilute  solution,  whereas  manganese,  nickel,  cobalt  and  zinc 
remain  in  solution.  Details  of  the  basic  acetate  method  are  given  on  page  260. 

Separation  of  Titanium  from  Aluminum.  Small  amounts  of  titanium 
from  large  amounts  of  aluminum.  (One  part  Ti  to  50  parts  Al.)  Cupferron, 
C6H5(NO)N'ONH4  added  to  a  decidedly  acid  solution  containing  titanium  and 
aluminum  precipitates  titanium,  but  not  aluminum.  The  precipitate  is  washed 
by  decantation  and  then  on  the  filter  with  very  dilute  hydrochloric  acid  to  remove 
traces  of  aluminum.  The  procedure  affords  a  separation  of  titanium  from 
chromium,  nickel,  cobalt,  manganese,  etc.  Copper  and  iron,  however,  precip- 
itate with  the  titanium,  if  present  in  the  solution.  The  yellow  titanium  salt  has 
the  composition  (C6H5(NO)NO)4Ti.2 

Separation  of  Titanium  from  Iron.  See  Gravimetric  Method  for  Deter- 
mination of  Titanium,  Modified  Gooch  Method,  below. 


GRAVIMETRIC  METHODS 
Gravimetric  Determination  of  Titanium.    Modified  Gooch  Method  3 

This  method  is  applicable  to  minerals  and  metallurgical  products  that  are 
comparatively  high  in  titanium.  The  method  provides  for  the  separation  of 
titanium  from  iron  and  from  aluminum  and  phosphoric  acid  with  which  it  com- 
monly occurs.  The  procedure  as  proposed  by  F.  A.  Gooch  and  modified  for 
non-aluminous  rocks  by  Wm.  M.  Thornton  has  been  found  by  the  author4  to 
give  reliable  results.  The  details  of  the  method  with  a  few  slight  changes  found 
to  be  advantageous  are  given  below.  Iron  is  separated  from  titanium  by  precip- 
itation as  a  sulphide  in  presence  of  tartaric  acid,  the  organic  acid  is  destroyed 
by  oxidation  and  titanium  precipitated  from  a  boiling  acetic  acid  solution.  In 
the  presence  of  alumina  and  phosphoric  acid  the  impure  precipitate  is  fused 
with  Na2C03  and  the  impurities  leached  out  with  boiling  water.  In  presence  of 
zirconium,  titanic  acid  is  incompletely  precipitated.  Hillebrand's  modification 
for  the  removal  of  zirconium  is  given  in  the  notes. 

Procedure.  Preparation  of  the  Sample.  Ores  High  in  Silica.  These  may 
be  decomposed  by  taking  to  S03  fumes  with  a  mixture  of  10  to  15  cc.  of  50% 
hydrofluoric  acid,  HF,  and  3  to  4  cc.  of  concentrated  sulphuric  acid  per  gram 
of  sample. 

Oxides.  Decomposed  by  fusion  with  sodium  or  potassium  bisulphate.  The 
fusion  is  dissolved  in  10%  sulphuric  acid,  keeping  the  volume  as  small  as  possible. 
The  sample  should  contain  not  over  0.2  gram  titanium. 

Precipitation  of  Iron.  To  the  solution  containing  titanium,  tartaric  acid,  equal 
to  three  times  the  weight  of  the  oxides  to  be  held  in  solution,  is  added.  This  should 

Acidity  exactly  0.5%  is  best  according  to  Levy,  C.N.,  56,  209. 

2  Analyst,  36,  520,  1912,  method  of  J.  Bellucci  and  L.  Grassi. 

3  F.  A.  Gooch,  Proc.  Am.  Acad.  Arts  and  Sci.,  New  Series,  12,  435.     Wm.  M. 
Thornton,  C.  N.,  107,  2781,  123,  1913. 

4  W.W.Scott. 


436  TITANIUM 

not  exceed  1  gram  of  the  organic  acid,  as  the  subsequent  removal  of  larger  amounts 
would  be  troublesome.  H2S  is  passed  into  the  solution  to  reduce  the  iron  and 
NH4OH  added  to  slight  alkalinity  followed  by  a  further  treatment  with  H2S  to 
completely  precipitate  FeS.  The  solution  should  be  faintly  alkaline  (litmus) 
otherwise  more  ammonia  should  be  added.  After  nitration  and  washing  of  the 
ferrous  sulphide  with  very  dilute  and  colorless  ammonium  sulphide,  the  titan- 
ium is  entirely  in  the  iron-free  filtrate. 

Oxidation  of  Tartaric  Acid.  Since  titanium  cannot  be  precipitated  by  any 
reagent  in  the  presence  of  tartaric  acid,  the  organic  acid  is  oxidized  by  addition 
of  15  to  20  cc.  of  concentrated  sulphuric  acid  to  the  sample  placed  in  a  500-cc. 
Kjeldahl  flask.  The  solution  is  evaporated  to  incipient  charring  of  the  tartaric 
acid.  After  cooling  slightly,  about  10  cc.  of  fuming  nitric  acid  are  added  cau- 
tiously, a  few  drops  at  a  time,  and  when  the  violent  reaction  has  subsided  the 
flask  is  heated  gradually  (hood),  a  vigorous  reaction  taking  place  accompanied 
by  much  effervescence  and  foaming  with  evolution  of  copious  brown  fumes. 
The  organic  matter  gradually  disappears,  the  effervescence  becomes  steady  and 
finally  ceases  and  white  fumes  of  S03  are  given  off.  The  solution  is  cooled  and  the 
pale  yellow  syrup  poured  into  100  cc.  of  cold  water,  the  flask  washed  out,  adding 
the  rinsing  to  the  main  solution.  If  cloudy,  the  solution  is  filtered. 

Precipitation.  Ammonia  is  added  until  the  solution  is  nearly  neutral,  a 
point  where  the  solution  is  slightly  turbid,  the  precipitate  dissolving  upon  vigor- 
ous stirring.  If  a  trace  of  iron  is  suspected  about  1  cc.  of  10%  ammonium 
bisulphate  is  added.  Five  cc.  of  glacial  acetic  acid  followed  by  15  grams  of 
ammonium  acetate  or  its  equivalent  in  solution  is  added  and  the  volume  of  the 
solution  made  up  to  about  350  cc.  The  solution  is  brought  rapidly  to  boiling 
and  maintained  in  ebullition  for  about  three  minutes.  The  titanium  will  pre- 
cipitate in  white  flocculent  and  readily  filterable  condition.  The  precipitate 
is  washed  first  with  water  containing  acetic  acid  and  finally  with  pure  water. 
The  filter  and  the  precipitate  are  ignited  cautiously  over  a  low  flame  and  finally 
blasted  over  a  M6ker  blast  for  twenty  minutes.  The  residue  is  weighed  as 
Ti02. 

In  the  presence  of  large  amounts  of  alumina  and  phosphoric  acid,  the  residue 
above  obtained  is  fused  with  sodium  carbonate  in  a  platinum  dish  and  the  fusion 
leached  by  boiling  with  pure  water.  Alumina  and  phosphoric  acid  go  into  solu- 
tion as  soluble  sodium  salts  and  titanium  oxide  remains  insoluble  in  the  residue. 

Ignited  insoluble  residue  =Ti02. 

NOTE.  Titanium  may  be  separated  from  aluminum  by  fusing  the  residue  with 
potassium  acid  sulphate,  KHSO4,  and  precipitation  of  titanium  in  an  acid  solution 
by  cupferron.  A1203  is  in  solution. 

Determination  of  Titanium  in  Ferro  Carbon  Titanium. 
Gravimetric  Method  1 

Into  a  6-in.  porcelain  evaporating  dish,  weigh  0.6  gram  (factor  weight)  of 
alloy. 

Dissolve  in  a  mixture  of  15  cc.  of  dilute  sulphuric  acid  (one  acid  to  one  water), 
5  cc.  of  nitric  acid,  and  10  cc.  of  hydrochloric  acid.  Evaporate  to  fumes  of  sul- 
phuric anhydride. 

1  Methods  of  analysis  used  in  the  laboratories  of  the  Titanium  Alloy  Manufacturing 
Company. 


TITANIUM  437 

Cool  and  take  up  by  boiling  with  50  to  60  cc.  of  water  and  5  to  10  cc.  hydro- 
chloric acid.  Filter  into  a  500-cc.  beaker  and  wash  the  residue  with  hot  water 
and  dilute  hydrochloric  acid. 

In  tne  nitrate  precipitate  iron  and  titanium  by  ammonia  in  slight  excess. 
Filter  without  boiling  and  wash  precipitate  twice  on  filter  with  hot  water. 

Reject  nitrate.  Dissolve  the  precipitate  in  a  very  little  dilute  hydrochloric 
acid,  washing  the  filter  with  hot  water  and  collecting  the  solution  and  washings 
in  the  original  beaker. 

Nearly  neutralize  the  solution  with  ammonia  or  ammonium  carbonate;  dilute 
to  300  cc.;  saturate  with  sulphur  dioxide  gas,  and  boil  until  titanic  acid  is  pre- 
cipitated and  the  solution  smells  faintly  of  sulphur  dioxide. 

Filter  and  wash  with  hot  water  and  dilute  sulphurous  acid. 

Dry,  ignite,  and  weigh  as  titanic  oxide. 

Since  the  factor  weight  of  sample  has  been  used,  one  milligram  of  titanic  oxide 
is  equal  to  0.1%  metallic  titanium. 


VOLUMETRIC  METHODS 

The  Determination  of  Titanium  by  Reduction,  Addition  of  Ferric 
Salt  and  Titration  of  Reduced  Iron  with  Potassium  Per= 
manganate  1 

Principle.  Titanic  acid  is  reduced  by  means  of  zinc,  an  excess  of  ferric  sul- 
phate is  added  and  the  ferrous  salt,  formed  by  reduction  by  titanous  salt,  is 
titrated  with  standard  permanganate.  The  method  is  more  accurate  than 
direct  titration  of  the  titanous  salt  with  permanganate. 

Reaction.     Ti2(S04)3+Fe2(S04)3  =  2Ti(S04)2+£FeS04, 
or    TiCl3+FeCl3=TiCl4+FeCl2.2 

Preparation  of  the  Sample 

Procedure.  One  to  2  grams  of  the  ore  is  decomposed  by  hydrofluoric  and 
sulphuric  acids  or  by  fusion  with  potassium  bisulphate  or  a  combination  of  the  two 
according  to  the  methods  already  described.  Members  of  the  H2S  group,  if 
present,  may  be  removed  by  H2S.  If  iron  is  present  it  may  be  determined  by 
boiling  off  the  H2S  in  the  filtrate  containing  Fe,  Ti,  etc.,  and  allowance  made  in 
the  titration  for  titanium.  If  other  interfering  elements  are  present  in  this 
filtrate,  titanic  acid  may  be  precipitated  by  boiling  the  slightly  acid  solution 
(sulphurous  acid)  according  to  directions  given  in  the  gravimetric  method. 
The  washed  oxide  is  dissolved  in  strong  H2S04  and  diluted  as  directed  below. 

Reduction.  The  solution  is  washed  into  a  100-cc.  flask  and  diluted  with 
water  so  that  it  will  contain  10%  of  sulphuric  acid.  This  acid  holds  titanic  acid  in 
solution  and  at  the  same  time  is  insufficient  to  oxidize  the  reduced  titanium 
oxide.  Sufficient  zinc  to  cause  complete  reduction  is  added  and  a  rubber  stopper 
carrying  a  Bunsen  valve  tube  and  a  thistle  tube  with  glass  stop-cock  is  inserted 

1 H.  D.  Newton,  A.  J.  Sc.  (4),  25,  130.  A.  F.  Gooch,  "  Methods  in  Chemical 
Analysis." 

2  T.  R.  Ball  and  G.  McP.  Smith,  Jour.  Am.  Chem.  Soc.,  36,  1838,  1914. 


438  TITANIUM 

in  the  neck  of  the  flask.  The  evolved  hydrogen  expels  the  air  and  reduces  the 
titanic  oxide  to  the  titanous  form.  Iron  if  present  is  also  reduced.  Gentle 
heat  is  applied  until  the  excess  of  zinc  dissolves.  The  solution  is  cooled  and  an 
excess  of  ferric  sulphate  added  through  the  thistle  tube,  followed  immediately 
by  cold  distilled  water  until  the  flask  is  filled  to  the  neck.  The  contents  of  the 
flask  is  poured  into  a  No.  6  beaker  containing  150  to  200  cc.  of  cold  distilled 
water  and  the  ferrous  iron,  formed  by  the  reducing  action  of  titanous  salt,  is 
titrated  with  N/10  KMn04  solution. 

One  cc.  N/10  KMn04  =0.00481  gram  Ti,     or    0.00801  gram  Ti02. 


Volumetric   Method   by  Reduction   of  Titanium   and   Titration 

with  a  Ferric  Salt 

The  following  volumetric  method  recommended  by  the  Titanium  Alloy  Mfg. 
Co.,  is  essentially  that  described  by  P.  W.  &  E.  B.  Shimer,  Proceedings  of 
Eighth  International  Congress  of  Applied  Chemistry,  the  method  hereafter 
described  differing  principally  in  the  form  of  reductor  and  also  in  a  few  details 
of  operation. 

Reagents.    Standard  ferric  ammonium  sulphate  solution. 

Dissolve  30  grams  of  ferric  ammonium  sulphate  in  300  cc.  water  acidified 
with  10  cc.  of  sulphuric  acid;  add  potassium  permanganate  drop  by  drop  as 
long  as  the  pink  color  disappears,  to  oxidize  any  ferrous  to  ferric  iron;  finally 
dilute  the  solution  to  1  liter. 

Standardize  this  solution  in  terms  of  iron.  The  iron  value  multiplied  by 
1.4329  gives  the  value  in  titanic  oxide  (Ti02);  and  the  iron  value  multiplied  by 
0.86046  gives  the  value  of  the  solution  in  terms  of  metallic  titanium. 

Indicator.    Saturated  solution  of  potassium  thiocyanate. 

Reductor.  As  a  reductor  a  500-cc.  dispensing  burette  is  used.  The  inter- 
nal dimensions  of  the  burette  are  If  by  22  ins. 

The  reductor  is  charged  with  1200  grams  of  20-mesh  amalgamated  zinc, 
making  a  column  about  12  ins.  high  and  having  an  interstice  volume  of  about 
135  cc.  This  form  of  reductor  is  connveient,  and  when  used  as  hereafter  described 
is  adapted  to  maintaining  hot  solutions,  which  is  essential  for  complete  reduction 
of  the  titanium. 

The  reductor  is  connected  to  a  liter  flask  for  receiving  the  reduced  titanium 
solution,  through  a  three-hole  rubber  stopper  which  carries  also  an  inlet  tube 
for  carbon  dioxide  supply,  and  outlet  tube  for  connecting  with  the  suction  pump. 

Procedure.  Determination  of  Titanium  in  Ferro-Carbon  Titanium.  One- 
half  gram  of  sample  is  dissolved  in  a  6-in.  porcelain  evaporating  dish  in  a  mix- 
ture of  10  cc.  water,  10  cc.  sulphuric  acid,  5  cc.  of  hydrochloric  acid,  5  cc.  of 
nitric  acid. 

The  solution  is  evaporated  to  fumes  of  sulphuric  anhydride;  taken  up  by 
boiling  with  50  cc.  water  and  10  cc.  of  hydrochloric  acid;  filtered  and  washed  with 
hot  water  and  hydrochloric  acid. 

The  filtrate  and  washings  should  be  about  100  cc.  in  volume. 

The  reductor  is  prepared  for  use  by  first  passing  through  it  a  little  hot 
dilute  sulphuric  acid  followed  by  hot  water,  finally  leaving  sufficient  hot  water 
in  the  reductor  to  fill  to  the  upper  level  of  the  zinc. 

The  hot  titanic  solution  prepared  as   described  above  is  now  introduced, 


TITANIUM  439 

about  100  cc.  of  water  being  drawn  from  the  reductor  into  the  original  beaker 
to  bring  the  solution  to  about  the  upper  level  of  the  zinc.  The  water  thus 
removed  will  not  contain  any  titanium  if  the  operation  has  been  conducted  as 
described;  but  it  serves  as  a  safeguard  and  is  also  convenient  to  acidify  this  water 
with  10  cc.  of  sulphuric  and  reserve  it  on  the  hot  plate  to  be  used  as  an  acid  wash 
after  the  reduction  of  the  sample  solution. 

The  titanium  solution  is  allowed  to  remain  in  the  reductor  for  ten  minutes. 

While  the  solution  is  being  reduced  the  receiving  flask  is  connected  to  the 
reductor  and  the  air  completely  displaced  by  carbon  dioxide,  conveniently  drawn 
from  a  cylinder  of  the  liquefied  gas. 

When  the  reduction  is  complete  the  receiving  flask  is  connected  with  the 
suction  pump,  and  while  still  continuing  the  flow  of  carbon  dioxide  the  reduced 
solution  is  drawn  out,  followed  by  the  reserved  acid  wash  and  then  three  or 
four  100-cc.  washes  with  hot  water.  The  displacement  of  the  sample  solu- 
tion and  washing  of  the  zinc  is  so  regulated  by  means  of  the  stop-cock  that  the 
reductor  is  always  filled  with  solution  or  water  to  the  upper  level  of  the  zinc. 

When  the  washing  is  complete,  gradually  release  the  suction  to  prevent  air 
being  drawn  back  into  the  receiving  flask.  ^ 

Disconnect  the  flask,  add  5  cc.  of  potassium  thiocyanatd^olution  as  indicator 
and  titrate  immediately  with  standard  ferric  ammonium  sulphate  solution, 
adding  the  solution  rapidly  until  a  brownish  color  is  produced  which  will  remain 
for  at  least  one  minute. 

The  method  is  also  well  adapted  for  determining  titanium  in  other  titanium 
products,  suitable  means  being  employed  for  bringing  the  titanium  into  sul- 
phuric acid  solution. 

Colorimetric  Determination  of  Titanium  with  Hydrogen  Peroxide 

Preliminary  Considerations.  Hydrogen  peroxide  added  to  acid  solutions 
of  titanium  produces  a  yellow  to  orange  color,  the  depth  of  the  color  depending 
upon  the  amount  of  titanium  present.  Upon  this  fact  the  method  is  based. 
It  is  of  especial  value  in  determining  small  amounts  of  titanium,  as  it  is  possible 
to  detect  less  than  one  part  of  the  metal  per  hundred  thousand  parts  of  solu- 
tion. Color  comparisons  can  best  be  made  on  samples  containing  0.05  to  5 
milligrams  of  the  element;  larger  amounts  produce  too  deep  a  color  for  accurate 
comparison. 

The  following  interferences  should  be  made  note  of,  e.g.,  molybdenum,  vana- 
dium and  chromium  also  produce  a  color  that  would  lead  to  error.  Iron  if 
present  to  the  extent  of  4%  or  over  produces  a  color  that  must  be  allowed  for; 
e.g.,  0.1  gram  Fe203  in  100  cc.  of  solution  is  equivalent  to  about  0.2  gm.  of  TiOa 
oxidized  by  H202  in  100  cc.  of  solution.  Fluorides  destroy  the  color,  hence  must 
be  absent.1  Phosphoric  acid  and  alkali  sulphates  have  a  slight  fading  action,2 
hence  must  be  allowed  for  by  adding  equivalent  amounts  to  the  standard  if 
they  are  present  in  the  sample.  The  addition  of  an  excess  of  sulphuric  acid  partly 
counteracts  the  action  of  phosphates  or  alkali  sulphates.3  The  color  intensity 
is  increased  by  increase  of  temperature,  hence  the  standard  and  the  sample 

1 W.  F.  Hillebrand,  J.  A.  C.  S.,  17,  718,  1895.    C.  N.,  72,  158,  1895. 

2  P.  Faber,  Zeit.  an.  Chemie,  46,  277,  1907. 

3  H.  E.  Merwin,  A.  J.  S.  (4),  28,  119,  1909. 


440 


TITANIUM 


examined  should  have  the  same  temperature.1  Since  metatitanic  acid  produces 
no  color  with  hydrogen  peroxide,  its  formation  must  be  prevented;  the  presence 
of  5%  of  free  H2S04  accomplishes  this.2 

The  procedure  is  very  satisfactory  for  magnetic  or  other  iron  ores.  It  is 
fully  as  accurate  as  the  best  gravimetric  method  and  very  much  more  rapid. 

Solutions  Required.  Standard  Titanium  Solution.  This  may  be  prepared 
by  precipitations  of  Ti02  from  K2TiF6  according  to  the  gravimetric  procedure 
and  purification  by  solution  and  reprecipitation,  the  fluorine  being  first 
removed  by  taking  the  compound  to  fumes  with  H2S04  and  then  hydrolyzing 
titanium  with  NH4OH.  The  washed  precipitate  is  ignited  over  a  Me"ker  flame 

for  fifteen  minutes,  cooled  in  a 
desiccator  and  placed  in  tightly 
stoppered  bottle,  since  TiOa  is 
slightly  hydroscopic. 

0.5  gram  of  Ti02  is  fused  with 
about  twenty  tunes  its  weight  of 
KHS04  in  a  platinum  dish,  keep- 
ing at  fusion  heat  until  the  oxide 
has  dissolved.  A  high  tempera- 
ture is  not  advisable.  The  fusion 
is  dissolved  in  5%  sulphuric  acid 
by  gently  heating.  The  solution 
washed  into  a  500-cc.  graduated 
flask  is  made  up  to  volume  with 
5%  H2S04.  One  cc.  contains 
0.001  gram  Ti02,  or  0.0006  gram 
Ti. 

Hydrogen  Peroxide.  Thirty 
per  cent  solution.  If  this  is  not 
available  sodium  peroxide  dis- 
solved in  dilute  sulphuric  acid 
will  do. 

Apparatus.  Colorimeter — Fig. 
69.  Also  see  Fig.  43,  page  245. 
Preparation  of  the  Sample.  The  solution  of  the  sample  having  been 
obtained  by  one  of  the  procedures  given  under  Preparation  and  Solution  of  the 
Sample,  the  element  may  be  determined  according  to  the  procedure  given 
below.  If  interfering  substances  are  present,  e.g.,  comparatively  large  amounts 
of  iron,  or  if  tungsten,  vanadium  or  chromium  are  present  it  will  be  necessary 
to  precipitate  titanic  acid  by  adding  ammonium  hydroxide  to  the  boiling  solu- 
tion as  directed  under  the  gravimetric  determination  of  the  element.  The 
washed  precipitate  is  dissolved  in  sulphuric  acid. 

Procedure.  The  sulphuric  acid  solution  of  titanium  should  contain  5%  of 
free  sulphuric  acid.  It  is  poured  from  the  beaker  in  which  solution  was  effected 
into  a  100-cc.  Nessler  tube,  2  cc.  of  hydrogen  peroxide,  30%  solution  are  added 
and  the  volume  made  up  to  100  cc.  with  5%  sulphuric  acid.  The  standard  is 
prepared  by  pouring  40  or  50  cc.  of  5%  sulphuric  acid  into  a  second  100-cc. 
Nessler  tube,  adding  2  cc.  of  30%  hydrogen  peroxide,  H202,  followed  by  sufficient 

1  Hillebrand. 

'Dunmngton,  C.  N.,  64,  302;  J.  A  C.  S.,  12,  210,  1891. 


FIG.  69. — Colorimeter. 


TITANIUM  441 

standard  titanium  solution  to  exactly  matcn  the  sample  and  the  solution  made 
up  to  100  cc.  with  5%  sulphuric  acid.  The  titanium  solution  is  added  from  a 
burette,  noting  the  exact  volume  required.  From  this  the  percentage  of  titanium 
in  the  sample  can  readily  be  calculated.  If  iron  is  present  in  the  sample,  an  equiv- 
alent amount  should  be  added  to  the  standard.  If  a  colorimeter  is  used,  a 
standard  should  be  prepared  which  is  deeper  in  color  than  the  sample  examined. 
The  standard  is  poured  into  the  comparison  cylinder  and  the  two  tubes  compared. 
By  raising  or  lowering  the  plunger  (see  illustration)  the  standard  solution  is 
forced  in  or  drawn  out  of  the  comparison  tube.  When  the  colors  match,  the 
cc.  in  the  comparison  tube  will  indicate  the  amount  of  Ti02  present  in  the  sample. 
The  solution  may  be  mixed  by  stirring  with  a  platinum  spiral. 

Example.    One-gram  sample  required  20  cc.  of  titanium  standard  solution, 
1  cc.  of  which  contained  0.001  gram  Ti02.    Then  the  sample  contains 


If  the  colorimeter  has  been  used  and  150  cc.  of  standard  made  by  adding 
30  cc.  of  standard  titanium  solution  and  it  is  found  that  the  column  of  liquor 
in  the  standard  comparison  tube  stands  at  85  cc.,  the  calculation  would  be  as 
follows:  150  cc.  contains  30X0.001  gram  Ti02,  therefore  85  cc.  are  equivalent 


to  ==  0.017  gram  Ti02  per  gram  or  1.7%. 

lou 

For  the  practical  application  of  the  colorimetric  method  in  determining 
titanium  in  steel  the  following  procedure  is  given. 

NOTE.  Separation  of  Titanium  from  Iron.  J.  H.  Walton,  Jr.1  separates  titanium 
from  iron  by  fusing  the  finely  powdered  substance  with  three  or  four  times  as  much 
sodium  peroxide,  and  extracts  the  fusion  with  water.  The  filtrate  contains  the  sodium 
pertitanate  whereas  the  iron  oxide  remains  on  the  filter  paper.  The  filtrate  is  acidified 
with  £[2804  until  5%  of  free  acid  is  obtained  and  the  color  of  this  solution  compared 
with  a  standard  obtained  by  fusing  a  known  weight  of  Ti02  with  NaaOg  and  extracting 
and  treating  with  H2S04  as  in  case  of  the  sample. 

Colorimetric  Determination  of  Titanium  in  Steel  Treated  with 
Ferro=carbon  Titanium2 

The  titanium  in  steel  treated  with  ferro-carbon  titanium  exists  in  two  con- 
ditions : 

(1)  Titanium  insoluble  in  hydrochloric  acid. 

(2)  Titanium  soluble  in  hydrochloric  acid. 

Of  the  very  small  amount  of  titanium  in  treated  steel  the  greater  part  will 
usually  be  found  in  the  first  form,  and  ordinarily  the  determination  of  titanium 
in  this  form  answers  every  purpose  of  identifying  and  judging  the  quality  of 
titanium-treated  steel. 

When  the  amount  of  titanium  in  the  steel  is  exceedingly  small,  the  soluble 
titanium  frequently  exceeds  the  insoluble  and  it  then  is  sometimes  desirable  to 
determine  also  that  existing  in  the  second  form. 

1  J.  Am.  Chem.  Soc.,  29,  481,  1907. 

2  By  L.  E.  Barton.     Method  of  analysis  recommended  by  the  Titanium  Alloy 
Manufacturing  Company. 


442 


TITANIUM 


Reagents.  Peroxide  Solution.  Dissolve  4  grams  of  sodium  peroxide  in 
125  cc.  dilute  sulphuric  acid  (1  of  acid  to  3  of  water),  and  dilute  to  500  cc. 

Concentrated  Standard  Titanium  Solution.  Stock  Solution.  One-fourth 
gram  of  a  standard  20%  carbonless  ferro-titanium  l  is  dissolved  in  30  cc. 
dilute  sulphuric  acid  (1  acid  to  3  water).  When  solution  is  complete  it  is 
oxidized  by  the  least  possible  quantity  of  concentrated  nitric  acid,  boiled  for  a 
few  minutes,  cooled  and  diluted  to  such  a  volume  that  1  cc.  will  contain  0.0005 
gram  of  titanium. 

When  using  a  5-gram  sample  1  cc.  is  therefore  equal  to  0.01%  titanium. 
Dilute   Standard    Titanium  Solution.    This  solution  is  made,  just  before 
making  the  determination,  by  diluting  one  volume  of  the  concentrated  standard 
titanium  solution  to  ten  volumes. 

One  cc.  of  this  solution  contains  0.00005  gram  of  titanium  and  is  equal  to 
0.001%  of  titanium  when  using  a  5-gram  sample. 

Apparatus.  Pipettes  and  Burettes.  The  pipettes  for 
measuring  the  concentrated  standard  solution  and  burette 
for  delivering  the  dilute  standard  solution  should  be  care- 
fully calibrated. 

Nessler  Jars.  These  should  be  graduated  with  50-cc. 
mark.  It  is  convenient  to  have  a  set  of  four. 

Colorimeter.  The  colorimeter  or  comparator  consists 
of  a  rectangular  block  2|  by  4  by  7  ins.  high — the  height 
being  about  J  in.  less  than  the  height  of  Nessler  jars- 
through  which  two  chambers  If  ins.  diameter  and  If  ins. 
between  centers  are  bored  lengthwise — the  chambers  being 
of  such  diameter  as  to  just  receive  the  jars. 

To  one  end  of  the  block  is  fastened  the  base,  which  is 
5  in.  thick  and  through  which  two  f-in.  holes  are  bored 
concentric  with  the  chambers,  thus  forming  a  shoulder 
which  supports  the  jars  and  also  exclude  light  from  the 
sides  of  the  tubes.  To  prevent  shadows  and  give  better 
lighting  the  holes  in  the  base  are  beveled  outward  at  an 
angle  of  45°.  The  construction  will  be  apparent  by  reference  to  Fig.  70.  The 
interior  of  the  chamber  is  painted  dead  black. 

(a)  For  Determination  of  Titanium   Insoluble  in 
Hydrochloric  Acid 

Procedure.  Dissolve  5  grams  of  steel  in  100  cc.  of  dilute  hydrochloric  acid 
(one  of  concentrated  acid  to  two  of  water)  by  boiling  gently.  Wash  off  the 
cover  and  wash  down  the  sides  of  the  beaker  with  water  and  filter  out  the  slight 
insoluble  residue,  washing  with  hot  water  and  dilute  hydrochloric  acid  until  free 
from  iron.  For  filtration  it  is  advisable  to  use  either  a  close-grained  paper  or 
double  rapid-filtering  papers  such  as  S.  &  S.  No.  589  white  ribbon. 

Ignite  the  residue  gently  in  a  platinum  crucible  to  burn  off  carbonaceous 
matter.  Treat  the  residue  in  the  crucible  with  a  mixture  of  3  cc.  dilute  sul- 
phuric acid  (1  :  1),  2  or  3  cc.  hydrofluoric  acid,  and  a  few  drops  of  nitric  acid. 

1  Ferro-titanium  suitable  for  the  preparation  of  standard  titanium  solutions  is 
made  and  supplied  by  the  Titanium  Alloy  Manufacturing  Company,  Niagara  Falls, 


FIG.  70. 


TITANIUM  443 

Heat  and  evaporate  to  fumes  of  sulphuric  anhydride  to  complete  expulsion  of 
hydrofluoric  acid. 

Cool,  add  a  few  cc.  of  water  and  heat  until  the  solution  is  perfectly  clear. 
The  ignited  residue  may  also  be  rapidly  and  completely  brought  into  solution 
by  fusion  with  about  3  grams  of  potassium  bisulphate  and  dissolving  the  fusion 
in  water  and  sulphuric  acid. 

In  either  case  wash  the  contents  of  the  crucible  into  one  of  a  pair  of  Nessler 
jars  and  dilute  with  cold  water  nearly  to  the  50-cc.  mark,  and  in  the  other  jar 
place  an  equal  volume  of  distilled  water. 

Place  the  jars  in  the  colorimeter  and  observe  if  the  sample  solution  is  color- 
less. If  the  sample  solution  is  colored  slightly  yellow  by  iron,  the  water  in  the 
standard  tube  should  be  brought  to  the  same  color  by  addition  of  a  few  drops 
of  a  ferric  solution.  For  this  purpose  a  solution  of  ferric  ammonium  sulphate, 
30  grams  per  liter,  is  very  convenient. 

If  the  work  up  to  this  point  has  been  carefully  performed,  the  addition  of 
ferric  solution  will  usually  be  unnecessary;  and  if  more  than  a  few  drops  of  ferric 
solution  are  required  the  analysis  should  be  rejected  and  a  new  sample  started. 
After  adjusting  the  color — if  necessary — bring  the  volume  of  solution  in  both 
jars  to  the  50-cc.  mark. 

The  volumes  now  being  equal  and  the  solutions  practically  colorless,  add 
2  cc.  of  the  peroxide  solution  to  each.  If  the  sample  contains  titanium  even  in 
minute  quantity  it  will  be  indicated  by  the  immediate  development  of  a  yellow 
color. 

Match  the  colors  by  running  into  the  standard  jar  freshly  prepared  dilute 
standard  titanium  solution,  keeping  the  volumes  equal  by  adding  an  equal 
quantity  of  water  to  the  sample,  placing  the  jars  in  the  colorimeter  for  compari- 
son of  colors. 

As  before  stated,  each  cc.  of  the  dilute  standard  solution  is  equal  to  0.001% 
titanium  when  using  a  5-gram  sample. 

The  determination  may  be  made  in  less  than  an  hour  and  requires  little 
attention. 

(b)  For  Determination  of  Titanium  Soluble  in 
Hydrochloric  Acid 

For  the  determination  of  soluble  titanium  the  filtrate  from  the  insoluble 
titanium  residue  obtained  as  before  described  may  conveniently  be  used. 

Dilute  the  solution  in  which  the  iron  is  already  in  the  ferrous  state  to  180  cc. 
Add  10  cc.  of  alum  solution  made  by  dissolving  40  grams  of  crystallized  alum 
in  a  liter  of  water. 

The  aluminum  here  added  is  subsequently  precipitated  as  alumina  with 
the  titanium  and  serves  to  collect  quickly  the  exceedingly  small  precipitate  of 
titanium  hydroxide  and  facilitate  its  separation  from  the  solution  by  filtration. 

Heat  the  solution  to  about  90°  C.  and  add  ammonia  or  ammonium  carbonate 
solution,  stirring  constantly  until  a  slight  permanent  precipitate  is  produced. 
Add  dilute  hydrochloric  acid  (1  to  1)  drop  by  drop  from  the  wash  bottle  until 
the  precipitate  is  just  redissolved  and  the  solution  perfectly  clear;  then  add 
1  cc.  more  of  the  dilute  hydrochloric  acid. 

Add  3  cc.  of  phenylhydrazine  dissolved  in  10  cc.  hot  water,  which  will  pre- 
cipitate the  titanium  and  aluminum.  Stir  thoroughly  and  filter  immediately 


444  TITANIUM 

on  a  7-cm.  filter  paper  in  a  Biichner  funnel,  using  suction.  Wash  thoroughly 
with  hot  water. 

Calcine  the  precipitate  gently  in  a  platinum  crucible  to  destroy  organic 
matter  and  dissolve  the  residue  exactly  as  described  under  (a),  except  that  6  cc. 
of  dilute  sulphuric  acid  is  used  instead  of  3  cc. 

The  solution,  which  has  a  very  light  yellow,  or  greenish-yellow  color,  is  trans- 
ferred to  one  of  a  pair  of  Nessler  jars  and  diluted  to  the  50-cc.  mark.  About  40 
cc.  of  water  are  placed  in  the  other  jar  and  the  color  of  the  sample  solution  exactly 
matched  by  addition  of  ferric  ammonium  sulphate  and  copper  sulphate  solutions, 
which  are  conveniently  delivered  from  burettes. 

For  matching  the  original  color  of  the  solution  nearly  saturated  solutions 
of  ferric  ammonium  sulphate  and  copper  sulphate  are  suitable. 

Only  a  few  drops  of  such  solutions  are  required,  but  it  is  frequently  neces- 
sary to  use  both  blue  and  yellow  to  match  the  greenish-yellow  tone  of  the  sample 
solution. 

The  standard  is  finally  diluted  to  the  50-cc.  mark.  The  volumes  now  being 
equal  and  identical  in  color,  add  to  each  2  cc.  peroxide  solution  to  develop  the 
titanium  color  and  finish  the  determination  as  before  described  under  (a). 

(c)  For  Determination  of  Total  Titanium 

The  total  titanium  is  given  by  the  sum  of  the  insoluble  and  soluble  titanium 
determined  as  under  (a)  and  (6);  but  if  desired  may  be  determined  in  one 
operation. 

To  determine  total  titanium,  dissolve  as  before  in  hydrochloric  acid  and 
without  filtering  proceed  as  directed  under  (6)  for  determination  of  soluble 
titanium. 

Determination    of    Titanium    when    Interfering    Elements 

are  Present 

If  chromium,  vanadium  or  molybdenum  is  present  in  the  steel,  fuse  the 
residue  insoluble  in  hydrochloric  acid  or  the  calcined  phenylhydrazine  pre- 
cipitate containing  the  interfering  element  with  a  mixture  of  sodium  carbonate 
and  a  little  sodium  nitrate. 

Dissolve  the  fusion  in  water  and  filter.  The  residue  on  the  filter  will  contain 
the  titanium,  free  from  interfering  element.  Bring  the  residue  into  sulphuric 
acid  solution  by  methods  before  described  and  determine  the  titanium  as  usual. 

Colorimetric  Determination  of  Titanium  with  Thymol l 

Principal  and  Preliminary  Considerations.  Titanium  dioxide  dissolved 
in  sulphuric  acid  is  colored  red  by  addition  of  thymol,  the  depth  of  color  being 
directly  proportional  to  the  amount  of  titanium  present.  The  intensity  of  the 
color  is  claimed  by  Lenher  and  Crawford  to  be  twenty-five  times  that  produced 
by  hydrogen  peroxide  with  the  same  amount  of  titanium. 

As  in  case  of  hydrogen  peroxide,  fluorides  destroy  the  color,  hence  must  be 
absent.  Dilution  with  water  has  no  effect  until  the  concentration  of  sulphuric 
acid  falls  below  79.4  (e.g.,  sp.gr.  1.725).  The  color  then  fades  in  direct  propor- 

1  Victor  Lenher  and  W.  G.  Crawford,  C.  N.,  107,  152,  March  28th,  1913. 


TITANIUM  445 

tion  to  dilution.  Warm  solutions  are  lighter  in  color  than  cold  solutions  with  the 
same  amount  of  titanium,  hence  the  standard  and  the  sample  compared  must 
have  the  same  temperature.  The  color  fades  on  heating  but  returns  on  cooling. 
The  temperature  should  be  kept  below  100°  C.  Chlorides,  phosphates  and  tin 
seem  to  have  no  effect.  Tungsten,  Wo03,  interferes,  as  it  intensifies  the  color 
of  the  solution  in  direct  proportion  to  the  amount  present;  hence  it  must  be 
removed  or  allowance  made  by  adding  an  equivalent  amount  to  the  standard 
or  subtracting  the  equivalent  blank. 

Special  Reagents.  Thymol  Solution  1%.  The  thymol  is  dissolved  in  a 
little  glacial  acetic  acid  containing  10%  ethyl  alcohol,  and  this  solution  added 
to  concentrated  sulphuric  acid.  Addition  of  the  thymol  directly  to  the  acid 
would  produce  a  colored  solution.  The  reagent  should  be  kept  protected  from 
strong  light,  otherwise  it  will  become  colored. 

Apparatus.  See  Colorimetric  Determination  of  Titanium  with  Hydrogen 
Peroxide,  Figs.  69,  70,  also  Fig.  43. 

Procedure.  About  0.3  gram  of  the  material  is  fused  with  potassium  acid 
sulphate,  KHSCX,  and  the  melt  dissolved  in  concentrated  sulphuric  acid.  Enough 
thymol  reagent  is  added  so  that  there  is  present  at  least  0.006  gram  thymol  for 
every  0.0001  gram  Ti02.  Concentrated  sulphuric  acid  is  added  to  bring  up  the 
volume  to  50  or  100  cc.  in  a  Nessler  tube  exactly  as  in  the  case  of  the  colorimetric 
determination  of  titanium  with  H202.  The  depth  of  color  is  compared  with  a 
standard  solution  of  titanium  dissolved  in  a  concentrated  sulphuric  acid  added 
to  5  cc.  of  thymol  solution  made  up  to  a  convenient  volume  with  concentrated 
sulphuric  acid.  The  procedure  is  the  same  as  described  in  the  H202  method. 


THE  ANALYSIS  OF  TITANIFEROUS  ORES  1 

Determination  of  Titanium 

Decompose  the  ore  by  fusion  with  potassium  bisulphate,  dissolving  the 
fusion  in  water,  hydrochloric  and  sulphuric  acids.  If  an  insoluble  residue  remains, 
filter  it  out.  Calcine  the  residue,  add  a  few  drops  of  sulphuric  acid  and  suf- 
ficient hydrofluoric  acid  to  dissolve  silica,  evaporate  to  fumes  of  sulphuric  anhy- 
dride and  then  heat  to  redness. 

If  a  residue  now  remains,  bring  it  into  solution  directly  in  acids  or  fuse  with  a 
little  potassium  bisulphate,  etc.,  finally  adding  the  solution  to  the  main  solution 
obtained  as  before  described. 

If  desired,  the  sample  of  ore  can  first  be  partially  dissolved  in  hydrochloric 
and  sulphuric  acids,  and  the  insoluble  residue  then  fused  with  potassium  bisul- 
phate or  treated  with  sulphuric  and  hydrofluoric  acids. 

Some  ores  may  be  completely  decomposed  by  a  mixture  of  nitric,  hydro- 
fluoric and  sulphuric  acids,  evaporating  to  fumes  of  sulphuric  anhydride  in  a  plati- 
num dish  to  free  the  solution  from  nitric  and  hydrofluoric  acids. 

The  complete  decomposition  of  the  sample  having  been  accomplished,  the 
titanium  in  the  solution  is  determined  by  either  the  gravimetric  or  volumetric 
methods  for  Determination  of  Titanium  in  Ferro-Carbon  Titanium.  Pages 
436  and  441. 

t    x  Method  of  Analysis  used  in  the  laboratories  of  The  Titanium  Alloy  Manufacturing 
Company. 


446  TITANIUM 


Determination  of  Iron  in  Presence  of  Titanium 

The  sample  is  decomposed  as  directed  under  the  Determination  of  Titanium* 
The  sulphuric  acid  solution,  which  should  have  a  volume  of  150  to  200  cc., 
is  saturated  with  hydrogen  sulphide  gas  to  reduce  the  iron,  and  filtered  to 
separate  any  precipitated  sulphides  and  free  sulphur.  The  filtrate  is  collected 
in  a  flask  fitted  with  a  rubber  stopper  through  which  pass  two  glass  tubes,  one 
reaching  nearly  to  the  bottom  for  conducting  gas  into  the  solution,  the  other 
a  short  exit  tube.  Unless  the  solution  after  filtration  is  still  highly  charged  with 
hydrogen  sulphide,  more  gas  should  be  passed  into  the  solution  to  reduce  any 
iron  that  may  have  been  oxidized  by  the  atmosphere  during  filtration.  The 
excess  hydrogen  sulphide  is  now  expelled  by  boiling  the  solution  while  passing  a 
current  of  carbon  dioxide. 

When  the  exit  gases  cease  to  darken  a  piece  of  filter  paper  moistened  with 
lead  acetate  solution,  the  flask  is  cooled  while  still  passing  the  carbon  dioxide. 
When  the  flask  has  partially  cooled  the  carbon  dioxide  is  shut  off  and  the  flask 
quickly  cooled  in  running  water  and  immediately  titrated  with  standard  per- 
manganate solution. 

Determination  of  Silica 

This  determination  is  conveniently  combined  with  the  determination  of  iron, 
the  ore  being  preferably  decomposed  by  fusion  with  potassium  bisulphate. 
The  fusion  is  dissolved  and  evaporated  with  excess  sulphuric  acid  to  fumes  of  sul- 
phuric anhydride  and  the  silica  determination  finished  as  usual — weighing,  vola- 
tilizing with  hydrofluoric  acid,  etc.  If  the  ore  contains  quartz  or  a  silicate  unde- 
composable  by  treatment  with  potassium  bisulphate  and  hydrofluoric  acid,  the 
residue  filtered  from  the  sulphuric  acid  solution  should  be  fused  with  sodium 
carbonate  and  the  silica  then  determined  as  usual. 

Determination  of  Alumina 

After  making  determination  or  separation  of  titanium  by  gravimetric  method, 
use  the  filtrate  for  determination  of  alumina. 

Phenylhydrazine  Method  for  Determination  of  Aluminum  in  Presence 

of  Iron 

The  iron  and  aluminum  should  be  in  hydrochloric  or  sulphuric  acid  solution. 
Nearly  neutralize  the  solution  with  ammonium  carbonate.  Pass  sulphurous 
acid  gas  to  complete  reduction  of  the  iron.  Boil  until  the  excess  sulphurous  acid 
is  driven  off  and  if  titanic  acid  separates  filter  it  out. 

After  filtering  out  titanic  acid  again  nearly  neutralize  with  ammonium 
bonate,  pass  a  little  sulphurous  acid  gas  and  heat  for  a  few  minutes  to  reduc 
any  iron  that  might  have  been  oxidized  during  filtration.  If  titanium  has  m 
been  detected  the  second  treatment  with  sulphurous  acid  may  be  omitted, 
either  case  the  solution  still  containing  a  little  free  sulphurous  acid  is  neai 
neutralized  with  ammonium  carbonate,  diluted  to  300  cc.  and  3  cc.  of  phenol 
hydrazine  added.  Stir  thoroughly,  let  settle  and  filter  out  the  alumina.  If  tl 
precipitate  is  discolored  by  iron,  dissolve  in  hydrochloric  acid,  and  repeat 
reduction,  neutralization  and  precipitation  by  phenylhydrazine.  Ignite  and 


TITANIUM  447 

weigh  ALOs+PaOe.  Since  the  alumina  precipitate  may  be  contaminated  by 
phosphoric  anhydride  (P205),  determine  it  by  analysis  and  correct  the  alumina 
determination  accordingly. 

Determination  of  Phosphorus 

Phosphoric  acid  may  be  separated  from  titanic  acid  by  repeatedly  fusing 
the  ore  with  alkali  carbonate  and  extraction  of  alkali  phosphate  with  water. 

The  determinations  of  other  constituents  of  the  ore  are  conducted  by  the 
usual  methods  of  ore  analysis. 


TUNGSTEN,  TANTALUM  AND  GOLUMBIUM1 


TUNGSTEN 

WILFRED  W.  SCOTT 

W.,  at.wt.  184.0;    sp.gr.  18.77;  m.p.  3000°  C.;2   oxides,  WO2  (brown);  WO3 
(yellow) ;     acids,  H2WO4,  ortho  tungstic;  H2W4Oi3,  met  a  tungstic 

DETECTION 

Minerals.  The  finely  powdered  material  is  fused  with  about  six  times  its 
weight  of  potassium  hydroxide  in  a  silver  or  nickel  crucible.  (Fusion  with  Na2C03 
or  with  KHS04  in  platinum  will  also  decompose  the  material.  See  Solution  of 
the  Sample.)  The  cooled  mass  is  extracted  with  hot  water  and  filtered.  The 
solution  is  treated  with  about  25  cc.  of  dilute  hydrochloric  acid  and  boiled.  The 
precipitate  formed  may  contain  antimony,  molybdenum,  niobium,  silica,  tantalum, 
tin  and  tungsten.  This  is  filtered  and  the  moist  residue  treated  with  a  solution 
of  yellow  ammonium  sulphide.  Antimony,  molybdenum,  tin  and  tungsten  pass 
into  the  filtrate,  niobium  and  tantalum  remain  on  the  filter.  The  ammoniacal 
sulphide  extract  is  acidified  with  hydrochloric  acid  and  boiled.  The  precipitate 
is  filtered  and  washed  with  a  little  hydrochloric  and  nitric  acids.  Antimony, 
molybdenum  and  tin  pass  into  the  filtrate,  while  tungsten  and  sulphur  remain  on 
the  filter.  Tungsten  is  now  confirmed  as  follows,  portions  of  the  precipitate 
being  taken: 

1.  The  residue  is  suspended  in  dilute  hydrochloric  acid  and  a  piece  of  zinc, 
aluminum,  or  tin  placed  in  the  solution.    In  the  presence  of  tungsten  a  blue- 
colored  solution  or  precipitate  is  seen,  the  color  disappearing  upon  dilution  with 
water. 

2.  A  portion  of  the  precipitate  is  warmed  with  ammonium  hydroxide  and  the 
extracts  absorbed  with  strips  of  filter  paper. 

(a)  A  strip  of  this  treated  paper  is  moistened  with  dilute  hydrochloric  acid 
and  warmed.  In  the  presence  of  tungstic  acid  a  yellow  coloration  is  produced. 

(6)  A  second  strip  of  paper  is  moistened  with  a  solution  of  stannous  chloride. 
A  blue  color  is  produced  in  the  presence  of  tungsten. 

(c)  A  third  strip  dipped  into  cold  ammonium  sulphide  remains  unchanged 
until  warmed,  when  the  paper  turns  green  or  blue  if  tungsten  is  present. 

Iron,  Steel  and  Alloys.  These  decomposed  with  strong  hydrochloric  acid 
followed  by  nitric  acid  as  directed  under  Solution  of  the  Sample  leave  a  yellow 
residue  in  the  presence  of  tungsten.  If  this  residue  is  digested  with  warm  ammo- 
nium hydroxide  and  the  extract  evaporated  to  dryness  a  yellow  compound,  W03, 
will  remain  if  tungsten  is  present.  This  oxide  may  be  reduced  in  the  reducing 
flame  to  the  blue-colored  oxide. 

1  Columbium  is  also  known  as  Niobium. 
•Circular  35  (2d  Ed.),  U.  S.  Bureau  of  Standards. 
448 


TUNGSTEN,  TANTALUM  AND  COLUMBIUM         449 


ESTIMATION 

Tungsten  occurs  principally  as  wolfram,  a  tungstate  of  iron  and  manganese 
(FeW04-Mn04),  and  as  scheelite,  a  tungstate  of  calcium  (CaW04).  The  best 
concentrate  of  hand-picked  material  contains  70  to  74%  tungsten  in  terms  of  its 
oxide,  W03. 

The  element  is  met  with  in  alloys — ferro-tungsten,1  silico-tungsten,  tungsten 
steels  containing  as  much  as  10  to  20%  of  the  metal,  used  for  making  high-speed, 
self-hardening  cutting  tools;  tungsten  powder; l  alkali  tungstates  for  mordanting 
purposes;  tungstic  oxide,  W03;  tungsten  electric  light  filaments,  etc. 

Solution  of  the  Sample 

For  solution  of  the  sample  the  following  facts  should  be  kept  in  mind 
regarding  solubilities. 

The  metal  is  practically  insoluble  in  HC1  and  in  H2S04.  It  is  slowly  attacked 
by  HN03,  aqua  regia  and  by  alkalies.  It  is  readily  soluble  in  a  mixture  of  HN03 
andHF(=WF6orWOF4). 

Oxides.  W02  is  soluble  in  hot  HC1  and  in  hot  H2S04  ( =red  sol.),  also  in 
KOH  (red  sol.).  The  oxide  W03  is  scarcely  soluble  in  acids,  but  is  readily  soluble 
in  KOH,  K2C03,  NH4OH,  (NH4)2C03,  (NH^S*.  Both  the  acid  and  the  alkali 
solutions  deposit  the  blue  oxide  on  standing. 

Acids.  Ortho  tungstates.  A  few  are  soluble  in  water  and  in  acids.  The 
alkali  salts  only  slightly  soluble.  The  meta  tungstates  are  easily  soluble  in  water. 
Tungstates  are  precipitated  from  alkali  salts  by  dilute  H2S04,  HC1,  HN03,  HsPO* 
(aqua)  as  yellow  W03-H20  or  white  W03-2H20.  Meta  tungstates  are  not  pre- 
cipitated by  cold  acids,  but  are  precipitated  by  boiling  and  by  long  standing. 

Solution  of  Minerals.  Fusion  Method.  The  material  may  be  opened  out 
by  fusion  with  alkalies  or  alkaline  carbonates,  or  by  solution  in  mixtures  of  acids 
of  which  hydrofluoric  acid  is  a  constituent.  The  following  procedure  is  satis- 
factory: 

The  finely  divided  mineral  is  fused  with  five  or  ten  times  its  weight  of  sodium 
or  potassium  carbonate  and  the  fusion  extracted  with  hot  water.  The  aqueous 
solution  may  contain  one  or  more  of  the  following:  alkaline  tungstate,  niobate, 
molybdate,  tantalate,  arsenate,  antimonate,  stannate,  aluminate,  chromate,  vana- 
date,  silicate,  phosphate,  sulphate,  chloride,  fluoride,  etc.,  in  absence  of  com- 
binations forming  insoluble  precipitates.  The  residue  may  contain  alkaline 
zirconate,  ferric  oxide,  carbonates  of  calcium,  strontium,  barium,  etc.  Tungsten 

1  TYPICAL  ANALYSES 
TUNGSTEN  POWDER  FERRO  TUNGSTEN 

%  % 

W,  97  to  98.7  71  to  85. 5 

Fe,  .5  to  .6+  14  to  24. 5 

C,  .1  to  .3+  .4  to  2.6 

Si,  .3  to  .7+  -I  to   .4 

Mn,  Oto  .2  .08  to   .9+ 

P,  —   —  .008  to   .02 

S,   —   —  .01  to   .02 

Al,  .2  to  .5  .001  to   .07 

Cu,  —   —  Oto   .008 
Mg,0  to  .3+ 


450        TUNGSTEN,  TANTALUM  AND  COLUMBIUM 

is  determined  in  the  filtered  solution  by  acid  or  mercurous  nitrate  precipitation, 
as  is  described  under  the  procedures  for  the  gravimetric  determination  of  the 
element.  (Separation  of  tungsten  from  certain  substances  may  be  necessary.) 

Steel  and  Alloys.  Low  tungsten  steel  may  be  decomposed  with  hydrochloric 
or  dilute  sulphuric  acid,  the  greater  part  of  the  iron  being  removed  in  solution  and 
tungsten  remaining  behind  as  a  metal  with  a  small  amount  of  iron.  The  residue 
is  then  fused  with  sodium  carbonate,  the  tungstate  extracted  with  water,  and 
tungsten  determined  gravimetrically.  Brearley  and  Ibbotson  recommended  the 
following  procedure  i1 

Five  grams  of  the  sample  are  digested  with  50  to  100  cc.  of  concentrated 
hydrochloric  acid  just  short  of  the  boiling-point.  The  iron  is  easily  attacked, 
but  tungsten  is  not.  On  adding  a  few  drops  of  concentrated  nitric  acid  the  ferrous 
chloride  changes  to  the  ferric  form  and  tungsten  is  visibly  acted  upon  until  the 
clear  orange-colored  ferric  chloride  blackens  again,  showing  that  some  ferrous 
chloride  has  reformed.  By  repeating  the  addition  of  nitric  acid  as  required,  for 
converting  all  of  the  iron  to  the  ferric  state  and  adding  a  slight  excess  the  sample 
completely  passes  into  solution  in  a  few  minutes.  The  essential  points  of  the 
process  consist  in  the  present  of  sufficient  hydrochloric  acid  to  keep  the  tungstic 
oxide  in  solution  until  decomposition  is  complete,  and  maintaining  the  strength 
of  the  acid  during  the  decomposition.  The  smaller  the  excess  of  acid  over  neces- 
sary requirements,  the  greater  the  economy  of  material,  and  of  time  occupied  in 
the  subsequent  evaporation.  No  more  oxidant  is  used  than  is  necessary  to  com- 
pletely oxidize  the  iron  and  tungsten.  If  the  acid  solution  of  the  metal  is  boiled 
until  the  tungstic  oxide  begins  to  separate  out,  and  then  diluted  with  at  least 
twice  its  volume  of  hot  water  and  again  boiled,  all  the  oxide  is  precipitated  except 
2  or  3  milligrams.  The  oxide,  W03,  is  generally  contaminated  with  silica,  which 
may  be  removed  by  volatilization  with  hydrofluoric  acid;  and  it  contains  traces 
of  ferric  iron,  which  may  be  estimated  by  fusion  of  the  residue  with  sodium  car- 
bonate and  extracting  the  tungsten  with  hot  water;  the  iron  remaining  may  be 
ignited  and  weighed  and  the  weight  subtracted  from  that  of  the  previously  weighed 
oxides  W03  and  Fe203. 

In  tungsten  molybdenum  steels  90  cc.  of  strong  hydrochloric  acid  and  10  cc. 
of  concentrated  nitric  acid  are  recommended.  The  solution  is  evaporated  to 
pastiness,  and  then  taken  up  and  boiled  with  dilute  hydrochloric  acid  (1  :  4), 
tungsten  and  silica  remaining  undissolved  and  molybdenum  and  iron  passing 
into  the  filtrate. 

Steel  containing  a  high  percentage  of  tungsten  is  extremely  hard,  so  that  it 
is  practically  impossible  to  get  filings  or  borings  without  contaminating  the  sample 
with  material  from  the  cutting  tool.  The  substance  is  best  prepared  by  hammer- 
ing into  a  coarse  powder  in  a  steel  mortar.  These  coarse  particles  are  not  readily 
decomposed  by  the  usual  acid  treatment  or  by  the  alkali  carbonate  and  nitrate 
fusion.  Opening  up  of  the  material  may  be  easily  accomplished  by  fusion  with 
potassium  acid  sulphate. 

About  0.5  gram  of  the  coarse  powder  is  heated  with  ten  times  its  weight  of 
KHS04  over  a  low  flame,  with  covered  crucible,  the  flame  being  removed  if  the 
action  becomes  violent.  The  melt  is  cooled  slightly  and  an  additional  5  grams 
of  bisulphate  added  and  the  treatment  repeated.  Finally  a  third  5-gram  portion 
of  the  acid  sulphate  is  added  and  the  material  heated  to  a  cherry  redness  for  a 

*  "  The  Analysis  of  Steel-Works  Materials." 


TUNGSTEN,  TANTALUM  AND  COLUMBIUM         451 

few  minutes.  About  fifteen  or  twenty  minutes  are  sufficient  to  decompose  the 
material.  The  heating  should  be  conducted  cautiously  so  that  only  a  gentle 
evolution  of  gas  occurs,  and  the  mass  kept  in  a  molten  state  until  the  black  par- 
ticles of  steel  have  entirely  dissolved.  The  mass  is  now  cooled,  the  crucible  and 
cover  placed  in  50  to  75  cc.  of  water  and  boiled  to  disintegrate  the  fused  mass. 
The  liquid  is  treated  with  20  cc.  of  concentrated  hydrochloric  acid  until  the  pre- 
cipitated tungstic  acid  is  yellow.  After  settling,  the  precipitate  is  filtered  off 
and  washed  with  10%  ammonium  nitrate  solution.  The  residue  is  then  dissolved 
in  hot  dilute  ammonium  hydroxide,  the  ammonium  tungstate  then  evaporated 
in  a  weighed  platinum  crucible  to  dryness,  then  covered  with  a  watch-glass  and 
the  residue  heated  to  decompose  completely  the  ammonium  salt.  Tungstic  oxide, 
W03,  remains  and  is  so  weighed. 

Should  silica  be  present  in  the  sample  it  will  contaminate  the  oxide,  W03.  It 
is  removed  by  volatilization  with  hydrofluoric  acid.  A  small  amount  of  tungsten 
passes  into  the  filtrate  from  the  acid  treatment,  which  is  recovered  by  repeated 
evaporation  with  hydrochloric  acid  as  described  under  the  gravimetric  procedure 
on  page  453. 

Ferro  Tungsten  Alloys  may  be  dissolved  by  covering  1  to  2  grams  of  the 
alloy  placed  in  a  platinum  dish  with  hydrofluoric  acid  and  adding  nitric  acid  in 
small  portions,  the  dish  being  kept  covered  during  the  intervals  between  the 
additions.  When  the  energetic  action  subsides  10  to  15  cc.  of  strong  sulphuric 
acid  are  added  and  the  material  digested  until  the  decomposition  is  complete. 
The  mixture  is  now  evaporated  to  S03  fumes  over  a  low  flame.  (Air  blown  over 
the  solution  assists  evaporation.)  The  residue  is  collected  on  a  filter  and  washed 
well,  then  ignited  and  weighed  as  W03. 

Tungsten  Bronzes.  About  0.5  gram  of  finely  powdered  bronze  is  heated  in 
a  porcelain  crucible  with  2  grams  of  alkali-free  ammonium  sulphate  and  2  cc. 
of  concentrated  sulphuric  acid,  using  a  very  small  flame  and  occasionally  agitating 
the  mixture.  After  a  few  minutes  when  sulphuric  acid  fumes  are  freely  evolved  the 
crucible  is  allowed  to  cool  and  then  additional  ammonium  sulphate  and  sulphuric 
acid  are  added  and  the  heating  repeated  until  strong  acid  fumes  are  evident.  The 
mass  is  cooled,  moistened  with  water,  rinsed  into  a  porcelain  dish,  50  cc.  of  con- 
centrated nitric  acid  added  and  the  contents  digested  for  about  four  hours,  then 
diluted  with  water  and  the  tungstic  oxide,  W03,  filtered  off.  The  small  amount 
of  tungsten  passing  into  the  filtrate  is  recovered  by  evaporating  to  dryness  and 
extracting  the  residue  with  hot  dilute  ammonium  hydroxide.  W03  is  precipitated 
with  HC1  and  the  alkalies  determined  in  the  filtrate. 

SEPARATIONS 

One  or  more  of  the  following  separations  may  be  required  in  the  isolation  of 
tungsten.  (See  Separation  of  Tungsten  under  Detection.) 

Separation  of  Tungsten  from  Silica.  The  oxide  of  tungsten,  as  ordinarily 
obtained,  is  frequently  contaminated  with  silica.  The  removal  of  silica  is  accom- 
plished by  heating  the  mixture  in  a  platinum  dish  with  sulphuric  and  hydrofluoric 
acids  and  volatilizing  the  silica.  After  taking  to  dryness  and  igniting  gently, 
the  last  traces  of  sulphuric  acid  are  expelled  by  adding  ammonium  carbonate 
and  again  igniting. 

Separation  from  Tin.  The  method  depends  upon  the  fact  that  volatile  stannic 
chloride  is  formed  and  expelled  when  stannic  oxide  is  heated  with  ammonium 


452        TUNGSTEN,  TANTALUM  AND  COLUMBIUM 

chloride,  while  the  oxide  of  tungsten  remains  behind.    The  method  was  proposed 
by  Rammelsberg.1 

Silica  having  been  removed,  the  weighed  residue  is  mixed  with  six  to  eight  times 
its  weight  of  ammonium  chloride  (free  from  non-volatile  residue)  in  a  platinum 
crucible,  placed  in  a  larger  crucible,  both  vessels  being  covered.  Heat  is  applied 
until  no  more  vapors  of  ammonium  chloride  are  evolved.  Additional  ammonium 
chloride  is  added  and  the  treatment  is  repeated  three  times.  The  fourth  treat- 
ment is  followed  by  weighing  of  the  residue  and  the  treatment  repeated  once 
more.  If  no  further  loss  of  weight  takes  place  it  is  assumed  that  all  the  stannic 
oxide  has  been  driven  off.  The  inner  crucible  is  now  placed  directly  over  the 
flame  and  heated  to  dull  redness  for  a  few  minutes  and  the  oxide,  W03,  weighed. 

Separation  of  Tungsten  from  Tin  and  Antimony.  Talbot's  Process.2  The 
mixed  oxides  are  fused  with  twelve  times  their  weight  of  potassium  cyanide  in 
a  porcelain  crucible.  Tin  and  antimony  are  thrown  out  as  metals  and  the  soluble 
alkali  tungstate  formed.  This  is  leached  out  with  water  and  the  aqueous  extract 
boiled  (hood)  with  an  excess  of  nitric  acid  to  drive  off  the  cyanogen  compounds. 
The  tungstate  is  then  precipitated  by  the  usual  methods.  If  phosphorus  is 
present  in  the  sample  it  will  be  found  in  the  solution  with  tungsten  and  its  removal 
will  be  necessary. 

Separation  of  Tungsten  from  Arsenic  and  Phosphorus.  Both  arsenic  and 
phosphorus  may  be  precipitated  by  cold  magnesia  mixture  in  an  ammoniacal 
solution,  tungsten  remaining  in  solution.  The  separation  of  arsenic  is  difficult, 
as  it  is  tenaciously  retained  by  tungsten  as  a  complex  salt.  The  following  process 
is  outlined  by  Kehrmann.3 

One  to  2  grams  of  the  sample  are  fused  with  twice  as  much  sodium  hydroxide 
as  is  required  to  combine  with  the  arsenic  oxide,  the  resulting  cake  is  dissolved  in 
a  little  water  and  boiled  in  an  Erlenmeyer  flask  for  half  an  hour.  After  cooling, 
three  times  as  much  ammonium  chloride  as  is  needed  to  form  chlorides  with  the 
alkalies  present  is  added,  and  then  ammonium  hydroxide  equal  to  one-fourth  the 
volume  of  the  solution  under  investigation,  followed  by  sufficient  magnesia  mixture, 
added  cold,  drop  by  drop  with  constant  stirring.  After  settling  several  hours, 
the  solution  is  filtered  and  the  residue  washed  with  a  weak  solution  of  ammonia 
and  ammonium  nitrate.  It  is  advisable  to  dissolve  the  residue  in  dilute  acid  and 
repeat  the  precipitation  several  times.  The  filtrates  containing  the  tungsten  are 
combined  and  concentrated  by  evaporation  if  necessary.  The  alkaline  solution  is 
neutralized  with  nitric  acid  and  the  tungsten  precipitated  with  mercurous  nitrate 
as  described  under  the  gravimetric  procedures  for  tungsten,  page  454.  Magnesia 
is  apt  to  contaminate  the  tungsten. 

Separation  of  Tungsten  from  Molybdenum,  Hommel's  Process.  The  moist 
oxides  *  of  tungsten  and  molybdenum  are  digested  with  concentrated  sulphuric 
acid  and  a  few  drops  of  dilute  nitric  acid,  in  a  porcelain  dish  over  a  free  flame  for 
about  half  an  hour.  About  three  times  its  volume  of  water  is  added  to  the  coolt 
solution,  the  residue,  W03,  filtered  off  and  washed  with  dilute  sulphuric  acid  (1  :  20) 
followed  by  three  washings  with  alcohol.  The  residue  is  ingited  separately  from 
the  paper  and  weighed  with  the  ash  of  paper  as  W03. 


iPogg.  Ann.,  120,  66,  1864;  C.N.,  9,  25,  1864. 
2  J.  A.  Talbot,  J.  Sci.  (2),  50,  244,  1870. 


» F.  Kehrmann,  Ber.,  20,  1813,  1887. 
4  Ignited  oxides  require  fusion  with  sodium  carbonate,  the  resulting  melt  is  the 
treated  with  sulphuric  acid. 


TUNGSTEN,  TANTALUM  AND  COLUMBIUM         453 

Molybdenum  is  in  the  filtrate  and  may  be  precipitated  in  a  pressure  flask 
with  H2S. 

Volatilization  of  Molybdenum  with  Dry  Hydrochloric  Acid  Gas.  Pechard's 
Process.1  The  procedure  depends  upon  the  fact  that  molybdenum  oxide  heated 
in  a  current  of  dry  hydrochloric  acid  gas  at  250  to  270°  C.  is  sublimed,  whereas 
tungsten  is  not  affected. 

The  oxides  of  the  two  elements,  or  their  sodium  salts,  are  placed  in  a  porcelain 
boat  and  heated  in  a  hard  glass  tube,  one  end  of  which  is  bent  vertically  down- 
ward and  connected  with  a  Feligot  tube  containing  a  little  water.  A  current 
of  dry  hydrochloric  acid  gas  is  conducted  over  the  material,  heated  to  250  to 
270°  C.  From  time  to  time  the  sublimate  of  molybdenum  (Mo03-2HCl)  is  driven 
towards  the  Feligot  tube  by  careful  heating  with  a  free  flame.  This  enables  the 
analyst  to  observe  whether  any  more  sublimate  is  driven  out  of  the  sample  and  to 
ascertain  when  the  tungsten  is  freed  of  molybdenum.  From  one  and  a  half  to 
two  hours  are  generally  sufficient  to  accomplish  the  separation.  If  sodium  salt  is 
present  it  is  leached  out  of  the  residue,  and  this  is  then  ignited  to  W03.  Molyb- 
denum may  be  determined  in  the  sublimate. 

Separation  from  Vanadium.2  Tungstic  and  vanadic  acids  are  precip- 
itated with  HgN03  and  HgO,  the  moist  precipitate  dissolved  in  HC1  and  the 
solution  largely  diluted ;  W03  is  precipitated  free  from  vanadium. 

Separation  from  Titanium.3  The  material  is  heated  with  K2C03  and  KN03, 
tungsten  is  dissolved  out  with  water  and  precipitated  as  mercurous  tungstate. 

Separation  of  Tungsten  from  Iron.  The  procedure  is  given  under  Solu- 
tion of  the  Sample,  of  Steel  and  Alloys.  The  impure  oxide  W03  is  fused  with 
Na2C03  and  the  melt  extracted  with  water.  Fe(OH)3  remains  on  the  filter. 
The  filtrate  is  evaporated  to  dryness  with  HN03  and  the  residue  extracted  with 
water.  The  insoluble  W03  is  washed  with  dilute  NH4N03  solution,  then  dis- 
solved in  NH4OH  and  tungsten  determined  in  the  solution. 


GRAVIMETRIC  PROCEDURES  FOR  DETERMINING  TUNGSTEN 

Since  there  is  no  highly  commendable  volumetric  procedure  for  determin- 
ing tungsten,  the  gravimetric  methods  are  preferred. 

The  element  is  determined  as  tungstic  oxide,  W03.  It  may  be  isolated 
in  the  form  of  tungstic  acid,  ammonium  tungstate,  or  as  mercurous  tungstate, 
in  the  usual  course  of  analysis,  all  of  which  forms  may  be  readily  changed  by 
ignition  to  the  non-volatile  oxide,  W03. 

Precipitation  of  Tungstic  Acid 

Isolation  of  tungstic  acid  by  acid  treatment  of  steels  and  alloys  is  given  under 
Solution  of  the  Sample  in  the  procedures  for  these  substances.  If  a  fusion 
method  with  an  alkali  hydroxide  or  carbonate  has  been  used  for  decomposition 
of  the  sample  and  the  tungsten  extracted  with  water  the  oxide  may  be  precipitated 
as  follows: 

An  equal  volume  of  concentrated  hydrochloric  acid  is  added  to  the  aque- 

1  E.  Pechard,  Comp.  Rend.,  114,  173,  1891. 

2  Friedheim,  C.  N.,  61,  220. 

3  Defacqz,  C.N.,  74,  293. 


454         TUNGSTEN,   TANTALUM   AND   COLUMBIUM 

ous  solution  of  the  alkali  tungstate,  and  the  mixture  evaporated  to  dryness 
on  the  water  bath,  and  then  heated  for  an  hour  or  more  in  the  hot-air  oven  at 
120°  C.  The  residue  is  moistened  with  hydrochloric  acid,  then  taken  up  and 
boiled  with  water,  filtered  and  washed  with  a  5%  hydrochloric  acid  or  ammo- 
nium nitrate  solution.  The  precipitate  is  ignited  and  weighed  as  W03,  which 
contains  0.793  gram  of  tungsten  per  gram  of  oxide. 

NOTE.  A  small  amount  of  tungsten  may  pass  into  the  filtrate.  This  is  recovered 
by  repeated  evaporation  with  hydrochloric  or  nitric  acids. 

Precipitation  of  Tungsten  as  Mercurous  Tungstate.     Berzelius' 

Process 1 

The  water  extract  of  the  sodium  carbonate  fusion  is  concentrated  to  50  to 
100  cc.,  a  few  drops  of  methyl  orange  added  and  the  alkali  carefully  neutralized 
with  nitric  acid,  avoiding  an  excess.2  The  mixture  is  boiled  to  expel  all  the 
carbonic  acid,  then  cooled  and  an  excess  of  mercurous  nitrate  added.  (Usually 
20  cc.  of  a  solution  made  by  digesting  60  grams  of  mercury  with  25  cc.  of  nitric  acid 
(sp.gr.  1.4)  +75  cc.  of  water  two  hours  on  steam  bath,  and  diluting  to  400  cc.) 
When  the  precipitate  settles  the  supernatant  solution  should  be  clear.  After  two 
hours  or  more  the  yellow  precipitate  is  filtered  off,  washed  with  2%  mercurous 
nitrate  solution,  dried  and  ignited  to  W03. 

One  gram  W03  =  0.793  gram  W. 

Volumetric  Method3 

Tungstic  oxide  is  precipitated  according  to  one  of  the  procedures  outlined  in 
the  section  on  Solution  of  the  Sample.  The  impure  oxide  containing  silica  and 
iron  is  washed  on  the  filter  with  dilute  nitric  acid,  then  with  dilute  solution 
of  potassium  nitrate  (5-10%  sol.)  until  the  filtrate  shows  the  residue  is  freed  from 
acid.  The  residue  is  washed  into  a  flask,  200  cc.  of  water  added  and  the  mixture 
titrated  boiling  hot  with  standard  solution  of  sodium  hydroxide,  using  phenol- 
phthalein  as  indicator. 

One  cc.  N.  NaOH  =0.116  gram  W03,  or  =0.092  gram  W. 

»J.  J.  Berzelius,  Schweigger's  Jour.,  16,  476,  1816;  W.  W.  Hutchin,  Analyst,  36, 
398,  1911. 

2  Mellor  recommends  adding  a  few  drops  of  nitric  acid  in  excess,  followed  by  the 
mercurous  nitrate,  and  then  ammonium  hydroxide,  drop  by  drop,  until  a  brown  pre- 
cipitate separates. 

8 Hewing,  Z.  angew.  Chem.,  14,  165,  1901. 


TUNGSTEN,   TANTALUM  AND   COLUMBIUM        455 
TANTALUM   AND    COLUMBIUM 

Cb,ti£.Mrt.  93.5;  sp.gr.  7.06;  m.p.  1950°;  oxides  CbO,  CbO2,  Cb2O5. 
Ta,  at.wt.  181.5;  sp.0r.14.49;  m.p.  3900°;  oxides  TaO2,  Ta2O4,  Ta2O5. 

DETECTION 

The  finely  powdered  mineral  is  digested  with  strong  hydrochloric  acid, 
followed  by  concentrated  nitric  acid  and  the  mixture  taken  to  dryness.  The 
residue  is  treated  with  hydrochloric  acid,  diluted  with  water,  boiled  and  filtered. 
The  residue  is  digested  with  warm  ammonium  hydroxide  to  remove  tungsten 
and  the  solution  filtered  from  the  insoluble  material,  in  which  tantalum  and 
columbium  will  be  found,  if  present  in  the  sample. 

Decomposition  of  the  material  may  be  effected  according  to  the  procedure 
described  for  the  detection  of  tungsten,  page  448. 

The  residue  obtained  is  digested,  in  a  platinum  crucible,  with  hydrofluoric 
acid  and  a  saturated  solution  of  potassium  fluoride  added.  The  mixture  is 
evaporated  to  small  volume  and  allowed  to  cool  slowly.  Tantalum  will  separate 
in  acicular  rhombic  crystals  (solubility — 1  part  of  the  salt  in  200  parts  of  water) 
as  potassium  fluotantalate  2KF-TaF5;  columbium  separates  in  plates  as  the 
double  fluoride,  2KF-CbF6,  if  HF  is  in  excess,  or  as  a  double  oxy-fluoride 
2KF-CbOF6,  if  HF  is  not  in  excess;  the  columbium  salt  being  much  more 
soluble  (1  part  of  the  salt  in  12  parts  of  water)  crystallizes  after  the  crystals  of 
tantalum  have  formed. 

The  crystals  may  be  examined  under  a  lens  and  then  treated  as  follows: 
The  needle-like  crystals  are  heated  in  a  shallow  platinum  dish  or  crucible  cover 
with  strong  sulphuric  acid  to  fumes,  the  cooled  mixture  is  transferred  to  a  test- 
tube  with  water  and  boiled  to  precipitate  the  tantalic  acid.  An  opalescent 
solution  is  obtained  when  this  precipitate  is  treated  with  an  excess  of  hydro- 
chloric acid.  Metallic  zinc  added  to  this  solution  produces  no  color.  A  light- 
brown  precipitate  is  obtained  with  tannic  acid  in  the  presence  of  tantalum. 
If  the  crystals  of  columbium  salt  are  treated  in  the  same  way,  metallic  zinc  added 
to  the  acid  solution  will  give  a  blue  coloration,  and  tannic  acid  an  orange-red 
coloration.  Tantalic  acid  fused  with  sodium  meta-phosphate  gives  a  colorless 
bead  (distinction  from  silica).  The  bead  moistened  with  FeSCX  and  heated  in 
the  inner  flame  is  not  colored  red.  Columbic  acid  fused  in  the  same  way  gives  a 
blue  bead  in  the  reducing  flame,  and  a  red  bead  by  addition  of  FeS04,  and  heat- 
ing in  the  flame. 

ESTIMATION 

Tantalum  and  columbium  occur  commonly  with  tungsten  in  nature.  In  the 
following  minerals,  however,  tantalum  and  columbium  form  the  more  important 
constituents : 

Columbite,  (Ta.Cb)2(Fe.Mn)06;  pyrochlore,  RCb206R(Ti.Th)3;  hatchet- 
tolite,  2R(Cb.Ta)206  or  R2(Cb-Ta)207;  fergusonite,  R(Cb-Ta)04;  yttrotan- 
talite,  RR(Cb-Ta)4015.4H20;  samarskite,  R3R2(Cb-Ta)602i. 

Tantalum  is  used  in  electric  light  filaments;  it  is  also  used  for  hardening 
steel  for  drills,  files,  cutting  edges,  watch  springs,  and  pen  points.  It  is  used 
in  rectifiers  for  alternating  currents. 


456        TUNGSTEN,  TANTALUM  AND  COLUMBIUM 

Solution  of  the  Sample 

The  statements  made  for  solution  of  the  sample  in  determinations  of  tungsten 
apply  here  also.  It  is  well  to  keep  the  following  facts  in  mind:  Tantalum  is 
insoluble  in  the  common  mineral  acids — hydrochloric,  nitric  and  sulphuric  acids, 
but  dissolves  in  hydrofluoric  acid.  Columbium  is  insoluble  in  hydrochloric, 
nitric  and  in  nitro-hydrochloric  acid,  but  dissolves  in  hot  concentrated  sul- 
phuric acid.  The  oxides  Ta206  and  Cb205  fused  with  KOH  form  soluble  salts. 
Cb206  (not  strongly  ignited)  is  soluble  in  acids,  from  which  (NH4)2S  and  NH4OH 
precipitate  columbic  acid  (containing  ammonia).  Freshly  precipitated  tantalic 
acid  is  soluble  in  acids,  and  reprecipitated  by  NH4OH.  The  acid  dissolves  readily 
inHF. 

Tantaliferous  Minerals.  Although  decomposition  may  be  effected  by  fusion 
with  potassium  acid  sulphate,  fusion  with  potassium  hydroxide  is  recommended 
as  being  the  best  flux  for  opening  the  minerals.  Simpson's  process  is  as  follows:1 

Three  grams  of  pure  potassium  hydroxide  are  fused  in  a  nickel  or  silver 
crucible  and  the  finely  powdered  mineral  (0.5  gram)  added,  the  contents  mixed 
by  gently  rotating  the  crucible  and  fusion  kept  at  a  dull  red  heat  for  ten  min- 
utes longer.  The  crucible  placed  in  a  hole  in  an  asbestos  board,  Fig.  65,  is 
heated  over  a  free  flame  for  half  an  hour,  the  sample  being  covered.  The  lid  is 
removed  and  allowed  to  cool  reversed,  if  any  material  clings  to  this.  The  cooled 
crucible,  placed  in  a  beaker,  is  two-thirds  filled  with  distilled  water,  and  a  clock- 
glass  immediately  placed  over  the  beaker.  After  the  violent  reaction  has  sub- 
sided the  contents  of  the  crucible  are  poured  into  about  10  cc.  of  dilute  hydro- 
chloric acid  (sp.gr.  1.08)  in  a  300-cc.  beaker,  and  the  crucible,  basin  and  the 
lid  washed  with  water,  followed  by  about  20  cc.  of  the  dilute  acid,  and  again 
with  water,  adding  the  washings  to  the  remaining  solution.  The  total  volume  of 
the  solution  should  occupy  from  80  to  100  cc.  A  drop  or  two  of  alcohol  are 
added  to  destroy  any  potassium  manganate  formed. 

Separations 

Isolation  of  Columbium  and  Tantalum  Oxides.  Separation  from  iron, 
manganese,  copper,  cobalt,  nickel,  calcium,  magnesium,  titanium,  and  tin.  The 
solution  obtained  above  is  boiled  with  5  to  10  cc.  of  hydrochloric  acid  (sp.gr. 
1.16)  (less  acid  may  be  used  if  titanium  is  absent).  Columbium  and  tantalum 
hydroxides  are  precipitated.  The  solution  is  now  diluted  to  200  cc.  and  boiled 
for  fifteen  minutes  longer  to  make  sure  that  the  precipitation  is  complete.  After 
settling,  the  clear  solution  is  decanted  through  a  close-grained  filter  and  the 
residue,  having  been  transferred  to  the  filter,  is  washed  with  dilute  hydrochloric 
acid  (sp.gr.  1.08)  until  the  washings  give  no  indication  of  iron.  The  residue  may 
contain  tantalum,  columbium,  tungsten,  silica,  antimony  and  tin.  The  greater 
part  of  the  tin,  titanium,  and  all  of  the  iron,  manganese,  cobalt,  nickel,  copper, 
calcium  and  magnesium  are  removed  in  the  filtrate. 

NOTES.  If  the  filtrate  becomes  turbid,  it  is  advisable  to  dilute  the  solution  and 
repeat  the  boiling  to  recover  the  columbium  and  tantalum  that  may  still  be  in  solution. 

In  the  presence  of  appreciable  amounts  of  titanium  a  soluble  double  chloride 
of  columbium  and  titanium  is  formed,  so  that  the  precipitation  of  columbium 

1 E.  S.  Simpson,  Chem.  News,  99,  243,  1909. 


TUNGSTEN,  TANTALUM  AND  COLUMBIUM         457 

is  not  complete.  (See  L.  Weiss  and  Landecker,  Chem.  News,  101,  2,  13,  26, 
1910.)  The  formation  of  this  compound  is  hindered  by  the  addition  of  an 
oxidizing  agent — sodium  nitrate — to  the  alkali. 

Removal  of  Tin,  Antimony,  Tungsten  and  Silica.  Tungsten  is  removed 
by  digesting  the  moist  precipitate  with  ammonium  hydroxide  or  sulphide,  tungsten 
being  soluble  in  these  reagents.  Antimony  and  Tin  are  also  removed. 

Silica  is  volatilized  by  heating  the  residue  with  sulphuric  and  hydrofluoric 
acids  according  to  the  standard  procedure. 

Tin.  The  oxide  may  be  reduced  with  hydrogen  passed  over  the  heated 
residue  within  a  boat  placed  in  a  combustion  tube.  The  tin  may  now  be  dissolved 
out  with  hydrochloric  acid. 

Determination  of  Columbium  and  Tantalum 

The  insoluble  residue  obtained,  freed  from  other  elmeents  by  the  procedures 
outlined,  is  ignited  at  a  red  heat  for  fifteen  or  twenty  minutes  and  the  residue 
weighed  as  Cb206+Ta206. 


URANIUM 

WILFRED  W.  SCOTT 

U,  at.  wt.  238.5;  sp.gr.  18.7;  m.p.  <1850°C.;1  oxides  UO2,  UO3, 
(oxide  U3O8,  formed  by 


DETECTION 

The  mineral  is  wanned  with  a  slight  excess  of  nitric  acid  (1  :  1)  until  decom- 
position is  complete.  The  solution  is  diluted  with  water  and  then  an  excess  of 
sodium  carbonate  added  and  the  mixture  boiled  and  filtered.  Sufficient  nitric 
acid  is  added  to  neutralize  the  carbonate,  and  after  expelling  the  C02  by  boil- 
ing, sodium  hydroxide  is  added  to  the  filtrate.  A  yellow  precipitate  is  formed 
in  presence  of  uranium.  The  precipitate  is  insoluble  in  an  excess  of  the  reagent, 
but  dissolves  in  the  ammonium  carbonate. 

Uranous  salts  are  green  or  blue  and  form  green  or  bluish-green  solutions, 
from  which  alkalies  precipitate  uranous  hydroxide,  reddish  brown,  insoluble  in 
excess,  but  readily  dissolved  by  ammonium  carbonate.  Uranous  salts  are  strong 
reducing  agents. 

Uranyl  salts  (IKVRa)  are  yellow.  Alkali  carbonates  give  a  yellow  precipitate, 
soluble  in  excess.  U02  is  regarded  as  a  basic  radical,  known  as  "  uranyl."  The 
radical  migrates  to  the  cathode,  upon  electrolysis  of  a  uranyl  solution.  Uranyl 
salts  are  more  stable  than  uranous  and  are  better  known. 


ESTIMATION 

The  element  occurs  in  the  following  minerals:  * 

Pitchblende,  or  uraninite,  containing  40  to  90%  U308. 

Autunite,  Ca(U02)2P2(V8H20,  contains  55  to  62%  UOS. 

Torbernite,  Cu(U02)2-P205-8H2p,  contains  57  to  62%  UOS. 

Carnotite,  a  vanadate  of  potassium  and  uranium,  V206-U203-K20-3H2O. 

Samarskite,  a  urano-tantalate  of  iron  and  yttrium,  etc.,  10  to  13%  UOs. 

Fergusonite,  a  columbate  of  cerium,  uranium,  yttrium,  calcium  and  iron. 

Nearly  all  the  silicates,  phosphates  and  zirconates  of  the  rare  earths  cont 
uranium. 

The  element  is  used  in  the  ceramic  industry  for  producing  yellow,  brown,  gray, 
and  velvety-black  tints.  It  produces  canary-yellow  glass.  It  is  used  as  a  mor- 
dant in  dyeing  of  silk  and  wool.  It  also  finds  use  in  photography.  The  metal  is 
used  in  cigarette-lighters  and  self-lighting  burners. 

1  Circular  35  (2d  Ed.),  U.  S.  Bureau  of  Standards. 

2  Thorpe,  "  Dictionary  of  Applied  Chemistry,"  Longmans,  Green   &  Co.    Cahen 
and  Wootten,  "The  Mineralogy  of  the  Rarer  Metals,"  Chas.  Griffin  &  Co.  and  J.  B. 
Lippincott  Co. 

458 


URANIUM  459 


Preparation  and  Solution  of  the  Sample 

The  element  dissolves  in  hydrochloric  and  in  sulphuric  acids;  less  readily  in 
nitric  acid.  It  is  insoluble  in  alkaline  solutions. 

The  oxide,  U02,  dissolves  in  nitric  acid  and  in  concentrated  sulphuric  acid. 

The  salts,  UF4  and  U02(HP04)2'4H20,  are  insoluble  in  water,  but  dissolve  in 
strong  mineral  acids. 

Solution  of  Ores.  One  gram  or  more  of  the  ore  is  dissolved  with  15  to  20  cc. 
of  aqua  regia,  by  placing  the  mixture  first  on  the  steam  bath  for  ten  to  fifteen 
minutes  and  then  gently  boiling  over  a  low  flame  or  on  the  hot  plate.  The  solu- 
tion is  taken  to  dryness,  silica  dehydrated  as  usual,  the  residue  treated  with  10 
cc.  of  hot  dilute  hydrochloric  acid  and  diluted  to  about  50  cc.  with  hot  water  and 
the  silica  filtered  off.  Uranium  passes  into  the  filtrate.  The  solution  is  now 
treated  as  directed  under  Separations.  If  much  silica  or  acid-insoluble  matter 
is  present,  this  should  be  treated  in  a  platinum  dish  with  strong  hydrofluoric  acid, 
and  evaporated  twice  on  the  steam  bath  with  hydrochloric  acid  to  expel  HF. 
The  residue,  dissolved  with  hydrochloric  acid  and  water,  is  added  to  the  first  por- 
tion of  solution  obtained. 

SEPARATIONS 

Separation  of  Uranium  from  Copper,  Lead,  Bismuth,  Arsenic,  Antimony 
and  the  Other  Members  of  the  Hydrogen  Sulphide  Group.  The  solution 
containing  uranium,  etc.,  having  an  acidity  of  about  5  cc.  strong  HC1  per  100  cc. 
of  solution,  is  saturated  with  hydrogen  sulphide  and  allowed  to  settle  and  again 
saturated  with  H2S.  The  sulphides  are  filtered  off  and  washed.  The  filtrate 
and  washings  contain  the  uranium  that  was  present  in  the  sample. 

Separation  of  Uranium  from  Iron  and  from  Elements  Having  Water- 
insoluble  Carbonates.  The  filtrate  from  the  hydrogen  sulphide  group  is  con- 
centrated to  about  150  cc.,  and  15  cc.  of  hydrogen  peroxide  added.  The  solution 
is  now  neutralized  with  sodium  carbonate  and  about  3  grams  added  in  excess. 
After  boiling  for  about  twenty  minutes,  renewing  the  water  evaporated,  the 
hydroxide  of  iron,  insoluble  carbonates,  etc.,  are  filtered  off,  washed  with  hot 
water  and  the  filtrate  set  aside  for  the  determination  of  uranium.  To  recover 
any  occluded  uranium  the  precipitate  is  dissolved  in  just  sufficient  nitric  acid  to 
effect  solution,  and  iron  again  precipitated  by  addition  of  hydrogen  peroxide  and 
sodium  carbonate  and  boiling  as  directed  above.  The  combined  filtrates  from 
this  precipitate  are  concentrated  to  about  250  cc. 

Separation  of  Uranium  from  Vanadium.  Procedure  1.  To  be  Used  in  the 
Determination  of  Uranium.  The  solution  obtained  as  directed,  under  the  previous 
separation,  is  acidified  with  nitric  acid,  adding  a  slight  excess,  and  C02  expelled 
by  boiling.  The  acid  is  now  neutralized  with  ammonia  (a  slight  permanent  pre- 
cipitate appearing),  and  then  10  cc.  of  strong  nitric  acid  is  added  (total  volume 
about  280-300  cc.).  Vanadium  is  now  precipitated  as  lead  vanadate  by  adding 
10  cc.  of  a  25%  solution  of  lead  acetate,  followed  by  sufficient  strong  ammonium 
acetate  solution  (1  vol.  strong  NH3OH+1  vol.  H20+sufficient  glacial  acetic  acid 
to  neutralize  NH4OH)  to  neutralize  the  free  nitric  acid.  The  precipitated  vana- 
date, which  is  insoluble  in  the  acetic  acid  formed  by  the  reaction,  is  allowed  to 
settle  for  a  couple  of  hours  on  the  steam  bath  and  is  then  filtered  off  and  washed 
once,  the  uranium  passing  into  the  filtrate.  To  recover  any  occluded  uranium 


460  URANIUM 

the  precipitate  is  dissolved  in  the  least  amount  of  nitric  acid  required,  the  solution 
neutralized  with  ammonia,  diluted  to  about  100  cc.  and  5  cc.  nitric  acid  added 
followed  by  2  to  3  cc.  of  lead  acetate  solution.  The  vanadate  of  lead  is  again 
precipitated  by  neutralizing  the  free  acid  with  ammonium  acetate.  The  vanadate 
is  filtered  off  and  washed  with  warm  water.  The  filtrate  containing  the  uranium 
is  concentrated  to  about  400  cc. 

In  order  to  remove  the  lead  present  in  the  filtrate,  due  to  the  excess  of  the 
acetate  reagent,  about  10  cc.  of  strong  sulphuric  acid  are  added,  the  bulk  of  the 
lead  precipitated  as  the  sulphate  is  filtered  off,  and  the  PbS04  washed  with  cold 
water.  The  filtrate  is  neutralized  with  ammonia  and  freshly  prepared  (NH4)HS 
added  until  the  solution  appears  yellow  and  the  remaining  lead  and  all  the  uranium 
are  thrown  out  as  sulphides.  The  precipitate  is  allowed  to  settle  on  the  steam 
bath,  and  then  filtered  off  and  washed  with  a  small  amount  of  warm  water.  This 
is  now  dissolved  with  hot  dilute  nitric  acid  (1  :  2),  and  the  nitric  acid  then 
expelled  by  taking  the  solution  to  S03  fumes  with  about  5  cc.  of  strong  sulphuric 
acid.  The  cooled  residue  is  taken  up  with  cold  water,  boiled  and  the  lead  sul- 
phate allowed  to  settle  until  the  solution  is  cold.  The  precipitate  is  filtered  off 
and  washed  with  water  slightly  acidified  with  sulphuric  acid.  Uranium  passes 
into  the  filtrate.  If  alumina  is  present  in  the  sample  it  must  now  be  removed 
according  to  the  directions  following  Procedure  2,  before  precipitation  of 
uranium. 

Procedure  2.  To  be  Used  in  the  Volumetric  Determination  of  Uranium. 
The  separation  of  vanadium  from  uranium  may  be  effected  by  precipitation  of 
the  latter  as  a  phosphate  according  to  the  following  procedure.  The  solution  is 
heated  and  allowed  to  run  in  a  small  stream  through  a  funnel  with  constricted 
stem,  into  a  boiling  solution  of  15  grams  of  ammonium  acetate,  5  grams  of  micro- 
cosmic  salt  dissolved  in  100  cc.  of  water  containing  about  5  cc.  of  glacial  acetic 
acid.  A  rod,  with  a  cup-shaped  tip,  placed  in  the  solution  prevents  bumping. 
The  mixture  is  allowed  to  boil  for  a  few  minutes,  the  beaker  is  then  removed  from 
the  keat  and  the  precipitate  allowed  to  settle.  This  is  now  transferred  to  a  filter 
after  first  decanting  off  the  clear  solution.  It  is  washed  once  with  hot  water, 
then  washed  back  into  the  beaker  and  dissolved  in  a  small  amount  of  hot  dilute 
nitric  acid,  the  precipitate  clinging  to  the  filter  being  dissolved  off  by  the  acid, 
which  is  allowed  to  run  through  the  filter  into  the  beaker.  This  nitric  acid  solu- 
tion containing  the  vanadium  is  diluted  to  about  75  cc.  and  the  uranium  (together 
with  aluminum  if  present)  again  precipitated  as  the  phosphate  according  to  the 
procedure  described.  The  precipitate  is  again  transferred  to  the  filter  previously 
used,  and  washed  off  with  hot  water  four  or  five  times.  Vanadium  passes  into 
the  nitrate.  The  phosphate  is  now  dissolved  off  the  filter  with  15  cc.  of  hot  dilute 
sulphuric  acid  (1  :  3),  and  uranium  determined  by  titration  with  permanganate 
according  to  the  directions  given  under  the  volumetric  method  described  later. 

Removal  of  Alumina  in  the  Gravimetric  Method  for  Determining  Uranium. 
Alumina  would  interfere  in  the  gravimetric  method,  hence  its  removal  is  neces- 
sary if  present.  The  filtrate  obtained  after  removal  of  iron  and  freed  from  vana- 
dium, if  this  is  present  in  the  original  sample,  is  nearly  neutralized  with  ammonia. 
Now  sufficient  powdered  ammonium  carbonate  is  added  to  the  cooled  solution 
to  precipitate  the  alumina  and  react  with  the  uranium,  and  about  2  grams  in 
excess.  If  the  precipitate  is  bulky  and  is  at  all  yellow,  it  is  dissolved  in  a  little 
sulphuric  acid  and  again  precipitated  as  before.  The  aluminum  hydroxide  is 
filtered  off  and  washed  with  hot  water.  Uranium  is  determined  in  the  filtrate. 


URANIUM  461 

GRAVIMETRIC    DETERMINATION     OF    URANIUM    AS    THE 

OXIDE,     U3O8 

Procedure.  The  filtrate  containing  the  uranium,  as  obtained  according  to 
the  method  given,  is  made  slightly  acid  with  hydrochloric  or  sulphuric  acid  and 
boiled  to  expel  the  CO2.  Ammonium  hydroxide  (free  from  carbonate)  is  now 
added  in  slight  excess  and  the  solution  brought  to  boiling.  The  precipitate  is 
allowed  to  settle,  then  filtered  onto  filter  paper  or  into  a  weighed  Gooch  crucible 
and  washed  five  or  six  times  with  a  2%  solution  of  ammonium  nitrate  and  finally 
once  with  water.  It  is  now  dried  and  ignited  to  the  oxide  U308,  in  which  form  it 
is  weighed. 

U308X0.8482=U. 

NOTES.  The  purity  of  the  oxide  may  be  ascertained  by  dissolving  in  HNO3  and 
testing  for  vanadium  with  H2O2  and  for  A12O3  by  adding  (NH4)2CO3. 

Treadwell  recommends  that  the  oxide  be  reduced  by  hydrogen  passed  over  the 
red-hot  residue,  the  brown  UO2  being  formed.  The  oxide  is  cooled  in  a  current  of 
hydrogen. 

VOLUMETRIC    DETERMINATION   OF   URANIUM   BY 
REDUCTION  AND  OXIDATION 

Introduction.  The  determination  of  uranium  by  oxidation  of  the  lower  oxide 
U02  to  U03  may  be  accomplished  with  great  accuracy  by  means  of  permanganate 
in  precisely  the  same  manner  as  in  the  determination  of  iron,  the  Jones  reductor 
being  used  for  the  reduction  of  the  uranic  salt  to  the  uranous  form.  The  metal 
must  be  in  solution  either  as  a  sulphate,  a  chloride  or  an  acetate,  but  not  as  a 
nitrate.  If  present  as  a  chloride  the  usual  preventative  solution  of  phosphoric 
acid  and  manganous  sulphate  solution  must  be  present  as  in  case  of  the  titration 
of  a  chloride  of  iron,  hence  a  sulphate  solution  is  to  be  preferred.  Although  the 
degree  of  reduction  varies  with  conditions,  it  is  found  that  with  brief  contact 
with  the  oxygen  of  the  air  the  oxide  U02  is  formed. 

Procedure.  Solution.  The  method  for  preparation  of  the  sample,  isolation 
of  the  uranium,  has  been  given  under  Preparation  and  Solution  of  the  Sample 
and  Separations.  The  solution  from  the  ammonium  carbonate  precipitate  is 
acidified  with  sulphuric  acid  and  boiled  to  expel  the  C02. 

Reduction.  The  uranium  sulphate  solution,  diluted  to  a  volume  of  100  to 
150  cc.,  containing  one-sixth  of  its  volume  of  sulphuric  acid,  is  heated  nearly  to 
boiling  and  the  organic  matter  that  may  be  present  oxidized  by  addition  of  just 
sufficient  potassium  permanganate  solution  to  produce  a  faint  pink  color.  Fifteen 
to  20  cc.  of  dilute  sulphuric  acid  are  passed  through  the  18-in.  column  of  zinc  in 
the  Jones  reductor,  followed  by  the  hot  uranium  sulphate  solution,  flowing  very 
slowly,  fifteen  to  twenty-five  minutes  being  required  for  0.2  gram  uranic  oxide, 
thirty  to  forty  minutes  for  0.3  gram  of  the  oxide,  care  being  taken  that  the  liquid 
in  the  reductor  always  covers  the  zinc.2  The  uranic  solution  is  followed  by  10  to 
15  cc.  of  dilute  1  I  6  solution  of  sulphuric  acid. 

1  Oxidation  of  lower  oxides  by  air  to  UO2".     O.  S.  Pulman,  Jr.  Am.  Jour.  Sc.  (4), 

J.U.    *-*-./. 

2  Hydrogen  dioxide  formed  by  nascent  hydrogen  in  contact  with  air  would  vitiate 
results. — Gooch. 


462  URANIUM 

Titration.  The  olive-green  solution  is  poured  into  a  beaker  or  casserole. 
The  lower  oxides  are  immediately  oxidized  to  U02  by  the  air,  as  seen  by  the  slight 
change  of  color  to  sea  green.  The  hot  solution  is  now  titrated  with  tenth  normal 
permanganate.  The  solution  during  titration  gradually  becomes  more  and  more 
yellowish  green,  as  the  highest  oxidation  is  approached,  until  a  faint  pink  color 
is  obtained.  With  large  amounts  of  uranium  the  color  appears  a  yellowish  pink. 

One  cc.  N/10  KMn04  =0.11925  gram  U. 
NOTE.     55.85  grams  Fe  is  equivalent  to  119.25  grams  U. — Sutton. 


VANADIUM 

WILFRED  W.  SCOTT 

V,  at.wt.  51.0;  sp.gr.  6.025;  m.p.  1720°  C.;  oxides  V2O,  V2O2,  V2O8,  V2O4, 
V2O5;  vanadates — meta  NaVO3,  ortho  Na3VO4,  pyro  Na4V2O7,  tetra 
Na3HV6017,  hexa  Na2H2V6O17. 

DETECTION 

Ammonium  Sulphide  or  Hydrogen  Sulphide  passed  into  an  ammoniacal 
solution  of  vanadium  precipitates  brown  V2S5,  soluble  in  an  excess  of  alkali  sul- 
phide and  in  alkalies,  forming  the  brownish-red  thio-  solution,  from  which  the 
sulphide  may  be  reprecipitated  by  acids. 

Reducing  Agents.  Metallic  zinc,  sulphites  (SO*),  oxalic  acid,  tartaric  acid, 
sugar,  alcohol,  hydrogen  sulphide,  hydrochloric  acid,  hydrobromic  and  hydriodic 
acids  (KI)  reduce  the  acid  solutions  of  vanadates  with  formation  of  a  blue-colored 
liquid.  (See  Volumetric  Methods.)  Reduction  is  hastened  by  heating. 

Hydrogen  Peroxide  added  to  a  cold  acid  solution  of  vanadium  produces  a 
brown  color,  changing  to  blue  upon  application  of  heat. 

Solid  Ammonium  Chloride  added  to  a  neutral  or  slightly  alkaline  solution 
of  a  vanadate  precipitates  the  colorless,  crystalline  salt,  NH4V03,  insoluble  in 
ammonium  chloride.  The  ammonium  metavanadate  ignited  is  decomposed, 
ammonia  volatilizing  and  the  red  pentoxide  of  vanadium  remaining  as  a  residue. 

The  colorless  ammonium  vanadate  solution  becomes  yellow  when  slightly 
acidified.  Acids  produce  a  red  color  when  added  to  the  solid  salt. 

The  oxide,  F205,  is  distinguished  from  Fe203  by  the  fact  that  it  fuses  very  readily 
with  the  heat  of  Bunsen  burner,  whereas  the  oxide  of  iron,  Fe203,  is  infusible  in 
the  heat  of  a  blast  lamp.  M.p.  V205=658°  C.;  m.p.  Fe203  =  1548°  C. 

Comparison  of  Vanadium  and  Chromium  Salts.  Vanadium,  like  Chromium, 
forms  a  soluble  salt  upon  fusion  with  sodium  carbonate  and  potassium  nitrate 
or  with  sodium  peroxide.  The  solution  of  vanadates  and  of  chromates  are  yellow 
or  orange;  the  color  of  the  chromate  becomes  more  intense  when  strongly  acidified, 
whereas  that  of  the  vanadate  is  reduced.  The  yellow  color  of  the  vanadate  solu- 
tion is  destroyed  by  boiling  with  an  excess  of  alkali,  but  may  be  restored  by  neu- 
tralizing the  alkali  with  acid.  The  chromate  color  is  not  destroyed.  (Yellow 
with  alkalies,  orange  in  acid  solution.)  Silver  nitrate  produces  a  dark-maroon 
precipitate  with  a  soluble  chromate  and  an  orange-colored  precipitate  with  a 
vanadate;  mercurous  nitrate  produces  a  red-colored  precipitate  with  chromates 
and  a  yellow  with  vanadates.  Vanadates  are  also  distinguished  from  chromates  by 
the  reduction  test;  reducing  agents  such  as  a  soluble  sulphite,  or  sulphurous  acid 
added  to  acid  solutions,  form  a  blue-colored  liquid  with  vanadates  and  a  green  color 
with  chromates.  Ammonium  hydroxide  added  in  excess  to  the  cold  reduced  solutions 

1  Reduction  with  zinc  is  rapid  with  vanadates,  much  less  vigorous  with  chromates. 
V206  reduced  to  V2O2,  color  changes  to  blue,  green,  lavender  and  finally  violet.  SO2 
or  H2S  reduces  V2O6  to  V2O4.  V2O2  forms  vanadyl  salts. 

463 


464  VANADIUM 

gives  a  brown  color,  or  a  brown  to  dirty  green  precipitate  with  vanadium,  and  violet 
or  lavender  color  or  a  light  green-colored  precipitate  with  chromium,  depending 
upon  the  concentration  of  the  solutions.  Hydrogen  peroxide  added  to  the  reduced 
cold  acid  solutions  changes  the  vanadium  blue  to  reddish  brown;  the  chromium 
green  remains  unchanged. 

Detection  of  Vanadium  in  Steel.  Five  grams  of  the  sample  are  dissolved 
in  dilute  nitric  acid,  the  nitrous  fumes  boiled  off,  the  solution  cooled,  and  an 
excess  of  sodium  bismuthate  added.  After  filtering  through  an  asbestos  filter 
an  excess  of  concentrated  ferrous  sulphate  solution  is  added,  and  the  solution 
divided  into  two  equal  parts  in  test-tubes.  To  one  portion  10  cc.  of  hydrogen 
peroxide  are  added  and  to  the  other  10  cc.  of  water.  If  vanadium  is  present  the 
peroxide  solution  will  show  a  deeper  color  than  the  untreated  solution.  A  deep 
red  color  is  produced  with  high  vanadium  steels  and  a  brownish-red  with  low. 
Since  titanium  also  causes  this  color,  it  would  interfere,  if  it  were  not  for  the 
fact  that  the  color  produced  with  titanium  is  destroyed  by  hydrofluoric  acid  and 
fluorides,  whereas  that  of  vanadium  is  not.  In  presence  of  titanium,  5  cc.  of  hydro- 
fluoric acid  are  added  to  the  treated  sample. 

The  brown  color  produced  by  hydrogen  peroxide,  with  vanadium  solutions, 
will  remain  in  the  water  portion  when  shaken  with  ether.  The  ether  layer  is 
colored  a  transient  blue  in  presence  of  chromium. 

ESTIMATION 

The  materials  in  which  the  estimation  of  vanadium  is  desired  may  be  sur- 
mised from  the  following  facts:  Industrial  application.  Vanadium  is  used  in 
special  iron  and  steel  alloys.  It  increases  the  strength  of  steel  as  well  as  the 
compression  power,  without  loss  of  hardness,  and  increases  the  resistance  to 
abrasion;  hence  vanadium  steels  are  used  in  locomotive  and  automobile  cylinders, 
pistons,  bushings  and  in  all  parts  of  machines  subject  to  jar.  It  is  used  in  high- 
speed tools,  vanadium  bronzes  for  gears,  trolley  wheels,  etc.  It  is  used  in  indelible 
inks,  and  in  the  form  of  alkali  vanadates  and  hypovanadates  it  serves  as  a 
mordant  for  aniline  black  on  silk,  for  calico  printing  and  like  uses.  Vanadium 
salts  are  used  in  ceramics  where  a  golden  glaze  is  desired. 

The  element  occurs  widely  distributed  in  minute  quantities.  It  is  found  in 
iron  ores,  hence  occurs  in  blast-furnace  slags  as  the  oxide,  V2O6.  The  principal 
ores  are: 

Patronite,  a  sulphide  of  vanadium  containing  28  to  34%  V206,  associated  with 
pyrites  and  carbonaceous  matter;  the  principal  source  of  vanadium. 

Vanadinite,  (PbCl)Pb4(V04)3,  containing  8  to  21%  V205. 

Carnotite,  K20.2U02.V2CV3H20,  contains  19  to  20%  V,06. 

Desdoizite,  (PbZn)2NV06,  contains  20  to  22%  V206. 

Roscoelite,  a  vanadium  mica  with  variable  composition. 

Eusynchite,  contains  17  to  24%  V206. 

Cuprodescloizite,  (PbZnCu)2(OH)V04,  contains  17  to  22%  V206. 

Calciovolborthite,  (CuCa)2(OH)V04,  contains  37  to  39%  V204. 

Vanadium  occurs  in  ores  of  copper  and  lead,  it  is  present  in  certain  clays  and 
basalts,  in  soda  ash,  phosphate  soda,  and  in  some  hard  coals. 


VANADIUM  465 


Preparation  and  Solution  of  the  Sample 

In  decompositon  of  the  material  for  analysis  the  following  facts  regarding 
the  solubility  of  the  metal,  its  oxides  and  principal  salts,  will  be  helpful: 

Element.  The  metal  is  not  attacked  by  aqueous  alkalies,  but  is  soluble  by 
fusion  with  potassium  or  sodium  hydroxide,  and  sodium  carbonate  containing 
potassium  nitrate.  It  is  insoluble  in  dilute  hydrochloric  and  sulphuric  acids. 
It  dissolves  in  concentrated  sulphuric  acid  and  in  dilute  and  concentrated  nitric 
acid  forming  blue  solutions. 

Oxides.  V202  is  easily  soluble  in  dilute  acids,  giving  a  lavender-colored 
solution. 

V203  is  insoluble  in  hydrochloric  and  sulphuric  acids,  and  in  alkali  solutions. 
It  dissolves  in  hydrofluoric  acid,  and  in  nitric  acid. 

V204  is  easily  soluble  in  acids,  forming  blue-colored  solutions.  It  dissolves 
in  alkali  solutions. 

V205  is  soluble  in  acids,  alkali  hydroxide  and  carbonate  solutions.  Insoluble 
in  alcohol  and  acetic  acid. 

Salts.  Ammonium  meta  vanadate,  NH4V03,  is  slightly  soluble  in  cold  water, 
readily  soluble  in  hot  water.  The  presence  of  ammonium  chloride  renders  the 
salt  less  soluble.  The  vanadates  of  lead,  mercury  and  silver  are  difficultly  soluble 
in  water.  These  are  dissolved,  or  are  transposed  by  mineral  acids,  the  vanadium 
going  into  solution;  i.e.,  lead  vanadate  treated  with  sulphuric  acid  precipitates 
lead  sulphate  and  vanadic  acid  passes  into  solution. 

General  Procedure  for  Decomposition  of  Ores.  One  gram  (or  more)  of  the 
finely  divided  material  is  placed  in  a  large  platinum  crucible  together  with  five 
times  its  weight  of  a  mixture  of  sodium  carbonate  and  potassium  nitrate 
(Na2C03  =  10,  KN03  =  1).  The  product  is  heated  to  fusion  over  a  blast  lamp 
and,  when  molten,  about  0.5  to  1  gram  more  of  the  nitrate  added  in  small  por- 
tions. (Caution — platinum  is  attacked  by  KN03.  A  large  excess  of  Na2C03 
tends  to  prevent  this.)  The  material  should  be  kept  in  quiet  fusion  for  ten  to 
fifteen  minutes,  when  most  of  the  ores  will  be  completely  decomposed.  The 
cooled  fusion  is  extracted  with  boiling  water,  whereby  the  vanadium  goes  into 
solution.  Arsenic,  antimony,  phosphorus,  molybdenum,  tungsten  and  chromium 
pass  into  solution  with  the  vanadium.  These  must  be  removed  in  the  gravimetric 
determination  of  this  element.  (Iron  remains  insoluble  in  the  water  extract.) 

Should  there  be  any  undecomposed  ore,  the  residue  from  the  water  extract 
will  be  gritty.  If  this  is  the  case,  a  second  fusion  with  the  above  fusion  mixture 
should  be  made. 

Small  amounts  of  occluded  vanadium  may  be  recovered  from  the  water-insol- 
uble residue  by  dissolving  this  in  nitric  acid  and  pouring  the  solution  into  a 
boiling  solution  of  sodium  hydroxide.  Vanadium  remains  in  solution. 

Vanadium  may  be  determined  volumetrically  after  removal  of  the  hydrogen 
sulphide  group,  by  titration  with  potassium  permanganate  according  to  the 
procedure  given  later.  The  isolation  and  determination  of  vanadium  by  the 
gravimetric  procedures  are  given  in  detail  later. 

Ores  and  Material  High  in  Silica.  The  sample  is  treated  in  a  platinum  dish 
with  about  ten  times  its  weight  of  hydrofluoric  acid  (10  to  50  cc.)  and  2  to  5  cc. 
of  strong  sulphuric  acid.  The  silica  is  expelled  as  SiF4  and  the  hydrofluoric  acid 
driven  off  by  taking  the  solution  to  S03  fumes.  The  residue  is  extracted  with  hot 
water  containing  a  little  sulphuric  acid.  Any  undissolved  residue  may  be  brought 


466  VANADIUM 

into  solution  by  fusion  with  potassium  acid  sulphate,  KHS04,  and  extraction  with 
hot  water  containing  a  little  sulphuric  acid.  By  this  treatment  the  iron  passes 
into  solution  with  vanadium. 

Products  Low  in  Silica.  Decomposition  may  be  effected  by  fusion  in  a  nickel 
crucible  with  sodium  peroxide  and  extraction  with  water.  The  water  should  be 
added  cautiously,  as  the  reaction  is  vigorous.  One  gram  of  the  finely  divided  ore 
is  intimately  mixed  with  3  to  4  grams  of  Na202  and  1  gram  of  the  peroxide  placed 
on  the  charge.  The  material  is  then  fused  as  stated.1 

Iron  and  Steel.  The  solution  of  the  sample,  isolation  of  vanadium  and  its 
volumetric  determination  are  given  at  the  close  of  the  chapter. 

Alloys.  These  may  be  decomposed  with  nitric  acid,  or  aqua  regia.  The 
isolation  of  vanadium  with  mercurous  nitrate  or  lead  acetate  are  given  under  the 
gravimetric  methods. 

SEPARATIONS 

Fusion  with  sodium  carbonate  and  potassium  nitrate  and  extraction  of  the 
melt  with  water  effect  a  separation  of  vanadium  from  most  of  the  metals,  which 
remain  insoluble  as  carbonates  or  oxides.  Arsenic,  molybdenum,  tungsten, 
chromium  and  phosphorus,  however,  pass  into  the  filtrate  with  vanadium. 

Removal  of  Arsenic.  This  element  generally  occurs  in  vanadium  ores.  It 
may  be  removed  when  desired,  by  acidifying  the  water  extract  of  the  fusion  with 
sulphuric  acid,  and  after  reducing  arsenic  with  S02,  precipitating  the  sulphide, 
As2S3  with  H2S  gas.  Vanadium  passes  into  the  filtrate. 

Removal  of  Molybdenum.  The  procedure  is  similar  to  that  used  for  arsenic, 
with  the  exception  that  the  sulphide  of  molybdenum  is  best  precipitated  under 
pressure.  The  solution  in  a  pressure  flask  is  treated  with  H2S.  The  flask  is 
stoppered  and  heated  in  the  steam  bath.  It  is  advisable  to  resaturate  the  solu- 
tion with  H2S  before  filtering  off  the  sulphide. 

Separation  from  Phosphoric  Acid.  In  the  gravimetric  procedure  phosphorus 
and  vanadium  are  precipitated  together  as  mercuric  vanadate  and  phosphate. 
The  mercury  is  expelled  by  heat  and  the  oxides  V205  and  P205  weighed.  (V205  in 
presence  of  P206  does  not  melt  as  it  does  in  pure  form,  but  only  sinters.)  The 
oxides  are  fused  with  an  equal  weight  of  sodium  carbonate,  the  melt  dissolved 
in  water,  then  acidified  with  sulphuric  acid  and  vanadium  reduced  to  the  vanadyl 
condition  by  S02  gas.  The  excess  of  S02  is  expelled  by  boiling  and  passing  in 
C02.  Phosphoric  acid  is  now  precipitated  with  ammonium  molybdate  (50  cc. 
of  a  solution  containing  75  grams  ammonium  molybdate  dissolved  in  500  cc.  of 
water  and  poured  into  500  cc.  nitric  acid — sp.  gr.  1.2)  in  presence  of  a  large  amount 
of  ammonium  nitrate  and  a  little  free  nitric  acid.  It  is  advisable  to  dissolve  the 
precipitate  in  ammonia  and  reprecipitate  in  presence  of  additional  ammonium 
molybdate  and  nitrate  by  acidifying  with  nitric  acid.  The  equivalent  P206  is 
deducted  from  the  weight  of  the  combined  oxides,  the  difference  being  due  to 
V206. 

NOTE.  Vanadium  must  be  completely  reduced  to  the  vanadyl  form,  as  vanadic  acid 
will  precipitate  with  phosphoric  acid. 

1  Direct  reduction  and  titration  of  vanadium  in  presence  of  a  large  accumulation  of 
salts  leads  to  erroneous  results.  The  vanadium  should  be  separated  by  precipitation 
with  lead  acetate. 


VANADIUM  467 

Separation  of  Vanadium  and  Chromium.  A  volumetric  procedure  for  deter- 
mining vanadium  and  chromium  in  the  presence  of  one  another  is  given.  If  a 
separation  is  desired  the  following  procedures  may  be  used : 

A.  The  solution  is  acidified  with  nitric  acid.     If  hydrochloric  acid  is  present 
it  is  expelled  by  taking  to  near  dryness  twice  with  nitric  acid,  the  residue  is  taken 
up  with  water  and  SO2  gas  passed  in  to  completely  reduce  the  vanadium.    This 
solution  is  poured  into  a  boiling  solution  of  10%  sodium  hydroxide.    After  boiling 
a  few  minutes,  the  solution  is  filtered  and  the  residue  washed.    The  filtrate  con- 
tains vanadium,  the  residue  chromium.     It  is  advisable  to  pour  the  filtrate  into 
additional  caustic  to  remove  the  small  amount  of  chromium  that  passes  into 
the  solution. 

B.  One  hundred  cc.  of  the  neutral  solution  is  made  acid  with  about  15  cc.  of 
glacial  acetic  acid  and  hydrogen  peroxide  added.    The  solution  is  boiled  for  a  few 
minutes.     Chromium  is  thereby  reduced  to  Cr203,  whereas  vanadium  appears  as 
V205.    Lead  acetate  will  now  precipitate  lead  vanadate,  the  reduced  chromium 
remaining  in  solution.     The  lead  vanadate  now  treated  with  strong  sulphuric 
acid  is  decomposed  upon  heating.    Addition  of  water  precipitates  PbS04,  the 
vanadium  remaining  in  solution. 


GRAVIMETRIC  METHODS 

The  following  procedures  presuppose  that  vanadium  is  present  in  the  solution 
as  an  alkali  vanadate,  the  form  in  which  it  occurs  in  the  water  extract  from  a 
fusion  with  sodium  carbonate  and  potassium  nitrate,  as  is  described  in  the  method 
of  solution  of  ores  containing  vanadium.  Chromium,  arsenic,  phosphorus,  molyb- 
denum and  tungsten,  if  present  in  the  ore  will  be  found  in  this  solution. 

Mercurous  Nitrate   Method   for  Determination   of  Vanadium — 

Gravimetric l 

Principle.  A  nearly  neutral  solution  of  mercurous  nitrate  precipitates 
vanadium  completely  from  its  solution.  The  dried  precipitate  ignited  forms 
the  oxide,  V205,  mercury  being  volatilized. 

Procedure.  To  the  alkaline  solution  or  an  aliquot  portion  of  the  water 
extract  from  the  sodium  carbonate  potassium  nitrate  fusion  nearly  neutralized  with 
nitric  acid  2  (the  solution  should  remain  slightly  alkaline)  is  added  drop  by  drop, 
a  nearly  neutral  solution  of  mercurous  nitrate  in  slight  excess  of  that  necessary  to 
precipitate  completely  the  vanadium  present,  as  may  be  determined  by  allowing 
the  precipitate  to  settle  and  adding  a  few  drops  more  of  the  reagent.  The  mixture 
is  heated  to  boiling  and  then  placed  on  the  water  bath  or  steam  plate  and  the  gray- 
colored  precipitate  allowed  to  settle.  The  precipitate  is  washed  several  times 

1  Method  of  Rose.     J.  W.  Mellor,  "  A  Treatise  on  Quantitative  Inorganic  Analysis." 

2  Should  the  alkaline  solution  of  the  vanadate  be  made  acid,  nitrous  acid,  from 
the  nitrate  fusion,  will  be  liberated  and  cause  reduction  of  the  vanadate  to  the  vanadyl 
salt,  in  which  form  it  is  not  precipitated  by  mercurous  nitrate;  hence  great  care  should 
be  used  in  neutralizing  the  alkaline  solution  to  avoid  making  it  acid.     It  is  a  good  prac- 
tice to  measure  the  acid  added,  having  determined  on  an  aliquot  portion  the  amount 
necessary  to  add  to  neutralize  the  solution.     This  is  readily  accomplished  when  a 
comparatively  large  sample  has  been  prepared  for  analysis  and  an  aliquot  portion 
taken  for  analysis,  several  determinations  being  made  on  the  same  fusion. 


468  VANADIUM 

with  water  containing  a  few  drops  of  mercurous  nitrate,  washing  once  or  twice 
by  decantation  and  finally  on  the  filter  paper.  The  precipitate  is  dried,  then 
ignited  in  a  porcelain  crucible  in  a  hood  over  a  Bunsen  burner  to  a  red  heat.  The 
fused  red  residue  is  V205. 

V206X0.5604=V. 

Gravimetric  Method  of  Determining  Vanadium  by  Precipitation 

with  Lead  Acetate l 

Principle.  From  a  weakly  acetic  acid  solution,  vanadium  is  quantitatively 
precipitated  by  lead  acetate.  The  precipitate  is  dissolved  in  nitric  acid,  lead 
removed  as  a  sulphate,  and  vanadium  determined  in  the  filtrate  by  taking  to 
dryness  and  igniting  to  the  oxide,  V205. 

Procedure.  To  the  alkaline  solution  or  an  aliquot  portion  obtained  by 
extraction  of  the  carbonate  fusion  of  the  ore  with  water,  just  sufficient  amount 
of  nitric  acid  is  added  to  nearly  neutralize  the  alkali  present,  as  in  the  case  of 
the  method  described  for  precipitation  of  vanadium  by  mercurous  nitrate,  and 
then  a  10%  solution  of  lead  acetate  is  added  in  slight  excess  with  continuous 
stirring.  The  precipitate  is  allowed  to  settle  on  the  steam  bath.  The  vanadate, 
first  appearing  orange  colored,  will  fade  to  white  upon  standing.  The  lead  vana- 
date is  filtered  and  washed  free  of  the  excess  of  lead  acetate  with  water  containing 
acetic  acid.  The  precipitate  is  washed  into  a  porcelain  dish  with  a  little  dilute 
nitric  acid,  and  brought  into  solution  by  warming  the  lead  salt  with  nitric  acid. 
To  this,  the  ash  of  the  incinerated  filter  is  added.  Sufficient  sulphuric  acid  is 
added  to  precipitate  completely  the  lead,  and  the  solution  taken  to  small  volume 
on  the  water  bath  and  then  to  S03  fumes,  but  not  to  dryness.  About  100  cc.  of 
water  are  added  and  the  mixture  filtered;  lead  sulphate  will  remain  upon  the  filter 
and  the  vanadium  will  be  in  solution.  The  lead  sulphate  is  washed  free  of 
vanadium  (i.e.,  until  the  washings  no  longer  give  a  brown  color  with  hydrogen 
peroxide). 

The  filtrate  containing  all  the  vanadium  is  evaporated  to  small  volume  in  the 
porcelain  dish,  then  transferred  to  a  weighed  platinum  crucible  and  evaporated 
to  dryness  on  the  water  bath  and  finally  the  residue  (V206)  heated  to  a  dull  red- 
ness over  a  Bunsen  flame. 

V205X0.5604=V. 

NOTES.  Lead  may  be  separated  from  the  vanadium  by  passing  H2S  through  the 
nitric  acid  solution,  the  excess  of  H2S  volatilized  by  boiling  and  the  liberated  sulphur 
filtered  off.  The  filtrate  is  evaporated  to  dryness  and  the  vanadium  ignited  with  a 
few  drops  of  nitric  acid  to  the  oxide  V2O6. 

Lead  may  also  be  separated  as  lead  chloride  in  the  presence  of  alcohol,  the  solu- 
tion taken  to  dryness  and  vanadium  oxidized  by  addition  of  nitric  acid  and  ignited 
to  V206. 

1  Method  by  Roscoe,  Ann.  Chem.  Pharm.,  Supplement  8,  102,  1872.  Treadwell  and 
Hall,  "  Analytical  Chemistry,"  p.  305. 


VANADIUM  469 

VOLUMETRIC  PROCEDURES  FOR  THE  DETERMINATION 

OF  VANADIUM 

Reduction  of  the  Vanadate,  V2O5,  to  Vanadyl  Condition,  V2O4, 
and  Reoxidation  with  Potassium  Permanganate 

Principle.  Vanadium  in  solution  as  a  vanadate  is  reduced  to  the  vanadyl  salt 
by  H2S  or  S02,  the  excess  of  the  reducing  agent  expelled  and  the  solution  titrated 
with  standard  KMn04,  vanadium  being  oxidized  to  its  highest  form,  V205. 

Reactions,    a.  V205+S02  =  V204+S03.    b.  V204+0=V205.    Hence 


At  wt  V 
N/10  sol.  = — '—— - —  grams  to  the  liter. 


10 

Procedure.  An  aliquot  portion  of  the  solution  containing  vanadium,  as 
obtained  by  one  of  the  procedures  given  for  the  solution  of  the  sample,  is  taken 
for  analysis;  dilute  sulphuric  acid  (1  :  1)  is  added  to  acid  reaction  and  5  cc.  of  acid 
per  100  cc.  of  solution  added  in  excess.  The  vanadium  content  should  be  not 
over  0.5  gram  V  when  a  tenth  normal  permanganate  is  used  for  the  titration. 
//  arsenic  or  molybdenum  is  present  these  may  be  removed  from  the  solution  by 
passing  in  H2S.  The  insoluble  sulphides  are  filtered  off  and  washed  with  H2S 
water.  The  filtrate  is  boiled  down  to  two-thirds  of  its  volume  and  the  sulphur 
filtered  off.  In  the  absence  of  members  of  the  H2S  group,  this  portion  of  the  pro- 
cedure is  omitted. 

Oxidation  with  KMnO4.  The  solution  containing  the  vanadium  is  oxidized 
by  adding,  from  a  burette,  tenth  normal  potassium  permanganate  to  a  faint  per- 
manent pink.  If  the  solution  has  been  treated  with  H2S,  the  vanadium  is  in  the 
vanadyl  condition,  and  the  amount  of  permanganate  required  to  oxidize  the 
solution  completely  will  give  a  close  approximate  value  for  the  vanadium  present, 
each  cc.  of  N/10  KMn04  being  equivalent  to  0.0051  gram  vanadium. 

Reduction.  The  vanadite  is  now  reduced  to  vanadyl  salt  by  passing  through 
the  acid  solution,  containing  approximately  5%  free  sulphuric  acid,  a  steady  stream 
of  S02  gas.  Reduction  may  also  be  accomplished  by  adding  sodium  metabisul- 
phite,  or  sodium  sulphite,  to  the  acid  solution.  The  excess  S02  is  now  removed 
by  boiling  (a  current  of  C02  passed  into  the  hot  solution  will  assist  in  the  com- 
plete expulsion  of  the  S02). 

NOTE.    KMnO4  is  reduced  by  SO2. 

Test  for  Iron.  A  drop  test  with  potassium  ferricyanide,  K3Fe(CN)6,  on  a 
white  tile  will  give  a  blue  color  in  the  presence  of  ferrous  iron.  Since  ferrous 
iron  will  titrate  with  potassium  permanganate,  its  oxidation  is  necessary.  This 
is  accomplished  by  adding  tenth  normal  potassium  dichromate  solution  cau- 
tiously to  the  cold  liquid  until  no  blue  color  is  produced  by  the  spot  test  with 
K3Fe(CN)6  outside  indicator.  If  the  sample  is  sufficiently  dilute,  the  blue  color 
of  the  vanadyl  solution  will  not  interfere  in  getting  the  point  where  the  iron  is 
completely  oxidized.  Care  must  be  taken  not  to  pass  this  end-point,  otherwise 
Va204  will  also  be  oxidized  and  the  results  will  be  low. 

NOTE.  The  action  of  the  dichromate  is  selective  to  the  extent  that  iron  is  first 
oxidized  and  then  V2O4.  If  the  amount  of  iron  present  is  large  a  separation  must 
be  effected.  In  case  a  sodium  carbonate  potassium  nitrate  fusion  has  been  made  and 


470  VANADIUM 

vanadium  has  been  extracted  by  water,  iron  will  not  be  present.    A  special  procedure 
for  determination  of  vanadium  in  steel  is  given. 

Potassium  Permanganate  Titration.  N/10  KMn04  is  now  cautiously  added 
until  a  pink  color,  persisting  for  one  minute,  is  obtained.  During  the  titration 
the  solution  changes  from  a  blue  color  to  a  green,  then  a  yellow  and  finally  a  faint 
pink.  The  reaction  towards  the  end  is  apt  to  be  slow  if  made  in  a  cold  solution. 

NOTES.  In  absence  of  chromium,  it  is  better  to  make  the  titration  in  a  hot  solu- 
tion, 60  to  80°  C.,  the  end-point  being  improved  by  heat.  In  case  an  excess  of  per- 
manganate has  been  added,  the  excess  may  be  determined  by  a  back  titration  with 
tenth  normal  thiosulphate.  The  solution  may  be  rerun,  if  desired,  by  repeating  the 
reduction  with  SO2  and  the  titration  with  K2Cr2O7  and  KMnO4. 

One  cc.  N/10  KMn04  =  0.0051  gram  V,  or  =0.00912  gram  V2O5. 

For  solutions  containing  less  than  0.5%  vanadium  a  weaker  permanganate  reagent 
should  be  used.  A  fiftieth  normal  permanganate  solution  will  be  found  to  be  useful 
for  materials  low  in  vanadium. 

The  author  obtained  excellent  results  by  the  above  procedure  on  materials  con- 
taining small  amounts  of  iron  and  chromium;  with  amounts  equal  to  that  of  vanadium 
present  in  the  solution  no  interference  was  experienced.  The  titration  with  potassium 
permanganate  is  made  in  cold  solutions  if  chromium  is  present,  as  the  permanganate 
will  oxidize  chromium  in  hot  solutions.  Potassium  permanganate  added  to  samples 
containing  chromic  salts,  and  the  mixture  boiled,  will  oxidize  these  quantitatively  to 
chromates.  This  reaction  does  not  take  place  in  cold  solutions  to  any  appreciable 
extent  during  a  titration  and  only  slowly  in  warm  solutions. 


Volumetric  Determination  of  Vanadium  by  Reduction  with 

Zinc  to  V2O2 

The  procedure  proposed  by  Gooch  and  Edgar  is  to  reduce  vanadic  acid,  in 
presence  of  sulphuric  acid,  by  zinc  to  the  oxide,  V202;  oxidation  of  the  unstable 
V202  by  the  air  is  anticipated  by  means  of  ferric  chloride  or  sulphate,  in  the 
receiver  of  the  Jones  reductor,  the  highest  degree  of  reduction  being  registered 
by  the  ferrous  salt  formed  by  the  reaction  of  the  reduced  vanadate  on  the  ferric 
salt,  i.e.,  V202+3Fe203=6FeO+V206.  Compounds  reduced  by  zinc  and  oxi- 
dized by  KMn04  must  be  absent  or  allowed  for. 

Procedure.  The  Jones  reductor  is  set  up  as  directed  in  the  procedure  for  the 
determination  of  iron  by  zinc  reduction.  The  receiver  attached  to  the  tube  con- 
taining the  column  of  zinc  is  charged  with  a  solution  of  ferric  alum  in  considerable 
excess  of  that  required  for  the  oxidation  of  the  reduced  vanadium.  (The  amal- 
gamated zinc  is  cleaned  by  passing  through  the  column,  a  dilute  solution  of  warm 
sulphuric  acid.  The  final  acid  washings  should  show  no  further  reducing  action 
on  permanganate  when  the  reductor  is  clean.)1  Gentle  suction  is  applied,  and 
through  the  column  of  clean  amalgamated  zinc  are  passed  in  succession — 100  cc. 
of  hot  water,  100  cc.  of  2.5%  sulphuric  acid,  and  then  the  solution  of  vanadic 
acid  diluted  to  25  cc.  in  a  2.5%  sulphuric  acid  solution,  and  finally  100  cc.  of  hot 

1  Corrections  should  be  made  for  the  action  of  zinc  upon  the  reagents  without 
the  vanadic  acids,  as  it  is  almost  impossible  to  get  a  condition  where  no  blank  is 
obtained  with  permanganate.  The  reductor  is  cleaned  first  by  passing  about  500  cc. 
of  dilute  2.5%  sulphuric  acid  through  the  column  of  zinc.  A  blank  is  now  obtained 
with  the  same  quantity  of  reagents  as  is  used  in  the  regular  determination,  only 
omitting  the  vanadium,  and  this  is  deducted  from  the  titration  obtained  for  each 
sample  reduced. 


VANADIUM  471 

water.    To  the  receiver  is  added  a  volume  of  4  cc.  of  syrupy  phosphoric  acid  to 
decolorize  the  solution.    The  reduced  iron  salt  is  now  titrated  with  N/10  KMn04. 

One  cc.  N/10  KMn04  =0.0017  gram  V,  or    =0.00304  gram  V205. 

Determination  of  Vanadium  in  Steel 

The  following  method  is  used  in  analyzing  the  Bureau's  vanadium  and  chrome- 
vanadium  steels.  The  procedure  was  worked  out  by  J.  R.  Cain  and  L.  F.  Witmer 
of  the  U.  S.  Bureau  of  Standards. 

Five  to  10  grams  of  drillings  are  dissolved  in  hydrochloric  acid  (1  : 1),  a  few 
drops  of  hydrofluoric  are  added,  and  the  solution  is  boiled  for  a  few  minutes.  The 
insoluble  matter  is  filtered  off,  ignited,  fused  with  a  little  sodium  carbonate,  the 
fusion  dissolved  in  water  and  added  to  the  main  filtrate.  This  is  then  oxidized 
with  the  minimum  amount  of  nitric  acid  needed,  and  boiled  till  free  from  fumes. 
The  iron  is  extracted  with  ether  and  the  excess  of  ether  removed  from  the  aqueous 
layer  by  evaporation  on  the  steam  bath.  After  concentration  on  the  bath,  strong 
nitric  acid  is  added  to  the  solution  and  it  is  evaporated  to  dryness.  The  residue 
is  dissolved  in  strong  nitric  acid,  the  solution  is  diluted  with  water  and  nearly 
neutralized  with  strong  sodium  hydroxide  solution.  It  is  then  poured  slowly 
into  150  to  200  cc.  of  a  10%  sodium  hydroxide  solution,  stirring  vigorously.  The 
solution  is  filtered,  and  the  series  of  operations  are  repeated  with  the  precipitate 
until  it  is  free  from  vanadium,  as  shown  by  dissolving  it  in  nitric  acid  and  testing 
with  hydrogen  peroxide.  In  the  latter  treatments  the  amount  of  sodium  hydrox- 
ide solution  used  may  be  smaller.  From  the  combined  filtrates  the  vanadium  is 
precipitated  with  mercurous  nitrate  solution,  after  making  nearly  but  not  quite 
neutral  with  dilute  nitric  acid.  After  settling,  the  precipitate  is  collected  on  paper 
and  washed  with  dilute  mercurous  nitrate  solution.  The  filter  is  burned  off  in 
a  platinum  crucible  and  the  precipitate  ignited  till  all  the  mercury  is  expelled. 
The  impure  vanadium  pentoxide  left  is  fused  with  a  little  sodium  carbonate,  the 
fusion  is  dissolved  in  water  and  filtered  (on  asbestos)  from  insoluble  matter.  A 
second  precipitation  with  mercurous  nitrate  is  then  made.  Sometimes  a  further 
fusion  and  precipitation  may  be  necessary  in  order  to  get  a  product  sufficiently 
pure  for  the  next  step,  which  is  a  final  fusion  with  sodium  carbonate.  The  fusion 
is  dissolved  in  dilute  sulphuric  acid  and  the  vanadium  is  reduced  by  sulphur 
dioxide  gas  and  titrated  against  N/50  permanganate  after  complete  expulsion  of 
the  excess  of  reducing  agent. 

Volumetric  Determination   of   Molybdenum   and   Vanadium   in 
Presence  of  One  Another 

Sulphur  dioxide  reduces  V206  to  V204,  but  does  not  reduce  molybdic  acid 
provided  the  sample  contains  1  cc.  of  free  sulphuric  acid  per  50  cc.  of  solution  and 
not  more  than  0.2  gram  of  molybdic  acid.  By  means  of  amalgamated  zinc  V205 
is  reduced  to  V202  and  Mo03  to  Mo203.  Upon  these  two  reactions  the  deter- 
mination is  based  according  to  the  procedure  worked  out  by  Edgar.1  Details 
of  the  method  are  given  in  the  chapter  on  Molybdenum,  page  282. 

1  Graham,  Edgar,  Am.  Jour.  Sci.  (4),  25,  332.  Gooch,  "  Methods  in  Chemical 
Analysis,"  John  Wiley  &  Sons. 


472  VANADIUM 


Volumetric  Determination  of  Vanadium,  Arsenic  or  Antimony 
in  Presence  of  One  Another.     Edgar's  Method  l 

Tartaric  or  oxalic  acid  reduces  V205  to  V204,  but  does  not  act  upon  arsenic 
or  antimony.  On  the  other  hand  S02  causes  the  reduction  of  all  three.  There- 
fore if  aliquot  portions  of  the  solution  are  taken,  one  portion  being  treated  with 
tartaric  acid  and  vanadium  determined  by  titration  with  iodine,  and  another 
portion  reduced  with  S02  and  again  titrated  with  iodine,  the  difference  between 
the  two  tit  rations  is  due  to  the  cc.  of  reagent  required  for  the  oxidation  of  the 
reduced  arsenic  or  antimony.2 

Reactions.    V204+I2+H20  =V205+2HI. 

As203+V204+3I2+3H20=As206+V205+6HI. 
Sb20«+V204+3I2+3H20=Sb205+V205+6HI. 

Vanadium.  One  portion  is  boiled  with  about  2  grams  of  tartaric  or  oxalic 
acid,  until  the  solution  turns  the  characteristic  blue  of  vanadium  tetroxide.  After 
cooling,  the  solution  is  nearly  neutralized  with  potassium  bicarbonate,  and  an 
excess  of  standard  iodine  solution  added.  Neutralization  is  now  completed, 
an  excess  of  bicarbonate  added,  and  after  fifteen  to  thirty  minutes  the  excess 
iodine  titrated  with  standard  arsenious  acid,  starch  being  used  as  an  indicator. 
This  titration  measures  the  vanadium  present. 

Arsenic  or  Antimony.  A  second  portion  of  the  solution  is  placed  in  a  pres- 
sure flask  and  acidified  with  sulphuric  acid.  A  strong  solution  of  sulphurous  acid 
is  added,  the  flask  closed  and  heated  for  an  hour  on  the  steam  bath.  After  cooling, 
the  flask  is  opened  and  the  solution  transferred  to  an  Erlenmeyer  flask  and  the 
excess  of  S02  removed  by  boiling,  a  current  of  C02  being  passed  through  the  liquid. 
The  cooled  solution  is  treated  with  bicarbonate,  iodine  added  and  the  titration 
conducted  exactly  as  described  for  determination  of  vanadium  in  the  first  por- 
tion. The  difference  between  the  first  titration  and  the  second  is  a  measure  of 
the  cc.  required  for  oxidation  of  arsenic  or  antimony. 


Determination  of  Vanadium  and  Iron  in  Presence  of  Each  Other 

The  solution  slightly  acidified  with  sulphuric  acid  is  treated  with  sulphurous 
acid,  the  excess  expelled  and  the  reduced  vanadium  and  iron  titrated  with  stand- 
ard potassium  permanganate.4 

10FeO-f-5V204-f6H2S04+4KMn04=5Fe203+5V206+2K2S04+4MnS04+6H,0. 

The  solution  is  now  reduced  with  zinc  in  the  Jones  reductor  and  again  titrated 
with  permanganate.2  V206  is  reduced  by  zinc  to  V202,  the  sample  being  caught 

1 G.  Edgar,  Am.  Jour.  Sci.  (4),  27,  299. 

'Gooch,  "  Methods  of  Chemical  Analysis." 

•Graham,  Edgar,  Am.  Jour.  Sci.,  (4),  26,  79. 

See  Am.  Jour.  Sci.,  (4),  27,  174,  also  Gooch,  "  Methods  in  Chemical  Analysis,"  p.  510, 
for  procedure  determining  iron,  chromium  and  vanadium,  in  presence  of  one  another. 

4  When  the  color  has  changed  from  a  bluish-green  to  greenish-yellow  the  solution 
is  heated  to  70  to  80°  C.,  and  the  permanganate  titration  completed  in  a  hot  solution. 


VANADIUM 


473 


in  ferric  alum  solution  (details  for  determining  of  vanadium  by  reduction  with 
zinc  are  given  under  the  volumetric  methods  for  this  element) . 

10FeOH-5V202+12H2S04+8KMn04=5Fe203-r-5V205+4K2S04+8MnS04+12H20. 

The  difference  between  the  two  titrations  multiplied  by  0.00456  =vanadic 
acid  (V205)  originally  present. 


lodometric  Method  for  Estimation  of  Chromic  and  Vanadic  Acids 
in  Presence  of  One  Another 

The  following  procedure  developed  by  Edgar,1  is  given  by  Gooch  ("  Methods 
of  Chemical  Analysis  "). 

In  carrying  out  the  operation,  the  alkali  salts  of  the  chromic  and  vanadic  acid 
are  put  into  the  Voit  flask  of  the  distillation  apparatus  shown  in  the  cut,  Fig.  71. 

One  or  2  grams  of  potassium  bromide  are  added,  the  flask  is  connected  with 
the  absorption  apparatus  contain- 
ing a  solution  of  potassium  iodide 
made  alkaline  with  sodium  car- 
bonate or  sodium  hydroxide,  and 
the  whole  apparatus  is  filled  with 
hydrogen  gas.  Fifteen  to  20  cc. 
of  concentrated  hydrochloric  acid 
are  added  through  the  separatory 
funnel  and  the  solution  is  boiled 
for  ten  minutes,  an  interval  of 
time  found  to  be  enough  for  the 
completion  of  the  reduction.  A 
slow  current  of  hydrogen  is  main- 
tained to  avoid  back  suction  of 
the  liquid  from  the  Drexel  bottle. 
The  apparatus  is  disconnected, 
the  Voit  flask  placed  in  a  beaker 

containing  cold  water,  and  the  FIG.  71. 

alkaline  solution  in  the  absorption 

apparatus  cooled  by  running  water.  The  contents  of  the  trap  are  washed  into 
the  Drexel  bottle  and  the  solution  therein  is  made  slightly  acid  with  hydro- 
chloric acid.  The  liberated  iodine  is  titrated  with  approximately  N/10  sodium 
thiosulphate  and  the  color  is  brought  back  by  a  drop  or  two  of  N/10  iodine  solu- 
tion, after  the  addition  of  starch. 

Alkaline  potassium  iodide  is  again  placed  in  the  absorption  apparatus  and  the 
latter  connected  with  the  Voit  flask.  The  current  of  hydrogen  is  turned  on  and, 
after  the  air  has  been  expelled,  the  apparatus  is  disconnected  momentarily,  1  or 
2  grams  of  potassium  iodide  are  added  to  the  solution  in  the  Voit  flask,  and  con- 
nections made  again.  Through  the  separatory  funnel  10  cc.  to  15  cc.  of  con- 
centrated hydrochloric  acid  and  3  cc.  of  syrupy  phosphoric  acid  are  added  and 
the  solution  in  the  reduction  flask  is  boiled  to  a  volume  of  10  cc.  to  12  cc.  The 
absorption  apparatus  is  removed  and  cooled,  hydrochloric  acid  is  added  and  the 
liberated  iodine  titrated  with  approximately  N/10  sodium  thiosulphate. 

1  Graham  Edgar,  Am.  Jour.  Sci.  (4),  26,  333. 


474  VANADIUM 

The  iodine  determined  in  the  first  titration  corresponds  to  a  reduction  of  the 
chromic  and  vanadic  acids  according  to  the  equation 

V205+2Cr03+8HBr=V204+Cr203+4Br2+4H20, 

while  in  the  second  case  the  iodine  corresponds  to  a  reduction  of  the  vanadium 
tetroxide  to  trioxide  as  indicated  in  the  equation 

V204+2HI  =  V203+I2+H20. 

The  second  titration,  therefore,  determines  the  vanadic  acid  present,  and  the 
difference  between  the  first  and  second  furnishes  the  necessary  data  for  the  cal- 
culation of  the  chromium. 

DETERMINATION  OF  VANADIUM  IN  FERRO= VANADIUM 

Standard  Methods  of  the  American  Vanadium  Company1 

Dissolve  0.510  gram  of  the  alloy  (100  mesh)  in  a  250-cc.  beaker  with  50  cc.  dilute 
sulphuric  acid  (1  :  2)  and  10  cc.  (concentrated)  nitric  acid.  If  the  alloy  does  not 
decompose,  when  heated,  add  a  few  cc.  of  hydrofluoric  acid.  Take  down  to  copious 
white  fumes.  ^  Cool,  add  50  cc.  dilute  sulphuric  acid  (1  :  2)  and  water.  Heat  until 
all  salts  are  in  solution  and  transfer  to  a  white  casserole  containing  100  cc.  dilute 
sulphuric  acid  (1  :  2).  Dilute  the  solution  to  400  cc.  with  H2O  and  heat  to  60°  C. 
The  solution  is  ready  to  titrate. 

Add  potassium  permanganate  until  a  deep  red  is  obtained.  Just  discharge  the 
red  color  with  ferrous  ammonium  sulphate. 

Get  the  neutral  point  by  alternating  the  permanganate  and  ferrous  ammonium 
sulphate  until  one  drop  of  the  ferrous  sulphate  just  discharges  the  pink  color. 

Now  add  N/10  ferrous  ammonium  sulphate  from  a  burette  until  the  vanadium 
is  reduced  and  then  3  cc.  in  excess. 

Titrate  the  excess  of  ferrous  ammonium  sulphate  with  N/10  potassium  bichro- 
mate, using  potassium  ferricyanide  as  an  indicator. 

From  the  cc.  of  ferrous  ammonium  sulphate  used,  subtract  the  cc.  of  bichromate 
used.  The  number  of  cc.  used  gives  the  per  cent  of  vanadium  in  the  alloy. 

The  relation  between  ferrous  ammonium  sulphate  and  bichromate  is  established 
by  adding  150  cc.  sulphuric  acid  (1  :  2)  to  a  casserole,  diluting  to  400  cc. 

Find  the  neutral  point  and  then  add  25  cc.  ferrous  ammonium  sulphate  and  titrate 
with  bichromate  until  the  blue  spot  is  just  discharged. 

Blank.  EXAMPLE 

Ferrous  ammonium  sulphate  used 25      cc. 

Potassium  bichromate  used 24 . 6  " 

25.00 

24.60 

.40  -i-25  =-0.016  factor. 
Alloy. 

Ferrous  ammonium  sulphate  used 40 . 00 

Potassium  bichromate  used 2 . 40 

40  cc.  X  —0.016 =      .  64  cc. 

40.00-0.64 =39.36  " 

Correction  on  ferrous  ammonium  sulphate : 

39.36-2.4  =36.96%  V. 

Solutions  used: 

N/10  potassium  bichromate. 

N/10  ferrous  ammonium  sulphate. 

Potassium  ferricyanide,  a  crystal  the  size  of  a  pea  in  50  cc.  of  water. 
Potassium  permanganate,  5  grains  per  liter. 

1  Methods  developed  in  the  Bridgeville  Laboratory.  By  courtesy  of  the  American 
Vanadium  Company. 


VANADIUM  475 


Determination  of  Vanadium  in  Vanadium  Ores 

Weigh  0.51  gram  of  the  finely  powdered  ore  in  a  H-in.  diameter  iron  crucible 
filled  three-fourths  full  of  sodium  peroxide.  Fuse.  Dissolve  the  fusion  in  water  and 
add  100  cc.  H2SO4  (1  :  2)  in  excess  and  evaporate  until  white  fumes  come  off.  Cool 
and  dilute  and  filter.  Gas  the  filtrate,  which  should  be  about  400  cc.,  until  all  H2S 
metals  are  precipitated.  Boil  and  filter.  Boil  the  filtrate  until  all  H2S  is  off.  Trans- 
fer to  a  500-cc.  casserole  and  add  50  cc.  H2SO4  (1  :  2)  and  heat  to  above  60°  C.  Ti- 
trate as  in  the  determination  of  vanadium  in  ferro-vanadium. 

Determination  of  Vanadium  in  Steel 

Dissolve  5.1  grams  of  steel  in  a  covered  400-cc.  beaker  with  60  cc.  of  HC1  (con- 
centrated). After  total  solution  add  concentrated  HNO3  sufficient  for  complete 
oxidation.  Evaporate  to  a  syrupy  consistency,  add  40  cc.  HC1  (concentrated)  and 
evaporate  to  about  20  cc.  Cool  and  transfer  contents  to  a  separatory  funnel,  wash- 
ing beaker  with  dilute  HC1  (2HC1  :  1  H2O). 

Add  100  cc.  ether,  cork  and  shake  for  some  time,  cooling  funnel  under  tap  water 
while  shaking.  Remove  cork,  place  funnel  in  stand  and  allow  it  to  stand  for  at  least 
five  minutes.  Run  out  the  lower  layer  of  the  separation  into  the  original  400-cc. 
beaker. 

Evaporate  the  ether  off.     Cool  and  oxidize  with  a  few  crystals  of  sodium  chlorate. 

Boil  off  the  chlorine.  Add  50  cc.  of  1  :  2  H2SC>4  and  evaporate  to  copious  white 
fumes.  Cool,  oxidize  completely  with  KMnO4  (5  grams  to  the  liter),  add  40  cc.  of 
HC1  (concentrated)  and  evaporate  to  dense  white  fumes.  Cool,  add  40  cc.  of  water, 
and  again  take  down  for  the  last  time  to  white  fumes.  Cool,  add  150  cc.  of  water, 
cool,  and  titrate  with  N/50  potassium  permanganate.  Each  cc.  of  permanganate 
used  is  equal  to  0.00102  gram  of  vanadium,  or  in  this  case,  having  used  a  10-factor 
weight,  each  cc.  represents  0.02%  vanadium. 

Determination  of  Vanadium  in  Steel  (When  Chromium  is  present) 

Dissolve  5.1  grams  of  steel  in  a  covered  400-cc.  beaker  with  60  cc.  of  HC1  (con- 
centrated). After  total  solution,  add  concentrated  HNO3  sufficient  for  complete 
oxidation.  Evaporate  to  a  syrupy  consistency,  add  40  cc.  HC1  (concentrated)  and 
evaporate  to  about  20  cc.  Cool  and  transfer  contents  to  a  separatory  funnel,  washing 
with  dilute  HC1  (2  HC1  :  1  H2O).  Add  100  cc.  ether,  cork  and  shake  for  some  time, 
cooling  funnel  under  tap  water  while  shaking.  Remove  cork,  place  funnel  in  stand 
and  allow  it  to  stand  for  at  least  five  minutes.  Run  out  the  lower  layer  of  the  sepa- 
ration into  the  original  400-cc.  beaker. 

Evaporate  the  ether  off.  Add  5  cc.  HNO3  (concentrated)  and  just  bring  to  a  boil, 
Stir  out  all  nitrous  fumes,  make  alkaline  with  NaOH  (saturated  solution).  Make 
just  acid  with  HNO3  (concentrated)  cool  solution.  . 

Add  above  solution  to  a  solution  containing  300  cc.  cold  water  and  5  cc.  of  NaOH 
(saturated  solution).  Boil  and  filter,  washing  with  hot  water  thoroughly.  Make 
nitrate  just  acid  with  HNO3  (concentrated).  Add  40  cc.  of  a  saturated  solution  of 
lead  acetate.  (If  lead  precipitate  forms  just  clear  solution  by  adding  HNO;J  drop  by 
drop  and  bring  to  a  boil.)  Add  60  cc.  of  ammonium  acetate.  Boil  for  twenty  minutes. 
The  vanadium  is  precipitated  as  lead  vanadate. 

Filter  the  lead  vanadate  onto  a  Munktell  paper,  washing  with  hot  water.  Put 
filter  containing  lead  vanadate  in  a  small  porcelain  dish  and  burn  off  paper  at  a  low 
heat.  Add  a  little  HNO3  and  evaporate  on  the  hot  plate,  then  put  the  dish  in  the 
cold  end  of  a  muffle  to  drive  off  the  remaining  HNO3.  Avoid  baking.  Dissolve 
in  HC1  (concentrated)  and  transfer  the  solution  to  a  400-cc.  beaker.  Add  60  cc. 
dilute  H2SO4  (1  :  2).  Oxidize  thoroughly  with  KMnO4  (5  grams  to  a  liter.)  Add 
40  cc.  HC1  (concentrated)  and  evaporate  to  dense  white  fumes.  Cool,  add  40  cc. 
of  water  and  again  take  to  white  fumes.  Cool,  add  150  cc.  of  water,  cool,  and  titrate 
with  N/50  KMnO  .  Each  cc.  of  permanganate  used  is  equal  to  0.00102  gram  of 
vanadium,  or  in  this  case,  having  used  a  ten-factor  weight,  each  cc.  represents  0.02% 
vanadium. 


476  VANADIUM 


Determination  of  Vanadium  in  Cupro-vanadium,  Brasses  and  Bronzes 

Dissolve  1.020  grams  of  cupro- vanadium  in  aqua  regia.  Evaporate  to  small  bulk 
and  add  excess  of  peroxide  of  hydrogen.  Dilute  to  600  cc.  and  add  ammonia  until 
all  copper  goes  into  solution.  Heat  to  boiling  and  add  sufficient  barium  chloride 
solution  to  precipitate  all  the  vanadium.  Boil  and  filter.  Wash  all  copper  out  of 
filter  with  hot  ammonia  water.  Transfer  the  filter  to  a  beaker,  add  100  cc.  1  :  2  sul- 
phuric acid,  boil  and  filter  on  close  filter  paper.  Titrate  the  filtrate  with  N/10 
ferrous  ammonium  sulphate  and  N/10  potassium  bichromate  the  same  as  in  the  case 
of  the  ferro  alloy,  except  that  this  being  a  two-factor  weight,  the  result  must  be 
divided  by  2. 

Vanadium  copper,  brasses  and  bronzes  are  treated  in  the  same  manner  except  that 
a  ten-factor  weight  is  used  and  the  titration  carried  out  with  N/50  solution  instead 
of  N/10. 

The  author  wishes  to  acknowledge  his  indebtedness  to  "  Methods  in  Chemical 
Analysis  "  by  F.  A.  Gooch  for  information  on  volumetric  methods  of  determining 
vanadium. 


ZING 

F.    G.    BREYER.1 

Zn,  ttt.wt.  65.37;  sp.gr.  6.48  to  7.19;  m.p.  419°;  6.p.  920°]  ZnO  oxide. 

DETECTION 

The  finely  powdered  material,  when  heated  on  charcoal  in  the  reducing  flame 
of  a  blowpipe,  gives  an  incrustation,  yellow  when  hot — white  when  cold.  On 
moistening  with  cobalt  nitrate  solution  and  re-igniting,  the  mass  is  greenish-yellow. 
Materials  containing  above  5%  Zn  will  give  positive  tests.  With  experience, 
less  can  be  detected,  but  for  smaller  amounts  the  regular  procedure  as  given 
under  Titration  in  Acid  Solution,  Separating  Zn  as  ZnS,  should  be  followed, 
using  samples  as  follows:  For  material  containing  0.01-0.05%,  10  to  20  grams; 
0.05-0.10%,  5  to  10  grams;  0.10-0.5%,  5  grams;  0.5%  on  up,  2  grams  to  0.5 
gram,  depending  on  per  cent  of  zinc  present. 

In  case  the  material  is  of  interest,  only  if  it  carries  higher  than  several  per  cent 
of  zinc,  a  shorter  and  easier  wet  test  is  to  bring  the  material  into  solution  by 
means  of  hydrochloric  or  nitric  acid,  add  bromine  water  and  then  precipitate  iron, 
aluminum  and  manganese  with  ammonia,  as  given  under  heading  of  Deter- 
mination of  Zinc  in  Acid  Solution,  Separating  Iron,  Aluminum  and  Man- 
ganese with  Ammonia  and  Bromine,  filter,  wash  and  make  the  filtrate  acid  with 
hydrochloric  acid,  10  cc.  excess  added  for  each  100  cc.  of  solution,  and  potassium 
ferrocyanide  added.  Zinc,  if  present,  gives  the  characteristic  precipitate.  Copper 
interferes  and  if  present  must  be  separated  with  hydrogen  sulphide,  as  given 
under  heading  Procedure  for  Copper-bearing  Ores.  v 

In  case  manganese  and  copper  are  known  to  be  absent,  a  still  snorter  test  may 
be  used:  To  the  solution  of  the  zinciferous  material  add  2  or  3  grams  of  citric 
acid  per  200  cc.  solution,  then  make  ammoniacal,  add  ferrocyanide — a  white 
precipitate  indicates  zinc. 

ESTIMATION 

The  determination  of  zinc  is  called  for  in  the  buying  and  selling  of  ores  for 
smelters,  refuse  material,  e.g.,  from  galvanizing  plants,  foundries,  brass  mills, 
and  blast  furnaces,  in  manufacture  of  brass,  white  metals,  and  alloys  in  general, 
paints  and  pigments,  zinc  chloride  for  preservation  purposes,  and  in  the  control 
work  in  smelting  of  zinc  and  lead  ores. 

Preliminary.  The  method  to  be  followed  in  the  estimation  of  zinc  will 
depend  largely  on  the  nature  of  the  material  in  which  it  occurs,  the  quantity 
present,  and  the  experience  of  the  analyst.  Each  of  the  methods  outlined  will 
give  correct  results  only  on  the  materials  for  which  they  are  indicated,  there 
being  but  one  method  recommended  which  is  applicable  to  all  zinciferous  mate- 

lln  Charge  of  Testing  Department,  New  Jersey  Zinc  Company  (of  Pa.),  Palmerton, 
Pa. 

477 


478  ZINC 

rials.  It  cannot  be  emphasized  too  strongly  that  each  step  has  a  definite  pur- 
pose (which  may  not  be  at  once  apparent  to  the  analyst  making  only  an  occa- 
sional zinc  determination),  and  no  part  of  the  procedure  should  be  varied  or 
omitted,  excepting  after  abundant  experience. 

Preparation  of  Sample 

The  representative  sample  should  be  ground  to  pass  a  100-mesh  screen  or 
finer.  If  the  material  contains  shot  metal,  it  should  be  screened  out  and  the 
percentage  present  calculated.  It  is  then  treated  as  given  under  heading  Material 
Containing  Metallics,  page  482. 

Moisture  Determination  in  the  Pulp 

One  of  the  commonest  causes  of  differences  in  zinc  ore  analysis  is  the  failure 
to  take  moisture  determinations  on  the  pulp  sample. 

In  order  that  analyses  made  on  the  same  pulp  at  different  times  and  in  different 
laboratories  may  be  compared  it  is  absolutely  necessary  that  all  determinations  be 
corrected  to  a  dry  basis.  It  is  not  sufficient  that  the  sample  be  dried  before  or 
after  having  been  pulped,  but  a  sample  for  moisture  must  be  weighed  out  at  the 
same  time  as  the  sample  for  analysis,  and  the  analytical  result  corrected  for  the 
per  cent  of  moisture  found  at  the  time  of  weighing.  This  is  especially  true  on 
roasted  zinc  ores  which  contain  sulphates  of  zinc,  iron  and  lime  and  which  take  up 
moisture  quite  rapidly  under  ordinary  atmospheric  conditions. 

The  usual  temperature  for  drying  should  be  110°  C.,  but  on  special  ores,  e.g., 
those  containing  sulphates,  it  is  necessary  to  dry  at  250°  C.  unless  it  is  first  shown 
that  there  is  no  loss  of  water  above  110°  C. 

The  determination  is  best  made  by  weighing  approximately  two  grams  in  a 
small  glass-stoppered  weighing  tube  and  drying  to  constant  weight,  the  weighing 
tube  being  closed  with  the  glass  stopper  as  soon  as  the  tube  is  taken  from  the 
drying  oven. 

SEPARATIONS 

Silica.  Evaporate  with  hydrochloric  acid  or  take  to  fumes  of  sulphuric 
acid.  The  dehydration  with  sulphuric  acid  is  complete  and  gives  silica  that  is 
easily  filtered  and  washed. 

Cadmium,  Lead,  Arsenic,  Antimony,  Bismuth  and  Copper.  Aluminum 
may  be  used  to  separate  all  the  metals,  except  cadmium,  the  latter  being  only 
partially  separated.  The  procedure  is  as  given  in  the  standard  method. 

The  sepa.ration  may  also  be  made  as  follows:  Evaporate  the  solution  of  the 
zinciferous  material  to  fumes  with  7  cc.  of  1  :  2  sulphuric  acid.  Cool,  take  up  in 
about  50  cc.  of  water  and  warm,  add  10  cc.  of  10%  sodium  thiosulphate,  boil 
until  evolution  of  sulphur  dioxide  ceases,  then  filter.  Cadmium  if  present  is  not 
precipitated.  It  should  be  separated  by  the  procedure  given  under  Titration  in 
Acid  Solution  Separating  Zinc  as  Sulphide. 

Iron,  Aluminum  and  Manganese.  This  separation  may  be  effected  by 
precipitation  with  ammonia  and  bromine,  providing  the  quantities  present  are 
small.  When  large- amounts  are  present  the  basic  acetate  procedure  is  followed, 
or,  better,  the  zinc  separated  as  sulphide  in  dilute  sulphuric  acid  solution,  page  485. 


[ZINC  479 

Nickel  and  Cobalt.  When  nickel  or  cobalt  are  present,  the  only  safe  pro- 
cedure is  to  separate  the  zinc  as  zinc  sulphide  in  dilute  sulphuric  acid  solution, 
as  described  under  the  standard  method.  Weiss  has  shown  conclusively  that 
zinc  can  be  precipitated  free  from  either  cobalt  or  nickel  under  the  conditions 
there  outlined. 

METHODS  OF  ANALYSIS 

I.  Gravimetric  methods. 
II.  Electrolytic  methods. 
III.  Titration  with  standard  solution  of  K4Fe(CN)6. 

(a)  In  acid  solution. 

(b)  In  alkaline  solution. 

(c)  In  acid  solution,  separating  Zn  as  ZnS.     (Standard  method.) 

GRAVIMETRIC  METHODS 

Weighing  as  Zinc  Oxide 

In  this  case  the  procedure  is  the  same  as  in  the  volumetric  method,  in  which 
zinc  is  separated  as  zinc  sulphide  up  to  point  where  the  zinc  sulphide  is  filtered 
off  and  washed.  It  is  now  ignited  in  a  weighed  crucible  and  heated  to  800  to 
900°  C.  in  a  muffle  for  one  hour  and  weighed  as  ZnO.  Factor  ZnO  xO.8034  =  Zn. 

The  precipitate  of  zinc  sulphide  may  also  be  filtered  on  a  Gooch  crucible, 
and  ignited  as  above. 

Weighing  as  Sulphate 

The  zinc  sulphide  is  dissolved  in  hydrochloric  acid.  Sulphuric  acid  is  added 
and  the  solution  evaporated  in  a  weighed  crucible,  all  excess  acid  fumed  off  and 
the  resulting  zinc  sulphate  finally  ignited  at  a  dull  red  heat  and  weighed. 
ZnS04X  0.405  =  Zn. 

Electrolytic  Methods 

The  determination  is  best  made  from  an  alkaline  electrolyte  or  one  slightly 
acid  with  acetic  acid  and  containing  a  considerable  amount  of  sodium  acetate. 
The  alkaline  electrolyte  tends  to  give  high  results,  due  to  the  presence  of  zinc 
oxide  or  hydroxide  in  the  deposit.  The  best  results  are  obtained  with  a  solu- 
tion weakly  acid  with  one  of  the  weaker  organic  acids.  The  procedure  for  the 
acetate  electrolyte  is  as  follows: 

The  zinc  is  separated  from  other  elements  by  precipitating  with  hydrogen 
sulphide  in  dilute  sulphuric  acid  solution,  as  given  under  the  standard  method. 
The  precipitate  is  filtered  and  washed,  dissolved  in  hot  hydrochloric  acid — 
5  cc.  1  :  1  sulphuric  acid  added  and  the  whole  evaporated  to  fumes  to  expel  hydro- 
chloric acid.  Cool  and  dilute,  neutralize  with  sodium  hydrate  solution,  make 
slightly  alkaline,  then  acidify  with  acetic  acid,  and  add  about  5  grams  of  sodium 
acetate.  The  volume  of  solution  should  now  be  about  100  to  125  cc.  Elec- 
trolyze  with  a  platinum  gauze  electrode  with  0.5  ampere  at  5  volts. 

The  electrolytic  methods,  on  account  of  the  special  apparatus  needed,  the 
experience  and  care  necessary  to  get  reliable  results,  and  the  unavoidable  errors 
involved  in  their  use,  are  less  desirable  than  the  gravimetric  oxide  method  and 
still  less  desirable  than  the  ferrocyanide  method. 


480  ZINC 


VOLUMETRIC  METHODS 

Titration   in   Acid   Solution,   Separating   Iron,   Aluminum,   and 
Manganese  with  Ammonia  and  Bromine 

General.  This  method  is  especially  adapted  to  material  low  in  silica,  alumina, 
iron,  and  manganese.  When  the  operator  gains  experience  in  manipulation,  it  is, 
possible  to  obtain  good  results  on  samples  higher  in  these  elements,  but  its  hap- 
hazard use  with  materials  high  in  these  impurities  is  one  of  the  chief  causes  of  the 
common  inaccuracy  of  zinc  work.  If  copper  or  cadmium  are  present  in  quanti- 
ties, the  titration  in  acid  solution,  separating  Zn  as  ZnS,  is  to  be  preferred  for 
accurate  work. 

Procedure  for  Ores.  One-half  or  1  gram  (depending  on  the  per  cent  of  zinc 
present)  is  weighed  in  a  250-cc.  beaker.  Fifteen  cc.  of  hydrochloric  *  acid  (sp.gr. 
1.2)  are  added,  a  cover-glass  put  on,  and  the  ore  agitated  to  prevent  caking.  Boil 
down  to  a  volume  of  about  5  cc.2  cool,  wash  down  cover-glass  and  sides  of  beaker 
with  a  jet  of  water.  Add  10  cc.  of  saturated  bromine  water,  5  grams  of  ammonium 
chloride  and  15  cc.  of  ammonia  water  (sp.gr.  0.90)  and  boil  vigorously  for  a 
minute  or  two.  Filter  off  the  precipitated  hydroxides,  and  wash  four  times  with 
hot  water,  containing  50  grams  ammonium  chloride  and  25  cc.  ammonia  per 
liter.  The  precipitate  is  now  washed  from  the  filter  into  the  beaker  in  which 
the  original  precipitation  was  made,  and  the  precipitate  dissolved  in  strong 
hydrochloric  acid.  Ten  cc.  of  ammonia  (sp.gr.  0.9)  are  added,  the  solution 
boiled,  filtered  and  washed  as  before,  the  filtrate  being  combined  with  the  first 
filtrate.3  The  solution  is  then  diluted  to  250  cc.,  heated  to  boiling,  and  4  drops  of 
ammonium  sulphide  solution  added  to  destroy  oxidizing  agents  4  and  pre- 
cipitate small  amounts  of  copper  and  cadmium.  The  solution  is  neutralized 
with  hydrochloric  acid,  the  resolution  of  the  precipitated  zinc  sulphide  serving 
in  lieu  of  an  indicator.  Ten  cc.  excess  of  concentrated  hydrochloric  acid  are 
added  6  and  the  solution  titrated,  not  below  75°  C..  with  standard  ferrocyanide, 
using  uranium  nitrate  (10%  solution)6  as  an  external  indicator. 

Standardization  of  the  Ferrocyanide  Solution 

The  potassium  ferrocyanide  is  standardized  by  weighing  out  portions  of  C.P. 
zinc  that  will  give  a  titration  of  approximately  the  same  number  of  cc.  as  the 
sample.  Dissolve  in  15  to  20  cc.  of  hydrochloric  acid  and  dilute  to  about  225  cc. 

1  Nitric  acid  should  be  added  in  case  of  sulphide  ores. 

a  In  case  of  siliceous  ore,  it  is  advisable  to  evaporate  to  dryness,  and  on  unknown 
material  to  evaporate  slowly,  in  order  to  make  sure  of  complete  solution  of  the  zinc. 
Certain  siliceous  and  oxide  ores  are  difficultly  soluble  in  hydrochloric  acid,  and  fre- 
quently cause  low  results,  where  rapid  decomposition  is  the  routine. 

3  In  case  of  high  silica,  alumina,  iron,  and  manganese  materials,  three  precipitations 
are  necessary. 

4  It  is  necessary  to  destroy  all  oxidizing  agents,  as  they  will  react  with  the  ferro- 
cyanide. 

6  The  excess  of  hydrochloric  acid  should  be  carefully  measured.  A  burette  is  very 
useful  in  neutralizing  the  solution. 

•The  strength  of  the  uranium  nitrate  is  a  matter  of  personal  preference,  some 
using  a  saturated  solution.  On  the  other  hand  some  prefer  ammonium  molybdate. 
The  strength  of  solution  given  above,  however,  is  recommended  as  the  first  choice 
of  a  large  number  of  experienced  zinc  chemists. 


ZINC  481 

•  • 

Then  add  37  cc.  strong  ammonia,1  taking  care  to  avoid  spattering,  heat  to  boil- 
ing, add  4  drops  of  ammonium  sulphide,  neutralize  and  add  10  cc.  excess  hydro- 
chloric acid  and  titrate. 

General  Notes 

The  ferrocyanide  is  of  the  same  strength  as  is  used  in  titration  in  alkaline  solu- 
tion. See  below. 

The  precipitate  with  ammonia  carries  down  zinc.  This  is  especially  true  with 
siliceous  material  or  material  high  in  iron  and  alumina.  By  working  with  hot  aim- 
rnoniacal  ammonium  chloride  solution  and  making  two  or  three  precipitations,  the 
amount  held  can  usually  be  made  negligible. 

The  precautions  in  regard  to  adding  ferrocyanide  and  keeping  conditions  of  stand- 
ardization and  titration  the  same,  hold  here  as  in  all  ferrocyanide  tit  rations. 


Titration  in  Alkaline  Solution 

General.  This  procedure  is  designed  for  rapid  routine  work  on  roasted  or 
oxidized  ores,  especially  those  high  in  silica,  alumina,  iron,  and  manganese.  It 
should  only  be  used  on  unroasted  sulphides,  copper,  or  high  cadmium-bearing 
ores,  when  the  operator  has  had  long  experience.  It  is  designed  to  give  the  zinc 
content  of  materials  soluble  in  hydrochloric  or  nitric  acid.  For  materials  con- 
taining insoluble  zinc,  the  titration  in  acid  solution,  in  which  zinc  is  separated 
as  sulphide,  is  preferred. 

Procedure  for  Common  Ores.  The  following  method  is  recommended: 
The  weight  of  ore  to  be  taken  will  depend  on  the  approximate  amount  of  zinc 
present.  For  material  above  50%,  take  1  gram;  from  10  to  50%,  2  grams; 
5  to  10%,  4  grams;  and  below  5%,  5  to  10  grams.  Weigh  the  sample  into  a  tall 
400-cc.  beaker,  cover  with  water  and  add  25  cc.  concentrated  hydrochloric  acid, 
rotating  the  beaker  to  prevent  caking.  In  case  sulphides  are  present,  nitric  acid 
also  should  be  added.  Place  on  a  hot  plate  or  steam  bath  and  evaporate  to  dryness. 2 
Now  add  50  cc.  concentrated  nitric  acid,  cover  with  a  watch  crystal  and  boil 
off  all  nitrous  fumes.  When  these  have  disappeared,  add  about  3  to  4  grams 
KC103  and  boil  until  chlorine  fumes  do  not  show.3  Cool,  wash  off  the  watch 
crystal  and  sides  of  the  beaker,  and  dilute  to  about  100  cc.  Wash  into  500  cc. 
graduated  flask,  make  up  to  the  mark  and  shake  well.  Filter  through  a  close 
24-cm.  qualitative  paper  and  without  waiting  for  the  whole  to  run  through, 
measure  out  250  cc.  of  the  clear  filtrate  4  into  a  600-cc.  beaker.  Add  ferric  nitrate 
solution,  if  necessary,  so  as  to  bring  the  iron  content  up  to  about  300  to  400  milli- 
grams, i.e.,  if  only  a  small  amount  is  present,  add  10  cc.;  if  10  to  15%  is  present, 
add  5  cc.,  and  proceed  exactly  as  under  Standardization. 

Procedure  for  Copper-Bearing  Ores.     Either  method  is  recommended: 

Separation  of  Copper  by  Aluminum.     The  sample  is  treated  as  usual  up  to 

1  The  amounts  of  acid  and  ammonia  used  throughout  should  be  carefully  measured, 
so  as  to  keep  the  amount  of  ammonium  salts  approximately  the  same.     This  is  very 
important  in  order  to  avoid  errors,  due  to  varying  blanks. 

2  The  temperature  of  the  hot  plate  should  not  be  over  120°  C.,  as  ZnCl2  is  appre- 
ciably volatile  at  higher  temperatures. 

3  Any  oxidizing  agent  such  as  chlorine  or  chlorine  oxides  acts  on  the  ferrocyanide. 

4  The  graduated  flasks  should  be  standardized  against  one  another,  i.e.,  the  500  cc. 
should  be  twice  the  volume  of  the  250  cc. 


482  ZINC 

the  point  where  manganese  has  been  separated  and  250  cc.  of  the  clear  filtrate 
measured  out.  Add  25  cc.  1  :  1  sulphuric  acid  and  evaporate  to  strong  fumes, 
cool,  dilute  to  100  cc.,  add  a  gram  or  two  of  20-mesh  zinc-free  aluminum.  Heat 
until  all  the  copper  separates,  filter,  wash  and  proceed  with  the  filtrate  as  in  the 
regular  method. 

Separation  of  Copper  by  Hydrogen  Sulphide.  After  separation  of  the  man- 
ganese with  chlorate,  sulphuric  acid  is  added  and  the  solution  taken  to  fumes, 
as  in  above.  Cool,  dilute  to  100  cc.,  and  add  sulphuric  acid  so  that  12%  is 
present.  Warm  slightly  and  pass  hydrogen  sulphide  through  the  solution.  Filter 
off  the  copper  sulphide,  wash,  boil  H2S  out  of  the  filtrate,  and  titrate  as  usual, 
after  adding  ferric  nitrate  and  citric  acid. 

Material  Containing  Cadmium.  If  the  material  contains  cadmium  in 
quantities  sufficient  to  warrant  separation  (0.15%  or  more),  it  is  best  to  use  the 
titration  in  acid  solution,  separating  zinc  as  sulphide. 

Material  Containing  Carbonaceous  Matter.  If  the  material  under  examina- 
tion contains  carbonaceous  matter,  coal,  etc.,  it  must  be  separated  by  taking  to 
dryness  with  hydrochloric  acid.  Take  up  in  acid  and  water,  filter  and  wash, 
and  evaporate  the  filtrate  to  dryness.  Take  up  in  nitric  acid  and  proceed  as  in 
the  regular  method. 

If  the  carbonaceous  material  is  not  removed,  the  manganese  does  not  sepa- 
rate cleanly,  due  to  the  reducing  action  of  carbonaceous  compounds. 

Procedure  for  Material  Containing  Metallics.  On  account  of  the  lack  of 
uniformity  in  the  case  of  metallic  zinciferous  material  containing  lead  and 
iron,  it  is  well  to  work  on  large  samples.  Five  or  10  grams  of  the  metallics 
reduced  to  as  fine  a  size  as  possible  are  weighed  out  and  dissolved  in  nitric 
acid.  The  nitrous  fumes  are  boiled  off  and  the  whole  made  up  to  500  cc.  or 
1000  cc.  Fifty  or  100  cc.  are  now  pipetted  off  into  a  600-cc.  beaker  and  the 
zinc  titrated  as  usual.  In  case  the  metallic  portion  contains  manganese, 
which  is  unusual,  it  can  be  separated  by  the  regular  procedure.  Copper 
is  separated  as  given  under  Copper-bearing  Ores.  Material  containing 
cadmium  should  be  analyzed  by  other  methods,  as  given  under  Standard  Pro- 
cedure. 

Solutions.  Potassium  Ferrocyanide.  34.8  grams  pure  salt  in  1000  cc. 
water.  One  cc.  =  approximately  0.010  Zn.  This  solution  should  be  allowed  to 
stand  about  four  weeks  before  using. 

Ferric  Nitrate.  One  part  salt  in  6  parts  water.  It  is  well  to  add  a  little 
nitric  acid  to  prevent  hydrolysis. 

Citric  Acid.  One  part  acid  in  3  parts  water.  One  hundred  cc.  of  nitric  acid 
should  be  added  to  each  liter  to  prevent  mould  growth. 

Standardization.  The  factor  for  the  standard  solution  varies  slightly, 
as  would  be  expected,  with  the  amount  of  ferrocyanide  used,  so  that  it  is  best 
to  have  at  least  three  sets  of  factors,  one  at  40  cc.,  one  at  20  cc.,  and  one  at 
10  cc. 

Weigh  out  into  600-cc.  beakers  at  least  three  portions  of  C.P.  zinc  (Kahl- 
baum's  or  Merck's  stick,  or  J.  T.  Baker,  or  Baker  &  Adamson  20  mesh),  for  each 
set  of  factors.  When  using  20-mesh  zinc  each  sample  should  be  examined 
under  a  low-power  glass,  for  foreign  matter  or  oxidized  particles.  Dissolve  the 
metal  in  about  15  cc.  nitric  acid,  first  covering  with  water.  Boil  off  the  nitrous 


ZINC  483 

fumes  and  dilute  to  250  cc.  with  distilled  water.  Add  10  cc.  of  ferric  nitrate  solu- 
tion, and  15  cc.  citric  acid  solution,  make  faintly  ammoniacal,  using  a  piece  of 
litmus  paper  as  indicator.  Then  add  a  measured  excess  of  ammonia,  as  follows : 
40  cc.  factor,  20  cc.  excess;  20  cc.  factor,  10  to  12  cc.  excess;  and  for  low  titra- 
tions  make  only  faintly  ammoniacal.  Heat  the  solution  to  a  full  boil,  and  titrate 
immediately  with  the  standard  ferrocyanide,  stirring  the  solution  thoroughly 
and  adding  ferrocyanide  not  too  rapidly.  The  titration  is  completed  when  a 
drop  of  solution  gives  a  bluish-green  coloration  with  a  drop  of  50%  acetic  acid 
on  a  spot  plate.  To  prevent  passing  the  end-point,  or  until  the  operator  is  expe- 
rienced, a  portion  (50  cc.)  of  the  solution  may  be  held  back  in  a  small  beaker, 
the  end-point  passed,  and  the  titration  completed  after  adding  the  part  in  the 
small  beaker. 

General  Notes 

A  standard  zinc  solution  may  be  used  in  case  the  end-point  is  passed.  However, 
this  is  not  to  be  recommended  as  a  usual  practice.  In  any  case  it  should  be  very 
dilute,  so  that  1  cc.  =0.001  gram  zinc. 

The  ferrocyanide  should  be  added  gradually  and  the  solution  stirred  constantly, 
to  prevent  occlusion  of  ferrocyanide  or  zinc  solution  by  the  heavy  precipitate. 

A  moisture  sample  should  be  weighed  at  the  same  time  as  the  sample  for  analysis. 

The  variation  of  factor  with  amount  of  zinc  titrated  is  more  marked  in  this  method 
than  in  the  titration  in  acid  solution.  Hence,  it  is  necessary  that  standards  be  run 
covering  the  whole  range  of  zincs  to  be  titrated.  It  will  be  found  that  the  factors 
from  30  to  50  cc.  are  almost  the  same  and  from  15  to  30  cc.  slightly  lower,  from  5  to 
15  cc.  still  lower. 

The  zinc  used  as  a  standard  should  be  carefully  examined  for  foreign  particles 
and  oxidized  zinc.  In  case  stick  zinc  is  used,  the  surface  should  be  scraped  clean 
before  cutting.  Merck's  and  Kahlbaum's  stick  zinc,  as  well  as  Baker  &  Adam  son's, 
Eimer  &  Amend's,  or  J.  T.  Baker's  powdered  zinc  answer  the  purpose  as  regards 
metallic  impurities.  It  is  desirable  to  check  the  factor  by  means  of  a  standard 
ore. 

The  standard  of  the  ferrocyanide  solution  should  be  frequently  checked,  at  least 
once  every  ten  days.  A  solution  of  such  a  strength  that  1  cc.  equals  10  milligrams  of 
zinc  has  in  glass  a  temperature  coefficient  sufficient  to  decrease  the  factor  0.135%  per 
5°  C.  rise  in  temperature,  so  care  should  be  taken  that  no  sharp  change  of  tem- 
perature occurs  between  standardization  and  titration. 

The  factors  in  alkaline  and  acid  solution  are  not  identical.  In  alkaline  solution 
the  precipitate  closely  approaches  the  normal  ferrocyanide,  while  in  acid  solution 
there  is  formed  a  double  ferrocyanide  of  zinc  and  potassium. 


Standard  Method 

Titration  in  Acid  Solution — Separating  of  Zinc  as  Sulphide 

General.  The  method  of  separating  zinc  as  sulphide  in  a  solution  slightly  acid 
with  sulphuric  acid  is  of  almost  universal  application,  and  can  be  used  on  any 
class  of  zinciferous  material  that  has  come  under  the  author's  observation.  The 
steps  fit  together,  so  that  copper  and  cadmium  are  easily  separated  and  any  zinc 
in  the  insoluble  state,  e.g.,  spinels,  etc.,  can  readily  be  looked  for.  The  method 
of  decomposing  (taking  to  fumes  of  sulphuric  acid)  tends  to  take  into  solution 
material  that  would  be  overlooked  in  the  rapid  decompositions  effected  in  the 
preceding  methods.  Moreover,  the  use  of  the  internal  indicator  gives  a  very 
sharp  end-point,  so  that  this  method  is  fully  as  accurate  as  any  gravimetric 
method.  The  method  is  more  tune  consuming  than  the  ones  already  given,  but 


484  ZINC 

it  is  not  designed  for  rapid  routine  work,  but  rather  as  a  standard  procedure 
that  will  give  absolutely  reliable  results  on  all  classes  of  material.  This  method 
is  also  recommended  for  routine  work  in  case  the  analyst  is  called  on  to  make 
only  occasional  zinc  analyses. 

Standardization  of  the  Ferrocyanide  Solution 

NOTE.  The  standardization  of  the  solution  is  given  first,  on  account  of  the 
method  of  titration. 

Weigh  into  tall  400-cc.  beakers  several  portions  of  C.P.  zinc,  using  about 
0.35  gram.  Cover  with  water  and  dissolve  in  10  cc.  hydrochloric  acid  (sp.gr. 
1.2).  Now  add  13  cc.  ammonia  (sp.gr.  0.9),  make  acid  with  hydrochloric  acid, 
and  add  3  cc.  excess.  Add  0.03  or  0.04  milligram  of  ferrous  iron  in  the  form  of 
a  ferrous  sulphate  solution  and  dilute  to  about  200  cc.  with  distilled  water.  Heat 
to  boiling  and  titrate  as  follows:  About  one-quarter  of  the  solution  is  reserved 
in  a  small  beaker  and  the  ferrocyanide  added  to  the  mam  solution  with  vigorous 
stirring.  The  solution  takes  on  a  blue  color,  which  changes  to  a  creamy  white 
when  an  excess  of  ferrocyanide  is  added.  Now  add  a  few  cc.  more  and  pour  in  the 
reserved  portion  of  zinc  solution,  excepting  about  5  or  10  cc.  Add  ferrocyanide 
until  the  end-point  is  reached  and  add  about  ^  cc.  more.  The  last  of  the  reserved 
zinc  solution  is  then  poured  into  the  main  beaker,  washing  out  the  small  beaker 
with  a  portion  of  the  main  solution,  and  the  ferrocyanide  added  drop  by  drop 
until  the  blue  color  fades  sharply  to  a  pea  green  with  one  drop  of  ferrocyanide.1 
This  is  the  end-point.  Repeat  until  satisfactory  standards  are  obtained. 

Procedure.  Weigh  into  a  tall  150-cc.  beaker  an  amount  of  sample  so  that 
it  gives  a  titration  of  about  40  cc.,  i.e.,  5  grams  for  a  10%  ore  to  f  gram  for  60% 
ore  and  over.  Moisten  with  water  and  add  10  cc.  of  hydrochloric  acid  (sp.gr. 
1.20),  cover  with  a  watch-glass.  In  case  of  sulphides  it  is  necessary  to  add 
nitric  acid.  Boil  moderately  on  a  hot  plate  for  half  hour  or  so.  Remove  and 
wash  down  cover-glass  and  sides  of  beaker,  add  10  cc.  of  1  I  1  H2S04  and  evaporate 
to  strong  fumes  of  sulphuric  acid.  In  case  of  very  siliceous  material,  it  is  well  to 
break  up  the  silica  with  a  glass  rod  before  adding  the  sulphuric  acid.  After 
fuming,  the  solution  is  cooled  and  diluted  to  40  to  50  cc.  and  about  a  gram  of 
20-mesh  aluminum  added.  Cover  with  a  watch  crystal  and  boil  until  water  white 
(about  ten  to  fifteen  minutes).  This  will  reduce  the  iron  and  precipitate  all  the 
hydrogen  sulphide  metals,  except  cadmium.2  The  silica  and  precipitated  metals 
are  filtered  off  and  washed  with  hot  water. 

Add  5  cc.  of  1  :  1  sulphuric  to  the  filtrate  and  dilute  to  100  cc.  Pass  a  rapid 
stream  of  hydrogen  sulphide  through  the  solution  for  fifteen  minutes.  Add 
dilute  ammonia,  a  drop  at  a  time  until  yellow  cadmium  sulphide  precipitates. 
Then  heat  the  solution  to  70  to  90°  C.  and  continue  to  pass  hydrogen  sulphide 
for  a  few  minutes.  Filter  at  once  through  a  close  paper  previously  packed  by 
washing  with  a  polysulphide,  an  acid  and  water.3  The  precipitate  is  washed  with 
cold  8  to  10%  sulphuric  acid  and  finally  with  hot  water.  The  filtrate  is  boiled 
to  remove  hydrogen  sulphide,  cooled,  neutralized  with  potassium  hydroxide 

1  It  is  only  by  adding  an  excess  of  ierrocyanide  that  one  is  assured  of  a  precipitate 
of  normal  composition. 

s  Cadmium  is  partially  precipitated,  but  goes  back  in  solution. 

1  All  the  cadmium  is  separated,  except  about  0.05%,  which  does  not  interfere 
with  the  titration  at  the  given  acidity. 


485 

solution,  and  finally  potassium  carbonate  solution,  to  within  an  acidity  of  a 
couple  of  drops  of  20%  sulphuric  acid.  Methyl  orange  is  used  as  an  indicator. 
Add  from  2  to  4  cc.  of  5%  1  sulphuric  acid  per  100  cc.  of  solution  according  to 
the  amount  of  zinc  present.  Cool  thoroughly.2  A  rapid  stream  of  hydrogen 
sulphide  is  now  passed  through  the  solution  for  forty  minutes.3  Allow  the 
precipitate  to  settle  ten  or  fifteen  minutes,  filter  and  wash  with  cold  water.  A 
hole  is  punched  in  the  filter  paper  and  the  sulphide  washed  back  into  the  beaker 
in  which  it  was  precipitated.  The  filter  paper  and  glass  tube  are  then  washed 
with  10  cc.  of  hydrochloric  acid  in  hot  water,  catching  the  washings  in  the  same 
beaker.  Boil  off  the  hydrogen  sulphide,  add  13  cc.  of  ammonia  (sp.gr.  0.9), 
neutralize  with  hydrochloric  acid,  add  3  cc.  excess  and  dilute  to  200  cc.  Heat 
to  boiling  and  titrate  as  under  Standardization.  When  cadmium  is  absent  or 
present  in  quantities  less  than  0.05,  the  procedure  is  of  course  shortened  con- 
siderably. 

To  Separate  Cadmium  Electrolytically.  After  filtering  off  the  silica  and 
precipitated  hydrogen  sulphide  metals,  add  1  cc.  of  1  :  1  sulphuric  acid,  dilute 
to  125  cc.  and  electrolyze  with  0.8  to  1.0  ampere  per  100  sq.cm.  of  electrode  sur- 
face for  1£  hours  at  2.95  to  3.05  volts.  Proceed  with  the  residual  solution  as 
above.  As  in  all  electrolytic  separations  the  current  must  be  carefully  watched. 

Procedure  with  Material  Containing  Insoluble  Zinc 

Proceed  as  usual  up  to  point  where  the  solution  is  to  be  reduced.  Filter 
off  the  silica  and  insoluble  material,  wash  with  hot  water  and  proceed  with  the 
filtrate  as  usual.  Burn  the  insoluble  residue  in  a  platinum  crucible,  taking  the 
usual  precautions  in  case  lead  is  present.  Fume  off  the  silica  with  hydrofluoric 
and  sulphuric  acids  and  fuse  with  acid  potassium  sulphate.  Dissolve  in  water 
and  sulphuric  acid  and  proceed  as  in  the  regular  method.  The  solution  may  be 
added  to  the  main  portion  or  analyzed  separately. 

Discussion  on  Separating  Zinc  as  Zinc  Sulphide  and  Titrating 
in  Acid  Solution 

Precipitation.  The  method  of  precipitating  zinc  as  sulphide  in  sulpnuric 
acid  solution  was  investigated  by  G.  Weiss  (Inaugural  Dissertation,  Miinchen, 
1906),  and  the  work  confirmed  by  the  author.  The  main  points  of  Weiss'  paper 
are  as  follows: 

1.  "  Sulphate   solutions   are    preferable   to    chlorides."     A  N/10    chloride 
solution  is  not  completely  precipitated  by  H2S.     Furthermore,  the  precipitate  of 
sulphide  from  HC1  solution  when  quantitative  is  not  crystalline  and  easy  to 
filter  like  that  obtained  from  sulphate  solution. 

2.  "  The  concentration  of  a  sulphate  solution  is  without  influence  on  the 
completeness  of  precipitation  from  N/10  down.    That  is  for  solutions  containing 
at  most  400  milligrams  ZnO  per  100  cc." 

3.  "  Sulphate  solutions  of  400  milligrams  ZnO  per  100  cc.  may  be  N/100  acid 
with  H2S04  before  beginning  the  precipitation."    Even  at  acidity  N/20  before 

1  Bear  in  mind  at  this  point  the  acid  liberated  by  the  action  of  H2S  in  the  zinc 
sulphate.     See  Discussion  below. 

2  In  cold  solution  the  precipitate  is  more  granular  and  easier  to  filter. 

3  The  hydrogen  sulphide  should  pass  through  at  a  rate  of  at  least  eight  bubbles  per 
second. 


486  ZINC 

precipitation  less  than  a  milligram  of  zinc  remains  unprecipitated.  According 
to  Weiss,  if  the  solution  were  diluted  to  300  cc.  1.3  grams  of  H2SO4  could  be 
added  or  6|  cc.  of  20%  H2S04,  and  still  have  the  precipitation  complete.  Even 
if  as  much  as  10  cc.  of  20%  acid  were  added  the  loss  would  still  be  only  a  little 
more  than  1  milligram.  Precipitating  300  milligrams  from  100  cc.,  however, 
only  100  milligrams  or  |  cc.  of  20%  acid  could  be  added.  This  means  that  when 
the  solution  becomes  more  acid  than  550  milligrams  of  H2S04  per  100  cc.  the 
precipitation  of  ZnS  ceases.  Knowing  approximately  the  zinc  content  of  a 
solution  one  can  easily  calculate  the  H2S04,  freed  when  the  ZnS04  is  converted 
into  ZnS,  and  the  difference  between  550  milligrams  and  this  calculated  H2S04 
is  the  amount  of  acid  that  may  be  added  when  precipitating  from  100  cc.  of  solu- 
tion. For  two  hundred  cc.  of  course  more  acid  can  be  added,  being  the  differ- 
ence between  1.100  grams  and  the  calculated  H2S04  freed  from  the  ZnS04. 
One  and  one-half  times  the  amount  of  Zn  judged  to  be  present  is  close  enough 
for  the  H2S04  freed. 

4.  "  The  precipitation,  under  the  above  given  conditions,  is  incomplete  when 
a  slow  current  of  hydrogen  sulphide  is  used  (about  four  bubbles  per  second) .     One 
must  work  with  as  fast  a  stream  as  possible  without  causing  mechanical  losses 
(at  least  eight  bubbles  per  second)."    Weiss  is  the  first  one  to  discuss  this  all- 
important  question  in  the  precipitation  of  ZnS.    His  explanation  of  the  efficacy 
of  the  rapid  stream  of  H2S  is  as  follows: 

The  precipitation  takes  place  according  to  the  following  equation: 

ZnS04+H2S  ±=»  ZnS+H2S04. 

Equilibrium  is  reached,  i.e.,  the  velocity  becomes  equal  in  both  directions,  and 
precipitation  ceases  when  the  amount  of  H2S04  per  100  cc.  reaches  a  certain 
point,  under  a  given  set  of  conditions.  Let  these  conditions  remain  exactly 
the  same  with  the  exception  of  the  H2S  and  have  the  active  mass  of  that  increased. 
The  equilibrium  will  be  displaced  from  left  to  right  and  as  a  consequence  ZnS 
will  come  down  in  the  presence  of  more  acid  than  before.  H2S  is  not  very  sol- 
uble in  water  at  room  temperature,  but  if  one  increases  the  surface  of  contact 
between  the  two  the  H2S  is  dissolved  much  more  rapidly  and  consequently  the 
mass  of  H2S  active  at  any  time  greatly  increased.  This  is  exactly  what  is  accom- 
plished when  the  zinc  solution  is  constantly  kept  full  of  bubbles  of  H2S.  One 
can  easily  see  how  greatly  increased  the  mass  of  H2S  would  be  in  the  extreme 
case,  when  the  solution  is  all  foam. 

5.  "  A  strong  current  of  gas,  like  that  called  for  above,  will  precipitate  the 
usual  amounts  of  zinc  used  in  analytical  operations  in  forty  minutes." 

6.  "  At  temperatures  above  50°  the  precipitation  is  incomplete;    further- 
more, at  room  temperature  the  ZnS  comes  down  in  a  form  suitable  for  filtra- 
tion." 

Weiss  found  that  not  only  were  the  precipitations  incomplete  at  high  tempera- 
tures, but  the  precipitate  was  finer  and  much  more  difficult  to  filter. 

7.  "  Water  only  is  required  for  washing  the  precipitates." 

End-point.  The  change  of  color  from  blue  to  pea  green  is  very  sharp.  It 
should  be  observed  by  looking  down  through  the  solution  and  not  from  the  side. 
The  change  in  color  may  be  explained  as  follows:  The  ferrocyanide,  having  stood 
for  three  or  four  weeks,  has  oxidized  slightly  to  ferricyanide,  due  to  dissolved 
oxygen  in  the  water.  The  few  tenths  of  a  milligram  of  ferrous  iron  added  acts 
with  this  ferricyanide  giving  the  ferro-ferricyanide  blue  as  long  as  the  ferro- 


ZINC  487 

cyanide  is  not  in  excess.    When  it  is  in  excess  the  blue  is  decomposed  and  gives 
the  colorless  ferro-ferricyanide. 

In  case  the  ferrocyanide  solution  is  freshly  prepared,  it  is  well  to  add  about 
300  milligrams  of  ferricyanide  to  each  liter. 

DETERMINATION  OF  SMALL  AMOUNTS  OF  ZINC 

The  following  method  is  applicable  to  samples  containing  0.05%  Zn  or  less. 

Procedure.  A  large  sample,  10  or  20  grams,  is  brought  into  solution  by  the 
standard  procedure,  taken  to  fumes  of  sulphuric  acid  and  the  zinc  precipitated 
as  sulphide  after  separating  groups  5  and  6  by  the  procedures  given  under 
Standard  Method,  filtered  and  dissolved  in  hydrochloric  acid.  The  sample  is 
now  washed  into  a  100-cc.  Nessler  tube,  5  cc.  of  ferrocyanide  added  and  the 
whole  made  up  to  the  mark,  mixed  by  pouring  into  a  beaker  and  then  back  into 
the  tube.  A  standard  containing  the  same  amount  of  acid  is  made  up  and  a 
standard  zinc  chloride  solution  added  until  the  turbidity  of  standard  and  unknown 
are  the  same.  From  the  amount  of  zinc  added  to  the  standard  the  percentage 
can  be  calculated.  The  standard  zinc  solution  is  made  up  by  dissolving  C.P. 
zinc  in  hydrochloric  acid  and  diluting  so  that  1  cc.  is  equal  to  1  milligram  of 
zinc. 

SPECIAL  METHODS 
Determination  of  Metallic  Zinc  in  Zinc  Dust 

Discussion.  From  time  to  time,  there  have  been  proposed  various  methods 
for  determining  the  metallic  content  of  zinc  dust.  Most  of  these  are  based  on  the 
measure  of  its  reducing  power,  for  example,  on  potassium  bichromate,  iodate,  ferric 
sulphate  and  the  like.  However,  none  of  these  gives  as  consistently  accurate 
results  as  the  hydrogen  evolution  method.  The  apparatus  described  below  was 
proposed  by  Franz  Meyer  in  1894,  and  the  method  thoroughly  investigated  by 
Morse  and  Barnes,  de  Koninck  and  Grandry.  Their  conclusions  as  to  its  accu- 
racy have  been  confirmed  by  the  author. 

The  methods  based  on  the  precipitation  of  a  metal,  for  example,  silver  from 
a  solution  of  silver  cyanide  in  potassium  cyanide,  while  they  may  give  informa- 
tion as  to  the  efficiency  of  the  zinc  dust  under  certain  conditions,  such  as  in 
cyanide  work,  they  do  not  give  the  metallic  zinc  content. 

The  determination  is  best  made  by  measuring  the  volume  of  hydrogen  evolved 
when  the  sample  is  treated  with  dilute  sulphuric  acid. 

The  apparatus,  which  is  similar  to  a  nitrometer,  consists  of  a  graduated  tube 
72  cm.  long,  having  a  bulb  at  the  top  capable  of  holding  260  cc.,  the  total  capacity 
of  the  bulb  and  tube  being  400  cc.  The  tube  is  graduated  in  0.25  cc.  By  means 
of  ground-glass  joints  connection  is  made  with  a  special  three-way  stop-cock 
and  a  decomposing  flask  with  a  capacity  of  350  cc.  The  stop-cock  is  special 
in  that,  while  it  resembles  an  ordinary  three-way  cock  in  every  other  respect, 
it  has  an  extra  hole  at  right  angles  to  and  connecting  with  the  opening  leading 
to  a  leveling  bottle.  Fig.  72  gives  a  sketch  of  the  apparatus. 

Procedure.  One  gram  of  zinc  dust  is  rapidly  weighed  and  transferred  to 
the  dry  decomposing  flask.1  Approximately  5  grams  of  C.P.  ferrous  sulphate 

1  The  sample  should  be  weighed  rapidly,  and  the  flask  be  perfectly  dry,  on  account 
of  the  ease  with  which  the  finely  divided  zinc  oxidizes. 


488 


ZINC 


and  a  piece  of  platinum  about  2  cm.  square  are  placed  in  the  flask.1  Water  is  now 
added  almost  up  to  the  neck,  the  connection  holding  the  stop-cock  is  put  in 
place  and  the  flask  completely  filled  with  water.  The  connection  is  now  made 
with  the  measuring  tube  and  the  stop-cock  turned  to  position  1  (Fig.  73).  By 


400cc. 


Rubber  Tubing  ft) 
\LevelingBottle 


•Ground 


Ground 


<^ 


FIG.  73. 


'Ground 


Ground 


FIG.  72. 


FIG.  74. 


means  of  the  leveling  bottle  the  tube  is  filled  with  dilute  sulphuric  acid  (1  :  10). 
The  stop-cock  is  now  turned  to  position  2  (Fig.  74).  The  acid  descends  into  the 
flask,  and  the  evolved  hydrogen  passes  up  into  the  measuring  tube.  The  appa- 
ratus is  shaken  from  time  to  time,  but  care  should  be  taken  not  to  allow  a  too 
vigorous  evolution  of  gas. 

1  The  ferrous  sulphate  and  platinum  act  as  catalytic  agents,  increasing  the  rate 
of  evolution  of  hydrogen. 


ZINC 


489 


When  all  the  hydrogen  is  evolved,  which  takes  from  two  to  twelve  hours, 
depending  on  the  composition  of  the  zinc  dust,1  the  volume  is  measured,  tem- 
perature and  pressure  taken,  and  the  volume  reduced  to  0°  and  760  mm.  The 
volume  of  hydrogen  is  calculated  to  zinc  by  multiplying  by  the  factor  0.2919  and 
dividing  by  a  factor  to  correct  for  the  solubility  of  hydrogen  in  1  :  10  sulphuric 
acid.  This  factor  is  determined  by  running  samples  of  C.P.  zinc.  The  sulphuric 
acid  can  be  saturated  with  hydrogen  before  using,  in  which  case  the  correction 
factor  can  be  made  negligible.2 


DETERMINATION  OF  IMPURITIES  IN  SPELTER 

LEAD 

Electrolytic  Method.  The  sample  is  thoroughly  mixed  on  a  sheet  of 
paper,  and  pieces  showing  discoloration  are  discarded.3  The  pieces  are  removed 
from  the  paper  by  lifting,  not  pouring.  A  magnet  is  passed  over  the  sample  to 
remove  particles  of  iron. 

8.643  grams  4  are  weighed  into  a  250-cc.  beaker,  about  100  cc.  of  distilled 
water  added,  and  40  cc.  of  concentrated  nitric  acid  added  gradually  until  solu- 
tion is  complete.  The  solution  is  boiled  to  expel  all  nitrous  fumes  and  diluted 
to  200  cc.  with  distilled  water,  4  or  5  drops  of  5%  silver  nitrate  added  to  pre- 
cipitate any  traces  of  chlorine  present,  and  the  solution  electrolyzed  hot.  For  sam- 
ples low  in  lead,  as  high  grade,5  a  current  of  0.25  ampere  is  used,  and  for  inter- 
mediate, brass  special  and  prime  western,  0.50  ampere.  The  anode  is  made  of 
sheet  platinum  and  is  sand  blasted.  It  has  a  surface  of  135  sq.cm.  A  spiral 
of  platinum  wire  is  used  as  a  cathode.  The  time  required  is  from  one  and  one- 
half  to  two  hours.  The  solutions  are  tested  for  lead  before  shutting  off  the 
current,  by  raising  the  liquid  in  the  beaker,  allowing  to  continue  for  twenty 
minutes  and  if  there  is  no  fresh  deposit,  the  anode  is  washed  three  times  with 

1  It  is  a  well-known  fact  that  very  pure  zinc  is  only  slowly  dissolved  by  sulphuric 
acid. 

2  If  the  sample  contains  iron  in  sufficient  quantity  to  influence  the  result,  a  correc- 
tion should  be  made. 

3  The  sample  should  be  taken  by  pouring  the  molten  metal  into  water,  thus 
granulating  it,  or  by  sawing  or  drilling  the  slabs.     In  this  latter  case  the  slabs  should 
be  sawed  or  drilled  completely  through.     No  lubricant  should  be  used.    The  sample 
is  then  washed  with  water,  dried  and  run  under  a  magnet. 

4  This  is  an  empirical  factor  weight,  0.866  being  the  theoretical  factor  to  convert 
the  dioxide  to  lead.    See  E.  F.  Smith,  Electroanalysis. 

5  The  rejection  limits  for  spelter  of  the  American  Society  for  Testing  Materials 
consider  four  grades  as  follows: 


Designation. 

Proportion 
of  Lead. 

Proportion 
of  Iron. 

Proportion 
of  Cadmium. 

Total 
Proportion  of 
Impurities. 

0.07 

0.03 

0.05 

0  10 

B  or  intermediate  

0.20 

0.03 

0  50 

0.50 

C  or  brass  special 

0  75 

0  04 

0  75 

1  20 

D  or  prime  western    .    .  . 

1  50 

0  08 

Each  grade  should  be  free  of  aluminum. 


490  ZINC 

distilled  water,  and  once  with  alcohol,  dried  in  the  air  bath  at  210°  C.  for  one- 
half  hour  and  weighed. 

The  weight  of  Pb02  found  (in  milligrams)  divided  by  100  gives  the  percentage 
of  lead. 

"  Lead  Acid  "  Method.  Add  1  gram  of  lead  acetate  in  300  cc.  of  water 
to  dilute  sulphuric  acid  (300  cc.  acid  to  1800  cc.  of  water).  Shake  well,  allow 
to  cool  and  settle.  Filter  off  the  precipitated  lead  sulphate.  By  the  use  of 
this  sulphuric  acid  saturated  with  lead,  the  solubility  of  lead  sulphate  need  not 
be  considered,  the  solution  being  brought  back  to  the  same  concentration  each 
time. 

Procedure.  Weigh  10  grams  of  the  sample  into  a  400-cc.  beaker  and  add 
120  cc.  of  "  lead  acid."  When  all  but  about  10%  of  the  zinc  is  dissolved,  filter 
and  wash  with  lead  acid.  Retain  the  filtrate.  Wash  the  metallics  back  into  the 
beaker  and  dissolve  in  nitric  acid.  Add  40  cc.  of  "  lead  acid  "  and  evaporate  to 
strong  fumes.  Cool  and  add  35  cc.  of  water,  which  is  the  amount  evaporated 
from  the  "lead  acid,"  and  heat  to  boiling.  Add  the  filtrate  containing  most 
of  the  zinc  and  a  little  lead  sulphate,  stir  and  allow  to  settle  over  night.  Filter 
on  a  Gooch  crucible,  wash  with  lead  acid,  a  mixture  of  alcohol  and  water  (1  :  1), 
finally  with  alcohol  and  ignite  inside  a  porcelain  crucible  and  weigh  as  lead 
sulphate. 

IRON 

Hydrogen  Sulphide  Method.  Weigh  10  grams  of  sample  which  has  had 
any  metallic  iron  particles  or  iron  containing  dust  removed  with  a  magnet. 
Place  in  a  250-cc.  beaker,  and  dissolve  with  50  cc.  concentrated  hydrochloric  acid. 
Let  stand  several  minutes  until  violent  action  has  ceased,  then  add  about  1  cc. 
potassium  chlorate  solution  (50  grams  per  liter),  and  boil  until  the  chlorate  is  all 
decomposed.  Cool,  add  50  cc.  of  water  and  neutralize  the  solution  with  ammonia, 
adding  a  large  excess,  boil  for  two  or  three  minutes,  allow  the  precipitate  to 
settle,  filter  and  wash  with  hot  dilute  ammonia  water  and  finally  with  hot  water. 
Dissolve  the  precipitated  hydroxide  of  iron  into  a  16-ounce  Erlenmeyer  flask, 
using  10  cc.  dilute  sulphuric  acid  (1  :  4).  Wash  the  paper  thoroughly  with  hot 
water,  dilute  to  a  volume  of  about  300  cc.  and  reduce  the  iron  by  passing  hydrogen 
sulphide  through  the  solution  for  five  minutes,  boil  to  expel  excess  of  hydrogen 
sulphide,  being  careful  to  exclude  the  air  by  means  of  a  Bunsen  valve.  Test 
for  hydrogen  sulphide  with  a  piece  of  moistened  lead  acetate  paper.  Cool  rapidly 
and  titrate  with  permanganate,  1  cc.  of  which  is  equal  to  approximately  0.00034 
gram  of  iron.  Run  a  blank  determination  in  order  to  determine  the  amount  of 
permanganate  necessary  to  show  the  pink  color  on  titration.  Standardize  the 
permanganate  against  sodium  oxalate.  (Bureau  of  Standards.) 

Colorimetric  Method 

Solutions.    Ammonium  Sulphocyanate.     One  part  salt  to  2  parts  of  water. 

Potassium  Chlorate.     One  part  salt  to  20  parts  of  water. 

Standard  Iron  Solution  I.  One  to  50  grams  of  granulated  zinc  of  low  iron 
content  are  dissolved  in  800  to  1000  cc.  of  hydrochloric  acid  and  oxidized  with 
potassium  chlorate.  The  solution  is  boiled  to  expel  chlorine  fumes,  and  made 
up  to  2500  cc.  This  solution  is  standardized  by  measuring  off  50-cc.  portions, 
corresponding  to  10  grams  of  zinc,  and  determining  the  iron  content  by  the 
hydrogen  sulphide  method. 


ZINC  491 

Standard  Iron  Solution  II.  0.7  gram  of  ferrous  ammonium  sulphate  is 
dissolved  in  water,  10  cc.  dilute  sulphuric  acid  added,  and  the  iron  oxidized  with 
permanganate.  The  solution  is  now  diluted  to  1000  cc.  One  cc.  equals  0.0001 
gram  iron. 

Procedure.  Ten  grams  of  sample  are  dissolved  and  oxidized  as  given  under 
the  hydrogen  sulphide  method.  The  solution  is  cooled  and  diluted  to  about 
25  cc.  and  transferred  to  a  comparison  tube,1  2  cc.  of  the  sulphocyanate  solution 
are  added,  and  the  volume  brought  up  to  100  cc.  and  mixed  by  pouring  into  the 
beaker  and  back  into  the  tube.  Compare  the  red  color  with  the  color  produced 
on  adding  2  cc.  of  sulphocyanate  to  50  cc.  of  standard  iron  solution  I,2  and 
diluting  to  100  cc.  Add  standard  iron  solution  II  until  the  colors  are  the  same, 
and  calculate  the  iron  present  in  the  unknown.  In  case  the  iron  is  over  0.030, 
it  should  be  determined  by  the  hydrogen  sulphide  method. 

CADMIUM 

Sulphide  Method.  Twenty-five  or  50  grams  are  weighed  in  a  liter  flask,  200 
cc.  water  are  added  followed  by  25  cc.  of  (1  :  1)  sulphuric  acid.  (In  case  of  high- 
grade  spelter,  add  a  piece  of  platinum  to  accelerate  the  action.)  Add  more  acid 
from  time  to  time,  or,  if  the  action  is  too  violent,  add  water.3  When  the  greater 
part  of  the  zinc  is  in  solution,  filter  off  the  metallics,  leaving  the  greater  portion 
in  the  flask,  and  wash  with  hot  water.  Wash  the  metallics  on  the  filter  paper 
back  into  the  flask,  add  nitric  acid  and  heat  until  all  is  in  solution,  then  add 
25  cc.  (1  I  1)  sulphuric  acid  and  take  down  to  dense  white  fumes  and  cool.  Care- 
fully add  water  and  heat  until  soluble  salts  are  in  solution,  allow  to  cool  and  let 
the  PbS04  settle.  Filter  and  wash,  dilute  to  200  cc.  and  pass  hydrogen  sulphide 
through  the  solution  fifteen  or  twenty  minutes,  then  add  a  few  drops  (4  to  5)  of 
ammonia  and  pass  hydrogen  sulphide  about  ten  minutes  more.  If  no  precipi- 
tate appears,  add  a  drop  or  two  more  of  ammonia  and  repeat  in  about  five  min- 
utes. Continue  until  a  precipitate  of  CdS  and  ZnS  is  obtained.  Filter,  wash 
with  cold  water,  and  dissolve  in  (1  :  1)  hydrochloric  acid,  wash  and  add  12  to  15 
cc.  of  1  I  1  sulphuric  acid  and  evaporate  to  fumes,  dilute  to  100  cc.  and  pass 
hydrogen  sulphide.  Add  ammonia  as  before  but  not  so  much  at  a  time. 
Finally,  1  or  2  drops  will  give  a  clean  yellow  precipitate.  In  case  a  large  amount 
of  cadmium  is  present,  a  third  precipitation  is  necessary.  (This  is  usually 
desirable  in  any  case.)  Filter  at  once  on  a  weighed  Gooch,  wash  with  cold 
water,  alcohol,  carbon  bisulphide  and  alcohol.  Dry  at  110°,  and  weigh  as 
cadmium  sulphide. 

The  cadmium  may  also  be  weighed  as  cadmium  sulphate  or  as  phosphate. 

Electrolytic  Method.  The  same  procedure  is  followed  as  given  in  the  pre- 
ceding method.  After  the  lead  sulphate  is  filtered  off,  enough  water  is  added 
to  make  the  sulphuric  acid  content  5  to  7%;  about  5  grams  of  potassium  sul- 
phate are  then  added  and  the  solution  electrolyzed  for  an  hour  to  an  hour  and 
a  half  with  0.20  to  0.35  ampere  at  2.75  volts  at  the  beginning  to  2.95  to  3 

1  Clear  glass  test-tubes  f  in.  in  diameter,  and  holding  110  cc.  make  good  com- 
parison tubes. 

2  The  zinc  content  of  the  standard  and  unknown  must  be  approximately  the  same. 
(See  references,  Bureau  of  Standards  Bulletin.) 

3  Care  should  be  taken  that  the  solution  does  not  proceed  too  rapidly.     The  metallics 
should  contain  about  5%  of  zinc. 


492  ZINC 

volts  at  the  end.  The  electrode  is  of  platinum  and  is  coated  with  cadmium.1 
It  has  a  surface  of  75  sq.cm. 

The  cathode  is  washed  three  times  with  water,  dipped  into  alcohol  and 
burned  off  carefully,  or  it  may  be  dipped  into  ether  and  dried  in  an  oven. 

Discussion.  Lead  can  be  more  rapidly  determined  by  using  higher  cur- 
rents, e.g.,  up  to  5  amperes,  by  rotating  the  electrode,  or  by  means  of  the  sole- 
noid of  Frary.2  However,  where  a  great  number  of  determinations  are  made, 
the  slower  electrolysis  is  to  be  preferred. 

In  cases  where  only  an  occasional  analysis  is  made,  the  lead  acid  method 
should  be  used. 


Determination  of  Impurities  in  Zinc  Oxide 

See  chapter  on  analysis  of  paint  pigments,  page  627. 

REFERENCES 

General 

H.  Nissenson,  Die  Untersuchungs  Methoden  des  Zinks. 

Bibliography  1890-1911,  Jr.  I.  and  E.  Chem.,  June,  1912. 

Report  of  Sub-Committee  on  Zinc  Analysis,  Jr.  A.  C.  S.,  29,  262. 

Certificate  of  Analysis,  Standard  Sample  37,  Sheet  Brass,  Bureau  of  Standards. 

Breyer,  Proceedings  Eighth  International  Congress,  25,  7. 

Titration  in  Acid  Solution: 

De  Koninck  and  Prost.,  Zeit.  fur  angew.  Chem.,  1896,  pp.  460  and  564. 

Waring,  Jr.  A.  C.  S.,  26,  4,  1904. 

Seamon,  Jr.  A.  C.  S.,  29,  205,  1907. 

Columbia  School  of  Mines  Quarterly,  April,  1900,  p.  267. 

Voigt,  Zeit.  fur  angew.  Chem.,  1911,  p.  2195;  1912,  pp.  205  and  1005. 

G.  Weiss,  Inaugural  Dissertation,  Miinchen,  1906. 

Lehner  and  Meloche,  Proceeding  Eighth  International  Congress,  1,  279. 

Technical  Methods  of  Ore  Analysis,  Low. 

Manual  for  Assayers  and  Chemists,  Seamon. 

Metallurgical  Analysis,  De  Merest. 

Titration  in  Alkaline  Solution: 

Nissenson,  Untersuchungs  Methoden. 

Voigt,  Zeit.  fur  angew.  Chem.,  June,  1898,  p.  307. 

Giudice,  Chem.  Zeit.,  6,  1034,  1882. 

Donath  and  Hottensaur,  Chem.  Zeit.,  14,  323,  1890. 

Moldhauer,  Chem.  Zeit.,  13,  1220,  1889. 

Blum.  Zeit.  f.  anal.  Chem.,  81,  60,  1892. 

Van  Osdel,  Eng.  and  Min.  Jr.,  84,  730,  1908. 

1  The  gauze  electrode  is  prepared  as  follows:   It  is  first  coated  with  copper  by 
electrolyzing  a  hot  copper-sulphate  solution   containing  250   milligrams  of  copper 
sulphate  and  1  cc.  of  sulphuric  acid  per  100  cc.  of  solution.     This  is  then  coated  with 
cadmium,  using  a  sulphate  solution  containing  about  100  milligrams  of  cadmium 
sulphate  and  5  to  10%  of  sulphuric  acid.    The  electrode  can  be  used  over  and  over 
again. 

2  Zeit.  f .  Electrochemie,  1907. 


ZINC  493 


Electrolytic  and  Gravimetric: 


Spear  Wells  and  Dyer,  Jr.  A.  C.  S.,  Dec.,  32,  530-38. 

Spear  and  Strahan,  Jr.  I.  and  E.  C.,  Dec.,  1912,  p.  889. 

Spitzer,  Zeit".  fur  electro.  Chemie,  June  23,  1905. 

Denso,  Zeit.  fur  electro.  Chemie,  June  9,  1903. 

Chemiker  Zeit.,  July  29,  1905. 

Foerster,  Zeit.  fur  angew.  Chem1?  19,  1906,  1890. 

Electro-Analysis,  E.  F.  Smith. 

Dakin,  Zeit.  fur  anal.  Chem.,  39,  273,  1900. 

Langley,  J.  A.  C.  S.,  31,  1051,  1909. 

Sullivan  and  Taylor,  J.  I.  and  E.  C.,  1,  475. 

Classen,  Ausgewahlte  Methoden  d.  Anal.  Chem.,  1901,  1.  Bd.,  S.  330. 

Separations: 

Nissenson  and  Kettembeil,  Chem.  Zeit.,  29,  951,  1905. 

Untersuchungs  Methoden. 
Breyer,  Proceedings  Eighth  Congress,  25,  7. 
Prosst  and  Hossreedter,  Zeit.  fur  angew.  Chem.,  5,  166,  1892. 
E.  Jensch,  Zeit.  fur  angew.  Chem.,  12,  465,  1899. 

Hampe  and  Fraatz,  Zeit.  f .  Berg.  Rutten  and  Salinenussen,  25.  253.  1879. 
Waring,  J.  A.  C.  S.,  26,  1904. 
Baubigny,  Compt.  Rend.,  1882,  94,  1183;  95,  34. 
Nissenson  and  B.  Neuman,  Chem.  Zeit.,  19,  1624,  1895. 

Metallic  Zinc: 

Meyer,  Zeit.  f.  angew.  Chem.,  7,  331,  1894. 

De  Koninck  and  Grandry,  Bull,  de  PAssoc.  de  Chimie,  16,  284,  1902. 

Nissenson,  Untersuchungs  Methoden. 

R.  G.  Max  Leibig,  Zinc  urid  Cadmium,  p.  30. 

Herz,  Bulletin  American  Institute  of  Mining  Engineers,  August,  1915. 

Spelter  Analysis: 

E.  F.  Smith,  Electroanalysis. 

Jr.  Ind.  and  Eng.  Chem.,  7,  No.  6,  p.  547. 

Seamon,  Manual  for  Assay ers  and  Chemists. 

Nissenson,  Untersuchungs  Methoden. 

Amer.  Soc.  for  Testing  Materials,  Year  Book,  1915,  p.  344. 

Bull,  of  Bureau  of  Standards,  3,  No.  1,  p.  115. 

Metallurgical  Analysis,  De  Merest. 


ZIRCONIUM 

R.  STUART  OwENs.1 
Zr,  at.wt.  90.6;  sp.gr.  4.15;  m.p.  1700°±  C.;  oxides  ZrO2,  ZrO3. 

DETECTION 

The  zirconium  having  been  brought  into  solution  by  one  of  the  methods 
outlined  below  may  be  distinguished: 

(1)  By  the  addition  of  sodium  phosphate  to  a  slightly  acid  solution.    A  white 
precipitate  which  is  difficultly  soluble  in  hydrochloric  acid  is  characteristic  of 
zirconium. 

(2)  By  its  solution  in  hydrochloric  acid  coloring  turmeric   paper  orange. 
Titanium,  however,  colors  it  brown,  and  will  mask  the  color  due   to  zirconium, 
when  both  are  present,  hence  it  is  necessary  to  reduce  the  titanium  by  the  addi- 
tion of  a  few  pieces  of  zinc.    Reduced  titanium  does  not  color  turmeric  paper,  but 
it  oxidizes  rapidly,  hence  the  test  should  be  made  as  quickly  as  possible.    Boric 
acid  also  produces  a  yellow  color  with  turmeric  paper,  but  both  elements  are 
met  with  in  the  same  sample  on  very  rare  occasions  only. 

(3)  From  alumina  by  the  solubility  of  its  carbonate  in  an  excess  of  an  alkali 
carbonate.    The  solution  from  ammonium  carbonate  if  boiled  precipitates  zir- 
conia. 

(4)  From   glucinum   by   the    insolubility   of   its   hydroxide   in   ammonium 
chloride.     Glucinum  hydroxide  dissolves  readily  in  the  reagent. 

(5)  By  spectroscopic  methods.     Zirconium  shows  lines  of  greatest  intensity 
in  the  arc  spectrum  at  4687.9,  4739.6,  4772.5,  4815.8,  and  in  the  spark  spectrum 
at  3999.1,  4149.4,  4209.4,  4380.1.* 

ESTIMATION 

The  determination  of  zirconium  is  required  in  minerals,  artificial  gems, 
incandescent  gaslight  mantles,  firebrick,  enamels,  glass  and  various  salts  of  the 
mineral  acids.  The  chief  source  of  zirconium  is  the  mineral  zircon  (ZrSi04) 
and  its  valuable  modifications  as  hyacinth.  Zircon  contains  from  60  to  67% 
of  Zr02. 

Preparation  and  Solution  of  the  Sample 

A.  Materials  Containing  a  Large  Amount  of  Silica 

Decomposition  by  Hydrofluoric  Acid.  Five  grams  of  the  finely  powdered 
sample  are  treated  in  a  large  platinum  dish  with  50  cc.  HF  and  50  cc.  of  H2SO4. 
When  the  violent  action  has  ceased  the  solution  is  evaporated  first  on  the  steam 
bath  to  expel  the  HF  and  then  on  a  sand  bath  till  fumes  of  S08  are  given  off.  The 

1  Research  Chemist,  New  York  City. 
a  All  of  these  lines  are  in  the  visible  spectrum. 
494 


ZIRCONIUM  495 

residue  is  taken  up  with  water.  This  usually  effects  complete  solution  of  the 
sample.  If,  however,  an  insoluble  residue  still  remains,  it  is  filtered  off,  washed 
with  cold  water,  ignited  in  platinum,  and  fused  with  10  parts  by  weight  of  potas- 
sium acid  sulphate.  The  cooled  fusion  is  dissolved  by  boiling  with  20%  HC1. 
All  the  zirconium  will  now  be  in  solution  and  may  be  determined  as  detailed 
below.  Barium  if  present  will  remain  insoluble  and  should  be  filtered  off. 

NOTES.  Heating  the  mineral  to  dull  redness  and  suddenly  plunging  into  cold 
water  enables  zircon  to  be  easily  pulverized. 

If  the  KHSO4  fusion  is  extracted  with  dilute  H2SO4  and  boiled,  the  white  basic 
sulphate,  3ZrO2-S03,  is  apt  to  form  and  remain  in  the  residue. 

B.  General  Method  for  Minerals,  Oxides,  etc. 

Decomposition  by  Fusion  with  an  Alkali  Carbonate.  Two  grams  of 
the  finely  pulverized  sample  are  fused  with  10  grams  of  Na2C03  (free  of  sulphur) 
and  |  gram  of  KN03  in  a  large  platinum  dish.1  The  melt  is  taken  up  in  water 
and  if  manganese  is  present  a  few  drops  of  alcohol  are  added  to  reduce  the  man- 
ganate  to  the  manganous  condition.  The  solution  is  filtered  and  the  residue 
washed  with  dilute  NaOH  solution.  The  filtrate  then  contains  all  the  silica  as 
sodium  silicate,  while  the  residue  contains  all  the  zirconium,  barium,  etc.  .The 
residue  is  dissolved  in  dilute  H2S04  and  the  zirconium  present  determined  as 
detailed  below. 

C.  Other  Methods  of  Decomposition  which  are  Sometimes  Used 

Fusion  with  acid  potassium  fluoride. 

Fusion  with  caustic  soda  and  sodium  fluoride. 

By  long  boiling  with  concentrated  hydrochloric  acid. 

SEPARATIONS 

From  Iron  by  the  volatilization  of  the  iron  as  chloride  in  the  presence  of 
strong  hydrochloric  acid  and  chlorine  at  a  temperature  of  200  to  300°  C.8 

From  Iron.     Zirconium  is  precipitated  free  from  iron  by  phenylhydrazine.3 

From  Titanium  by  precipitating  the  titanium  from  dilute  sulphuric  acid 
solution  by  boiling  iu  the  presence  of  acetic  acid.4 

From  thorium  by  precipitation  of  both  metals  as  oxalates  by  ammonium 
oxalate  and  then  adding  an  excess  of  oxalic  acid  when  the  zirconium  oxalate 
dissolves  completely.5 

From  cerium  and  the  iron  groups  by  boiling  the  hydrochloric  acid  solu- 
tion with  sodium  thiosulphate.  The  zirconium  is  precipitated  as  thiosulphate, 
which  may,  after  filtering  and  washing,  be  ignited  to  the  oxide.6 

Tartaric  acid  prevents  the  precipitation  of  zirconium  hydroxide. 

1  A  nickel  dish  should  be  used  in  place  of  platinum  if  sulphur,  lead  or  phosphorus 
is  preser-t. 

2  Havens  and  Way,  A.  J.  C.,  (4),  7,  217. 

3  Allen,  J.  A.  C.  Si,  25,  426. 

4Streit  and  Franz,  J.  pr.  Chem.,  108,  75;  Streit  and  Franz,  Zeitsch,  anal,  chem., 
9,  388. 

5  Roscoe  and  Schorlemmeyer,  Vol.  II,  Part  II.  p.  276. 
e  Ibid,  p.  272. 


496  ZIRCONIUM 

GRAVIMETRIC    METHODS    FOR  THE    DETERMINATION    OF 

ZIRCONIUM 

Salts  of  Zirconium 

"  A  "  solutions  containing  zirconium  are  treated  with  5  cc.  of  H2S04  and 
evaporated  to  fumes;  taken  up  with  cold  water  and  diluted  to  400  cc. 

"  B  "  dry  salts  are  treated  with  5  cc.  of  H2S04  and  heated  to  fumes  of  S03 
on  a  sand  bath.  The  residue  is  taken  up  with  cold  water  and  diluted. 

Minerals,  Silicates,  etc. 

The  sample  having  been  decomposed  by  one  of  the  methods  outlined  and 
the  zirconium  being  present  in  solution  as  sulphate  the  liquid  is  diluted  so  as  to 
contain  about  1%  of  free  H2S04. 

Determination  as  Phosphate 

To  the  acid  solution  sufficient  H202  is  added  to  oxidize  the  titanium  which 
may  be  present.  (The  solution  is  colored  yellow  by  H202  when  titanium  is 
present.)  A  sufficient  quantity  of  ortho-phosphate  (as  (NH4)2HP04  or  Na2HP04) 
is  added  to  precipitate  all  the  zirconium  as  phosphate  (aluminum  and  iron 
are  not  precipitated  in  the  presence  of  free  acid).  If  titanium  is  present  and  the 
color  bleaches  after  a  time,  more  H202  is  added  until  the  color  is  restored.  (Any- 
reduced  titanium  is  carried  down  with  the  zirconium  phosphate.)  The  precipi- 
tate is  filtered  off,  washed  well  with  water  containing  some  H202,  ignited  and 
weighed  as  zirconium  phosphate,  which  contains  51.8%  of  Zr02.  The  solution 
after  precipitation  should  be  allowed  to  stand  several  hours.  Traces  require 
ten  to  fifteen  hours,  while  considerable  amounts  of  zirconium  require  only  from 
thirty  minutes  to  one  hour  of  settling  on  the  steam  bath  for  complete  precipi- 
tation. 

Determination  as  Zirconium  Oxide 

With  pure  salts  the  zirconium  may  be  precipitated  completely  as  the  hydroxide 
by  the  addition  of  ammonia,  settling  and  finally  igniting  and  weighing  as  the 
oxide,  ZrOj. 

Determination  as  Zirconium  Oxide  in  the  Presence  of  Iron  Oxide  1 

The  aqueous  solution  of  zirconium  and  iron  free  from  other  metals  is  treated 
with  a  slight  excess  of  ammonia  water  and  then  boiled  to  remove  the  excess. 
The  precipitated  hydroxides  are  filtered  off,  washed  with  water,  and  dried  at 
105°  C.  The  filtrate  is  evaporated  to  dryness,  the  residue  taken  up  in  hydro- 
chloric acid  and  the  solution  again  precipitated  as  before.  The  combined  pre- 
cipitates which  have  been  dried  to  constant  weight  in  a  porcelain  crucible  are 
cooled  and  weighed  as  Zr02-Fe203.  The  oxides  are  then  ground  in  a  mortar, 
weighed  into  a  platinum  crucible  and  ignited  to  constant  weight  in  a  current 
of  hydrogen.  Only  the  iron  is  reduced  to  the  metallic  state,  hence  data  are  at 
hand  for  calculating  the  percentages  of  iron  and  zirconium. 

1  Method  of  Gutbier  and  Huller,  Zeit.  anorg.  Chem.,  32,  92. 


PART  II 
SPECIAL  SUBJECTS 


ACIDS 

WILFRED  W.  SCOTT 

To  determine  the  amount  of  free  acid  present  in  a  given  solution,  an  alkaline 
reagent  of  known  strength  is  required,  since  acids  are  most  accurately  estimated 
by  titration.  Under  certain  conditions,  not  only  the  free  acid  but  also  the  com- 
bined is  determined  by  titration,  e.g.,  H2S04  in  A12(S04)3,  (see  Aluminum),  when 
caustic  is  added  to  a  hot  solution  with  phenolphthalein  as  indicator.  When  an 
equivalent  amount  of  caustic  has  been  added  to  the  acid  present  the  solution  be- 
comes neutral,  a  condition  spoken  of  as  the  "  end-point,"  which  is  recognized  by 
means  of  certain  compounds  known  as  indicators.  The  accuracy  of  the  results 
depends  largely  upon  the  choice  of  the  indicator  used. 


INDICATORS 

Indicators  are  usually  dyestuffs,  or  organic  compounds,  which  impart  a 
different  color  to  an  acid  solution  than  to  one  which  is  alkaline.  This  color 
is  attributed  to  a  particular  arrangement  of  atoms  in  the  compound  called 
a  chromophor.  It  is  thought  that  the  change  of  color  is  caused  by  a  slight 
rearrangement  of  the  atoms  in  the  molecule,  or  is  due  to  the  fact  that  in  certain 
cases  the  ions  have  a  different  color  from  the  undissociated  molecules.  A  large 
number  of  indicators  are  known,  but  for  general  purposes  the  following  will  cover 
the  requirement  of  acidimetry  and  alkalimetry — methyl  orange,  methyl  red, 
phenolphthalein,  litmus,  lacmoid. 


INDICATOR 


CONDITION  OF  SOLUTION 


GENERAL  USE  IN  TITRATION 


Methyl  orange, 
acids  =  red 
alkalies  =  yellow. 

Methyl  red. 

As  above. 
Phenolphthalein. 

acids  =  colorless 
alkalies  =  red. 


Cold  solution  Hydrates,  carbonates,  bicarbonates,  sul- 

only.  phides,  arsenites,  silicates,  borates  of  sodium 

potassium,    ammonium,   calcium,    magne- 
sium, barium,  etc. 

Cold  solution  Especially  adapted  for  titration  of  weak 

only.  bases  such  as  NH4OH. 

Cold  solutions.  Alkaline  hydrates,  the  mineral  acids, 
organic  acids,  e.g.,  oxalic,  citric,  tartaric, 
acetic.  The  indicator  very  sensitive  to 
acids  and  adapted  to  titration  of  weak  acids 
— carbonic  acid,  etc. 

Hot  solutions.          The  indicator  is  sensitive  in  hot  solu- 
tions to  the  above.    It  is  generally  used  in 
hot  solutions  for  titration  of  acids  com- 
bined with  comparatively  weak  bases. 
499 


500 


ACIDS 


INDICATOR        CONDITION  OF  SOLUTION  GENERAL  USE  IN  TITRATION 

Litmus.  Cold  solutions.         Hydrates  of  Na,  K,  NH3,  Ca,  Ba,  etc. 

acids  =  red  Silicates    and    arsenates    of    Na    and    K, 

alkalies  =  blue.  HN03,  H2S04,  HC1  and  H2C204. 

Hot  solutions.  In  addition  to  above  neutral  and  acid 
carbonates  of  K,  Na,  Mg;  the  sulphides 
and  silicates  of  Na,  K. 

Lacmoid.  Cold  solutions.         The  alkaline  and  alkaline  earth  hydrates, 

In  alcohol  the  arsenates,  borates,  mineral  acids,  many 

acids  =red  salts  of  metals  which  are  acid  to  litmus  and 

alkalies  =  blue.  neutral   to   lacmoid,    e.g.,    sulphates   and 

chlorides  of  iron,  copper  and  zinc,  hence  of 
value  in  determining  free  acids  in  their 
presence. 

Hot  solutions.  In  addition  to  the  above,  carbonates 
and  bicarbonates  of  K,  Na,  Ca,  Sr,  Ba,  etc. 

In  general,  methyl  orange,  methyl  red  and  lacmoid  are  especially  sensitive  to 
bases,  but  not  so  sensitive  to  acids  and  are  not  used  for  weak  acids.  Phenolphtha- 
lein  is  especially  sensitive  to  acids  and  is  of  value  in  titrating  weak  acids.  Litmus 
is  commonly  used  as  a  test  indicator  (litmus  paper)  though  with  careful  prepara- 
tion, it  is  valuable  for  general  acid  and  alkali  titration. 

The  following  table  compiled  by  Thomson,1  refers  to  the  number  of  atoms  of 
hydrogen  displaced  by  monatomic  metals,  such  as  sodium  or  potassium  in  solution 
as  hydroxides.1 


Acids 

Methyl  Orange 
Cold 

Phenolphthalein 

Litmus 

Name 

Formula 

Cold 

Hot 

Cold 

Hot 

Sulphuric  

H2S04 
HC1 
HNO3 

2 
1 
1 
2 
0 
1 
0 

1 
1 

0 
indicator 
destroyed 
0 
0 
1 

2 
1 
1 
2 
Idil. 
2 
Idil. 
2 
2 

2 
1 
1 
2 
0 

2 
1 
1 
2 

2 
1 
1 
2 
0 

Hydrochloric  

Nitric     

Thiosulphuric  

Carbonic 

H2CO3 
H2SO8 

Sulphurous  
Hydrosulphuric 

0 

0 

Phosphoric 

H3P04 
H3AsO4 
H3AsO3 
HNO2 

H4Si04 
H3BO3 
H2CrO4 
H2C204 
HC2H3O2 
HC4H7O2 
H2C4H4O4 

Arsenic 

Arsenious 

0 

1 

0 

0 
0 

Nitrous 

1 

"2" 
2 
1 
1 
2 
1 
2 
3 

"2" 

2 

Silicic. 

Boric 

Chromic 

Oxalic  

2 
1  nearly 
1  nearly 
2 
1 
2 

2 

Acetic  

Butyric  

Succinic  

Lactic  

HC3H503 
H2C4H406 
H8C6H607 

Tartaric 



Citric 

1  Volumetric  Analysis,  Sutton,  Tenth  Edition,  page  44. 
1.,  12,  432. 


R.  T.  Thomson,  J.S.C., 


ACIDS 


501 


In  general,  the  acid  in  the  indicator  must  be  weaker  than  the  acid  which  it  is 
required  to  determine  by  its  means.  Methyl-orange,  for  example,  is  a  fairly  strong 
acid,  hence  it  is  not  used  for  titration  of  organic  acids  as  the  end  reaction  is  uncer- 
tain; it  is*  not  sensitive  to  carbonic,  hydrocyanic,  boric,  oleic  acids;  on  the 
other  hand,  phenolphthalein,  being  an  extremely  weak  acid,  is  decomposed  by 
organic  acids,  H2C03,  etc.,  hence  is  of  value  in  determination  of  these  acids. 


ULTIMATE  STANDARDS 

Sulphuric  and  hydrochloric  acids  are  generally  used  as  the  ultimate  standard 
acids.  Benzoic  acid  may  also  be  used. 

Sodium  carbonate  is  the  best  of  the  alkali  standards.  This  salt  may  be  pre- 
pared in  exceedingly  pure  form.  It  is  frequently  used  as  the  basic  material  for  the 
volumetric  standardization  of  the  standard  acid. 

Preparation  of  Pure  Sodium  Carbonate 

Bicarbonate  of  Soda  made  by  the  Ammonia-Soda  process  may  be  obtained  in 
exceedingly  pure  form.  The  impurities  that  may  be  present  are  silica,  ammonia, 
lime,  arsenic,  sodium  chloride  and  sodium  sulphate.  With  the  exception  of  silica 
and  lime  the  impurities  may  be  readily  removed  by  washing  the  bicarbonate  of 
soda  several  times  with  cold  water  and  decanting  off  the  supernatant  solution  of 
each  washing  from  the  difficultly  soluble  bicarbonate.  The  washing  is  continued 
until  the  material  is  free  from  chlorine,  as  sodium  chloride  is  the  principal  im- 
purity, and  its  removal  leaves  an  exceedingly  pure  product.  The  bicarbonate  is 
* \ried  between  large  filter  papers  in  the  hot  air  oven  (100°  C.). 

Standard  Sodium  Carbonate  is  made  from  this  pure  sodium  bicarbonate  by 
heating  at  290°  C.  to  300°  C.  in  an  electric  oven.  If  a  constant- 
temperature  oven  is  not  available  a  simple'  oven  may  be  impro- 
vised by  use  of  a  sand  bath  and  a  large  beaker  or  a  sheet-iron 
cylinder  covered  at  the  upper  end  as  shown  in  Fig.  75.  A  ther- 
mometer passing  through  this  shield  registers  the  temperature 
of  the  material,  within  a  large  platinum  crucible.  This  crucible 
rests  upon  a  triangle,  so  that  the  bicarbonate  is  entirely  sur- 
rounded by  an  atmosphere  of  comparatively  even  temperature. 

The  sodium  bicarbonate  is  converted  to  the  carbonate.  Con- 
stant weight  will  be  obtained  in  about  five  or  six  hours.  When 
the  material  no  longer  loses  weight  it  is  cooled  in  a  desiccator 
and  bottled  for  use,  preferably  in  several  small,  glass-stoppered 
bottles.  For  exceedingly  accurate  work  the  material  is  analyzed 
and  allowance  made  for  the  impurities  that  may  still  remain. 
The  error  caused  by  any  such  impurities  is  so  small  that  for  all 
practical  purposes  it  may  be  neglected. 


FIG  75. 


This  purified  sodium  carbonate  is  the  ultimate  standard  for  acidimetric  and 
alkalimetric  volumetric  analysis. 


502 


ACIDS 


PREPARATION  OF  STANDARD  ACID 
Standard  Sulphuric  Acid 

Fifty-two  per  cent  sulphuric  acid  is  in  equilibrium  with  the  average  moisture 
present  in  the  air  of  the  laboratory;  acid  of  this  concentration  is  recommended 
for  the  standard  stock  solution.1 

Pure  94  to  97%  H2S04  is  diluted  with  sufficient  water  so  that  its  gravity  is 


I.01* 
'> 

/ 

^  

"^S 

N 

2  1840 

/ 

V 

O 

/ 

\ 

o. 

/ 

(f)  )  Q36 

/ 

H 

/ 

3.19     94         95         96          97          98         9?          10 

S 

^L 

\ 

1:977 

/ 

\ 

"> 

/ 

^ 

^ 

/ 

\ 

j 

IRI7 

M 

20       40       60       80 
Percent  HZS04  Percent  Free  S03 

FIG.  76.  FIG.  77. 

Specific  Gravity  Charts — Sulphuric  Acid. 


100 


37.7  43.7  52.1         57.6  64.5  73.1         84.5 

Percent  H2504 
0          10         20         30         40         50         60         70         80          90         100 


-100 


/ 

Fft  C.° 
-550-  288 

-500=  260 

.  iCA  -  pT? 

/ 

/  \ 

/    / 

y 

{    \ 

/    ,' 

^^ 

/ 

) 

i 

X 

/ 

/ 

\    ; 

\ 

/ 

/ 

\ 

\ 

/ 

/  ^ 

\ 

-400-  204 
-350=  J77 

300=  149 
-  ?t;n=  i?i 

\ 

>*v 

2 

! 

\ 

/?J 

\ 

^ 

V 

/ 

\ 

A0' 

Q 

\ 

/ 

V 

V 

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/$' 

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// 

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r 

3 

t 

i  ' 

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FIG.  78.— Chart  Showing  Freezing-  and  Boiling-points  of  Sulphuric  Acid  of  Varying 

Concentration. 

1  Ninety-three  thousand  pounds  of  sulphuric  acid,  with  an  exposed  surface  of  1260 
sq.  ft.  and  depth  of  10  in.,  had  decreased  in  strength  from  86  p?r  cent  to  52.12  per  cent 
H"2iSO4,  after  standing  in  a  lead  pan,  protected  from  the  rain,  for  42  days  (Sept.  9th 
to  Oct.  21st,  1916).  Air  was  bubbled  through  a  two-liter  sample  of  this  acid  for  seven 
consecutive  days,  when  the  solution  was  tested  and  found  to  contain  52.18  per  cent 
H2SO4.  The  average  temperature  of  the  laboratory  was  74°  F.,  the  average  vapor  of 
the  air  (7  tests)  was  0.2223  gram  H2O  per  standard  cubic  foot.  The  average  humidity 
for  September  and  October  \v:is  (is  per  cent;  the  average  temperature  62°  F.  The 
average  humidity  for  the  past  33  years  was  72  per  cent;  average  temperature  57°  F. 


ACIDS  503 

about  1.4200  (42.7°  Be*.).  The  acid  is  well  mixed  and  poured  into  small  clean  and 
dry  glass-stoppered  sample  bottles  of  about  200-cc.  capacity.  The  bottles  are 
carefully  sealed  and  placed  aside  for  use  as  desired.  To  determine  the  exact 
strength  of  this  standard  acid  a  portion  is  standardized  against  the  sodium  car- 
bonate, prepared  according  to  directions  given. 

Method  of  Standardization.  Procedure.  A  catch  weight  of  about  10  grams 
of  the  acid  is  weighed  out  in  a  weighing  bottle  or  100-cc.  beaker  (10  cc.  =  approxi- 
mately 13  grams)  and  placed  aside  for  titration.  The  amount  of  sulphuric  acid  in 
the  sample  (weight  of  sample  multiplied  by  per  cent  divided  by  100)  is  neutralized 
by  1.0808  times  its  weight  of  sodium  carbonate.  As  an  excess  of  acid  is  necessary 
to  drive  out  all  the  carbonic  acid  the  following  formula  is  used — (grams  H_S04 
-0.05)  X  1.0808  =  weight  of  Na2C03  required. 

The  required  amount  of  sodium  carbonate  is  weighed  and  transferred  to  a 
600-cc.  Erlenmeyer  flask  and  100  cc.  of  water  added.  The  acid  is  carefully  poured 
into  the  flask  and  the  rinsings  of  the  weighing  bottle  or  beaker  added.  The  solu- 
tion is  boiled  for  15  minutes  to  expel  CO  .  A  small  filtering  funnel  inserted  in  the 
neck  of  the  flask  prevents  loss  during  the  boiling  of  the  acid  and  carbonate  mixture. 
The  excess  of  acid  is  titrated  with  N/5  NaOH,  using  phenolphthalein  indicator, 
the  caustic  being  added  drop  by  drop  until  a  faint  permanent  pink  color  is  obtained. 

(The  sulphuric  equivalent  to  the  NaOH  added)  +  (weight  of  Na2C03X  0.9252) 
=  weight  of  pure  H2S04  present  in  the  sample. 

NOTES.  COo-free  water  should  be  taken  in  all  titrations  with  phenolphthalein. 
The  indicator  contains  1  gram  of  the  compound  per  liter  of  95%  alcohol.  One  cc.  of 
indicator  of  this  strength  is  required  for  each  titration. 

Results  should  agree  to  within  0.05%. 

The  temperature  of  the  acid  should  be  observed  at  the  time  of  standardization  and 
this  noted  with  results  on  the  bottles  containing  the  standard  samples.  The  coefficient 
of  expansion  is  .00016+  per  degree  F.  risen  in  temperature  or  .000293  per  degree  C.  per 
cc.  of  solution. 

Normal  Sulphuric  acid1  contains  49.043  grams  of  H2S04  per  liter  of  solution. 
To  make  a  liter  of  the  normal  acid  the  amount  of  the  standard  acid  required  is 

100x49.043 

calculated   by   the   formula    -  ^   . — - — -^—7  =  grams   standard  acid 

per  cent  H2S04  in  standard 

necessary.  The  acid  is  weighed  out  in  a  small  beaker,  a  slight  excess  being  taken 
(0.1  gram) .  The  acid  is  washed  into  a  liter  flask  and  made  to  volume.  An  aliquot 
portion  is  standardized  against  the  standard  sodium  carbonate.  The  solution 
may  now  be  adjusted  to  the  exact  strength  required. 

Example. l  If  25  cc.  of  the  acid  is  found  to  contain  1 .25  grams  H2S04  we  find  the 
amount  of  dilution  required  as  follows:  25  cc.  of  N/l  H2S04  should  contain  1.226075 

25  X 1  25 

grams,  therefore  1.226075  :  25  ::  1.25  :  x,  and  x  =     oogn--.    Then  x  minus  25  =the 

1 . 226075 

amount  of  water  required  for  25  cc.  Total  dilution  =  dilution  for  25  multiplied 
by  the  volume  of  acid  remaining  in  the  flask  divided  by  25  =  cc.  water  required 
to  make  a  normal  acid  solution. 

Fifth  normal  and  tenth  normal  acids1  may  be  prepared  by  diluting  the 
normal  acid  to  five  or  ten  volumes  as  the  case  requires. 

Gravimetric  Methods.  Precipitation  as  BaSQ*.  Sulphuric  acid  may  be 
standardized  by  precipitating  as  BaS04  according  to  the  procedure  given  for  sul- 
phur. BaS04X0.4202=H2S04. 

1  See  formulae  on  page  525. 


504  ACIDS 

Determination  as  (NH4)2SO4.  To  10  cc.  of  the  acid  diluted  to  50  cc.  in  a  large 
platinum  dish  is  added  NH4OH  until  the  acid  is  neutralized  and  a  faint  odor  of 
ammonia  is  perceptible.  The  solution  is  evaporated  to  dryness  on  the  water  bath 
and  dried  at  100°  C.  for  half  an  hour.  The  residue  is  weighed  as  (NH4)2S04. 
(NH4)2S04X0.7422=gram  H2S04. 


Standard  Hydrochloric  Acid 

This  acid  is  occasionally  preferred  by  chemists  to  sulphuric  acid  as  a  standard. 
At  the  constant  boiling-point,  with  pressure  of  760  mm.,  hydrochloric  acid  has  a 
definite  composition  of  20.242%  HC1.  For  every  10  mm.  increase  in  pressure  the 
percentage  drops  .024  and  for  every  10  mm.  decrease  in  pressure  the  percentage 
rises  .024%  HC1.  Advantage  is  taken  of  this  fact  in  the  preparation  of  standard 
hydrochloric  acid.  Strong,  pure  HC1  is  distilled,  the  first  25  or  30  cc.  being 
rejected.  The  distillate  is  bottled  in  200-cc.  glass-stoppered  bottles  and  sealed,  a 
portion  being  reserved  for  standardization.  The  acid  is  best  standardized  against 
sodium  carbonate,  using  the  formula,  Weight  of  HC1  weighed  for  analysis  minus 
0.05)  X 1 .4533  =  Na2C03  required.  As  in  case  of  H2S04  the  Na2C03  is  weighed  out, 
placed  in  an  Erlenmeyer  flask  with  the  acid  and  boiled  to  expel  C02.  The  excess  of 
HC1  is  titrated  with  standard  caustic.  N/5  NaOH  =0.0072836  gram  HC1  per  cc. 

The  exact  weight  of  Na2C03X0.6881  =HC1.  To  this  add  HC1  obtained  by 
NaOH  titration  =  total  HC1  in  the  sample  taken. 

The  exact  amount  of  HC1  being  known,  normal  acid  containing  36.468  grams 
HC1  per  liter  may  be  made,  and  by  diluting  further,  fifth  normal  and  tenth  normal 
acids  obtained.1 

Gravimetric  Determination  of  Hydrochloric  Acid  by  Precipitation  as  AgCl. 
Hydrochloric  acid  may  be  standardized  by  precipitation  with  silver  nitrate 
solution  by  the  procedure  for  determination  of  chlorine.  AgClX  0.2544  =HC1. 
It  is  advisable  to  heat  the  sample,  diluted  to  a  convenient  volume,  and  add  the 
hot  silver  nitrate  in  slight  excess  of  that  required  by  HC1,  the  amount  of  the 
reagent  being  calculated,  e.g.,  mol.  wt.  HC1  :  mol.  wt.  AgN03::Wt.  HC1  in 
sample  :  x. 


Benzoic  Acid  Standard 

Benzoic  acid  may  be  obtained  in  exceedingly  pure  form  by  melting  the  resub- 
limed  acid  in  a  covered  platinum  dish  in  a  constant-temperature  oven,  at  a  temper- 
ature of  140°  C.  The  acid  is  poured  into  test-tubes,  cooled,  and  the  sticks  bottled 
for  use.  The  acid  does  not  take  up  moisture  to  any  appreciable  extent,  even 
when  exposed  to  the  air  for  some  time,  so  that  it  may  be  weighed  without 
danger  of  absorption  of  moisture. 

Standard  Caustic  Solution 

Standard  normal  sodium  hydroxide  is  made  by  dissolving  approximately  50 
grams  of  NaOH  sticks  with  1  to  2  grams  of  Ba(OH)*  in  200  to  300  cc.  of  water  and 

1  See  formulae  on  page  525. 


ACIDS 


505 


diluting  to  1000  cc.  The  caustic  is  standardized  against  normal  H2S04,  using 
phenolphthalein  indicator.  The  solution  is  adjusted  to  the  exact  strength  desired 
by  addition  of  distilled  water. 

NOTE.  The  addition  of  Ba(OH)2  is 
made  to  precipitate  the  carbonate  in  the 
caustic,  as  this  would  interfere  with  titra- 
tions  in  presence  of  phenolphthalein.  As 
the  presence  of  barium  would  produce  a 
cloudiness  with  H^SCX  it  is  advisable  to 
add  only  an  amount  sufficient  to  precipi- 
tate the  carbonate. 

STANDARD    BURETTES1 

For  accurate  titration  of  acids  or 
alkalies  it  is  advisable  to  have  a  titra- 
tion of  75  to  100  cc.  Since  the  straight 
100-cc.  burette  if  graduated  to  twenti- 
eths of  a  cc.  would  be  too  long  for  con- 
venient handling,  the  chamber  burette 
is  used.  The  chamber  located  in  the 
upper  portion  of  the  apparatus  holds 
75  cc.,  the  lower  portion  drawn  out  into 
a  uniform-bore  tube  is  graduated  in 
twentieths  of  a  cc.  Each  tenth  of  a 
cc.  has  a  mark  passing  entirely  around 
the  tube  so  that  there  will  be  no  error 
in  reading,  the  eye  being  held  so  that 
the  mark  appears  to  be  a  straight  line 
drawn  across  the  tube.  The  burette  is 
enclosed  in  a  large  tube  filled  with  dis- 
tilled water  and  carrying  a  thermom- 
eter. The  burette  is  connected,  by 
means  of  an  arm  at  the  base,  with  a 
reservoir  of  standard  acid.  The  cut, 
Fig.  79,  shows  the  apparatus  connected 
ready  for  use. 

If  vapor  is  lost  from  the  standard  re- 
agents and  this  replaced  by  dry  air,  as 
in  the  common  practice,  the  solution 
gradually  changes  in  strength.  A  sim-  E 
pie  and  ingenious  device,  designed  by 
H.  W.  Herig  (Gen.  Chem.  Co.),  is  shown 
at  the  top  of  Fig.  79,  which  overcomes  this  FIG.  79. 

difficulty.       The    air     drawn    into    the 

reagent  bottle  is  purified  and  saturated  with  moisture  by  passing  it  through  sodium 
hydroxide.  A  mercury  valve  relieves  the  pressure  if  expansion  of  air  in  the  reagent 
bottle  occurs  due  to  rise  of  temperature. 

1  The  chamber  burette  was  designed  at  the  Laurel  Hill  Laboratory,  General  Chem- 
ical Company. 


Chamber 
Burette 


•Water 
Jacket 


506 


ACIDS 


METHODS  OF  WEIGHING   ACIDS 
Dilute  Acids  Nonvolatile  under  Ordinary  Conditions 

Dilute  acids  may  be  weighed  directly  in  a  beaker,  weighing  bottle  or  ordinary 
pipette  (see  directions  given  later)  by  measuring  out  the  approximate  amount 
desired.  Since  a  burette  reading  from  75-cc.  to  100-cc.  should  be  used  for  this 
work  it  will  be  necessary  to  take  such  an  amount  of  the  acid  as  will  require  a 
titration  between  these  extremes.  This  may  be  accomplished  by  taking  the 
specific  gravity  of  the  acid  and  referring  to  the  table  for  the  approximate  strength. 
From  this  the  volume  necessary  may  readily  be  calculated. 

Example.  The  case  will  be  taken  where  a  75-cc.  to  100-cc.  burette  is  being  used 
and  the  titration  is  to  be  made  with  normal  caustic  solution,  the  acid  titrated  is 
sulphuric  acid.  The  capacity  of  the  burette  is  75X0.049=3.675  grams  H2S04  to 
100X0.049=4.9  grams  H2S04.  (For  HC1  the  capacity  would  be  2.74  to  3.65 
grams  HC1  and  for  HN03  it  would  be  4.73  to  6.3  grams  HN03). 

Suppose  the  sulphuric  acid  has  a  sp.gr.  of  1.1600.  From  the  table  for  H2S04  we 
find  that  this  acid  is  22.25%  H2S04,  then  1  cc.  contains  1.16X22.25  divided  by 
100  =0.2581  gram  H2S04.  Since  the  capacity  of  the  burette  is  3.675  to  4.9  grams 

3  675        4  9 
H2S04,  we  must  weigh  between    '        to  -     -  grams  of  the  acid;  to  get  this  we 


,      . ,   .  .     3.675 
should  take  — -  —  to 


4.9 


.2225       .2225 
cc.,  that  is  to  say,  14.5  to  18.5  cc.  of  the  acid, 


.2581         .2581 
which  will  weigh  16. 8 'grams  to  21 .5  grams. 

Weighing  Strong  Acids,  Fuming  or  Volatile  under  Ordinary 

Conditions 

The  acid  must  be  confined  during  weighing  and  until  it  is  mixed  with  water 
or  standard  caustic.  The  best  forms  of  apparatus  include  the  follow- 
ing: 

Lunge-Ray  Pipette.  The  pipette  is  shown  in  Fig.  80.  Two 
glass  stop-cocks  confine  the  acid  in  a  bulb.  The  lower  part  of  the 
pipette  is  protected  by  a  ground-on  test-tube.  The  dry  pipette  is 
weighed.  Cock  2  is  closed  and  1  opened  and  a  vacuum  produced 
in  the  bulb  by  applying  suction  at  the  upper  end  of  pipette  and 
closing  stop-cock  1  with  suction  still  on.  The  sample  may  now  be 
vj^  w  drawn  into  the  pipette  by  immersing  the  lower  end  in  the  sample 
(jf  and  opening  the  stop-cock  2,  the  vacuum  producing  the  suction. 
The  increased  weight  =  acid  drawn  in.  The  pipette  is  emptied  by 
running  the  acid  under  water. 

Dely  Weighing  Tube.1  This  form  of  weighing  tube  has  proven 
to  be  of  exceptional  value,  to  the  busy  works-chemist,  in  the  analy- 
sis of  oleum  and  mixed  acids.  Both  speed  and  accuracy  are  gained 
by  its  use.  The  apparatus,  shown  in  the  cut  on  page  507,  consists 
of  a  long  glass  tube  of  small  bore,  wound  in  a  spiral  coil.  Fig.  SI. 

The  sample  of  acid  is  drawn  into  the  weighed  coil  by  applying 
suction  through  a  rubber  tube  attached  to  A  and  drawing  in 
the  required  amount  of  acid,  a  mark,  ascertained  by  a  previous  run 
being  made  to  indicate  the  point  to  which  the  acid  is  drawn.  The 
1  J.  G.  Dely,  Chemist,  Gen.  Chem.  Co. 


FIG.  80. 

Lunge-Ray 

Pipette. 


ACIDS 


507 


FIG.  81. 
Dely  Weighing  Tube  in  Operation. 


tip   B   is   carefully  wiped   off    with  tissue  paper   and   the   tube   and   sample 

weighed.    The  weight  of  the  tube  deducted  gives  the  weight  of  the  sample. 
The  apparatus  is  now  inclined  so  that  the  acid  runs  back   into  the  crook  at 

C  to  a  point  marked  on  the  wall  of  the  tube,  in  order  to  expel  as  much  air  as 

possible  from  this  end.     A  rubber  tube  filled 

with  water  is  attached  to  A,  the  other  end 

of  the  rubber  tube  being  connected  to  a  bottle 

containing  distilled  water.    A  glass  bead,  such 

as  is  used   in    rubber-tipped  burettes,  fitting 

snugly  in  this  tube,  regulates  the  flow  of  water. 

The  Dely  tube  is  now  inverted,  the  tip  being 

immersed   in  150  cc.  to  200   cc.   of  distilled 

water  in  a  4-in.  casserole — Fig.  81.    By  pressing 

gently  on  the  bead,  water  is  slowly  admitted 

in  the  tube,  forcing  the  acid  before  it.     The 

acid  and  water  are  separated  by  a  bubble  of 

air.     Before  forcing  out  the  last  half-inch  of 

acid,  the  tube  connected  to  the  water  supply 

is  disconnected  and  the  weak  acid  from  the 

casserole  drawn  back  into  the  Dely  tube  for 

two   or  three  inches,  then  again   the  acid  is 

almost  entirely  expelled  by  water   from  the 

reservoir  and  the  procedure  repeated.     This  is  to  absorb  the  S03  gas  that  invari- 
ably is  present  in  the  bubble  of  air  above  mentioned,  which  would  be  lost  if 

forced  out  directly  by  the  water  column.     In  order  to  facilitate  this  last  step  it 

is  well  to  have  a  short  rubber  tube  attached  to  the  Dely  tube,  and  a  glass  tip  in 

the  tube  connected  with  the  reservoir  of  water.    The  acid  in  the  casserole,  upon 

washing  out  the  Dely  tube,  is  titrated  with  standard  caustic  according  to  the 

procedure  for  titration  of  acids. 

The  tube  is  dried  after  washing  with  alcohol,  followed  by  ether,  by  heating 

on  an  asbestos  mat  on  a  hot  plate,  dry  air  being  aspirated  through. 

Snake  Weighing  Tube.  The  snake  tube  is  a  simple  device  that  may  be  easily 
made  by  an  amateur  glass-blower.  It  is  made  out  of  a  glass  tube 
8-10  ins.  long,  slightly  thinner  than  a  lead  pencil.  One  end 
of  the  tube  is  drawn  out  to  capillarity.  The  tube  has  a  double 
bend,  as  shown  in  the  illustration.  It  is  so  made  that  it  rests 
on  the  double  bend  with  the  ends  inclined  upward  to  prevent  the 
outflow  of  the  acid.  Fig.  82. 

The  tube  is  dried  with  alcohol,  ether  and  air  treatment,  as  in 
case  of  the  Dely  tube.  After  weighing  the  empty  tube,  acid  is 
drawn  into  it  by  suction  through  an  attached  rubber  tube.  The 
capillary  end  that  has  dipped  into  the  sample  is  wiped  dry  with 
tissue  paper.  The  acid  and  tube  are  weighed  and  the  acid  esti- 
mated by  difference. 

The  acid  is  run  into  150  cc.  of  water  in  a  casserole,  the  flow 
being  regulated  by  the  index  finger  pressed  against  the  larger  end 
of  the  tube.  With  careful  regulation  of  the  flow,  practically  no 
bumping  occurs.  With  a  small  capillary  opening  it  is  not  neces- 
sary to  place  the  finger  over  the  larger  end  of  the  tube  as  the 

acid  flow  will  be  slow.   The  tube  should  be  kept  in  motion  to  prevent  bumping  from 


FIG.  82. 
Snake  Tube. 


508 


ACIDS 


Horns  for  Suspending 
burette 


Scotts 
Modification 


overheating  any  one  portion.  Kicking  back  of  the  acid  indicates  that  the  capil- 
lary end  of  the  tube  is  too  large.  When  the  contents  of  the  tube  have  run  out, 
the  tube  is  rinsed  by  sucking  up  some  acid  from  the  casserole  and  allowing  it 
to  run  out,  repeating  several  times.  Suction  may  be  applied  by  means  of  a 
rubber  bulb  attached  to  the  tube.  The  acid  is  now  titrated  with  standard  caustic, 
using  phenol phthalein  indicator. 

Blay-Burkhard  Graduated  Weighing  Burette.  This  apparatus,  designed  by  V. 

L.  Blay  and  W.  E.  Burkhard,  General  Chem- 
ical Company,  is  used  for  weighing  acids  or 
other  liquids.  The  form  for  general  use  is 
shown  in  Fig.  83.  The  burette  is  graduated 
in  half  cc.  divisions,  from  0  to  20  cc.  An 
apparatus  half  this  size  is  used  for  oleum, 
where  a  2-cc.  sample  is  sufficient  for  a  deter- 
mination. For  the  purpose  of  running  the 
sample  under  water  a  capillary  tube  (E, 
Fig.  83)  with  ground  joint,  is  attached  to 
the  burette.  This  tube  is  placed  in  the  solu- 
tion during  titration.  The  burette  is  pro- 
vided with  a  glass  vented  stopper  (A)  on 
the  top,  and  a  glass  cap  for  the  tip,  both 
having  ground  joints,  to  prevent  escape  of 
fumes  from  the  sample. 

The  Editor  has  modified  the  apparatus 
by  replacing  the  fragile  cap  (A}  by  a  tube 
stopper  with  capillary  vent  (see  A',  Fig.  83). 
The  vent  to  the  air  is  opened  or  closed  by  a 
slight  turn  of  this  stopper.  By  means  of  this 
tube  acid  may  be  drawn  into  the  burette 
according  to  the  Lunge-Ray  pipette  pro- 
cedure. With  these  burettes  a  man  can 
control  his  work  very  accurately  and  save  a 
great  amount  of  time,  both  in  weighing  and 
manipulation. 


Cap/ltary 
Tube  adaptor 
for  Fuming 
Ada's 


FIG.  83.— Blay-Burkhard  Graduated 
Weighing  Burette. 


In  the  analysis  of  strong  oleum,  about  50  grams  of  neutral  Glauber  salt  are 
placed  in  a  casserole  containing  water,  and  the  fuming  acid  allowed  to  flow  under 
the  undissolved  salt.  The  violent  reaction  of  the  acid  with  water  is  thus  avoided. 
The  tube  E,  Fig.  83,  should  be  made  of  fused  silica. 

The  glass-bulb  method  is  still  used  for  analysis  of  strong  oleum.  The  acid 
weighed  in  a  sealed  tube  of  known  weight  is  mixed  with  water  by  breaking  the 
bulb  in  a  stoppered  bottle  containing  water,  the  acid  is  cooled  and  titrated  as  usual. 


Titration  of  Acids  and  Alkalies 

In  the  acid  titration  the  sample  is  conveniently  titrated  in  a  white  porcelain 
casserole.  This  gives  a  white  background  that  enables  the  analyst  to  see  the  end- 
point.  The  caustic  is  run  into  the  acid,  to  within  a  few  cc.  of  the  end-point, 
rapidly  and  then  cautiously  to  a  faint  change  of  color — faint  pink  with  phenol- 
phthalein  or  an  orange-yellow  with  methyl-orange.  Phenolphthalein  is  generally 
preferred  to  acid  titrations.  C02-free  caustic  and  water  should  always  be  used. 


ACIDS  509 

ANALYSIS  OF   MURIATIC  ACID 

(Commercial  Hydrochloric  Acid) 

4 

Total  Acidity  and  Hydrochloric  Acid 

The  usual  titration  with  standard  caustic  gives  the  total  acidity,  including, 
in  addition  to  hydrochloric  acid,  nitric  and  sulphuric  acids  which  may  occur  in  the 
commercial  product.  The  acidity  due  to  these  acids  is  deducted  from  the  total 
acidity  to  find  the  actual  HC1  in  the  muriatic  acid. 

A  catch  weight,  10  to  15  grams  of  the  acid,  is  weighed  in  a  weighing  bottle,  or  a 
large  snake  tube,  or  the  Dely  tube,  as  in  case  of  oleum  analysis,  and  the  acid  allowed 
to  mix  with  water  in  a  casserole;  methyl-orange  indicator  is  added  and  the  acid 
titrated  with  standard  normal  caustic  solution,  the  red  color  fading  to  a  lemon- 
yellow.  A  fraction  of  a  drop  of  the  alkali  will  cause  the  change  when  the  end-point 
has  been  reached. 

One  cc.  N/l  NaOH  =0.03647  g.  HC1. 

NOTE.  Hydrochloric  acid  may  be  determined  gravimetrically  by  precipitating 
the  chloride  with  silver  nitrate — HCl+AgNO3=AgCl+HNO3,  or  by  the  volumetric 
methods  for  the  determination  of  chlorine.  See  Chlorine. 

Determination  of  Impurities    in  Commercial  Hydrochloric  Acid. 

Free  Chlorine 

Five  cc.  of  the  acid  are  diluted  to  10  cc.,  about  5  cc.  of  fresh  starch  solution 
added  and  a  few  drops  of  5%  KI  solution  together  with  about  1  cc.  of  dilute 
H2S04.  A  blue  color  indicates  free  chlorine.  This  color  may  be  matched  in  a 
Nessler  tube  with  a  standard.  It  is  possible  to  determine  .0001%  chlorine  on  a 
5-cc.  sample. 

Nitric  Acid  or  Nitrates  in  Hydrochloric  Acid 

About  5  cc.  of  the  hydrochloric  acid  is  cautiously  added  to  75  cc.  of  95% 
H2S04,  the  HC1  being  introduced  under  the  surface  of  the  sulphuric  acid.  The 
nitric  acid  may  now  be  titrated  with  standard  ferrous  sulphate  by  the  procedure 
for  the  direct  determination  of  nitric  acid  and  nitrates.  (Method  of  Scott  and 
Bowman.)  The  ferrous  sulphate  test  for  nitric  is  delicate.  Traces  of  nitric  acid 
produce  a  pink  coloration;  larger  amounts  a  reddish  brown  to  dark  brown.  The 
color  is  permanent  when  an  excess  of  ferrous  sulphate  has  been  added.  See 
page  515. 

Sulphuric  Acid  and  Sulphates  in  Hydrochloric  Acid 

Free  H2S04.  Fifty  cc.  of  the  sample  is  evaporated  in  a  platinum  dish  (steam 
bath)  to  dryness  or  until  the  HC1  has  been  expelled.  A  few  drops  of  water  are 
added  and  the  material  again  taken  to  dryness  (steam  bath).  The  residue  is 
taken  up  with  water  and  titrated  with  N/10  NaOH,  using  methyl-orange  indica- 
tor. One  cc.  =0.0049043  gram  H2S04. 

Total  Sulphates.  Fifty  cc.  of  the  muriatic  acid  is  evaporated  to  about  5  to  10  cc. 
and  then  diluted  to  about  200  cc.  and  heated  to  boiling.  Total  S03  is  now  precipi- 
tated by  adding  BaCl2  solution  as  in  case  of  determination  of  total  sulphur.  The 
precipitated  BaS04  includes  the  free  H2S04  and  the  combined  S03.  BaS04  X  0.4202 
=  HiS04. 


510  ACIDS 


Arsenic  in  Hydrochloric  Acid 

Commercial  muriatic  acid  may  contain  arsenic.  This  is  best  determined  by  the 
Gutzeit  Method  given  in  detail  under  Arsenic.  10  cc.  of  sample  is  usually  suffi- 
cient for  this  determination.  If  much  arsenic  is  present  the  distillation  method 
may  be  followed,  using  a  25  to  50-cc.  sample.  The  distillate  is  titrated  with  stand- 
ard iodine  according  to  procedure  given  for  arsenic  by  the  iodine  titration, 
page  39. 

Barium  Chloride  in  Hydrochloric  Acid 

Fifty  cc.  is  evaporated  to  dryness  and  then  over  a  low  flame  to  expel  S03.  The 
residue  is  taken  up  with  1  cc.  of  1  :  1  HC1  and  50  cc.  of  water.  1  cc.  H2S04  is 
added  and  the  precipitated  BaS04  filtered  off  and  weighed.  If  silica  is  present 
in  the  sample  its  weight  should  be  deducted.  BaS04X 0.8923  =BaCl2. 

Total  Solids  and  Silica 

One  hundred  cc.  of  the  HC1  in  a  platinum  dish  is  evaporated  to  dryness  and  the 
residue  ignited  and  weighed.  5  cc.  of  HF  is  added  with  a  few  drops  of  H2S04 
and  the  solution  again  evaporated  and  ignited.  The  first  weight  =  total  solids. 
The  loss  of  weight  in  the  second  ignition  =Si02. 


ANALYSIS   OF  HYDROFLUORIC  ACID 

The  following  constituents — hydrofluosilicic  sulphuric  and  sulphurous  acids — 
commonly  occurring  with  hydrofluoric  acid,  are  determined  in  the  analysis, 
along  with  the  hydrofluoric  acid,  by  titration.  Generally  the  acid  contains  a 
slight  residue  upon  ignition.  The  titrations  are  made  in  presence  of  KN03,  first 
ice  cold,  and  then  completed  at  80°  C.  or  more.  The  cold  titration  gives  the 
hydrofluoric,  sulphuric  and  sulphurous  acids  and  one-third  of  the  hydrofluosilicic 
acid  and  upon  heating  the  titration  gives  the  remaining  two-thirds  of  the  H2SiF6, 
the  following  reactions  taking  place.  Titration  cold,  H2SiF6H-2KN03=K2SiF6 
+2HN03(=£  H2SiF6).  The  liberated  2HN03  requires  2NaOH.  Titration  hot, 
K2SiF4+4NaOH  =4NaF+2KF+Si02+2H20(f  H2SiF6). 

The  sulphuric  acid  is  determined  by  titration  with  NaOH,  upon  expulsion  of 
the  accompanying  more  volatile  acids.  Sulphurous  acid  is  determined  by  titration 
with  standard  iodine. 

Special  Apparatus.  Chamber  burette  graduated  from  75  to  100  cc.  in  -£$  cc. 
as  described  under  the  determination  of  sulphuric  acid,  oleum,  mixed  acids,  etc. 

Platinum  weighing  tube.  Length  about  5  cm.,  diameter  1.4  cm.  The  tube 
fitted  with  a  platinum  cap  with  a  loop  top  to  facilitate  removal  by  means  of  a 
platinum  wire. 

Lead  thief  for  sampling. 

Special  Reagents. 

Normal  solution  of  NaOH.     1  cc.  =  .04903  gram  H2S04. 

N/10  Iodine  solution.     I  cc.  =  .0041  gram  H2S03. 

Phenolphthalein  indicator,  and  Starch  solution. 


ACIDS  511 


Details  of  Procedure.    Total  Acidity  and  Hydrofluosilicic  Acid 

A  catch  weight  of  the  acid  is  taken  by  pouring  the  acid  by  means  of  the  thief 
or  directly  from  the  paraffine  bottle  into  the  platinum  weighing  bottle,  such  a 
weight  being  taken  as  will  require  a  titration  of  from  75  to  100  cc.  of  the  normal 
caustic  solution.  (This  may  be  judged  by  a  preliminary  run  if  the  approximate 
value  is  not  known.) 

About  10  cc.  of  a  saturated  solution  of  KN03  is  poured  into  a  large  platinum 
dish  (capacity  about  125  cc.),  and  chipped  ice  added.  About  50  cc.  of  N/l  NaOH 
solution  is  run  in  from  a  burette  and  three  drops  of  the  strong  phenolphthalein 
added.  The  platinum  weighing  bottle  containing  the  sample  is  inverted  beneath 
the  surface  of  the  caustic,  the  cover  cautiously  removed  from  the  bottle  by  means 
of  a  heavy  platinum  wire,  so  as  to  allow  the  acid  to  mix  very  gradually  with  the 
standard  NaOH  (rapid  addition  is  apt  to  cause  loss  of  acid  by  fumes).  Standard 
N/l  NaOH  is  added  from  the  burette  until  the  first  permanent  pink  color  is 
obtained.  (The  end-point  will  be  uncertain  and  fading  unless  the  solution  is  kept 

cold— 0°G.)     The   reading   of   the   burette   is  noted — total  — r=A. 

Wt.  of  sample 

The  dish  is  now  placed  on  a  hot  plate  and  the  solution  warmed  to  about 
80°  C.  and  the  titration  completed  with  the  N/l  NaOH  solution  to  a  permanent 
pink.  Additional  cc.  required  divided  by  weight  of  sample  =B,  (See  calculation 
at  close  of  procedure.) 

Sulphuric  Acid  in  Hydrofluoric  Acid 

About  5  grams  of  the  sample  are  weighed  in  the  platinum  capsule  and  trans- 
ferred to  a  large  platinum  dish,  the  capsule  being  rinsed  out  into  the  dish  with 
water.  The  solution  is  evaporated  on  the  steam  bath  to  small  volume  (the 
evaporation  is  assisted  by  passing  a  hot  current  of  pure  dry  air  over  the  sample, 
see  procedure  for  oleum),  a  few  drops  of  water  are  added  and  the  evaporation 
repeated;  no  odor  should  be  perceptible,  all  the  hydrofluoric,  hydrofluosilicic  and 
sulphurous  acids  being  expelled.  The  sulphuric  acid  is  cooled,  taken  up  with 
100  cc.  of  C02-free  water,  three  drops  of  strong  phenolphthalein  added  and  the 
acid  titrated  with  N/l  NaOH  solution  in  a  50-cc.  burette.  The  cc.  titration 
divided  by  the  weight  of  the  sample  is  noted  as  C.  (See  calculations  at  the 
close  of  the  procedure.) 

Sulphurous  Acid  in  Hydrofluoric  Acid 

Ten  grams  of  the  sample  are  weighed  in  a  tared  platinum  capsule  with  cover 
and  washed  into  a  large  platinum  dish  with  about  75  cc.  of  water.  N/10  Iodine 
solution  is  added  to  a  faint  yellow.  The  end  point  is  made  more  distinct  by  addi- 
tion of  a  little  starch  solution  near  the  end  of  the  reaction. 

One  cc.  of  N/10  I  =0.0041  g.  H2S03.    cc.  N/10  I^wt.  of  sample  =D. 
Calculation  of  Results. 
Factors.  H2S04X0.4904  =H2SiF6. 

H2S04X0.4080=HF. 
One  cc.  N/10  1=0.0041  g.  H2SO* 


512  ACIDS 

cc.  NaOH  for  total  acidity  (cold) 

Symbols.  A= ...  .  ,  .    ,  — . 

Weight  of  sample 

_     cc.  of  NaOH  additional  for  H2SiF6  (hot) 
15= 


c= 

D  = 


Weight  of  sample 

cc.  NaOH  for  H2S04 
Weight  of  sample 

cc.  N/10  iodine. 


Weight  of  sample' 


Formulae  for  Calculation.    If  E=  value  of  1  cc.  of  the  standard  N/l  caustic 
in  terms  of  H2S04  then 

Per  cent  HF  =  f  A-  ?  -C  )  XEX0.408X100-0.2D: 


Per  cent  H2SiF6=-BXEX0.4904X100; 
2> 

Per  cent  H2S04=CXEX100; 
Per  cent  H2S03=DX  0.0041X100. 

Residue.  This  is  determined  by  evaporation  of  15  to  20  grams  of  the  acid 
in  a  platinum  dish,  and  gentle  ignition  of  the  dry  residue. 

NOTES  AND  PRECAUTIONS.  Weighings  should  be  made  quickly  in  covered  platinum 
weighing  bottles. 

The  end-point  in  the  cold  titration  is  the  first  pink  that  persists  for  15  seconds. 

It  is  advisable  to  weigh  out  the  sample  for  the  sulphuric  acid  determination  first 
and  start  the  evaporation  to  facilitate  more  rapid  results. 

Iodine  is  preferred  to  permanganate  for  titration  of  H2SO|  as  the  latter  also  titrates 
organic  matter  that  is  apt  to  occur  in  the  acid. 

The  residue  contains  Fe208,  A120|,  CaSO4,  CaF,  Alkalies,  etc. 


COMPLETE  ANALYSIS  OF  NITRIC  ACID 

The  acidity  of  nitric  acid  obtained  by  titration  with  standard  caustic  may  be 
due  not  only  to  HN03  but  to  impurities  H2S04,  HC1  and  lower  oxides  of  nitrogen, 
hence  for  extremely  accurate  analysis  it  is  essential  to  look  for  these  impurities 
and  make  allowances  accordingly  if  they  are  found  to  be  present.  Nitric  acid  may 
be  determined  directly  by  titration  with  ferrous  sulphate  according  to  the  pro- 
cedure given  in  detail,  page  515;  this  titration  will  include  combined  nitrates  as 
well  as  the  free  acid,  whereas  the  titration  with  caustic  includes  only  free  acids. 
In  addition  to  the  above-mentioned  impurities,  commercial  nitric  acid  frequently 
contains  free  chlorine,  chlorides,  chlorates,  iodine,  iodides,  iodates,  silica,  and 
suspended  solids;  the  last  is  reported  as  insoluble  residue.  In  an  analysis  of 
nitric  acid  the  impurities,  which  are  known  to  be  injurious  to  the  art  for  which  the 
acid  is  used,  are  looked  for  and  determined  if  present. 


ACIDS  513 


Determination  of  Total  Acidity 

As  in  ease  of  mixed  acids  and,  in  fact,  all  accurate  determinations  of  acids  with 
caustic,  such  an  amount  of  the  sample  should  be  taken  as  will  require  a  titration 
within  the  limits  of  the  standard  chamber  burette — 75  to  100  cc.  For  normal 
caustic  this  would  require  4.726  to  6.3  grams  of  100%  HN03  or  a  fifth  or  tenth  of 
thi  amount  for  N/5  or  N/10  NaOH.  From  the  specific  gravity  of  the  acid  its 
approximate  strength  can  be  obtained  by  referring  to  the  table  for  nitric  acid  and 
calculating  the  volume  and  approximate  weight  required  for  analysis  (see  example 
under  Methods  of  Weighing  Acids — Dilute  Acids — Non- Volatile  under  Ordinary 
Conditions,  page  506). 

The  acid  is  weighed  in  a  weighing  bottle,  or  in  the  Dely  tube  or  Blay-Burk- 
hard  pipette,  if  it  is  a  fuming  acid.  The  titration  is  made  in  a  casserole,  the  acid 
being  mixed  with  150  to  200  cc.  of  C02  free  water  and  titrated  in  presence  of 
phenolphthalein  indicator.  (Methyl-orange  is  destroyed  by  nitrous  acid.)  The 
total  acidity  is  expressed  in  terms  of  H2S04  if  other  acids  are  present. 

cc.N/1  NaOH  X. 049043X100 

— : =  per  cent  H2S04  equivalent.  H2S04  X 1 .285  =  HNOi. 

Weight  of  the  sample 

.    cc.  N/l  NaOH  X 0.063018X100 

Direct  calculation  to  HN03 TT7  .  . — =per  cent  HNO». 

Weight  of  the  sample 

Determination  of  Sulphuric  Acid  in  Nitric  Acid 

About  10  grams  of  the  acid  are  evaporated  to  dryness  on  the  steam  bath.  The 
residue  is  taken  up  with  about  10  cc.  of  water  and  the  evaporation  repeated  until 
free  from  nitric  fumes,  the  residue  finally  diluted  to  100  cc.  and  the  sulphuric  acid 
titrated  with  N/5  NaOH,  using  phenolphthalein  or  methyl-orange  indicator 
Gravimetrically  the  acid  may  be  precipitated  from  a  hot  solution  as  BaS04  by 
addition  of  barium  chloride  reagent  according  to  the  method  for  determining 
sulphur. 

One  cc.  N/5  NaOH  =0.009809  gram  H2S04. 

BaS04X0.4202  =H2S04.  Per  cent  =  100  divided  by  weight  of  sampleXH2S04 
obtained. 

Determination  of  Hydrochloric  Acid  in  Nitric  Acid 

A  5-  to  50-gram  sample  is  taken,  that  is  to  say,  a  sufficient  amount  of  the  acid 
so  that  a  weighable  amount  of  AgCl  may  be  obtained.  The  sample  is  nearly 
neutralized  with  NH4OH  (it  should  be  slightly  acid  with  HN03)  and  a  slight 
excess  of  silver  nitrate  reagent  added  to  the  hot  solution;  the  mixture  is  stirred 
thoroughly,  then  allowed  to  settle  for  one  or  two  hours.  The  AgCl  is  filtered 
through  a  weighed  Gooch  crucible  containing  an  asbestos  mat,  then  washed, 
dried  and  ignited  at  a  low  red  heat.  (See  general  method  for  the  determination  of 
chlorine.) 

Factors.  AgClXO.2474   =C1.    AgCl  X  0.2544  =HC1. 

AgCl  X  0.34212  =  equivalent  H2S04. 
Find  the  per  cent  HC1  and  the  per  cent  equivalent  H2S04. 


514  ACIDS 


Lower  Oxides.     Determined  as  Nitrous  Acid 

For  practical  purposes  the  lower  oxides  of  nitrogen  that  may  be  present  in 
nitric  acid  are  calculated  to  N203  or  HN02.  If  it  is  desired  to  report  these  as  N204 
the  conversion  factor  given  below  may  be  used.  The  lower  oxides  may  be  obtained 
by  titration  with  standard  permanganate,  other  reducing  agents  being  absent. 
In  presence  of  organic  matter  titration  with  standard  iodine  solution  should  be 
made.  (See  general  procedure  for  determination  of  nitrous  acid,  etc.) 

It  makes  but  little  difference  whether  the  permanganate  is  added  to  the  sample 
containing  nitrite  or  the  sample  added  to  a  measured  amount  of  permanganate, 
provided  in  the  first  method  the  titration  be  made  as  rapidly  as  possible  to  prevent 
oxidation  taking  place  due  to  dilution  of  the  sample  with  water.  The  end-point 
in  the  first  procedure  is  quicker  and  sharper. 

Potassium  permanganate  oxidizes  nitrous  acid  to  nitric  according  to  the 
reaction  2KMn04+5HN02+3H2S04  =K2S04+2MnS04+5HN03+3H20.  There- 
fore 1  cc.  of  N/l  KMn04  =0.02351  gram  HN02  or  0.019  gram  N203. 

Twenty-five  cc.  of  the  acid  are  diluted  in  a  casserole  to  about  300  cc.  with  cold 
water,  and  25  cc.  of  dilute  H2S04,  1  :  4  added.  The  solution  is  titrated  imme- 
diately with  N/5  KMn04,  the  reagent  being  added  rapidly  at  first  and  finally 
drop  by  drop  as  the  end-point  is  approached.  The  reaction  near  the  end  is  apt 
to  be  slow,  so  that  time  must  be  allowed  for  complete  oxidation.  The  titration 
is  completed  when  a  pink  color  is  obtained,  that  persists  for  three  minutes. 

cc.  N/5  KMn04X 0.004702=  gram  HN02. 

100 

The  result  multiplied  by  -  — r-  =  per  cent, 

wt.  sample 

HN02X  1.0431  =equivalent  H2S04. 

Nitric  Acid 

From  the  total  acidity  expressed  as  H2S04  is  subtracted  the  acidity  due  to  HC1 
and  HN02  (lower  oxides  of  nitrogen)  expressed  in  terms  of  H2S04.  The  remainder 
is  due  to  nitric  acid,  in  terms  of  sulphuric  acid. 

H2S04X  1.285  =HN03. 

Determination  of  Iodine  in  Nitric  Acid 

Fifty  cc.  of  the  acid  in  an  Erlenmeyer  flask  is  neutralized  with  caustic,  the  mix- 
ture being  cooled  in  running  water  during  the  operation.  The  solution,  poured  into 
a  separatory  funnel,  is  made  acid  with  dilute  H2S04  and  a  few  drops  of  1%  solution 
of  KN02  added,  followed  by  about  25  cc.  of  CS2  or  CC14.  The  mixture  is  shaken 
to  extract  the  free  iodine  and  the  CS2  or  CC14  drawn  off  and  the  extraction  repeated 
by  addition  of  KN02  and  CS2  or  CC14  until  all  the  iodine  has  been  extracted. 
Iodine  present  as  iodide  is  extracted  by  this  method.  To  obtain  the  iodine  from 
iodate,  H2S  water  is  added  and  the  extraction  with  addition  of  NaN02  and  CS2 
repeated. 

The  combined  extracts  are  washed  in  a  separatory  funnel  until  free  of  acid. 
The  iodine  is  now  titrated  with  standard  sodium  thiosulphate  by  adding  25  to 


ACIDS  515 

30  cc.  of  water  together  with  5  cc.  of  1%  sodium  bicarbonate  solution  (10  grams 
NaHC03  per  liter +1  cc.  HC1). 

One  cc.  N/10  Na2S203=  0.01269  gram  I. 
Reactions. 

2HI+2KN02+H2S04=K2S04+2H20+L+2NO; 

2Na2S203+I2  =2NaI+Na2S406. 

Determination  of  Free  Chlorine  in  Nitric  Acid 

When  a  current  of  pure  air  is  passed  into  nitric  acid  containing  free  chlorine 
the  air  blows  out  the  chlorine.  If  air  aspirated  through  a  sample  of  nitric  acid  is 
passed  through  a  solution  of  potassium  iodide  the  free  chlorine  will  displace  the 
iodine.  The  liberated  iodine  may  now  be  titrated  with  standard  sodium  thio- 
sulphate  and  the  equivalent  chlorine  calculated. 

Total  Nonvolatile  Solids 

These  may  be  determined  by  evaporating  a  large  sample  of  100  to  200  cc.  of 
the  nitric  acid  to  dryness.  The  residue  is  heated  gently  to  expel  the  last  traces 
of  nitric  acid  and  then  washed  into  a  platinum  dish,  again  evaporated  to  dryness 
and  ignited  to  a  dull  red  heat.  The  residue  is  due  to  non-volatile  solids. 


FERROUS  SULPHATE  METHOD  FOR  THE  DIRECT  DETERMN 
NATION   OF   NITRIC  ACID1 

Although  the  test  for  nitric  acid  by  ferrous  sulphate  in  presence  of  strong  sul- 
phuric acid  has  long  been  known,  the  reagent  has  not  been  used  for  an  accurate 
quantitative  method  until  F.  C.  Bowman  and  W.  W.  Scott,  General  Chemical 
Company,  developed  the  procedure  herein  given.  Nitric  acid  may  be  determined 
quantitatively  in  arsenic  acid  by  titration  with  ferrous  sulphate  containing  free 
sulphuric  acid.  The  method  is  also  applicable  to  the  determination  of  nitric  acid 
in  phosphoric  acid  and  in  sulphuric  acid,  including  oleums  and  mixed  acids. 
The  reaction  in  phosphoric  acid  and  arsenic  acid  goes  further  than  it  does  in 
sulphuric  acid.  The  following  equations  represent  the  reactions  taking  place: 

Reaction  in  Arsenic  or  Phosphoric  Acids: 

6FeS04+2HN03+3H2S04  =  3Fe2(S04)3+2NO+4H20. 
Reaction  in  Sulphuric  Acid: 

4FeS04+2HN03+2H2S04  =  2Fe2(S04)3+N203+3H20. 

Oxidizing  agents  such  as  chlorates,  iodates,  bromates,  etc.,  interfere,  owing  to 
their  oxidizing  action  on  ferrous  sulphate,  hence  these  should  be  absent  from  the 
sample  or  allowance  made,  if  appreciable  amounts  are  present.  NaCl  up  to 
.002  gram  does  not  interfere;  larger  amounts  tend  to  lower  results.  KI  and  KBr 
react  in  a  similar  manner  to  NaCl,  0.002  gram  causing  no  interference.  KN02 

1  The  Jour.  Ind.  Eng.  Chem.,  7,  766,  1915. 


516  ACIDS 

present  in  amounts  up  to  50%  of  the  HN03  does  not  interfere.  The  sample 
should  not  contain  over  25%  water,  nor  should  the  temperature  exceed  60°  C. 
during  titration.  0.1  to  0.8  gram  HNO3  are  accurately  titrated,  in  sulphuric  acid. 

Special  Reagents  Required.     Standard  Ferrous  Sulphate. 

A.  Reagent  to  be  Used  in  Titration  of  Nitric  Acid  in  Sulphuric  Acid, 
Oleum,  etc.     176.5  grams  of  FeS04-  7H20  are  dissolved  in  about  400  cc.  of  water, 
and  500  cc.  of  about  60%  H2S04  (1  vol.  66°  Be*,  acid  per  1  vol.  H20)  are  added 
with  constant  stirring,  and  the  solution  (cooled  if  necessary)  made  up  to  1000  cc. 
1  cc.  will  be  equivalent  to  0.02  ±  gram  HN03,  the  exact  value  being  determined  by 
standardization. 

B.  Reagent  for  Titration  of  Nitric  in  Phosphoric  or  Arsenic  Acid.    Fer- 
rous sulphate  to  be  used,  should  be  made  up  as  follows:  264.7  grams  of  FeS04. 
7H20  is  dissolved  in  500  cc.  of  water,  50  cc.  of  66°  Be*.  H2S04  (93.2%),  added  and 
the  solution  made  up  to  1000  cc.     1  cc.  will  be  equal  to  approximately  0.02  gram 
HN03.    The  exact  strength  is  ascertained  by  titrating  a  known  amount  of  nitric 
acid  in  phosphoric  or  arsenic  acid  upon  warming  to  40°  or  50°  C. 

Standard  Nitric  Acid.  The  acid  should  contain  about  40  grams  of  HN03 
(100%)  per  liter  of  solution,  e.g.,  41  cc.  of  the  desk  reagent  (sp.gr.  1.42)  per  liter 
will  give  the  strength  desired,  the  exact  value  being  determined  by  titration  of  the 
acid  against  standard  caustic. 

Potassium  Dichromatef  N/2  K^Cr^Oi  Solution.  The  exact  value  in  terms 
of  iron  should  be  known. 

Standardization  of  Ferrous  Sulphate  Reagent 

1.  Titration  against  standard  nitric  acid. 

A.  Reagent  to  be  Used  for  Determination  of  Nitric  in  Sulphuric  Acid. 

10  cc.  of  the  standard  HN03=0.4±  g.  (the  exact  amount  having  been  ascer- 
tained), is  run  into  100  cc.  of  66°  Be".  (93.2%)  H2S04,  free  from  oxidizing  agents 
(HN03,  etc.)  and  the  resulting  mixture  titrated  with  the  standard  FeS04  solution 
according  to  the  directions  given  under  the  General  Procedure  for  determining 
HN03  in  H2S04,  page  517. 

Weight  of  HN03  taken  divided  by  cc.  of  FeS04  minus  0.2  cc.  » =  grams  HN03 
cc.  FeS04. 

B.  Standardization  of  the  Reagent  Used  in  the  Determination  of  Nitric  in 
Arsenic  and  Phosphoric  Acids.     10  cc.  of  the  standard  HN03  =  0.4±  gram  (the 
exact  amount  having  been  ascertained)  is  run  into  100  cc.  of  H2As04,  or  H3P04, 
according  to  the  product  to  be   titrated,  the  mixture  warmed  and  titrated  ac- 
cording to  directions  given  under  Procedure  for  determination  of  HN03  in  arsenic 
or  phosphoric  acid. 

Weight  of  HN03  taken,  divided  by  cc.  FeS04  =  grams  HN03  per  cc.  FeS04. 

2.  Standardizing  Ferrous  Sulphite  with  Standard  Potassium  Bichromate. 
A.  Reagent  to  be  Used  in  Determination  of  Nitric   in  Sulphuric  Acid. 

25  cc.  of  N/2  K2Cr207  (or  125  cc.  N/10  K2Cr207),  are  accurately  measured  out 

JAn  excess  of  0.2  cc.  FeSO4  is  required  to  produce  the  desired  color  reaction  in 
100  cc.  of  pure  HaSO4.  A  larger  blank  is  frequently  required,  as  HNO3  occurs  as  an 
impurity  in  H2SO4.  100  cc.  should  be  tested  for  HNO3  and,  if  present,  the  blank  sub- 
stituted for  the  constant  0.2  cc.  The  burette  should  be  allowed  to  drain  three  minutes 
before  taking  the  reading. 


ACIDS  517 

into  a  250-cc.  beaker  and  the  solution  titrated  with  the  FeS04  reagent,  until  the 
first  fraction  of  a  drop  of  excess  produces  a  blue  color  with  potassium  ferricyanide 
indicator  on  a  spot  plate.  Usually  between  19  to  20  cc.  are  required.  The  iron 
value  of  the  dichrornate  multiplied  by  0.5643=  gram  HN03  for  the  total  cc.  of 
FeS04  required  in  the  titration. 
Calculation. 

Since  N/2  K2Cr207=  0.0245 17  gram  salt,  1  gram  K2Cr207  =  1.13882  Fe,  there- 
fore 25  cc.  =0.024517X1.13882X0.5643X25  =0.3939  gram  HN03  equivalent. 

0.3939  divided  by  cc.  FeS04  required  in  the  titration  =  grams  HN03  equiv- 
alent per  cc. 

B.  Reagent  to  be  Used  in  Determination  of  HNO3  in  H3AsOt  or  #3PO4.  38 
cc.  of  K2Cr207  solution  are  titrated  with  FeS04  according  to  directions  given  in 
"  A  ".  The  Fe  value  multiplied  by  0.3762  =  gram  HN03. 

Calculation.    38  cc.  of  K2Cr207  =0.024517X1. 13882X0.3762X38  =0.3991  gram 
HN03  equivalent.    0.3991  divided  by  cc.  FeS04  required  in  the  titrati on  =  grams 
HN03  equivalent  per  c.c. 
Factors. 

K2Cr207  to  Fe  =  1.13882,  reciprocal  =  0.8781. 

2Fe  to  HN03  =  0.5643,  recip.  =  1 . 7722.     3Fe  to  HN03 = 0.3762,  recip.  =  2.6582. 

HN03  to  2FeS04.7H20  =  8.8235  recip.  =0.1 133. 

HN03  to  3FeS04.7H20  =  13.2348,  recip.  =0.07556. 

K2Cr207  to  HN03 =0.6426,  recip.  =  1.5562.     (Titration  of  A  reagent.) 

K2Cr207  to  HN03 =0.4284,  recip.  =2.3342.     (Titration  of  B  reagent.) 


NOTE.  The  two  procedures  for  standardization  agree  closely.  The  following  results 
were  obtained  on  a  check  standardization  by  the  two  procedures : 

HNO3  as  Standard— HNO3  equivalent  =  0.02068,  average  of  4  closely  agreeing 
titrations. 

K2Cr2O7  as  Standard— HNO3  equivalent  «=  0.02073,  average  of  4  closely  agreeing 
titrations. 

Runs  by  two  men  working  independently  checked  within  0.1  cc. 


General  Procedure.    Determination  of  Nitric  Acid  in 
Sulphuric  Acid 

The  procedure  is  applicable  to  the  determination  of  nitric  acid,  free  or  combined 
as  nitrate,  sulphuric  acid  being  used  as  the  medium  in  which  the  titration  is  made. 
Although  0.1  to  0.8  gram  HN03  may  begiccurately  titrated,  it  is  a  general  practice 
to  have  the  nitric  acid  content  of  the  simple  taken  for  the  titration  about  the 
same  as  the  amount  taken  in  standardization  of  the  FeS04  reagent.  A  preliminary 
run  on  the  original  material  is  made,  if  the  approximate  nitric  acid  content  is  not 
known.  Solids  are  dissolved  in  water  and  made  to  the  desired  volume,  strong 
HN03  is  diluted  with  water,  in  either  case  the  dilution  should  be  such  that  10  cc. 
of  the  solution  will  contain  approximately  0.4  gram  HN03.  Mixed  acids  and  oleum 
containing  over  10%  HN03  should  be  mixed  with  additional  66°  Be*.  (93-f-per  cent 
H2S04)  and  made  to  a  definite  volume,  an  aliquot  part  being  taken  for  titration. 


518  ACIDS 


Evaluation  of  Nitric  Acid  or  Nitrates1 

If  the  nitric  acid  is  known  to  be  free  of  other  acids  it  may  be  titrated  directly 
with  caustic;  combined  nitrate  cannot  be  titrated  with  caustic,  but  may  be  accu- 
rately determined  by  the  ferrous  sulphate  method.  The  approximate  strength 
of  the  HN03  or  salt  having  been  determined  on  1  cc.  or  1  gram  sample  (if  the  ma- 
terial is  a  solid),  the  requisite  amount  is  weighed  and  made  to  volume,  10  cc. 
of  which  should  contain  not  more  than  0.8  gram  or  less  than  0.1  gram  HN03,  pref- 
erably about  0.4  gram. 

Example.  Suppose  1  cc.  required  a  titration  of  43.8  cc.  FeS04,  10  cc.  would 
require  a  titraiion  of  438  cc.,  whereas  20  cc.  is  desired.  438  divided  by  20  =  approx- 
imately 22,  e.g.,  the  dilution  should  be  to  22  volumes.  23  cc.  of  the  solution  diluted 
to  500  cc.  will  give  a  mixture  of  the  desired  strength.  23  cc.  are  accordingly 
weighed  in  a  weighing  bottle,  the  acid  washed  into  a  beaker  transferred  then  to 
the  graduated  500-cc.  flask  and  made  to  volume.  The  preliminary  run  may  be 
made  in  two  or  three  minutes. 

Titration.  A  250-cc.  beaker  containing  100  cc.  of  strong,  nitric  free,  H2S04 
(93+%)  is  placed  in  a  large  casserole  or  deep  porcelain  dish  containing  cold  water. 
10  cc.  of  the  sample  are  measured  out  in  an  accurately  marked  pipette,  graduated 
to  contain  exactly  10  cc.  The  solution  is  run  under  the  surface  of  the  sulphuric 
acid,  the  delivery  tip  of  the  pipette  being  kept  in  constant  circular  motion  to  pre- 
vent too  much  local  heating.  Since  the  sides  of  the  beaker  are  cooled,  the  tip  of 
the  pipette  should  be  kept  against  the  sides  in  the  circular  sweep  during  the  de- 
livery. By  this  procedure  loss  of  nitric  acid  is  reduced  to  the  minimum. 

The  ferrous  sulphate  solution  is  now  added  from  a  burette  in  a  fine  stream  until 
the  yellow  color  that  first  forms  takes  on  a  faint  brownish  tinge  (dirty  yellow). 
The  pipette  is  now  rinsed  out  by  sucking  up  the  mixture  and  draining  it  back  into 
the  beaker.  The  titration  is  now  completed,  adding  the  FeS04  cautiously  drop  by 
drop  until  the  yellowish  brown  color  again  appears,  a  drop  in  excess  producing 
an  appreciable  darkening  of  the  solution.  A  larger  excess  produces  a  brownish 
red  color.  With  small  amounts  of  HN03  a  pink  color  will  be  obtained,  instead  of 
the  yellowish  brown.  The  end-point  once  recognized  is  readily  duplicated. 

Calculation.    The  cc.  titration  minus  the  constant  blank  0.2  cc.2  multiplied  by 

the  factor  for  FeS04= weight  of  HN03  in  the  sample  taken.      — 

Wt.  of  sample 

per  cent  HN03. 

Example.   Suppose  10  cc.  equivalent  to  1/50  of  a  42-g.  sample  weighed,  requires 

22  cc.  FeS04  whose  value =0.02  g.  HN03  per  cc.,  then  -=52.4%  HN03. 


Determination   of   Nitric   Acid  in   Oleum   or  in   Mixed  Acids. 
Ferrous  Sulphate  Method 

The  rapidity  and  accuracy  of  the  method  for  determining  HN03  in  sulphuric 
acid  makes  it  valuable  for  determining  nitric  acid  in  oleums  and  mixed  acids. 
Nitrated  oleums  may  be  weighed  and  titrated  without  diluting  to  definite  volume, 

1  The  author  (W.  W.  Scott)  found  this  method  exceedingly  useful  in  his  tests  of  the 
synthetic  nitric  acid  made  by  himself,  during  his  investigation  of  the  manufacture  of 
this  acid  from  its  elements. 

2  See  Correction  Factor,  page  519.   i 


ACIDS  519 

mixed  acids  containing  large  percentages  of  nitric  acid,  however,  require  dilution 
with  H2S04,  as  stated  under  General  Procedure. 

Procedure.  The  sample  may  be  weighed  in  a  Dely  weighing  tube  (see  analysis  of 
oleum  and  mixed  acids),  or  in  a  standard  pipette  (5  cc.  generally  taken  =  9.61  grams). 
If  the  latter  is  used,  the  sample  is  sucked  into  the  pipette,  a  rubber  tube,  with  glass 
bead  valve,  being  attached  to  the  upper  end,  to  which  suction  is  applied  without 
danger  of  drawing  S03  fumes  into  the  mouth.  A  little  vaseline  placed  on  the  tip 
of  the  pipette  prevents  loss  of  acid  during  the  weighing.  In  routine  analysis, 
where  a  large  number  of  daily  samples  of  oleum  are  analyzed,  and  the  specific 
gravity  of  the  oleum  does  not  vary  appreciably,  5-  to  10-cc.  samples  may  be  drawn 
out,  by  means  of  a  pipette,  and  titrated  without  weighing,  the  weight  being  cal- 
culated from  the  gravity. 

The  acid  is  run  under  cold  concentrated  H2S04  (93%),  and  titrated  according 
to  directions  under  General  Procedure  for  Nitric  acid.  A  blank  of  0.2  cc.1  having 
been  deducted,  cc.  FeS04XHN03  factor  for  FeS04X100  divided  by  wt.  taken 
=  per  cent  HN03. 

Correction  Factor.  In  making  a  number  of  runs  with  varying  amounts  of  HNO3, 
it  was  found  that  small  quantities  of  nitric  acid  required  a  proportional  greater  amount 
of  FeSO4  than  larger  quantities  of  HNO3.  For  example,  0.07392  gram  HNO3  required 
3.9  cc.  FeSO4,  four  times  the  amount  of  HNO3  required  15  cc.  FeSO4,  in  place  of  15.6, 
(3.9  X4)  and  six  times  0.07392  gram  HNO3  required  22.5  cc.  FeSO4  in  place  of  23.4.  It 
was  observed  that  even  traces  of  HNO3  required  a  titration  of  over  0.2  cc.  It  is  evi- 
dent that  a  deduction  of  0.2  cc.  makes  the  titrations  multiples  of  the  lowest,  e.g.,  3.7, 
14.8  and  22.3.  Again  it  was  found  that  standardization  of  FeSO4  with  HNO3  checked 
the  dichromate  factor  when  0.2  cc.  was  deducted  from  the  first  series  of  titrations.  This 
led  to  the  conclusion  that  a  constant  blank  of  0.2  cc.  should  be  deducted  from  the  ferrous 
sulphate  titrations  of  nitric  acid  in  presence  of  100  cc.  of  nitric  free  sulphuric  acid, 
(66°  Be.). 

Comparison  of  results: 

FeSO4  value  by  HNO3  corrected =0.02067  gram.     Uncorrected  =  0.02045  gram  HNO3. 

FeS04  value  by  K2Cr2O7  titration =0.02083  gram  HNO3. 

Accuracy  of  the  Ferrous  Sulphate  Method.  Results  obtained  by  the  ferrous  sul- 
phate method  agree  closely  with  those  obtained  by  the  nitrometer.  The  following 
data  were  obtained  by  Mr.  B.  S.  Clark,2  by  the  FeSO4  method,  on  nitrated  oleums. 
The  figures  below  the  first  row  are  checks  obtained  on  these  samples  by  purchasers  of 
the  acid,  the  nitrometer  method  being  used. 

FeSO4  method.  2.40;  2.82;  3.23;  3.35;  3.52;  3.50;  3.48;  3.57;  3.53;  3.56. 

Nitrometer  method.  2.35;  2.79;  3.26;  3.39;  3.57;  3.53;  3.50;  3.58;  3.57;  3.56. 

Difference.  0.05;  0.03;  0.03;  0.04;  0.05;  0.03;  0.02;  0.01;  0.04;  0.00. 

Determination  of  Nitric  Acid  in  Arsenic  and  Phosphoric  Acids 
by  the  Ferrous  Sulphate  Method 

A  direct  procedure  for  the  determination  of  nitric  acid  in  arsenic  acid  or  phos- 
phoric acid  has  been  sought  on  account  of  the  inaccuracy  of  the  evaporation 
method,  since  it  is  difficult  to  completely  expel  HN03  from  these  acids.  Ferrous 

1  Back  titrations  of  the  excess  of  FeSO4  may  be  made  with  standard  K2Cr207,  using 
the  ferricyanide  spot  test  for  ferrous  iron. 

Sp.gr.  of  twelve  average  samples  of  oleum  had  a  difference  of  only  0.01.  5  cc. 
weighs  9. 61  grams.  This  is  found  convenient  for  analysis.  10  cc.  =  19.22  grams  will 
usually  give  a  titration  of  about  20+cc.  on  the  usual  nitrated  oleum. 

2  Formerly  Chemist  U.  S.  Works,  G.C.C.,  Camden,  N.  J. 


520  ACIDS 

sulphate,  in  presence  of  sulphuric  acid,  quantitatively  titrates  nitric  in  arsenic 
acid,  the  following  reaction  taking  place: 

6FeS04+2HN03+3H2S04+xH3As04=3Fe2(S04)3+2NO+4H20-hxH3As04. 

The  procedure  is  applicable  to  the  determination  of  nitric  acid  in  phosphoric 
acid,  the  end-point  being  sharper  in  this  acid  than  in  arsenic.  The  procedure  gives 
very  excellent  results  in  either  acid  and  is  recommended  for  accuracy  and 
rapidity. 

Standardization  of  Ferrous  Sulphate  has  already  been  given  under  special 
reagents.  It  must  be  remembered  that  the  arsenic  or  phosphoric  acid  diluents 
should  be  free  from  nitric  acid  or  the  blank  on  100  cc.  be  ascertained  and  de- 
ducted from  titrations  made  in  this  diluent. 

Procedure.  The  amount  of  the  sample  to  be  taken  is  governed  by  the  nitric 
acid  present  as  an  impurity.  This  may  be  quickly  determined  by  a  preliminary 
run  on  a  10-cc.  sample,  the  diluent  being  the  same  acid  (HN03  free)  as  the  acid 
titrated. 

Example.  Suppose  10  cc.  require  a  titration  of  4.5  cc.  of  FeS04,  whereas  a 
titration  of  20  cc.  is  desired,  then  20X10-7-4.5  =44.44  cc.  of  the  sample  required. 

The  required  amount  of  the  acid  is  measured  out  and  weighed,  if  its  sp.gr.  is 
not  known.  The  acid  is  poured  into  a  4-in.  casserole  and  diluted  with  100  cc. 
of  nitric  free  acid  of  the  same  kind  as  that  being  titrated.  The  mixture  is  gently 
warmed  to  40  to  50°  C.  and  titrated  with  standard  ferrous  sulphate  reagent  to  a 
permanent  yellowish  brown.  Towards  the  end  of  the  titration  the  acid  will  boil 
with  each  addition  of  the  FeS04  and  the  characteristic  reddish  yellow  fumes  will 
be  given  off.  (This  does  not  occur  in  titrations  of  HN03  in  H2S04.) 

When  very  small  amounts  of  nitric  acid  are  present  it  is  often  necessary  to 
add  a  known  amount  of  HN03  to  start  the  reaction.  The  titration  in  excess  of 
that  required  by  the  added  HN03  is  due  to  the  nitric  acid  in  the  sample.  Very 
small  amounts  of  HN03  produce  a  pink  color. 

Calculation  cc.  FeS04XHN03  factor  for  FeSC^XlOO  divided  by  weight  taken 
=per  cent  HN03. 

Factors.    Fe  to  HN03  =0.3762.    Reciprocal  =2.6582. 

NOTE.     In  a  20-gram  sample  1  cc.  0.02  reagent  =  0.1%  per  cc. 


DETERMINATION  OF  NITROUS  ACID  OR  NITRITE 
PERMANGANATE   METHOD 

Principle.  Potassium  permanganate  reacts  with -nitrous  acid  or  a  nitrite  as 
follows: 

5N203-f-4KMn04-f6H2S04=5N205-f-2K2S04+4MnS04+6H20. 

5HN02+2KMn04+3H2S04  =  5HN03-fK2S04+2MnS04+3H20. 

Since  2KMn04  in  acid  solution  has  five  available  oxygens  for  oxidation  of  sub- 
stances (e.g.,2KMn04  =K20.2Mn04-5O  equivalent  to  10H)  the  molecular  weights 
of  the  constituents  divided  by  20  in  the  first  equation  and  by  10  in  the  second  would 
represent  the  normal  weights  per  liter,  e.g.,  5N203  divided  by  20=76  divided  by 


ACIDS  521 

4  =  19  grams  N203  per  liter.  4KMn04  divided  by  20  or  2KMn04  divided  by  10 
=  158.03  divided  by  5=31.61  grams  of  KMn04  per  liter  for  a  normal  solution. 
In  the  second  equation  if  Na  represents  the  univalent  element  we  would  have 
5NaN02  divided  by  10  or  69  divided  by  2  =34.5  grams  per  liter.  Hence  1  cc.  of 
a  normal  KMn04  solution  would  oxidize  0.019  gram  N203  or  0.0345  gram  NaNOa 
to  form  N206  and  NaN03  respectively. 

Organic  matter  is  also  oxidized  by  KMn04  hence  will  interfere  if  present. 

Special  Reagents. 

N/5  Potassium  Permanganate.  The  solution  contains  6.322  grams  KMn04 
per  liter. 

N/5  Sodium  Oxalate.    Na2C204  reacts  with  KMn04  as  follows: 
5Na2C204+2KMn04+8H,S04=K2S04+2MnS04+5Na2S04+10C02+8H20. 

Hence  5Na2C204  divided  by  10  or  134  divided  by  2=67  grams  per  liter  =  a 
normal  sodium  oxalate  solution.  A  N/5  solution  requires  13.4  grams  Na2C204 
per  liter. 

Preparation  of  the  Sample. 

Soluble  Nitrites.  Ten  grams  of  the  nitrite  are  dissolved  in  water  and  made 
to  1000  cc.;  10  cc.  contain  0.1  gram  of  the  sample. 

Water-insoluble  Nitrites.  0.5  to  1.0  gram  of  the  nitrite  according  to  the 
amount  of  nitrous  acid  present  is  taken  for  analysis.  An  excess  of  KMn04  solu- 
tion is  added,  followed  by  dilute  H2S04  and  the  excess  standard  permanganate 
titrated  with  sodium  oxalate  according  to  directions  given  under  Procedure. 

Nitrous  Acid  in  Nitric  Acid  and  Mixed  Acids.  This  is  present  generally  in 
very  small  amounts  so  that  a  large  sample  is  taken.  The  amount  and  details  of 
the  procedures  are  given  under  the  special  subject. 

Procedure.  For  accurate  work  a  chamber  burette  is  recommended,  as  in  case 
of  titration  of  acids,  graduated  from  50  cc.  to  100  cc.  Since  the  readings  will  fall 
between  these  extremes  the  sample  should  contain  an  equivalent  of  0.19  to  0.38 
gram  N203,  or  0.345  to  0.69  gram  NaN02  or  0.426  to  0.85  gram  KN02.  In  soluble 
commercial  nitrites,  NaN02  or  KN02,  50  cc.  of  the  above  solution  (0.5  gram)  are 
generally  sufficient  for  titration.  A  preliminary  run  will  show  approximately  the 
amount  of  nitrite  present  and  the  amount  of  sample  taken  is  governed  accordingly. 

For  routine  work  where  a  number  of  daily  determinations  are  made,  a  50-cc. 
burette  is  generally  preferred.  Half  the  above  samples  must  then  be  taken. 

Trial  Run.  If  the  approximate  strength  of  the  salt  is  not  known  the  following 
test  may  be  quickly  made  to  ascertain  whether  more  than  50  cc.  of  solution  is 
necessary  and  the  approximate  amount  of  KMn04  required  for  oxidation. 

Ten  cc.  of  the  solution  together  with  100  cc.  of  water  are  placed  in  a  4-in. 
casserole  and  about  10  cc.  of  dilute  H2S04,  1:1,  added.  Standard  KMn04  from 
a  50-cc.  burette  is  now  run  into  the  sample  until  a  permanent  pink  color  is  obtained. 
The  cc.  of  KMn04  multiplied  by  5=  the  approximate  amount  of  permanganate 
solution  required  for  oxidation  of  50  cc.  of  sample.  An  excess  of  5  to  10  cc.  should 
be  taken  in  the  regular  run. 

Titration  of  Nitrite.  Fifty  cc.  of  the  solution  (or  more  or  less  as  the  case 
may  require)  are  placed  in  a  4-in.  casserole  and  standard  KMn04  added  in  quantity 
sufficient  to  completely  oxidize  the  nitrite  together  with  5  to  10  cc.  in  excess,  as 
ascertained  by  the  trial  run.  Ten  cc.  of  dilute  H2S04  are  added  and  the  sample 


522 


ACIDS 


placed  on  the  hot  plate  until  the  mixture  reaches  a  temperature  of  70°  to  80°  C. 
About  25  cc.  more  of  the  dilute  acid  are  now  added  and  the  excess  permanganate 
titrated  in  a  hot  (approx.  80°  C.)  solution  with  N/5  sodium  oxalate.  The  Na2C204 
solution  should  be  added,  from  a  25-cc.  burette,  cautiously  allowing  time  for 
reaction  with  each  addition.  When  the  pink  color  fades  the  reading  is  taken.  A 
drop  of  N/5  KMn04  should  restore  the  pink  color.  Total  permanganate  taken 
minus  the  back  titration  with  oxalate  =  cc.  KMn04  required  by  the  nitrite. 

One  cc.  N/5  KMn04  =0.0038  g.  N203,  or  0.0069  g.  NaN02,  or  0.0085  g.  KN02. 


THE  ANALYSES  OF  OLEUM  OR  FUMING  SULPHURIC  ACID 
AND  OF  MIXED  ACID 

The  analyses  of  fuming  sulphuric  acid  and  mixed  acid  are  placed  under  one 
general  scheme  as  the  procedure  for  oleum  is  included  in  that  of  mixed  acid.  The 
term  oleum  is  given  to  strong  sulphuric  acid  containing  free  S03,  the  combined 


FIG.  84. — Method  for  Rapid  Evaporation  of  Liquids. 


water  in  the  product  decreasing  (along  with  sulphuric  acid)  with  the  increase  of 
free  S03  or  sulphuric  anhydride.  Mixed  acid  is  the  technical  name  for  the  mixture 
of  strong  sulphuric  acid  and  nitric  acid  or  of  oleum  and  nitric  anhydride,  the 
product  being  commonly  used  in  nitrating  glycerine,  cotton  and  other  materials. 
The  analysis  includes  the  determinations  of  H2S04,  HN03,  N206,  N203  and  in  the 
case  of  oleum,  the  determination  of  S03.  In  the  presence  of  the  latter,  HN03  is 
assumed  to  lose  its  combined  water  according  to  the  reaction: 

2HN03+S03=H2S04+N206 

In  absence  of  nitric  acid  S02  may  be  present.  It  is  assumed  that  if  HN03  is 
present  the  S02  is  oxidized  to  S03  with  formation  of  H2S04  and  the  anhydrides 
S03  and  N203  according  to  the  reaction. 

N206+H20+2S02  =N203+S03+H2S04 
Some  chemists  prefer  to  express  the  reaction: 

2HNO.+SO,  =H2S04+N204. 

The  analysis  is  carried  out  by  three  titrations — (a)  determination  of  total 
acidity,  (6)  determination  of  sulphuric  acid  including  S03  free  in  case  of  oleum, 
(c)  determination  of  lower  oxides. 


ACIDS  523 

For  economy  of  time  the  following  order  should  be  observed:  The  sample 
for  the  determination  of  sulphuric  acid  and  free  S03  (oleum)  should  be  weighed, 
diluted  with  water  according  to  the  detailed  procedure  and  placed  on  the  steam 
bath  for  evaporation.  During  the  evaporation  the  titration  for  total  acidity  of 
the  sample  and  the  titration  for  the  lower  oxides  are  made  and  finally  that  of  oleum 
on  the  evaporated  sample. 

Special  Reagents. 

Normal  Sodium  Hydroxide.     One  cc.  =0.04904  gram  H2S04. 

Tenth  Normal  Potassium  Permanganate.  3.16  grams  KMn04  per  liter. 
Standardized  against  N/10  solution  of  Sorensen's  Sodium  Oxalate.  (See  Prepara- 
tion of  Standard  Reagents.)  One  cc.  =  0.0019  gram  N203,  or  0.002351  gram  HNO2. 

Procedure.    Total  Acids 

The  sample  is  accurately  weighed  by  one  of  the  procedures  recommended  for 
strong  acids.  The  Dely  or  Blay-Burkhard  tubes  are  best  for  this  purpose. 
Such  a  weight  being  taken  as  will  require  a  titration  between  75  and  100  cc., 
e.g.,  containing  an  equivalent  of  3.675  grams  to  4.9  grams  H2S04.  The  acid  is 
now  run  under  cold  C02  free  water  according  to  directions  on  pages  507  and  508, 
and  the  acid  titrated  with  N/l  solution  of  NaOH. 

AT    rvrr      KKAMA        TT  o^        ^i       i±  x  CC.  NaOH  X  .04904  X 100 

One  cc.  NaOH  =  0.04904  g.  H2S04.    Calculate  to  per  cent  TT7  .  .  — . 

Weight  of  Acid  Taken 

Lower  Oxides 

Ten  cc.  of  the  sample,  weighed  in  a  pipette  with  capillary  delivery  tip,  are 
cautiously  run  into  about  400  cc.  of  cold  water,  keeping  the  delivery  tip  well  under 
the  water  and  in  rapid  motion  to  prevent  overheating  through  local  action.  The 
mixture  is  titrated  with  N/10  KMn04  until  a  pink  tint  is  obtained  that  does  not 
fade  in  three  minutes. 

1  cc.  N/10  KMn04  =  0.0019  g.  N203.  (N203  to  N204  factor  =2.42.) 

1  cc.  N/10  KMn04  =  0.0046  g.  N204. 

1  cc.  N/10  KMn04  =  0.00235  g.  HN02.        Equivalent  H2S04  =  0.0049043  g.  per  cc. 

1  cc.  N/10  KMn04  =  0.0032035  g.  S02. 

1  cc.  N/10  KMn04  =  0.0041043  g.  H2S03. 

NOTE.     With  exactly  N/10  KMnO4  on  a  19-gram  sample  1  cc.  =0.01%  N2O3. 

Sulphuric  Acid  and  Free  SOs 

The  sample  is  weighed  in  a  Dely  tube  and  run  under  cold  water,  as  in  case 
of  total  acids,  using  in  this  case  about  45  to  50  cc.  of  water  in  a  4-in.  casserole. 
The  solution  is  evaporated  on  the  steam  bath  to  expel  the  volatile  acids,  lower 
oxides  and  nitric.  The  evaporation  is  hastened  by  blowing  a  current  of  hot,  dry, 
pure  air  over  the  sample,  see  Fig.  84.  Instead  of  a  casserole,  a  shallow  glass 
cell,  3  inches  in  diameter  and  1|  inches  deep  may  be  used.  The  air  current  in 


524  ACIDS 

this  case  is  unnecessary.     About  5  cc.  of  water  are  added  and  this  again  evapor- 
ated off.     The  acid  thus  obtained  is  H2S04+S03. 

The  acid  is  taken  up  with  water  and  titrated  with  standard  caustic,  using  COa 
free  water  and  phenolphthalein  indicator. 

One  cc.  N/l  NaOH  =0.004904  gram  H2S04. 

Nitric  Acid 

This  may  be  obtained  from  the  above  determinations  according  to  calculations 
following.  It  may  be  obtained  by  direct  titration  with  standard  ferrous  sulphate, 
by  running  a  weighed  amount  of  mixed  acid  into  100  cc.  of  cold  sulphuric  acid  and 
titrating  to  a  yellowish  red  tint.  For  the  detailed  procedure  see  Nitric  Acid, 
page  515. 

Calculation  of  Results. 

A.  Nitric  Acid  and  SO2  being  Absent. 

The  total  acidity  is  calculated  to  S03.  Reference  is  made  to  the  table  for 
Oleum  from  which  the  per  cent  H2S04  and  free  S03  are  obtained. 

Example.  Suppose  the  total  acidity  in  terms  of  S03  was  found  to  be  84.2. 
The  acid  contains  86%  H2S04  and  14%  free  S03. 

B.  Nitric  Acid  Absent,  SO2  is  Present  in  the  Mixture. 

Total  SOs.  From  total  acidity  as  S03  subtract  S02X1.25  (i.e.,  equivalent 
SO,). 

Combined  water.    100  -  (total  S03+S02)  =H20. 
Combined  SO3.    H2OX  4.4445  =  S03  equivalent  or  combined  S03. 
Free  SO3.    Total  S03  -  combined  S03  =  free  S03. 
Sulphuric  acid.     Combined  S03+H20. 

Example.  If  S02  was  found  to  be  2%  and  the  total  acidity  in  terms  of  SOj 
=  83.5% 

Total  SO,  =83.5  -(2  XI.  25)  =81%. 

Water  =  100  -  (81  +2)  =  17%.          Report 
Combined  S03  =  17X4.4445  =75.56%.  Sulphuric  acid  =92.56%. 

Free  S03  =81  -75.56  =5.44%.  Free  S03  =5.44. 

Sulphuric  acid  =75.56+17  =92.56%.  S02  =2.00.    Total  100. 

C.  Nitric  Acid  Present  and  SO2  Absent. 

Nitric  acid  in  presence  of  free  S03  is  assumed  to  be  the  anhydride  N206. 
N2Os.     From  the  total  acidity  is  subtracted  the  acidity  after  evaporation,  both 
being  calculated  to  equivalent  S03.    The  difference  multiplied  by  1.349  =  per  cent 


H2O.     Total  S03  (after  evaporation)  +N206  subtracted  from  100  =  H20. 
Combined  SO3.     H20  X  4.4445  =  S03  equivalent  to  H20. 
Free  SO3.    Combined  SO3  subtracted  from  total  S03  =  free  S03. 
Sulphuric  acid.    Combined  S03+H20  =  H2S04. 

Example.    If  total  acidity  =  84%  in  terms  of  S03  and  the  total  SOS  (after 
evaporation)  =  82%,  then  the  difference  2  X  1.349  =  2.698%  N206. 


ACIDS  525 

Water  =  100-  (82+2.698)  =  15.302%.  Report 

Combined  S03  =  15.302X4.4445  =  68.01%.  H2S04  =  83.312%. 

Free  S03  =  82  -68.01  =  13.99%.  Free  S03  =  13.980%. 

H2S04  =  68.01  +  15.302  =  83.312%.  N205=  2.698%. 

Total  100. 

D.  NZO5  Required  to  be  Reported  as  HNO3,  96  '%.*• 
HNOs,    Q6%  =  S03   equivalent    (acid   expelled  by  evaporation)  XI.  64.     100 

-per  cent  HN03  (96%)  =  01eum.     Total  S03  in  oleum  =  1QOXtota|  S°3. 

per  cent  oleum 

Reference  to  the  oleum  table  will  give  the  per  cent  free  S03  in  the  oleum. 

Example.  Suppose  total  acidity  in  terms  of  S03  =  84%  and  the  S03  after 
evaporation  =  82%,  then  HN03,  96%  =  the  difference  =  2X1.  64  =  3.  28%  HN03 
(96%). 

Oleum  =  100  -3.28  =96.72%. 

Total  S03  in  oleum  =  100X82  divided  by  96.72  =84.78. 

From  the  oleum  table  84.78  gives  17.10%  free  S03. 

Report 

Nitric  acid,  96%  =  3.28% 

Oleum  =96.72% 

FreeS03  =17.10% 

Total  S03  =84.78% 

The  nitric  acid  and  oleum  make  a  total  of  100. 
Formulae  for  Diluting  or  Strengthening  Solutions.* 
To  dilute  a  solution  with  watei  : 

(a)  ^=X;  Y=Z-X;        or        (6)  ^ 

To  dilute  a  strong  with  a  weaker  liquid: 

,  .   -A-     DA     T7.  _  T7.  /1A  A.     DX. 

a-=Y         X-Z=Y'        or  - 


To  strengthen  a  weak  with  a  stronger  liquid: 


A  =  actual  concentration  of  the  solution  that  is  to  be  corrected; 
B  =  concentration  of  the  diluting  solution; 
C=  concentration  of  the  strengthening  solution; 
D  =  desired  concentration  ; 

X  =  amount  of  the  stronger  solution  to  be  added,  taken  or  prepared; 
Y  =  amount  of  weaker  solution  to  be  added  or  taken; 
Z  =  amount  of  solution  desired  or  given. 
All  data  are  in  terms  of  weight  of  the  constituents. 

1  This  is  the  usual  strength  of  the  commercial  concentrated  acid. 

2  Compiled  by  J.  B.  Barnitt. 


526  ACIDS 

METHOD  OF  ANALYSIS  OF  CHLOROSULPHONIC  ACID 

Chlorosulphonic  acid,  S03-  HCl,  decomposes  to  H2S04  and  IIC1  on  addition 
of  water,  the  reaction  being  violent.  Considerable  care  must  be  exercised  to 
prevent  loss  of  acid  during  dilution  with  water  for  examination  of  the  product. 
The  following  method  of  analysis  has  been  found  satisfactory: 

Total  Acidity.  Three  to  four  grams  of  the  chlorosulphonic  acid  are  weighed 
in  a  De*li  tube  or  small  glass  bulb.  About  25  cc.  of  distilled  (neutral)  water  and 
about  10  cc.  less  NaOH  (normal  strength)  than  is  necessary  to  neutralize  the 

sample  (i.e.,  -  --  10  =  cc.  NaOH  to  be  taken)  are  placed  in  a  heavy 


wall  glass  bottle  (250-300  cc.  capacity).  If  the  sample  is  weighed  in  a  De*li  tube 
it  is  run  into  the  NaOH  solution  according  to  the  procedure  described  on  page 
506.  If  the  bulb  is  used,  the  bottle,  with  the  sample  inserted,  is  stoppered, 
wrapped  in  a  towel  and  shaken  vigorously  until  the  bulb  breaks  and  the  acid 
mixes  with  the  water  and  NaOH.  The  excess  of  acid  is  now  titrated  with  N. 
NaOH,  using  phenolphthalein  or  methyl  red  indicator.  The  total  acidity  is  cal- 
culated to  S03  and  recorded  as  per  cent  S03. 

Titration  of  Chloride.  The  NaCl  formed  is  titrated  with  N/3  AgN03  solu- 
tion, using  K2Cr04  indicator.  The  cc.  of  the  reagent  are  calculated  to  the  equiv- 
alent HC1.  Since  NaOH  is  apt  to  contain  NaCl,  the  blank  is  subtracted  to 
obtain  the  true  HC1  equivalent  in  the  sample.  The  per  cent  HC1  is  calculated. 

The  Composition  of  the  Acid  is  now  determined  as  follows: 

(a)  Total  acid  as  per  cent  S03  =  a. 

(b)  HCl  obtained  by  titration  of  the  neutralized  solution  (made  faintly  acid) 
with  N/3  AgN03  (the  HCl  blank  for  the  NaOH  used  in  (a)  having  been  subtracted) 
=  6.     The  HCl  is  converted  to  its  equivalent  S03  by  multiplying  by  1.0978=6'. 

(c)  £03  (combided  and  free).      The  S03  equivalent  of  HCl  obtained  in  b  is 
subtracted  from  the  total  acidity  as  SO;J  of  (a)  is  a—  6'  =  S03  total. 

(d)  100  -(per  centS03+per  cent  HCl)  =  per  cent  H20  in  sample.     This  is 
combined  with  a  portion  of  the  S03  as  H.S04.     Calculate  to  per  cent  H2S04  by 
multiplying  by  5.4444. 

(e)  The  S03  combined  with  H20  is  subtracted  from  the  total  S03  of  (c).     The 
result  is  the  S03  of  the  chlorosulphonic  acid  and  free  S03  (if  any). 

By  inspection  it  is  possible  to  ascertain  whether  the  product  contains  free 
S03  or  free  HCl  since  SO3-HC1  are  in  the  proportion  31.29  per  cent  HCl  and 
68.71  per  cent  S03,  i.e.,  HCl  :  S03::  1  :  2.2. 

//  S03  is  in  excess.  The  HCl  is  calculated  to  S03  •  HCl  by  multiplying  by 
3.1956,  the  result  is  the  per  cent  chlorosulphonic  acid  in  the  sample. 

Free  S03  is  obtained  by  subtracting  per  cent  S03-HC1  +  per  cent  H2S04 
from  100. 

//  HCl  is  in  excess.  The  per  cent  S03  obtained  in  (e)  is  multiplied  by  1.4555; 
the  result  is  the  per  cent  chlorosulphonic  acid. 

FreeHCl  is  obtained  by  subtracting  per  cent  S03  •  HCl  -fper  cent  H.S04  from  100. 

Results  are  reported  as  per  cent  S03-HC1,  H2SO,,  free  S03  or  free  HCl. 

Factors  : 

HCl  X  1.0978  =  S03,    HC1X3.1956  =  S03-HC1   and   HClx2.1959  =  S03  in  S03HC1. 
SO3  X0.8998  =  HC1,  S03  X  1.4555  =  S03-  HCl   and   S03  X  0.4554=  HCl  in  S03HC1. 
H20  X5.4444  =  H2S04,     H3S04  X0.1837  =H20,  H2S04  X0.7436  =  HC1. 
NaCl  X0.6238  =HC1,     S03-HC1=31.29  per  cent  HCl  and  68.71  per  cent  S08. 


ACIDS  527 


ANALYSIS  OF  ACETIC  ACID 

The  acidity  of  acetic  acid  may  be  determined  by  titration  with  standard  caustic, 
using  phenolphthalein  as  indicator. 

About  4  to  5  grams  of  glacial  acetic  acid  or  a  corresponding  amount  of  dilute 
acid  are  taken  for  analysis,  being  weighed  out  in  a  weighing  bottle  or  other  suitable 
container  used  for  strong  and  weak  acids.  The  acid  is  mixed  with  about  250  cc. 
of  water  and  titrated  in  the  presence  of  phenolphthalein  indicator  with  normal 
caustic. 

One  cc.  N/l  NaOH  =0.06003  gram  CH3COOH. 

Impurities  in  Acetic  Acid 

The  more  important  impurities  that  are  looked  for  in  commercial  acetic  acid 
are  formic  acid,  furfurol,  acetone,  sulphuric  acid,  sulphurous  acid,  hydrochloric 
acid,  metals. 

In  the  examination  of  the  acid  the  physical  appearance — turbidity  and  color 
are  noted. 

Formic  Acid  in  Acetic 

Qualitative.  Ten  cc.  of  the  acid  (glacial  diluted  1  :  10)  are  heated  with  1  gram 
of  sodium  acetate  and  5  cc.  of  5  per  cent  mercuric  chloride  solution.  A  turbidity 
indicates  formic  acid. 

Quantitative.  Five  grams  of  glacial  acetic  acid  or  corresponding  quantity  of 
dilute  acid  are  treated  with  5  grams  of  sodium  acetate  and  40  cc.  of  mercuric 
chloride  solution  (5  per  cent)  and  30  cc.  of  water  added.  The  mixture  is  heated 
for  two  hours  in  a  flask  with  a  return  condenser,  the  flask  being  surrounded  by 
steam.  The  precipitated  mercurous  chloride,HgCl,  is  filtered  off,  dried  and  weighed. 

Weight  of  HgClXO.0977  =formic  acid  equivalent. 

Furfurol  in  Acetic  Acid 

Qualitative.  Aniline  dissolved  in  pure  glacial  acetic  acid  (5  cc.  aniline  in  2  cc. 
glacial  acetic  acid)  and  added  to  100  cc.  of  the  sample  will  produce  a  red  color  in 
presence  of  furfurol. 

Quantitative.  The  test  may  be  made  quantitative  by  comparing  the  color 
produced  with  standard  solutions  containing  known  amounts  of  furfurol.  One 
gram  of  redistilled  furfurol  is  dissolved  in  100  cc.  of  95  per  cent  alcohol.  1  cc.  of 
this  solution  is  diluted  to  100  cc.  with  95  per  cent  alcohol.  1  cc.  =  0.0001  gram 
of  the  reagent. 

Test  for  furfurol  in  vinegar.  Fifty  cc.  of  the  vinegar  is  neutralized  with 
sodium  hydroxide,  and  15  to  20  cc.  are  distilled.  Two  cc.  of  colorless  aniline  and 
15  cc.  of  hydrochloric  acid  (1:12)  added.  The  mixture  is  warmed  to  about  15° 
C.  for  a  few  minutes  and  the  color  compared  with  standards  prepared  in  the  same 
way. 


528  ACIDS 


Gravimetric  Method  with  Phloroglucid 

Place  a  quantity  of  the  material,  chosen  so  that  the  weight  of  phloroglucid 
obtained  shall  not  exceed  0.300  gram,  in  a  flask,  together  with  100  cc.  of  12  per 
cent  hydrochloric  acid  (specific  gravity,  1.06),  and  several  pieces  of  recently 
heated  pumice  stone.  Place  the  flask  on  a  wire  gauze,  connect  with  a  condenser, 
and  heat,  rather  gently  at  first,  and  so  regulate  as  to  distill  over  30  cc.  in  about 
ten  minutes,  the  distillate  passing  through  a  small  filter  paper.  Replace  the 
30  cc.  driven  over  by  a  like  quantity  of  the  dilute  acid  added  by  means  of  a  separa- 
tory  funnel  in  such  a  manner  as  to  wash  down  the  particles  adhering  to  the  sides 
of  the  flask,  and  continue  the  process  until  the  distillate  amounts  to  360  cc.  To 
the  completed  distillate  gradually  add  a  quantity  of  phloroglucol  (purified  if  neces- 
sary) dissolved  in  12  per  cent  hydrochloric  acid  and  thoroughly  stir  the  resulting 
mixture.  The  amount  of  phloroglucol  used  should  be  about  double  that  of  the  fur- 
fural expected.  The  solution  first  turns  yellow,  then  green,  and  very  soon  an 
amorphous  greenish  precipitate  appears,  which  grows  rapidly  darker,  till  it  finally 
becomes  almost  black.  Make  the  solution  up  to  400  cc.  with  12  per  cent  hydro- 
chloric acid,  and  allow  to  stand  overnight. 

Filter  the  amorphous  black  precipitate  into  a  tared  Gooch  crucible  through 
an  asbestos  felt,  wash  carefully  with  150  cc.  of  water  in  such  a  way  that  the  water 
is  not  entirely  removed  from  the  crucible  until  the  very  last,  then  dry  for  four 
hours  at  the  temperature  of  boiling  water,  cool  and  weigh,  in  a  weighing  bottle, 
the  increase  in  weight  being  reckoned  as  phloroglucid.  To  calculate  the  furfural, 
pentose,  or  pentosan  from  the  phloroglucid,  use  the  following  formulas  given  by 
Krober: 

(a)  For  weight  of  phloroglucid  "  a  "  under  0.03  gram. 

Furfural  =  (a+0.0052)  X0.5170. 
Pentoses  =  (a+0.0052)  X  1.0170. 
Pentosans  =  (a+0.0052)  X  0.8949. 

(6)  For  weight  of  phloroglucid  "  a  "  over  0.300  gram. 

Furfural  =  (a+0.0052)  X  0.5180. 
Pentoses  =  (a+0.0052)  X  1.0026. 
Pentosans  =  (a+0.0052)  X  0.8824. 

For  weight  of  phloroglucid  "  a  "  from  0.03  to  0.300  gram  use  Krober's  table 
or  the  following  formulas : 

Furfural  =  (a+0.0052)  X0.5185. 
Pentoses  =  (a+0.0052)  X  1.0075. 
Pentosans  =  (a+0.0052)  X  0.8866. 

The  phloroglucol  is  purified  by  recrystallization  from  hydrochloric  acid.  For 
details  of  the  procedure  see  Bulletin  107,  U.  S.  Dept.  of  Agriculture,  Bureau  of 
Chemistry.  (1912,  page  54.) 

Acetone  in  Acetic  Acid 

Fifteen  grams  of  glacial  acetic  acid,  or  a  corresponding  amount  of  weak  acid,  is 
treated  with  70  cc.  potassium  hydroxide  (10  per  cent  solution),  or  sufficient  caustic 


ACIDS  529 

to  make  the  solution  slightly  alkaline.  The  solution  is  cooled  and  25  cc.  N/5 
iodine  solution  added  and  sufficient  hydrochloric  acid  to  make  the  mixture  faintly 
acid.  The  excess  of  iodine  is  titrated  with  N/5  sodium  thiosulphate,  using  starch 
indicator.  The  total  iodine  solution  taken  minus  the  equivalent  cc.  of  thiosulphate 
=  the  iodine  combined  with  the  acetone,  then  the  weight  of  iodine  in  grams  mul- 
tiplied by  0.07612  =  grams  acetone  in  the  sample. 

Sulphuric  Acid  in  Acetic  Acid 

This  is  best  determined  by  the  turbidity  test.  About  5  cc.  of  the  sample  are 
taken  and  1  drop  of  hydrochloric  acid  and  half  a  cc.  of  10  per  cent  barium  chloride. 
The  turbidity  is  now  compared  with  a  standard  pure  acetic  acid  solution  containing 
a  known  quantity  of  BaS04,  the  standard  being  added  to  a  comparison  cylinder 
until  the  turbidity  is  the  same  as  that  of  the  sample,  which  has  been  diluted  to  a 
convenient  volume  in  a  Nessler  tube  or  similar  comparison  cylinder.  The  appara- 
tus used  in  determining  small  amounts  of  titanium,  lead,  etc.,  is  suitable  for  this 
test.  In  this  case  the  glowing  wire  or  filament  of  an  incandescent  light  is  viewed 
through  the  solutions,  the  brightness  of  the  wire  acting  as  a  guide  in  matching  the 
solutions. 

Sulphurous  Acid  in  Acetic  Acid 

This  is  best  detected  by  placing  in  a  small  flask  about  20  cc.  of  the  sample, 
adding  5  cc.  of  strong  hydrochloric  acid  and  about  3  grams  of  zinc  and  covering 
with  a  filter  paper  saturated  with  lead  acetate.  The  blackening  of  the  paper 
indicates  S02  in  the  sample  (e.g.,  reduced  to  H2S  by  the  hydrogen  generated  by 
the  zinc). 

The  sulphurous  acid  is  best  titrated  with  N/10  iodine  solution,  using  starch 
indicator.  1  cc.  N/10  I2=.0032  gr.  SO2. 

Hydrochloric  Acid  in  Acetic  Acid 

Determined  by  the  turbidity  test  as  in  case  of  sulphuric  acid,  silver  nitrate 
solution  being  used  to  precipitate  AgCl,  and  nitric  acid  substituted  for  hydrochloric 
acid. 

Metals  in  Acetic  Acid 

Total  Solids.  Ten  to  100  grams  of  the  acid  is  evaporated  to  dryness  in  a 
platinum  dish.  The  residue  contains  the  non- volatile  solids. 


ACETATES 

Two  to  5  grams  of  the  material  is  placed  in  a  Kjeldahl  flask  connected  by  means 
of  a  condenser  to  a  receiving  flask  containing  half  normal  caustic.  About  20  cc. 
of  85  per  cent  phosphoric  acid  are  added  and  about  150  cc.  of  water.  Gentle  heat 
is  applied  and  gradually  increased.  About  100  cc.  of  the  solution  is  distilled  into 
the  caustic.  Additional  hot  water  is  added  to  the  residue  in  the  Kjeldahl  flask 
and  the  distillation  continued.  This  is  repeated  until  about  800  cc.  of  solution 
has  been  distilled  over.  The  C02  is  boiled  out  of  the  distillate,  a  reflux  condenser 
being  used  to  prevent  loss  of  the  acetic  acid.  If  the  solution  is  alkaline,  a  known 


530  ACIDS 

amount  of  acid  is  added  and  the  C02  boiled  out.    The  excess  acid  is  now  titrated 
and  the  amount  of  acetic  acid  in  the  distillate  calculated. 

One  cc.  N/2  NaOH  =0.030015  gram  CH3COOH. 
CH,COOHXl.3169=Ca(CH,CO«),,  or  X1.3663  =CH2COONa. 

Acetates  of  the  Alkalies  and  Alkaline  Earths.  In  absence  of  other  organic 
acids,  nitrates,  etc.,  a  quick  method  is  suggested  by  Sutton  (Vol.  Analy.,  X.  Ed., 
p.  91).  The  salts  are  converted  into  carbonates  by  ignition  and  the  residue 
titrated  with  normal  acid. 

One  cc.  N/l  acid  =0.06003  gram  CH3COOH. 


CITRIC   ACID 

The  free  acid  may  be  titrated  with  sodium  hydroxide,  using  phenolphthalein 
indicator.     One  cc.  N/l  alkali  =0.07  gram  crystallized  citric  acid. 


VOLUMETRIC  ESTIMATION  OF  FREE  ACID  IN  PRESENCE  OF 

IRON  SALTS 

The  red  precipitate  formed  when  solutions  containing  iron  are  titrated  with 
caustic  makes  it  difficult  to  detect  the  end-point  of  neutralization ;  the  method  sug- 
gested lijy  C.  A.  Ahlum1  takes  advantage  of  the  white  compound  formed  by  pre- 
cipitating the  iron  as  a  phosphate  and  the  fact  that  monosodium  phosphate  is 
neutral  to  methyl-orange  indicator. 

Reactions 

Fe2(S04)3+2NaH2P04+  x  free  acid=2FeP04+Na2S04+x  free  acid+2H2S04, 
or  2FeCl3+2NaH2P04+  x  free  acid=2FeP04+2NaCl+  x  free  acid+4HCl. 

The  acid  equivalent  to  ferric  iron  is  deducted  from  the  total  acid  found,  the 
excess  acid  being  due  to  the  free  acid  in  the  solution. 

Procedure.  To  the  solution  containing  the  iron  and  free  acid  is  added  an  excess 
of  C.P.  solution  of  monosodium  phosphate  (neutral  to  methyl-orange),  and  then 
a  few  drops  of  the  indicator.  The  acidity  of  the  solution  is  now  determined  by 
titration  with  standard  caustic  in  the  usual  way,  the  solution  being  cold.  From 
this  titration  the  total  free  and  combined  acid  are  calculated. 

Iron  is  now  determined  in  a  separate  portion  by  titration  with  stannous  chloride 
or  dichromate. 

Calculation. 

(A)  Fe20,Xl.2285  =g.  H2S04  (combined).    Fe203X0.9135  =g.  HC1  (combined). 

(B)  One  cc.  N/5  NaOH  =  .00981  gram  H2S04  or  .00729  gram  HC1. 
Total  acid  (B)  minus  combined  acid  (A)  =free  acid. 

1  C.  A.  Ahlum,  The  Analyst,  31,  168,  1906. 


ACIDS  531 


ESTIMATION    OF    THE    CARBONATES    AND    HYDRATES    OF 
POTASSIUM  AND  SODIUM  WHEN  TOGETHER  IN  SOLUTION1 

Procedure.  A  measured  volume  of  the  solution  is  titrated,  using  phenolphtha- 
lein  as  indicator.  The  acid  used  is  equivalent  to  all  of  the  hydrate  and  half  the 
carbonate ;  methyl  orange  is  now  added  and  the  titration  completed ;  the  additional 
amount  of  the  acid  used  is  equivalent  to  half  the  carbonate,  therefore  the  amount 
of  acid  required  for  the  carbonates  and  for  the  hydrates  can  be  calculated  from 
these  figures. 

The  fully  neutralized  solution  is  evaporated  to  dry  ness  and  the  residue  weighed. 
The  result  is  the  weight  of  the  mixed  sulphates,  due  to  the  carbonates  and  hydrates 
of  potassium  and  soda  in  the  solution. 

Calculate  the  total  acid  required  to  its  equivalent  of  potassium  sulphate,  sub- 
tract from  this  result  the  weight  of  the  mixed  sulphates,  and  the  difference  is  due 
to  the  sodium  sulphate  in  the  mixed  sulphates,  owing  to  the  difference  in  the  molecu- 
lar weights  of  potassium  sulphate  and  sodium  sulphate.  The  whole  of  the  acid 
used  has  been  calculated  to  potassium  sulphate,  and  as  the  acid  was  neutralized 
by  carbonates  and  hydrates,  it  is  evident  the  proportion  of  total  sulphate,  due  to 
the  carbonates  and  hydrates,  is  equivalent  to  the  amount  of  the  acid  used  for  each 
respectively;  therefore  the  proportion  of  the  above  obtained  difference  due  to  the 
carbonates  and  the  hydrates  respectively  is  also  proportional  to  the  amount  of 
acid  used  for  each. 

Example.  A  solution  of  the  mixed  carbonates  and  hydrates  of  potassium  and 
sodium  required : 

(40  cc.  NaOH  :  40  cc.  KOH)  80  cc.  of  acid  to  neutralize  the  hydrates. 
(10  cc.  Na2C03  :  10  cc.  K2C03)  20  cc.  of  acid  to  neutralize  the  carbonates. 
100  cc.  total  acid  required  to  neutralize  the  solution. 

Total  acid  100  cc.  calculated  to  K2S04  =0.87  gram. 

Total  neutralized  solution  evaporated  to  dryness  (K2S04+Na2S04)  =0.79  gram. 
Difference  due  to  Na2S04  in  weighed  sulphates  =0.08  gram. 

(K2S04-Na2S04)  :  Na2S04  :  :  Diff  : 

32  :     142     :  :  0.08  :  0.355  Na2S04  present  in  the  mixed  sul- 

phates. 

And  the  mixed  sulphates  0.79  gram  —0.355  =0.435  K2S04  present  in  the  mixed 
sulphates. 

Therefore  the  mixed  sulphates  consist  of  Na2S04  0.355  gram,  K2S04  0.435  gram. 

The  proportion  of  the  acid  used  for  the  hydrates  is  80/100  and  for  the  car- 
bonates is  20/100. 

Therefore  the  proportion  of  the  difference  (0.08)  due  to  Na2S04  from  the  hydrate 
NaOH  is  0.08X80/100  =0.064.  For  the  carbonates  =0.08X20/100  =0.016. 

By  the  above  ratios  32  :  142  :  :  0.064  :  0.284  Na2S04  from  NaOH  =40  cc. 
N/10  acid.  32  :  142  :  :  0.016  :  0.071  Na2S04  from  Na2CO  =10  cc.  acid. 

1 W.  A.  Bradbury  and  F.  Owen.     C.  N.,  107,  2778,  85  (Feb.  21,  1913). 


532  ACIDS 

80  cc.  acid  used  for  the  hydrates     =0.696    K2S04. 

0.284  Na2S04  from  the  NaOH         =0.348    K2S04. 

Difference  =K2S04  from  KOH         =0.348  =40  cc.  N/10  acid. 

20  cc.  acid  used  for  the  carbonates  =0.174. 

0.071  Na2S04  from  the  Na2C08       =0.087. 

Difference  =K2S04  from  K2C03       =0.087  =  10  cc.  acid. 

The  figures  correspond  with  the  quantities  taken. 

80  cc.  of  acid  to  neutralize  the  hydrates. 
20  cc.  of  acid  to  neutralize  the  carbonates. 

f  NaOH  0.284=  40  cc.  acid) 

Na2S04= 0.355     AT  80  cc.  acid. 

[  Na2C03  0.071  =10  cc.  acid  J 

f  KOH     0.348=  40  cc.  acid  ) 

K2S04  =  0.435  I  [  20  cc.  acid 

[  K2CO,  0.087  =  10  cc.  acid  J 

Totals      0.790  0.790(a)100 

Calculate  these  sulphates  to  the  corresponding  hydrates  and  carbonates. 

The  author  acknowledges  the  assistance  rendered  by  Messrs.  J.  P.  Kelly  and  B.  S. 
Clark  by  review  and  criticism  of  this  chapter. 


WATER  ANALYSIS 

D.  K.  FRENCH 

Probably  at  no  other  time  has  the  importance  of  a  water  supply,  either  for 
domestic  or  industrial  purposes,  been  so  great,  as  in  these  early  years  of  the  twen- 
tieth century.  The  increasing  realization  of  the  effect  of  contaminating  materials, 
both  organic  and  inorganic,  on  a  municipal  or  private  drinking  supply — and 
history's  record  of  the  devastating  nature  of  epidemics  due  to  water-borne  disease 
organisms,  have  led  to  the  careful  investigation  of  water  for  its  sanitary  value 
and  the  development  of  materials  and  equipment  to  fight  and  eliminate  such 
contamination,  and  have  increased  many  hundreds  of  per  cent  the  factor  of  safety 
to  the  public  health.  In  like  manner,  and  even  to  a  greater  extent,  has  the  value 
of  water  for  industrial  uses  been  a  matter  for  careful  consideration.  It  is 
hard  for  the  public  to  realize  the  immense  quantities  of  water  used  for  industrial 
purposes,  not  only  for  the  development  of  steam  and  electric  power,  but  also  for 
purposes  of  manufacture. 

From  the  standpoint  of  power  development  we  are  familiar  with  the  heat 
losses  and  the  increased  operating  expenses  due  to  scale  formation  in  the  steam 
or  locomotive  boiler,  and  also  to  the  continued  rapid  decrease  in  valuation  of 
boiler  property,  or  of  power  plant  property,  due  to  corrosion  or  rusting.  Another 
element  of  trouble  which  is  noticed  not  so  much  in  stationary  boiler  practice  as 
in  locomotive  boiler  practice,  is  the  element  of  foaming  and  priming  of  a  water, 
which  results  in  much  more  rapidly  putting  the  steam  raiser  out  of  active  service 
than  either  of  the  other  types  of  trouble. 

From  the  standpoint  of  plant  deterioration  due  to  rusting  and  corrosion  one 
has  only  to  look  to  the  great  mass  of  works  on  the  corrosion  of  iron  and  steel  which 
are  largely  results  of  the  growing  need  for  some  information  as  to  the  cause  and 
possible  prevention  of  this  particular  phase  of  trouble. 

Little  work  has  been  done  so  far  on  the  actual  theory  of  foaming  troubles  in 
water,  although  Mr.  Stabler  of  the  United  States  Geological  Survey  considers  it 
quite  thoroughly  in  several  Government  bulletins  with  which  he  has  been  con- 
nected.1 

In  the  world  of  industry  the  action  of  a  hard  water  upon  soap  consumption 
has  been  known  for  centuries,  and  for  a  considerable  period  of  time  the  value  of 
a  water  was  determined  largely  by  the  amount  of  soap  that  it  would  consume 
and  render  insoluble.  This  same  hardness  has  a  noticeable  effect  in  the  textile 
industry,  in  bleaching  and  dyeing,  in  the  canning  industry,  especially  when  the 
water  supply  contains  such  substances  in  large  quantities.  In  the  photo- 
graphic industry  the  presence  of  chlorides  in  water  and  certain  alkalies  is  a  source 
of  considerable  trouble,  and  in  every  case,  before  any  intelligent  effort  can  be  made 
to  overcome  these  troubles,  a  complete  analysis  of  the  water  is  necessary. 

It  shall  be  our  purpose  in  the  methods  which  follow  to  give,  where  it  is  possible, 
first  a  system  of  analysis  whereby  a  complete  analysis  can  be  made,  and  to  follow 

1  Water  Supply  Paper  274  and  254  (Supplement). 
533 


534  WATER  ANALYSIS 

this  up  with  optional  methods  which,  individually,  are  equally  as  good  as  those 
occurring  in  the  system  of  analysis,  and  in  some  cases  more  satisfactory  where  the 
laboratory  has  the  required  equipment,  adding  any  special  methods  which  may 
be  found  available. 

SANITARY  ANALYSIS 

A  sanitary  analysis  consists  in  the  physical  examination  covering  turbidity, 
color,  odor  and  occasionally  taste,  the  chemical  analysis  for  total  residue,  loss 
on  ignition  and  fixed  solids,  noting,  where  possible,  the  odor  during  ignition 
and  also  noting  the  appearance  as  regards  color  of  the  residue  both  before  and 
after  ignition,  the  determination  of  free  and  albuminoid  ammonia,  nitrogen 
as  nitrite  and  nitrate,  chlorine  as  chloride  and  oxygen  consumed.  Organic  nitro- 
gen is  frequently  determined  upon  polluted  waters. 

In  sanitary  analysis  the  principal  determinations  relate  to  the  various  forms 
and  compounds  in  which  nitrogen  appears. 

Organic  Nitrogen.  The  initial  form  can  be  determined  as  such,  or  as  is 
usually  the  case  in  all  but  highly  polluted  supplies,  as  albuminoid  ammonia  which 
gives  a  very  close  approximate.  By  decomposition  the  organic  matter  first  gives 
nitrogen  as  free  ammonia,  then,  by  oxidation,  nitrogen  as  nitrites,  and  finally  the 
more  stable  form  of  nitrogen  as  nitrates  is  reached.  Conversely  the  reactions  are 
frequently  reversed  through  the  influence  of  bacteria  and  microscopic  organisms. 

Chlorine  is  determined  and  by  its  excess  over  the  normal  chlorine  of  a  general 
district  may  indicate  previous  sewage  contamination. 

Oxygen  Consumed,  or  "  oxygen  required,"  means  the  amount  which  carbo- 
naceous organic  compounds  present  consume  in  the  presence  of  potassium  perman- 
ganate and  acid.  From  these  figures  additional  evidence  is  obtained  as  to  the 
sanitary  character  of  a  water,  though  many  phases  of  interference  can  occur. 

PHYSICAL  TESTS 

For  the  physical  examination,  standards  for  turbidity  and  color  have  been 
adopted. 

Turbidity.  Turbidity  standards  are  based  on  parts  per  million  of  silica  (Si< 
suspended  in  water,  and  the  adopted  standard  is  that  of  the  United  States  G< 
logical  Survey  (A.  P.  H.  A.,  p.  4).  A  water  with  a  turbidity  of  100  is  one 
which  has  100  p.p.m.  of  silica  (Si02)  in  such  a  state  of  fineness  that  a  bright 
platinum  wire  1  mm.  in  diameter  can  just  be  seen  when  center  of  said  wire  is 
100  mm.  below  the  surface  of  the  water  and  the  observer  is  1.2  meters  above 
the  wire.  The  observation  must  be  in  open  air,  not  in  sunlight,  and  in  the  middle 
of  the  day.  Standards  are  prepared  with  precipitated  fuller's  earth  (to  pass 
200-mesh  sieve).  One  gram  to  one  liter  of  distilled  water  makes  a  stock  solution 
with  1000  turbidity.  Standards  for  comparison  are  obtained  by  dilution. 

The  Illinois  Water  Supply  Association  outlines  another  method  (Proc. 
I.  W.  S.  A.,  1914,  pp.  49-51),  whereby  a  suspension  is  prepared  by  shaking  silica 
(Si02)  or  fuller's  earth  (ground  to  pass  a  200-mesh  sieve),  settling  for  ten  hours, 
and  determining  by  evaporating  and  weighing  the  amount  of  silica  (SiOa)  in  a  given 
portion.  Standards  are  then  prepared  by  dilution. 

Color.    All  suspended  matter  should  be  removed  by  filtration.    The  standai 
designated  as  color  500  is  obtained  as  follows: 


WATER  ANALYSIS 


535 


1.246  grams  potassium  platinic  chloride  (PtCl42KCl)1  containing  0.5  gram 
of  platinum  and  1  gram  crystallized  cobalt  chloride  (CoCl26H20)  containing  0.25 
gram  cobalt  (Co),  are  dissolved  in  water  with  100  cc.  hydrochloric  acid  and  made 
to  one  liter  with  distilled  water.  This  solution  is  diluted  with  distilled  water  for 
comparative  purposes,  but  a  water  with  a  color  greater  than  70  should  be  diluted 
prior  to  comparison.  The  standards  for  observation  should  be  in  100-cc.  Nessler 
tubes  with  the  mark  20-25  cm.  above  the  bottom  and  should  be  viewed  vertically 
downwards  to  a  white  reflective  surface. 

Standard  glass  disks  are  used  by  the  United  States  Geological  Survey  2  in  place 
of  the  above  standard. 

Odor.  Observations  should  be  made  both  on  cold  and  hot  samples.  Note 
should  be  made  immediately  on  opening  containers  as  some  odors  are  very  tran- 
sient and  rapidly  disappear. 

Cold.  Shake  sample  violently  in  collecting  bottle,  same  to  be  about  half  full. 
Remove  glass  stopper  and  smell  at  neck  of  bottle. 

Hot.  Use  either  open  beaker,  400  cc.,  containing  150  cc.  sample  well  covered 
and  heated  nearly  to  boiling,  or  sealed  glass  stoppered  bottle  or  saponification 
flask,  heating  fifteen  minutes  just  under  boiling.  Allow  to  cool  slightly,  remove 
stopper,  shake  and  smell.  Designate  odor  as  aromatic,  grassy,  earthy,  musty, 
fishy,  putrid,  disagreeable,  peaty,  sweetish,  etc.  The  following  table  expressing 
intensity  of  odor  is  copied  from  the  American  Public  Health  Association  Standard 
Methods,  1913,  p.  12: 


Numerical 
Value. 

Term. 

Approximate  Definition. 

0 

None. 

No  odor  perceptible. 

1 

Very  Faint. 

An  odor  that  would  not  be  detected  ordinarily  by  the  average 
consumer,  but  that  could  be  detected  in  the  laboratory  by 
an  experienced  observer. 

2 

Faint. 

An  odor  that  the  consumer  might  detect  if  his  attention  were 
called  to  it,  but  that  would  not  attract  attention  otherwise. 

3 

Distinct. 

An  odor  that  would  be  detected  readily  and  that  might  cause 
the  water  to  be  regarded  with  disfavor. 

4 

Decided. 

An  odor  that  would  force  itself  upon  the  attention  that  might 
make  the  water  unpalatable. 

5 

Very  Strong. 

An  odor  of  such  intensity  that  the  water  would  be  absolutely 
unfit  to  drink.  A  term  to  be  used  only  in  extreme 

cases. 

Taste.  May  be  made  on  hot  and  cold  samples.  A  simple  statement  following 
largely  the  terms  applied  to  odor  in  expressing  results,  brackish,  astringent,  salty, 
sweetish,  etc. 

1  Care  should  be  taken  that  this  be  the  bright  yellow  platinic  salt,  and  not  con- 
taminated with  the  reddish  platinous  salt. 

2  App.  made  by  Builders'  Iron  Foundry,  Providence,  R.  I. 


536 


WATER  ANALYSIS 


CHEMICAL  TESTS 
Free  Ammonia 

Apparatus.     The  apparatus  for  this  determination  should  be  as  far  as  pos- 
sible free  from  joints  or  connections  that  are  subject  in  any  way  to  outside 


Angle  t  ,  j  Block  Tin 

may  be  F/      Condemer  Tube 

Vantdby  (~~)          in  On,  Piece 

Meant  of  ISU  M        from 


FIG.  85. 

contamination  or  to  decomposition.  The  apparatus  is  composed  of  a  distillation 
flask  and  a  condenser,  with  possibly  a  safety  tube  located  somewhere  near  the  flask 
to  avoid  the  possible  carrying  over  of  impurities  in  connection  with  the  steam. 


WATER  ANALYSIS  537 

Reagents.     1.  Ammonia-free  Water. 

2.  Standard  Ammonium  Chloride  Solution.    Dissolve  3.82  grams  of  ammo- 
nium chloride  in  1  liter  of  distilled  water.     Dilute  10  cc.  of  this  to  1  liter  with 
ammonia-free  water.     1  cc.  =0.00001  gram  of  nitrogen. 

3.  Nessler's  Solution.     Dissolve  50  grams  of  potassium  iodide  in  the  smallest 
possible  quantity  of  cold  water.    Add  a  saturated  solution  of  mercuric  chloride 
until  a  faint  show  of  excess  is  indicated.    Add  400  cc.  of  50%  solution  of  potassium 
hydrate.    After  same  has  clarified  by  sedimentation,  make  up  to  1  liter  with 
water,  allow  to  settle  and  decant. 

Optional  Method.  Dissolve  61.75  grams  of  potassium  iodide  in  250  cc.  of  redis- 
tilled water,  and  add  a  cold  solution  of  mercuric  chloride  which  has  been  saturated 
by  boiling  with  excess  of  salt.  Pour  in  the  mercury  solution  cautiously,  and  add  an 
amount  just  sufficient  to  make  the  color  a  permanent  bright  red.  With  a  little 
practice  the  exact  depth  of  color  can  be  easily  duplicated.  It  will  take  a  little  over 
400  cc.  of  the  mercuric  chloride  solution  to  reach  this  end-point.  Dissolve  the  red 
precipitate  by  adding  exactly  .75  gram  of  potassium  iodide.  Then  add  150  grams 
of  potassium  hydrate  dissolved  in  250  cc.  of  water.  Make  up  to  1  liter.  Mix 
thoroughly  and  allow  the  precipitate  formed  to  settle.  Pour  off  the  supernatant 
liquid.  Mercuric  chloride  increases  the  sensitiveness  and  potassium  iodide  decreases  it. 

Operation.    Clean  apparatus  thoroughly  as  follows: 

Fill  a  flask,  which  for  most  satisfactory  results  should  be  an  800-cc.  Kjeldahl 
flask,  with  500  cc.  of  distilled  water.  Add  a  pinch  of  c.p.  sodium  carbonate  and 
distill  first  of  all  with  no  running  water  in  the  condenser  jacket  until  free  steam 
blows  through  the  apparatus.  Then  turn  on  condenser  water  and  distill  off 
approximately  250  cc.,  testing  the  last  50  cc.  with  Nessler's  solution,  and  this 
portion  should  not  show  color  in  fifteen  minutes'  time.  The  flask  is  then  emptied 
of  the  remaining  water,  500  cc.  of  the  water  to  be  analyzed  placed  therein,  and 
if  acid,  neutralized  with  c.p.  sodium  carbonate.  A  slight  excess  hurries  the 
ammonia  liberation  but  also  tends  to  cause  bumping.  The  distillation  is  then 
started,  distilling  6  cc.  to  10  cc.  per  minute,  and  three  separate  portions  of  50  cc. 
each  are  caught  in  Nessler  jars.  After  150  cc.  is  distilled  the  flame  should  be 
removed.  To  each  50-cc.  portion  add  2  cc.  Nessler's  solution  and  after  ten 
minutes'  standing  compare  with  standards  from  the  standard  ammonium  chloride 
solution. 

Albuminoid  Ammonia 

Reagent.  1.  Alkaline  Potassium  Permanganate.  Dissolve  200  grams  of 
potassium  hydrate  and  8  grams  c.p.  potassium  permanganate  in  1250  cc.  of 
water,  boil  down  to  1  liter  and  bottle  while  still  warm. 

Operation.  Add  50  cc.  alkaline  potassium  permanganate  solution  and  several 
pieces  of  washed  and  ignited  pumice  to  the  water  remaining  in  the  flask  from  the  free 
ammonia  determination  and  continue  the  distillation,  taking  off  four  or  five 
separate  portions  of  50  cc.  each  in  Nessler  jars.  Add  2  cc.  Nessler's  solution 
to  each  and  after  ten  minutes  standing  compare  color  with  standard  as  in  the  free 
ammonia  determination. 

Organic  Nitrogen 

While  this  determination  is  not  usually  made  we  give  it  for  the  sake  of  com- 
pleteness. 

The  portion  of  sample  from  the  free  ammonia  determination,  or  a  new  por- 
tion freed  from  free  ammonia  by  distillation,  is  acidified  with  5  cc.  C.P.  sulphuric 


538 


WATER  ANALYSIS 


acid  (nitrogen-free)  and  digested  in  a  hood  until  colorless  and  H2S04  fumes  are 
given  off.  A  little  ignited  pumice  will  guard  against  bumping.  Remove  from 
flame,  add  potassium  permanganate  in  small  portions  until  a  heavy  greenish 
precipitate  persists,  cool,  dilute  with  ammonia-free  water,  neutralize  with  10% 
Na2CO3  solution  (NH3  free),  distill  into  Nessler  tubes  and  compare  as  in  free  and 
albuminoid  ammonia. 

Permanent  standards  l  can  be  made  using  potassium  platinic  chloride,  2  grams 
dissolved  in  water,  100  cc.  strong  hydrochloric  acid  and  made  to  1  liter;  and 
cobalt  solution,  12  grams  cobaltous  chloride  (CoCl2  6H20)  dissolved  in  distilled 
V  ;ter,  100  cc.  strong  hydrochloric  acid  added  and  made  to  1  liter.  The  follow- 
ing table  represents  the  amounts  used,  to  be  made  to  50  cc.  with  distilled  water 
in  Nessler  tubes-  for  comparison,  the  150-cc.  mark  being  20-25  cm.  above  the 
bottom,  but  should  be  checked  against  Nesslerized  standards  and  the  Nessler 
solution  modified,  if  necessary,  until  the  standards  agree.  This  is  accomplished 
by  varying  the  amounts  of  potassium  iodide  and  mercuric  chloride. 


Equivalent  Volume 
of  Standard 
Ammonium  Chloride, 
cc. 

Platinum  Solution, 
cc. 

Cobalt  Solution, 
cc. 

0.0 

1.2 

0.0 

0.1 

1.8 

0.0 

0.2 

2.8 

0.0 

0.4 

4.7 

0.1 

0.7 

5.9 

0.2 

1.0 

7.7 

0.5 

1.4 

9.9 

1.1 

1.7 

11.4 

1.7 

2.0 

12.7 

2.2 

2.5 

15.0 

3.3 

3.0 

17.3 

4.5 

3.5 

19.0 

5.7 

4.0 

19.7 

7.1 

4.5 

19.9 

8.7 

5.0 

20.0 

10.4 

6.0 

20.0 

15.0 

7.0 

20.0 

22.0 

Nitrogen  as  Nitrite 

Reagent.     1 .  Sulphanilic  Acid.    Dissolve  8  grams  of  the  acid  in  1  liter  of  acetic 
acid,  specific  gravity  1 .04.    This  is  practically  a  saturated  solution  and  keeps  well. 

2.  Naphthylamine  Acetate.     Dissolve  5  grams  of  a-naphthylamine  in  1  liter 
of  acetic  acid,  specific  gravity  1.04,  and  filter  through  absorbent  cotton  (previ- 
ously washed). 

NOTE.     A  slightly  pink  color  resulting  on  standing  does  not  materially  interfere 
with  the  use  of  this  solution. 

3.  Sodium  Nitrite  Solution.    Dissolve  1.1  grams  of  silver  nitrite  in  nitrite-free 
water.    Precipitate  the  silver  with  sodium  or  potassium  chloride  solution  and  dilute 

1  Permanent  Standards  (Jackson,  Tech.  Quart.,  1900,  vol.  13,  p.  320.) 


WATER  ANALYSIS 


539 


to  1  liter.  Dilute  100  cc.  of  this  solution  to  1  liter  and  then  10  cc.  of  this  second 
solution  to  1  liter  with  sterilized  nitrite-free  water,  adding  1  cc.  of  chloroform 
and  holding  in  a  sterilized  bottle.  1  cc.  =0.0001  milligram  of  nitrogen. 

Operation.  Take  100  cc.  of  the  water  after  nitration  and  clarification, 
preferably  with  aluminum  hydrate,  to  remove  possible  suspended  iron  and  ma- 
terial which  might  interfere  with  color  production.  Add  2  cc.  each  of  solutions 
No.  1  and  No.  2.  After  ten  minutes'  standing  compare  with  standards  made  up 
from  the  standard  sodium  nitrite  solution  (No.  3). 

Permanent  Standards 

Cobalt  Solution.  Dissolve  24  grams  of  cobaltous  chloride  (CoCl2  •  6H20)  in 
distilled  water,  add  100  cc.  of  strong  hydrochloric  acid  and  make  up  to  one  liter 
with  distilled  water. 

Copper  Solution.  Dissolve  12  grams  of  dry  cupric  chloride  (CuCl2-2H20) 
in  distilled  water,  add  100  cc.  of  strong  hydrochloric  acid  and  make  up  to  one  liter 
with  distilled  water. 

The  standards  are  used  in  100-cc.  tubes  with  the  mark  12-14  cm.  above  the 
bottom.  The  following  table  gives  the  proportions  of  each  solution  to  be  made 
up  to  100  cc.: 


cc.  Cobalt  Solution. 

cc.  Copper  Solution. 

p.p.m.  Nitrite  per 
100  cc.  of  Water. 

.0 

.0 

.000 

1.1 

1.1 

.001 

3.5 

3.0 

.003 

6.0 

5.0 

.005 

12.5 

8.0 

.010 

The  solutions  to  use  for  100  cc.  of  water  are  the  old  ones,  as  follows:  1  cc. 
of  hydrochloric  acid  (1  :  4),  2  cc.  of  sulphanilic  acid  (8  grams  per  liter),  and 
finally  2  cc.  of  naphthylamine  hydrochloride  (8  grams  per  liter  with  10  cc.  of 
strong  hydrochloric  acid),  and  allow  color  to  develop  twenty  minutes. 

NOTE.  Volume  28,  page  742,  J.  Soc.  Chem.  Ind.,  calls  attention  to  the  possibility 
of  a  permanent  standard  composed  of  a  solution  of  acid  magenta  (fuchsine-S,  acid 
fuchsine  according  to  Weigert).  According  to  this  article,  0.2  of  a  gram  of  this  dye 
is  dissolved  in  50  cc.  of  2/N  HC1  and  made  up  to  2000  cc.  with  distilled  water.  Of 
this  solution  200  cc.  are  mixed  with  50  cc.  of  2/N  HC1  and  again  diluted  to  2000  cc. 
with  distilled  water.  From  this  latter  solution  standard  solutions  can  be  prepared 
containing  various  quantities,  these  standards  being  made  up  to  200  cc.  with  distilled 
water  after  the  addition  cf  5  cc.  of  2/N  HC1.  Considerable  work  is  being  done  on  this, 
but  the  standards  have  not  yet  been  accepted  in  this  country.  However,  standards 
can  be  made  by  matching  these  solutions  against  standards  prepared  in  the  usual  way 
and  their  permanence  is  much  greater  than  such  standards. 

Nitrogen  as  Nitrate 

Phenolsulphonic  Acid  Method 

Reagent.  1.  Phenolsulphonic  Acid.  Dissolve  25  grams  of  pure  white  phenol 
in  150  cc.  of  pure  concentrated  sulphuric  acid,  add  75  cc.  of  fuming  sulphuric 
acid  (13%  S08),  stir  well  and  heat  for  two  hours  at  about  1000.1 

1  Jour.  Amer.  Chem.  Soc.,  33,  382,  1911. 


540  WATKR  ANALYSIS 

2.  Ammonium  Hydrate  1-1. 

3.  Sodium  Carbonate.    10%  solution  of  anhydrous  Na2C03. 

4.  Standard  Nitrate  Solution.    Dissolve  0.72  gram  pure  or  C.  P.  potassium 
nitrate  in  1  liter  of  distilled  water.    Evaporate  carefully  10  cc.  of  this  solution 
on  water  bath,  moisten  thoroughly  with  2  cc.  of  solution  No.  1  and  dilute  to  1 
liter.     1  cc.  of  this  =0.001  milligram  of  nitrogen. 

Determination.  Carefully  evaporate  100  cc.  of  water  after  the  addition  of 
2  cc.  of  sodium  carbonate  solution.  After  this  evaporate  to  dryness,  cool  and 
add  2  cc.  phenolsulphonic  acid  (No.  1),  mixing  well  with  a  glass  rod.  Dilute 
with  25  cc.  of  distilled  water  and  add  an  excess  of  ammonium  hydrate,  making 
up  to  100  cc.  volume  with  distilled  water. 

The  dilute  solution  is  then  compared  with  the  standard  solution. 

NOTES.  When  the  chlorides  are  over  100  parts  per  million  in  the  original  sample 
they  should  be  removed  with  the  addition  of  silver  sulphate  in  the  solid  form  and  the 
water  should  be  filtered  prior  to  evaporation.  It  is  for  this  reason  that  ammonium 
hydrate  is  used  to  develop  the  color  instead  of  potassium  hydrate,  which  is  frequently 
recommended,  as  a  slight  excess  of  silver  sulphate  will  result  in  a  dirty  precipitate  when 
using  potassium  hydrate,  whereas  the  use  of  ammonia  has  no  effect.  Furthermore, 
the  filtration  of  a  turbid  nitrate  solution  does  not  result  in  a  satisfactory  color,  as 
would  be  the  case  without  filtration. 

Permanent  standards  can  be  made  by  procedure  given  on  page  539,  or  standards 
can  be  made  using  tripotassium  nitrophenoldisulphonate.  The  following  method  is 
given  in  an  article  in  the  J.  Amer.  Chem.  Soc.,  Vol.  33,  pp.  381-384: 

The  theoretical  amount  of  powdered  potassium  nitrate  is  added  to  the  disulphonic 
acid  regent  in  small  pinches  at  a  time  (for  each  cc.  of  reagent  0.1076  gram  KNO3), 
stirring  thoroughly  after  each  addition.  The  product  is  then  diluted,  treated  with 
dry  barium  carbonate  to  a  deep  yellow  color,  filtered  and  the  precipitate  washed  with 
boiling  water  to  remove  the  barium  salt  which  is  but  slightly  soluble  in  cold  water.  This 
extraction  must  be  thorough.  Filtrates  and  washings  are  united,  the  barium  removed 
by  the  addition  of  potassium  carbonate  until  alkaline,  the  solution  filtered  and  the 
filtrate  concentrated  and  crystallized.  The  solution  may  then  be  easily  purified  by 
crystallization.  In  preparing  the  standards,  however,  solutions  made  from  known 
amounts  of  nitrate  standards  will  match  up  with  this  recrystallized  solution,  and  by 
means  of  proper  dilutions  the  series  of  standards  can  be  made.  Standards  made  this 
way  will  last  for  many  months,  whereas  standards  made  from  the  standard  nitrate 
solution  are  apt  to  lose  value  in  a  month's  period  and  should  be  made  up  very  frequently. 

Optional  Method  —  Aluminum  Reduction  l 

Reagents.  1.  Sodium  or  Potassium  Hydrate  Solution.  Dissolve  250  grams 
of  the  hydrate  in  1250  cc.  of  distilled  water,  add  several  strips  of  aluminum  foil 
and  allow  action  to  pass  overnight.  Boil  down  to  1  liter. 

2.  Aluminum  Foil.  Use  strips  of  pure  aluminum  approximately  10  cm.  long, 
9  mm.  wide,  and  3  mm.  thick,  same  to  weigh  a-tiout  £  gram. 

Opergfcon.  100  cc.  of  water  is  placed  in  a  30Q-ec.  casserole.  Add  2  cc.  of  the 
hydraj^^lution  and  boil  down  to  about  20  cc.  i*  r  >  he  contents  of  the  casserole 
into  at  test-tube  about  6  cm.  longjindtf  cm.  in  diameter  and  of  approximately  100-cc. 
capacity.  Rinse  the  casserole  several  times  with  nitrogen-free  water  and  add  the 
rinse  water  to  that  already  in  the  tube,  thus  making  the  contents  of  the  tube 
approximately  75  cc.  Add  a,  strip  of  aluminum  foil.  Close  the  tube  by  means 
of  a  rubber  stopper  through  \\Vich  passes  a  A-shaped  glass  tube  about  5mm. 
in  diameter.  Make  the  short  end  of  the  tube  flush  with  the  lower  side  of  the 


iv.  of  Illinois  Bull.  Water  Survey,  Series  7,  p.  14,  1909;    Amer.  Jour.  Pub. 
Hygiene,  19,  536,  1909. 


WATER  ANALYSIS  541 

rubber  stopper  while  the  other  end  extends  below  the  surface  of  distilled  water 
contained  in  another  test-tube.  This  apparatus  serves  as  a  trap  through  which 
the  evolved  hydrogen  escapes  freely.  The  amount  of  ammonia  escaping  into 
the  trap  is  slight  and  may  be  neglected.  Allow  the  action  to  proceed  for  a  mini- 
mum period  of  four  hours,  or  overnight.  Pour  contents  of  the  tube  into  a  distil- 
ling flask,  dilute  with  250  cc.  of  ammonia-free  water,  distill  and  collect  in  Nessler 
tubes  and  Nesslerize.  When  the  nitrate  content  is  high,  collect  the  distillate  in 
a  200-cc.  flask  and  Nesslerize  an  aliquot  portion.  If  the  supernatant  liquid  in 
the  reduction  tube  is  clear  and  colorless,  the  solution  may  be  diluted  to  a  definite 
volume  and  an  aliquot  part  Nesslerized  without  distillation. 

NOTE.  Where  the  nitrates  are  very  high,  from  50  parts  per  million  up,  note 
additional  method  given  under  the  head  of  Nitrate  Determination  in  Mineral  Analysis 
of  Water. 

Oxygen   Consumed 

Reagents.  1.  Standard  Potassium  Permanganate  Solution.  Dissolve  0.4 
gram  C.P.  salt  in  1  liter  of  distilled  water.  1  cc.  is  equivalent  to  0.1  milligram 
available  oxygen. 

2.  Standard  Ammonium   Oxalate   Solution.     Dissolve    0.888    gram    C.P. 
ammonium  oxalate  in  1  liter  of  distilled  water.     1  cc.  is  equivalent  to  0.1  milli- 
gram of  oxygen.     The  standard  permanganate  solution  must  be  standardized 
against  the  ammonium  oxalate  solution. 

3.  Dilute  Sulphuric  Acid  1-3. 

Operation.  100  cc.  of  water  are  measured  into  a  450-cc.  Erlenmeyer  flask,  acid- 
ified with  5  cc.  dilute  sulphuric  acid.  Ten  cc.  of  standard  permanganate  solution 
is  run  in  from  a  burette  and  the  flask  is  placed  in  a  bath  of  boiling  water,  the  level  of 
which  is  above  the  level  of  the  flask  contents,  for  thirty  minutes.  Remove.  Add 
10  cc.  of  standard  oxalic  solution  and  then  determine  the  excess  with  the  standard 
permanganate  solution.  -Deduct  from  the  total  permanganate  solution  used  the 
10  cc.  of  oxalic  acid,  and  the  remainder  represents  oxygen  consumed.  For  par- 
ticularly bad  waters  smaller  quantities  of  the  sample  are  taken  and  diluted  to 
100  cc.,  as  it  is  undesirable  at  any  time  in  the  course  of  boiling  that  the  pink 
color  of  permanganate  be  completely  discharged. 

Chlorine  as  Chlorides 

Reagents.  Standard  Salt  Solution.  16.48  grams  fused  C.P.  sodium  chloride 
are  dissolved  in  1  liter  of  distilled  water.  100  cc.  of  this  solution  diluted  to 
1  liter  gives  a  standard  solution,  each  cc.  of  which  contains  ,.001  gram  of  chlorine. 

Standard  Silver  Nitrate  Solution.  4.8  grams  dried  silver  nitrate  crystals 
are  dissolved  in  one  liter  of  distilled  water.  Each  cc.  of  this  solution  is  equiva- 
lent to  approximately  .001  gram  of  chlorine,  standardized  against  the  Standard 
Salt  Solution. 

NOTE.  N/50  solutions  of  both  sodium  chloride  and  silver  nitrate  can  be  used 
where  it  is  inconvenient  to  make  too  many  standard  solutions,  using  the  proper  factors. 

Potassium  Chromate.    Ten  per  cent  solution  neutral  potassium  chromate. 

NOTE.  A.  P.  H.  A.,  page  43,  recommends  5  per  cent  solution  of  neutral  potassium 
chromate,  adding  after  solution  of  the  crystals  in  a  few  cc.  of  water,  sufficient  silver 
nitrate  to  produce  a  slight  red  precipitation.  This  is  filtered  off,  and  the  nitrate 
made  up  to  volume. 


542  WATER  ANALYSIS 

Operation.  100  cc.  of  the  sample  are  titrated  with  silver  nitrate  solution, 
using  1  cc.  of  the  potassium  chromate  as  indicator  to  the  first  persistence  of 
the  silver  chromate  red.  Subtract  0.2  cc.  blank  from  the  reading.  A  white 
porcelain  dish  or  casserole  is  the  preferable  container,  although  a  flint-glass  beaker 
over  a  white  porcelain  plate  may  be  used.  Where  a  chlorine  is  high  and  more 
than  15  cc.  of  silver  nitrate  is  used,  a  smaller  sample  (50  cc.  or  25  cc.)  should  be 
taken  and  distilled  water  added  to  bring  the  volume  up  to  approximately  lOO 
If  the  original  water  is  noticeably  colored,  25  to  30  by  standard,  it 
decolorized  by  adding  precipitated  aluminum  hydrate,  bringing  to  a  boil  and 
filtering.  Titration  must  always  be  made  in  the  cold,  however. 

NOTE.  Precipitated  aluminum  hydrate  is  prepared  by  dissolving  potash  alum  in 
water,  precipitating  by  adding  carefully  ammonia  and  washing  in  a  large  jar  with 
distilled  water,  by  decantation,  until  free  from  chlorine,  ammonia,  and  nitrites.  An 
acid  water  should  first  be  neutralized  with  sodium  carbonate  and  a  water  containing 
free  hvdrates  should  be  neutralized  with  sulphuric  acid.  Where  specially  accurate 
work  Is  desired,  observations  may  be  made  in  a  dark  room  with  a  yellow  light. 
(A.  P.  H.  A.,  page  44.)  A  yellow  photographic  glass  may  be  used  in  daylight  and  at 
night  the  ordinary  carbon  filament  electric  light. 

Total   Solid  Residue 

Evaporate  50  cc.  to  dryness,  in  a  platinum  dish,  at  about  270°  Fahr.,  and 
bake  for  at  least  30  minutes  at  that  temperature.  An  ordinary  water-bath 
temperature  will  not  remove  water  of  crystallization  from  alkali  sulphates  or 
calcium  sulphate.  Where  water  is  high  in  magnesium  salts,  as  determined  in 
mineral  analysis,  the  water-bath  temperature  is  more  satisfactory,  due  to  the 
readiness  with  which  magnesium  chloride  and  frequently  magnesium  carbonate 
will  decompose  to  oxide.  As  a  rule,  however,  a  temperature  from  240°  to  270° 
meets  most  of  the  conditions. 

Weight  to  tenths  of  milligram  times     1168=grs.  per  gal.  total  solids. 
Weight  to  tenths  of  milligram  times  20,000  =  parts  per  million  total  solids. 

Residues  from  acid  waters  should  be  ignited  to  a  dull  red  heat  after  addition 
of  a  drop  or  so  of  sulphuric  acid,  to  insure  complete  removal  of  the  acid  itself, 
which  will  not  go  off  at  the  temperature  stated.  This  will  result  in  the  decom- 
position of  all  iron  compounds  to  the  oxide  form,  and  will  fix  all  salts,  lime,  mag- 
nesium, sodium  and  potassium,  in  the  sulphate  form,  and  correction  should  be 
made  for  chlorides  present,  which  would  be  converted  into  sulphate. 

Waters  high  in  magnesium  salts  should  be  evaporated  at  the  first  specified 
temperature,  adding,  however,  a  few  cc.  of  50  normal  sodium  carbonate 
solution  to  insure  a  slight  excess  of  sodium  carbonate,  correcting  for  the  weight 
of  sodium  carbonate  added.  Where  the  waters  contain  much  organic  matter 
after  weighing,  they  may  be  very  gently  ignited  at  a  very  dull  red  heat  until  the 
carbon  has  been  burned  off.  After  cooling,  the  residue  may  be  recarbonated  with 
tested  ammonia  carbonate  solution,  and  again  dried  in  the  usual  way.  The  differ- 
ence in  weight  after  titrating  for  possible  loss  of  chlorides,  due  to  volatilization, 
gives  a  close  approximation  of  the  organic  matter  present.  Similarly,  waters  high 
in  magnesium  chloride  or  nitrate  compounds  may  be  evaporated  with  a  few 
drops  excess  of  sulphuric  acid,  and  ignited  to  a  dull  red  heat,  the  residue  being 
compared,  where  a  complete  analysis  is  made,  with  the  sum  of  all  bases  calculated 
to  the  sulphate  form.  This  is  .sometimes  more  convenient  and  satisfactory  than 
the  evaporation  with  excess  sodium  carbonate. 


WATER  ANALYSIS  543 


INTERPRETATION   OF  RESULTS 

The  interpretation  of  the  results  of  a  sanitary  water  analysis  is  largely  a  matter 
of  experience,  and  it  is  impossible  to  lay  down  hard  and  fast  rules  covering  this 
one  matter.  It  is,  however,  possible  to  sum  up  the  meanings  of  the  various 
determinations  made,  as  each  determination  has  some  bearing  upon  the  sanitary 
condition. 

In  physical  data  the  turbidity  refers  to  insoluble  matter  in  suspension.  In 
many  cases  it  is  perfectly  harmless,  although  less  attractive,  and  frequently 
suggests  contamination,  which  is  as  apt  to  be  present  as  not.  High  turbidities, 
following  rain  storms  or  lake  over-turnings,  are  usually  accompanied  by  B.  coli, 
the  intestinal  organism,  in  considerable  quantity.  The  turbid  waters  of  the 
West  may  cause  stomach  trouble  until  a  person  is  accustomed  to  them.  Color 
is  due,  usually,  to  an  extract  of  vegetable  or  organic  matter,  or  to  iron  salts, 
and  in  itself  has  no  value  save  suggesting  organic  contamination.  Highly  colored 
water  may  have  an  astringent  taste,  and  is  not  looked  upon  with  favor  by  the 
consumer.  It  may  cause  corrosion  in  pipes  and  boilers. 

Various  organic  matters  are  in  no  way  determined  in  this  analysis,  the  results 
obtained  being  simply  indications  of  certain  cycles  in  decomposition  of  nitro- 
genous material,  as  no  decomposition  can  take  place  without  some  resulting 
nitrogen  compound.  Free  ammonia  represents  the  first  stage  in  this  decom- 
position, and  represents  the  amount  of  organic  matter  present  in  a  partially 
decomposed  and  decomposing  state.  Deep  wells  in  glacial  drift  frequently  also 
contain  high  ammonia,  however,  which  would  in  no  way  suggest  active  con- 
tamination. 

Albuminoid  ammonia  represents  organic  substances  in  an  undecomposed  state, 
which  will,  however,  decompose  under  the  proper  conditions.  The  presence  of 
nitrogen  in  such  combination  in  large  amount  usually  suggests  the  presence 
of  pollution  of  a  sewage  character.  However,  its  presence  usually  accompanies 
and  varies  in  amount  with  the  color  and  with  the  microscopic  organisms. 

The  next  stage  in  the  cycle  is  nitrogen  as  nitrites,  indicating  that  decom- 
position is  actively  progressing.  Nitrite  in  surface  water  may  indicate  con- 
tamination when  in  considerable  quantity,  but  in  ground  water  is  absolutely  of 
no  significance.  (Proc.  Am.  W.  W.  Assoc.,  1908,  page  323.)  Its  presence  is 
due  to  the  action  of  certain  types  of  bacteria  either  as  a  product  of  oxidation 
from  free  ammonia  or  as  a  product  of  reduction  from  nitrate.  Ferrous  com- 
pounds have  also  a  bearing  on  such  reduction. 

The  final  state  of  decomposition  is  nitrogen  as  nitrate.  This  indicates  the 
fact  that  at  some  time  in  the  past  organic  matter  has  been  present.  Its  presence 
indicates  a  purified  water.  In  large  amounts  it  may  cause  itching  in  sensitive 
persons.  It  is  an  important  cause  of  corrosion  in  pipes  and  boilers. 

The  oxygen  consumed  represents  the  amount  of  oxygen  required  to  oxidize 
organic  matter  already  in  the  water.  It  has  a  bearing  upon  the  organic  matter, 
but  there  are  many  inorganic  substances  which  also  discharge  the  color  of  the 
permanganate  solution,  and  the  result  should  always  be  considered  in  the  presence 
of  the  other  determinations. 

Chlorine  as  chlorides,  if  above  the  normal  figure  for  any  definite  location, 
is  a  fairly  good  indication  of  sewage,  as  it  is  one  of  the  most  constant  and  prin- 
cipal constituents  of  sewage. 

The  total  residue  itself  should  not  be  too  high,  as  an  excess  of  inorganic 


544 


WATER  ANALYSIS 


materials  would  stamp  the  water  unfit  from  an  industrial  point  of  view,  and  also, 
from  the  standpoint  of  the  individual,  might  make  it  unsatisfactory  as  a  drinking 
supply,  for  daily  consumption. 

With  reference  to  standards  of  purity,  it  is  impossible  to  make  absolute 
standards.  We  quote  a-^i  matter  of  interest  a  table  published  by  the  State  of 
Illinois,  giving  their  suggested  limits  of  impurities  for  supplies  in  that  State. 
(The  remarks  which  follow  are  those  of  the  State  Geological  Survey.) 


Lake 
Michigan. 

Streams. 

Springs 
and 
Shallow 
Wells. 

Deep  Drift 
Wells. 

Deep  Rock 
Wells. 

Turbidity 

None 

10 

None 

None 

Color 

None 

2* 

None 

None 

None 

Odor. 

None 

None 

None 

None 

None 

Residue  on  Evaporation.  .  . 
Chlorine  

150. 
4.5 

300. 
6 

500. 
15 

500. 
15 

500. 
5  -100 

Oxygen  consumed  

1.6 

5 

2 

2  -5 

2  -5 

Nitrogen  as: 
Free  Ammonia  

.01 

.05 

02 

02-3 

02-3 

Albuminoid  Ammonia.  .  . 
Nitrites 

.08 
000 

.15 

000 

.05 
000 

.20 
005 

.15 

000 

Nitrates 

04 

5 

2  00 

50 

5 

Alkalinity  

120. 

200. 

300 

300 

300 

Bacteria  per  cc  

100. 

500 

500 

100 

100 

Colon  bacillus  in  one  cc..  .  . 

Absent 

Absent 

Absent 

Absent 

Absent 

*Modified  Nessler  or  Natural  Water  Standard  equal  26  p.p.m.  platinum  scale. 

The  formation  of  a  reasonable  and  just  opinion  regarding  the  wholesomeness  of  a 
water  requires  that  there  be  taken  into  consideration  all  the  data  of  the  analysis, 
together  with  the  history  of  the  water;  the  nature  of  the  source;  character  of  the  soil 
and  earth  or  rock  strata,  and  the  surroundings.  The  interpretation  of  results  is  a  task 
for  the  expert. 

Chlorine  is  the  most  permanent  element  shown  in  water  analysis,  as  it  is  never 
removed  from  water  by  any  changes  or  processes  of  purification.  Salt  deposits,  how- 
ever, in  the  soil  must  also  be  taken  into  consideration. 


WATER  ANALYSIS 


545 


MINERAL  ANALYSIS 


Outline  of  Procedure 

50  cc.  (Certified  pipette  or  burette)  evaporated  to  dryness  at  270°  F.  in  weighed 
platinum  dish.  Increased  weight  of  dish  represents  total  solid  residue. 
(Can  be  used  for  SO4  when  sample  is  small.)  Ignite  for  organic  loss. 

250  cc.  Titrate  with  N/10  acid  or  alkali  for  alkalinity  or  acidity.  (Can  be  re-used 
to  make  up  volume  of  500-cc.  portion  when  water  sample  is  small.)  Methyl 
orange  indicator. 

100  cc.  Titrate  with  N/10  AgNO3  for  chlorine. 

100  cc.  Acidify,  boil,   precipitate  with  BaCl2,  filter  and  weigh  for  total  sulphate. 

(Use  nitrate  for  Na  and  K  when  necessary.) 

100  cc.  Add  2  cc.  10%  Na2CO3,  evaporate  to  dryness,  add  phenolsulphonic  acid,  dilute, 
then  excess  of  NH4OH  for  total  nitrate. 


500  cc.  Evaporate  to  dryness  (with  a  few  cc.  concentrated  HC1  when  very  -accurate 
SiO2  figure  is  necessary)  in  No.  8  R.  B.  dish.     Bake  30 
boiling  HC1  (concentrated),  dilute  and  filter. 


Precipitate  is  SiO2 
and   silicate   im- 
purities        'i[also 
BaSO4).     Unless 
great  accuracy  is 
necessary,    it 
should         be 
weighed  as  such, 
otherwise      SiO2 
can  be  removed 
by  HF1  and  cor- 
rection made. 

Filtrate.     Add  a  few  drops  of  HNOs,  concentrate  to  50  cc.,  cool, 
add  NH4OH,  boil  and  filter. 

Precipitate  (Fe,Al, 
Phos.)  may  be  re- 
ported as  such  or 
as    Fe    and     Al 
after   Qual.    test 
for  phosphate  has 
shown  same  to  be 
absent.       Other- 
wise both  Fe  and 
Phos  should    be 
determined     and 
weight  corrected. 

Filtrate.     Boil  and  add  saturated  Am.  Oxalate 
drop  by  drop,  boil  and  filter. 

Prec.  Ca  as 
oxalate, 
dry,  ignite 
and  weigh 
as    CaCO3 
or  CaO. 

Filtrate  Mg  (and  Mn)  add  50  cc 
concentrated  Sod.  Phos.  Solu- 
tion, then  50  cc.  NH4OH,  stir 
well  2   minutes,   or  more,   let 
stand  4  hours,  or  more,  filter 
and  wash  with    3%    NH4OH. 
Ignite    and  weigh    (determine 
Mn     separately     and     correct 
when  necessary. 

NOTE.  For  industrial  purposes  the  original  addition  of  HC1  is  not  always 
necessary  and  correction  for  BaSO4  Phos.  Mn  and  separation  of  Fe  and  Al  can 
be  dispensed  with  unless  there  is  cause  to  suspect  one  to  be  present  in  material 
amounts. 


546  WATER  ANALYSIS 

In  the  matter  of  mineral  analysis  of  water,  it  is  not  so  hard  to  obtain  a  com- 
plete analysis  of  the  water,  including  the  non-incrusting  or  "  nearly  always  " 
soluble  materials  as  well  as  the  incrusting  materials,  as  it  is  to  make  numberless 
individual  or  independent  tests,  in  the  hope  of  drawing  conclusions  from  same. 
The  scheme  of  analysis  which  follows  is  used  exclusively  in  the  writer's  labora- 
tories, and  when  carried  out  as  given,  makes  it  possible  to  complete  analysis  of  a 
water,  or  a  group  of  waters  numbering  up  to  ten,  in  the  period  of  eight  hours 
elapsed  time,  or  twenty-four  hours,  assuming  the  work  is  arranged  in  such  a  way 
that  the  magnesia  precipitates  are  allowed  to  stand  overnight  before  filtration. 
On  another  page  will  be  found  a  skeleton  form  for  this  complete  analysis,  and 
this  skeleton  will  serve  as  a  rough  guide  to  the  more  extended  discussion  which 
will  follow. 

The  complete  analysis  considers  the  quantitative  determinations  of  silica, 
iron  and  aluminum,  calcium,  magnesium,  sodium  and  potassium,  as  bases,  and 
carbonate,  hydrate,  nitrate,  sulphate,  chloride,  and  phosphate,  as  radicals  or 
acids,  with  suggested  methods  for  manganese,  ammonia,  barium,  and  other 
materials  which  might  possibly  be  present. 

Prior  to  the  starting  of  the  analysis,  the  physical  characteristics  of  the  water 
should  be  noted,  turbid  waters  should  be  filtered,  the  suspended  matter  analyzed 
separately  when  necessary,  and  the  amount  determined  either  by  nitration  and 
weighing  of  the  separated  material  (alundum  cones  are  very  satisfactory),  or 
by  the  difference  between  two  residues,  one  of  which  represents  the  original  water 
and  one  the  filtered  water.  The  mineral  analysis  should  represent  the  filtered 
supply.  This  is  due  to  the  difficulty  of  getting  uniform  samples  with  suspended 
matter  at  different  times. 

Silica,  Iron,  Aluminum,  Calcium,  Magnesium 

(Manganese,  Phosphoric  Acid) 

NOTE.  If  from  qualitative  observations  the  water  contains  considerable  mineral 
matter,  smaller  quantities  varying  from  100  to  250  cc.  may  be  taken,  or  if  the  sample 
is  apparently  distilled  or  condensed  and  contains  very  little  mineral  matter,  1000  cc. 
should  be  taken,  the  object  being  to  obtain  a  residue  neither  too  large  nor  too  small. 
0.4  to  0.6  gram  is  a  good  quantity  to  work  on. 

Silica 

Evaporate  over  free  flame,  then  on  £-in.  asbestos  board,  to  dryness,  500  cc. 
original  water,  using  a  No.  8  porcelain  dish.  Bake  at  110-130°  C.  or  on 
asbestos  plate  over  flame  for  one-half  hour.  Moisten  with  10  cc.  concentrated 
HC1,  add  50  cc.  of  water,  boil  fifteen  to  thirty  seconds  and  filter.  Wash  with  hot 
water. 

NOTE.  For  great  accuracy,  evaporate  twice  to  dryness  as  above,  with  the  addition, 
prior  to  the  sample  going  to  dryness,  of  10  cc.  HC1,  allow  to  bake  as  above,  following 
from  there  on  the  usual  procedure  for  filtration. 

The  precipitate  retained  on  the  filter  paper  represents  the  silica  or  siliceous 
matter,  including  possibly  barium  sulphate.  Ignite  and  weigh. 

NOTE.  If  the  amount  is  over  .01  gm.  per  liter,  or  8  parts  per  million,  moisten  with 
a  few  drops  of  concentrated  sulphuric  acid  and  hydrofluoric  acid,  expel  excess  acids, 
and  reweigh.  This  must  be  done  in  platinum.  The  loss  represents  silica,  and  should 


WATER  ANALYSIS  547 

be  recorded  as  such,  and  the  residue  represents  bases,  principally  barium,  combined 
with  sulphuric  acid.  This  will  also  catch  possible  calcium  sulphate  that  might  be  left 
undissolved,  due  to  short  boiling,  to  low  dilution,  or  conditions  which  would  prevent 
its  normal  solubility  in  the  original  solution. 

Iron  and  Aluminum    (Gravimetric) 

The  filtrate  contains  iron,  aluminum,  calcium,  magnesium,  possibly  manganese, 
and  phosphate.  Bring  to  a  boil,  add  two  or  three  drops  cone,  nitric  acid  and  con- 
centrate to  about  25  cc.  Remove  from  hot  plate  or  flame,  add  ammonium 
hydroxide  in  slight  excess,  boil  for  one  or  two  minutes,  and  filter. 

The  precipitate  contains  iron,  aluminum,  and  possibly  phosphates.  Burn  and 
weigh  as  oxides  of  iron  and  aluminum,  plus  phosphates,  and  test  50  cc.  of  the 
original  water  with  treatment  in  the  usual  way  to  determine  whether  or  not 
phosphates  are  present.  Where  this  precipitate  of  iron  and  aluminum  oxides  is 
greater  than  0.01  gm.  per  liter  or  8  parts  per  million,  or. where  the  separation  of 
the  iron  and  aluminum  is  advisable,  the  precipitate  should  be  fused  with  eight  or 
ten  times  its  weight  of  potassium  bisulphate,  redissolved  in  water,  the  iron  reduced 
to  the  ferrous  condition  with  zinc,  and  titrated  with  potassium  permanganate, 
recording  the  difference  in  weight  between  the  original  precipitate  and  the  iron 
determination  as  aluminum  oxide. 

FeXl.43=Fe203. 

NOTE.  Where  much  water  is  available  and  time  is  an  object,  an  additional  500  cc. 
can  be  carried  down  to  approximately  50  cc.  with  a  few  drops  of  nitric  acid,  the  iron 
and  aluminum  precipitated  as  above  mentioned  with  ammonia,  and  the  precipitate 
before  drying  redissolved  in  acid,  reduced  and  titrated  with  potassium  permanganate. 
This  portion  can  be  started  at  the  same  time  the  original  analysis  is  started,  and  will 
greatly  simplify  the  determination  and  save  time. 

Total  Iron  (Colorimetric) 

Reagents.  Iron  Standard.  0.7  gm.  cryst.  ferrous  ammonium  sulphate  is 
dissolved  in  a  small  amount  of  distilled  water,  add  25  cc.  dilute  (1-5)  sul- 
phuric acid,  warm  slightly  and  oxidize  completely  with  potassium  permanganate, 
make  up  to  1000  cc.  1  cc.  =0.1  mg.  Fe. 

Potassium  Sulphocyanide.    2  per  cent  solution. 

Potassium  Permanganate.     6.3  gms.  per  liter. 

Operation.  Instead  of  precipitating,  or  where  traces  of  Fe  are  of  impor- 
tance, 100  cc.  to  1000  cc.  of  the  water  may  be  carried  to  dryness  with  HC1  and  a 
few  drops  of  Br,  taken  up  with  5  cc.  (1  :  1)  HC1,  diluted  to  100  cc.  in  a  Nessler 
tube,  10  cc.  KCNS  solution  (20  gms.  to  a  liter)  added  and  the  color  compared 
with  standards.  The  comparison  should  be  made  at  once  as  the  color  fades. 

NOTE.  It  is  frequently  as  satisfactory  to  add  the  standard  iron  solution  from  a 
burette  to  a  100  cc.  Nessler  tube  containing  5  cc.  (1  :  1)  hydrochloric  acid  (Fe  free), 
10  cc.  potassium  sulphocyanide  solution  (20  gms.  to  a  liter)  and  sufficient  distilled  water 
until  the  color  matches  that  of  the  sample. 

(Ferrous  Iron — Colorimetric) 

(Frequently  desirable  in  acid  waters  but  rarely  necessary.) 

Reagents.  Iron  Standard.  0.7  gm.  cryst.  ferrous  ammonium  sulphate  is 
dissolved  in  one  liter  of  distilled  water  containing  10  cc.  dilute  H2S04.  (Not 
permanent.  Should  be  made  up  as  needed.)  1  cc.  =0.1  mg.  Fe. 


548  WATER   ANALYSIS 

Potassium  Ferricyanide  Solution.  (Prepare  as  needed.)  0.5  g.  per  100  cc. 
distilled  water. 

Sulphuric  Acid.     1  '.  5. 

NOTE.     Prepare  sample  and  standards  at  same  time. 

Operation.  Place  in  100  cc.  Nessler  jar  50  cc.  of  sample,  10  cc.  dilute  H2S04 
(1-5),  filter,  if  necessary,  to  remove  suspended  matter,  add  15  cc.  potassium 
ferricyanide  solution  and  make  up  to  100  cc.  mark  with  distilled  water. 
Compare  with  standards  made  as  follows : 

Place  in  100  cc.  Nessler  jar  75  cc.  distilled  water,  10  cc.  dilute  H2S04  (1-5) 
and  15  cc.  potassium  ferricyanide  solution,  and  mix  well.  Add  various  amounts 
of  iron  standard  from  burette,  mix  and  compare  color.  Determine  ferric  iron 
by  deduction  of  ferrous  iron  from  total  iron. 

Phosphates 

Reagents.  Ammonium  Molybdate.  50  gms.  c.p.  neutral  salt  dissolved  in 
1  liter  distilled  water. 

Nitric  Acid  (spec.  grav.  1.07).     Dilute  about  1-5  with  distilled  water. 

Standard  Phosphate  Solution.  0.5324  gm.  c.p.  cryst.  Na2HP04,  12H20. 
Dissolve  in  distilled  water,  100  cc.  standard  HN03  added.  Dilute  to  1  liter. 

One  cc.  =0.0001  gram  P206. 

Operation.  Evaporate  50  cc.  water  to  dryness  in  porcelain  after  addition  of 
3  cc.  HN03  (spec.  grav.  1.07).  Bake  two  hours  at  212°  F.  Take  up  with  50  cc. 
distilled  water,  add  4  cc.  molybdate  solution  and  2  cc.  HN03,  and  compare  in 
Nessler  tube  with  standards  from  phosphate  solution  made  to  50  cc.  and  treated 
with  same  reagents.  A  tube  2.5  cm.  by  24  cm.  to  100-cc.  mark  of  hard,  white 
glass  is  most  suitable.1  Where  waters  are  already  colored  the  evaporation  should 
be  carried  on  with  3  cc.  HN03  and  0.5  cc.  (or  more,  if  water  is  highly  colored)  of 
KMn04  solution,  (1  gram  per  1000  cc.),  baking  at  212°  F.  for  the  same  time.2 
Where  the  phosphate  is  present  in  large  enough  quantities  to  precipitate  the 
gravimetric  methods  may  be  used. 

Calcium 

The  filtrate  from  iron,  aluminum  and  phosphate  precipitate  contains  calcium, 
magnesium,  and  possibly  manganese.  Concentrate  to  about  100  cc.  Add  to  the 
hot  ammoniacal  solution  a  concentrated  (saturated)  solution  of  ammonium  oxa- 
late  drop  by  drop,  or  add  in  small  portions  crystals  of  ammonium  oxalate.  Allow 
to  boil  two  minutes,  stirring,  if  necessary  (on  account  of  heavy  precipitate  and 
tendency  to  bump),  remove,  filter  and  wash.  (Five  complete  washings  are  usually 
sufficient.) 

NOTE.  Where  great  accuracy  is  desired,  the  precipitate  on  the  filter  should  be 
redissolyed  in  a  small  amount  of  hot,  dilute,  hydrochloric  acid  and  reprecipitated  with 
ammonium  oxalate. 

The  calcium  oxalate  upon  the  filter  paper  can  now  be  burned  and  weighed 
either  as  calcium  oxide  or  calcium  carbonate. 

1 J.  Am.  Chem.  Soc.,  23,  96,  1901. 

2  J.  Ind.  and  Eng.  Chem.,  5,  301-2,  1913. 


WATER  ANALYSIS  549 

NOTE.  The  burning  of  calcium  oxalate  to  carbonate  is  not  so  difficult  as  it  seems, 
as  an  intense  heat  is  necessary  to  convert  it  to  the  oxide,  and  if  the  crucible  is  well 
watched  and  the  flame  gives  just  sufficient  heat  to  carbonize  and  destroy  the  filter 
paper,  there  will  be  no  chance  whatever  of  any  calcium  oxide  being  formed,  or  any 
calcium  oxalate  being  left.  Where  hypothetical  combinations  are  used,  it  is  very 
convenient  to  have  the  calcium  as  carbonate  without  calculation.  Where  burned  to 
the  complete  oxide  it  is  frequently  necessary  to  use  a  blast  lamp,  as  large  precipitates 
require  a  high  temperature  to  reduce  completely  to  oxide  form. 

Optional  (Volumetric) 

Or  it  may  be  dissolved  in  2%  sulphuric  acid  and  titrated  with  the  standard 
solution  of  potassium  permanganate.  (N/50  KMn04  may  be  used.) 

NOTE.  Where  the  volumetric  method  is  to  be  used,  five  complete  washings  are 
not,  as  a  rule,  sufficient,  as  the  presence  of  traces  of  ammonia  salts,  while  not  interfering 
in  any  way  with  the  gravimetric  determination,  are  prone  to  have  considerable  influence 
upon  the  volumetric  results,  due  to  the  possibility  of  traces  of  ammonium  oxalate 
still  being  present. 

Fe  Value  X  0.895  =CaC03. 

Fe  Value  X  0.5016  =CaO. 

Fe  Value  X  0.3584  =Ca. 

Magnesium 

The  filtrate  contains  magnesium  (and  possibly  manganese}.  Acidify  with  HC1, 
concentrate,  if  necessary,  to  150  cc.,  add  25  cc.  saturated  solution  of  ammonium 
sodium  hydrogen  phosphate  (NH4NaHP04, 4H20,  microcosmic  salt),  cool  and  make 
alkaline  with  ammonium  hydrate.  Allow  to  stand  at  least  four  hours,  filter 
and  wash  with  3%  solution  of  ammonium  hydrate.  Burn  and  weigh  as  Mg2P207. 

NOTE.  Accurate  results  are  also  obtained  with  the  use  of  sodium  phosphate  added 
direct  to  the  filtrate  from  the  calcium  precipitate  without  previously  acidifying  with 
acid,  with  25  cc.  to  50  cc.  of  ammonium  hydrate  added  to  make  strongly  alkaline,  after 
which  the  solution  should  be  very  thoroughly  stirred  (for  at  least  two  minutes),  using 
a  rubber-ended  glass  rod.  Allow  to  stand  at  least  four  hours.. 

For  very  rapid  work  in  either  case,  if  the  magnesium  solution  after  the  precipitation 
is  cooled  in  ice-water,  filtration  can  be  frequently  made  in  two  hours'  tune. 

For  extremely  accurate  work  the  precipitate  produced  in  either  of  the  methods 
above  should  be  redissolved  in  a  little  dilute  HC1  and  the  precipitation  repeated. 

Optional  (Volumetric) 

Reagent.     Sodium  Arsenate,  10%  solution. 

The  filtrate  from  the  calcium  precipitate,  or  an  original  portion  of  500  cc. 
from  which  iron,  aluminum  and  calcium  have  been  removed  as  above,  is  acidified. 
Concentrate  to  the  point  of  crystallization,  after  which  approximately  one-third 
by  volume  of  ammonium  hydrate  and  25  cc.  sodium  arsenate  solution  are  added 
and  the  solution  vigorously  shaken  for  at  least  ten  minutes,  filtered,  and  the 
precipitate  washed  free  from  arsenic  with  distilled  water  to  which  has  been 
added  3%  C.P.  ammonia  water.  Dissolve  in  50  cc.  dilute  H2S04  (1:3),  transfer 
to  precipitation  flask,  dilute  to  approximately  100  cc.  and  add  3.4  grams  potas- 
sium iodide.  Allow  to  stand  five  minutes  and  titrate  with  standard  thiosulphate 
solution  until  the  yellow  color  of  the  liberated  iodine  just  disappears.  Starch 
as  an  indicator  is  not  satisfactory,  nor  necessary.  This  method  is  not  so  accurate 
as  the  gravimetric  method,  giving  slightly  high  results,  but  is  good  for  rapid  work. x 
1  J.  Am.  Chem.  Soc.,  29,  1464-7;  ibid,  21,  146. 


550  WATER  ANALYSIS 

Manganese 

Where  necessary,  manganese  should  be  determined  separately  in  another 
portion  of  the  water  and  corrections  made.  The  Knorres  Persulphate  method  is 
the  most  reliable  for  large  amounts  (10  milligrams  Mn  per  liter);  the  Bis- 
muthate  method  for  smaller  amounts. 

Knorres,  Persulphate  Method  (Volumetric) 

Reagents.     Potassium  Bisulphate  C.  P. 

Ammonium  Persulphate  Solution  (60  grams  per  liter  distilled  water). 

Hydrogen  Peroxide  Solution.  Equivalent  to  N/10  KMn04.  (Approx.  5.6  cc., 
3%  H202  diluted  to  100  cc.) 

Operation.  Evaporate  5  liters  or  more  to  dryness,  adding  first  10  cc.  con- 
centrated H2S04.  Ignite  after  adding  a  few  crystals  of  potassium  bisulphate 
and  take  up  in  hot  water.  Transfer  to  250-cc.  Erlenmeyer  flask  with  5  cc.  dilute 
(1  :  3)  H2S04,  add  10  cc.  ammonium  persulphate  solution,  boil  twenty  minutes, 
cool,  dissolve  precipitate  (manganese  superoxide)  in  standard  hydrogen  peroxide 
solution.  (If  no  ppt.  forms  no  manganese  is  present.) 

NOTES.  When  hydrogen  peroxide  solution  is  standardized  against  N/10  KMnO4 
1  cc.  will  be  equivalent  to  2.754  milligram  Mn. 

An  excess  of  10-20  cc.  H2O2  Sol.  can  be  added  and  this  excess  titrated  with  N/10 
KMnO4. 

Sodium  Bismuthate  Method  (Colorimetric) l 

Reagents.  Potassium  Permanganate.  0.288  gram  KMn04  to  1000  cc. 
1  cc.  =0.1  milligram  Mn. 

Sodium  Bismuthate  (purest). 

See  method  of  preparation  of  reagent  given  on  page  263. 

Nitric  Acid.  (Spec.  grav.  1.135)  3  parts  concentrated  HN03  to  1  part  H20 
should  be  blown  with  air  until  free  from  oxides  of  nitrogen. 

Sulphuric  Acid.  25  cc.  concentrated  H2S04  to  1000  cc.  Add  permanganate 
solution  to  a  faint  but  noticeable  color. 

Operation.  Evaporate  500  cc.  in  porcelain  dish  after  adding  1  cc.  dilute  H2S04 
in  excess  to  that  necessary  to  neutralize  all  alkali.  Ignite  to  remove  free  acid 
(organic  matter  and  chlorine),  cool  and  dissolve  in  50  cc.  HN03  (30  cc.  concentrated 
HN03  to  1  liter),  with  heat  if  necessary.  Cool  again,  add  0.5  gram  sodium 
bismuthate  and  heat  until  pink  color  disappears,  re-cool  and  add  sodium  bismuth- 
ate  in  excess,  filter  through  asbestos  in  Gooch  crucible  (asbestos  must  be  free 
from  organic  matter,  thoroughly  washed  and  ignited),  or  alundum  crucible. 
Wash  with  nitrite-free  distilled  water  containing  5%  dilute  HN03  (30  cc.  concen- 
trated HN03  per  liter),  into  Nessler  tube,  make  up  to  100  cc.  and  match  with  color 
produced  by  necessary  amount  of  standard  KMn04  in  100  cc.  H2S04  reagent. 

No.  cc.  standard  KMn04  X  0.2  =  milligrams  Mn  per  liter. 

NOTE.  The  permanganate  solution  used  for  oxygen  consumed  (see  Sanitary 
Method)  contains  0.139  gram  Mn  per  liter  and  may  be  used  when  necessary. 

No.  cc.  X  0.278  =  milligram  Mn  per  liter. 

1  J.  Am.  Chem.  Soc.,  29,  1074-78,  1907. 


WATER  ANALYSIS  551 


Sulphates 

100  cc.  of  the  water  is  slightly  acidified  with  cone.  HC1  and  5  cc.  10  %  NH4C1 
solution  added,  brought  to  a  boil,  and  if  turbid  is  filtered  and  washed  four  or  five 
times  with  boiling  water.  The  clear  or  original  water  is  now  brought  to  a  boil 
and  10%  barium  chloride  added  drop  by  drop  to  the  boiling  solution  in  slight 
excess.  Boil  ten  minutes,  stirring  from  time  to  time,  if  the  precipitate  is  heavy. 
Remove  and  allow  to  cool  prior  to  filtering.  The  precipitate  consists  of  barium 
sulphate.  Wash  free  from  chlorides,  testing  with  AgN03.  Dry,  ignite  and  weigh. 

BaS04  X.411=S04. 
BaS04  X.583=CaS04. 
milligrams  BaS04  X  .338  =  CaS04  grains  per  gallon. 

Benzidine  Method  (Optional)1 

Reagents.    Benzidine  Solution.    Triturate  in  a  mortar  with  5  cc.  to  10  cc. 

water,  4  grams  benzidine  base.  Transfer  to  liter  flask,  add  10  cc.  HC1  and  make 
to  volume.  1  cc.  =.0013  gram  S04. 

Hydroxylamine  Hydrochloride.     1%  solution  in  water. 

Operation.  Add  10  cc.  hydroxylamine  hydrochloride  to  250  cc.  water,  then 
add,  at  once  stirring  well,  100  cc.  benzidine  solution.  Allow  to  stand  fifteen  to 
twenty  minutes,  decant  through  vacuum  filter  and  wash  with  10  cc.  to  20  cc. 
distilled  water  (do  not  let  filter  run  dry),  return  filter  paper  to  beaker,  cover 
with  distilled  water,  bring  to  a  boil  and  titrate  with  N/10  or  N/50  NaOH,  using 
phenolphthalein  as  indicator. 

One  cc.  N/10  NaOH  =  .0048  gram  S04. 
One  cc.  N/50  NaOH  =  .00096  gram  S04. 

NOTE.  An  accurate  method  by  the  turbidimeter  is  given  by  Hale  in  the  chapter 
on  Coal,  page  675. 

N.  B.  Method  by  Muer,  Jour.  Ind.  Eng.  Chem.,  Vol.  3,  Aug.,  1911.  When  the 
sulphate  is  25  p. p.m.  or  more,  the  determination  may  be  made  by  the  turbidimeter 
method  direct  on  100  cc.  For  less  quantities,  larger  amounts  of  water  are  taken  and 
evaporated. 

Sodium  and   Potassium 

The  filtrate  contains  sodium  and  potassium  and  may  be  used  for  such  unless 
the  water  is  highly  mineralized,  in  which  case  a  new  portion,  100  cc.  to  500  cc., 
should  be  taken. 

Evaporate  to  dryness,  add  saturated  solution  of  barium  hydrate  in  excess, 
filter,  wash  with  hot  water,  add  to  the  filtrate  ammonium  carbonate  in  excess  and 
a  few  drops  of  ammonium  oxalate,  boil,  filter,  evaporate  again  to  dryness  and  dry 
at  a  high  temperature  to  expel  excess  of  ammonia  salts.  Redissolve,  add  slight 
excess  of  ammonium  carbonate  again  and  continue  until  no  further  precipitate 
is  formed  on  such  addition.  Evaporate  to  dryness  in  a  weighed  platinum  dish, 
remove  ammonium  salts  by  high-temperature  drying,  and  weigh  the  combined 
chlorides  of  sodium  and  potassium.  Moisten  with  about  25  cc.  of  water  and  a 
few  drops  of  HC1  and  add  from  1  cc.  to  5  cc.  of  10%  solution  of  platinic  chloride 
^reidbaum  and  Nydegger,  Z.  Agnew.  Chem.,  1907-9. 


552  WATER  ANALYSIS 

(1  cc.  to  each  25  milligrams  to  30  milligrams  total  chlorides).  Evaporate  to  dry- 
ness  on  water  bath,  take  up  and  wash  with  95%  alcohol  until  filtrate  is  free  from 
color.  Dry,  redissolve  precipitate,  washing  through  the  filter  paper  in  hot  water. 
Evaporate  again  to  dryness  and  weigh  as  K2PtCl6. 

K,PtCl,X.161=K. 
KoPtCl  X.307=KC1. 


Deduct  from  combined  weight  of  chlorides.     Remaining  NaClX  .394  =Na. 

NOTE. 
as  sodium 


NOTE.     When  separation  is  not  necessary,  the  combined  chlorides  are  calculated 
chloride  and  reported  as  sodium  and  potassium  chlorides. 


Alkalinity 

In  ordinary  cases  titrate  with  N/10  or  N/50  H2S04,  using  methyl  orange  as 
indicator.  Special  cases  will  be  considered  later. 

Reagents.     Sulphuric  acid,  N/10.     Methyl  orange.     Phenolphthalein. 

Operation.  250  cc.  of  water  in  400-cc.  beaker  or  a  casserole  are  titrated  with 
N/10  H2S04,  using  two  to  five  drops  of  methyl  orange  indicator  (or  50  cc.  can 
be  similarly  titrated  with  N/50  H2S04). 

Calculate  for  250-cc.  sample. 

No.  cc.X4X.005  =gms.  per  liter  CaC03. 

No.  cc. X4X 58.4 X. 005  =grs.  per  gallon  CaC03. 

Or         X  1.168  =grs.  per  gallon  CaC03. 

Distilled  water,  and  neutral  waters  containing  magnesium  chloride  and 
magnesium  sulphate  frequently  give  an  alkaline  reaction  when  used  with  methyl 
orange.  In  such  cases  from  .2  to  .8  cc.  N/10  acid  are  required  to  discharge  the 
alkaline  color  of  the  methyl  orange.  Such  a  procedure  would  suggest  to  the 
operator  that  the  waters  were  alkaline.  However,  if  such  neutral  waters  are 
boiled  with  phenolphthalein  as  an  indicator  for  twenty  minutes  and  no  pink 
color  develops,  the  waters  are  not  alkaline  but  neutral.  The  use  of  a  blank  of 
.2  cc.  is  of  no  value  under  such  conditions  and  it  appears  to  the  writer  as  much 
the  safest  way  when  the  titration  is  under  1  cc.  of  N/10  acid  that  the  water  be 
boiled  with  phenolphthalein  in  an  effort  to  determine  absolutely  whether  this 
water  is  alkaline,  due  to  the  presence  of  a  carbonate  as  indicated  by  the  methyl 
orange,  or  whether  the  alkalinity  is  entirely  due  to  the  hydrolyzing  of  the  cal- 
cium or  magnesium  base  present  in  the  absence  of  alkali.  When  no  pink  color 
is  produced  the  water  should  be  pronounced  neutral. 

Phenolphthalein  may  also  be  used  as  indicator  on  another  250-cc.  portion, 
using  the  above  procedure.  This  titration  in  connection  with  the  methyl  orange 
titration  makes  possible  a  determination  of  the  relation  of  carbonate,  bicarbonate 
and  caustic  alkalinity. 

The  following  is  adapted  from  a  table  on  page  39,  Standard  Methods  of  Water 
Analysis  of  the  American  Public  Health  Association,  and  is  of  value  in  showing 
the  relation  of  the  various  titrations.  Methyl  orange  has  been  used  in  place  of 
erythrosine. 


WATER  ANALYSIS 


553 


TABLE  SHOWING  RELATION  BETWEEN  ALKALINITY  BY  PHENOL- 
PHTHALEIN  AND  THAT  BY  METHYL  ORANGE  IN  PRESENCE  OF 
BICARBONATES,  CARBONATES  AND  HYDRATES. 


Bicarbonates. 

Carbonates. 

Hydrates. 

P  =  O 

M 

o 

o 

P<iM  

M-2P 

2P 

o 

P  =  iM  
P>|M 

0 

o 

2P 
<2(M-P} 

0 
2P  M 

P  =  M         .      . 

o 

o 

M 

M  =  Methyl  orange  alkalinity. 
P  =  Phenolphthalein  alkalinity. 

Acidity 

For  acidity  use  N/10  Na2CO3  and  250  cc.  water. 


Acidity  due  to 

Indicator. 

Hot  or  Cold. 

Carbonic  and  sulphuric  acids,  also  Fe  and  Al 
sulphates  

Phenolphthalein 

Cold 

Sulphuric  acid,  also  Fe  and  Al  sulphates  

Phenolphthalein 

Boiling 

Sulphuric  acid  alone  

Methyl  orange 

Cold 

When  desired,  20  cc.  N/10  H2SO4  may  be 
added.  Boil  fifteen  to  twenty  minutes,  cool 
and  titrate,  noting  the  excess  of  acidity  over 
the  original  20  cc. 

Free  Carbonic  Acid1 

Reagents.  Either  standard  N/10  sodium  carbonate  or  standard  N/22  sodium 
carbonate.  For  the  latter  dissolve  2.41  grams  of  dry  sodium  carbonate  in  one  liter 
of  distilled  water  which  has  been  boiled  and  cooled  in  a  carbon  dioxide  free 
atmosphere.  Hold  both  solutions  in  glass  bottles  protected  by  tubes  filled^  with 
soda-lime. 

One  cc.N/10  Na2C03=2.2  milligrams  C02. 

One  cc.N/22  Na2COs  =  1.0  milligram  C02. 

Operation.  With  N/10  sodium  carbonate  titrate  250  cc.  of  sample  in  400- 
cc.  beaker,  using  phenolphthalein  as  indicator.  First  faint  but  permanent  pink 
denotes  end-point. 

Using  250  cc. 

No.  cc.  N/10  Na2C03X8.8  =C02  parts  per  million. 
No.  cc.  N/10  Na2C03X.513  =C02  grains  per  gallon. 

With  N/22  sodium  carbonate  solution,  use  100  cc.  of  sample,  preferably 
in  100-cc.  Nessler  tube,  titrate  and  rotate  the  tube  until  faint  but  permanent 

1  For  criticisms  of  this  method,  see  Z.  Nahr.  Genussm.,  24,  429,  also  Chem.  Abs., 
5,  1024;  C.A.,  6,  3137;  C.A.,  7,  38. 


554  WATER  ANALYSIS 

pink  color  30  seconds  without  fading  is  produced,  using  phenolphthalein  as  indi- 
cator 

Using  100  cc. 

No.  cc.  N/22  Na2C03X10  =C02  parts  per  million. 
No.  cc.  N/22  Na2C03X.583  =C02  grains  per  gallon. 

Chlorine 

Titrate  100  cc.  of  water,  using  1  cc.  of  10%  potassium  chromate  as  an  indica- 
tor, with  N/10  AgN03  to  first  permanent  indication  of  the  red  silver  chromate. 
(Acid  waters  should  be  neutralized  and  sulphide  waters  boiled  with  a  drop  or  so  of 
nitric  acid  and  then  neutralized  for  reliable  results.) 

No.  cc.X3.42  =grs.  per  gallon  NaCl. 
No.  cc.X 58.46  =  parts  per  million  NaCl. 
No.  cc.X35.46  =  parts  per  million  Cl. 

NOTE.  Where  qualitative  test  shows  chlorine  to  be  high,  smaller  portions  of  the 
sample  should  be  taken,  either  by  certified  pipette,  or  burette,  and  when  the  titration 
with  N/10  AgN03  is  less  than  .2  cc.,  N/50  or  N/100  AgNO3  should  be  used  for  accuracy. 

Nitrates 
(Also  see  Sanitary  Analysis) 

Evaporate  100  cc.  of  water,  after  adding  2  cc.  10%  Na2C03,  to  dryness,  cool, 
moisten  with  2  cc.  phenolsulphonic  acid,  add  50  cc.  water  and  then  NE^OH  until 
slightly  ammoniacal.  Yellow  coloration  shows  presence  of  nitrates.  Compare 
with  standards  which  should  be  renewed  every  month,  or  oftener.  Less  than 
^  grain  per  gallon,  or  about  2  parts  per  million  as  KN03,  while  of  value  in  sanitary 
analyses,  usually  rank  as  "  trace  "  in  mineral  waters. 

Where  nitrates  are  high,  85  to  90  parts  per  million,  or  5  grains  per  gallon  and 
over,  colorimetric  methods  do  not  always  give  reliable  results,  and  500  cc.  of  the 
water  should  be  first  boiled  with  a  slight  excess  of  acid,  then  made  alkaline 
with  sodium  or  potassium  hydroxide,  reduced  with  10  grams  each  of  powdered  Zn 
and  Fe,  or  10  grams  powdered  Al,  and  distilled  into  an  excess  of  N/10  or  N/100 
HC1,  as  the  case  may  be,  and  titrated  back,  using  cochineal  as  indicator,  and 
calculating  the  ammonia  absorbed  to  N03  or  Ca(N03)2  as  desired.  (Where  free 
ammonia  or  its  compounds  are  present  corrections  must  be  made.) 

A  recent  modification  of  this  method  depends  upon  the  absorption  of  ammonia 
into  a  solution  of  boric  acid  (5  grams  boric  acid  in  100  cc.  of  water).  Due  to 
the  very  weak  acidity  of  the  boric  acid,  it  is  possible  to  titrate  the  ammonia 
direct  with  standard  acid,  using  methyl  orange  as  an  indicator,  and  this  has  the 
advantage  of  doing  away  with  two  standard  solutions.  The  boric  acid  strength 
is  based  upon  5  grams  of  boric  acid  to  100  cc.  of  water  to  each  .2  gram  of  ammonia 
absorbed.  It  is  stated  that  even  the  cooled  condenser  is  unnecessary,  in  this 
absorption.1 

1  The  Volumetric  Determination  of  Ammonia.  L.  W.  Winkler,  Budapest.  Z.  angew. 
Chrm.,  26,  Aufsatzteil,  231-2. 

Determination  of  Ammonia  by  the  Boric  Acid  Method.  L.  W.  Winkler,  Z.  angew. 
Chem.,  27,  I,  630-2,  1914. 

The  Determination  of  Ammonia  by  the  Boric  Acid  Method.    E.  Bernard, 
angew.  Chem.,  27,  1,  664,  1914. 


WATER  ANALYSIS  555 


Ammonia  and    Its  Compounds 

Place  500  cc.  or  less  in  an  800-cc.  Kjeldahl  flask,  make  alkaline  and  distill 
into  N/10,  or  weaker,  HC1,  titrate  with  cochineal  or  Nesslerize.  (See  Sanitary 
Analysis,  page  536.) 

Total  Mineral  Residue 

Use  a  clean  weighed  platinum  dish.  Evaporate  50  cc.  (certified  pipette)  to 
dryness  at  about  130°  C.  and  bake  for  at  least  thirty  minutes  at  that  temperature. 
Ordinary  water-bath  temperature  will  not  remove  water  of  crystallization  from 
Na2SC>4  or  CaS04.  Weigh  to  the  fourth  decimal  or  .0001  gram. 

Weight  XI 168=  grains  per  gallon. 
0.1  milligram  =2  parts  per  million. 

Residues  of  acid  waters  should  be  ignited  to  a  dull  red  heat.  Where  the 
acidity  is  low  a  drop  or  so  of  sulphuric  acid  should  be  added  to  assure  the  fixation 
of  all  sodium  and  potassium  salts  as  the  sulphate.  The  ignition  should  be  com- 
plete so  that  no  free  acid  is  left  behind  and  to  assure  the  decomposition  of  all  iron 
compounds  to  the  oxide  form.  In  calculating,  correction  must  be  made  for  the 
change  in  the  iron  salts  and  all  other  compounds  converted  to  the  sulphate  form 
for  comparison  with  the  sulphated  residue,  and  then  the  proper  corrections  made 
to  give  the  theoretical  residue  on  the  original  water. 

Residues  with  much  organic  matter,  after  weighing,  may  be  gently  ignited  until 
the  carbon  has  been  burned  off,  cooled,  recarbonated  with  tested  (NH^COs  dried 
and  again  weighed.  The  difference  in  weight  after  titrating  for  possible  volatil- 
ized chlorides  gives  approximately  the  organic  matter  present. 

Waters  high  in  easily  decomposed  MgCl2  or  Ca(N03)2  should  be  evaporated 
with  a  few  drops  excess  of  H2S04,  or  Na2C03,  and  the  residue  compared  with  an 
addition  of  all  bases  calculated  to  the  sulphate  form,  or  corrected  for  added  car- 
bonate. 

NOTE.  When  acid  is  used,  ignite  to  a  dull  red  heat;  when  carbonate,  evaporate 
as  in  the  case  of  the  original  residue. 

Hydrogen   Sulphide 

Due  to  the  fact  that  hydrogen  sulphide  is  frequently  very  transient  and  often 
oxidizes  to  sulphate  in  transit,  it  is  advisable  to  collect  this  sample  in  a  special 
container  at  the  point  of  sampling.  Two  or  three  bottles  holding  exactly  250  cc. 
of  water  each,  are  used,  each  bottle  containing  50  cc.  N/100  iodine  solution. 
After  filling,  the  bottle  is  sealed.  The  sample  is  titrated  with  standard  N/100 
sodium  thiosulphate  upon  receipt  at  laboratory,  at  which  time  a  blank  is  run, 
using  50  cc.  iodine  solution  made  to  mark  with  distilled  water.  The  difference 
between  the  titration  of  the  sample  and  the  blank  represents  hydrogen  sulphide 
present. 

Iodine  value  X0.1263x4=sulphur  value  grams  per  liter. 


556  WATER   ANALYSIS 

Oil 

Frequently  waters  from  condensing  engine,  or  after  passing  heaters  or  oil 
separators,  still  contain  oil  in  small  quantities.  The  following  method  has  been 
found  most  satisfactory: 

Reagents.  Ferric  Chloride  Solution.  (10  grams  of  iron  dissolved  in  200  cc. 
HC1,  oxidized  with  HN03  and  made  to  one  liter.) 

Ammonia  C.P. 

NOTE.  If  the  oil  exceeds  0.4  grain  per  gallon,  use  500  cc.,  or  less  for  the  deter- 
mination; if  below  0.4  grain  per  gallon  use  1  liter. 

Operation.  Add  to  the  water  taken  in  a  large  beaker  or  flask  5  cc.  of  the 
"  ferric  chloride  "  solution  and  heat  nearly  to  boiling;  then  add  ammonia  in 
excess,  to  precipitate  the  iron  (which  precipitate  contains  all  the  oil),  and  boil  for 
two  minutes. 

Allow  to  stand  a  few  minutes  and  filter  through  a  15  cm.  filter  paper  which 
has  been  previously  extracted  with  ether,  transferring  the  precipitate  on  to  the 
paper  with  hot  water,  and  washing  three  or  four  times  with  hot  water.  Then  dry 
both  filter  and  precipitate  in  the  water  oven  at  100°  C.  and  when  dry,  extract 
with  ether  in  the  soxhlet  in  the  usual  way,  evaporate  the  ether  extract  and 
weigh  the  remaining  oil. 

Dissolved  Oxygen 

Use  the  Winkler  Method1 

Reagents.  No.  1.  Manganous  Sulphate  Solution.  48  grams  manganous 
sulphate  dissolved  in  100  cc.  distilled  water. 

No.  2.  Iodide  Solution.  360  grams  NaOH  and  100  grams  KI  dissolved  in  1 
liter  of  distilled  water. 

No.  3.  Concentrated  hydrochloric  acid,  or  sulphuric  acid  sp.gr.  1.4  (dilute 
111). 

No.  4.  Sodium  Thiosulphate  Solution.  N/100  solution  is  made  as  needed 
from  the  N/10  stock  solution. 

NOTE.  Not  permanent;  should  be  frequently  restandardized  against  N/100  potas- 
sium bichromate. 

The  addition  of  5  co.  of  chloroform  plus  1.5  grams  sodium  or  ammonium  carbonate 
to  each  liter  of  solution  on  mixing  will  improve  its  keening  quality. 

N/40  sodium  thiosulphate  containing  6.2  grams  C.P.  recrystallized  salt  por  liter 
may  be  preferred  to  N/100  strength.  1  cc.  of  this  solution  is  equivalent  to  0.2  milligram 
oxygen  by  weight  or  0.1395  cc.  oxygen  by  volume,  standard  conditions. 

5.  Starch  Solution.2  The  starch  should  first  be  made  into  a  thin  paste  with 
cold  water  and  about  200  times  its  weight  of  boiling  water  stirred  in  and  boiled 
for  a  few  minutes.  A  few  drops  of  chloroform  will  assist  in  preserving  this  solut  ion. 

Collection  of  Sample.  A  small-necked,  250-cc.  bottle  should  be  used,  etched 
or  otherwise  marked,  with  its  exact  volume  previously  determined.  The  collec- 

'Ber.  deutsche  Chem.  Gesell.,  21,  2843,  1888.  Also  Z.  Anal.  Chem.,  53,  665-72, 
1914;  C.F.C.A.,  8,  674,  1915. 

2  Hale  gives  the  following  method.  "Rub  5  grams  of  potato  starch  with  cold  water 
to  a  thin  paste  together  with  10  milligrams  of  mercuric  iodide.  Pour  into  one  liter 
of  boiling  water  and  boil  half  an  hour." 


WATER   ANALYSIS  557 

tion  should  be  so  arranged  to  exclude  outside  air  and  result  in  several  con- 
tinuous changes  of  the  contents  before  stoppering,  care  being  taken  to  exclude 
air  bubbles. 

Operation.  To  sample  as  received  add,  in  both  cases  by  pipette,  delivering 
below  surface  of  water  and  away  from  the  air,  2  cc.  solution  No.  1  (manganese 
sulphate)  and  No.  2  (NaOH,KI).  Restopperand  shake  thoroughly.  After  pre- 
cipitate has  settled  add  2  cc/^pCl  or  H2S04  and  again  mix  by  thorough  shaking 
until  precipitate  has  completely  dissolved,  transfer  100  cc.  to  flask,  and  titrate 
with  solution  No.  4  (sodium  thiosulphate),  using  starch  as  indicator  near  end  as 
the  color  approaches  a  faint  yellow. 

N  =  cc.  N/100  thiosulphate  solution. 
V  =  capacity  of  bottle  less  4  cc.  (vol.  sol.  1  and  2  added). 

O  =  the  amount  of  oxygen  in  parts  per  million  in  water  saturated  at  the  same  tem- 
perature and  pressure. 

.0008NX  1,000,000 

(1)  Oxygen  in  p.p.m.  ^ —      —  =  .8N.1 

(2)  Oxygen  in  cc.  per  liter          =.7  oxygen  p.p.m. 

Oxygen  p.p.m.  (observed  temp,  and  pres.) 

(3)  Oxygen  per  cent  saturation  =  —      — ^ — — —• . 

Saturation  oxygen  p.p.m.  (observed  temp,  and  pres.) 


METHODS  FOR  THE  DETERMINATION  OF  SMALL  AMOUNTS 
OF  LEAD,  ZINC,  COPPER  AND  TIN 

Very  frequently  a  determination  is  desired  of  materials  which  are  apt  to  be 
present  in  water  due  to  the  solvent  action  of  such  water  upon  pipes  and  con- 
tainers. In  most  cases  the  estimates  are  made  by  colorimetric  methods  if  the 
amounts  present  are  exceedingly  small.  As  these  determinations  are  made  only 
in  rare  cases  it  seems  advisable  to  summarize,  calling  attention  to  the  fact  that 
all  methods  may  be  found  in  full  in  any  of  the  editions  of  Standard  Methods  for 
Water  Analysis  gotten  out  by  the  American  Public  Health  Association. 

Where  any  or  all  of  the  metals,  lead,  zinc,  copper  and  iron  are  apt  to  be  present, 
a  large  quantity  (1  to  4  liters),  of  the  water  is  evaporated.  The  metals  are 
separated  as  sulphides  with  ammonia  and  hydrogen  sulphide.  The  precipitate 
after  washing  is  dissolved  in  nitric  acid  and  refiltered  to  remove  suspended 
matter  and  then  concentrated  with  H2S04. 

The  lead  is  removed  by  taking  up  the  concentrated  solution  with  50%  alcohol 
(100  cc.  to  150  cc.),  filtering  and  dissolving  the  precipitate  in  ammonium  acetate, 
after  which  the  solution  is  made  to  volume  and  divided.  One-half  is  saturated 
with  hydrogen  sulphide  water  to  get  an  approximate  idea  of  the  amount  of  lead 
present.  To  the  other  half  add  two  to  three  drops  of  acetic  acid,  then  an  excess 
of  hydrogen  sulphide  water  and  compare  the  color  with  standards.  This  gives  lead. 

The  alcohol  is  removed  from  the  filtrate  by  evaporation  and  it  is  then  treated 
with  ammonia  to  remove  possible  iron.  The  filtrate  from  the  iron  precipitate 

1  Correcting  for  displacement  for  300-cc.  bottle,  .8N  =  .811N;  for  275-cc.  bottle, 
.8N  =  .812N. 

No  correction  for  displacement  affects  result  .1  p.p.m.  oxygen. 

Twenty-five  cc.  variation  in  capacity  of  bottle  affects  result  .01  p.p.m.  oxygen. 

The  above  formulae  are  based  upon  N/100  thiosulphate,  and  titrating  100  cc. 
volume.  N  =  cubic  centimeters  thiosulphate  used. 


558  WATER  ANALYSIS 

is  neutralized  with  H2S04,  then  2  cc.  concentrated  H2S04  and  1  gram  urea 
added.  Copper  is  removed  by  electrolyzing  (two  hours  with  0.5  ampere  current). 
If  the  deposit  is  material  it  may  be  weighed  as  copper  after  washing  with  alcohol 
and  drying.  When  the  deposit  is  extremely  small  it  should  be  dissolved  in  nitric 
acid,  evaporated  to  dryness  to  remove  acid  taken  up  in  water,  after  which  potas- 
sium sulphide  solution  is  added  and  the  color  compared  with  standards.  This 
gives  copper. 

The  solution  from  the  above  is  nearly  neutralized  with  ammonia.  It  is  then 
concentrated  and  2  grams  potassium  oxalate  and  1.5  grams  potassium  sulphate  are 
added  and  the  zinc  removed  by  electrolyzing.  (Three  hours  with  0.3  ampere 
current.)  This  gives  zinc. 

Where  copper  only  is  desired  it  is  frequently  sufficiently  satisfactory  to  con- 
centrate the  water  from  50  cc.  to  75  cc.,  after  which  it  is  acidified  with  2  to  5  cc. 
concentrated  H2S04,  depending  upon  whether  the  water  is  very  alkaline  with 
carbonate  of  lime,  etc.,  and  then  the  procedure  for  copper  is  followed.1 

There  is  no  satisfactory  method  for  the  quantitative  determination  of  small 
quantities  of  tin.  In  the  above-mentioned  procedure,  however,  in  case  tin  should 
be  present  it  would  be  removed  with  the  ammonia  precipitate  for  the  removal  of 
iron  and  its  presence  may  be  avoided  by  dissolving  the  sulphides  in  the  original 
precipitation  in  HN03,  in  which  the  tin  would  remain  behind  insoluble. 

HARDNESS 
Total   Hardness 

The  most  accurate  method  for  total  hardness  is  by  calculation  of  the  calcium 
and  magnesium  determined  gravimetrically  as  previously  outlined,  calculating 
the  calcium  as  calcium  carbonate  and  the  magnesium  to  its  calcium  carbonate 
equivalent  in  terms  of  parts  per  million.2  However,  where  only  the  hardness  is 
desired,  gravimetric  methods  are  cumbersome  and  the  following  are  accepted  as 
standard. 

The  standard  method  for  the  determination  of  total  hardness,  as  well  as  tem- 
porary and  permanent,  depends  upon  the  action  of  the  lime  and  magnesia  in 
solution  upon  soap,  the  soap  added  in  a  very  dilute  solution  in  alcohol.  Total 
hardness  represents  the  total  soap  acted  upon  by  the  water  in  its  original  state, 
permanent  hardness  represents  the  total  soap  acted  upon  by  the  water  after  the 
water  in  question  has  been  thoroughly  boiled  and  separated  from  the  suspended 
matter,  and  temporary  hardness  represents  the  difference  between  the  total  hard- 
ness and  the  permanent  hardness,  and  while  it  is  supposed  to  represent  combined 
carbonates  of  lime  and  magnesia,  and  the  permanent  hardness  is  supposed  to 
represent  lime  and  magnesia  in  other  forms  than  carbonate,  this  is  rarely  so  due 
to  the  fact  that  a  certain  material  amount  of  carbonate  of  lime  and  magnesia  ia 
soluble  in  water,  even  in  the  absence  of  carbon  dioxide  gas.  The  reagents  used 
are  standard  soap  solution  and  standard  calcium  chloride  solution,  the  latter 
being  made  under  such  conditions  that  1  cc.  of  the  solution  is  equivalent  to 
0.2  milligram  of  calcium  carbonate. 

1  Phelps,  Jour.  Amer.  Chem.  Soc.,  28,  369,  1906. 
8  C.  Bahlmann,  J.  Ind.  Eng.  Chem.,  6,  209,  11. 


WATER  ANALYSIS 


559 


Preparation  of  Solutions 

0.2  gram  pure  calcium  carbonate  is  dissolved  in  a  small  amount  of  dilute  HC1, 
taking  pains  to  avoid  any  loss  due  to  effervescence  or  spattering.  Evaporate  the 
solution  to  dryness  several  times  to  remove  excess  acid.  Dissolve  in  distilled 
water  and  make  up  to  1  liter. 

Standard  soap  solution  is  obtained  by  dissolving  approximately  100  grams 
dry  castile  soap  in  1  liter  80%  alcohol.  This  solution  should  stand  several  days. 
For  standardizing,  this  solution  should  be  diluted  with  alcohol  (70%  to  80%), 
until  6.4  cc.  when  added  to  20  cc.  of  standard  calcium  solution  will  produce  a 
permanent  lather.  Usually  less  than  100  cc.  of  the  original  soap  solution  will 
make  1  liter  of  standard  solution. 

For  standardizing,  use  250-cc.  glass-stoppered  bottle,  add  20  cc.  calcium 
solution  with  30  cc.  distilled  water.  The  soap  solution  should  be  added  from  a 
burette,  approximately  .2  cc.  at  a  time,  after  which  the  bottle  is  shaken  vigorously 
until  the  lather  formed  remains  unbroken  .for  five  minutes  after  shaking  and  after 
the  bottle  has  been  placed  upon  its  side. 

NOTE.  Pure  potassium  oleate  and  potassium  carbonate  may  be  used  in  place 
of  soap.1 

Operation.  Fifty  cc.  of  the  water  in  question  are  measured  into  a  250-cc. 
bottle,  the  soap  solution  added,  approximately  .2  cc.  at  a  time,  and  in  the  same 
manner  as  described  for  the  standardizing  of  said  soap  solution.  The  following 
table,  copied  from  p.  33,  Standard  Methods  of  Water  Analysis,  A.P.H.A.,  1913, 
may  be  used  to  obtain  the  total  hardness  from  the  results  so  noted : 


TABLE  OF  HARDNESS  SHOWING  THE  PARTS  PER  MILLION  OF  CALCIUM 
CARBONATE  (CaCO3)  FOR  EACH  TENTH  OF  A  CUBIC  CENTIMETER 
OF  SOAP  SOLUTION  WHEN  50  CC.  OF  THE  SAMPLE  ARE  USED. 


cc.  of  Soap 
Solution. 

0.0 
cc. 

0.1 
cc. 

0.2 
cc. 

0.3 
cc. 

0.4 
cc. 

0.5 
cc. 

0.6 
cc. 

0.7 
cc. 

0.8 
cc. 

0.9 
cc. 

0.0 

0.0 

0.6 

3.2 

1.0 
2.0 

4.8 
19.5 

6.3 
20.8 

7.9 
22.1 

9.5 
23.4 

11.1 

24.7 

12.7 
26.0 

14.3 
27.3 

15.6 

28.6 

16.9 
29.9 

18.2 
31.2 

3.0 
4.0 
5.0 

32.5 
45.7 
60.0 

33.8 
47.1 
61.4 

35.1 

48.6 
62.9 

36.4 
50.0 
64.3 

37.7 
51.4 
65.7 

38.0 
52.9 
67.1 

40.3 
54.3 
68.6 

41.6 
55.7 
70.0 

42.9 
57.1 
71.4 

44.3 
58.6 
72.9 

6.0 
7.0 

74.3 

88.6 

75.7 
90.0 

77.1 
91.4 

78.6 
92.9 

80.0 
94.3 

81.4 
95.7 

82.9 
97.1 

84.3 
98.6 

85.7 
100.0 

87.1 
101.5 

It  is  not  desirable  to  use  more  than  7  cc.  of  soap  solution  for  50  cc.  of  the 
water,  and  when  the  figures  are  higher,  the  water  should  be  diluted  with  distilled 
water.  The  reading  in  the  table  corresponding  to  the  cc.  of  soap  solution 

JC.  Blacher,  Chem.  Ztg.,  36,  541;  J.  Soc.  Chem.  Ind.,  31,  555,  C.  A.,  7,  1394;  C. 
Blacher,  P.  Gruenberg,  M.  Kissa,  Chem.  Ztg.,  37,  56-8,  C.  A.,  7,  1938.  L.  W.  Winkler, 
Z.  Anal.  Chem.,  53,  409-15,  C.  A.,  8,  2912. 


560  WATER  ANALYSIS 

used  is  then  multiplied  by  the  quotient  -     — ;    x  cc.  being  equal  to  the  amount 

*c  cc. 

of  water  taken.  In  making  this  determination  there  is  frequently  noted  a  false 
end-point  sometimes  known  as  the  magnesium  end-point.  ,To  avoid  error,  it 
is  advisable,  after  completing  the  titration,  to  read  the  burette,  add  0.5  cc. 
more  of  the  soap  solution  and  shake  well.  If  magnesium  has  been  respon- 
sible for  the  false  end-point,  after  such  addition  the  lather  will  again  dis- 
appear, and  titration  should  be  continued  until  a  new  and  true  end-point 
is  reached.  It  is  advisable  to  determine  the  strength  of  the  soap  solution 
from  time  to  time,  as  it  is  very  prone  to  change  upon  standing.  Results 
should  be  recorded  in  terms  of  calcium  carbonate,  parts  per  million.  There 
are  various  other  means  of  reporting.  The  English  degree  frequently  noted 
as  Clark  degree,  represents  grains  calcium  carbonate  per  Imperial  gallon  and 
should  be  multiplied  by  14.3  to  give  parts  per  million.  Conversely,  the  result 
obtained  in  parts  per  million  divided  by  14.3  will  give  Clark,  or  English  degrees. 
French  degrees  represent  parts  per  100,000  calcium  carbonate  and  should  be 
multiplied  by  10  to  give  parts  per  million.  Conversely,  division  of  the  result 
obtained  above  by  10  will  give  French  degrees.  German  degrees  represent  parts 
per  100,000  calcium  oxide  and  should  be  multiplied  by  17.8  to  give  parts  per 
million  calcium  carbonate.  The  determination  of  hardness  is  not  reliable  on 
account  of  the  varying  action  of  calcium  and  magnesium  salts,  and  should  never 
be  resorted  to  when  possible  to  determine  these  bases  direct. 

NOTE.  Dr.  Hale  claims  that  the  soap  method  for  hardness  in  skilled  hands  is 
accurate  from  10  to  15  parts  per  million  on  waters  as  hard  as  300  parts. 

For  permanent  hardness  the  standard  soap  solution  is  used  as  above  stated. 
The  water,  however,  is  boiled  gently  for  one-half  hour,  allowed  to  cool,  made  to 
volume  with  boiled  and  cooled  distilled  water  and  filtered,  after  which  the  above 
method  is  used.  The  difference  between  total  hardness  and  permanent  hardness 
is  supposed  to  represent  temporary  hardness.  The  alkalinity  determination  given 
on  a  previous  page  is  a  much  more  accurate  method  of  determining  temporary 
hardness,  however,  and  is  also  much  more  easily  carried  out.  When  total  hard- 
ness and  alkalinity  are  determined,  permanent  hardness  would  be  the  difference 
between  these  two  figures.  For  comparative  use  as  against  total  and  perma- 
nent hardness  determined  as  such,  the  results  would  be  much  different,  as  the 
alkalinity  determination  of  all  the  carbonates  would  give  a  permanent  hardness 
representing  absolutely  non-carbonate  hardness;  whereas  the  determined  per- 
manent hardness  would  contain  a  material  amount  of  combined  carbonates  of 
lime  and  magnesia.  The  American  Public  Health  Association,  Committee  on 
Standard  Method  of  Water  Analysis,  recommend  that  the  determination  of  per- 
manent hardness  by  the  soap  solution  be  discontinued  in  connection  with  softening 
process,  as  it  is  so  unsatisfactory  in  general  practice. 

Magnesium  Chloride 

Frequently,  when  hypothetical  combinations  are  used  it  is  desired  to  chirk 
up  these  calculated  combinations  by  some  chemical  method.  Magnesium  chloride 
is  frequently  produced  in  the  course  of  hypothetical  combinations  and  its  presence 
is  as  frequently  a  source  of  much  trouble  in  the  determination  of  a  mineral  residue, 
owing  to  the  ease  with  which  it  decomposes  or  carbonates.  A  method  is  suggested 


WATER  ANALYSIS  561 

whereby  a  second  50  cc.  portion  similar  to  the  total  mineral  residue  is  exactly 
neutralized  with  sufficient  H2S04,  the  amount  to  use  being  calculated  from  the 
total  alkalinity  obtained  elsewhere.  The  solution  is  allowed  to  go  to  complete 
dryness,  is  baked  at  a  temperature  of  280°  F.  to  300°  F.,  and  after  being  cooled 
the  chlorine  is  titrated.  The  difference  between  the  chlorine  thus  determined 
and  the  total  chlorine  previously  determined  represents  chlorine  lost  by  volatil- 
ization as  magnesium  chloride.  In  the  absence  of  organic  matter  this  method 
is  approximately  accurate.  Where  organic  matter  or  other  reducing  material  is 
present,  however,  the  results  are  not  so  satisfactory. 

Calcium   Sulphate 

In  a  similar  manner  it  is  frequently  desired  to  know  whether  or  not  a  water 
would  contain  calcium  sulphate,  and  a  method  of  comparative  satisfaction  depends 
upon  the  evaporation  of  250  cc.  to  500  cc.  of  the  original  water  to  dryness.  After 
cooling,  10  cc.  of  distilled  water  are  added  and  the  mineral  matter  loosened  from 
the  sides  of  the  dish  and  partially  dissolved.  Ten  cc.  of  95%  alcohol  are  then 
added  and  100  cc.  of  50%  alcohol.  After  thorough  stirring  and  solution  this 
material  is  filtered,  the  precipitate  washed  with  50%  alcohol  and  the  nitrate  made 
to  volume,  divided  and  tested  for  calcium  and  sulphates  in  the  usual  manner. 
The  method  is  only  approximate. 


LIME  AND   SODA  VALUE1 

Two  very  simple  methods  have  been  devised  for  the  rapid  estimation  of  the 
amount  of  lime  and  soda-ash  necessary  for  softening,  when  water  treatment  is 
considered  from  the  outside  softening-plant  point  of  view. 

Value  for  Lime 

Reagents.  Saturated  lime  water  (strength  to  be  known  for  each  series  of 
determinations).  N/10  hydrochloric  acid. 

Process.  Take  200  cc.  of  the  water  in  question;  add  50  cc.  saturated  lime- 
water  solution  in  250-cc.  volumetric  flask  and  heat  to  boiling.  Allow  to  cool. 
Fill  to  the  250-cc.  mark  with  water  to  replace  that  lost  by  evaporation;  filter 
through  a  dry-folded  filter  and  titrate  200  cc.  of  the  filtrate  with  N/10  acid,  using 
methyl  orange  as  an  indicator. 

For  calculation,  let  "  a  "  equal  number  of  cc.  N/10  calcium  oxide  in  50  cc. 
the  lime  water,  as  determined:  and  let  "  b  "  equal  the  number  cc.  N/10  hydro- 
chloric acid  used  in  determination. 

(4a— 5b)X3.51  CaO  will  give  milligrams  of  lime  per  liter  required  to  soften 
the  water  tested. 

Value  for  Soda 

To  the  neutralized  200  cc.  from  above  titration,  add  20  cc.  N/10  sodium 
carbonate.  Heat  to  boiling.  Transfer  with  C02  free  distilled  water  into  a  250- 
cc.  flask  to  make  up  to  mark  with  washings  from  the  dish;  mix  thoroughly  and 
filter,  collecting  200  cc.  of  the  filtrate  in  a  beaker.  Titrate  with  N/10  hydro- 

1  Drawe,  Zeit.  f .  Angew.  Chem.,  23,  52,  1910. 


562 


WATER  ANALYSIS 


chloric  acid  for  the  excess  alkali.     Designate  the  number  of  cc.  in  this  titration 
by  "  c." 

Formula:  (20-b— £c)X33.13  Na2C03  =  milligrams  of  soda  per  liter  necessary 
to  soften  water  in  question. 

NOTE.  Both  formulae  are  based  upon  C.  P.  chemicals,  and  corrections  must  be 
made  for  the  value  of  the  commercial  materials  in  use.  These  methods  are  valuable, 
though  for  actual  practice  it  is  advisable  to  try  out  on  a  liter  of  water  in  question, 
using  the  calculated  amounts  of  lime  and  soda  for  experimental  purposes. 

METHODS  OF  REPORTING  AND  INTERPRETATION 

The  manner  of  reporting  the  results  of  a  mineral  analysis  of  any  water  calls 
for  as  much  thought  and  uniformity  as  the  methods  of  analysis  themselves,  and 
in  this  department  there  is  much  less  uniformity  than  in  the  case  of  analytical 
methods.  Undoubtedly,  the  ideal  method  of  reporting  is  that  which  gives  results 
in  Ionic  form  (positive  and  negative  radicals),  in  terms  of  parts  per  million  or 
grains  per  gallon.  The  latter  term  is  purely  American  and  would  have  to  be 
converted  for  comparison  with  results  obtained  in  almost  any  foreign  country. 
Parts  per  million,  though  newer  and  still  unfamiliar  to  all  but  professional  and 
scientific  men,  is  gaining  gradually  a  strong  foothold,  and  the  consideration  of 
this  terminology  with  the  Ionic  form  of  reporting  will  be  considered  prior  to  the 
discussion  of  hypothetical  combination  and  grains  per  gallon. 

Mr.  Herman  Stabler,1  and  R.  B.  Dole,2  of  the  United  States  Geological 
Survey,  have  devised  and  simplified  certain  calculations  and  formulas,  which 
greatly  assist  in  the  interpretation,  comparison,  and  classification  of  waters  for 
Industrial  and  Irrigation 3  purposes.  Formulas  with  reference  to  dissolved  solids 
will  be  the  only  ones  discussed  here.  The  following  table  gives  reaction  coefficients : 


Positive  Radicals. 

Reaction 
Coefficients. 

Negative  Radicals. 

Reaction 
Coefficients. 

Ferrous  Iron  (Fe)  
Aluminum  (Al) 

0.0358 
.1107 
.0499 
.0822 
.0435 
.0256 
.992 

Carbonate  (CO«)  

0.0333 
.0164 
.0208 
.0282 
.0161 

Bicarbonate  (HCO8)  

Calcium  (Ca) 

Sulphate  (SO4)  

Macrnesium  (]Mc) 

Chlorine  (Cl) 

Sodium  (Na)..  . 

Nitrate  (N03)  

Potassium  (K)    

Hydrogen  (H)  

Using  the  above  table,  the  parts  per  million  of  each  radical  multiplied  by  its 
reacting  coefficient  will  give  its  reacting  value,  and  in  the  formulas  which  follow 
this  will  be  indicated  by  "  r  "  prefixed  to  the  chemical  symbol  of  the  radical. 

For  checking  the  accuracy  of  the  analysis,  the  sum  of  the  positive  reacting 
values  should  equal  the  sum  of  the  negative  reacting  values,  and  the  formula, 

100  r'  -r>°8'  ,  r  XTeg'  =E,  the  percentage  error  of  the  analysis.    The  value  of  tin's 
r.  Pos.+r  Neg. 

error  should  never  exceed  5  for  waters  of  100  p. p.m.  or  more  dissolved  solids,  and 
should  be  2  or  less. 

*Eng.  News,  60,  355,  1909. 

2  Water  Supply  Paper  No.  274,  p.  165,  Water  Supply  Paper  No.  254,  J.  Ind.  and 
Eng.  Chem.,  6,  (1914),  No.  7,  p.  710. 

3  U.  S.  G.  S.  W.  S.  Paper,  274,  p.  177. 


WATER  ANALYSIS  563 

In  ordinary  analysis,  silica,  iron  and  aluminum  are  present  in  such  small  quan- 
tities that  they  may,  for  simplicity's  sake,  be  ignored.  The  following  formulas 
are  given  without  comment,  as  full  details  can  be  found  iu  Water  Supply  Paper 
No.  274. 

Water  Softening 

For  1000  Gals.  Water.    Pounds  lime  (90%  CaO)  required 

=0.26(rFe+rAl+rMg+rH+rHC03+.0454COz). 

Pounds  soda  ash  (95%  Na2C03)  required 

=0.465(rFe+rAl+rCa+rMg+rH  -rC03  -rHC03). 

NOTE.  Dr.  Hale  states  the  following.  Instead  of  the  extended  formulaB  of  the 
Ionic  system,  I  much  prefer  my  simple  formulae. 

(Alkalinity X. 44+ free  CO2)  X.0106      =lbs.  CaO  per  1000  gals,  feed  water. 
Also  (Total  hardness -total  lime)  X. 0047  =  lbs.  CaO  per  1000  gals,  feed  water. 

or  total  magnesia  as  CaCO3. 

(Total  hardness  -  alkalinity)  X  .009    =  Ibn.  Na2C03  per  1000  gals,  feed  water. 
Expressed  as  CaCO3. 

Foaming  and  Priming 

Foaming  coefficient  F  =2.7  Na. 

Taking  into  consideration  the  various  boilers  and  the  action  of  various  waters 
in  practice,  the  following  approximate  classification  of  waters  for  foaming  con- 
ditions is  of  value : 

Non-foaming,    F  =  60  or  less. 
Semi-foaming,  F=  60-200. 
Foaming,  F  =200  or  more. 

Corrosion 

For  Add  Waters 
Coefficient  of  corrosion  C  =  1.008(rH+rAl+rFe+rMg-rC08-rHC03). 

For  Alkaline  Waters 
C=rMg-rHC03. 

If  C  is  positive,  water  will  corrode. 

If  C+.0503  Ca  is  negative,  water  will  not  corrode  on  account  of  the  mineral 
materials  in  the  water. 

If  C  is  negative,  but  C  —  .0503  Ca  is  positive,  the  water  may  or  may  not  corrode. 

Scale 

Si02+2.95  Ca+1.6G  Mg=scale  p.p.m., 
or 

1  (.00833  Sm-f- .00833  Cm+.3  rFe+.142  rAl)+.168  rMg+.492  rCa 

= scale  Ibs.  per  1000  gallons. 

1  Can  be  omitted  or  ignored  unless  suspended  matter,  silica,  etc.,  are  present  in 
large  quantities. 


564 


WATER  ANALYSIS 


There  are  also  formulas  given  in  the  above-mentioned  Bulletin  on  soap  cost, 
lime,  soda,  soda  ash,  cost  hard  scale  (pounds  per  1000  gallons)  and  a  hardness 
coefficient  of  the  scale  formation. 

Irrigating  Waters 

Alkali  Coefficient 
(a)  When  Na  — .65  Cl  is  zero  or  negative. 

Alkali  coefficient,  k=         . 

(6)  When  Na-.65  Cl  is  positive,  but  not  greater  than  .48  S04, 
Alkali  coefficient,  k=^f^. 

(c)  When  Na-.65  C1-.48  S04  is  positive, 

Alkali  coefficient,  k  =  — -  -— . 


Classification  on  basis  of  alkali  coefficient : 


Alkali  coefficient. 

Class. 

Remarks. 

More  than  18  ... 
18  to  6  

Good.  .  . 
Fair.  .  .  . 

Have  been  used  successfully  for  many  years  without  special 
care  to  prevent  alkali  accumulation. 
Special  care  to  prevent  gradual  alkali  accumulation  has 

5.9  to  1.2  

Poor.  .  . 

generally  been  found  necessary  except  on  loose  soils  with 
free  drainage. 
Care  in  selection  of  soils  has  been  found  to  be  imperative  and 

Less  than  1.2.  .. 

Bad.  .  .  . 

artificial  drainage  has  frequently  been  found  necess;n-\. 
Practically  valueless  for  irrigation. 

Hypothetical   Combinations 

The  use  of  hypothetical  combinations  in  the  reporting  of  a  mineral  water  is 
frequently  of  value,  in  that  it  gives  a  more  rapid  way  of  placing  in  simpler  terms 
the  principal  materials  present  in  the  water.  It  should  never  be  assumed  from 
the  hypothetical  combinations  that  the  materials  so  reported  are  present  in  the 
water  in  that  particular  form,  but  it  is  assumed  by  most,  that  the  form  in  which 
such  materials  are  reported  will  represent  the  condition  in  which  those  materials 
will  combine  when  the  water  is  subjected  to  increased  pressure  and  increased 
temperature.  In  other  words,  the  hypothetical  combinations  most  generally  in 
use  represent  the  way  materials  will  appear  when  combined,  due  to  the  law  of 
mass  action  under  steam-boiler  conditions. 

For  such  purpose  the  method  which  takes  care  of  the  insoluble  materials  <>r 
materials  leaving  the  water  first  is  the  most  common  method  in  use.  This 
method  combines  as  follows:  Where  the  sum  of  the  sulphate  and  carbonate  radicals 
exceeds  that  of  lime  and  magnesia  as  bases,  the  magnesia  is  first  calculated  to 
carbonate,  the  remaining  carbonate  is  combined  with  lime,  the  remaining  lime 


WATER  ANALYSIS  565 

with  sulphate  and  the  remaining  sulphate  with  sodium.  This  also  takes  care 
of  the  general  condition  where  the  carbonates  alone  are  in  excess  of  the  com- 
bined carbonates  of  lime  and  magnesium,  in  which  case  the  remaining  carbonate 
naturally  would  be  calculated  to  sodium  and  all  the  sulphate,  as  well  as  chloride, 
also,  calculated  to  sodium.  Where,  however,  the  sum  of  the  bases  is  greater 
than  the  sum  of  the  carbonate  and  the  sulphate  radicals,  two  possible  conditions 
or  combinations  exist.  Where  magnesium  chloride  is  present  in  the  water,  the 
sum  of  the  acids  calculated  to  the  soda  radical  should  be  greater  than  the  total 
mineral  residue.  Partially  decomposed  magnesium  chloride  is  indicated  in  this 
way,  also  the  fact  that  magnesium  chloride  has  a  lower  molecular  weight  than 
sodium  chloride,  which  condition  would  be  indicated  in  such  a  comparison.  When 
this  case  exists,  the  sulphate  is  first  calculated  to  calcium,  the  remaining  calcium 
to  carbonate,  the  remaining  carbonate  to  magnesium,  the  remaining  magnesium 
to  chloride,  the  remaining  chloride  to  sodium.  Where  the  total  mineral  residue 
is  greater  than  the  sum  of  the  acids  and  where  nitrates  are  present,  we  then  have 
nitrate  of  lime,  which  is  assumed  the  commoner  form  than  nitrate  of  magnesium, 
and  the  calculations  are  as  follows :  All  the  sulphate  is  calculated  to  lime,  all  the 
magnesium  to  carbonate,  the  remaining  carbonate  to  lime,  the  remaining  lime  to 
nitrate,  the  remaining  nitrate  to  sodium,  and  all  the  chlorides  to  sodium.  In  acid 
waters  naturally  the  lime  and  magnesia,  as  well  as  the  iron  and  aluminum,  are 
calculated  to  the  acid  present  in  the  greatest  excess.  These  methods  of  calculation 
will  give  certain  materials  frequently  found  in  scale  formation  and  materials 
frequently  supposed  to  cause  certain  characteristic  troubles  in  either  steam  or 
domestic  usage.  It  is  possible  in  a  purely  qualitative  way  to  judge  or  interpret 
the  water  on  the  basis  of  the  lime  and  magnesium  salts,  for  incrustation,  and  of 
the  alkali  salts  for  other  troubles  in  boiler  practice,  also  from  the  standpoint  of 
irrigation,  the  various  forms  of  the  alkali  salts  as  black  and  white  alkali,  without 
the  necessity  to  use  the  formulas  already  considered. 

Field  Assay  of  Water 

Mr.  R.  B.  Dole  has  published  in  Water  Supply  Paper  No.  151,  of  the  U.  S. 
Geological  Survey,  field  methods  for  the  assay  of  water  in  which  tablets  of  known 
value  are  used  for  the  determination  of  chlorides,  carbonates,  sulphates  and  iron. 
In  this  type  of  assay,  a  given  amount  of  the  water  is  taken  and  tablets  are  added  to 
the  water  until  certain  definite  reactions  take  place,  when  the  number  of  tablets 
used  is  estimated  and  an  approximate  value  obtained.  The  error  in  such  work 
varies  from  3  to  15  per  cent,  but  the  results  of  the  test  give  valuable,  if  not 
accurate,  information. 

The  author  is  indebted  to  Dr.  F.  E.  Hale,  Director  of  Laboratories  Depart- 
ment of  Water  Supply,  New  York  City,  for  a  careful  review  of  this  chapter,  and 
for  valuable  suggestions. 


FIXED  OILS,   FATS  AND  WAXES 

AUGUSTUS  H.  GILL  l 

It  will  be  remembered  that  the  fixed  oils  are  those  which  leave  a  permanent 
stain  on  paper,  whereas  the  essential  or  volatile  oils  evaporate.  The  fixed  oils, 
if  saponifiable,  are  glycerides  of  the  higher  fatty  acids,  oleic,  CnHssCOOH,  stearic, 
CnH35COOH,  palmitic,  Ci6H3iCOOH;  and  if  unsaponifiable,  hydrocarbons, 
usually  of  the  paraffin  (CnH2n+2)  and  olefin  (CnH2n)  series.  The  fats  differ  from 
the  oils  in  having  a  higher  melting-point,  caused  by  a  larger  percentage  of 
stearic  and  palmitic  acid.  The  waxes  differ  from  the  oils  or  fats  in  that  the 
former  are  esters  of  monatomic  alcohols.  The  oils  are  further  divided  according 
to  their  drying  power  on  exposure  to  the  air,  into  drying,  semi-drying  and  non- 
drying  oils. 

The  drying  oils  contain  a  large  proportion  of  glycerides  of  the  unsaturated 
acids,  particularly  linoleic  and  linolenic,  whereas  the  semi-drying  contain  a  smaller 
percentage,  and  the  non-drying  little  or  none  of  these  esters. 

Examination  of  an  Unknown  Oil 

There  being  no  specific  tests  for  the  various  oils,  as  for  their  identification,  the 
analyst  should,  in  attacking  an  unknown  oil,  ascertain  all  possible  facts  about  it, 
as  the  source,  the  use  to  which  it  is  put,  and  the  cost. 

Certain  physical  properties  too,  may  aid  in  the  examination.  The  color 
is  of  little  assistance,  as  oils  may  be  colored  by  the  use  of  oleates  or  butyrates  of 
iron  or  copper.  Fluorescence  or  "  bloom  "  is  valuable  as  indicating  the  presence 
of  mineral  oil;  this  can  be  shown  by  placing  a  few  drops  of  the  oil  on  a  sheet 
of  ebonite  and  observing  the  bluish  color.  The  odor  and  taste  are  particularly 
valuable.  Marine  animal  oils  are  detected,  especially  when  warm,  by  their 
strong  "  fishy  "  odor,  while  neatsfoot,  tallow,  lard,  rosin  and  linseed  oils  each  have 
a  well-marked  and  easily  distinguishable  smell.  Whale  oil  is  said  to  have  a 
"nutty,"  and  rape  oil  has  a  harsh,  unpleasant  "turnipy"  taste.  The  tur- 
bidity, showing  the  presence  of  water,  or  of  oils  which  imperfectly  mix — as  castor 
and  mineral  oils — and  the  sediment,  either  stearin  or  dirt,  are  also  to  be  noted; 
these  should  be  filtered  out  through  paper  before  the  oil  is  analyzed. 

The  elaidin  test  (page  582)  may  be  applied  next,  to  allow  time  for  the  cake  to 
form;  it  will  be  followed  by  the  Maumene  test  (page  582)  both  being  done  in 
duplicate.  In  making  the  elaidin  test  it  is  advisable  to  carry  on  an  experiment 
under  the  same  conditions  with  a  known  sample  of  lard  oil.  These  two  tests 
will  show  whether  the  sample  under  examination  is  a  drying  or  non-drying  oil  and 
when  the  ingredients  of  the  mixture  are  determined,  the  results  of  the  Maumen6 
test  can  be  used  for  calculating  their  relative  amounts.  The  iodine  test  can  be 
employed  to  check  this  result. 

1  Professor  of  Technical  Analysis  at  Massachusetts  Institute  of  Technology,  Cam- 
bridge, Mass. 

566 


FIXED   OILS,  FATS  AND  WAXES 


567 


The  saponification  test,  unless  mineral  or  rosin  oil  be  suspected,  need  rarely  be 
resorted  to;  the  reason  being  that  it  would  show  practically  nothing  regarding 
the  nature  of  the  oil.  Except  in  the  case  of  castor  (Sapn.  No.  181),  rape 
(174),  sperm  (135)  and  cocoanut  (260),  this  characteristic  is  about  193. 

Finally,  where  the  importance  of  the  case  will  warrant,  the  analyst  is  advised 
to  prepare  a  mixture  of  oils  using  the  proper  proportions  indicated  by  the  various 
tests,  and  subject  it  to  the  more  rapid  tests  as  the  specific  gravity,  viscosity, 
Maumene*  and  iodine  number.  In  making  out  the  report  of  analysis  it  should 
be  borne  in  mind  that,  excepting  in  the  case  of  the  special  test,  the  results  of 
one  test  cannot  be  relied  upon  to  determine  the  nature  of  an  oil,  but  the  evidence 
of  all  the  tests  here  given  should  be  carefully  compared  and  weighed  before 
rendering  a  final  verdict:  in  consideration  of  the  fact  of  the  wide  variation  of  the 
characteristics  of  the  oils,  it  is  futile  to  report  the  quantities  of  oil  found  in  a 
mixture  more  closely  than  1%. 


PETROLEUM  PRODUCTS 
(a)   Burning  Oils 

The  tests  or  determinations  to  be  made  are,  in  the  order  of  their  importance, 
flash,  fire,  specific  gravity,  distillation,  sulphur,  free  acid,  sulphuric  acid,  mineral 
salts  and  water.  In  some  cases  the  color  is  determined. 

Flash  Test  or  Point.  By  flash  point  we  understand  the  lowest  temperature 
to  which  an  oil  must  be  heated,  to  give  off  vapors  which  when  mixed  with  air  pro- 
duce an  explosive  mixture.  The  results  of  this  test  will  vary  according  to  the 
quantity  of  air  over  the  surface  of  the  oil,  and 
whether  this  be  moving  or  still;  also  according 
to  the  distance  of  the  testing  flame  from  the 
surface  of  the  oil.  Furthermore,  the  size  of 
this  testing  flame,  the  length  of  its  time  of 
action,  its  form  and  dimensions,  and  lastly,  the 
manner  of  heating  the  oil,  will  all  influence 
the  result.1 

Any  cause  producing  the  rapid  evolution  of 
a  large  amount  of  petroleum  vapor  tends  to 
lower  the  flash  point.  Barometric  changes  are, 
for  practical  work,  negligible,  each  5  mm.  caus- 
ing a  variation  of  but  0.1°  C. 

Determination  by  the  "New  York  State 
Board  of  Health  Tester/'  The  apparatus, 
Fig.  86,  consists  of  a  copper  oil  cup,  D,  hold- 
ing about  10  oz.,  the  quantity  usually  contained 
in  lamps,  heated  in  a  water  bath  by  a  small 
Bunsen  flame.  The  cup  is  provided  with  a 
glass  cover,  C,  carrying  a  thermometer,  B,  and  a  hole  for  the  insertion  of  the 
testing  flame — a  small  gas  flame  one-quarter  of  an  inch  in  length. 

Manipulation.    After  describing  the  apparatus  minutely,  the  regulations  of 


FIG.  86.— N.  Y.  Tester. 


Engler  and  Haase,  Z.  Anal.  Chem.,  20,  3,  1881. 


568  FIXED  OILS,   FATS  AND  WAXES 

the  New  York  State  Board  of  Health  say,1  "  (2)  The  test  shall  be  applied  ac- 
cording to  the  following  directions: 

"  Remove  the  oil  cup  and  fill  the  water  bath  with  cold  water  up  to  the  mark 
on  the  inside.  Replace  the  oil  cup  and  pour  in  enough  oil  to  fill  it  to  within  one- 
eighth  of  an  inch  of  the  flange  joining  the  cup  and  the  vapor-chamber  above. 
Care  must  be  taken  that  the  oil  does  not  flow  over  the  flange.  Remove  all  air- 
bubbles  with  a  piece  of  dry  paper.  Place  the  glass  cover  on  the  oil  cup,  and  so 
adjust  the  thermometer  that  its  bulb  shall  be  just  covered  by  the  oil. 

"  If  an  alcohol  lamp  be  employed  for  heating  the  water  bath,  the  wick  should 
be  carefully  trimmed  and  adjusted  to  a  small  flame.  A  small  Bunsen  burner 
may  be  used  in  place  of  the  lamp.  The  rate  of  heating  should  be  about  two 
degrees  per  minute,  and  in  no  case  exceed  three  degrees. 

"  As  a  flash  torch,  a  small  gas  jet  one-quarter  of  an  inch  in  length  should  be 
employed.  When  gas  is  not  at  hand  employ  a  piece  of  waxed  linen  twine. 
The  flame  in  this  case,  however,  should  be  small. 

"  When  the  temperature  of  the  oil  has  reached  85°  F.  the  testings  should  com- 
mence. To  this  end  insert  the  torch  into  the  opening  in  the  cover,  passing  it  in 
at  such  an  angle  as  to  well  clear  the  cover,  and  to  a  distance  about  half-way 
between  the  oil  and  the  cover.  The  motion  should  be  steady  and  uniform,  rapid 
and  without  any  pause.  This  should  be  repeated  at  every  two  degrees'  rise 
of  the  thermometer  until  the  temperature  has  reached  95°,  when  the  lamp 
should  be  removed  and  the  testings  should  be  made  for  each  degree  of  temper- 
ature until  100°  is  reached.  After  this  the  lamp  may  be  replaced  if  necessary 
and  the  testings  continued  for  each  two  degrees. 

"  The  appearance  of  a  slight  bluish  flame  which  passes  over  the  entire  sur- 
face shows  that  the  flashing-point  has  been  reached. 

"  In  every  case  note  the  temperature  of  the  oil  before  introducing  the  torch. 
The  flame  of  the  torch  must  not  come  in  contact  with  the  oil. 

"  The  water  bath  should  be  filled  with  cold  water  for  each  separate  test,  and 
the  oil  from  a  previous  test  carefully  wiped  from  the  oil  cup." 

For  the  determination  with  the  open  tester  (Tagliabue's  small)  reference 
may  be  had  to  the  author's  "  Short  Handbook  of  Oil  Analysis";  for  the  test  with 
the  closed  tester,  Abel's  or  Abel-Pensky,  or  Holde's  "Examination  of  Hydrocarbon 
Oils  "  translated  by  Mueller. 

Fire  Test.  The  fire  test  of  an  oil  is  the  lowest  temperature  at  which  it  will 
give  off  vapors  which  when  ignited  will  burn  continuously.  It  is  made  by  con- 
tinuing to  heat  the  oil  (the  cover  being  removed  in  the  case  of  a  closed  tester 
without  slipping  out  the  thermometer)  at  the  same  rate  after  the  flash  test 
is  made  and  noting  the  point  as  indicated  above.  The  flame  is  extinguished  by  a 
piece  of  asbestos  board  and  the  heating  discontinued.  In  the  case  of  many 
illuminating  oils  this  point  is  from  10°  to  20°  F.  higher  than  the  flash  point. 

In  the  case  of  "  Mineral  Sperm  "  (300°  F.  fire  test  oil)  these  tests  should  be 
made  with  the  instrument  for  lubricating  oils  (page  576).  The  heating  should 
be  at  the  rate  of  10°  F.  per  minute,  and  the  testing  flame  first  applied  at  230°  F. 
and  then  every  seven  degrees  until  the  flashing-point  is  reached. 

The  most  satisfactory  way  of  making  these  tests  is  to  place  the  watch  upon  the 
desk  and  read  the  thermometer  at  the  expiration  of  every  minute,  noting  down 
each  reading  in  the  proper  column  in  the  laboratory  note-book. 

1  Report  of  the  New  York  State  Board  of  Health,  1882,  p.  495. 


FIXED   OILS,  FATS  AND  WAXES 


569 


Specific  Gravity:  (a)  By  the  Hydrometer.  A  hydrometer  jar  is  four-fifths 
filled  with  the  oil,  a  verified  Baume  hydrometer  introduced  into  it,  and  the 
depth  read  off  to  which  the  instrument  sinks  into  the  oil.  This  may  be  effected 
by  placing  a  strip  of  white  paper  back  of  the  jar  and  noting  the  point  at  which 
the  lower  meniscus  of  the  oil  touches  the  scale.  The  temperature  of  the  oil 
is  taken  at  the  same  time,  and  in  case  it  be  not  60°  F.  (15.5°  C.),  subtract  1°  Baume" 
from  the  hydrometer  reading,  for  every  10°  F.  it  is  higher  than  60°,  and  add  1° 
Baume  for  every  10°  F.  it  is  lower  than  60°  F.  In  practice  this  can  be  done 
by  Tagliabue's  "  Manual  for  Inspectors  of  Coal  Oil,"  which  gives  the  readings  at 
60°  F.  for  any  gravity  from  20°  to  100°  Baume,  between  20°  and  109°  F.  The 

140 


specific  gravity  may  be  found  by  the  formula1 


B°  representing  the  read- 


ing  Baume*  at  15.5°  C. 

(6)  By  the  Westphal  Balance.  This  is  a  specially  constructed  instrument, 
Fig.  87,  with  a  glass  plummet  carrying  a  thermometer  counterbalanced  by  a  weight. 
Upon  immersing  the  plummet  in  a 
liquid  the  positions  of  the  weights, 
which  must  be  added  to  restore  the 
equilibrium,  represent  the  specific  grav- 
ity directly.  The  largest  weight  repre- 
sents the  first  decimal  place,  the  next 
the  second,  and  so  on.  The  instrument 
is  placed  upon  a  level  table,  and  by 
means  of  the  leveling  screw  is  brought 
into  adjustment  —  i.e.,  so  that  the  point 
upon  the  beam  is  exactly  opposite  the 
point  upon  the  fixed  part. 

The  plummet  is  now  placed  in  the 
vial  or  balance  jar  containing  the  oil, 
cooled  to  15.5°  C.,  hung  upon  the  bal- 
ance, being  careful  completely  to  im- 
merse it  in  the  oil,  weights  added  to 
restore  the  equilibrium,  and  the  specific 
gravity  read  off  as  above  described. 

Care  should  be  taken  that  the  plum- 
met does  not  touch  the  sides  of    the 
jar  or  vial.    For  solid  fats  and  some  oils  the  specific  gravity  is  taken  at  100°  C., 
using  a  special  plummet. 

Distillation  Test:  Engler's  Method.  Engler  uses  a  special  boiling  flask, 
6.5  cm.  in  diameter,  with  neck  15  cm.  long,  and  with  the  side  tube  about 
9  cm.  from  the  springing  of  the  bulb;  this  is  connected  with  a  Liebig  condenser 
and  heated  by  a  small  lamp  with  a  shield. 

One  hundred  cubic  centimeters  of  the  oil  are  measured  into  the  boiling  flask 
and  distilled  at  the  rate  of  2  to  2.5  cc.  per  minute,  the  distillate  being  caught 
in  a  25-cc.  burette  or  graduate.  When  the  distillation  is  to  be  broken,  the  lamp 
should  be  taken  away  and  the  temperature  allowed  to  sink  20°  and  again  brought 
to  the  breaking  or  fractionating  point,  as  long  as  any  considerable  quantity  goes 
over.  The  distillation  is  first  broken  at  150°  C.,  and  then  each  50°  until  290°C. 


FIG.  87.— Wesphal  Balance. 


1  This  formula  applies  to  liquids  lighter  than  water. 


570  FIXED   OILS,   FATS   AND   WAXES 

is  reached ;  in  this  way  a  much  better  idea  of  the  value  of  the  oil  is  obtained  thaf 
if  the  distillation  were  allowed  to  proceed  continuously  between  these  points. 
The  lighter  portions,  for  example,  those  between  150  and  200°,  burn  much 
better  than  those  between  250  and  290°;  the  heavy  portions  of  American  petro- 
leum burn  much  better  than  those  of  the  Russian  oils. 

The  averages  from  four  samples  of  Caucasian  and  ten  samples  of  American 
oils  subjected  to  this  test  were  as  follows,  in  per  cent  by  volume:1 


Below  150°  C. 

150-290° 

Above  290°  C. 

Caucasian  p6trol6uin 

8  0 

86  6 

5  4 

American  petroleum 

16  9 

57  1 

26  0 

Determination  of  Sulphur.2  The  deleterious  effect  of  the  oxides  of  sulphur 
upon  hangings  and  bindings — as  well  as  upon  the  human  system — is  well 
known,  sulphuric  acid  being  their  ultimate  product.  The  sulphur  exists  in  com- 
bination, partly  as  compounds  formed  from  the  sulphuric  acid  used  in  refining 
and  partly  as  alkyl  sulphides.  Its  qualitative  detection  may  be  effected  by  heat- 
ing the  oil  to  its  boiling-point  with  a  bright  piece  of  sodium  or  potassium.  If 
sulphur  compounds  be  present,  a  yellowish  layer  is  formed  upon  the  metal. 
After  cooling  add  distilled  water  drop  by  drop  until  the  metal  is  dissolved,  and 
test  for  sulphides  with  sodium  nitroprusside. 

For  the  quantitative  determination  of  sulphur  1  to  li  grams  of  the  oil  are 
burned  in  a  calorimetric  bomb  containing  10  cc.  of  water  and  oxygen  under  a 
pressure  of  30  atmospheres.  A  lower  pressure  sometimes  gives  inaccurate  results. 
If  the  sample  contains  more  than  3%  sulphur,  the  bomb  is  allowed  to  stand 
in  its  water  bath  for  fifteen  minutes  after  ignition  of  the  charge.  The  bomb 
is  allowed  to  cool  fifteen  minutes,  opened,  and  its  contents  washed  into  a 
beaker.  If  the  bomb  has  a  lead  washer,  5  cc.  of  a  saturated  solution  of  sodium 
carbonate  is  added,  the  contents  are  heated  to  the  boiling-point,  boiled  for  ten 
minutes  and  filtered.  This  is  necessary  to  decompose  any  lead  sulphate  from 
the  washer.  The  united  washings  are  filtered  and  neutralized  with  HC1,  using 
methyl  orange  as  an  indicator.  The  neutralized  solution  is  poured  into  the 
tube  of  the  Jackson  turbidimeter,3  diluted  to  near  the  100-cc.  mark,  shaken, 
then  acidified  with  1  cc.  of  1  :  1  hydrochloric  acid,  made  up  to  the  mark  and 
mixed  well  by  shaking.  One  of  the  barium  chloride  tablets  is  then  dropped  in 4 
and  the  tube  closed  by  a  clean  rubber  stopper.  The  tube  is  then  tilted  up  and 
down,  causing  the  tablet  to  roll  back  and  forth  through  the  solution  by 
gravity.  When  the  precipitation  appears  to  be  complete,  the  remainder  of 
the  tablet  may  be  dissolved  by  rapidly  rotating  the  tube;  violent  shaking  should 
be  avoided.  The  turbid  liquid  is  transferred  to  a  beaker,  the  candle  lighted,  a 
small  quantity  of  the  liquid  poured  into  the  glass  tube  to  prevent  overheating 
and  cracking,  and  the  tube  put  in  place.  More  of  the  liquid  is  then  poured 
in,  allowing  it  to  run  down  the  side  of  the  tube,  rapidly  at  first,  until  the  image 
of  the  flame  becomes  dim,  then  more  slowly,  waiting  a  minute  after  each  addi- 

1  Veith,  "  Das  Erdoel,"  p.  244. 

2  Allen  and  Robertson,  Technical  Paper  26,  Bureau  of  Mines;  Chem.  Abstracts,  6, 
2997,  1912. 

»  Muer,  J.  Ind.  and  Eng.  Chem.,  3,  556,  1911. 

4  From  the  Frazer  Tablet  Co.,  Brooklyn,  N.  Y.;  or  1  gram  of  barium  chloride  in 
dilute  solution  can  be  slowly  added. 


FIXED  OILS,   FATS  AND  WAXES  571 

tion  until  the  liquid  in  the  tube  is  quiet,  and  continuing  thus  until  the  image  of 
the  flame  just  disappears.  The  depth  of  the  liquid  in  centimeters  is  noted 
and  the  weight  of  sulphur  found  from  the  table  on  pages  676  and  677.  The 
mixture  is  returned  to  the  beaker,  poured  back  and  forth  from  beaker  to  tube 
two  or  three  times  and  read  again  as  before. 

Or  the  barium  sulphate  can  be  determined  in  the  usual  way  gravimetric- 
ally.  In  case  a  turbidity  too  low  to  be  read  with  the  apparatus  be  obtained, 
a  larger  quantity  of  oil  must  be  used.  Gasolines  and  light  oils  can  be  weighed 
out  in  a  gelatin  capsule. 

The  percentage  of  sulphur  in  a  kerosene  should  not  exceed  0.05;  the  Penn- 
sylvania oils  contain  usually  0.02  to  0.03,  the  Lima  0.04  to  0.05.1 

Detection  of  Acidity.  Shake  equal  quantities  of  oil  and  warm  water  in  a 
test-tube,  pour  off  the  oil,  and  test  the  water  with  litmus  paper.  If  the  water  be 
strongly  acid,  the  quantity  may  be  determined  as  in  "  Free  Acid,"  page  596. 

The  acid  in  this  case  is  most  probably  sulphuric,  coming  from  the  refining 
process. 

Sulphuric  Acid  Test.  The  object  of  this  test  is  to  judge  of  the  degree  of 
refinement  of  the  oil,  a  perfectly  refined  oil  giving  little  or  no  color  when  sub- 
mitted to  the  process.  One  hundred  grams  of  oil  and  40  grams  of  sulphuric  acid, 
1.73  specific  gravity,  are  shaken  together  for  two  minutes  in  a  glass-stoppered 
bottle  and  the  color  of  the  acid  noticed.  For  comparative  work  this  color  is 
matched  by  solutions  of  Bismarck  brown.2 

Mineral  Salts.  Salts  of  calcium  or  magnesium  when  dissolved  in  the  oil 
diminish  its  illuminating  power;  their  action  is  to  form  a  crust  on  the  wick 
and  prevent  access  of  air. 

Redwood  3  states  that  0.02  gram  of  either  of  these  salts  in  1000  grams  of  oil 
diminishes  the  illuminating  power  30  to  40%  in  eight  hours. 

They  are  determined  by  distilling  100  to  200  cc.  of  the  oil  down  to  about  20 
cc.,  evaporating  and  igniting  this  residue,  and  subsequently  treating  with  hydro- 
chloric acid.  The  calcium  and  magnesium  are  then  determined  in  the  usual  way. 

Determination  of  Water.  By  rubbing  the  oil  together  with  a  little  eosin  on 
a  glass  plate  the  oil  will  take  on  a  pink  color  if  water  be  present. 

The  evaporation  method  is  approximate  and  applicable  only  to  heavy  oils 
and  greases.  Its  accuracy  even  with  heavy  greases  is  questionable. 

Dilute 4  the  oil  with  an  equal  volume  of  benzol,  whirl  it  vigorously  in  a  cen- 
trifuge until  the  separated  layer  of  water  does  not  appear  to  increase  in  volume. 
However,  as  water  is  somewhat  soluble  in  any  diluent  used  and  also  in  oils, 
a  portion  of  the  water  content  will  fail  to  appear,  consequently  the  method 
in  which  a  diluent  is  used  cannot  be  considered  accurate.  It  is  advisable  first 
to  agitate  the  diluent  vigorously  with  water  and  then  to  separate  with  the 
centrifuge  in  order  to  saturate  it  with  water  before  using. 

Groschuff 5  states  that  100  grams  of  benzene  will  dissolve  0.03  gram  of  water 
at  3°  C.  and  0.337  gram  of  water  at  77°  C.,  whereas  petroleum  products  (dens- 
ity 0.792)  will  dissolve  from  0.0012  gram  at  2°  C.  to  0.097  gram  at  94°  G. 

1  Kissling,  Ch.,  Rev.  Fett  und  Harz.  Ind.,  14,  157,  1906. 

2  J.  Soc.  Chem.  Ind.,  15,  678,  1896. 
J  Dingier,  Pol.  J.,  255,  427,  1887. 

4  Reported  by  Allen  and  Jacobs.     Bureau  of  Mines  Technical  Paper  No.  25,  1912. 

5  Groschuff,  E.,  "  The  Solubility  of  Water  in  Benzene,  Petroleum  and  Paraffin  in 
Oil,"  Chem.  Abs.,  5,  2550,  1911. 


572  FIXED   OILS,   FATS   AND   WAXES 

While  water  to  the  extent  even  of  3  or  4%  is  apparently  without  influence  on 
the  viscosity,  1%  extinguishes  the  flame  when  making  the  flash  test. 

Color.  This  test  has  lost  its  importance  since  oils  are  sometimes  satis- 
factory despite  their  yellow  color.  The  determination  is  usually  made  with  the 
Stammer  colorimeter  in  which  the  depth  of  the  oil  is  changed  in  a  cylinder  until 
it  matches  the  color  of  a  standard  plate  of  uranium  glass.  Standard  white 
oil  requires  a  depth  of  50  mm.  and  water  white  from  300-320  mm.  to  match  the 
color  of  the  plate. 

For  a  cut  of  the  instrument  and  method  of  using,  reference  may  be  had  to 
Holde's  "  Examination  of  Hydrocarbon  Oils,"  translated  by  Mueller,  page  52. 

(b)    Lubricating  Oils 

The  tests  to  be  made  are,  in  the  order  of  their  importance,  viscosity,  specific 
gravity,  evaporation,  cold  test,  flash  test,  fire  test,  test  for  soap,  carbon  residue 
test,  friction  test.  Saponification  value,  tarry  matter  insoluble  in  88°  naphtha, 
and  added  impurities  are  also  determined. 

The  office  of  a  lubricant  is  to  prevent  the  attrition  of  axle  and  journal  box  by 
interposing  itself  between  them  in  a  thin  layer,  upon  which  the  shaft  revolves. 
The  ideal  lubricant  is  that  which  has  the  greatest  adhesion  to  surfaces  and  the 
least  cohesion  among  its  own  particles,  or,  as  the  practical  man  expresses  it,  the 
most  fluid  oil  that  will  do  the  work  and  stay  in  place.  The  determination  of  its 
viscosity  or  "  body  "  is  then  of  the  first  importance. 

Viscosity  is  the  degree  of  fluidity  of  an  oil  or  its  internal  friction.  It  is  inde- 
pendent of  the  specific  gravity  of  the  oil,  although  this  in  the  pipette  instruments 
influences  the  time  of  efflux.  Within  certain  limits  it  may  be  taken  as  a  measure  of 
the  value  of  oil  as  a  lubricant,  by  comparing  the  viscosity  of  the  oil  under  examina- 
tion with  that  of  other  oils  which  have  been  found  to  yield  good  results  in  practice. 

The  instruments  employed  for  its  determination  may  be  divided  into  two 
classes — pipette  viscosimeters,  giving  the  time  of  efflux,  as  those  of  Engler, 
Saybolt,  and  others,  and  torsion  viscosimeters,  giving  the  retardation  due  to 
the  oil,  those  of  Macmichael  and  Doolittle. 

In  expressing  viscosity,  consequently,  it  is  necessary  to  give  the  name  of  the 
instrument  with  which  it  is  determined.  It  is  sometimes  expressed  as  specific 
viscosity,  that  is,  the  time  of  the  oil  divided  by  the  time  of  water;  this  is  only 
comparative  when  done  with  instruments  of  the  same  name,  that  is,  specific  vis- 
cosity Engler  is  not  the  same  figure  as  specific  viscosity  Saybolt.  Besides  this 
manner  of  expressing  viscosity,  it  is  occasionally  measured  in  absolute  (C.G.S.) 
units  or  dynes.  This  is  possible  when  the  diameter  of  the  orifice,  its  length,  the 
quantity  and  specific  gravity  of  the  oil,  its  time  of  efflux  and  change  of  head  are 
known.  Where  it  is  impracticable  to  determine  all  these  data,  by  direct  measure- 
ments, the  readings  of  a  viscosimeter  may  be  changed  into  dynes  by  determin- 
ing the  viscosity  in  seconds  of  standard  solutions  of  glycerine,  the  viscosity  of  these 
being  determined  in  dynes  from  tables  of  physical  constants.  Or  it  may  be  done 
by  use  of  the  the  tables  on  pages  575  and  608. 

Engler  Apparatus.  Description.  The  apparatus  (Fig.  88)  consists  of  a  flat, 
brass  cylindrical  vessel,  A,  106  mm.  in  diameter  and  about  62  mm.  deep,  holding 
240  cc.,  provided  with  a  jet  2.9  mm.  in  diameter  and  20  mm.  long.  This  vessel 
is  gilt  inside  and  the  jet,  in  the  standard  instruments,  is  of  platinum — ordinarily 
it  is  made  of  brass;  the  vessel  is  surrounded  with  a  bath,  B,  either  of  water  or 


FIXED    OILS,  FATS  AND  WAXES 


573 


oil,  provided  with  a  stirrer  and  heated  by  a  ring  burner.  The  jet  is  closed  by  the 
wooden  valve,  F,  passing  through  the  cover,  and  a  thermometer,  c,  shows  the 
temperature  of  the  oil;  three  studs  show  the  height  to  which  A  is  filled  and 
at  the  *  same  time  when  it  is  level.  The  oil 
ordinarily  is  discharged  into  the  200-cc.  flask, 
although  in  case  the  oil  or  time  be  limited,  100 
or  50  cc.  may  be  used  and  the  time  of  efflux 
multiplied  by  a  suitable  factor.  The  instrument 
is  standardized  with  water,  200  cc.  of  which  at 
20°  C.  should  run  out  in  from  50  to  52  seconds. 
Manipulation.  The  instrument  is  thor- 
oughly cleaned  with  alcohol  and  ether  if  neces- 
sary and  dried;  any  suspended  matter  is  removed 
from  the  oil,  which  is  poured  into  it  up  to  the 
level  of  the  studs,  stirred  until  20°  C.  is  reached 
and  the  bath  adjusted  to  the  same  temperature. 
The  flask  is  placed  beneath  the  orifice,  the  plug 
raised  and  the  time  required  for  200  cc.  of  oil 
to  flow  out  is  noted;  this  is  divided  by  the 
water  value  of  the  instrument  and  gives  then 
relative  or  specific  viscosity.  If  only  50  cc.  are 


FIG.  88. — Engler  Viscosimeter. 


omjj.o.fi 

c 

0 

0 
c 

A 

,_» 

0         ) 
c 

k+r-rdfy 

H: 

0 

|P          0         0 

T-fl 

fSj         frr* 

B* 

allowed  to  run  out  the  time  must  be  multiplied  by  5,  and  if  100  cc.,  by  2.35.     If 
only  50  cc.  were  put  in  and  40  cc.  allowed  to  run  out,  multiply  this  time  by  3.62 

to  obtain  the  time  for  200  cc.;  if  66  cc. 
and  50  cc.  run  out,  multiply  by  2.79. 1  If 
it  be  desired  to  express  the  viscosity  in 
absolute  measure  (C.G.S.  units)  it  can  be 
done  by  reference  to  the  table  on  page 
608.  It  should  be  noted  that  specific 
viscosity  obtained  with  a  different  type 
of  instrument,  e.g.,  the  Saybolt,  is  not 
the  same  as  with  the  Engler. 

The  Saybolt  Viscosimeter. z —  The 
Standard  Universal  Viscosimeter  is  the 
one  now  used  for  testing  cylinder,  valve, 
and  similar  oils  at  210°  F.;  reduced  black 
oils  at  130°  F.;  spindle,  paraffin,  red, 
and  other  distilled  oils  at  100°  F. 

The  Universal  Viscosimeter.  De- 
scription. This  consists  of  a  brass  tube, 

FIG.  89.— Saybolt  Viscosimeter.          ^»  forming  the  body  of  the  pipette  pro- 
vided with  a  jet,  K.    The  upper  part  of 
the  pipette  is  surrounded  with  a  gallery,  B,  which  enables  a  workman  to  fill  it  to 

1  Gans,  Chem.  Revue  der  Fett  und  Harz.  Ind.,  6,  221,  1899. 

2  Redwood,  J.  Soc.  Chem.  Ind.,  5,  124,  1886.     This  was  formerly  made  in  three 
forms,  A,  B,  C.     Apparatus  "  A  "  was  the  standard  for  testing  at  70°  F.  Atlantic  Red, 
Paraffin,  and  other  distilled  oils;    "  B  "  for  testing  at  70°  F.  Black  Oils  of  0°,  15°, 
25°,  and  30°,  Cold  Test,  and  other  reduced  oils  up  to,  but  not  including,  Summer  Cold 
Test  Oil.     Apparatus  "  C  "  was  used  for  testing  at  212°  F.  Reduced,  Summer,  Cylinder, 
Filtered  Cylinder,  XXX  Valve,  26.5°  Be.,  and  other  heavy  oils. 


574  FIXED   OILS,   FATS   AND   WAXES 

the  same  point  every  time.  The  pipette  is  contained  in  a  water  bath,  C,  which 
can  either  be  heated  by  steam  or  a  ring  burner,  D;  a  tin  cup  with  spout,  a  strainer, 
thermometer,  pipette  with  rubber  bulb,  stop  watch,  and  beaker  for  waste  oil 
complete  the  outfit.  It  may  be  used  for  testing  cylinder,  valve,  and  similar 
oils  with  bath  at  212°  and  oil  at  210°;  for  testing  reduced,  black  oils,  bath  and 
oil  at  130°;  for  testing  spindle,  paraffin,  red  and  other  distilled  oil  bath  and  oil 
at  100°.  When  used  for  testing  at  212°  F.,  it  may  be  used  with  either  gas  or  steam 
alone  or  both  in  combination.  If  with  both,  the  steam  may  be  introduced 
slowly,  more  for  its  condensation  to  replace  evaporation  than  for  real  heating  pur- 
poses, depending  upon  the  gas  flame  to  reach  the  boiling-point,  and  keeping 
it  there  during  the  operation  of  test.  The  bath  vessel  should  always  be  kept 
full  during  a  test,  whether  at  212°,  130°,  or  100°.  When  used  at  130°  or  100°, 
gas  alone  is  used  to  bring  the  bath  to  the  prescribed  temperature,  and  turned  off 
during  the  operation  of  test,  the  large  size  of  the  bath  usually  permitting  making 
one  test  without  reheating. 

Its  dimensions  are  as  follows:1 

Diameter  of  overflow  cup 51.0  mm. 

Depth  of  overflow  cup 13.0  mm. 

Diameter  of  pipette  A 30 . 0  mm. 

Depth  from  starting  head  to  outlet  jet 113 . 0  mm. 

Length  of  outlet  jet 13 . 0  mm. 

Diameter  of  outlet  jet 1.8  mm. 

Capacity  of  pipette  A 70  cc. 

Manipulation.  1.  Have  the  bath  of  water  prepared  at  the  prescribed  tem- 
perature. 

2.  Have  the  oil  strained  into  one  of  the  tin  cups,  in  which  cup  it  may  be 
heated  up  to  about  the  standard  temperature. 

3.  Clean  out  the  tube  with  some  of  the  oil  to  be  tested  by  using  the  plunger 
sent  with  the  instrument. 

4.  Place  the  cork  (as  little  distance  as  possible)  into  the  lower  outlet  coupling 
tube  just  enough  to  make  air-tight,  but  not  far  enough  to  nearly  touch  the  small 
outlet  jet  of  the  tube  proper  (one-eighth  to  one-quarter  of  an  inch  may  be  enough) . 

6.  Pour  the  oil  from  the  tin  cup  (again  through  the  strainer)  into  the  tube 
proper  until  it  overflows  into  the  overflow  cup  up  to  and  above  the  upper  edge  of 
tube  proper. 

6.  Now  again  see  that  the  bath  is  at  the  prescribed  temperature. 

7.  Use  the  thermometer  sent  with  the  instrument  by  stirring  to  bring  the 
oil  just  to  the  standard  temperature. 

8.  Remove  the  thermometer. 

9.  Draw  from  the  overflow  cup,  with  a  pipette,  all  the  surplus  oil  down  to  and 
below  the  upper  edge  of  tube  proper.     This  insures  a  positive  starting  head. 

10.  Place  the  60-cc.  flask  under  and  directly  in  line  with  the  outlet  jet,  and  as 
close  to  the  coupling  tube  as  is  practicable  to  permit  of  room  for  drawing  the  cork. 

11.  With  the  watch  in  left  hand  draw  the  cork  with  the  right,  and  simultane- 
ously start  the  watch. 

12.  The  time  required  in  the  delivery  of  60  cc.  is  the  viscosity. 

13.  Clean  out  the  tube  proper  before  each  test  with  some  of  the  oil  to  be  tested. 

14.  No  drill  or  other  instrument  should  ever  be  used  in  the  small  outlet  jet  of 
tube  proper. 

1  Private  communication. 


FIXED   OILS,   FATS  AND   WAXES 


575 


The  tube  should  be  cleaned  out  before  each  test  with  some  of  the  oil  to  be 
tested.  Black  oils  or  any  oil  containing  sediment  should  be  carefully  strained 
before  testing  or  "  running,"  as  it  is  technically  termed.  The  instruments  should 
be  carefully  guarded  from  dust  when  not  in  use. 

The  results  obtained  with  this  instrument  are  not  the  same  in  many  cases 
as  those  furnished  by  the  A,  B,  and  C  instruments,  but  they  seem  to  have  been 
adopted  by  the  trade  generally. 

It  is  worth  noting  that  3  or  4%  of  water  are  apparently  without  influence  on 
the  viscosity. 

Absolute  Viscosity.  This  expresses  viscosity  in  dynes,  that  is,  the  force  neces- 
sary to  produce  the  acceleration  of  1  cc.  per  second  on  the  mass  of  a  gram. 
It  is  independent  of  the  instrument  used;  Engler  numbers  can  be  converted  to 
absolute  viscosity  by  the  following  factors: 

Engler  No.  Absolute  Viscosity  Dynes  per  Sq.Cm.J 

1 0.0 1006 X specific  gravity 

2 0.1 146  Xspecific  gravity 

5   0 . 353     Xspecific  gravity 

10 0 . 726     Xspecific  gravity 

20 1 . 46       Xspecific  gravity 

30 2 . 19       Xspecific  gravity 

60 4.38       Xspecific  gravity 


The  Engler  numbers  of  5  or  over  are  quite  nearly  proportional  to  the  absolute 
viscosities. 

Specific  Gravity.    See  under  Burning  Oils,  page  569. 

Evaporation  Test.2  The  object  of  this  test  is  to  determine  what  percentage 
of  an  oil — more  especially  a  spindle  oil — is  volatile  when  exposed  to  nearly  the 
same  conditions  as  it  is  on  a  bearing. 

The  oil  is  exposed  upon  annular  disks  of  filter-paper  If  in.  outside  diameter, 
with  hole  j  in.  in  diameter,  which  have  been  standing  in  a  sulphuric  acid 
desiccator  for  several  days,  contained  in  a  flat  watch-glass. 

Manipulation.  The  watch-glass  and  paper  are  weighed — to  tenths  of  a  milli- 
gram— and  about  0.2  gram  of  oil  brought  upon  it  by  dropping  from  a  rod, 
and  accurately  weighed.  The  watch-glass  is  now  placed  in  an  air  bath,  the 
temperature  of  which  remains  nearly  constant  at  60°  to  65°  C.  (140°  to  150° 
F.),  and  heated  for  eight  hours.  It  is  then  cooled  and  re  weighed,  the  loss  being 
figured  in  per  cent.  No  oil  should  be  passed  which  gives  an  evaporation  of  more 
than  4%. 

The  following  table  of  results  upon  some  spindle  oils  shows  the  relation  of 
gravity,  flash  point,  and  evaporation: 


Gravity. 

Flash,  °F. 

Evaporation. 

Gravity. 

Flash,  °F. 

Evaporation. 

298 

7   0% 

862 

352 

0  9% 

.846 

318 
348 

4.4% 
2  0% 

.866 

870 

366 
384 

1.7% 
0  8% 

.852 
.856 

348 
336 

1.0% 

1-4% 

.882 

364 

1.7% 

1Waidner,  Proc.  Am.  Soc.  Test.  Mat.,  Pt.  I,  293,  1915. 
8  Archbutt,  J.  Soc.  Chem.  Ind.,  15,  326,  1896. 


576  FIXED   OILS,   FATS   AND   WAXES 

NOTES.  The  temperature  employed,  65°  C.,  is  approximately  that  attained  by 
a  bearing  (in  a  spinning  frame)  after  running  two  hours,  thus  leaving  the  oil  exposed 
to  it  for  eight  hours,  assuming  a  ten-hour  day. 

The  test  is  important  to  the  insurance  underwriter,  because  it  measures  the  amount 
of  inflammable  material  sent  into  the  air,  and  hence  the  liability  to  cause  or  aid 
conflagrations;  it  is  important  to  the  mill-owner,  as  it  indicates  the  quantity  of  oil 
left  upon  the  bearing,  hence  serving  its  purpose. 

The  test  is  made  upon  other  oils  by  heating  them  six  hours  in  a  shallow  dish  to 
100°,  150°,  220,  or  300°,  sometimes  in  a  draft  of  air. 

Cold  Test.  This  may  be  defined  as  the  temperature  at  which  the  oil  will  just 
flow. 

Manipulation.  A  4-oz.  vial  is  one-fourth  filled  with  the  oil  to  be  examined, 
a  short,  rather  heavy,  thermometer  inserted  in  it,  and  the  whole  placed  in  a 
freezing  mixture.  When  the  oil  has  become  solid  throughout,  let  it  stand 
one  hour;  the  vial  is  removed,  the  oil  allowed  to  soften,  and  thoroughly  stirred 
until  it  will  run  from  one  end  of  the  bottle  to  the  other.  The  reading  of  the 
thermometer  is  now  taken  by  withdrawing  it  and  wiping  off  the  oil  with  waste 
to  render  the  mercury  visible.1 

The  chilling-point  is  the  temperature  at  which  flakes  or  scales  begin  to  form 
in  the  liquid,  and  is  determined  similarly,  by  cooling  the  liquid  5°  at  a  time. 

Freezing  Mixtures.  For  temperatures  above  35°  F.  use  cracked  ice  and  water; 
between  35  and  0°  F.  use  two  parts  of  ice  and  one  part  of  salt;  and  from  0  to  -30°  F. 
use  three  parts  of  crystallized  calcium  chloride  and  two  parts  of  fine  ice  or  snow. 
A  still  more  convenient  means  is  by  the  use  of  solid  carbonic  acid  dissolved 
in  ether,  giving  —  50°  F.  readily. 

The  preceding  method  is  open  to  quite  an  error  from  the  personal  equa- 
tion of  each  observer.  To  obviate  this  Martens  2  proceeds  as  follows : 

The  oil  is  poured  into  a  U-tube  1  cm.  in  diameter,  16  cm.  high,  with  3  cm. 
between  the  bends,  to  a  depth  of  3  cm.;  it  is  then  placed  in  a  freezing  mixture, 
cooled,  and  connected  with  a  blast  at  a  constant  pressure  of  3  cm.  The  temper- 
ature at  which  the  oil  begins  to  flow  under  these  conditions  is  considered  as  the 
cold  test. 

Flash  Point.  Several  forms  of  apparatus  for  testing  the  flash  point  of  lubri- 
cating oils  have  been  devised:  Pensky-Martens's  closed  tester  employing  a  stirrer 
is  used  in  Germany.  Martens  states  in  a  later  article  that  stirring  is  unneces- 
sary. In  this  country  an  open  cast-iron  or  spun  brass  cup — the  Cleveland  open 
cup — If  in.  high  by  2£  in.  in  diameter,  heated  by  a  Tirrill  burner  in  an  air  bath  is 
quite  extensively  used.  Dudley  and  Pease  use  an  open  porcelain  dish  heated 
with  a  Bunsen  burner. 

The  cup,  Fig.  90,  is  filled  with  oil  to  about  J  in.  from  the  top  and  the 
thermometer  is  suspended  so  that  the  bulb  is  just  immersed  in  the  oil.  The 
oil  is  heated  at  the  rate  of  10°  F.  a  minute  by  a  Bunsen  burner  with  a  pro- 
tecting chimney;  as  the  flash  point  is  approached,  a  test  is  made  for  every  rise 
of  3°  by  slowly  passing  the  small  bead-like  test  flame  across  the  cup  near 
the  thermometer.  The  oil  should  flash  near  the  thermometer  when  the 
proper  point  is  reached.  The  fire  test  is,  as  a  rule,  50°  to  80°  F.  higher  than  the 
flash  point.  As  the  open-cup  tests  are  easily  affected  by  drafts,  they  are  subject 
to  errors  of  5°  F.  The  thermometers  used  should  be  compared  with  a  standard 

1  Dudley  and  Pease,  An.  Eng.  and  R.  R.  J.,  69,  332,  1895. 

*  Mitt.  kgl.  tech.  Versuchstation;  abstr.  J.  Soc.  Chem.  Ind.,  9,  772,  1890. 


FIXED   OILS,  FATS  AND  WAXES 


577 


and  corrected  for  stem  exposure.  When  this  is  done  it  is  suggested  that  "  corr.  " 
be  added  to  the  reading:  thus,  "  flash  379°  F.  corr." 

Fire  Test.  The  cover  is  supported  above  the  cup,  and  the  heating  and 
application  of  the  testing  flame  continued  as  in  making  the  flash  test. 

The  method  of  recording  is  the  same  as  in  the  case  of  the  illuminating  oils, 
one  column  for  times  and  another  for  temperatures.  Holde  1  finds  that  with  oils 


FIG.  90. — Cleveland  Cup. 

flashing  between  172°  C.  and  241°  C.  the  exact  quantity  of  oil  used  is  of  little 
importance.  In  these  particular  cases  a  difference  of  filling  of  13  cc.  altered  the 
flash  point  only  1-1.5°  C.  For  the  effect  of  water  see  page  572. 

It  is  worthy  of  notice  that  the  free  fatty  (oleic)  acid  contained  in  an  oil  lowers 
its  flash  point  apparently  in  proportion  to  the  quantity  present. 


1 J.  Soc.  Chem.  Ind.,  16,  322,  1897. 


578  FIXED   OILS,   FATS   AND   WAXES 

Detection  of  Soap.  To  increase  the  viscosity  of  an  oil,1  resort  is  had  to  the 
use  of  "  oil  pulp,"  "  oil-thickener,"  or  "  white  gelatin,"  usually  an  oleate  of 
aluminum,  though  other  bases  may  be  present.  Its  disadvantages  are  that  it 
causes  the  oil  to  chill  more  easily  and  to  emulsify,  thus  increasing  the  friction. 
Furthermore,  it  is  precipitated  by  contact  with  water  or  steam,  causing  clogging 
of  the  machinery. 

The  test  depends  upon  the  fact  that  the  metaphosphates  of  the  earthy  and 
alkali  metals  and  aluminum  are  insoluble  in  absolute  alcohol.2 

The  test  is  applied  as  follows:  five  to  10  cc.  of  the  oil  to  be  tested  are  dissolved 
in  about  5  cc.  of  86°  gasoline  or  ether,  and  about  15  drops  of  the  phosphoric  acid 
solution  (Appendix,  Reagents)  added,  shaken  and  allowed  to  stand;  the 
formation  of  a  flocculent  precipitate  indicates  the  presence  of  soap.  An  idea 
of  the  kind  of  soap  can  be  often  gained  by  adding  an  alcoholic  solution  of  PtCl4. 
If  the  precipitate  becomes  crystalline  it  is  a  potash  soap;  if  it  dissolves,  soda, 
lime,  or  magnesia;  if  unchanged,  alumina  or  iron. 

For  the  accurate  determination  of  these  compounds  a  known  weight  of  the 
oil  must  be  ignited,  the  residue  determined  and  quantitatively  examined. 

Caoutchouc.  Holde  3  states  that  1  to  2%  of  unvulcanized  caoutchouc  is  some- 
times added  to  oils  to  increase  their  viscosity.  This  may  be  detected  by  adding 
three  parts  of  alcohol  to  four  parts  of  the  ethereal  solution,  whereby  the  rubber 
material  is  precipitated  and  may  be  dried  and  weighed. 

Test  for  Fatty  Oils.  To  detect  small  quantities  of  fatty  oil  (1  to  2%)  Lux 4 
recommends  heating  a  few  cubic  centimeters  of  the  oil  for  fifteen  minutes  with 
some  bits  of  sodium  in  a  test-tube  in  an  oil  bath;  a  similar  test  is  made  with 
sodium  hydrate.  The  temperature  employed  should  be  for  light  oils  about  230°, 
for  dark  oils  250°. 5  In  case  fatty  oil  be  present,  the  contents  of  one  or  both 
of  the  tubes  solidify  to  a  jelly  of  greater  or  less  consistence  according  to  the 
amount  of  fatty  oil  present. 

The  quantitative  determination  of  these  oils,  as  for  example  in  cylinder  oils, 
is  effected  after  the  manner  of  determining  the  saponification  value  (page  587) 
or  the  detection  of  unsaponifiable  oils  in  fatty  oils  (page  588). 

Schreiber 6  adopts  a  method  similar  to  Sweetham  and  Henriques,  in  that  he 
dissolves  5  grams  of  the  oil  in  25  cc.  of  benzole,  adds  25-50  cc.  N/2  alcoholic 
potash,  and  boils  for  half  an  hour  on  the  water  bath,  using  a  3-ft.  glass  tube  as  a 
condenser. 

Gumming  Test.7  This  is  designed  to  give  an  idea  of  the  amount  of  a 
change  that  may  be  expected  in  a  mineral  oil  when  in  use.  These  resinified 
products  increase  the  friction  of  the  revolving  or  rubbing  surfaces.8  It  is  also  a 
measure  of  the  amount  that  an  oil  will  "  carbonize  "  in  a  gas  or  gasoline  engine 
cylinder.  It  is  applied  after  the  manner  of  the  elaidin  test,  by  thoroughly 
mixing  together  5  grams  of  the  oil  in  a  cordial  glass  with  11  grams  of  nitrosul- 

1  In  a  case  which  came  to  the  writer's  notice  the  oil  would  not  flow  out  of  the  Saj- 
bolt  "  A  "  apparatus  at  70°,  at  85°  required  1167",  and  at  110°,  181." 
•Schweitzer  and  Lungwitz,  J.  Soc.  Chem.  Ind.,  13,  1178,  1894. 

*  "  Examination  of  Hydrocarbon  Oils,"  p.  166. 
4  Z.  anal.  Chem.,  24,  357,  1885. 

6  Holde,  Untersuchung  d.  Schmierole  u.  Fette.  p.  175. 

•  J.  Am.  Chem,  Soc.,  29,  74,  1907. 

'  Gill,  J.  Am.  Chem.  Soc.,  24,  467,  1902. 

8  Aisinman,  J.  Soc.  Chem.  Ind.,  14,  282,  1895. 


FIXED   OILS,   FATS    AND  WAXES 


579 


phuric  acid  and  cooling  by  immersion  in  a  pan  of  water  at  10-15°.  Brownish 
spots  or,  in  case  of  a  bad  oil,  masses,  form  around  the  edges  and  become  red  in 
the  course  of  two  hours.  The  cordial  glass  is  filled  successively  three  times 
with  70-86°  naphtha  and  the  oil  dissolved  off  the  surface  of  the  acid,  the  gaso- 
line solution  being  sucked  off  into  a  bottle  with  an  air  pump.  Care  is  taken  not 
to  suck  off  any  of  the  tarry  matter  formed.  The  acid  can  be  neutralized  with 
ammonia  and  the  tar  can  be  collected  on  a  tared  filter,  washed  with  gasoline 
that  leaves  no  residue  on  evaporation,  dried  at  a  low  temperature,  and  weighed 
as  gummy  matter.  As  shown  by  long  practical  experience,  the  oil  showing 
the  least  tar  or  gum  is  the  best  oil;  it  also  absorbs  the  least  oxygen. 

Carbon  Residue  Test.  Gray's  Method.  To  a  tared  1-oz.  quartz  flask  of  the 
dimensions  shown  in  Fig.  91,  add  25  cc.  of  the  oil  to  be  tested  and  weigh.  Wrap  the 
neck  of  the  flask  with  asbestos  paper  as  far 
down  as  the  side  arm.  Stopper  tightly 
with  a  good  cork.  Connect  to  a  small 
aerial  condenser  by  plugging  the  space  with 
asbestos  or  glass  wool.  Provide  a  shield 
which  will  protect  the  flame  and  the  flask 
up  to  the  side  tube.  Using  the  flame  of  a 
good  Bunsen  or  Tirrell  burner,  heat  the 
flask  so  that  the  first  drop  of  distillate  will 
come  over  in  approximately  five  minutes. 
Continue  the  distillation  at  such  a  rate 
that  1  drop  per  second  will  fall  from  the 
end  of  the  condenser.  As  the  end  of  the 
distillation  approaches,  increase  the  heat 
just  enough  so  that  no  heavy  vapors  are 


FIG.  91.— Gray's  Distillation  Flask. 


allowed  to  condense  and  drop  back  into  the  flask;  continue  increasing  the  heat 
until  the  flask  is  enveloped  in  the  flame,  and  hold  the  temperature  five  minutes. 
Allow  the  flask  to  cool,  remove  the  asbestos  covering  and  cork,  and  burn  out 
completely  the  carbon  and  oil  in  the  neck  as  far  down  as  the  side  tube,  and  in 
the  side  tube.  Heat  the  bottom  of  the  flask  until  no  more  vapors  are  given  off. 
Cool  and  weigh. 

Motor  oils,  of  light  and  medium  grade,  range  in  coke-like  residue  from 
0.06  to  0.5%,  the  percentage  offixed  carbon  being  roughly  proportional  to  the 
viscosity  of  the  oil.  That  is,  the  higher  the  viscosity,  the  higher  will  be 
the  percentage  of  fixed  carbon,  provided  the  oils  have  been  manufactured  from  the 
same  grade  of  crude  petroleum  by  the  same  general  methods.  The  heavy  and 
extra  heavy  motor  oils  range  from  0.5  to  1.25%.  As  the  percentage  of  fixed  car- 
bon varies  with  the  viscosities  of  the  oils,  the  viscosity  should  be  taken  into  con- 
sideration. For  illustration,  it  would  not  be  fair  to  compare  a  motor  oil  having  a 
viscosity  of  200  at  100°  F.,  Saybolt,  with  a  motor  oil  having  a  viscosity  of  400  at 
the  same  temperature.  The  carbon  residue  in  the  200  viscosity  oil  would  be  in 
the  neighborhood  of  0.2%,  where  as  the  fixed  carbon  of  the  higher  viscosity  oil 
would  be  in  the  neighborhood  of  0.75%. 

Gasoline  Test.  This  shows  the  presence  of  tar  (still  bottoms)  or  asphaltic 
matters. 

Mix  10  cc.  of  the  oil  with  90  cc.  86°-88°  gasoline  (from  Pennsylvania  crude) 
B.pt.  30°-50°  C.,  allow  to  stand  one  hour  at  70°  to  80°  F.;  not  more  than  10% 
Ji  flocculent  or  tarry  matter  should  have  settled  out.  This  settling  can  be 


580  FIXED   OILS,  FATS  AND   WAXES 

facilitated  by  whirling  in  a  centrifuge  in  a  graduated  tube  in  which  the  volume  of 
the  precipitate  can  be  read  off.  If  the  test  be  applied  to  the  oil  before  making 
the  flash  test  and  then  again  after  this  test  it  shows  the  extent  to  which  the 
oil  is  changed  upon  heating.  Other  things  being  equal  the  oil  which  is  changed 
the  least  is  the  best  oil.1 

Microscopical  Test.  Put  a  few  drops  of  the  well-mixed  oil  on  a  slide  and 
note  the  nature  of  the  suspended  matter — whether  carbonaceous  specks,  flakes 
of  paraffin  which  disappear  on  warming,  or  foreign  matter.  A  good  oil  should 
be  practically  free  from  all  these  bodies. 

Friction  Tests.  The  writer  is  inclined  to  doubt  if  friction  tests  are  worth 
the  outlay  for  a  machine  and  the  time  expended  in  their  execution.  With- 
out question  they  do  determine  the  relative  efficiency  as  regards  lubricating 
power  of  different  oils,  but  the  conditions  under  which  the  test  is  made  seldom 
occur  in  practice;  the  bearings  upon  which  the  oil  is  tested  are  as  nearly  perfect 
as  can  be  made,  and  the  feed  and  load  are  as  regular  as  is  possible;  in  other 
words,  the  conditions  are  ideal. 

The  lubricating  power  of  an  oil  is  so  closely  related  to  its  viscosity 2  that  the 
author  believes  that  results  of  more  practical  value  can  be  obtained  by  the 
determination  of  the  viscosity  of  the  oils,  and  subsequent  observation  of  their 
behavior  in  actual  use  than  by  the  longer  and  more  troublesome  friction  test. 
Recent  experiments,3  however,  have  shown  that  of  two  oils  of  the  same  viscosity 
and  other  constants  the  coefficient  of  friction  of  one  was  14%  less  than  the  other. 

In  case,  however,  it  be  desired  to  make  the  friction  test,  the  following  machines, 
it  is  believed,  will  be  found  to  be  most  satisfactory  for  the  purpose : 

For  spindle  oils  and  light  lubricating  oils,  the  machine  4  of  the  Thurston 
type  which  can  be  run  at  the  highest  speed  and  lowest  pressure. 

For  heavy  oils  and  railroad  work,  the  large  machine  of  the  Thurston  B  type, 
described  in  his  "  Friction  and  Lost  Work  in  Machinery  and  Millwork,"  page  254; 
also  in  Brannt,  page  486;  also  in  Archbutt  and  Deeley.6 

For  machines  using  a  flooded  bearing  the  Beauchamp-Tower  machine,  de- 
scribed in  the  "  Proceedings  of  the  Institution  of  Mechanical  Engineers  of  Great 
Britain,"  1883,  632;  1884,  29;  1885,  58;  1888,  173;  1891,  131;  also  in 
Archbutt  and  Deeley.7 1 

ANIMAL  AND  VEGETABLE  OILS 

The  tests  most  commonly  employed  for  the  identification  of  these  oils  are  as 
follows:  specific  gravity,  refractive  index,  Valenta  test,  elaidin  test,  Maumene" 
test,  iodine  number,  and  saponification  value. 

In  addition,  certain  special  and  commercial  tests  are  applied,  as  Bechi 
test,  Baudouin  test,  free  acid,  spontaneous  combustion,  and  drying  test. 

Specific  Gravity.  This  is  usually  determined  either  by  the  Westphal  balance 
(page  569)  or  by  the  picnometer. 

1  Conradson,  J.  Ind.  and  Eng.  Ch.,  2,  171,  1910. 

2  Brannt,  "  Petroleum  and  its  Products,"  p.  510;  Woodbury,  vide  infra.} 

3  Trans.  Am.  Soc.  Mech.  Eng.,  32,  834,  1910. 

4  Made  by  Olsen  or  Hiehl6  Bros.,  Philadelphia,  Pa. 
6  "  Lubrication  and  Lubricants,"  1907,  pp.  332-348. 

6  Ibid.,  p.  359. 

7  Ibid.,  p.  355. 


FIXED   OILS,    FATS   AND   WAXES 


581 


A  two-necked  flask  of  50  cc.  capacity,  having  a  thermometer  carefully  ground 
into  one  neck,  the  second  one  being  a  narrow  tube  bearing  the  mark,  is  most 
suitable.  This  is  filled  with  the  oil  to  be  examined,  cooled  to  15.5°  C.,1 
the  excess  "of  oil  removed  and  weighed.  If  the  weighings  be  made  to  0.5  milli- 
gram and  a  correction  applied  for  the  expansion  of  the  glass  by  the  differ- 
ence in  temperature  =15. 5—  4  =  11.5°  =  —0.025%  of  the  value  ^obtained,  the 
determination  is  accurate  to  0. 00002. 2 

For  the  determination  of  the  specific  gravity  of  small  quantities  of  oil, 
satisfactory  results  can  be  obtained  by  weighing  1  or  5  cc.  of  the  oil  carefully 
measured  from  an  accurately  calibrated  pipette.  Or  a  mixture  of  alcohol  and 
water  can  be  made  until  a  drop  of  oil  will  stay  in  any  position  in  it,  and  its  specific 
gravity  determined. 

Refractive  Index.  This  is  of  the  same  value  as  the  determination  of  specific 
gravity:  it  has,  however,  the  advantage  that  it  is  more  rapid  and  uses  only  one 
or  two  drops  of  the  oil. 

The  apparatus  preferably  employed  is  the  Abbe*  refractometer,  Fig.  92,  the 
prisms    of   which  are   kept    at    constant 
temperature,  usually  25°  C.,  by  circulat- 
ing water. 

The  illuminating  mirror  should  light 
the  cross  hairs  and  the  telescope  should 
be  sharply  focused  on  them. 

The  double  prism  is  opened  by  means 
of  the  screw  heads,  and  after  carefully 
cleansing  the  prisms  with  cotton  and 
ether,  a  drop  or  two  of  the  oil  placed 
on  the  horizontal  surface  of  the  fixed 
prism.  The  prisms  are  then  tightly  closed. 
The  telescope  is  brought  into  the  position 
shown  and  the  sector  is  firmly  held  and 
the  alidade  (the  moving  part)  moved  for- 
ward until  the  field  of  vision  shows  the 
boundary  between  light  and  shade  just 
intersecting  the  cross  hairs. 

By  means  of  the  screw  on  the  right 
of  the  instrument  this  boundary  line 
should  be  made  as  sharp  as  possible. 
The  index  of  refraction  is  read  off  directly 
from  the  sector,  using  a  lens  if  necessary; 
the  reading  is  accurate  to  .0002. 

After  using,  the  prisms  are  again  care- 
fully cleansed  and  a  piece  of  filter  paper  placed  between  them  to  prevent  them 
from  being  scratched.  The  instrument  is  in  correct  adjustment  when  water  at 
18°  gives  a  mean  reading  of  1.333.  The  temperature  correction  for  oils  and  fats 
is  0.0004  for  every  degree  rise. 

Valenta  Test.3    Although  considered  by  some  to  be  unreliable,  yet  as   the 

1  Allen  (Organic  Analysis,  33)  states  that  a  correction  of  0.00064  can  be  made  for 
each  variation  of  1°  C. 

2  Wright,  J.  Soc.  Chem.  Ind.,  11,  300,  1892. 

3  Valenta,  Dingier  polyt.  J.,  253,  418;  also  J.  Soc.  Chem.,  Ind.,  3,  643,  1884. 


FIG.  92.— Refractometer. 


582  FIXED   OILS,   FATS   AND   WAXES 

indication  given  by  this  test  may  be  of  value,  it  is  barely  worth  the  trouble  of 
execution.  It  depends  upon  the  solubility  of  the  oil  in  glacial  acetic  acid. 

Enough  oil  is  poured  into  a  test-tube  to  fill  it  to  the  depth  of  about  1  in., 
the  exact  height  being  marked  by  the  thumb;  an  equal  quantity  of  glacial  acetic 
acid  is  poured  in,  that  is,  until  the  acid  reaches  the  point  indicated  by  the  thumb. 
A  light  thermometer  is  placed  in  the  tube,  and  it  is  heated  until  the  oil  dissolves 
— shown  by  the  liquid  becoming  homogeneous.  The  tube  is  now  allowed  to  cool, 
and  the  point  noted  at  which  it  begins  to  become  thoroughly  turbid. 

Castor  oil  is  soluble  at  ordinary  temperatures,  while  rape-seed  and  other 
cruciferous  oils  are  usually  insoluble  even  at  the  boiling-point  of  the  acid.  The 
temperatures  at  which  other  oils  become  turbid  are  given  on  pages  604  and  605. 

Elaidin  Test.  Although  this  is  not  a  quantitative  test,  yet  its  ease  of  applica- 
tion and  the  conclusions  which  may  be  drawn  from  it  render  it  valuable.  It 
depends  upon  the  change  of  the  liquid  olein  into  its  solid  isomer  elaidin,  and  is 
especially  applicable  to  olive  and  lard  oils. 

Manipulation.  Five  grams  of  the  oil  are  weighed  1 — within  2  drops — into  a 
cordial  glass,  7  grams  of  nitric  acid,  specific  gravity  1.34,  are  then  weighed  into  it,1 
and  two  pieces  of  copper  wire  (0.6  to  1.0  gram)  added.  Place  the  glass  in  a  pan 
of  cold  water  at  about  12°  C.,  and  stir  with  a  short  glass  rod  about  20  to  30  turns, 
not  only  with  a  rotary  movement,  but  also  with  an  up-and-down  motion,  so  as 
to  mix  the  oil  and  the  evolved  gas  thoroughly.  When  the  wire  has  dissolved, 
add  a  second  piece  and  stir  as  before.  This  second  addition  should  furnish  gas 
enough  if  the  liquid  has  been  kept  cool  and  the  stirring  has  been  thorough. 

At  the  end  of  the  first  hour,  pure  lard  oil  will  usually  show  flakes  of  a  wax-like 
appearance,  and  upon  standing  without  disturbance  and  at  the  same  temperature 
for  another  hour,  the  oil  will  have  changed  to  a  solid  white  cake  hard  enough  to 
bear  several  ounces'  weight,  or  admit  of  lifting  the  glass  and  contents  by  the  glass 
rod. 

Most  of  the  fish  and  seed  oils  yield  a  pasty  or  buttery  mass  separating  from  a 
fluid  portion,  whereas  olive,  almond,  peanut,  lard,  sperm  and  sometimes  neat's- 
foot  oil,  yield  a  solid  cake. 

Instead  of  using  nitric  acid  and  copper,  sulphuric  acid  of  46°  Baume",  con- 
taining a  little  nitric  acid  and  saturated  at  0°  C.  with  nitric  oxide,  may  be  em- 
ployed. 

A  test  should  always  be  made  at  the  same  time  with  an  oil  of  undoubted  purity. 

NOTES.  If  the  oil  be  stirred  too  much  or  too  frequently,  or  is  too  warm,  it  has  no 
opportunity  to  form  a  hard  cake. 

Htibl  states  that  all  attempts  to  make  the  test  a  quantitative  one  have  resulted 
in  failure. 

Mercury  can  be  used  instead  of  copper. 

Cailletet's  method,2  in  which  a  smaller  quantity  of  oil  is  used,  and  sulphuric  and 
nitric  acids  allowed  to  act  upon  it  in  a  boiling  water  bath,  cannot,  in  the  experience 
of  the  writer,  be  depended  upon  to  give  reliable  results. 

Maumene  Test.3  While  this,  like  the  preceding,  is  not  a  quantitative  test, 
yet  the  indications  afforded  by  it  are  of  more  value  in  many  cases  than  those 
obtained  by  quantitative  methods,  as,  for  example,  the  saponification  value. 
It  depends  upon  the  heat  developed  by  the  mixing  of  the  oil  with  strong  sul- 

1  Not  on  the  analytical  balance. 

*  Milliau,  J.  Am.  Chem.  Soc.,  15,  156,  1893. 

3  SO2C1  gives  similar  results. 


FIXED   OILS,   FATS  AND  WAXES  583 

phuric  acid.    This  takes  place  in  a  small  beaker  7}  to  9  cm.  deep  and  of  150  cc. 
capacity,  packed  in  an  agate-ware  cup  with  dry  felt  or  cotton  waste  packing. 

Manipulation.  Fifty  grams  of  the  oil  are  weighed l  into  the  beaker  to  within 
2  drops,  and  its  temperature  noted  by  a  thermometer.  Ten  cc.  of  sulphuric 
acid  are  now  run  gradually  into  the  oil — allowing  the  graduate  to  drain  five  seconds 
— the  mixture  being  stirred  at  the  same  time,  and  the  stirring  continued  until 
no  further  increase  in  temperature  is  noted.  The  highest  point  at  which  the 
thermometer  remains  constant  for  any  appreciable  time  is  observed,  and  the 
difference  between  this  and  the  initial  temperature  is  the  urise  of  tempera- 
ture." This  varies  with  the  strength  of  the  acid  employed,  and  to  secure  uni- 
formity 2  the  results  should  be  expressed  by  dividing  the  rise  of  temperature  with 
the  oil  by  the  rise  of  temperature  with  water,  and  multiplying  by  one  hundred. 
This  is  called  the  "  specific  temperature  reaction."  The  rise  of  temperature 
with  water  is  determined  in  the  same  manner  as  with  oil,  using  the  same  vessel. 

NOTES.  In  performing  this  test  it  is  important  that  the  oil  and  acid  be  of  the 
same  temperature,  attained  by  keeping  them  beside  each  other. 

The  strength  of  acid  should  be  as  far  as  possible  the  same;  it  should  be  deter- 
mined not  by  specific  gravity,  but  by  titration,  as  100%  and  94.3%  acid  have  the 
same  specific  gravity. 

For  concordant  results  the  conditions  should  be  the  same,  and  the  same  apparatus 
should  be  used.  In  case  the  test  is  to  be  applied  to  a  drying  oil,  it  should  be  diluted 
one-half  with  a  mineral  oil,  25°  paraffin,  for  example,  thoroughly  mixing  them.  The 
"rise  of  temperature"  is  then,  the  rise  of  temperature  of  mixture  minus  half  the  rise 
of  temperature  of  50  grams  of  mineral  oil,  multiplied  by  2. 

It  is  advisable  to  make  a  test  at  the  same  time  with  an  oil  of  known  purity.  Re- 
sults should  agree  within  2%.  By  the  use  of  the  Hub!  formula,  page  586,  substituting 
thermal  values,  results  comparable  with  those  obtained  with  the  iodine  value  can 
be  obtained. 

Sherman,  Danziger,  and  Kohnstamm  3  have  studied  this  method  with  the  idea 
of  eliminating  the  errors.  Rather  than  dilute  the  oil  with  a  mineral  oil  they  dilute 
the  acid,  using  one  of  89%.  The  results  obtained  are  a  little  lower  for  vegetable 
oils  and  a  little  higher  for  animal  oils  than  those  usually  found  with  the  strong  acid 
as  employed  by  Thomson  and  Ballantyne.  Mitchell 4  uses  an  inert  diluent — car- 
bon tetrachloride — in  a  vacuum-jacketed  tube  and  one-fifth  the  quantities;  all  oils 
are  diluted.  He  finds  that  the  results  obtained  are  in  close  agreement  with  the 
bromine  thermal  values;  further,  that  the  test  may  be  of  use  in  determining  the 
degree  of  oxidation  of  fats  and  oils,  the  figures  becoming  greater  with  the  age  of 
the  oil. 

Data  upon  various  oils  will  be  found  on  pages  603-605. 

References. 

Maumene,  Compt.-Rend.,  35,  572,  1852. 

Ellis,  J.  Soc.  Chem.  Ind.,  5,  361,  1886. 

Thomson  and  Ballantyne,  J.  Soc.  Chem.  Ind.,  10,  234,  1891. 

Richmond,  Analyst,  20,  58,  1895. 

Munroe,  Am.  Pub.  Health  Ass'n,  10,  236,  1884. 

Iodine  Number  or  Value.  This  is  the  percentage  of  iodine  absorbed  by  an 
oil;  the  method  depends  upon  the  fact  that  different  oils  absorb  different  amounts 
of  the  halogens;  the  process  is  mainly  one  of  addition,  although  small  quantities 

1  Not  on  the  analytical  balance. 

2  Tortelli,  J.  Soc.  Chem.  Ind.,  23,  668,  1904,  is  unable  to  secure  uniformity  in  thia 
way. 

3  J.  Am.  Chem.  Soc.,  24,  266,  1902. 

4  Analyst,  26,  169,  1901. 


584  FIXED   OILS,    FATS   AND  WAXES 

of  substitution  products  are  formed.  For  example,  the  unsaturated  body  olein, 
(Ci7H33COO)3C3H5,  when  brought  in  contact  with  iodine  takes  up  6  atoms  and 
forms  the  addition  product,  di-iodo  stearin,  (CnHgnLCOCOaCsHs.  Palmitin, 
(CisHsiCOO^CsEU,  when  similarly  treated,  forms  no  addition  product,  but  a  small 
quantity  of  the  substitution  product,  iodo-palmitin,  (CnHsoICOO^CoHs,  and 
the  hydrogen  displaced  unites  with  the  iodine  to  form  hydriodic  acid.  The 
Quantity  of  hydriodic  acid  thus  formed  is  a  measure  of  the  amount  of  substitution.1 

1.  Hanus's  Method.  Manipulation.  From  0.12  to  0.15  gram  of  a  drying 
oil,  0.2  to  0.3  gram  of  a  non-drying  oil,  or  0.6  to  0.7  gram  of  a  solid  fat,  is  accu- 
rately weighed  into  a  dry  200-cc.  bottle.  This  should  be  of  colorless  glass  and  be 
provided  with  a  well-ground  stopper.  This  is  best  effected  by  pouring  out  about 
5  grams  of  the  oil  into  a  No.  1  beaker  containing  a  short  stirring  rod,  and  setting 
it  into  a  watch-glass  upon  the  pan  of  the  analytical  balance.  The  whole  system 
is  weighed,  the  beaker  removed,  and  several  drops  of  oil  transferred  to  the  bottle 
by  dropping  down  the  rod,  being  careful  that  no  oil  touches  the  neck.  Eight 
drops  are  approximately  0.2  gram.  The  beaker  is  replaced  in  the  watch-glass 
and  the  system  again  weighed,  the  difference  in  weight  being  the  amount  of  oil 
in  the  bottle. 

The  oil  is  dissolved  in  10  cc.  of  chloroform,  30  cc.  of  the  iodine  solution 
(Reagents)  added — best  from  a  burette — and  allowed  to  stand  with  occasional 
shaking  for  exactly  fifteen  minutes;  with  oils  of  an  iodine  number  of  less  than 
100,  ten  minutes  suffices;  15  cc.  of  potassium  iodide  solution  2  are  added  and  the 
solution  titrated,  with  or  without  the  addition  of  starch,  with  sodium  thiosul- 
phate  until  the  halogen  disappears. 

At  the  same  time  at  which  the  oil  is  prepared,  two  "  blanks  "  should  be  pre- 
pared similarly  in  every  way  to  the  actual  tests,  except  in  the  addition  of  the  oil, 
and  treated  in  every  respect  like  them;  the  strength  of  the  thiosulphate  solution 
should  also  be  determined  the  same  day  on  which  this  test  is  carried  out. 

Standardization  of  the  Thiosulphate  Solution.  Ten  cc.  of  potassium  iodide 
and  100  cc.  of  water  are  poured  into  the  Erlenmeyer  flask;  20  cc.  of  the  bichromate 
solution,  equivalent  to  0.2  gram  of  iodine,  are  now  measured  in  with  a  pipette, 
and  to  this  5  cc.  of  strong  hydrochloric  acid  added  and  the  mixture  shaken  for 
three  minutes.  It  is  now  titrated  with  the  thiosulphate  solution  until  the  yellow 
color  of  the  iodine  has  almost  disappeared;  starch  paste  is  now  added,  and  the 
titration  continued  until  the  deep-blue  color  of  the  solution  changes  to  a  sea- 
green — due  to  CrCl3, — which  is  usually  brought  about  by  the  addition  of  a  single 
drop. 

The  reactions  involved  are : 

K2Cr207+14HCl  =2CrCl,+2KCl+7HI0-f-3Cla; 

3Cl2+6KI=6KCl-f3I2; 
6Na2S203+ 31,  =3Na2S406+6NaI. 

NOTES.  Wijs  J  uses  iodine  chloride  instead  of  bromide;  it  is  more  troublesome 
to  prepare  and  gives  results  about  1.2  points  higher.4  Either  of  these  methods  has 
the  advantage  over  Hubl's — first,  that  the  solutions  keep  better,  remaining  practically 

1  Mcllhiney,  J.  Am.  Chem.  Soc.,  16,  275,  1894. 

*  This  is  the  original  method.  Tolman  adds  here  100  cc.  water  as  in  the  Hiibl 
method. 

»  Berichte,  31,  752,  1898. 

4  Tolman  and  Munson,  J.  Am.  Chem.  Soc.,  25,  244,  1903. 


FIXED   OILS,  FATS  AND  WAXES  583 

unchanged  for  several  months;   secondly,  that  the  action  is  about  sixteen  times  as 
rapid,  it  being  completed  in  fifteen  minutes;  thirdly,  that  the  solutions  are  cheaper. 

Acetic  acid  cannot  be  displaced  by  carbon  tetrachloride  as  a  solvent,  as  the  last 
traces  of  iodine  are  difficult  to  remove  from  it.  The  acetic  acid  used  should  be  at 
least  99.5%  and  show  no  reduction  with  potassium  bichromate  and  sulphuric  acid. 

2.  H'iibl's  Method.  Manipulation.  The  oil  is  weighed  out  as  in  1,  into 
300-cc.  bottles,  except  that  about  25%  more  may  be  used. 

The  oil  is  now  dissolved  in  10  cc.  of  chloroform,  30  cc.  of  iodine  and  mercuric 
chloride  solution  added,  the  bottle  placed  in  a  dark  closet,  and  allowed  to  stand, 
with  occasional  gentle  shaking,  for  four  hours.  If  the  solution  becomes  nearly 
decolorized  after  two  hours,  an  additional  quantity  should  be  added.  One 
hundred  cc.  of  distilled  water  and  20  cc.  of  potassium  iodide  are  added  to  the 
contents,  and  the  excess  of  iodine  titrated  with  sodium  thiosulphate.  If  at  this 
point  a  red  precipitate  (HgI2)  is  formed,  more  potassium  iodide  should  be  added. 
As  the  chloroform  dissolves  some  of  the  iodine,  the  titration  can  proceed  until 
the  chloroform  layer  is  nearly  colorless,  then  the  starch  solution  is  added,  and 
the  operation  continued  to  the  disappearance  of  the  blue  color. 

"  Blanks  "  should  be  titrated  as  with  the  foregoing  process,  page  584. 

NOTES.  The  method  was  proposed  by  Cailletet  in  1857,  made  use  of  by  Mills 
and  Snodgrass  1  in  1883,  using,  however,  bromine  and  carbon  bisulphide,  and  de- 
scribed in  almost  its  present  form  by  Hlibl.2  The  chief  factors  in  its  execution  are 
(1)  strength  of  the  iodine  solution;  (2)  the  quantity  used;  and  (3)  the  length  of  its 
time  of  action. 

1.  The  Strength  of  Iodine  Solution.  ^   According  to  HiibFs  original  memoir,  the  solu- 
tions can  be  kept  indefinitely  when  mixed. 

Fahrion  3  states  that  the  solution  deteriorated  as  much  as  from  17  to  23%  in 
eight  days.  Ballantyne  4  confirms  the  deterioration,  but  finds  it  much  less,  5  to  8% 
in  thirty-eight  days.  This  weakening  of  the  solution  is  probably  due  to  the  hydriodic 
acid  formed  by  the  action  of  the  iodine  upon  the  alcohol.6 

The  mercuric  chloride  acts  apparently  as  a  carrier  of  iodine,  as  the  reaction  takes 
place  very  slowly  without  it.  (Gantter.)  6  Waller  7  finds  that  the  addition  of  50 
cc.  HC1,  specific  gravity,  1.19,  to  the  mixed  iodine  solution  preserves  it  for  months. 
Of  the  other  metallic  chlorides,  CoCl2  gives  the  highest  true  iodine  value,  MnCl2, 
MnBrz  and  NiCl2  cause  practically  no  addition.  (Schweitzer  and  Lungwitz.)  8 

2.  The  Quantity  of  Iodine  Solution   Used.     The  mixed  iodine  solution  as  made 
up  should  require  about  53  cc.  of  the  thiosulphate.     Before  using,  a  rough  titra- 
tion should  be  made,  and  if  it  be  much  weaker  than  this,  a  proportionately  larger 
amount  added.     The  action  of  a  large  excess  of  iodine  is  to  increase  the  substitu- 
tion rather  than  addition;    increase  in  temperature  or  in  time  produces  the  same 
effect.9 

The  excess  of  iodine  recommended  is  from  150  to  250%;  some  observers  recom- 
mend from  400  10  to  600%. n 

3.  Length  of  Time.     Two  hours  is  sufficient  for  olive  oil,  tallow,  and  lard,  while 
for  linseed  oil,  balsams,  and  resins  twenty-four  hours  should  be  allowed.12 

1 J.  Soc.  Chem.  Ind.,  2,  435,  1883. 

2  Dingier  polyt.  J.,  253,  281;  also  J.  Soc.  Chem.  Ind.,  3,  641,  1884. 

8  J.  Chem.  Ind.,  11,  183,  abstr.,  1892. 

4  Ibid.,  13,  1100,  abstr.,  1894. 

5  J.  Soc.  Chem.  Ind.,  14,  130,  1895. 

6  Ibid.,  12,  717,  abstr.,  1893. 

7  Chem.  Ztg.,  19,  1786,  1831,  1895. 

8  J.  Soc.  Chem.  Ind.,  14,  1031,  1895. 

9  J.  Soc.  Chem.  Ind.,  12,  717,  abstr.,  1893. 

10  Ibid.,  14,  1031,  1895. 

11  Holde,  Mitt.  kgl.  Techn.  Versuchs.,  9,  81,  1891. 

12  Dieterich,  J.  Soc.  Chem.  Ind.,  12,  381,  1893. 


586  FIXED   OILS,   FATS   AND   WAXES 

Ingle l  has  shown  that  the  free  acid  formed  during  the  process  is  due  to  the 
action  of  water  upon  the  iodochlorides.  Some  of  these  are  reduced  by  potassium 
iodide  with  liberation  of  iodine  and  consequent  reduction  in  the  iodine  absorption. 
Iodine  chloride  is  the  active  agent,  and  not  hypoiodous  acid. 

For  the  calculation  of  the  percentage  of  adulteration  of  one  oil  by  another, 
Hubl  gives  the  following  formula:2 

"Let  x=  percentage  of  one  oil  and  y=  percentage  of  the  other  oil,  further, 
m  =  iodine  value  of  pure  oil  x,  n  of  pure  oil  y,  and  /  of  the  sample  under  examina- 
tion, then 

100(7  -n)" 
m — n 

He  further  states  that  the  age  of  the  oil,  provided  it  be  not  rancid  or  thick- 
ened, is  without  influence  on  the  iodine  value.  Ballantyne 3  finds  that  light  and 
air  diminish  the  iodine  number. 

As  might  be  expected,  the  iodine  value  is  inversely  proportional  to  the  cold  test. 

The  method,  as  will  be  seen,  is  a  conventional  one,  and  the  best  results  will 
be  obtained  by  using  measured  quantities  of  reagents  and  carrying  through  the 
process  in  the  same  manner  every  time.4 

The  calculation  is  perhaps  most  easily  made  as  follows:  Subtract  the  number 
of  cc.  of  thiosulphate  used  for  the  titration  of  the  oil,  from  that  obtained  by 
titrating  the  blank — this  gives  the  thiosulphate  equivalent  to  the  iodine  absorbed 
by  the  oil.  Multiply  this  number  (of  cc.)  by  the  value  of  the  thiosulphate  in 
terms  of  iodine,  and  the  result  is  the  number  of  grams  of  iodine  absorbed  by  the 
oil;  this  divided  by  the  weight  of  oil  used  and  multiplied  by  100  gives  the  iodine 
number. 

In  case  it  be  desired  to  recover  the  iodine  used,  reference  may  be  had  to  an 
article  by  Dieterich,  abstracted  in  the  Jour.  Soc.  Chem.  Ind.,  15,  680,  1896. 

Oxidized  Oils.  Iodine  Number  of.  To  find  the  original  iodine  number  of  a 
semi-drying  or  non-drying  oil  which  has  been  altered  by  atmospheric  oxidation, 
add  0.8  to  the  iodine  number  found  on  the  altered  sample  for  each  increase  of 

(15  5°  C  \5 
taken  at  -  '        ' ) . 
15.5   U./ 

Bromine  Number  or  Value.  The  iodine  method  just  described  has,  among 
others,  the  disadvantage  that  it  fails  to  distinguish  between  addition  and  substi- 
tution; this  is  sometimes  of  importance,  and  to  accomplish  it  Mcllhiney  6  makes 
use  of  the  bromine  absorption. 

Manipulation.  From  0.2  to  0.3  gram  of  a  drying  oil,  0.4  to  0.5  of  a  non- 
drying  oil,  or  1.0  to  1.2  grams  of  a  solid  fat,  are  accurately  weighed  into  the  300 
cc.  bottle,  as  in  the  iodine  number  (page  584). 

The  oil  is  dissolved  in  10  cc.  of  carbon  tetrachloride,  and  20  cc.  of  bromine 
solution  (Reagents)  added,  best  from  a  burette.  After  allowing  it  to  stand  two 
minutes  by  the  watch,  20  or  30  cc.  of  potassium  iodide  are  added,  in  the  manner 

1  J.  Soc.  Chem.  Ind.,  21,  587,  1902. 

2  Dingier  polyt.  J.,  253,  281,  1884. 

3  J.  Soc.  Chem.  Ind.,  10,  31,  1891. 

4  If,  for  example,  the  water  be  added  before  the  iodide  solution,  the  iodine  number 
is  changed  by  0.3  per  cent. 

6  Sherman  and  Falk.,  J.  Am.  Chem.  Soc.,  27,  608,  1895. 
•  J.  Am.  Chem.  Soc.,  21,  1084,  1899. 


FIXED   OILS,   FATS   AND   WAXES  587 

described  below,  the  amount  depending  upon  the  excess  of  bromine.  To  pre- 
vent loss  of  bromine  and  hydrobromic  acid,  a  short  piece  of  thin  and  wide  rubber 
tubing — "  bill  tie  tubing  " — is  slipped  over  the  lip  of  the  bottle,  thus  forming  a 
well  around  the  stopper;  some  of  the  iodide  solution  is  poured  into  this  and  the 
bottle  cooled  in  cracked  ice.  Upon  removing  the  stopper  the  solution  is  sucked 
into  the  bottle,  it  is  shaken  to  insure  the  solution  of  the  vapors,  and  the  remainder 
of  the  reagent  added.  The  iodine  liberated  is  titrated  by  sodium  thiosulphate 
in  the  usual  way. 

When  this  titration  is  finished,  5  cc.  of  the  potassium  iodate  solution  are  added 
and  the  titration  repeated.  The  iodine  liberated  in  this  reaction  is  equivalent  to 
the  hydrobromic  acid  present.  Blank  determinations  should  be  made  with  the 
reagents  used,  as  with  the  iodine  number. 

NOTES.  Oftentimes,  particularly  with  resins,  emulsification  of  the  solution  takes 
place,  masking  the  end-point.  This  can  be  prevented  by  the  addition  of  50  or  100 
cc.  of  a  10%  solution  of  salt. 

In  case  ice  be  not  at  hand,  the  vapors  will  probably  be  completely  absorbed  by 
passing  through  the  iodine  solution  in  the  rubber  well. 

The  reactions  involved,  in  addition  to  those  on  page  584  are: 

Palmitin 

(C15H3:COO)5C3H5+3Br2  =  (C^HsoBrCOO^CaHs+SHBr. 
3HBr+3KI  =  3KBr+3HI. 
6HI+KIO3  =3I2+3H2O+KI. 

The  calculation  is  similar  to  that  followed  in  the  iodine  number  (page  584). 

The  percentage  of  bromine  found  as  hydrobromic  acid  is  called  the  bromine  sub- 
stitution figure,  and  the  total  percentage  absorbed,  less  twice  the  bromine  substitu- 
tion figure,  gives  the  bromine  addition  figure. 

The  method  has  the  further  advantages  that  it  is  rapid,  the  bromine  solution  is 
permanent  and  inexpensive.  For  data  upon  various  oils,  see  table  on  page  604. 

Saponification  Value.  This  is  expressed  by  the  number  of  milligrams  of 
potassium  hydrate  necessary  to  saponify  one  gram  of  the  oil.  It  is  called  from 
the  originator  "  Koettstorfer  1  number  or  value/'  also  "  Saponification  number," 
and  must  not  be  confounded  with  "  Saponification  equivalent "  as  proposed 
by  Allen,2  which  is  the  number  of  grams  of  oil  saponified  by  56.1  grams  of  potassium 
hydrate. 

Manipulation.  One  to  2  grams  of  the  oil  are  weighed  out  into  a  200-cc.  Erlen- 
meyer  flask  (as  in  the  iodine  value,  q.  v.,  page  584)  and  saponified  by  25  cc.  N/2 
alcoholic  potash  accurately  measured  from  a  burette,  by  heating  upon  a  water 
bath,  a  1-in.  funnel  being  inserted  in  the  flask. 

When  the  Saponification  is  complete,  shown  by  the  homogeneity  of  the  solution, 
a  few  drops  of  phenolphthalein  are  added  and  the  excess  of  alkali  titrated  with 
N/2  hydrochloric  acid.  Two  blank  determinations  of  the  strength  of  the  N/2 
potassium  hydrate  must  be  made  simultaneously,  by  heating  25  cc.  under  the  same 
conditions  as  when  mixed  with  the  oil  and  for  the  same  length  of  time. 

NOTES.  Many  prefer  to  cork  the  flasks  tightly  and  tie  down  the  stoppers,  thus 
saponifying  under  pressure;  others  make  use  of  a  return  flow  condenser,  oftentimes 
merely  a  long  glass  tube. 

Smetham  3  adds  20  cc.  of  ether  and  finds  that  it  aids  Saponification.     Henriques  4 

1  Z.  anal.  Chem.,  18,  199,  1879. 

2  Commercial  Organic  Analysis,  2,  40. 
8  Analyst,  18,  193,  1893. 

4  Z.  angew.  Chemie,  721,  1895. 


588  FIXED   OILS,  FATS   AND  WAXES 

uses  3  to  4  grams  of  oil,  25  cc.  of  petroleum  ether,  and  25  cc.  of  normal  alcoholic  potash, 
saponifying  in  the  cold  by  allowing  to  stand  overnight;  the  advantage  consists  in 
preventing  the  change  in  the  solution  by  boiling. 

Mcllhiney  l  has  applied  the  process  to  dark-colored  substances  by  making  use 
of  the  principle  that  when  ammonium  chloride  is  added  to  a  neutral  soap  solution, 
and  the  mixture  distilled,  the  amount  of  ammonia  freed  is  equivalent  to  the  quantity 
of  alkali  combined  with  the  fatty  acids.  As  a  description  of  the  process  is  beyond 
the  scope  of  the  present  volume,  reference  must  be  had  to  the  original  article. 

As  ordinarily  ^  prepared,  the  alcoholic  potash  solution  turns  rapidly  reddish- 
brown,  so  that  it  is  very  difficult  to  note  the  end-point.  This  trouble  can  be  partially 
avoided  by  adding  a  drop  or  two  of  the  solution  ^to  the  diluted  indicator  contained 
upon  a  tile  after  the  manner  of  the  titration  of  iron  by  bichromate.  As  the  color 
IB  probably  due  to  the  polymerization  of  the  aldehyde  formed  by  the  oxidation  of 
the  alcohol,  it  is  more  satisfactory  to  use  for  the  preparation  of  the  potash  solution 
an  alcohol  which  is  practically  aldehyde  free.  This  is  best  made,  according  to  Dun- 
lap,2  as  follows:  1£  grams  of  silver  nitrate  are  dissolved  in  3  cc.  of  water,  added  to 
1  liter  of  alcohol  and  thoroughly  shaken;  3  grams  of  potassium  hydrate  are  dissolved 
in  15  cc.  of  warm  alcohol  and,  after  cooling,  added  to  the  alcoholic  silver  nitrate  and 
thoroughly  shaken  again,  best  in  a  tall  bottle  or  cylinder.  The  silver  oxide  is  allowed  to 
settle,  the  clear  liquid  siphoned  off  and  distilled.  Alcoholic  potash  made  up  from  this, 
using  the  so-called  "potash  by  alcohol,"  will  give  a  solution  which  will  remain  water- 
white  for  weeks. 

The  writer  has  found,  if  the  stock  solution  be  kept  under  an  atmosphere  of 
hydrogen,  that  the  coloration  by  standing  is  almost  entirely  prevented. 

Detection  of  Unsaponifiable  Oils.  The  qualitative  detection  takes  place  by 
observing  the  behavior  of  the  solution  obtained  by  boiling  the  oil  with  alcoholic 
potash  when  diluted  with  warm  water.  Any  unsaponifiable  material  will  mani- 
fest itself  as  oily  drops  in  the  clear  alcoholic  solution,  or  as  a  whitish  cloud  on  the 
addition  of  water. 

The  quantitative  determination  may  take  place  in  two  ways:  1.  From  the 
saponification  number.  2.  By  gravimetric  methods. 

1.  From  the  Saponification  Number.     On  pages  604  and  605  it  will  be 
noticed  that,  except  for  castor,  rape,  and  sperm  oils,  the  saponification  number 
averages  193.    If  the  number  found  be  divided  by  this  figure,  the  percentage  of 
saponifiable  matter  will  be  obtained;  this  subtracted  from  100  will  give  the  unsa- 
ponifiable matter.    This  method  gives  no  idea  of  the  kind  of  saponifiable  matter. 

2.  By  Gravimetric  Methods.    The  procedure  is  essentially  that  of  Spitz  and 
Honig  :3  10  grams  of  the  oil  are  boiled  fifteen  minutes  under  a  return-flow  condenser 
with  50  cc.  of  5%  alcoholic  potash;4  40  cc.  of  water  are  added  and  the  boiling 
repeated.     The  liquid  is  allowed  to  cool,  washed  into  a  separatory  funnel  with  50% 
alcohol  and  50  cc.  of  86°  gasoline,  thoroughly  shaken  and  allowed  to  stand.    The 
gasoline  layer  should  separate  clearly  and  quickly  from  the  soap  solution  and 
the  latter  is  drawn  off;  the  gasoline  is  washed  2  or  3  times  with  50%  alcohol  to 
extract  any  soap,  and  these  washings  added  to  the  soap  solution.    This  latter  is 
extracted,  until  upon  evaporation  the  gasoline  leaves  no  stain  upon  paper,  care 
being  taken  to  wash  the  gasoline  extracts  each  time  with  50%   alcohol;   three 
extractions  with  gasoline  are  usually  sufficient. 

The  gasoline  is  distilled  from  these  extracts,  the  residue  heated  until  the  gas- 

1 J.  Am.  Chem.  Soc.,  1G,  409,  1894.  For  a  discussion  of  the  theory  of  the  process, 
see  Lewkowitsch,  J.  Soc.  Chem.  Ind.,  17,  1107,  1898. 

1  J.  Am.  Chem.  Soc.,  28,  397,  1906. 

>  Z.  ang.  Chem.,  19,  565,  1891. 

4  The  potash  is  made  by  dissolving  purified  potash  in  the  smallest  possible  quan- 
tity of  water  and  adding  absolute  alcohol. 


FIXED  OILS,  FATS  AND  WAXES  589 

oline  odor  disappears,  and  weighed.  From  the  appearance  of  the  residue  some 
idea  of  the  kind  of  unsaponifiable  matter  can  be  obtained.  This  in  the  case  of 
sperm  oil, will  be  mainly  solid  alcohols,  probably  of  the  ethylene  series. 

According  to  Schicht  and  Halpern  1  this  method  is  open  to  the  following  errors: 
incomplete  saponification,  incomplete  extraction,  solubility  of  soaps  in  the  solv- 
ent, and  the  solubility  of  the  Untsaponifiable  matter  in  the  washing  solution.  Their 
improved  method  is  as  follows:  5  grams  of  fat 2  with  3  of  grams  solid  caustic  pot- 
ash dissolved  in  a  little  water  and  25  cc.  of  absolute  alcohol  are  boiled  half  an  hour 
under  a  reflux  condenser.  After  cooling  25  cc.  of  10%  KC1  are  added  and  the  solu- 
tion is  then  shaken  four  times  with  200  cc.  of  petroleum  ether  distilling  under  60°. 
The  petroleum  ether  is  evaporated  and,  without  washing,  the  residue  is  dissolved 
in  25  cc.  absolute  alcohol  and  the  solution  made  slightly  alkaline  with  normal 
alkali;  25  cc.  of  10%  KC1  are  added  and  the  shaking  with  petroleum  ether  repeated. 
The  petroleum  ether  solution  is  shaken  with  100  cc.  of  50%  alcohol  and  the  wash 
solution  with  100  cc.  petroleum  of  ether,  which  is  afterwards  washed  with  100  cc. 
of  50%  alcohol.  After  combining  the  extracts  the  petroleum  ether  is  driven  off 
and  the  residue  dried  and  weighed. 

NOTE.  Care  should  be  taken  to  use  gasoline  which  leaves  no  residue  on  evap- 
oration at  100°  C. 

Identification  of  the  Unsaponifiable  Matter.  The  unsaponifiable  matter  is 
either  liquid  or  solid;  in  case  it  is  liquid,  it  may  be  (1)  hydrocarbon  oils,  either 
mineral,  or  formed  by  the  distillation  of  waste  fats,  as  wool  grease,  or  (2)  tar 
oils,  "  dead  oils,"  etc.,  obtained  by  the  distillation  of  coal  tar;  or  (3)  rosin  oils. 

If  it  be  a  question  of  one  of  these  three,  the  specific  gravity  will  usually  decide 
it;  that  of  the  hydrocarbon  oils  is  0.855  to  0.930,  of  the  rosin  oils  0.96  to  0.99, 
while  the  tar  oils  are  heavier  than  water.  Rosin  oils  would  be  shown  by  the  Lie- 
bermann-Storch  test,  page  595;  a  mixture  of  mineral  and  tar  oils  would  be  iden- 
tified by  treatment  with  an  equal  quantity  of  nitric  acid,  sp.gr.  1.45,  both  pre- 
viously cooled  to  15°  C.,  and  noting  the  rise  of  temperature.  Mineral  oils  give 
a  very  slight  rise,  being  paraffins,  while  the  tar  oils  belong  to  the  benzole  series 
and  are  more  easily  nitrated.  Hydrocarbon  oils  from  distilled  grease  oleins  can 
be  identified  by  their  refractive  index  and  rotatory  power.3 

Solid  unsaponifiable  matters  may  be: 

(4)  Paraffin. 

(5)  Ceresene — refined  ozokerite. 

(6)  Higher  alcohols  of  the  paraffin  series,  as  cetyl,  Ci6H33OH,  coming  from  the 
saponification  of  sperm  oil  and  other  waxes. 

(7)  Cholesterol,  C26H430H,  and  its   isomers,   phytosterol,  sitosterol,    isocho 
lesterol,  etc. 

(8)  Lactones,  internal  anhydrides  of  oxy  acids  as  stearlactone, 

CuH29CHOHCH2CH2COOH=Ci4H29CHCH2CH2COO+H2O. 

I 1 

These  may  be  separated  by  boiling  for  two  hours  with  an  equal  quantity  of  acetic 

1  Chem.  Ztg.,  31,  279,  1907. 

2  For  linseed  and  other  oils,  ten  or  twenty  times  this  weight  should  be  used,  the 
alkali  being  correspondingly  increased. 

3  Gill  and  Forrest,  J.  Am.  Chem.  Soc,  32,  1071;  Gill  and  Mason,  J.  Am.  Chem.  Soc., 


590  FIXED   OILS,   FATS   AND  WAXES 

anhydride;  if  the  substance  dissolves  and  does  not  precipitate  on  cooling,  higher 
alcohols  are  indicated;  if  a  mass  of  crystals  separates  out  on  cooling,  cholesterol 
and  its  isomers,  or  a  mixture  of  these  with  the  higher  alcohols  is  indicated;  if  an 
oily  layer  remains  on  top,  it  is  an  indication  of  the  presence  of  paraffin  or  cere- 
sene.  For  the  complete  separation  and  identification  of  these  reference  must  be 
had  to  Lewkowitsch,  "  Analysis  of  Fats,  Oils,  and  Waxes,"  as  it  is  beyond  the  limits 
of  this  chapter. 

Test  for  Animal  or  Vegetable  Oils.  Animal  oils  contain  cholesterol,  C25H43OH, 
while  vegetable  oils  contain  the  isomeric  body  phytosterol;  hence  the  isolation 
and  identification  of  these  compounds  enables  one  to  say  with  certainty  as  to  the 
presence  of  one  class  of  oil  or  the  other — for  example  as  to  the  presence  of  fish  oil 
in  linseed.  The  quantity  of  these  bodies  varies  from  0.2  to  1%.  The  method 
is  essentially  that  of  Bomer.1  Fifty  grams  of  the  oil  are  boiled  in  a  flask  with 
a  return  cooler  with  75  cc.  of  95%  alcohol  for  five  minutes  and  the  alcoholic  solu- 
tion separated;  this  is  repeated  with  another  portion  of  alcohol.  The  alcoholic 
solutions  are  mixed  with  15  cc.  of  30%  sodium  hydroxide  and  evaporated  on  a 
water  bath  nearly  to  dryness  in  a  porcelain  dish  and  the  residue  shaken  out  with 
ether.  The  ether  is  evaporated,  the  residue  taken  up  with  a  little  ether,  filtered, 
again  evaporated,  dissolved  in  95%  alcohol  (by  volume),  and  allowed  to  crys- 
tallize slowly.  Bomer  states  that  the  form  of  the  crystals  is  more  to  be  relied 
upon  than  a  determination  of  their  melting-point.  Cholesterol  crystallizes  from 
alcohol  or  ether  in  leaflets  or  rhomboid  tables  containing  one  molecule  of  water 
of  crystallization.  Phytosterol  crystallizes  also  from  alcohol  with  one  molecule 
of  water  in  needles  forming  stars  or  bundles.  As  a  further  means  of  identification, 
some  of  the  esters  should  be  made  and  their  melting-points  determined. 

To  this  end  the  crystals  above  obtained  are  heated  over  a  low  flame  in  a  small 
porcelain  dish  covered  with  a  watch-glass,  with  2  or  3  cc.  of  acetic  or  other  acid 
anhydride  until  it  boils:  the  watch-glass  is  removed  and  the  excess  of  anhydride 
evaporated  on  the  water  bath.  The  contents  of  the  dish  are  treated  with  a  small 
quantity  of  absolute  alcohol  to  prevent  crystallization,  more  alcohol  added  and 
the  solution  allowed  to  crystallize.  The  crystals  are  filtered  off  through  a 
very  small  filter,  washed  with  a  small  quantity  of  95%  alcohol,  dissolved  in  abso- 
lute alcohol,  and  recrystallized  until  a  constant  melting-point  is  obtained. 

The  following  table  shows  the  corrected  melting-points  of  these  alcohols  and 
their  esters : 

Cholesterol.  Phytosterol. 

Alcohol 148-150.8°  136-143.8° 

Acetate 113-114°  120-137° 

Benzoate 135-151 >  142-148° 

Propionate 97-98°  104-105° 

NOTES.  Some  directions  state,  in  isolating  the  cholesterol  or  phytosterol,  to 
boil  with  the  30%  sodium  hydroxide  until  one-fourth  of  the  alcohol  is  evaporated. 
As  a  result  of  repeated  experiments  this  has  been  found  to  cut  down  the  yield  so 
much  that  on  a  large  scale  practically  none  of  these  bodies,  particularly  phytosterol, 
was  obtained.  This  agrees  with  the  observation  of  Lewkowitsch  that  by  heating 
cholesterol  with  normal  alcoholic  potash,  cholesterin  hydrate  is  obtained. 

The  following  test  will  serve  to  differentiate  between  cholesterol  and  phytosterol.2 
A  very  small  quantity  of  cholesterol  is  warmed  with  1.5  cc.  absolute  alcohol  and  a 

1  J.  Soc.  Chem.  Ind.,  17,  954,  1898;   Tolman,  J.  Am.  Chem.  Soc.,  27,  590,  1905; 
Tolman,  Bull.  107,  U.  S.  Dept.  Agriculture,  1907. 

2  Neuberg  and  Rauchwerger,  abstr.  J.  Soc.  Chem.  Ind.,  23,  1163,  1904. 


FIXED   OILS,   FATS   AND   WAXES  591 

trace  of  isodulcit  or  rhamnose  (5-dimethylfurfural)  added.  After  cooling,  an  equal 
volume  of  concentrated  sulphuric  acid  is  added,  so  as  to  form  a  layer  below  the  solu- 
tion, whereupon  a  raspberry-colored  ring  is  produced  at  the  zone  of  contact  of  the 
two  liquids.  •  On  mixing  the  layers  while  the  tube  is  cooled  in  a  current  of  cold  water 
the  mixture  becomes  intensely  colored.  With  phytosterol  the  reaction  fails  or  at 
most  a  pink  color.  Similar  reactions  are  given  by  abietic  acid. 

As  little  as  1%  of  cotton-seed  has  been  found  in  lard,  and  4%  in  any  oil  have  been 
detected  by  this  test. 

For  the  means  of  distinguishing  between  drying  and  marine  animal  oils,  see  Halphen, 
J.  Pharm.  Chim.,  14,  391  (1901),  abstracted  J.  Soc.  Chem.  Ind.,  21,  74,  or  Chem. 
Centralb.,  72,  ii,  1097  and  1323. 

Tests  for  Antifluorescents.1  It  is  often  desired  to  remove  the  fluorescence 
or  "  bloom  "  from  petroleum  oils.  This  may  be  effected  by  refining  with  chromic 
acid,  or  more  easily  by  the  addition  of  a  small  quantity  of  nitro-naphthalene 
or  nitro-benzene.  The  latter  may  often  be  detected  by  the  odor. 

The  test  is  made  by  boiling  about  1  cc.  of  the  oil  with  3  cc.  of  10%  alcoholic 
potash  for  one  to  two  minutes.  If  either  of  the  nitro  compounds  be  present, 
a  blood-  or  violet-red  coloration  is  produced;  a  pure  mineral  oil  is  changed  only 
to  yellow  or  brownish-yellow  by  this  treatment.  In  case  the  characteristic  color 
does  not  appear  the  following  test  may  be  applied.2  It  depends  upon  the  reduc- 
tion of  the  nitro  bodies  to  their  amines. 

A  few  cc.  of  the  oil  are  heated  with  feathered  tin  and  hydrochloric  acid 
in  an  Erlenmeyer  flask  for  ten  minutes:  this  can  be  aided  by  the  introduction  of 
a  piece  of  platinum  wire.  The  oil  is  separated  by  a  separatory  funnel  and  filtra- 
tion through  a  wet  filter,  the  filtrate  treated  in  another  separatory  with  sodium 
hydrate  until  the  tin  hydrate  redissolves  and  shaken  out  with  10-20  cc.  of  ether. 
The  amines  go  into  solution  in  the  ether,  giving  to  it  a  violet  color  and  fluores- 
cence in  the  case  of  a-naphthylamine.  These  can  be  recognized  by  their  odor, 
that  of  naphthylamine  being  very  characteristic.  The  latter  may  be  recog- 
nized by  dissolving  in  hydrochloric  acid,  evaporating  the  latter,  and  upon,  treat- 
ment with  ferric  chloride  obtaining  an  azure-blue  precipitate.  This  changes  when 
filtered  off  to  purple-red  and  the  filtrate  to  violet. 

Aniline  can  be  recognized  by  solution  in  concentrated  sulphuric  acid  and 
the  red  and  then  blue  color  which  appears  on  the  addition  of  a  small  crystal  of 
potassium  bichromate.  Free  aniline  is  also  temporarily  colored  violet  by  a  solu- 
tion of  bleaching  powder. 

Acetyl  Value.  The  estimation  of  the  acetyl  value  is  seldom  required  in  oil 
analysis,  it  being  characteristic  only  when  triglycerides  are  present.  For  a 
description  of  the  method  and  its  applications,  reference  must  be  had  to  the 
larger  works,  as  Lewkowitsch  or  Allen. 

Special  Tests  for  Certain  Oils 

Lewkowitsch  says 3  "  It  should  be  distinctly  understood  that  color  reactions 
taken  by  themselves  should  not  be  relied  upon  as  giving  a  decisive  answer.  At 
best  they  can  only  be  used  as  a  preliminary  test,  or  as  a  confirmatory  test.  The 
ease  with  which  this  test  can  be  carried  out,  and  its  apparent  reliability,  have 
led  to  an  over-estimation  of  this  very  useful  and  important  reaction;  so  much 

1  Holde,  J.  Soc.  Chem.  Ind.,  13,  906,  1893. 

2  Holde,  "  Examination  of  Hydrocarbon  Oils,"  p.  168. 

3  "  Chemical  Technology  and  Analysis  of  Fats,  Oils  and  Waxes,"  2,  203. 


592  FIXED   OILS,   FATS   AND   WAXES 

so,  that  grave  errors  may  be  committed  by  those  who  assign  to  this  test  an  exclu- 
sive or  even  a  paramount  importance.  It  is  altogether  unjustifiable  to  look  upon 
this  test,  as  has  been  done,  as  permitting  of  quantitative  interpretation." 

Bechi's  Test  for  Cotton-seed  Oil.  This  depends  upon  the  supposition  that 
a  substance  of  an  aldehydic  nature  which  reduces  silver  nitrate  is  contained 
in  the  oil.  The  method  is  essentially  that  of  Milliau.1 

Fifteen  grams  of  oil  are  weighed  into  a  No.  6  porcalain  dish,  using  the  coarse 
scales,  and  heated  for  about  ten  minutes  upon  the  water  bath;  a  mixture  of  10  cc. 
of  30%  caustic  soda  and  10  cc.  of  the  alcohol  is  slowly  poured  upon  the  oil. 
The  whole  is  occasionally  stirred  until  the  mass  becomes  clear  and  homo- 
geneous, and  150  cc.  of  hot  distilled  water  slowly  added  so  as  not  to  decompose 
the  soap,  and  the  boiling  continued  until  the  alcohol  is  expelled.  Dilute  sul- 
phuric acid  (1:10)  is  added  to  acid  reaction,  and  the  separated  fatty  acids  washed 
three  times  by  decantation  with  cold  water.  A  portion  of  these  is  brought  into 
a  large  test-tube,  15  cc.  of  alcohol  and  2  cc.  of  3%  silver  nitrate  solution  are 
added,  the  tube  is  wrapped  with  brown  paper,  held  in  place  by  an  elastic  band, 
and  heated,  with  constant  stirring,  in  the  water  bath  until  one-third  of  the 
alcohol  is  expelled,  which  is  replaced  by  10  cc.  of  water.  This  heating  is  con- 
tinued for  a  few  minutes  longer  and  the  coloration  of  the  insoluble  fatty  acids 
observed.  The  presence  of  cotton-seed  oil  in  any  appreciable  proportion  causes 
a  mirrorlike  precipitate  of  metallic  silver,  which  blackens  the  fatty  acids  of  the 
mixture. 

NOTES.  The  alcohol  should  be  proved  free  from  aldehyde  by  a  blank  test.  Un- 
less the  mixture  in  the  test-tube  be  thoroughly  stirred  while  heating,  it  will  "bump" 
and  eject  the  contents.  Other  methods  of  procedure  consist  in  applying  the  test  to 
the  oil  itself,  often  after  treatment  with  dilute  caustic  soda  and  nitric  acid.  (Wesson.2) 
The  writer  had  a  case  in  which  the  oil  gave  the  test  while  the  fatty  adds  gave  no 
blackening,  showing  there  was  something  in  the  oil  itself  other  than  cotton-seed  oil 
which  reduced  the  silver  nitrate.  Students  have  no  difficulty  in  detecting  a  5% 
adulteration  with  cotton-seed  oil. 

Dupont 3  thinks  that  the  reduction  of  silver  nitrate  is  due  rather  to  sulphur  com- 
pounds contained  in  the  oil;  by  passing  steam  over  the  oil  he  obtained  a  product 
containing  sulphur  and  the  oil  still  gave  the  Bechi  test.  This  work  has  been  repeated 
and  confirmed  by  the  author.4  It  is  to  be  noted  that  while  the  fatty  acids  blacken 
silver  nitrate  they^  do  not  color  cadmium,  lead,  or  copper  salts,  but  reduce  mercury 
compounds.  No  indication  of  an  aldehyde  was  noted  by  the  fucnsine  or  ammonia 
tests.  The  supposition  that  the  reducing  substance  is  aldehydic  in  its  nature  finds 
support  in  the  fact  that  if  the  oil  be  heated  to  240°  5  or  be  kept  for  some  time  6  it 
loses  this  peculiar  property. 

By  purifying  the  acids  by  the  lead  salts  Tortelli  and  Ruggeri  7  are  able  to  detect 
as  little  as  10%  of  heated  cotton-seed  oil. 

It  is  to  be  noted  that  pure  lard,  tung  and  olive  oil  are  not  infrequently  met 
with  which  give  the  test,  consequently  its  indications  cannot  be  considered  as 
conclusive. 

Halphen's  Test  for  Cotton-seed  Oil.8    This  depends  upon  the  observation 

1  J.  Am.  Chem.  Soc.,  15, 164,  1893. 
8  J.  Am.  Chem.  Soc.,  17,  723,  1895. 

«  Bull.  Soc.  Chem.  (3),  13,  696;  J.  Soc.  Chem.  Ind.,  14,  811,  1895;  also  Charabot 
and  March,  Bull.  Soc.  Chim.,  21,  252,  1899. 

4  Gill  and  Dennison,  J.  Am.  Chem.  Soc.,  24,  397,  1902. 
6  ftolde,  J.  Soc.  Chem.  Ind.,  11,  637,  1892. 

6  Wilson,  Chem.  News,  59,  99,  1889. 

7  J.  Soc.  Chem.  Ind.,  20,  753,  1901. 

8  Halphen,  J.  Pharm.  Chim.,  390,  1897. 


FIXED  OILS,   FATS  AND   WAXES  593 

that  this  oil  contains  an  unsaturated  fatty  acid  which  combines  with  sulphur, 
giving  a  colored  compound.1 

Procedure.  Ten  cc.  of  the  oil  or  melted  fat  are  heated,  in  a  large  test-tube 
with  a  long  glass  condenser  tube  attached,  with  an  equal  volume  of  amyl  alco- 
hol and  of  carbon  bisulphide  solution  of  sulphur  (Reagents),  at  first  with  frequent 
agitation,  in  a  steam  bath,  and  then,  after  the  violent  boiling  has  ceased,  in  a 
brine  bath  (105-110°)  for  forty-five  minutes  to  three  hours,  according  to  the  quan- 
tity of  adulterant  present,  the  tube  being  occasionally  removed  and  shaken. 
As  little  as  1%  will  give  a  crimson  wine  coloration  in  twenty  minutes.2 

NOTES.  If  the  mixture  be  heated  for  too  long  a  time  a  misleading  brownish- 
red  color  due  to  burning  is  produced.  The  reaction  seems  to  be  peculiar  to  this  oil; 
it  is  more  sensitive  with  fresh  than  old  fats,  and  while,  by  comparison  with  a  blank, 
^  of  1%  is  noticeable,  \  of  1%  is  easily  detected.  Cotton-seed  oil  which  has  been 
heated  to  250°  does  not  give  the  test;  the  oil  is  then  not  available  as  food.  Heating 
to  200°  does  not  interfere  with  the  test.3 

The  test  is  not  given  by  an  oil  which  has  been  oxidized  with  sulphuric  acid  and 
potassium  permanganate,  although  such  an  oil  gives  the  Bechi  test.4  This  shows 
that  the  two  tests  are  not  produced  by  the  same  substance.  Nor  is  this  test  or  that 
of  Bechi  given  by  an  oil  which  has  been  treated  with  chlorine  or  sulphurous  acid.5 
If  treated  with  the  former  it  is  no  longer  edible;  an  oil  treated  with  sulphurous  acid 
and  washed  with  alcohol  cannot  be  distinguished  from  ordinary  cotton-seed  oil  and 
does  not,  as  already  stated,  respond  to  either  the  Halphen  or  Bechi  test.  In  this 
case  the  test  for  phytosterol  is  the  only  means  of  determining  if  it  has  been  added 
to  an  animal  oil.  The  test  is  also  given  by  kapok  oil,  which  is  used  as  an  edible  oil  in 
China,  the  East  and  West  Indies,  and  in  Africa;  baobab  oil  also  gives  it. 

Lard  from  hogs  fed  on  cotton-seed  meal  shows  this  reaction  strongly,  as  if  it  were 
25%  oil.6  The  butter  from  cows  similarly  fed  also  yields  the  reaction.7 

The  test  may  be  applied  to  the  soaps  or  fatty  acids,  provided  they  are  not  too 
deeply  colored. 

The  amyl  alcohol  cannot  be  omitted  nor  substituted  by  ethyl  alcohol  without 
impairing  the  delicacy  of  the  test.8  The  compound  in  the  oil  cannot  be  removed 
by  treating  with  animal  charcoal.9 

Hexabromide  Test  for  Linseed  Oil.  The  object  of  the  test  is  to  determine  the 
amount  of  insoluble  bromides  of  the  fatty  acids  contained  in  the  oil. 

Fifteen  grams  of  the  oil  are  saponified  by  boiling  with  15  cc.  of  potassium  hydrox- 
ide solution,  sp.gr.,  1.35,  and  15  cc.  of  alcohol  in  a  flask  under  a  reflux  condenser; 
300  cc.  of  warm  water  are  added  and  the  solution  distilled  with  steam  until  the 
alcohol  is  removed.  Dilute  sulphuric  acid  is  added  to  excess,  the  solution  heated 
until  the  fatty  acids  are  obtained  as  a  clear  oily  upper  layer;  this  is  washed  several 
times  with  hot  distilled  water  until  free  from  sulphuric  acid,  using  methyl  orange 
as  an  indicator.  This  does  not  react  with  fatty  acids  of  low  molecular  weight 
which  being  soluble  in  water  may  redden  litmus.  This  washing  is  effected  in  an 
atmosphere  of  inert  gas,  carbonic  acid  or  hydrogen  by  stopping  the  flask  with  a 
three-holed  stopper,  carrying  a  siphon,  an  entrance  and  an  exit  tube  for  the  gas. 

1  Raikow,  Chem.  Ztg.,  24,  562,  583,  1900. 

2  Oilar,  Am.  Chem.  J.,  24,  355;  abstr  Anal.,  28,  22,  1901. 

3  Fischer  and  Peyan,  Analyst,  30,  131,  1905;  Soltsien,  Z.  offentl.  Chem.,  5,  135. 
1899;  J.  Soc.  Chem.  Ind.,  18,  865. 

4  Raikow,  loc.  cit. 

6  Petkow,  Analyst,  32,  123,  1907. 

6  Soltsien,  Z.  offentl.  Chem.,  7,  140,  1901. 

7  Wauters,  J.  Soc.  Chem.  Ind.,  li),  172,  1900. 

8  Soltsien,  loc.  cit.,  25,  Oilar,  loc.  cit. 

9  Utz,  Rev.  Fett  u.  Harz.  Ind.,  9,  125,  1902. 


594 


FIXED   OILS,  FATS   AND   WAXES 


The  acids  are  siphoned  into  a  small  Erlenmeyer  flask  and  in  case  a  few  drops  of 
water  come  over — an  equal  quantity  of  alcohol  added  and  dried  upon  the  water 
bath  in  a  stream  of  dry  inert  gas. 

In  order  to  test  for  the  presence  of  unsaponified  fat,  3  cc.  are  dissolved  in 
15  cc.  of  95%  (by  volume)  alcohol,  and  15  cc.  of  aqueous  ammonia  are  added.  If 
an  appreciable  amount  of  fat  has  escaped  saponification,  the  mixture  will  become 
turbid  (Geitel). 

Two  grams  of  mixed  fatty  acids  l  are  dissolved  in  a  flask  in  27  cc.  of  dry  ether, 
cooled  down  to  10°  C.,  and  0.25  cc.  of  bromine  allowed  to  run  into  the  solution 
from  a  very  finely-drawn-out  pipette,  the  time  allowed  for  this  being  about  twenty 
minutes.  The  remaining  0.25  cc.  of  bromine  is  added  somewhat  more  rapidly, 
within  about  ten  minutes,  the  bromination  thus  occupying  about  thirty  minutes. 
The  authors  attach  great  value  to  the  exact  observance  of  the  time.  The  tempera- 
ture should  never  be  allowed  to  rise  during  bromination  above  5°.  The  flask  is 
corked  and  allowed  to  stand  for  two  hours  at  0°.  The  ethereal  solution  is  next 
decanted  through  a  weighed  asbestos  or  paper  filter  (Lewkowitsch)  and  the 
precipitate  is  washed  with  five  lots  of  5  cc.  each  of  dried  and  cooled  ether.  After 
complete  draining,  the  precipitate  is  dried  for  two  hours  at  80°  to  85°,  and  allowed 
to  cool  in  a  desiccator.  The  temperature  is  designedly  kept  below  100°,  as  the 
authors  found  that  the  color  of  the  hexabromide  becomes  somewhat  gray  if  the 
drying  takes  place  at  100°.  The  melting-point  of  the  hexabromides  was  177°, 
whereas  the  melting-point  of  pure  hexabromide  has  been  found  to  be  higher. 
No  doubt  the  low  melting-point  is  due  to  the  drying  having  been  carried  out  below 
100°. 

Nevertheless  small  traces  of  retained  moisture  cannot  account  for  the  much 
larger  yield  of  hexabromide  which  the  authors  obtained. 

The  yields  of  hexabromide  obtained  by  these  authors  are  as  follows: 


Fatty  Acids 

Per  cent. 

Fatty  Acids 

Per  cent. 

Perilla  oil. 

64  12 

Tung  oil.                 

nil 

Linseed  oil,  Baltic 

57  96 

Soya  bean  oil      

up  to  7  .  78 

Linseed  oil,  Dutch 

51  73 

Poppy  seed  oil      

nil 

Linseed  oil  La  Plats. 

51  66 

Rape  oil 

6  34 

Linseed  oil.  Indian  

50  50 

Renard's  Test  for  Peanut  Oil.2  Tolman 3  has  modified  this  as  follows: 
Weigh  20  grams  of  oil  into  an  Erlenmeyer  flask.  Saponify  with  alcohol 
potash,  neutralize  exactly  with  dilute  acetic  acid,  using  phenolphthalein  as  indie 
tor,  and  wash  into  a  500-cc.  flask  containing  a  boiling  mixture  of  100  cc.  of  wat 
and  120  cc.  of  a  20%  lead  acetate  solution.  Boil  for  a  minute  and  then  cool  tl 
precipitated  soap  by  immersing  the  flask  in  water,  occasionally  giving  it  a  whirlii 
motion  to  cause  the  soap  to  stick  to  the  sides  of  the  flask.  After  the  flask  has 
cooled,  the  water  and  excess  of  lead  can  be  poured  off  and  the  soap  washed  with 
cold  water  and  with  99%  (by  volume)  alcohol.  Add  200  cc.  of  ether,  cork,  am 
allow  to  stand  for  some  time  until  the  soap  is  disintegrated,  heat  on  the  wat 

1  Eibner  and  Muggenthaler,  Farben  Ztg.,  1912. 

*  Renard,  Compt.  rend.,  73, 1330,  1871;  also  Archbutt,  J.  Soc.  Chem.  Ind.,  17,  11! 

1  Bull.  107.  U.  S.  Dept.  Agriculture,  1907,  p.  145. 


FIXED   OILS,   FATS   AND   WAXES  595 

bath,  using  a  reflux  condenser,  and  boil  for  about  five  minutes.  In  the  oils  most 
of  the  soap  will  be  dissolved,  while  in  lards,  which  contain  much  stearin,  part 
will  be  left  undissolved.  Cool  the  ether  solution  of  soap  to  15°  or  17°  C.  and 
let  it  stand  until  all  the  insoluble  soaps  have  crystallized  out  (about  twelve 
hours). 

Filter  and  thoroughly  wash  the  precipitate  with  ether.  Wash  the  soaps  on 
the  filter  back  into  the  flask  by  means  of  a  stream  of  hot  water  acidified  with 
hydrochloric  acid.  Add  an  excess  of  dilute  hydrochloric  acid,  partially  fill  the 
flask  with  hot  water,  and  heat  until  the  fatty  acids  form  a  clear  oily  layer.  Fill  the 
flask  with  hot  water,  allow  the  fatty  acids  to  harden  and  separate  from  the  pre- 
cipitated lead  chloride,  wash,  drain,  repeat  washing  with  hot  water,  and  dissolve 
the  fatty  acids  in  100  cc.  of  boiling  90  per  cent  (by  volume)  alcohol.  Cool  to 
15°  C.,  shaking  thoroughly  to  aid  crystallization. 

From  5  to  10  per  cent  of  peanut  oil  can  be  detected  by  this  method,  as  it 
effects  a  complete  separation  of  the  soluble  acids  from  the  insoluble,  which  inter- 
fere with  the  crystallization  of  the  arachidic  acid.  Filter,  wash  the  precipitate 
twice  with  10  cc.  of  90%  (by  volume)  alcohol,  and  then  with  alcohol  70%  (by  vol- 
ume). Dissolve  off  the  filter  with  boiling  absolute  alcohol,  evaporate  to  dryness 
in  a  weighed  dish,  dry  and  weigh.  Add  to  this  weight  0.0025  gram  for  each  10  cc. 
of  90%  alcohol  used  in  the  crystallization  and  washing  if  done  at  15°  G.;  if  done 
at  20°  add  0.0045  gram  for  each  10  cc.  The  melting-point  of  arachidic  acid  thus 
obtained  is  between  71°  and  72°  C.  Twenty  times  the  weight  of  arachidic  acid 
will  give  the  approximate  amount  of  peanut  oil  present.  No  examination  for 
adulterants  in  olive  oil  is  complete  without  making  the  test  for  peanut  oil.  Ara- 
chidic acid  has  a  characteristic  structure  and  can  be  detected  by  the  microscope. 

Bach's  Test  for  Rapeseed  Oil.  According  to  O.  Bach,1  the  acids  obtained  from 
rape-seed  oil  are  completely  insoluble  in  David's  alcoholic  acetic  acid,  in  the 
proportion  of  1  to  15,  by  volume;  those  from  cottonseed,  peanut,  sesame,  and 
sunflower  oil  dissolve  on  heating.  Those  from  the  last  oil  separate  as  a  granular 
precipitate  at  15°,  while  from  the  other  three  they  gelatinize.  The  acids  from 
olive  oil  are  completely  soluble  at  the  ordinary  temperature.  David's  acid  is 
made  by  mixing  22  cc.  of  50%  acetic  acid  (by  volume)  with  30  cc.  of  alcohol,  sp.gr. 
0.817,  92.07%  (by  weight.) 

NOTE.  The  author  has  found  that  Bach's  observation  cannot  be  implicitly 
relied  upon,  as  some  rape-seed  oils  yield  acids  which  are  soluble  in  David's  mixture. 

Liebermann-Storch  Test  for  Rosin  Oil.  One  or  2  cc.  of  the  oil  are  shaken 
with  an  equal  quantity  of  acetic  anhydride  and  gently  warmed.  When  cool 
the  acetic  anhydride  is  pipetted  off  and  tested  by  the  addition  of  1  drop  of  con- 
centrated sulphuric  acid.  A  fine  violet  color  is  produced  in  the  presence  of  rosin 
oil.  Tung  oil  and  also  cholesterol,  which  is  contained  in  the  animal  fats,  produce 
a  similar  coloration;  the  latter  can  be  removed  by  saponifying  the  oil  as  completely 
as  possible  and  shaking  out  the  somewhat  dilute  soap  solution  with  ether  or 
petroleum  ether.  The  soap  solution  is  then  acidified,  setting  free  the  fatty 
acids,  and  these  treated  with  acetic  anhydride  as  if  they  were  the  oil. 

Baudouin's,  or  Camoin's  test  for  Sesame  Oil.  Villavecchia  and  Fabris2 
apply  the  test  as  follows:  0.1  gram  sugar  is  dissolved  in  10  cc.  of  hydrochloric  acid 

1  Allen,  "  Commercial  Organic  Analysis,"  2,  pt.  1,  128,  1899. 

2  Z.  angew.  Chem.,  509,  1892:  abstr.  J.  Soc.  Chem.  Ind.,  12,  67;  also  Kerp,  Analyst, 
24,  246,  1899. 


596 


FIXED  OILS,  PATS  AND  WAXES 


of  specific  gravity  1.18  in  a  test-tube,  and  20  grams  of  the  oil  to  be  tested  added, 
the  whole  thoroughly  shaken  and  allowed  to  stand.  In  the  presence  of  1%  of 
sesame*  oil  the  aqueous  liquid  will  be  colored  red,1  due  to  the  action  of  the  fur- 
furol  formed  upon  the  oil.  They  state  that  as  olive  oils  of  undoubted  purity  have 
shown  the  reaction  in  the  aqueous  layer  and  not  in  the  oily  stratum,  the  color  should 
be  looked  for  in  the  latter. 

The  sugar  may  be  replaced  by  0.1  cc.  of  a  2%  solution  of  furfurol  and  half  the 
quantity  of  oil  used. 

Milliau2  saponifies  as  in  the  Bechi  test  and  dries  the  acids  at  105°.  Lew- 
kowitsch  3  states  that  this  is  a  needless  complication.  Da  Silva 4  states  that  this 
test  has  given  colors  with  certain  Portuguese  olive  oils;  also  those  of  Bari  Brindisi 
and  Lecce.  Kreis B  states  that  the  active  or  color-giving  constituent  is  probably 
phenolic  in  its  nature.  The  reaction  is  given  by  other  substances,6  as  vanillin,  oil 
of  cloves,  and  cinnamon;  this  should  be  borne  in  mind  in  testing  oils  which  have 
been  extracted  from  confectionery.  Rancid  fats  prevent  the  coloration;  it  can, 
however,  be  brought  about  even  in  rancid  fats  by  the  addition 
of  an  equal  quantity  of  cotton-seed  oil. 7 

Free  Acid  Test.  About  10  grams  of  oil  are  weighed  (to 
centigrams)  into  a  250-cc.  Erlenmeyer  flask,  60  cc.  of  neutral 
alcohol  (Reagents)  added,  the  mixture  warmed  to  about  60° 
C.,  and  titrated  with  N/6  potassium  hydrate,  using  phenol- 
phthalein,  the  flask  being  frequently  and  thoroughly  shaken. 
The  result  is  conventionally  reported  in  per  cent  of  oleic  acid; 
1.0  cc.  N/6  KOH  is  equivalent  to  0.047  gram  oleic  acid.  Or 
it  can  be  reported  like  the  saponification  number,  in  milli- 
grams of  KOH  per  gram  of  oil. 

Spontaneous  Combustion  Test.  Mackey's  Apparatus. 
The  apparatus,8  Fig.  92a,  consists  of  a  cylindrical  copper  water 
bath  7  in.  high  and  4  in.  in  diameter  (inside  measurements), 
surrounded  with  a  £-in.  water-jacket.  The  cover  is  packed 
with  asbestos  and  carries  the  draft  tubes  A  and  B,  |  in.  in 
diameter  and  6  in.  long,  which  cause  a  current  of  air  to  be 
sucked  down  B  and  up  A,  thus  ensuring  a  circulation  of  air 
in  the  apparatus:  C  is  a  cylinder  made  of  24-mesh  wire  gauze 
6  in.  high  and  1^  in.  in  diameter  and  supported  upon  a  pro- 
jection from  the  bottom  of  the  bath.  A  thermometer  projects 
down  into  the  center  of  the  cylinder;  if  a  metal  condenser 
the  water  bath  it  can  be  used  indefinitely  without  refilling 


FIG.  92a. 

Mackey's  Appa- 
ratus. 


be  connected  to 

and  without  danger  of  burning  out. 

Seven  grams  of  ordinary  bleached  cotton  wadding  or  "  absorbent  cotton  " 
are  weighed  out  in  a  porcelain  dish  or  on  a  watch-glass,  and  14  grams  of  the  oil 
to  be  tested  poured  upon  the  cotton  and  thoroughly  worked  into  it,  care  being 

llbid.,  1893,  505;  abstr.  Analyst,  19,  47. 

*  J.  Am.  Chem.  Soc.,  15,  162,  1893. 
1 "  Oils,  Fats  and  Waxes." 

4  J.  Soc.  Chem.  Ind.,  17,  275,  1898. 

6  Chem.  Ztg.,  27,  316,  1903. 

8  Gerber,  Analyst,  32,  90,  1907. 

7  Lauff  and  Hinsmann,  Chem.  Ztg.,  31,  1023,  1908. 

•  Mackey,  J.  Soc.  Chem.  Ind.,  15,  90,  1896;  Gill,  ibid.,  26,  185,  1907. 


FIXED  OILS,  FATS  AND  WAXES 


597 


taken  to  replace  any  oil  that  is  lost.  The  cotton  is  then  placed  in  the  cylinder, 
packed  about  the  thermometer  so  that  it  occupies  the  upper  4|  in.  of  the  cylinder, 
and  put  into  the  boiling  water  bath.  After  the  expiration  of  an  hour,  the  bath 
having  been  "kept  in  active  ebullition,  the  temperature  is  read.  Any  oil  which 
shows  a  temperature  exceeding  100°  C.  in  one  hour,  or  200°  C.  in  two  hours,  should 
be  regarded  as  a  dangerous  oil,  or  liable  to  produce  spontaneous  combustion.  The 
following  tables  show  the  results  obtained  in  using  this  apparatus. 


Oil. 

Temperature  °C.  in 

1  hr. 

1J  hrs. 

1J  hrs. 

Olive  (neutral)  ...            .    . 

97-98 
112-128 
98-103 
102-114 

100 
177-242 
101-115 

101 

194-282 
102-191 
196 

Cotton-seed  

Elaine    

Olive  fatty  acids 

Other  values  obtained  were : 


Oil. 

Temp. 
°C 

Time 
Minutes. 

Iodine, 
No. 

Free  Acid, 
per  cent. 

Olive 

234 

130 

85  4 

5  3 

Lard 

234 

75 

75  2 

Trace 

Oleic  acid 

158 

188 

60  5 

Cotton-seed 

234 

70 

108  9 

Neutral 

Linseed                           . 

234 

65 

168  1 

Neutral 

25°  Paraffin                

97 

135 

16  2 

Besides  being  used  for  testing  oils  it  can  be  applied  to  testing  other  materials, 
oily  waste,  sawdust,  or  any  mixtures  suspected  of  causing  spontaneous  combustion. 

"  The  results  l  of  the  greatest  practical  value  obtained  in  the  use  of  this  appa- 
ratus have  been,  first,  determining  the  cause  of  fires;  and,  second,  determining  the 
degree  of  safety  of  the  various  oils  used  in  manufacturing.  Mineral  oil,  as  is 
well  known,  is  not  liable  to  spontaneous  combustion;  and  a  certain  percentage  of 
animal  or  vegetable  oil  may  be  added  to  mineral  oil  without  materially  increasing 
the  danger  under  ordinary  circumstances.  This  percentage  varies  according  to 
the  oil;  with  neat's-foot  and  first  quality  lard  oil  some  50  to  60%  may  be  used,  with 
cotton-seed  not  over  25%  is  allowable.  The  claim  so  often  made  for  so-called 
1  safe '  oils,  said  to  have  been  changed  by  special  and  secret  processes  of  refining 
so  as  to  be  no  longer  dangerous,  is  easily  exposed  by  this  test." 

Drying  Test  Upon  Glass.2  A  few  drops  of  oil  are  brought  upon  a  glass  plate 
inclined  at  about  30°  from  the  horizontal.  A  test  of  the  oil  is  made  from  time 
to  time  by  touching  it  with  the  fingers,  the  time  at  which  it  does  not  soil  them 
being  noted  as  the  point  when  it  is  dry.  Good  oil  should  dry  in  three  days. 

Archbutt s  makes  this  test  as  follows :  A  piece  of  polished  plate-glass  7  cm. 
square  by  4  mm.  thick  is  cleaned  and  counterpoised  on  the  balance;  it  is  then 
heated  for  an  hour  at  200°  C.  in  an  air  bath  to  thoroughly  dry  it.  It  is  taken  out, 

1  Richards,  Tech.  Quarterly,  4,  346,  1891. 

2  Amsel,  J.  Soc.  Chem.  Ind.,  15,  222,  1896. 
» J.  Soc.  Chem.  Ind.,  18,  347,  1899. 


598  FIXED   OILS,   FATS   AND   WAXES 

laid  on  a  non-conductor,  allowed  to  cool  for  three  or  four  minutes,  and  the  hot  glass 
thinly  painted  with  the  oil  to  be  tested  by  means  of  a  camel's-hair  brush.  When 
the  glass  is  cold  it  is  weighed  and  sufficient  oil  added  to  make  it  up  to  0.1  gram. 
Two  glasses  are  coated  with  the  sample  and  two  with  a  standard  oil,  all  placed  on 
a  level  surface  in  a  large  air  bath  at  50°  C.  and  heated  for  nine  hours;  one  set  of 
plates  is  withdrawn,  cooled,  and  tested  by  the  finger.  Good  raw  linseed  is  tacky, 
when  tested  by  the  finger  when  cold,  in  nine  hours  and  dry  in  twelve;  corn  oil  is 
practically  dry  in  fifteen  hours,  though  slightly  tacky;  cottonseed,  partially  dry 
in  eighteen  hours  and  fully  dry  in  twenty-one.  Refined  rape  oil  dried  in  forty- 
eight  hours,  and  olive  oil  was  sticky  after  thirteen  days. 

Titer  Test.  Under  this  rather  misleading  title  is  expressed  the  solidification 
point  of  the  fatty  acids  derived  from  a  fat  or  oil ;  it  has  nothing  at  all  to  do  with 
titration,  as  might  be  expected.  The  test  is  extensively  used  for  the  evaluation 
of  fats,  and  according  to  the  method  provisionally  adopted  by  the  Association  of 
Official  Agricultural  Chemists  is  carried  out  as  follows:1 

(a)  Standard  Thermometer.    The  thermometer  must  be  graduated  in  tenth 
degrees  from  10°  to  60°,  with  a  zero  mark,  and  have  an  auxiliary  reservoir  at 
the  upper  end,  also  one  between  the  zero  mark  and  the  10°  mark.     The  cavity 
in  the  capillary  tube  between  the  zero  mark  and  the  10°  mark  must  be  at  least 
1  cm.  below  the  10°  mark,  the  10°  mark  to  be  about  3  or  4  cm.  above  the  bulb, 
the  length  of  the  thermometer  being  about  15  in.  over  all.     The  thermometer  is 
annealed  for  75  hours  at  450°  C.,  and  the  bulb  is  of  Jena  normal  16"'  glass, 
moderately  thin,  so  that  the  thermometer  will  be  quick  acting.    The  bulb  is  about 
3  cm.  long  and  6  mm.  in  diameter.    The  stem  of  the  thermometer  is  6  mm.  in 
diameter  and  made  of  the  best  thermometer  tubing,  with  scale  etched  on  the  stem, 
the  graduation  to  be  clear-cut  and  distinct,  but  quite  fine. 

(b)  Determination.    Saponify  75  grams  of  fat  in  a  metal  dish  with  60  cc.  of  30% 
sodium  hydroxide  (36°  Baume*)  and  75  cc.  of  95%  (by  volume)  alcohol  or  120  cc. 
of  water.     Boil  to  dryness,  with  constant  stirring  to  prevent  scorching,  over  a  very 
low  flame  or  over  an  iron  or  asbestos  plate.  Dissolve  the  dry  soap  in  a  liter  of  boiling 
water,  and  if  alcohol  has  been  used,  boil  for  forty  minutes  in  order  to  remove  it,  add- 
ing sufficient  water  to  replace  that  lost  in  boiling.    Add  100  cc.  of  30%  sulphuric 
acid  (25°  Baume*)  to  free  the  fatty  acids,  and  boil  until  they  form  a  clear,  trans- 
parent layer.    Wash  with  boiling  water  until  free  from  sulphuric  acid,  collect  in 
a  small  beaker,  and  place  on  the  steam  bath  until  the  water  has  settled  and  the 
fatty  acids  are  clear;  then  decant  them  into  a  dry  beaker,  filter,  using  the  hot- 
water  funnel,  and  dry  twenty  minutes  at  100°  C.    When  dried,  cool  the  fatty  acids 
to  15  or  20°  C.  above  the  expected  titer  and  transfer  to  the  titer  tube,  which  is 
25  mm.  in  diameter  and  100  mm.  in  length  (1  by  4  in.)  and  made  of  glass  about  1 
mm.  in  thickness.    Place  in  a  16-oz.  salt-mouth  bottle  of  clear  glass,  about  70 
mm.  in  diameter  and  150  mm.  high  (2.8  by  6  in.),  fitted  with  a  cork,  which  is  per- 
forated so  as  to  hold  the  tube  rigidly  when  in  position.    Suspend  the  thermometer, 
graduated  to  0.1°  C.,  so  that  it  can  be  used  as  a  stirrer,  and  stir  the  mass  slowly 
until  the  mercury  remains  stationary  for  thirty  seconds.    Then  allow  the  ther- 
mometer to  hang  quietly,  with  the  bulb  in  the  center  of  the  mass,  and  observe 
the  rise  of  the  mercury.    The  highest  point  to  which  it  rises  is  recorded  as  the 
titer  of  the  fatty  acids. 

Test  the  fatty  acids  for  complete  saponification  as  follows: 

1 U.  S.  Dept  of  Agriculture,  Bureau  of  Chemistry  Bulletin  No.  107,  p.  135,  1907. 


FIXED   OILS,   FATS   AND   WAXES 


599 


Place  3  cc.  in  a  test-tube  and  add  15  cc.  of  alcohol  (95%  by  volume).  Bring 
the  mixture  to  a  boil  and  add  an  equal  volume  of  ammonium  hydroxide  (0.96  sp.gr.). 
A  clear  solution  should  result,  turbidity  indicating  unsaponified  fat.  The  titer 
must  be  made  at  about  20°  C.  for  all  fats  having  a  titer  above  30°  C.  and  at  10°  C. 
below  the  titer  for  all  other  fats. 

References 

Heffter,  G.  Technologie  der  Fette,  Oele,  und  Wachsarten  des  Pflanzen  und  Tier- 
reichs.  4  volumes,  1906+ 

Ubbelohde,  L.  Chemie,  Analyse  und  Gewinnung  der  Oele,  Fette  und  Wachse.  4 
volumes,  1908+ 

EDIBLE   FATS 

These  include  butter,  lard  and  hardened  oils. 

Butter  is  examined  for  water,  fat,  ash,  curd,  and  salt;  these  are  usually  present 
in  the  following  proportions: 


Per  cent. 

Average  per  cent 

Fat.            

78.  -90 

82 

Water  

5.  -20 

12 

Salt  

0.4-15 

5 

Curd  

0.1-  5 

1 

These  are  determined  as  follows:  weigh  about  2  grams  of  butter  into  a  plat- 
inum Gooch  crucible  half  filled  with  ignited  fibrous  asbestos,  and  dry  it  at  100°  C. 
to  constant  weight.  The  loss  is  the  amount  of  water.  Dissolve  out  the  fat  by 
repeated  treatment  with  petroleum  ether  and  again  dry  to  constant  weight. 
The  loss  represents  the  amount  of  fat .  Ignite  the  crucible  with  a  low  flame  or  in 
a  muffle,  being  careful  not  to  volatilize  the  salt,  until  a  light-gray  ash  is  obtained. 
The  loss  represents  curd  and  the  residue  ash.  By  extraction  of  the  ash  with  water, 
and  neutralization  with  calcium  ca  .'Hate,  the  salt  can  be  titrated  with  silver 
nitrate. 

Examination  of  the  Fat.  Butter  is  adulterated  with  oleomargarine,  ren- 
ovated butter,  and  cocoanut  oil.  The  first  may  be  detected  by  testing  for 
cottonseed  or  sesame  oil  either  by  the  color  tests  or  by  the  index  of  refraction;  this 
at  25°  is  for  butter  1.459-1.462,  for  oleo.  1.465-1.470.  Owing  to  the  fact  that 
butter  contains  a  large  per  cent  of  volatile  fatty  acids  (butyric,  caproic,  caprylic 
and  capric  acids,  in  all  about  8%),  adulterants  may  be  detected  by  determining 
the  amount  of  these.  The  process  usually  employed  is  that  of  Reichert  modified 
by  Meissl. 

Five  grams  of  the  clear  fat,  filtered  through  absorbent  cotton,  are  weighed 
into  a  250-cc.  round-bottomed  flask  and  saponified  by  2  cc.  potassium  hydroxide 
1  : 1  and  lOcc.of  95%  alcohol,  under  a  return  flow  condenser  for  twenty-five  minutes. 
The  alcohol  is  rapidly  evaporated  off  on  the  water  bath  until  no  odor  of  alcohol  is 
perceptible.  Add  slowly  160  cc.  of  recently  boiled  distilled  water  which  has  been 
cooled  to  50°  or  60°;  warm  the  flask  until  a  clear  solution  of  the  soap  is  obtained. 
Cool  to  about  60°  and  add  8  cc.  sulphuric  acid  1  : 4  to  liberate  the  fatty  acids. 
Drop  into  the  flask  two  bits  of  pumice  (about  the  size  of  peas)  which  have  been 


600  FIXED   OILS,   FATS   AND   WAXES 

heated  and  quenched  in  water,  and  tie  in  a  well-fitting  cork;  warm  the  flask 
until  the  fatty  acids  have  melted  and  are  floating  on  the  liquid.  Cool  to  about 
60°  and  attach  the  flask  to  a  condenser,  using  a  trap  to  prevent  the  sulphuric 
acid  from  being  mechanically  carried  over;  110  cc.  are  distilled  into  a  graduated 
flask  in  as  nearly  thirty  minutes  as  possible.  Thoroughly  mix  the  distillate,  pour 
through  a  dry  filter,  and  titrate  100  cc.  with  N/10  NaOH,  using  phenolphthalein 
as  an  indicator.  Multiply  the  cc.  of  alkali  by  1.1  and  calculate  them  to  5  grams 
of  fat.  The  Reichert-Meissl  value  for  butter  is  from  24  to  34,  the  average  is  about 
28.8;  cocoanut  oil  gives  6-8  and  other  fats  less  than  1. 

The  procedure  is  a  conventional  one  and  should  be  followed  as  exactly  as 
possible.  Cocoanut  and  other  vegetable  oils  would  be  shown  by  the  fact  that 
the  unsaponifiable  matter  would  contain  phytosterol;  also  by  the  Polenske  number.1 
Renovated  butter  is  best  shown  by  the  "  Spoon  or  Foam  Test."  This  con- 
sists in  melting  a  third  of  a  teaspoonful  of  the  sample  in  a  tablespoon  over  a  small 
flame  and  stirring  with  a  match.  Increase  the  heat  until  the  fat  boils  briskly, 
stirring  thoroughly  several  times.  Oleomargarine  and  renovated  butter  boil 
noisily,  sputtering  like  a  mixture  of  grease  and  water  and  produce  no  foam. 
Butter  boils  with  less  noise  and  much  foam  sometimes  rising  over  the  sides  of  the 
spoon.  The  pieces  of  curd  in  butter  are  much  smaller  than  in  either  of  the  others. 

Preservatives,  benzoic,  boric  and  salicylic  acids,  may  be  examined  according 
to  the  procedure  given  in  Woodman  and  Norton,  "Air,  Water  and  Food,"  pp.  154 
and  196. 

Color  may  be  detected  according  to  Allen,  "  Commercial  Organic  Analysis," 
4th  Ed.,  Vol.  II,  or  Leach's  "  Food  Analysis." 

Lard  is  adulterated  with  water,  25%  being  added  in  some  cases,  with  cotton- 
seed oil  or  stearine  and  beef  stearine. 

Water  is  determined  as  with  butter;  cottonseed  oil  or  stearine  by  the  usual 
tests.  It  should  be  borne  in  mind,  however,  that  hogs  fed  on  cottonseed  meal 
yield  a  lard  which  will  give  the  Halphen  test  as  strongly  as  if  it  contained  25%  of 
the  oil.  The  iodine  number  and  the  presence  of  phytosterol  will  confirm  this 
test;  the  iodine  number  varies  widely  according  to  the  source  of  the  fat,  but  in 
general  it  may  be  said  it  should  be  between  46  and  66. 

Beef  stearine  is  very  difficult  if  not  impossible  of  detection.  For  this,  reference 
may  be  had  to  Lewkowitsch,  5th  Ed.,  Vol.  II. 

HARDENED  OILS 

As  the  name  denotes,  these  are  oils  which  have  been  changed  to  more  or 
less  solid  fats  by  the  addition  of  hydrogen,  in  the  presence  of  a  catalyst,  usually 
a  compound  of  nickel.  This  betrays  their  presence  and  may  be  tested  for  as 
follows:* 

Ten  grams  of  the  fat  are  heated  on  the  water  bath  with  10  cc.  of  hydrochloric 
acid  (sp.  gr.  1.12)  with  frequent  shaking  for  two  or  three  hours.  The  fat  is  removed 
by  filtering  through  a  wet  filter,  receiving  the  filtrate  in  a  porcelain  dish;  after 
partial  evaporation  of  the  filtrate  2  or  3  cc.  of  strong  nitric  acid  are  added  and 
the  evaporation  continued  to  dryness  to  ensure  the  destruction  of  the  organic 
matter.  The  residue  is  dissolved  in  a  few  cc.  of  distilled  water,  a  few  drops  of  a 

>Z.  Nahr.  Genussm.,  7,  193,  1904,  also  Leach,  "Food  Analysis." 
*Kerr,  J.  Ind.  and  Eng.  Chem.,  6,  207,  1914. 


FIXED   OILS,   FATS  AND  WAXES 


601 


1%  solution  of  dimethyl  glyoxime  in  alcohol  added,  and  a  few  drops  of  dilute 
ammonia.  The  presence  of  nickel  is  shown  by  the  appearance  of  the  red-colored 
nickel  dimethyl  glyoxime.  The  amount  of  nickel  can  be  determined  colori- 
metrically  by  comparison  with  solutions  containing  known  quantities. 

The  quantity  of  nickel  is  very  minute,  not  as  much  as  the  fats  take  up  when 
cooked  in  nickel  or  nickeled  dishes  and  need  cause  no  apprehension. 

Hydrogenation  destroys  all  the  characteristics,  particularly  the  color  tests, 
by  which  the  different  oils  may  be  sometimes  detected. 

WAXES 

These,  as  will  be  remembered,  contain  no  glycerine;  the  tests  applied  to  them  are 
the  same  as  to  the  oils.  The  characteristics  of  the  more  commonly  occurring  waxes 
are  given  in  the  table,  p.  606;  sperm  oil,  which  is  really  a  liquid  wax,  is  included 
among  the  oils. 


MISCELLANEOUS   OILS  AND  LUBRICANTS 

PROPERTIES  OF  SOME  OF  THE  MINERAL  OILS 


Oil. 

Specific 
gravity, 
deg.  Baumfi 
at  60°  F. 

Flash 
point, 
°F. 

Viscosity 
(Saybolt), 
at  70°  F. 

Cold  test, 
deg.  Fahr. 

Black  

29 

325 

100-120 

5-15 

Ice  machine    . 

26-27 

325-360 

60-100 

0-4 

Crank  case  

26-27 

455 

100 

Transformer 

340-380 

400 

25 

Turbine     . 

30 

420 

160 

Spindle.  .  .    . 

30-35 

320-390 

58-156 

Loom  

28 

360 

203 

Engine  

27-30 

410 

190-210 

Cylinder 

23-25 

525 

200-300* 

Cylinder 

26-28 

400-575 

•At  212°  F. 

Belt  Dressings  are  (1)  mixtures  of  fats,  waxes,  degras  or  tallow  with  castor 
or  fatty  oils;  (2)  vulcanized  corn  or  cottonseed  oil  thinned  with  naphtha;  (3) 
preparations  containing  wood  tar;  or  (4)  preparations  containing  rosin,  which 
is  undesirable.  Black  oils,  car  oils,  well  oil  or  reduced  oils  are  crude  oils 
from  which  the  naphthas  and  burning  oils  have  been  separated  by  distillation. 
Crank-case  oils  are  pure  mineral  oils  which  emulsify  but  little  with  water.  Mil- 
ling-machine or  soluble  cils  are  lard,  sulphonated  oils  or  mineral  oils  held  in  sus- 
pension in  water  by  soaps  or  alkalies,  as  borax  or  soda;  the  soaps  used  are  either 
ammonium,  sodium  or  potassium  with  resin,  oleic  or  sulphofatty  acids.  Rosin 
oils  are  obtained  by  distilling  or  "  running  "  rosin,  each  distillate  being  called  a 
"  run  "  and  numbered  according  to  the  times  it  has  been  distilled.  They  oxidize 
quite  rapidly  and  should  not  be  used  as  lubricants  except  as  soaps  in  lubricating 
greases.  Screw-cutting  oils  are  often  mixtures  of  27°  Be.  paraffin  and  25% 
fatty  oil,  preferably  cottonseed,  although  lard  oil  was  formerly  used.  Stainless 
oils  are  spindle  or  loom  oils  mixed  with  fatty  oils — lard  or  neatsfoot.  Transformer 
oils  should  be  either  pure  mineral  or  rosin  oils  and  as  free  as  possible  from  water, 


602 


FIXED   OILS,   FATS  AND   WAXES 


acid,  alkali  and  sulphur.  Turbine  oils  should  be  of  excellent  quality,  free  from 
acid  and  tendency  to  resinify,  and  low  in  sulphur.  Watch  oil  is  obtained  from  the 
porpoise,  dolphin,  or  blackfish,  where  it  exists  in  cavities  in  the  jaw  and  in  the 
brain  or  "  melon  "  of  the  fish.  Lubricating  greases  are  mixtures  of  soaps  of  palm 
oil,  tallow  or  rosin  oil  (with  lime  or  soda  as  bases)  with  various  oils  or  fats  such  as 
rosin,  tallow  or  mineral  oil.  The  best  are  those  made  from  tallow  by  saponifica- 
tion  with  caustic  soda.  They  may  also  contain  finely  powdered  talc  or  graphite. 
Non-fluid  oils  are  oils  or  their  greases  stiffened  with  "  oil  pulp  "  or  "dope,"  i.e., 
aluminum  oleate  or  palmitate. 

The  source,  preparation  and  uses  of  the  various  oils  and  greases  are  described 
in  Rogers  and  Aubert's  Industrial  Chemistry,  Chapters  XXII,  XXIV,  XXV 
and  XXVII. 

For  the  guidance  of  the  analyst,  the  characteristics  of  the  more  frequently 
occurring  oils  are  given,  the  usual  figures  being  given  in  italic. 

The  vegetable  oils  may  be  classified  into 

Drying.     Linseed,  C  hinese  wood,  poppyseed,  sunflower  and  menhaden. 

Semi-drying.    Corn,  cottonseed,  sesame",  rape,  black  mustard  and  horse. 

Non-drying.  Castor,  almond,  peanut,  olive,  cocoanut,  palm,  seal,  cod-liver, 
elaine,  lard,  neatsfoot,  tallow,  sperm  and  whale. 


FIXED   OILS,   FATS   AND  WAXES 


603 


CHARACTERISTICS  OF  THE  FATTY  ACIDS  FROM  SOME  OILS 


Oil. 

Refr.  Ind.  at 
60°  C. 

M.pt.    °C. 

Solidifn.    Pt. 
°C. 

Iodine 
Per  cent. 

Almond            

1   4461 

13-14 

9-11  8 

93  5-96  5 

Castor  

1.4546 

13 

3 

86-88 

Chinese  wood 

40-43  8 

31  2 

145-159  4 

Cocoanut                       ... 

1  4295 

24-27 

15-20 

8  4-9 

Codliver,  Medicinal  

— 

— 

17-18  (titer) 

164-171 

Corn  

18-21.6 

14-16 

113-125 

Cottonseed 

1  446 

34-40 

32-35 

105-112 

Elaine 

Horse                       

37.5-39  5 

33.6-37  7 

84-87 

Lard               

35 

Linseed  

1.4546 

17-24 

13-17 

179  209.8 

Menhaden  

No  figures  av 

ail.ble. 

Black  Mustard 

1  4665  at  20° 

9-17 

6-8 

108-126  5 

Neatsfoot 

28  5-29  8 

16-26  5 

62-77 

(titer) 

Olive    

1  4410 

19-31 

17-24  .  6 

86-90 

Palm 

47  7-50 

36-46 

53  3 

44 

Peanut 

1  4461 

27-35 

22-32  5 

95-103 

Poppvseed. 

1  4506 

20-21 

16  5 

139 

Rape    

1.4491 

16-22 

16-18 

99-105 

Seal 

14-33 

13-17 

186-202 

Sesam  ^ 

1  4461 

23-32 

18-26 

109-112 

Sperm                               .    .  . 

13-21 

16 

83-99 

Sunflower                      

1.4531 

17-24 

17-18 

124 

Tallow  

Whale 



14-27 

23-24 

130-132 

CALIFORNIA   CflLLEii 

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604 


FIXED  OILS,   FATS  AND  WAXES 


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caprin,  olein,  laurin, 
myristicin,  palmitin, 
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in,  palmitic  acid. 

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Similar  to  lard. 

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FIXED   OILS,   FATS   AND   WAXES 


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Composition. 

Ceryl  and  myricyl  cer- 
otate, carnaubate 
and  a  hydrocarbon. 

Hydrocarbon,  myricyl 
alcohol 

Cerotic  and  melissic 
acids,  myricin,  ceryl 
and  myricyl,  alco- 
hols, hydrocarbons. 

Ceryl  cerotate. 

Cetyl  palmitate. 

Ceryl  and  carnaubyl 
alcohols,  cholesterol, 
lanoceric,  lanopal- 
mic,  myristic,  and 
carnaubic  acids. 

Palmitin  and  palmitic 
acid. 

Palmitin. 

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FIXED   OILS,   FATS   AND   WAXES 


607 


MULTIPLYING  FACTORS  TO  REDUCE  SAYBOLT  TIMES  TO  ENGLER  NUMBERS  OR  TO 

REDWOOD  TIMES  J 


Saybolt  Times 
Seconds. 

Factor  Saybolt 
Time  to  Engler 
Number. 

Factor  Say- 
bolt  Time 
to  Redwood 
Time. 

Saybolt  Times 
Seconds. 

Factor  Saybolt 
Time  to  Engler 
Number. 

Factor  Say- 
bolt  Time 
to  Redwood 
Time. 

28 

0.0357 

0.95 

75 

0.0289 

0.86 

30 

.0352 

.95 

80 

.0286 

.86 

32 

.0346 

.94 

85 

.0284 

.86 

34 

.0342 

.94 

90 

.0282 

.85 

36 

.0337 

.94 

95 

.0280 

.85 

38 

.0334 

.93 

100 

.0279 

.85 

40 

.0330 

.93 

110 

.0276 

.85 

42 

.0327 

.92 

120 

.0274 

.84 

44 

.0323 

.92 

130 

.0272 

.84 

46 

.0320 

.91 

140 

.0271 

.84 

48 

.0317 

.91 

160 

.0269 

.84 

50 

.0314 

.90 

180 

.0268 

.84 

55 

.0308 

.90 

200 

.0267 

.84 

60 

.0302 

89 

65 

]0297 

:s8 

isoo 

0.0267 

6i84 

70 

0.0293 

0.87 

The  Engler  number  is  the  quotient  of  Engler  Time  divided  by  the  water  value 
of  the  instrument  at  20°  C.  in  seconds. 


Reagents 

The  reagents  used  in  oil  analysis  are  few  and  easily  obtained.  A  list  and 
their  method  of  preparation  is  here  given. 

Acetic  Acid,  Glacial.  Baker  and  Adamson's  C.  P.  or  Kahlbaum's  "Eisessig," 
99.5  %  pure.  The  determination  of  its  strength  should  be  made  by  titration  and 
not  by  specific  gravity,  as  the  98%  and  80%  acid  have  the  same  specific  gravity, 
1.067.  The  determination  of  the  melting-point  gives  results  equally  good  with  those 
obtained  by  titration  and  requires  less  time.2  It  is  made  after  the  manner  of  the 
"  liter  test  "  (p.  598),  the  tube  being  half  filled,  chilled  to  10  to  11°  C.,  and  further 
chilled  by  placing  the  outside  bottle  in  ice-water;  the  temperature  of  the  super-cooled 
acid  rises  to  its  melting-point,  where  il  remains  stationary  for  some  time.  The  melt- 
ing-points of  acids  of  various  strengths  are  as  follows: 

100%,,  16.75°  C.;  99.5%,  15.65°;  99%,  14.8°. 

For  Hanus's  solution  it  must  not  reduce  potassium  bichromate  and  sulphuric  acid. 

Acetic  Anhydride.  Baker  and  Adamson's  C.  P.  or  Kahlbaum's  "  Essigsaures 
Anhydrid." 

Alcohol.  Commercial  "  Cologne  Spirits."  For  the  preparation  of  alcohol  free 
from  aldehyde  for  alcoholic  potash,  cologne  spirits  are  treated  with  silver  oxide  as 
follows:  1£  grams  of  silver  nitrate  are  dissolved  in  3  cc.  of  water,  added  to  1  liter  of 
alcohol  and  thoroughly  shaken;  3  grams  of  potassium  hydrate  are  dissolved  in  15  cc. 
warm  alcohol  and,  after  cooling,  added  to  the  alcoholic  silver  nitrate  and  thoroughly 
shaken  again,  best  in  a  tall  bottle  or  cylinder.  The  silver  oxide  is  allowed  to  settle,  the 
clear  liquid  siphoned  off  and  distilled,  a  few  bits  of  pumice,  prepared  by  igniting  it  and 
immediately  quenching  under  water,  being  added  to  prevent  bumping.  Alcohol 
for  use  in  the  free  acid  determination  is  prepared  by  placing  10  to  15  grams  of  dry 
sodium  carbonate  in  the  reagent  bottle,  taking  care  to  filter  it  before  use. 

Alcohol,  Amyl.     Kahlbaum's  manufacture. 

Bromine.  The  commercial  article;  also  a  N/3  solution,  made  by  dissolving  26.6 
grams  bromine  in  1  liter  carbon  tetrachloride. 


.  Am.  Soc.  Test.  Mat.,  15,  1,  288,  1915. 
2  Mcllhiney  et  al.,  J.  Am.  Chem.  Soc.,  29,  1224,  1907. 


608  FIXED   OILS,  FATS  AND  WAXES 

Calcium  Chloride.     The  dry  and  also  the  crystallized  salt. 
Calcium  Sulphate.     Plaster  of  Paris. 

Carbon  Tetrachloride.  Baker  and  Adamson's  C.  P.  or  Kahlbaum's  "  Tetrachlor- 
kohlenstoff." 

Chloroform.     Squibb's,  U.  S.  P. 

Copper.     Copper  turnings  or  clippings,  used  for  the  generation  of  nitric  oxide. 

Copper  Wire.    Cut  in  pieces  of  0.3  to  0.5  gram. 

Ether.     Squibb's,  U.  S.  P. 

Gasoline.    Gasoline,  86°  Baume*. 

Hydrochloric  Acid,  C.  P.— Specific  gravity  1.2.  For  N/2  HC1  dilute  39  cc.  of  the 
above  acid  to  1  liter  and  standardize. 

Iodine  Solution.  Fifty  grams  of  iodine  to  1  liter  of  alcohol.  For  Hanus's  solution 
dissolve  by  warming  13.2  grams  iodine  in  1  liter  glacial  acetic  acid;  cool  and  add  3  cc. 
of  bromine. 

Lead  Acetate.    One  hundred  grams  of  the  salt  to  1  liter. 

Lacmoid.     Three  grams  per  liter  of  dilute  alcohol. 

Lacmoid  Paper.     Unsized  paper  dipped  in  above  solution. 

Litmus  Paper. 

Mercuric  Chloride.     Sixty  grams  of  the  salt  to  1  liter  of  alcohol. 

flitric  Acid.     Specific  gravity  1.34. 

Phenolphthalein.     One  gram  of  the  substance  to  500  cc.  of  alcohol. 

M eta-Phosphoric  Acid.  A  saturated  solution  of  the  commercial  "  stick  phosphoric 
acid  "  in  absolute  alcohol. 

Potassium  Bichromate.  Dissolve  3.8633  grams  of  the  C.  P.  salt  in  1  liter  of  water; 
1  cc.  is  equivalent  to  0.01  gram  of  iodine.  The  solution  should  be  tested  against  iron 
wire  containing  a  known  percentage  of  iron. 

Potassium  Hydrate.  N/2:  Dissolve  30  grams  of  "  potash  by  alcohol  "  in  1  liter  of 
alcohol.  N/6:  Dissolve  10  grams  of  "  potash  by  alcohol "  in  1  liter  of  water  and 
dilute  to  proper  strength.  The  solution  should  be  protected  by  "  stick  potash  "  from 
the  carbon  dioxide  in  the  air.  Ten  per  cent.:  Dissolve  100  grams  of  "  stick  potash  " 
in  1100  cc.  of  alcohol.  ^  ^ 

Potassium  lodate.    A  2%  solution. 

Potassium  Iodide.  One  hundred  grams  of  the  commercial  salt  are  dissolved  in  1 
liter  of  water.  This  should  be  free  from  iodate,  shown  by  yielding  no  coloration  when 
acidified  with  strong  HC1. 

Silver  Nitrate.    Thirty  grams  Jo  1  liter+0.4  cc.  HN03. 

Sodium.  *~  -• 

Sodium  Chloride.    Ordinary  "  coarse  fine  "  salt  for  freezing  mixtures. 

Sodium  Hydrate.    36°  Baum6.     Dissolve  300  grams  of  caustic  soda  in  1  liter  of  water. 

Sodium  Nitroprusside.    The  commercial  salt. 

Sodium  Thiosulphate.  N/10:  Dissolve  26  grams  of  "sodium  hyposulphite"  in 
1  liter  of  water.  See  page  204. 

Starch  Solution.  Rub  up  in  a  mortar  1  gram  of  potato  starch,  with  10  to  15  cc.  of 
water,  pour  this  into  200  cc.  of  water  which  is  boiling  actively,  and  continue  the 
boiling  for  a  few  minutes. 

Sugar.     Ordinarily  granulated  sugar. 

Sulphur.     A  1.5%  solution  in  carbon  bisulphide. 

Sulphuric  Acid.  C.  P.     This  should  be  at  least  99.5%  pure,  and  its  strength  be 
determined  by  titration,  as  100%  and  94.3%  acid  have  the  same  specific  gravity. 
Dilute.    One  part  acid  to  ten  parts  water.  v 

Nitrosulphuric  Add,  for  the  Elaidin  Test.  }A  liter  of  sulphuric  acid  of  46°  Baume* 
(1.47  specific  gravity)  is  prepared  by  diluting  560  cc.  commercial  sulphuric  acid  to 
1  liter;  a  few  drops  of  nitric  acid  are  added  and  nitric  oxide  (generated  from  copper 
and  nitric  acid)  passed  in  until  it  is  saturated.  The  acid  is  then  cooled  in  ice-water 
and  the  gas  passed  in  until  it  is  saturated  at  0°  C.^  This  is  called  Roth's  liquid. 

The  author  wishes  to  acknowledge  his  indebtedness  to  Mr.  Thomas  T.  Gray 
for  his  careful  review  of  this  chapter.  Mr.  Gray's  broad  experience  in  petroleum 
products  as  Chief  Chemist  of  Tidewater  Oil  Company,  makes  his  criticism  and 
suggestions  of  special  value. 

*  Richmond,  J.  Soc.  Chem.  Ind.,  9,  479, 1890. 


ANALYSIS  OF  PAINTS 

HENRY  A.  GARDNER1  AND  JOHN  A.  ScnAEFPER2 

In  reporting  the  results  of  an  examination  of  a  paint,  it  is  advisable  to  give 
all  the  analytical  data  as  well  as  a  re*sume*  showing  the  probable  composition  of 
the  paint.  This  is  shown  in  the  following  example: 

RESULTS  OP  ANALYSIS 

Total  Pigments  or  Solids 60% 

Total  Vehicle  or  Liquids 40 

Analysis  of  Pigment  Portion 

Lead  Oxide  (PbO) 37.47% 

Zinc  Oxide  (ZnO) 44.50 

Alumina,  iron,  lime 2 . 90 

Magnesia  (MgO) 1 . 90 

Silica  (SiO2) 4.63 

Carbon  Dioxide  (CO2) 2.50 

Sulphuric  Anhydride  (SO3) 5.02 

Water  (combined) .73 

99.15% 
Analysis  of  Vehicle  Portion 

Vehicle  contained  20%  volatile  matter. 

Volatile  matter  consisted  of  equal  parts  of  turpentine  and  mineral  spirits. 

Non-volatile  matter  had : 

Iodine  Number 175 

Acid  Number 2.4 

Saponification  Number 188 

and  contained  .02%  ash  consisting  of  lead  and  manganese  oxides. 

Probable  Composition  of  Paint. 

Pigment 60% 

Liquid 40 

Pigment 

Basic  Carbonate— White  Lead 22% 

Basic  Sulphate— White  Lead 25 

Zinc  Oxide 43 

Asbestine 10 

100% 
Liquid 

Raw  Linseed  Oil 80% 

Mineral  Spirits 10 

Turpentine  and  Drier 10 

100% 

1  Assistant  Director,  The  Institute  of  Industrial  Research,  Washington,  D.  fi. 

2  Chief  Chemist,  The  Eagle-Picher  Lead  Co.,  Joplin,  Mo. 

609 


610  PAINT  AND  PAINT  PIGMENTS 


ANALYSIS  OF   PAINT  VEHICLES 

Composition  of  Liquid  Part.  The  vehicle  or  liquid  portion  of  paints  may  coi>- 
tain  various  fixed  animal,  vegetable  or  mineral  oils,  oleo-resinous  varnishes,  tur- 
pentine, mineral  distillates,  benzol  and  driers. 

It  is  always  advisable  to  determine  the  total  percentage  of  liquids  in  a  paint. 
The  container  should  be  thoroughly  shaken  so  that  the  contents  will  be  uniform 
throughout.  A  portion  of  4  or  5  ounces  may  then  be  removed  and  placed 
in  a  screw-cap  bottle.  The  original  can  of  paint  should  then  be  set  aside  so  that 
settling  of  the  pigments  will  take  place.  Unless  the  paint  is  in  paste  form,  this 
will  usually  be  accomplished  in  twenty-four  hours.  A  portion  of  the  clear  liquid 
floating  over  the  pigments  may  then  be  removed  and  directly  examined  as  out- 
lined under  Separation  of  Vehicle  Components. 

Percentage  of  Liquid  by  Ignition  Method.  The  percentage  of  vehicle  in  the 
uniform  sample  of  paint  previously  obtained  may  be  found  by  placing  a  weighed 
portion  in  a  porcelain  crucible  and  slowly  igniting  it  to  burn  off  the  organic  con- 
stituents. By  carefully  regulating  the  heat,  the  oil  and  volatile  thinners  will  be 
slowly  burned  off,  leaving  the  pigment  behind,  which  may  then  be  weighed,  cal- 
culating the  vehicle  by  difference.  This  method  is  a  rapid  one  and  works  well 
with  some  pigments.  When  pigments  are  present  which  show  an  appreciable  loss 
on  ignition,  or  blacks  or  blues,  this  method  is  not  to  be  relied  upon. 

Percentage  of  Liquid  by  Extraction  Methods.  Another  good  method  of  sepa- 
rating the  vehicle  from  a  paint  is  to  place  a  portion  in  a  large  tube,  adding  a  con- 
siderable quantity  of  benzol,  petroleum  ether,  or  that  portion  of  gasoline  distilling 
below  120°  C.,  subsequently  centrifuging.  Pigments  which  settle  slowly  are 
thrown  down  very  rapidly  by  this  method.  The  process  is  repeated  three  or  four 
times  in  order  thoroughly  to  free  the  pigment  from  oil.  After  drying,  the  pigment 
is  weighed  and  the  percentage  of  vehicle  determined  by  difference.  In  case  a 
centrifuge  is  not  available,  the  vehicle  of  many  paints  may  be  separated  by  simply 
shaking  a  portion  of  the  paint  in  a  long  test-tube  with  benzol,  allowing  the  pigment 
to  settle,  repeating  the  extraction  until  the  oil  is  thoroughly  removed. 

Some  operators  have  from  time  to  time  used  a  Soxhlet  extractor  for  the  deter- 
mination of  the  vehicle  of  a  paint.  This  method  is  rather  slow  and  does  not 
always  give  satisfactory  results. 

It  must  be  remembered  that  no  method  of  extraction  of  the  oil  from  a  paint 
will  give  absolute  results.  The  last  traces  of  oil  cannot  be  removed  from  the 
pigment,  which  is  probably  due  to  the  fact  that  many  pigments  such  as  lead  and 
zinc  react  with  the  oil,  producing  small  quantities  of  insoluble  soaps  which  are 
not  completely  dissolved  by  the  solvent. 

In  the  extraction  of  paints,  the  choice  of  a  solvent  is  important.  When  benzol 
(90°)  is  not  available,  it  may  be  replaced  by  gasoline  that  has  been  redistilled, 
using  the  light  fraction  coming  over  below  120°  C.  This  cannot  be  used,  however, 
when  varnish  resins  other  than  rosin  are  present,  as  they  are  insoluble  therein. 

There  are  some  pigments  which  by  reason  of  their  low  specific  gravity,  col- 
loidal nature  or  partial  solubility  can  never  be  completely  separated  from  oil, 
either  by  settling,  centrifuging  or  extraction.  Of  these  the  most  commonly 
met  with  are  lampblack  and  other  forms  of  carbon,  zinc  oxide  and  Prussian  blue. 
Colloidal  pigments  such  as  zinc  oxide  are  very  troublesome  in  this  respect.  When 
these  pigments,  however,  are  present  in  a  paint  in  considerable  percentage,  the 


PAINT  AND  PAINT  PIGMENTS  611 

difficulty  of  their  separation  may  be  avoided  by  adding  to  the  paint  three  or  four 
times  its  volume  of  fuller's  earth,  diluting  the  mixture  in  a  large  test-tube  with 
gasoline  or  petroleum  ether  and  either  centrifuging  or  placing  in  a  rack  to  settle. 
The  fuller's  earth  carries  down  the  colloidal  pigments  and  the  separation  is  sharp 
and  easy.  This  method,  of  course,  is  simply  used  to  extract  the  vehicle  present. 
The  pigment  resulting  from  the  separation  cannot  be  used  for  analysis  on  account 
of  admixture  with  the  fuller's  earth. 

In  some  cases  the  pigments  in  paste  colors  made  of  lampblack  and  Prussian 
blue  cannot  be  separated  from  the  vehicle  portion.  The  amount  of  Prussian  blue 
present,  however,  may  be  determined  by  making  a  Kjeldahl-Gunning  determina- 
tion on  a  portion  of  the  entire  paint,  multiplying  the  nitrogen  found  by  4.4.  For 
the  determination  of  the  lampblack  present,  a  portion  of  the  entire  paint  may  be 
boiled  with  an  excess  of  alcoholic  potash  until  all  of  the  oil  is  saponified.  The 
mixture  is  then  decanted  through  a  filter  and  washed,  first  with  hot  alcohol  and 
then  with  hot  water.  This  affords  a  very  good  separation  of  the  vehicle  from  the 
pigment  of  such  paints.  By  this  method,  the  Prussian  blue  which  may  be  present 
is  partially  destroyed,  the  iron  content  remaining  admixed  with  the  black  pig- 
ment on  the  filter. 

Separation  of  Vehicle  Components.  Whenever  possible,  it  is  advisable  to 
determine  the  constituents  of  the  vehicle  upon  that  sample  that  has  been  removed 
from  the  top  of  the  settled  can  of  paint.  A  weighed  portion  of  this  vehicle  may  be 
placed  in  a  tared  flask  and  attached  to  a  Liebig  condenser.  Heating  to  180°  C. 
or  lower  will  drive  off  nearly  all  the  volatile  constituents.  The  composition  of  the 
distillate  may  be  determined  by  the  methods  given  under  the  Examination  of  Tur- 
pentine. A  portion  of  the  residue  in  the  flask,  which  consists  of  oil,  driers,  gums, 
etc.,  may  be  transferred  to  a  crucible  and  ignited.  The  residue  may  then  be 
weighed  and  calculated  to  ash.  The  ash  should  be  analyzed  for  lead,  manganese 
and  other  driers. 

Another  portion  of  the  original  vehicle  may  be  evaporated  in  an  atmosphere 
of  C02  (prevents  oxidation)  to  remove  the  volatile  constituents.  A  portion  of  the 
oil  residue  may  then  be  examined  for  iodine  number  and  other  constants.  In  some 
instances  it  would  be  advisable  to  make  a  saponification  and  extraction  of  the 
fatty  acids  from  this  residue,  determining  the  iodine  number  on  the  fatty  acids. 

Water.  For  a  direct  determination  of  the  percentage  of  water  in  a  paint,  the 
analyst  may  place  a  weighed  quantity  (approximately  100  grams)  of  the  paint  in 
a  metal  still,  mixing  it  with  an  equal  quantity  of  sand.  Distillation  will  drive  off 
the  water  and  other  volatile  constituents  which  will  separate  into  two  layers  in  the 
graduate. 

Direct  Distillation  for  Volatiles.  For  a  direct  determination  of  the  volatile 
constituents  in  a  paint,  a  sample  may  be  distilled  in  vacuo.  This  is  easily  managed 
wherever  a  vacuum  pump  is  available  and  avoids  the  necessity  of  overheating  the 
oil.  When  distilling  by  this  method,  a  sample  of  the  clear  vehicle  from  a  settled 
paint,  in  order  to  obtain  the  fixed  oils  for  analysis,  it  should  not  be  heated  above 
150°  C.  and  neither  should  the  solvent  be  volatilized  in  such  a  way  as  to  allow  the 
oil  to  be  in  contact  with  air,  as  it  will  oxidize  rapidly  while  warm  and  its  iodine 
number  be  very  much  lowered.  The  volatile  may  also  be  separated  by  steam  dis- 
tillation. 

Detection  of  Resinates.  To  determine  whether  the  drier  in  a  paint  is  of  the 
resinate  type  or  linoleate  type,  a  few  drops  of  the  oil  vehicle  may  be  mixed  on  a  por- 
celain plate  with  one  or  two  drops  of  acetic  anhydride,  subsequently  adding  a- 


612  PAINT   AND   PAINT   PIGMENTS 

drop  of  sulphuric  acid.  Upon  the  addition  of  the  sulphuric  acid,  a  flash  of  purple 
color,  turning  to  dark  brown,  will  be  shown  where  rosin  is  present.  If  rosin  should 
be  present  in  the  vehicle  to  a  considerable  extent,  the  oil  will  have  a  very  high  acid 
number.  The  approximate  percentage  of  rosin  present  may  be  determined  by 
shaking  a  portion  of  the  vehicle  with  95%  alcohol  in  a  separatory  funnel,  sub- 
sequently separating  the  alcoholic  extract,  evaporating  and  weighing  the  residue. 

Detection  of  Various  Oils.  Chinese  wood  oil  may  be  detected  in  the  vehicle 
by  mixing  the  oil  with  an  equal  volume  of  a  saturated  solution  of  iodine  in  petro- 
leum ether,  allowing  the  mixture  to  stand  in  direct  sunlight.  Under  these  condi- 
tions, a  peculiar,  insoluble,  spongy  polymer  of  one  of  the  fatty  acids  of  Chinese 
wood  oil  is  shown.  Fish  oil  can  usually  be  detected  by  its  odor  and  the  dark  red 
color  daring  saponification.  The  presence  of  soya  bean  and  other  vegetable  oils 
is  in  some  cases  difficult  to  detect.  The  iodine  numbers  of  these  oils,  however,  are 
all  lower  than  that  of  linseed  oil.  It  must  be  remembered,  however,  that  the 
iodine  number  of  boiled  linseed  oil  is  lower  than  that  of  raw  oil  and  that  the  iodine 
number  of  oils  extracted  from  many  paints  is  usually  lower  than  shown  by  the 
original  oil.  In  the  presence  of  considerable  quantities  of  drier,  it  is  always 
advisable  to  extract  the  fatty  acids  from  oil  and  make  the  iodine  determination 
upon  them. 

The  distillate  from  the  paint  vehicle  may  consist  of  turpentine,  mineral  dis- 
tillates, benzol  and  similar  solvents.  The  presence  of  benzol  is  readily  detected 
by  adding  a  few  drops  of  the  distillate  to  a  small  quantity  of  a  mixture  of  con- 
centrated nitric  and  sulphuric  acids.  Upon  heating  this  mixture,  the  character- 
istic odor  of  nitro-benzol  will  be  recognized  if  benzol  is  present.  Mineral  dis- 
tillates from  petroleum  are  easily  detected  by  the  polymerization  method  given 
under  the  Examination  of  Turpentine. 


ANALYSIS  OF  PAINT  OILS 

Although  linseed  oil  is  used  to  the  greatest  extent  in  paints,  some  other  oils 
find  use  in  the  manufacture  of  special  paints.  The  following  have  been  used 
for  this  purpose:  soya  bean,  perilla,  corn,  cottonseed,  sunflower,  lumbang,  and 
similar  vegetable  oils;  menhaden,  herring,  and  similar  marine  animal  oils  of  rela- 
tively high  iodine  number.  All  of  the  above  named  oils  may  be  analyzed  by 
applying  the  test  for  specific  gravity,  acid  number,  saponification  number,  un- 
saponifiable  matter,  and  refractive  index,  as  outlined  for  the  analysis  of  Chinese 
wood  oil.  The  iodine  numbers  of  these  oils  are,  however,  better  determined  with 
Hanus  solution,  according  to  the  following  method : 

Iodine  Number.  Weigh  in  a  small  glass  capsule  from  0.2  to  0.3  gram  of  oil, 
transfer  to  a  500-cc.  bottle  having  a  well-ground  stopper,  dissolve  the  oil  in  10  cc. 
of  chloroform  and  add  30  cc.  of  Hanus  solution;  let  it  stand  with  occasional  shak- 
ing for  one  hour,  add  Ifrcc.  of  a  10  per  cent  solution  of  potassium  iodide  and  150 
cc.  of  water,  and  titrate  with  standard  sodium  thiosulphate,  using  starch  as  indi- 
cator. Blanks  must  be  run  each  time.  From  the  difference  between  the  amounts 
of  sodium  thiosulphate  required  by  the  blanks  and  the  determination,  calculate 
the  iodine  number  (centigrams  of  iodine  to  1  gram  of  oil).  The  iodine  number  of 
raw  linseed  oil  varies  from  175  to  193.  Make  the  Hanus  solution  by  dissolving 
13.2  grams  of  iodine  in  1000  cc.  of  glacial  acetic  acid  which  will  not  reduce  chromic 
acid,  and  adding  3  cc.  of  bromine. 


PAINT  AND  PAINT  PIGMENTS  613 


Analysis  of  Chinese  Wood  Oil  (Tung  Oil) 

4 

The  analysis  of  Chinese  wood  oil  requires  the  application  of  several  tests  not 
used  for  the  examination  of  other  oils.  There  is  presented  herewith  a  complete 
outline  for  determining  not  only  the  regular  constants  of  oils,  but  the  additional 
tests  that  have  been  adopted  for  the  identification  of  pure  tung  oil.  These  tests 
constitute  the  recommended  methods  of  Sub-Committee  III  of  Committee  D-l 
of  the  American  Society  for  Testing  Materials,  of  which  one  of  the  writers  is 
chairman. 

Specific  Gravity.  Use  a  pyknometer  accurately  standardized  and  having  a 
capacity  of  at  least  25  cc.,  or  any  other  equally  accurate  method,  making  the 
test  at  15°.5  C.,  water  being  1  at  15°.5  C. 

Acid  Number.  Weigh  10  grams  of  oil  in  a  200-cc.  Erlenmeyer  flask,  add 
50  cc.  of  neutral  alcohol,  connect  with  a  reflux  air  condenser  (or  place  small 
funnel  in  neck  of  flask),  and  heat  on  a  steam  bath  for  one-half  hour.  Remove 
from  the  bath,  cool,  add  phenolphthalein,  and  titrate  the  free  acid  with  N/5 
sodium  hydroxide.  Calculate  as  the  acid  number  (milligrams  of  potassium 
hydroxide  to  1  gram  oil) . 

Saponification  Number.  Weigh  from  2  to  3  grams  of  oil  in  a  200-cc.  Erlen- 
meyer flask,  add  30  cc.  of  a  N/2  alcoholic  solution  of  potassium  hydroxide,  connect 
with  a  reflux  condenser,  heat  on  a  steam  bath  for  one  hour,  then  titrate  with  N/2 
sulphuric  acid,  using  phenolphthalein  as  indicator.  Always  run  two  blanks  with 
the  alcoholic  potash.  From  the  difference  between  the  number  of  cc.  of  acid 
required  by  the  blanks  and  the  determinations,  calculate  the  saponification 
number  (milligrams  of  potassium  hydroxide  to  1  gram  of  oil). 

Unsaponifiable  Matter.  To  25  grams  of  oil  add  15  cc.  of  an  aqueous  solution 
of  KOH  (200  grams  of  KOH  dissolved  in  water  and  made  up  to  300  cc.)  and  35 
cc.  of  95%  alcohol.  Connect  with  a  reflux  condenser  and  heat  on  the  water 
bath  for  one  hour  with  occasional  shaking.  Transfer  to  a  separatory  funnel  con- 
taining a  little  water  and  wash  out  flask  with  water,  using  in  all  125  cc.  Cool, 
add  200  cc.  of  ether  and  shake  vigorously  for  one  minute.  In  a  few  minutes  the 
ether  solution  will  separate  perfectly  clear.  Draw  off  the  soap  solution  into 
another  separatory  funnel.  Shake  the  soap  solution  with  three  100-cc.  portions 
of  ether.  Unite  all  the  ether  portions  and  wash  with  three  30-cc.  portions  of 
water.  Filter  the  ether  solution  (small  portions  at  a  time)  into  a  tared  flask, 
distill  off  the  ether  and  dry  flask  and  contents  to  constant  weight  at  95  to  100°  C. 
in  a  steam  oven.  Report  the  percentage  of  unsaponifiable  matter. 

Refractive  Index.  Use  a  properly  standardized  Abbe*  refractometer  at  25°  C. 
or  any  other  equally  accurate  instrument. 

Iodine  Number  (Hiibl).  Place  a  small  quantity  of  oil  into  a  small  weighing 
bottle  or  beaker.  Weigh  carefully.  Transfer  by  dropping  from  0.2  to  0.3  gram 
to  a  500-cc.  bottle  having  a  well-ground  stopper,  or  a  specially  flanged  neck, 
iodine-test  Erlenmeyer  flask.  Reweigh  the  weighing  bottle  or  beaker  to  deter- 
mine the  amount  of  oil  used  in  the  test.  Then  dissolve  the  oil  in  10  cc.  of  chloro- 
form and  add  an  amount  of  Hiibl  solution  containing  twice  the  amount  of  iodine 
that  will  be  absorbed  by  the  oil.  Stopper  the  flask,  shake  well,  and  place  in  a 
dark  closet  for  eighteen  hours.  Add  10  cc.  of  a  10%  solution  of  potassium 
iodide  and  100  cc.  of  distilled  water.  Titrate  with  N/10  sodium  thiosulphate,  using 
starch  as  an  indicator.  Blank  tests  must  be  made.  From  the  difference  between 


614 


PAINT  AND  PAINT  PIGMENTS 


the  amounts  of  sodium  thiosulphate  required  by  the  blanks  and  the  determination, 
calculate  the  iodine  number  (centigrams  of  iodine  to  1  gram  of  oil). 

On  account  of  the  fact  that  Hubl  solution  after  preparation  is  apt  to  deteri- 
orate in  strength,  it  is  considered  advisable  to  have  prepared  the  two  component 
parts  of  Hubl  solution,  namely,  a  solution  of  mercuric  chloride  in  alcohol  and  a 
solution  of  iodine  in  alcohol,  of  the  proper  strength,  as  outlined  in  text-books. 
The  proper  amounts  of  these  solutions  may  be  mixed  on  the  day  of  use. 

Heating  Test  (Browne's  Method).  Test-tubes  for  containing  the  oil  should 
be  16  cm.  by  15  mm.,  with  a  mark  near  the  bottom  to  indicate  5  cc.,  and 
closed,  by  a  cork  so  perforated  that  a  glass  rod  3  mm.  in  diameter  can  move 
freely. 

Fill  a  copper  beaker  (height  12  cm.;  internal  diameter,  6  cm.)  with  cotton- 
seed oil  to  a  height  of  7.5  cm.  Place  a  thermometer  so  as  to  be  1.5  cm.  from 
the  bottom  of  the  bath. 

Use  a  nitrogen-filled,  immersed-stem  chemical  thermometer,  engraved  stem; 
total  length  4  to  4|  ins.;  graduated  from  210  to  310°  C.  in  2°  intervals;  the  length 
between  210  and  310°  C.  not  less  than  2£  ins.  If  preferred,  use  emergent-stem 
thermometer  30  cm.  long,  with  graduations  from  100  to  400°  C.,  making  cor- 
rection for  emergent  stem  according  to  the  method  outlined  in  Stem  Correction 
Sheet  No.  44  of  the  U.  S.  Bureau  of  Standards. 

When  the  bath  temperature  is  293°  C.  (560°  F.)  and  very  slowly  rising  at 
this  point,  place  the  tube  containing  5  cc.  of  the  oil  to  be  tested  so  that  its  bottom 
is  level  with  the  lowest  part  of  the  bulb  of  the  thermometer.  Note  the  time, 
remove  the  source  of  heat  for  about  forty-five  seconds  and  then  reapply.  Before 
two  minutes  have  elapsed  the  temperature  of  the  bath  will  have  fallen  to  282°  C. 
(540°  F.),  at  which  point  it  should  be  kept  as  steady  as  possible.  When  the  wood 
oil  has  been  in  the  bath  about  nine  minutes,  raise  the  glass  rod  at  intervals  of 
one-half  minute,  and  when  the  rod  is  firmly  set  note  the  time.  As  setting  or  jelly- 
ing takes  place  within  a  few  seconds  of  fluidity,  a  good  end-determination  is 
afforded.  Remove  the  specimen  at  once,  heat  the  bath  again  to  293°  C.,  and 
repeat  the  experiment  with  another  portion  of  the  sample. 

No  stirrer  is  used  in  the  bath.  A  screen  around  the  bath  enables  the  tem- 
perature to  be  more  easily  reached.  When  the  cotton-seed  oil  has  become  tarry 
and  viscid,  it  should  be  renewed;  otherwise  heating  may  be  irregular. 

Iodine  Jelly  Test.  In  a  wide-necked  200-cc.  Erlenmeyer  flask,  place  2.5 
grams  (weight  correct  to  1  milligram)  of  the  oil.  Add  10  cc.  of  chloroform  from 
a  pipette  and  stopper  the  flask  immediately.  Caremlly  insert  a  small  glass  vial 
into  the  flask  so  that  the  vial  stands  upright.  Into  the  vial  from  a  pipette  run 
10  cc.  of  a  solution  of  iodine  in  chloroform,  containing  0.035  to  0.036  gram  of 
iodine  per  cc.  Place  the  flask  in  a  bath  containing  water  at  25  to  26°  C.  and 
allow  it  to  stand  there  for  a  few  minutes.  Keep  the  flask  stoppered,  except  when  it 
is  necessary  to  remove  stopper  to  insert  the  vial  and  to  add  the  iodine  solution. 
Tilt  and  rotate  the  flask  so  that  the  vial  is  upset  and  the  contents  of  the  flask 
are  thoroughly  mixed,  at  the  same  time  starting  a  stop-watch.  Keep  the  flask 
in  the  bath  at  25  to  26°  C.  and  at  the  end  of  every  quarter  minute  tilt  the  flask 
towards  a  horizontal  position.  Note  the  time  required  for  the  formation  of  a 
jelly  that  does  not  flow,  but  sticks  to  the  bottom  of  the  flask  or  slides  as  a  mass. 
Record  time  in  minutes  and  quarters  thereof.  Pure  Chinese  wood  oil  should 
require  2f  to  3j  minutes  for  the  formation  of  the  jelly.  If  the  temperature  of  the 
laboratory  is  more  than  2  or  3°  C.  above  or  below  25°  C.,  place  the  flask  contain- 


PAINT   AND   PAINT   PIGMENTS  615 

ing  the  iodine  solution  in  the  bath  and  allow  it  to  remain  there  for  several  minutes 
before  pipetting  out  the  10  cc.  for  the  test. 

A  convenient  procedure  for  preparing  the  iodine  solution  is  as  follows: 
Treat  an  excess  of  iodine  with  warm  chloroform  and  after  shaking  for  a  few 
minutes  cool  the  contents  to  about  20°  C.  and  filter  through  glass  wool.  Pipette 
10  cc.  of  the  solution  into  a  flask  containing  10  cc.  of  10%  potassium-iodide 
solution  and  titrate  with  0.1  normal  sodium-thiosulphate  solution.  Calculate 
the  iodine  content  and  dilute  with  chloroform  so  as  to  obtain  an  iodine  content 
of  0.035  to  0.036  gram  per  cc.  After  dilution,  titrate  again  against  the  thio- 
sulphate  to  be  sure  that  the  solution  is  of  required  strength. 

All  the  details  of  the  above  method  must  be  followed  exactly. 

The  chloroform  used  to  dissolve  the  oil  and  to  prepare  the  iodine  solution  must 
conform  to  the  requirements  of  the  U.  S.  Pharmacopoeia  and  must  have  a  specific 
gravity  at  25/25°  C.  of  not  more  than  1.481  and  not  less  than  1.480.  The  proper 
density  can  be  obtained  by  washing  with  water  if  the  specific  gravity  is  too  low, 
or  by  adding  95%  ethyl  alcohol  if  too  high. 

Standards  for  Chinese  Wood  Oil,  A.  S.  T.  M. 

Raw  Chinese  wood  oil  should  conform  to  the  following  requirements : 

Maximum.  Minimum. 

Specific  gravity  at  ^HM?  C 0.943  0.939 

JLO    .O 

Acid  number 6 

Saponification  number 195                      190 

Unsaponifiable  matter,  per  cent 0 . 75 

Refractive  index  at  25°  C 1 .520                  1 .515 

Iodine  number  (Htibl  eighteen  hours) 165 

Heating  test  (Browne's  method),  minutes. .  ...  12 

Iodine  jelly  test,  minutes 4 

Constants  of  Various  Oils.  The  constants  exhibited  by  some  of  the  semi- 
drying  and  drying  oils  that  have  been  used  by  one  of  the  writers  (Gardner)  in 
making  paints  and  paint  tests  are  shown  below.  There  are  also  given  here- 
with the  standards  for  raw  and  boil  d  linseed  oil  pressed  from  North  American 
seed.  Similar  oils  expressed  from  South  American  seed  will  generally  show  like 
constants,  except  for  the  iodine  number,  which  will  generally  range  from  170 
to  180. 


616 


PAINT   AND   PAINT   PIGMENTS 

CONSTANTS  OP  VARIOUS  OILS 


Sp.  Gr. 

Iodine  No. 

Sapon.  No. 

Acid  No. 

Refrac. 
Index. 

Raw  Linseed  Oil                 .... 

931 

186 

188 

2  0 

4867 

Soya  Bean  Oil 

924 

129 

189 

2  3 

4813 

Menhaden  Oil.     •  .                     . 

932 

158 

187 

3  9 

4850 

Raw  Tung  Oil          .             ... 

944 

166 

183 

3  8 

5050 

Perilla  Oil.  

.94 

200 

188 

2  0 

.4874 

Perilla  Special  

.94 

192 

189 

3  2 

.4978 

Heavy  Bodied  Linseed  Oil. 

968 

133 

189 

2  8 

4966 

Lithographic  Linseed  Oil 

97 

102 

199 

2  7 

4978 

Whale  Oil  

.924 

148 

191 

9  2 

1.4820 

Boiled  Linseed  Oil.      . 

941 

172 

187 

2  7 

1  4895 

(Linoleate  Drier) 
Corn  Oil  

.921 

124.8 

190  1 

4  1 

1.4800 

Cottonseed  Oil  

920 

111.7 

194  3 

0  9 

1.4781 

Rosin  Oil  

964 

68.9 

35  5 

32  4 

Treated  Tung  Oil  l  

882 

56.4 

101  3 

7  7 

1.4764 

Lumbang  Oil  

927 

152 

189 

1  0 

1.4789 

Sunflower  Oil  

924 

124  6 

189  3 

7  5 

1.4796 

927 

149  4 

191  1 

3  9 

1.4822 

Shark  Oil  

910 

132  8 

158  9 

5  2 

1.4815 

Sardine  Oil   .         

919 

134  6 

177  3 

10  4 

1.4800 

Petroleum  Mixing  Oil  

851 

28  2 

52  9 

1  1 

1.4773 

Boiled  Linseed  Oil  

936 

184  2 

187  6 

7  3 

1.4895 

(Resinate  Drier) 
Peanut  Oil  

932 

102  2 

188  0 

2  2 

1  4790 

Boiled  linseed  oil  from  North  American  seed  should  conform  to  the  following 
requirements,  A.  S.  T.  M.: 

Maximum. 


Specific  gravity  at  j|^  C 0.945 

Acid  number 8 

Saponification  number 195 

Unsaponifiable  matter,  per  cent 1.5 

Refractive  index  at  25°  C 1 . 484 

Iodine  number  (Hanus) 

Ash,  per  cent 0.7 

Manganese,  per  cent 

Calcium,  per  cent 0.3 

Lead,  per  cent. * 


Minimum. 

0.937 

189 

1.479 
178 
0.2 
0.03 

0.1 


Raw  linseed  oil  from  North  American  seed  should  conform  to  the  following 
requirements,  A.  S.  T.  M.: 


Maximum. 

Specific  gravity  at  J^f  C 0.936 

lo  .o 


or 


25< 


Specific  gravity  at  ^  C 0 .931 

Acid  number 6.00 

Saponifiation  number 195 

Unsaponifiable  matter,  per  cent 1 . 50 

Refractive  index  at  25°  C 1 .4805 

Iodine  number  (Hanus) 


Minimum. 

0.932 

0.927 

189" 

"i 
180 


1  Contained  30%  volatile  matter,  largely  high  boiling-point  petroleum  spirits. 


PAINT   AND   PAINT  PIGMENTS  617 

Examination  of  Turpentine 

RECOMMENDED  METHODS  OF  THE  A.  S.  T.  M. 

Color.  Fill  a  200-mm.,  perfectly  flat-bottom  colorimetric  tube  graduated  in 
millimeters  to  a  depth  of  from  40  to  50  mm.  with  the  turpentine  to  be  examined . 
Place  the  tube  in  a  colorimeter  and  place  on  or  under  it  a  No.  2  yellow  Lovibond 
glass.  Over  or  under  a  second  graduated  tube  in  the  colorimeter,  place  a  No.  1 
yellow  Lovibond  glass  and  run  in  the  same  turpentine  until  the  color  matches 
as  nearly  as  possible  the  color  in  the  first  tube.  Read  the  difference  in  depth 
of  the  turpentine  in  the  two  tubes.  If  this  difference  is  50  mm.  or  more  the 
turpentine  is  "  Standard  "  or  better. 

Specific  Gravity.  Determine  specific  gravity  at  any  convenient  temperature 
with  a  plummet,  the  displacement  of  which  has  been  accurately  determined  for 
that  temperature,  or  by  an  equally  accurate  method,  using  the  factor  0.00082 
for  each  degree  centigrade  that  the  temperature  of  determination  differs  from 
15°.5  C. 

Refractive  Index.  Determine  refractive  index  at  any  convenient  tempera- 
ture with  an  accurate  instrument,  and  calculate  the  results  to  15°.5  C.,  using  the 
factor  0.00045  for  each  degree  that  the  temperature  of  determination  differs  from 
15°.5  C. 

Distillation.  Use  an  ordinary  Engler  flask  and  condenser,1  and  heat  the 
flask  by  placing  it  in  a  glycerine  or  oil  bath  of  the  general  type  described  in 
Bulletin  No.  135,  Bureau  of  Chemistry.  Fit  the  flask  with  a  thermometer  reading 
from  145  to  200°  C.  in  such  a  way  that  the  mercury  bulb  shall  be  opposite  the 
side  tube  of  the  flask  and  the  175°  mark  below  the  cork.  Place  100  cc.  of  the 
turpentine  to  be  examined  in  the  flask,  connect  with  the  condenser,  insert  stopper 
bearing  thermometer,  and  heat  until  distillation  of  the  turpentine  begins.  Con- 
duct the  distillation  so  that  the  distillate  passes  over  at  the  rate  of  2  drops  per 
second.  Note  the  initial  distilling  temperature  and  the  percentage  distilling 
below  170°  C. 

Polymerization.  Place  20  cc.  of  exactly  38/N  (100.92  per  cent2)  sulphuric  acid 
in  a  graduated,  narrow-neck  Babcock  flask,  stoppered,  and  place  in  ice-water 
and  cool.  Add  slowly  5  cc.  of  the  turpentine  to  be  tested.  Gradually  mix  the 
contents,  cooling  from  time  to  time,  and  not  allowing  the  temperature  to  rise  above 
about  60°  C.  When  the  mixture  no  longer  warms  up  on  shaking,  agitate  thor- 
oughly and  place  the  bottle  in  a  water  bath  and  heat  from  60  to  65°  C.  for  about 
ten  minutes,  keeping  the  contents  of  the  flask  thoroughly  mixed  by  vigorous 
shaking  five  or  six  times  during  the  period.  Do  not  stopper  the  flask  after  the 
turpentine  has  been  added,  as  it  may  explode.  Cool  to  room  temperature,  fill 
the  flask  with  concentrated  sulphuric  acid  until  the  unpolymerized  oil  rises  into 
the  graduated  neck.  Centrifuge  at  about  1200  R.P.M.  from  four  to  five  minutes, 
or  allow  to  stand  for  twelve  hours.  Read  unpolymerized  residue,  notice  its  con- 
sistency and  color,  and  determine  its  refractive  index. 

1  Stillman,  "  Engineering  Chemistry,"  p.  503. 
*4%freeS03. 


618  PAINT   AND   PAINT  PIGMENTS 


Standards  for  Turpentine,  A.  S.  T.  M. 

Turpentine  should  be  clear  and  free  from  suspended  matter  and  water,  and 
should  conform  to  the  following  requirements : 

The  color  shall  be  "  Standard  "  1  or  better. 

The  specific  gravity  shall  be  not  less  than  0.862  nor  more  than  0.872  at  15°.5  C. 

The  refractive  index  at  15°.5  C.  shall  be  not  less  than  1.468  nor  more  than 
1.478. 

The  initial  boiling-point  shall  be  not  less  than  150  nor  more  than  160°  C. 

Ninety  per  cent  of  the  turpentine  shall  distill  below  170°  C. 

The  polymerization  residue  shall  not  exceed  2%  and  its  refractive  index  at 
15°.5  C.  shall  not  be  less  than  1.500. 


ANALYSIS  OF  VARNISH 

The  testing  of  varnish  should  largely  be  of  a  physical  nature.  Such  properties 
as  odor,  consistency,  clarity,  flowing,  time  of  drying,  character  of  finish,  hard- 
ness, resistance  to  moisture  and  abrasion,  elasticity,  etc.,  point  out  the  real  value 
of  a  varnish.  Chemical  tests  that  give  additional  information,  sometimes  of  a 
valuable  nature,  are  as  follows:  Flash  point,  acid  number,  ash,  character  of  sol- 
vent, fixed  oil  and  resins. 

Flash  Point.  A  nickel  or  iron  crucible  of  60  mm.  diameter  and  40mm.  height 
is  filled  with  the  varnish  to  within  20  mm.  of  the  top.  It  is  then  supported  in  a 
water  bath  in  such  a  manner  as  to  be  about  two-thirds  immersed  in  the  water. 
The  water  should  be  from  15°  to  20°  C.  at  the  start  and  should  be  heated  slowly 
so  that  the  temperature  of  the  varnish,  as  indicated  by  a  thermometer  suspended 
in  it,  will  show  a  rise  of  about  1  degree  per  minute.  Test  for  flash  at  each  half 
degree,  using  a  very  small  flame. 

Acid  Number.  Ten  to  20  grams  of  the  varnish  are  weighed  into  a  small 
Erlenmeyer  flask,  50  cc.  neutral  alcohol  added,  and  a  small  funnel  inserted  in  the 
neck.  Heat  on  the  water  bath  for  one-half  hour,  with  occasional  shaking.  Allow 
to  cool  somewhat,  add  two  drops  of  phenolphthalein  indicator  and  titrate  with 
tenth-normal  potassium  hydroxide  solution.  The  acid  number  is  the  number  of 
milligrams  of  KOH  required  to  neutralize  each  gram  of  the  varnish. 

Ash.  Weigh  in  a  porcelain  or  fused  silica  crucible  several  grams  of  the  varnish. 
Burn  off  over  a  small  Bunsen  flame,  using  great  caution  to  avoid  boiling  over  and 
spattering.  When  all  combustible  matter  is  destroyed,  weigh  the  ash  and  if 
desired  analyze  it. 

Solvent.  Steam  distillation  of  a  portion  of  the  varnish  will  remove  the  sol- 
vents, leaving  a  residue  of  fixed  oils  and  varnish  resins,  which  may  be  weighed 
after  driving  off  the  water.  The  distillate  should  be  examined  as  recommended 
under  Methods  for  the  Examination  of  Turpentine.  The  amount  of  mineral 
spirits  and  turpentine  may  thus  be  determined. 

Fixed  Oils  and  Resins.  In  the  above  determination,  the  total  amount  of  fixed 
oils  and  resins  is  obtained.  It  is  a  difficult  matter,  however,  to  determine  the  exact 

1  The  term  "  Standard  "  refers  to  the  color  recognized  as  standard  by  the  "  Naval 
Stores  Trade."  Turpentine  is  qf  "  Standard  "  color  when  a  depth  of  50  mm.  in  a  per- 
fectly flat  polished  bottom  tube,  approximately  matches  a  No.  1  yellow  Lovibond 


PAINT   AND   PAINT  PIGMENTS  619 

percentage  and  character  of  resins  that  have  been  used  in  the  manufacture  of  the 
varnish.  This  is  due  to  the  fact  that  during  the  process  of  heating  oils  in  the 
presence  of  resins  many  intricate  chemical  changes  are  brought  about,  a  con- 
siderable portion  of  the  resins  being  distilled  off  in  the  form  of  vapors  and  com- 
binations of  the  oil  brought  about  that  are  difficult  of  separation.  One  of  the  best 
methods,  however,  of  separating  the  fixed  oils  and  varnish  resins  is  carried  out  in 
the  following  manner. 

A  portion  of  about  a  half  ounce  of  the  varnish  resin  should  be  placed  in  a  300-cc. 
tared  beaker.  There  should  then  be  added  about  200  cc.  of  ice-cold  petroleum 
ether  and  the  beaker  should  be  covered  and  allowed  to  stand,  preferably  in  a  dish 
containing  ice.  In  an  hour's  time  the  resinous  ingredients 'will  be  found  precipi- 
tated at  the  bottom  of  the  beaker  or  adhering  to  the  side  thereof  (with  the  ex- 
ception of  rosin,  which  is  largely  soluble  in  petroleum  ether).  The  precipitated 
resins  should  be  washed  with  fresh  portions  of  cold  petroleum  ether  two  or  three 
times,  pouring  the  decanted  portions  into  a  large  bottle.  The  combined  portions  of 
petroleum  ether  may  then  be  filtered  through  a  tared  filter,  adding  by  the  aid 
of  a  stirring  rod  the  resins  contained  in  the  beaker.  The  filter  paper  and  the  beaker 
with  the  resins  may  then  be  dried  at  100°  C.  and  weighed.  The  combined  filtrates 
may  be  distilled  to  obtain  the  fixed  oil  which  may  be  examined  for  constants. 
(This  fixed  oil  may  contain  rosin.)  The  amount  of  rosin  contained  in  a  varnish 
may  be  roughly  ascertained  by  thoroughly  shaking  in  a  separatory  funnel  a  portion 
of  the  varnish  with  a  large  quantity  of  absolute  alcohol.  The  rosin  may  be  ob- 
tained by  evaporation  of  the  alcoholic  extracts.  The  fixed  oils  after  oxidation  or 
polymerization,  as  caused  by  the  heating  of  the  varnish  during  manufacture,  are 
not  readily  soluble  in  alcohol. 

Separation  of  Polymerized  Oils  and  Resins.  In  the  making  of  varnish,  some 
oils  become  oxidized  or  polymerized  to  a  condition  resembling  resins.  For  instance, 
when  a  varnish  is  examined  for  resins  by  the  above  method,  it  will  often  be  found 
that  a  considerable  amount  of  matter  insoluble  in  petroleum  ether  will  be  obtained 
even  when  hard  resins  are  absent.  The  insoluble  substance  is  oxidized  or  polym- 
erized oil.  It  may  be  differentiated  from  varnish  resins  by  the  fact  that  it  is 
readily  saponified  by  alcoholic  potash.  The  following  method  by  Boughton 
(Technologic  Paper  No.  65,  U.  S.  Bureau  of  Standards),  though  involving  consider- 
able work,  is  probably  the  most  accurate  method  for  the  separation  of  polymerized 
oils  and  resins. 

To  about  4  grams  of  varnish  in  a  flask  add  about  25  cc.  of  water  and  boil  until 
the  volume  is  about  10  cc.  This  removes  nearly  all  of  the  volatile.  Add  25  cc. 
half  normal  alcoholic  potash  and  25  cc.  benzol  and  boil  under  a  reflux  condenser 
for  one-half  hour.  Evaporate  the  solution  to  about  15  cc.  and  add  about  10  cc. 
of  alcohol.  Transfer  completely  to  a  separatory  funnel,  washing  the  flask  with 
water  and  ether  and  using  a  policeman  if  necessary.  Dilute  with  water  to  about 
100  cc.,  add  100  cc.  of  ether,  and  shake.  Add  a  few  cc.  of  alcohol  if  necessary  to 
make  the  layers  separate.  Draw  off  the  aqueous  layer  and  wash  the  ether  three 
times  with  water  and  transfer  to  a  tared  flask  for  future  use. 

To  the  combined  soap  solution  and  washings,  add  an  excess  of  hydrochloric 
acid  and  extract  twice  with  50  cc.  of  ether.  Discard  the  aqueous  layer,  wash 
the  combined  ether  extracts  with  water,  transfer  to  a  flask  and  distill  off  the 
ether.  To  the  dry  residue  add  20  cc.  of  absolute  alcohol  and  20  cc.  of  a  mixture 
of  1  volume  of  sulphuric  acid  and  4  volumes  of  absolute  alcohol  and  boil  for  two 
minutes  under  a  reflux  condenser.  Completely  transfer  the  contents  of  the  flask 


620 


PAINT   AND   PAINT   PIGMENTS 


to  a  separately  funnel,  washing  the  flask  with  water  and  ether.  Add  100  cc. 
ether  and  after  agitation  add  100  cc.  of  10  per  cent  sodium  chloride  solution  and 
again  shake.  Draw  off  the  aqueous  layer,  extract  it  with  50  cc.  of  ether,  combine 
the  ether  solutions  and  wash  with  water.  Add  50  cc.  of  a  fifth-normal  potassium 
hydroxide  solution  and  10  cc.  of  alcohol,  shake  and  draw  off  the  lower  layer  into 
a  second  funnel.  Wash  the  ether  layer  with  50  cc.  of  water  containing  5  cc.  of 
the  potassium  hydroxide  solution  and  5  cc.  of  alcohol. 

Extract  the  combined  aqueous  portions  with  two  50-cc.  portions  of  ether  and 
finally  wash  the  combined  ether  solutions  (containing  the  ethyl  esters  of  the  fatty 
acids)  with  water. 

Distill  off  the  ether  and  boil  the  residue  with  25  cc.  of  half-normal  alcoholic 
potash  for  one-half  hour  under  a  reflux  condenser.  Transfer  completely  to  a  sepa- 
ratory  funnel  and  extract  the  soap  four  times  with  ether.  Wash  the  combined 
ether  solution  twice  with  water  and  add  it  to  the  first  ether  solution  of  unsaponi- 
fiable  matter  obtained. 

Unite  the  solution  and  washings  containing  the  soaps,  add  an  excess  of  hydro- 
chloric acid,  and  extract  twice  with  ether.  Transfer  to  a  tared  flask  the  combined 
ether  solutions,  after  washing  them  with  water,  distill  off  the  ether,  dry  the  residue 
to  constant  weight  at  110°  C.  and  weigh  as  "  fatty  acids." 

Report  the  percentage  of  fatty  acids  as  percentage  of  oil  and  calculate  the 
percentage  of  resin  by  difference. 


OTHER  MATERIALS 

For  detailed  methods  other  than  those  given  in  this  work,  for  the  examination 
of  shellac,  resins,  bitumens  and  other  raw  materials  of  the  vehicle  portion  of  paints 
and  varnishes,  the  following  references  may  be  consulted: 

Proceedings  of  the  American  Society  for  Testing  Materials  (Committee  D-l), 
1910-15. 

Analysis  of  Paints  and  Varnishes.  Gardner  and  Schaeffer.  McGraw-Hill 
Book  Co.,  New  York. 

Manufacture  of  Varnishes.  Livache  and  Mclntosh.  Vols.  I-III.  Scott; 
Greenwood  &  Son,  London. 


PAINT   AND   PAINT   PIGMENTS  621 


THE    ANALYSIS    OF    PAINT    PIGMENTS 

4 

The  vehicle  having  been  extracted  from  the  paint  under  examination,  by  the 
previously  outlined  methods,  the  pigment  is  left  ready  for  analysis.  The  pig- 
ment can  be  readily  classified  under  one  of  the  following  heads  by  its  color,  thus 
shortening  any  preliminary  examination.  Many  of  the  colors  have  a  white  base 
which  necessitates  a  determination  of  both  the  colored  portion  of  the  pigment 
and  any  white  base  which  may  have  been  used. 

The  general  analysis  of  colored  pigments  is  carried  out  according  to  the  specific 
method  outlined  for  the  individual  colored  pigments,  together  with  the  methods 
for  a  composite  white  paint,  provided  a  qualitative  examination  does  not  directly 
reveal  the  identity  of  the  pigment. 

The  pigments  used  in  the  manufacture  of  paints  are  classified  as  follows,  in 
certain  instances  the  trade  names  being  given  by  which  the  particular  pigments 
are  known. 

White  Pigments 

Lead  Pigments 

Sublimed  White  Lead — Basic  Sulphate  of  Lead — Basic  Sulphate — White  Lead. 
Corroded  White  Lead — Basic  Carbonate  of  Lead. 

Old  Dutch  Process  White  Lead. 

Quick  Pr  jcess  White  Lead. 

Mild  Process  White  Lead. 
Zinc  Lead. 
Leaded  Zinc. 

Zinc  Pigments 
Zinc  Oxide — Zinc  White. 
Lithopone— Ponolith— Beckton  White— Charlton  White— Orr's  White. 

Silica  Pigments 

Silica — Silex. 

Asbestine — Talcose. 

China  Clay — Kaolin — Tolamite. 

Calcium  Pigments 

Whiting— Paris  White— Chalk— Alba  Whiting— Spanish  White. 
Gypsum — Plaster  of  Paris — Terra  Alba — Agalite. 

Barium  Pigments 

Barytes — Barite— Blanc  Fixe — Barium  Sulphate. 
Barium  Carbonate — Witherite. 

Red  and  Brown  Pigments 

Red  Lead — Orange  Mineral. 

Vermilion. 

Ochres — Tuscan  Red — Indian  Red — Venetian  Red. 

Umbers — Siennas. 


622 


PAINT  AND   PAINT   PIGMENTS 


Blue  Pigments 

Sublimed  Blue  Lead. 

Ultramarine  Blue. 

Prussian  Blue — Antwerp  Blue — Chinese  Blue. 

Yellow  and  Orange  Pigments 

Chrome  Yellow — Lemon  Yellow — Medium  Chrome  Yellow. 
American  Vermilion — Orange  Chrome — Basic  Lead  Chromate. 
Orange  Mineral. 


Green  Pigments 


Chrome  Green. 
Chromium  Oxide. 
Green  Earth. 


Black  Pigments 

Graphite. 

Carbon  Black — Bone  Black — Lamp  Black — Drop  Black — Ivory  Black — Min- 
eral Black. 
Willow  Charcoal. 
Black  Oxide  of  Iron. 


ANALYSIS  OF  WHITE  PIGMENTS 

SUBLIMED  WHITE  LEAD 
Basic  Sulphate  of  Lead.     Basic  Sulphate — White  Lead 

This  pigment,  embracing  the  daily  analysis  by  the  manufacturers  of  the  product 
of  over  five  months'  time,  shows  the  following  average  composition: 

Lead  sulphate 76.68% 

Lead  oxide 17.23 

Zinc  oxide . .  5 . 79 


99.70 

The  remaining  .3  of  1  per  cent  consists  of  moisture  and  ash  which  are  rarely 
determined. 

The  analysis  of  this  pigment  based  on  the  following  method,1  which  depends 
upon  the  above  average  composition,  together  with  the  volumetric  determination 
of  the  total  lead  and  zinc  contents,  is  rapid  and  accurate. 

1  Jour,  of  Ind.  and  Eng.  Chem.,  6,  3,  200,  March,  1914. 


PAINT   AND   PAINT   PIGMENTS  623 


Volumetric  Determination  of  Lead  1 

One  gram  of  the  sample  is  dissolved  in  100  cc.  of  an  acid  ammonium  acetate 
solution  made  up  as  follows : 

Eighty  per  cent  acetic  acid 125  cc. 

Concentrated  ammonium  hydroxide 95  cc. 

Water 100  cc. 

Add  this  solution  hot,  dilute  with  50  cc.  water  and  boil  until  a  clear  solution  is 
obtained.  Dilute  to  200  cc.  and  titrate  with  standard  ammonium  molybdate 
solution,  using  a  freshly  prepared  solution  of  tannic  acid  as  an  outside  indicator. 
A  solution  of  ammonium  molybdate  containing  8.67  grams  per  liter  usually 
gives  a  solution  where, 

One  cc.  =0.01  gram  Pb. 

Standardize  against  pure  PbO,  pure  PbS04,  or  clean  lead  foil. 
For  further  details  of  this  method  see  p.  239. 


Volumetric  Determination  of  Zinc2 
Boil  1  gram  of  the  sample  with  the  following  solution : 

Water 30  cc. 

Ammonium  chloride 4  grams 

Concentrated  hydrochloric  acid 6  cc. 

If  the  sample  is  not  quite  dissolved,  the  result  is  unaffected,  as  the  residue  is 
lead  sulphate  or  precipitated  lead  chloride. 

Dilute  to  200  cc.  with  hot  water.  Add  2  cc.  of  a  saturated  sodium  hypo- 
sulphite solution  and  titrate  with  a  standard  solution  of  potassium  ferrocyanide, 
using  a  5%  solution  of  uranium  nitrate  as  an  outside  indicator.  Calculate  the 
zinc  to  zinc  oxide. 

Using  the  average  total  of  99.70%,  the  total  lead  found  and  the  zinc  oxide 
content,  the  composition  of  this  pigment  is  determined  by  the  following  calcu- 
lation : 

Total  percentage  of  lead  compounds  present 

=total  percentage  found  of  ZnO,  PbO  and  PbS04— percentage  of  ZnO. 

Total  percentage  of  lead  compounds  present 

=  99.70%  (average  total)  —percentage  ZnO. 

Atomic  weight  lead 207 . 1 

Molecular  weight  lead  oxide 223 . 1 

Molecular  weight  lead  sulphate 303 . 1 

As  a  hypothetical  case,  we  can  assume  the  presence  of  a  4.70%  ZnO  and 
69.00%  metallic  lead. 

1  Modification  of  Low's  Method,  "  Technical  Methods  of  Ore  Analysis,"  p.  149. 

2  Low's  Method,  "  Technical  Methods  of  Ore  Analysis^"  p.  284. 


624  PAINT   AND   PAINT   PIGMENTS 

/Mol.wt.PbSO,         pb  f        \  _      p 

\     At.  wt.  Pb  / 

- 


4.  Tiua/^  4.   puri 

Mol.  wt.PbSO4-mol.  wt.  PbO 

Mol.  wt.  PbO 
/Mol.wt.PbO 


%  P^O  present 


x%  pb  found    _%  pb  constituents 
\  At.  wt.  Pb  ^  I  _          p  ^ 

Mol.  wt.  PbO  -Mol.  wt.  PbSO4 
Mol.  wt.  PbS04 

Determining  the  percentage  of  lead  oxide  and  lead  sulphate  present  by  the 
above  formulas  we  find: 


(Hi*69-00)  -95-00 

'303.1-223.1 
223.1 

-95.00 


223.1-303.! 
303.1 


=P—ntPbSO,  =78.32. 


If  it  is  necessary  actually  to  determine  the  percentage  of  lead  sulphate  present, 
the  following  procedure  may  be  followed: 


Total  Sulphate 

Mix  0.5  gram  of  the  sample  with  3  grams  of  sodium  carbonate.  Add  30  cc. 
of  water  and  boil  gently  for  ten  minutes.  Allow  to  stand  for  four  hours.  Dilute 
with  hot  water,  filter  and  wash  thoroughly.  All  the  lead  sulphate  is  here  changed 
to  lead  carbonate,  the  sodium  carbonate  being  transposed  to  sodium  sulphate, 
which  is  found  in  the  filtrate. 

The  sulphate  is  determined  in  the  filtrate  by  precipitation  as  BaS04.  Calcu- 
late the  BaS04  to  PbS04.  Determine  the  total  lead  as  above  outlined,  deduct 
the  lead  found  as  PbS04  and  calculate  the  residual  lead  to  PbO. 

The  foregoing  method  is  the  one  generally  used  in  the  commercial  estimation 
of  lead  and  yields  excellent  results  to  the  analyst  who  is  familiar  with  it.  How- 
ever, in  laboratories  where  only  occasional  lead  determinations  are  made,  the 
well-known  gravimetric  methods  for  lead  and  zinc  will  sometimes  be  found  prefer- 
able. The  time  required  for  gravimetric  determinations  is  not  much  greater 
and  the  chance  of  error  is  reduced. 

The  method  referred  to  consists  in  weighing  the  lead  as  sulphate l  and  the 
precipitation  of  the  zinc  from  the  filtrate  with  sodium  carbonate,  igniting  it,  and 
weighing  as  zinc  oxide. 

1  As  outlined  under  Basic  Carbonate  of  Lead,  p.  625. 


PAINT  AND  PAINT  PIGMENTS  625 


CORRODED  WHITE   LEAD 

Basic  Carbonate  of  Lead1 — Old  Dutch  Process  White  Lead — Quick  Process 
White  Lead— Mild  Process  White  Lead 

Corroded  white  lead  contains  approximately  80%  metallic  lead  and  20% 
carbonic  acid  and  combined  water  with  traces  sometimes  of  silver,  antimony  and 
other  metals.  The  formula  for  this  compound  is  2PbC03  «Pb(OH)j. 

Total  Lead  (Gravimetric) 

Dissolve  1  gram  in  20  cc.  of  HN03  (1 : 1)  in  a  covered  beaker,  heating  till  all 
COj  is  expelled;  wash  off  cover,  add  20  cc.  of  H2SO  4(1 : 1)  and  evaporate  to  fumes 
of  S03,  cool,  add  about  150  cc.  of  water  and  150  cc.  of  ethyl  alcohol;  let  stand 
in  cold  water  one  hour,  filter  on  a  Gooch  crucible,  wash  with  95%  ethyl  alcohol, 
dry  at  110°  C.,  and  weigh  the  PbS04.  Calculate  to  PbO  or  to  basic  carbonate.* 
Instead  of  determining  the  lead  as  sulphate,  the  sample  may  be  dissolved  by 
boiling  with  acetic  acid;  then  dilute  to  about  200  cc.  with  water,  make  alkaline 
with  NH4OH,  then  acid  with  acetic  acid,  heat  to  boiling  and  add  10  to  15  cc. 
of  a  10%  solution  of  potassium  dichromate;  heat  till  the  yellow  precipitate 
assumes  an  orange  color.  Let  settle  and  filter  on  a  Gooch  crucible,  washing  by 
decantation  with  hot  water  till  the  washings  are  colorless,  finally  transferring 
all  of  the  precipitate.  Then  wash  with  95%  ethyl  alcohol  and  then  ether;  dry 
at  1 10°  C.  and  weigh  PbCr04.  (Any  insoluble  matter  should  be  filtered  out  before 
precipitating  the  lead.) 

Total  Lead  (Volumetric) 

Dissolve  0.5  gram  of  sample  in  10  cc.  of  concentrated  hydrochloric  acid,  boil 
till  solution  is  effected,  cool,  dilute  to  40  cc.  and  neutralize  with  ammonium 
hydroxide.  Add  acetic  acid  until  distinctly  acid,  dilute  to  200  cc.  with  hot  water, 
boil  and  titrate  with  ammonium  molybdate  as  follows: 

Dissolve  4.25  gram  of  ammonium  molybdate  in  water  and  make  up  to  one 
liter.  To  standardize  this  solution,  dissolve  about  0.2  gram  of  pure  lead  foil  in 
nitric  acid  (pure  PbO  or  PbS04  may  also  be  used),  evaporate  nearly  to  dryness, 
add  30  cc.  of  water,  then  5  cc.  H2S04  (  sp.gr.  1.84),  cool,  and  filter. 

Drop  filter  with  PbS04  into  a  flask,  add  10  cc.  concentrated  HC1,  boil  till 
completely  disintegrated,  add  15  cc.  of  HC1,  25  cc.  of  water,  and  NH4OH  till 
alkaline.  Acidify  with  acetic  acid,  dilute  to  200  cc.  with  hot  water  and  boil. 
Titrate,  using  an  outside  indicator  of  one  part  of  tannic  acid  in  300  parts  of  water. 

It  should  be  noted  that  when  calcium  is  present,  it  forms  a  more  or  less 
insoluble  molybdate,  and  results  are  apt  to  be  high.  With  samples  containing 
less  than  10%  of  lead,  the  lead  should  be  precipitated  as  PbS04,  filtered,  redis- 
solved  and  titrated  as  in  the  process  of  standardizing. 

Carbon  Dioxide 

Determine  by  evolution  with  dilute  hydrochloric  acid  absorbing  in  soda-lime 
or  KOH  solution.  Calculate  CO2  to  PbC03,  subtract  PbO  equivalent  from 
total  PbO  and  calculate  residual  PbO  to  Pb(OH)2. 

1  Tentative  Methods  for  the  Routine  Analysis  of  White  Pigments.     Report  of 
Commission  D-l,  American  Society  for  Testing  Materials,  1915. 

2  This  method  of  weighing  lead  sulphate  is  not  accurate  in  the  presence  of  calcium 
compounds. 


626 


PAINT  AND   PAINT  PIGMENTS 


Acetic  Acid ! 

Place  18  grams  of  the  pigment  in  a  500-cc.  flask,  add  40  cc.  of  sirupy  phos- 
phoric acid,  18  grams  of  zinc  dust  and  50  cc.  of  water.  Connect  to  a  straight 
Liebig  condenser,  apply  heat  and  distill  down  to  a  small  bulk.  Then  pass  steam 
into  the  flask  until  it  becomes  about  half  full  of  condensed  water,  shut  off  the 
steam  and  distill  down  to  a  small  bulk — this  operation  being  conducted  twice. 
To  the  total  distillate  which  was  collected  in  a  larger  flask  add  1  cc.  of  sirupy 
phosphoric  acid,  connect  to  a  Liebig  condenser,  using  a  spray  trap,  and  distill 
to  a  small  volume — about  20  cc.  Pass  steam  through  till  about  200  cc.  of  water 
condense  in  the  distillation  flask,  shut  off  steam  and  continue  the  distillation. 
These  operations  of  direct  and  steam  distillations  are  conducted  until  10  cc.  of 
the  distillate  require  only  1  drop  of  0.1  N  alkali  to  give  a  change  in  the  presence  of 
of  phenolphthalem.  Then  titrate  the  total  distillate  with  0. 1  N  sodium  hydroxide 
and  phenolphthalein  and  calculate  the  total  acidity  as  acetic  acid.  It  will  be 
found  convenient  to  titrate  each  200-cc.  portion  of  the  distillate  as  collected. 

Metallic  Lead1 

Weigh  50  grams  of  the  sample  into  a  400-cc.  beaker,  add  a  little  water  and  add 
slowly  60  cc.  of  40%  acetic  acid  and  after  effervescence  has  ceased,  boil  on  hot 
plate.  Fill  the  beaker  with  water,  let  settle,  and  decant  the  clear  solution. 
To  the  residue  add  100  cc.  of  a  mixture  of  360  cc.  of  strong  NH4OH,  1080  cc.  of 
water,  2160  cc.  of  80%  acetic  acid,  and  boil  until  all  solution  is  complete.  Fill 
the  beaker  with  water,  let  settle  and  decant  the  clear  solution.  Collect  residue 
on  a  watch-glass,  floating  off  everything  but  metallic  lead.  Dry  and  weigh. 
Result  X2  =  percentage  of  metallic  lead  in  sample. 

The  following  method  of  A.  N.  Finn  (unpublished)  gives  total  basicity  of  a 
pure  white  lead:  Place  2  grams  of  pigment  in  an  evolution  flask,  add  a  little  C02- 
free  water,  connect  with  a  separatory  funnel  and  condenser  (Knorr  type),  add 
through  the  funnel,  finally  washing  down,  100  cc.  of  N/4  nitric  acid,  boil  and 
absorb  the  C02  in  a  soda  lime  tube  in  the  usual  manner  (having  H2S04  and  CaClj 
drying  tubes  in  train)  and  weigh.  To  the  solution  in  the  evolution  flask,  add 
about  20  cc.  of  neutral  sodium  sulphate  solution  and  titrate  with  N/4  sodium 
hydroxide  solution  (carbonate-free),  using  phenolphthalein.  C02  is  calculated  to 
PbCOi.  The  amount  of  N/4  acid  corresponding  to  the  C02  is  calculated  and 
deducted  from  the  total  amount  of  N/4  acid  neutralized  by  the  sample  and  the 
difference  calculated  to  combined  H20,  from  which  Pb(OH)2  is  computed. 


ZINC  LEAD  AND  LEADED  ZINC 

Zinc  lead  and  leaded  zinc  are  varying  compounds  containing  zinc  oxide 
and  lead  sulphate,  the  former  showing  approximately  50%  zinc  oxide  and  50% 
lead  sulphate,  while  the  latter  contains  on  an  average  25%  lead  sulphate  and 
75%  zinc  oxide.  See  also  pp.  239,  480. 

These  pigments  may  be  analyzed  by  the  following  procedure : 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

1  Thompson's  Method,  Jour.  Soc.  Chem.  Ind.,  24,  487  1905. 


PAINT   AND   PAINT   PIGMENTS  627 

Lead  and  Zinc.  Determine  the  lead  directly  by  the  volumetric  molybdate 
method  and^the  zinc  by  the  volumetric  ferrocyanide  method  as  outlined  under 
Sublimed  Wnite  Lead.  See  also  pages  239  and  480. 

Total  Soluble  Sulphates1  (in  the  absence  of  BaS04).  Treat  0.5  gram  of 
the  sample  with  5  cc.  of  water,  3  grams  of  NH4C1  and  5  cc.  of  HC1  saturated 
with  bromine;  digest  (covered)  on  the  steam  bath  about  fifteen  minutes,  add  25 
cc.  of  H20,  neutralize  with  dry  Na2C03  and  add  about  2  grams  more.  Boil 
ten  to  fifteen  minutes;  let  settle,  dilute  with  hot  water,  filter  and  wash  with 
hot  water;  redissolve  in  HC1,  reprecipitate  as  above  and  wash  thoroughly  with 
hot  water.  Acidify  the  united  filtrates  with  HC1  and  add  a  slight  excess  of 
10%  BaCl2  solution.  Let  stand  on  steam  bath  for  one  hour,  filter,  wash  with 
hot  water,  ignite  and  weigh  the  BaS04.  Calculate  to  S03  (includes  80s  formed 
fromS02). 

Total  Soluble  Sulphate  (in  the  presence  of  BaS04).  Treat  1  gram  in  a 
600-cc.  beaker  with  10  cc.  of  H20,  10  cc.  of  strong  HC1,  saturated  with  bromine, 
and  5  grams  of  NH4C1,  heat  on  a  steam  bath  in  a  covered  beaker  for  five  minutes, 
add  hot  water  to  make  about  400  cc.,  boil  for  five  minutes  and  filter  to  separate 
any  insoluble  material.  (A  pure  pigment  should  be  completely  dissolved.)  Wash 
with  hot  water,  ignite  and  weigh  the  insoluble.  Remove  lead  with  Na2C03  as 
above,  making  a  double  precipitation,  acidify,  and  to  the  boiling  hot  filtrate  add 
slowly,  with  stirring,  20  cc.  of  a  10%  BaCl2  solution;  let  stand  for  two  hours  on 
the  steam  bath,  filter,  wash,  ignite,  and  weigh  as  BaS04.  (Includes  S03  formed 
from  S02.) 

Soluble  Zinc  Sulphate.  Boil  2  grams  of  the  sample  with  150  cc.  of  water 
and  50  cc.  of  alcohol  for  thirty  minutes,  filter  and  wash  with  a  mixture  of  alcohol 
and  water  (1:3).  Heat  the  filtrate  to  boiling  and  expel  most  of  the  alcohol;  then 
determine  S03  by  the  usual  method  of  precipitation  with  BaCl2.  Calculate  to 
ZnS04  and  to  S03. 

Sulphur  Dioxide.  Digest  2  grams  of  the  sample  with  frequent  stirring  in 
100  cc.  of  freshly  boiled  cold  water  and  5  cc.  of  concentrated  HC1;  let  stand  ten  to 
fifteen  minutes,  add  an  excess  of  0.01  normal  iodine  solution  and  titrate  back  with 
0.01  normal  sodium  thiosulphate  solution,  using  starch  indicator.  Report  as 
S02.  Run  blank  on  reagents  and  make  corrections. 

Calculations.  Report  soluble  S03  as  ZnS04.  Deduct  ZnO  equivalent  of  the 
ZnS04  from  total  ZnO  and  report  residue  as  ZnO.  Deduct  soluble  S03  and  SOS 
equivalent  to  S02  from  total  S03,  calculate  remainder  to  PbS04;  subtract  PbO 
equivalent  of  PbS04  from  total  PbO  and  report  remainder  as  PbO. 

ZINC  OXIDE2 

Moisture.  Weigh  10  grams  on  watch-glass  and  dry  for  two  hours  at  105  to 
110°  C.  Cool  and  weigh. 

Carbon  Dioxide.  Place  10  grams  in  a  4-ounce  Erlenmeyer  flask,  moisten  with 
water,  add  solution  of  KMn04  to  oxidize  S02,  insert  a  two-hole  rubber  stopper, 
with  an  acid  delivery  tube  and  connect  to  a  carbon  dioxide  apparatus.  This 
apparatus  consists  of  a  tube  containing  KOH  solution,  preceding  the  flask  with 

1  Report  of  Sub-committee  VIII  of  Committee  D-l,  Proceedings  of  American 
Society  for  Testing  Materials,  14,  271-2,  1914. 

2  Frank  G.  Breyer,  Chief,  Testing  Department,  The  New  Jersey  Zinc  Co. 


628  PAINT   AND   PAINT   PIGMENTS 

sample,  to  absorb  any  C02  from  the  air  drawn  in.  The  flask  is  followed  by  a  tube 
with  concentrated  H2S04  to  absorb  moisture,  a  calcium  chloride  tube,  and  next 
is  a  weighed  Geissler  l  bulb  with  KOH  solution,  to  absorb  the  C02  from  the  sample; 
this  is  followed  by  another  calcium  chloride  tube  which  is  connected  to  a  suction 
line.  The  acid  delivery  tube  contains  25  cc.  H2S04  (1:1)  and  before  opening 
the  stopcock  the  suction  is  applied  to  insure  that  the  connections  are  all  air- 
tight; if  there  is  no  leak  the  acid  is  allowed  to  flow  into  the  flask  and  the  suction 
regulated  so  that  the  bubbles  in  the  Geissler  bulb  may  easily  be  counted.  The 
flask  is  heated  cautiously  to  boiling  for  a  minute  or  two,  the  flame  removed  and 
the  suction  allowed  to  proceed  from  thirty  to  forty  minutes.  The  Geissler  1  bulb 
is  then  disconnected,  placed  in  the  balance  for  fifteen  minutes  together  with  the 
end  calcium  chloride  tube  and  then  weighed.  The  KOH  solution  used  for 
absorption  is  of  the  same  strength  as  for  carbon  in  steel. 

Insoluble.  Treat  10  grams  in  a  250-cc.  beaker  with  50  cc.  concentrated  HC1, 
evaporate  to  dryness,  take  up  residue  with  HC1  and  water,  filter  and  wash 
thoroughly  with  HC1  (1  :  4)  and  hot  water.  Ignite  filter  paper  and  contents 
in  a  weighed  platinum  crucible. 

Sulphuric  Anhydride;  Total  S  as  SOs.  Treat  10  grams  with  50  cc.  strong 
HC1  and  a  few  cc.  of  bromine  water;  boil  to  expel  bromine,  filter  from  insoluble, 
wash  with  hot  water.  Neutralize  the  excess  of  HC1  with  ammonia,  keeping  the 
solution  slightly  acid,  heat  to  boiling  and  add  about  15  cc.  of  hot  BaCl2.  Let 
stand  overnight,  filter  on  a  weighed  Gooch  crucible,  wash  well  with  hot  water, 
ignite  in  a  muffle,  cool  and  weigh  as  BaS04. 

Lead  Oxide 

Gravimetric  Method.  Treat  10  grams  with  50  cc.  strong  HC1  and  50  cc. 
H2S04  (1  :  1),  evaporate  on  a  hot  plate,  and  finally  over  a  Bunsen  burner  to  strong 
fumes  of  S03. 

Cool,  and  add  100  cc.  water,  heat  again  to  dissolve  the  soluble  sulphates,  cool, 
add  25  cc.  95%  alcohol,  let  stand  overnight,  filter  on  a  Gooch  crucible  and  wash 
with  dilute  H2S04,  and  finally  with  alcohol.  Dry  at  110°  C.,  ignite  for  five  to  ten 
minutes,  cool  and  weigh.  Dissolve  the  PbS04  in  the  Gooch  crucible  with  a  hot 
solution  of  ammonium  acetate,  slightly  acidify  with  acetic  acid,  wash  with  hot 
water,  dry  at  110°  C.,  ignite  and  weigh  again.  The  loss  in  weight  is  PbS04,  from 
which  the  PbO  is  calculated. 

Electrolytic  Method.  9.330  grams  of  the  sample  are  dissolved  in  a  250-cc. 
beaker  with  40  cc.  concentrated  HNO3  and  about  50  cc.  of  distilled  water.  The 
solution  is  boiled  for  a  few  minutes  until  all  red  fumes  are  expelled.  Add  enough 
silver  nitrate  solution  to  precipitate  all  chlorides  (an  excess  of  silver  nitrate  does 
not  interfere)  and  dilute  to  about  200  cc. 

Electrolyze  for  two  hours,  using  about  .5  ampere  current.  The  solutions  are 
tested  for  lead  before  turning  off  the  current  by  raising  the  liquid  in  the  beaker, 
and  allowing  to  continue  for  twenty  minutes.  If  there  is  no  fresh  deposit  of  PbO?, 
the  electrode  is  washed  three  times  with  distilled  water  (current  still  on)  and  then 
after  removal  from  the  electrolytic  stand,  with  alcohol.  After  drying  one  hour 
at  110°  C.  the  electrode  is  weighed.  The  weight  of  PbO*  in  milligrams  divided 
by  100  gives  the  percentage  of  PbO. 

*See  Procedure  for  COs  determination  in  the  chapter  on  Carbon,  p.  103. 


PAINT   AND   PAINT  PIGMENTS  629 

Chlorine.  Treat  10  grams  of  sample  with  50  cc.  strong  HN03,  add  10  cc. 
N/10  AgN03,  boil,  cool,  add  10  cc.  ferric  nitrate  (1  :  3),  and  titrate  the  excess 
of  AgN03  with  NH4CNS  (9  grams  per  liter  of  solution).  A  blank  determination 
is  conducted  in  a  similar  manner  and  from  the  amount  of  N/10  AgNO3  required 
the  chlorine  is  calculated. 

Ferric  Oxide.  Treat  10  grams  with  50  cc.  strong  HC1,  add  about  1  gram 
KC103,  and  boil  down  to  a  syrupy  consistency.  Cool,  add  water  and  a  large 
excess  of  ammonia.  Allow  to  stand  until  the  ferric  oxide  separates,  and  filter; 
wash  with  dilute  ammonia  water  and  then  with  hot  water.  Dissolve  the  pre- 
cipitate of  ferric  oxide  in  an  Erlenmeyer  flask  with  warm  dilute  H2S04.  Wash 
the  filter  paper  thoroughly  with  hot  water,  dilute  the  solution  in  the  Erlenmeyer 
flask  to  about  200  cc.  and  pass  in  hydrogen  sulphide  for  five  minutes.  Place  a 
funnel  in  the  neck  of  the  flask  and  boil  until  all  H2S  is  expelled.  Cool  and  titrate 
with  dilute  KMn04.  A  blank  determination  is  carried  out  in  a  similar  manner 
and  the  number  of  cc.  of  KMn04  required  to  give  a  pink  color  is  subtracted  from 
the  total  number  required  on  the  sample. 

Manganese  Oxide.  Treat  a  10-gram  sample  in  a  16-oz.  Erlenmeyer  flask 
with  100  cc.  of  HN03  (1:3),  heat  to  boiling  and  add  a  pinch  of  sodium  bismuthate, 
when  the  pink  color  of  permanganic  acid  is  produced;  now  add  a  few  cc.  of  dilute 
Na2S203  solution  to  destroy  the  pink  color,  and  continue  boiling  to  drive  off  all 
nitrous  oxide  fumes.  Cool  thoroughly  and  add  50  cc.  of  a  3%  solution  of  HN03, 
and  a  very  small  pinch  of  sodium  bismuthate  to  restore  the  pink  color  again. 
Filter  the  solution  through  a  Gooch  crucible  to  remove  the  excess  of  sodium 
bismuthate,  rinsing  the  flask  and  Gooch  with  50  cc.  of  3%  HN03  solution  to 
which  a  small  amount  of  sodium  bismuthate  has  been  added.  Now  add  10  cc. 
of  ammonium  ferrous  sulphate  solution,  and  titrate  the  excess  of  ammonium  ferrous 
sulphate  with  standard  KMn04  whose  iron  value  has  been  determined.  One  gram 
of  KMn04  per  liter  is  a  convenient  strength;  and  12.4  grams  of  ammonium  fer- 
rous sulphate,  and  50  cc.  strong  H2S04  to  the  liter  gives  a  solution  which  is  almost 
equal  to  the  permanganate  solution.  A  blank  determination  is  carried  out  in 
exactly  the  same  manner  as  with  the  sample  of  oxide,  and  the  difference  in  the 
number  of  cc.  of  KMn04  required  to  give  a  pink  color  with  the  blank  deter- 
mination and  the  sample  of  oxide  is  equal  to  the  amount  of  MnO  present.  The 
manganese  value  of  the  KMn04  is  calculated  from  the  iron  value,  according  to 
the  ratio  of  Mn  :  Fe,  or  55  :  279.5  or  0.1968  :  1. 

Arsenous  Oxide.  Weigh  10  grams  of  oxide  in  a  16-ounce  Erlenmeyer  flask, 
add  about  10  grams  of  FeS04,  place  a  rubber  stopper  with  an  acid  delivery  tube 
and  an  exit  tube,  which  is  immersed  in  a  beaker  containing  about  200  cc.  dis- 
tilled water.  The  beaker  of  water  is  placed  in  a  pan  of  cold  water,  the  pan 
having  an  inlet  and  overflow.  Now  add  100  cc.  strong  HC1  from  the  delivery 
tube,  and  heat  the  flask  to  boiling  so  as  to  distill  the  arsenic  into  the  beaker  of 
water.  Continue  boiling  until  about  two-thirds  of  the  acid  has  been  distilled, 
remove  from  the  flame,  rinse  the  delivery  tube,  add  10  cc.  strong  HC1  to  the 
solution  in  the  beaker,  warm  and  pass  in  H2S  to  precipitate  the  arsenic,  as  As2S3. 
Let  stand  in  a  warm  place  for  some  time  and  filter  in  a  Gooch  crucible,  wash 
the  precipitate  of  As2S3  with  alcohol  and  then  with  carbon  bisulphide  and  several 
times  with  dilute  alcohol.  Dry  at  105°  C.  for  one  hour  and  weigh.  Dissolve 
the  As2S3,  in  the  Gooch  crucible  with  dilute  ammonia  water,  wash  well  with  hot 
water,  and  dry  at  105°  C.  and  reweigh.  The  loss  in  weight  is  As2S3,  from  which 
the  As20a  may  be  calculated.  See  procedure  for  arsenic  distillation,  p.  33. 


630  PAINT   AND   PAINT  PIGMENTS 

SO2  Equivalent.  Treat  10  grams  in  a  250-cc.  beaker  with  25  cc.  cold  water, 
25  cc.  hot  water,  add  some  starch  solution  and  titrate  with  N/10  iodine  solution, 
gradually  adding  25  cc.  HC1  until  a  permanent  blue  color  appears. 

Zinc  Oxide.  The  percentage  of  ZnO  is  found  by  adding  together  all  the 
percentages  of  impurities,  except  the  S02  equivalent,  and  subtracting  this  sum 
from  100. 

LITHOPONE 
Ponolith— Beckton  White— Charlton  White,  etc. 

This  pigment  is  a  chemically  precipitated  pigment  containing  approximately 
from  69  to  70  per  cent  barium  sulphate,  the  remainder  consisting  of  zinc  sul- 
phide, with  occasional  impurities  of  zinc  oxide  and  carbonate. 

Moisture.     Heat  2  grams  for  two  hours  at  105°  C. 

Barium  Sulphate.  Treat  1  gram  with  10  cc.  cone.  HC1  and  1  gram 
of  potassium  chlorate,  added  in  small  amounts.  Evaporate  to  one-half  its 
volume,  add  100  cc.  hot  water  and  a  few  cc.  of  dilute  H2S04.  Boil,  filter,  wash 
and  weigh  the  insoluble  residue,  which  should  show  only  the  presence  of  barium 
sulphate.  Examine  the  residue  for  silica  and  alumina. 

Total  Zinc.  Determine  the  total  zinc  in  the  filtrate  by  the  volumetric 
method  as  outlined  under  Sublimed  White  Lead. 

Zinc  Sulphide.  Digest  1  gram  at  room  temperature  for  one-half  hour  with 
100  cc.  of  1%  acetic  acid.  Filter  and  determine  the  zinc  in  the  precipitate  by 
solution  in  HC1  as  under  Sublimed  White  Lead. 

Zinc  soluble  in  acetic  acid  is  reported  as  zinc  oxide,  zinc  insoluble  as  zinc 
sulphide.  The  filtrate  from  the  acetic  acid  treatment,  after  precipitating  the  zinc 
as  zinc  sulphide  and  subsequent  removal,  should  be  examined  for  barium  which 
might  be  present  as  carbonate,  and  calcium,  present  as  either  sulphate  or  car- 
bonate. The  zinc  sulphide  may  also  be  determined  by  the  method  as  outlined 
under  Tentative  Methods  for  Analysis  of  Pigments  by  Committee  D-I l  as 
follows: 

Zinc  Sulphide.8  Place  0.5  gram  of  the  pigment  in  an  evolution  flask 3  with 
about  10  grams  of  "  feathered  "  or  mossy  zinc,  add  50  cc.  of  water;  insert  the 
stopper  carrying  a  separatory  funnel  and  an  exit  tube.  Run  in  50  cc.  of  con- 
centrated HC1  from  the  funnel,  having  previously  connected  the  exit  tube  to  two 
absorption  flasks,  in  series;  first  flask  contains  100  cc.  of  alkaline  lead  nitrate 
solution,  second  flask,  50  cc.  of  same  as  a  safety  device.  After  all  of  the  acid 
has  run  into  the  evolution  flask,  heat  slowly,  finally  boiling  until  the  first  appear- 
ance of  steam  in  the  first  absorption  flask.  Disconnect,  let  the  lead  sulphide 
settle,  filter,  wash  with  cold  water,  then  with  hot  water  till  neutral  to  litmus 
paper  and  washings  give  no  test  for  lead.  The  PbS  precipitate  in  dissolved  in 
hot,  dilute  HN03,  evaporated  to  fumes  with  H2S04  and  finally  weighed  as  PbS04. 
Calculate  PbS  or  PbS04  to  ZnS. 

The  alkaline  lead  solution  is  made  as  follows:  Into  100  cc.  of  KOH  solution 
(56  grams  in  140  cc.  of  H20)  pour  a  saturated  solution  of  lead  nitrate  (250  grams 
in  500  cc.  of  H20)  until  the  precipitate  ceases  to  redissolve,  stirring  constantly 

1  American  Society  for  Testing  Materials,  1915. 

1  Evolution  Method  of  W.  G.  Scott,   "  White  Paints  and  Painting  Material/ 
p.  257;  see  also  p.  398,  chapter  on  Sulphur  by  W.  W.  Scott. 
3  See  Apparatus  on  p.  399. 


PAINT  AND  PAINT  PIGMENTS  631 

while  mixing.  About  three  volumes  of  the  lead  solution  will  be  required  for  one 
of  the  alkali. 

Instead  of  absorbing  the  evolved  H2S  in  alkaline  lead-nitrate  solution,  a 
solution  of  8  grams  of  cadmium  chloride  in  250  cc.  of  water  and  150  cc.  of  NH4OH 
(sp.gr.  0.90)  may  be  used.  The  CdS  precipitate  may  be  filtered  on  a  weighed 
Gooch,  washed  with  water  containing  a  little  NH4OH,  dried  at  100°  C.,  and 
weighed.  Calculate  to  ZnS.  It  is  better  to  filter  the  CdS  on  a  small  filter  and 
wash  as  above,  then  place  filter  and  precipitate  in  a  beaker  and  dissolve  in  HC1 
and  KC103  (keeping  at  room  temperature  at  first).  Filter  out  any  paper  pulp 
or  insoluble  matter,  make  filtrate  alkaline  with  NH4OH,  then  just  acid  with 
HC1,  heat  to  boiling  and  precipitate  with  BaCl2  in  the  usual  manner.  Filter, 
wash,  ignite,  and  weigh  the  BaS04.  Calculate  to  ZnS. 

For  very  rapid  work  the  contents  of  the  absorption  flask,  after  all  H2S  has 
been  absorbed,  may  be  washed  into  a  vessel  with  cold  water  and  diluted  to  about 
1  liter,  acidified  with  concentrated  HC1  and  titrated  with  standard  iodine  solu- 
tion, using  starch  indicator.  (The  precipitate  should  be  completely  dissolved.) 
The  iodine  solution  is  prepared  by  dissolving  about  12.7  grams  of  pure  resublimed 
iodine  and  18  grams  of  KI  in  a  little  water  and  then  diluting  to  1  liter. 

Soluble  Salts.  Digest  2  grams  with  hot  water  and  examine  the  filtrate  for 
soluble  salts. 

SILICA  OR  SILEX— CHINA  CLAY— ASBESTINE 

These  pigments,  while  all  true  silica  pigments,  are  widely  different  from  the 
standpoint  of  physical  structure.  A  microscopic  examination  is  of  great  value, 
showing  silica  or  silex  to  consist  of  small,  sharp  particles,  china  clay  to  be  tabloid 
in  appearance  and  asbestine  to  consist  of  long,  rod-like  fibrous  particles. 

The  following  procedure  taken  from  the  outlined  method  published  by  Sub- 
Committee  VIII  of  Committee  D-I1  will  well  serve  for  the  analysis  of  these 
pigments. 

Moisture.    Heat  2  grams  at  105°  for  two  hours. 

Loss  on  Ignition.    Ignite  1  gram  to  constant  weight  in  a  platinum  crucible. 

Insoluble  Matter.  Boil  2  grams  for  thirty  minutes  with  50  cc.  HC1  (1  :  1), 
add  50  cc.  of  water,  wash,  ignite,  and  weigh  insoluble  residue. 

In  the  case  of  China  clay,  or  asbestine,  a  sodium  carbonate  fusion  should  be 
resorted  to,  with  the  subsequent  dehydration  of  the  silica. 

The  insoluble  residue  in  either  case  is  volatilized  with  H2S04  and  HF  in  the 
usual  manner,  any  loss  in  weight  being  considered  silica.  Any  residue  is  fused 
with  sodium  carbonate,  the  fusion  being  added  to  the  original  filtrate.  Should 
BaS04  be  present,  the  melt  is  digested  with  warm  water,  the  BaC03  filtered  off, 
washed,  dissolved  in  hot  dilute  HC1  and  precipitated  and  determined  as  BaS04. 

The  filtrates,  combined  from  the  preceding  filtrations,  are  examined  for 
alumina,  iron,  manganese,  calcium  and  magnesium  in  the  usual  way. 

Should  it  be  necessary  to  determine  the  alkalies  present,  a  separate  sample 
is  treated  according  to  the  method  of  Mr.  J.  Lawrence  Smith  as  in  Bulletin  No. 
422,  U.  S.  Geological  Survey.  See  page  355. 

Carbon  Dioxide.  Determine  by  evolution  with  HC1,  weighing  in  soda- 
lime,  KOH  solution,  or  by  absorbing  in  Ba(OH)2  solution  and  titrating  or  weigh- 
ing as  BaC03.  See  p.  103. 

1  Proceedings  of  American  Society  for  Testing  Materials,  14,  279, 1914. 


632 


PAINT   AND  PAINT   PIGMENTS 


Any  excess  of  calcium  is  reported  as  oxide.  The  magnesium  is  calculated  as 
MgO,  unless  the  carbon  dioxide  is  in  excess  of  the  amount  of  calcium  present, 
in  which  case  it  is  reported  as  MgC03,  and  the  remainder  as  MgO. 

WHITING— PARIS  WHITE 
Gypsum — Plaster  of  Paris 

These  pigments  are  of  the  following  composition: 

Whiting.    The  natural  form  of  calcium  carbonate. 

Paris  White.    The  artificial  form  of  calcium  carbonate. 

Gypsum.    The  hydrated  form  of  calcium  sulphate,  of  formula  CaS04-2H20. 

These  pigments  are  analyzed  in  the  following  manner: 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

Loss  on  Ignition.  Ignite  1  gram  at  a  high  heat  to  constant  weight.  The 
loss  will  be  water,  if  carbonates  are  absent. 

Calcium.  Treat  1  gram  with  dilute  HC1  and  a  few  drops  of  HN03. 
Evaporate  to  dryness,  dehydrate,  moisten  with  a  few  drops  of  concentrated 
HC1,  dilute  with  hot  water  and  determine  the  insoluble  residue.  Examine 
for  BaS04.  The  residue  should  consist  of  silica. 

In  the  filtrate,  precipitate  and  determine  the  iron  hydroxide  and  aluminum 
hydroxide  in  the  usual  manner.  The  calcium  is  precipitated  in  the  boiling  am- 
moniacal  filtrate  with  30  cc.  of  saturated  ammonium  oxalate  solution,  allowing 
the  solution  to  boil  for  one-half  hour.  A  double  precipitation  is  here  advisable 
to  remove  the  last  traces  of  magnesium.  The  calcium  oxalate  is  filtered  off, 
thoroughly  washed  and  determined  volumetrically  by  the  permanganate  method, 
p.  92. 

Magnesium.  Determine  in  the  filtrates  after  removal  of  the  calcium  by 
precipitation  as  magnesium  ammonium  phosphate  and  ignition  to  magnesium 
pyrophosphate  in  the  usual  manner,  p.  255. 

Carbon  Dioxide.    Determine  as  outlined  under  Silica. 

Sulphates.  Dissolve  1  gram  in  concentrated  HC1,  remove  any  insoluble 
residue,  heat  to  boiling  and  precipitate  any  sulphate  as  BaS04,  determining  in  the 
usual  manner.  See  p.  395. 


BARYTES  AND  BLANC  FIXE 

Of  these  two  barium  pigments  used  in  the  manufacture  of  paints,  barytes 
is  the  natural  barium  sulphate,  while  blanc  fixe  is  precipitated  barium  sulphate. 
Their  barium  sulphate  content  should  be  not  less  than  95%. 

The  following  method  may  be  used  for  the  analysis  of  these  pigments: 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

Loss  on  Ignition.  Ignite  1  gram  to  constant  weight.  The  loss  will  be 
reported  as  loss  on  ignition,  and  will  consist  of  free  and  uncombined  water,  carbon 
dioxide  and  organic  matter. 

Barium  Sulphate.  Boil  1  gram  with  dilute  HC1,  evaporate  to  dryness, 
moisten  with  HC1,  add  water,  boil,  filter  and  wash.  Should  lead  be  present 
in  the  insoluble  residue,  as  shown  by  the  action  of  H2S,  treat  the  insoluble  residue 
with  a  little  (1:1)  HC1  and  several  drops  of  H2S04.  Filter,  wash  and  weigh 
the  residue.  Treat  the  ignited  residue  with  H2S04  and  HF,  evaporate  to  dryness 


PAINT  AND   PAINT  PIGMENTS  633 

and  ignite.  The  residue  should  show  no  loss  as  silica.  The  filtrate  is  examined 
for  alumina,  iron,  calcium  and  magnesium  in  the  usual  manner. 

Soluble  Sulphates.  Treat  1  gram  with  20  cc.  cone.  HC1,  dilute  to  200  cc. 
with  hot  water,  boil,  filter,  wash,  add  NH4OH  until  neutral,  make  acid  with 
HC1  and  precipitate  any  sulphate  as  BaS04.  Determine  in  the  usual  manner. 
Calculate  to  CaS04.  If  carbonates  are  present,  calculate  the  remaining  CaO  to 
CaC03.  Any  excess  of  oxide  is  reported  as  CaO. 

Carbon  Dioxide.  Determine  as  outlined  under  silica.  If  any  barium  car- 
bonate is  present,  it  is  determined  in  the  filtrate  from  the  preliminary  HC1 
treatment,  by  precipitation  and  weighing,  as  BaS04.  Any  excess  of  carbon 
dioxide  over  the  barium  is  reported  as  calcium  carbonate. 

ANALYSIS  OF  A  COMPOSITE  WHITE  PAINT 

A  white  paint  may  consist  of  a  mixture  of  any  of  the  preceding  pigments, 
excepting  that  it  is  understood  that  lead  pigments  and  lithopone  are  seldom 
found  together,  owing  to  their  tendency  to  blacken  with  the  formation  of  lead 
sulphide. 

After  separation  from  the  oil  and  other  liquids  as  outlined  above,  the  white 
pigment  mixture  may  be  rapidly  analyzed  by  the  following  method.  It  is,  however, 
often  advisable  to  resort  to  a  qualitative  examination  before  beginning  the  quan- 
titative analysis. 

Insoluble  Residue.  Boil  1  gram  of  the  sample  with  20  cc.  (1:1)  HC1. 
Evaporate  to  dryness,  moisten  the  residue  with  a  few  cc.  of  concentrated  HC1, 
allow  to  stand  a  few  minutes,  dilute  with  hot  water,  boil,  filter  and  wash  the 
insoluble  residue  thoroughly  with  hot  water.  Treat  the  insoluble  residue  with 
(1  :  1)  HC1  and  2  cc.  H2S04  to  remove  the  last  traces  of  lead.  Filter,  wash  and 
weigh  the  insoluble  residue.  Determine  the  silica  by  volatilization  with  H2SOi 
and  HF.  Any  loss  is  reported  as  silica.  Determine  the  BaS04  in  the  residue 
by  boiling  with  dilute  HC1  or  making  a  potassium  bisulphate  fusion.  The 
residue  remaining  after  either  of  these  treatments  is  reported  as  barium  sul- 
phate. 

Total  Lead.  This  constituent  can  be  best  determined  on  a  separate  sample. 
To  1  gram  add  10  cc.  of  cone.  HN03,  boil,  add,  after  cooling,  cone.  H2S04  and 
evaporate  to  strong  S03  fumes.  Dilute  with  water,  allow  to  stand  several 
hours,  filter,  wash  slightly,  dissolve  and  determine  the  lead  volumetrically  as 
outlined  under  Sublimed  White  Lead. 

Lead  can  also  be  determined  on  the  combined  filtrates  from  the  insoluble 
residue.  Precipitate  the  lead  in  an  acid  solution  with  H2S  and  determine  vol- 
umetrically in  the  above  outlined  manner. 

To  determine  whether  both  sublimed  white  lead  and  corroded  white  lead  are 
present,  treat  a  separate  portion  of  the  paint  with  boiling  acetic  acid,  filter  and 
collect  the  insoluble  residue.  Determine  the  lead  either  in  the  filtrate  or  in  the 
insoluble  residue  by  the  volumetric  method.  The  lead  soluble  in  acetic  acid  is 
the  basic  carbonate  of  lead  and  the  lead  oxide  from  the  sublimed  white  lead, 
while  the  lead  sulphate  from  the  sublimed  white  lead  remains  insoluble. 

Alumina  and  Iron  Oxide.  Remove  the  H2S  from  the  filtrate  by  boiling, 
after  removal  of  the  lead,  and  precipitate  the  hydroxides  in  an  ammoniacal 
solution  after  boiling  with  the  addition  of  a  few  drops  of  HN03.  Determine/ 
and  separate  in  the  usual  manner. 


634  PAINT   AND   PAINT   PIGMENTS 

Zinc.  Precipitate  the  zinc  in  the  filtrate  from  the  alumina  and  iron  pre- 
cipitation, after  acidifying  with  acetic  acid,  and  determine  the  zinc  as  outlined 
under  Sublimed  White  Lead  on  p.  623. 

Calcium  and  Magnesium.  Determine  the  calcium  and  magnesium  in  the 
nitrate  from  the  precipitation  of  zinc  sulphide  in  the  usual  manner,  testing,  how- 
ever, first  for  the  presence  of  barium. 

Sulphate.    Determine  as  outlined  under  Zinc  Lead  and  Leaded  Zincs. 

Sulphide.  Should  lithopone  be  present,  separate  the  zinc  oxide  and  zinc 
sulphide  as  outlined  under  Lithopone,  p.  630. 

Carbon  Dioxide.    Determine  as  outlined  under  Silica,  p.  631. 

Calculations.  Silica  is  reported  as  silica,  except  where  alumina  is  present, 
showing  the  presence  of  China  clay.  In  this  case,  calculate  the  alumina  to  clay 
by  the  method  of  Scott. 

Weight  of  Al203X2.5372=weight  of  clay. 

Weight  of  clay  X  0.4667  =  weight  of  Si02  in  clay. 

Any  difference  greater  than  5%  may  be  considered  silica. 

Barium  sulphate  is  reported  as  barium  sulphate  or  as  lithopone,  if  zinc  sul- 
phide is  present,  according  to  the  given  composition  of  lithopone,  70%  barium 
sulphate  and  30%  zinc  sulphide. 

Lead  is  reported  as  Basic  Carbonate  of  Lead  on  the  formula  2PbC03-Pb(OH)j. 

Calculate  lead  soluble  in  acetic  acid,  after  determining  C02  to  basic  lead  car- 
bonate and  any  residual  lead  to  lead  oxide  which,  together  with  the  lead  sulphate 
is  reported  as  Sublimed  White  Lead. 

Should  calcium  sulphate  be  present  the  portion  soluble  in  water  is  examined 
for  lime  or  sulphuric  acid  and  calculated  to  calcium  sulphate,  any  residual  lime 
being  calculated  to  calcium  carbonate  and  any  residual  sulphuric  acid  being  cal- 
culated to  lead  sulphate.  Any  residual  C02  after  calculating  calcium  'carbonate 
is  calculated  to  white  lead  and  any  residual  lead  is  calculated  to  lead  oxide. 

Lead  oxide  should  not  be  reported  except  in  the  presence  of  lead  sulphate. 
Any  large  percentage  of  magnesium  denotes  the  presence  of  asbestine. 


RED  AND  BROWN  PIGMENTS 

These  pigments  are  grouped  under  these  heads: 

The  Lead  Oxide  Pigments — The  Iron  Oxide  and  Manganese  Oxide 
Pigments — The  Mercury  Oxide  Pigments 

RED  LEAD  AND  ORANGE  MINERAL 

These  pigments  in  the  pure  form  are  oxides  of  lead,  of  the  generally  accepted 
form,  Pb304,  being  probably  mixtures  of  lead  monoxide,  and  lead  dioxide.  In 
chemical  composition  they  are  the  same,  the  proportions  of  lead  monoxide  and 
lead  dioxide  varying,  however,  but  by  their  physical  structure  and  color  they  can 
be  readily  differentiated. 

Two  methods  are  given  for  the  analysis  of  this  pigment.  The  first  is  taken 
from  the  method  as  outlined  by  Sub-committee  VIII  of  Committee  D-I.1 

Moisture.    Dry  2  grams  at  105°  for  two  hours. 

1  Proceedings  of  American  Society  for  Testing  Materials,  14,  281-283,  1914. 


PAINT   AND   PAINT   PIGMENTS  635 

Organic  Color.  Boil  2  grams  with  25  cc.  of  95%  ethyl  alcohol,  let  settle, 
decant  off  the  supernatant  liquid;  boil  residue  with  water,  decant  as  before  and 
boil  residue  with  very  dilute  NH4OH.  If  either  the  alcohol,  water  or  NH4OH 
is  colored,  organic  coloring  matter  is  indicated. 

Total  Lead  and  Insoluble  Residue.  Treat  1  gram  with  15  cc.  of  HN03 
(1:1)  and  sufficient  hydrogen  dioxide  to  dissolve  all  the  Pb02  on  warming.  If 
any  insoluble  matter  is  present,  add  25  cc.  of  water,  boil,  filter  and  wash  with 
hot  water.  Insoluble  contains  free  Si02,  and  should  be  examined  for  BaSCX 
and  silicates,  if  appreciable.  To  the  original  solution  or  nitrate  from  insoluble, 
add  20  cc.  of  cone.  H2S04  and  evaporate  to  S03  fumes;  cool  and  determine 
lead  as  lead  sulphate  either  gravimetrically  or  volumetrically.  If  the  sample 
contains  soluble  barium  salts,  the  PbS04  will  contain  BaS04  and  should  be 
treated  with  acid-ammonium  acetate  solution,  the  lead  being  determined  in  the 
nitrate. 

Determination  of  Lead  Peroxide  (PbO2)  and  True  Red  Lead  (Pb3O4). 
(Method  of  Diehl,1  modified  by  Topf  2 — not  applicable  when  substances  are 
present,  other  than  oxides  of  lead,  that  liberate  iodine  under  conditions  given.) 

Weigh  1  gram  of  finely  ground  sample  into  a  200-cc.  Erlenmeyer  flask,  add  a 
few  drops  of  distilled  water  and  rub  the  mixture  to  a  smooth  paste  with  a  glass 
rod  flattened  on  end.  Mix  in  a  small  beaker  30  grams  of  C.P.  "  Tested  Purity  " 
crystallized  sodium  acetate,  2.4  grams  of  C.P.  potassium  iodide,  10  cc.  of  water 
and  10  cc.  of  50%  acetic  acid;  stir  until  all  is  liquid,  warming  gently;  if  neces- 
sary add  2  to  3  cc.  of  H20,  cool  to  room  temperature  and  pour  into  the  flask  con- 
taining the  red  lead.  Rub  with  the  glass  rod  until  nearly  all  the  red  lead  has  been 
dissolved;  add  30  cc.  of  water  containing  5  or  6  grams  of  sodium  acetate,  and 
titrate  at  once  with  decinormal  sodium  thiosulphate,  adding  the  latter  rather 
slowly  and  keeping  the  liquid  constantly  in  motion  by  whirling  the  flask.  When 
the  solution  has  become  light  yellow,  rub  any  undissolved  particles  up  with  the 
rod  until  free  iodine  no  longer  forms,  wash  off  rod,  add  the  sodium  thiosulphate 
solution  until  pale  yellow,  add  starch  solution  and  titrate  until  colorless,  add 
decinormal  iodine  solution  until  blue  color  is  just  restored  and  subtract  the 
amount  used  from  the  volume  of  thiosulphate  that  had  been  added. 

Calculation.  The  iodine  value  of  the  sodium  thiosulphate  solution  multi- 
plied by  0.94193  =Pb02;  the  iodine  value  multiplied  by  2.69973  =Pb304;  the 
Pb02  value  multiplied  by  2.86616  =Pb304. 

Sodium  Thiosulphate  Solution  (decinormal) .  Dissolve  24.83  grams  of 
C.P.  sodium  thiosulphate,  freshly  pulverized  and  dried  between  filter  paper, 
and  dilute  with  water  to  1  liter  at  a  temperature  at  which  the  titrations  are  to  be 
made.  The  solution  should  be  made  with  well-boiled  H20,  free  from  C02,  or 
let  stand  eight  to  fourteen  days  before  standardizing.  Standardize  with  pure, 
resublimed  iodine,  as  described  in  the  chapter  on  Iodine,  page  204,  and  also  against 
pure  potassium  iodate.  The  two  methods  of  standardization  should  agree  within 
0.1%  on  iodine  value. 

Starch  Solution.  Two  to  3  grams  of  potato  starch  are  stirred  up  with  100  cc. 
of  1%  salicylic  acid  solution,  and  the  mixture  boiled  till  the  starch  is  practically 
dissolved  and  then  diluted  to  1  liter. 

The  red  lead  may  also  be  examined  for  zinc,  carbon  dioxide,  and  soluble 
sulphate. 

1  Dingl.  Polyt.  Jour.,  246,  196. 

2  Zeitschrift  fur  analytische  Chemie,  26,  296. 


636 


PAINT   AND   PAINT   PIGMENTS 


The  second  method  for  determination  of  the  lead  peroxide  or  true  red  lead 
content  is  somewhat  shorter.1 

Treat  1  gram  in  a  beaker  with  15  cc.  of  nitric  acid,  sp.gr.  1.2  (110  cc.  nitric 
acid,  sp.gr.  1.42  to  100  cc.  of  water).  Stir  the  sample  until  all  trace  of  red  color 
has  disappeared.  Add  from  a  calibrated  pipette  or  burette  exactly  10  cc.  of 
dilute  hydrogen  dioxide  (1  part  of  3%  hydrogen  dioxide  to  3.5  parts  of  water). 
Add  about  50  cc.  of  hot  water  and  stir  until  all  the  lead  dioxide  has  passed  into 
solution.  In  the  case  of  some  coarsely  ground  oxides  the  contents  of  the  beaker 
may  have  to  be  gently  heated  to  effect  complete  solution.  After  the  oxide  has 
completely  passed  into  solution,  dilute  with  hot  water  to  about  250  cc.  volume 
and  titrate  directly  with  a  standard  potassium  permanganate  solution,  having 
an  iron  value  of  0.005.  Titrate  to  the  faint  pink  permanganate  color.  A  blank 
titration  on  the  hydrogen  dioxide  solution  must  now  be  made. 

Into  a  beaker  pour  15  cc.  of  nitric  acid  of  abovo  strength  and  add  exactly 
the  same  amount  of  hydrogen  dioxide  (10  cc.).  Dilute  to  250  cc.  with  hot  water 
and  titrate  with  standard  potassium  permanganate  solution  to  a  faint  pink 
color. 

The  difference  between  the  number  of  cc.  of  potassium  permanganate  required 
for  the  blank  titration  and  the  number  required  for  the  red  lead  titration  is  the 
amount  required  for  the  hydrogen  dioxide  which  was  reacted  on  by  the  red  lead. 
The  difference  between  the  two  amounts  of  potassium  permanganate  required 
multiplied  by  3.058  grams  gives  the  percentage  of  red  lead  present.  The  dif- 
ference multiplied  by  1.067  gives  the  percentage  of  Pb02  present. 

VERMILION 

The  following  portion  of  Walker's  2  method,  will  suffice  for  the  examination 
of  this  pigment.  Should  the  analyst  desire  to  determine  the  sulphide  of  mercury 
present  or  make  a  more  complete  examination — reference  may  be  made  to  the 
original  method. 

True  vermilion,  or,  as  it  is  generally  called,  English  vermilion,  is  sulphide 
of  mercury.  On  account  of  its  cost  it  is  rarely  used  in  paints,  and  is  liable  to  gross 
adulteration.  It  should  show  no  bleeding  on  boiling  with  alcohol  and  water  and 
no  free  sulphur  by  extraction  with  carbon  disulphide.  A  small  quantity  mixed 
with  five  or  six  times  its  weight  of  dry  sodium  carbonate  and  heated  in  a  tube 
should  show  globules  of  mercury  on  the  cooler  portion  of  the  tube.  The  best 
test  for  purity  is  the  ash,  which  should  be  not  more  than  one-half  of  1%.  Make 
the  determination  in  a  porcelain  dish  or  crucible,  using  2  grams  of  the  sample. 
Ash  in  a  mufflle  or  in  a  hood  with  a  very  good  draft,  as  the  mercury  fumes  are 
very  poisonous.  It  is  seldom  necessary  to  make  a  determination  of  the  mercury. 

Genuine  vermilion  is  at  the  present  time  little  used  in  paints.  Organic 
lakes  are  used  for  most  of  the  brilliant  red,  scarlet  and  vermilion  shades.  These 
organic  coloring  matters  are  sometimes  precipitated  on  red  lead,  orange  mineral 
or  zinc  oxide;  but  as  a  usual  thing  the  base  is  barytes,  whiting  or  china  clay. 
Paranitraniline  red,  a  compound  of  diazotized  paranitraniline  and  beta-naphthol, 
is  largely  employed;  but  a  number  of  colors  may  be  used. 

Paranitraniline  red  is  soluble  in  chloroform.     It  is  also  well  to  try  the  solvent 

1 "  Analysis  of  Lead  and  Its  Compounds,"  Schaeffer  and  White,  pp.  25-27. 
s  P.  H.  Walker,  Bulletin  109,  Revised,  Bureau  of  Chemistry,  U.  S.  Dept.  of  Agri., 
pp.  31-33. 


PAINT  AND   PAINT  PIGMENTS  637 

action  on  different  reds,  of  sodium  carbonate,  etc.  The  amount  of  organic  pig- 
ment present  in  such  reds  is  generally  very  small,  and  when  it  cannot  be  deter- 
mined by  ignition  owing  to  the  presence  of  lead,  zinc  or  carbonate,  it  is  best  deter- 
mined by  difference. 

IRON  OXIDES 

The  iron  oxides  and  manganese  oxide  pigments  include  the  ochres,  umbers, 
siennas,  Venetian  red,  metallic  brown,  Indian  red  and  Tuscan  red. 

In  analyzing  these  pigments,  the  following  constituents  are  sought;  moisture, 
loss  on  ignition,  insoluble  residue,  iron  oxide,  manganese  dioxide,  calcium  and 
magnesium  oxides  and  sulphur  trioxide. 

Owing  to  the  similarity  of  the  methods  used  for  the  analysis  of  these  pigments 
to  those  used  in  the  analysis  of  iron  ores,  the  analyst  is  referred  to  p.  211  on  the 
Analysis  of  Iron  Ores,  or  to  the  method  of  Walker.1 


BLUE  PIGMENTS 

In  examining  blue  pigments,  only  three  are  found  of  commercial  importance 
in  the  manufacture  of  paints;  namely,  Prussian  blue,  ultramarine  blue  and  sub- 
limed blue  lead. 

Sublimed  blue  lead  is  the  fume  product  resulting  from  the  smelting  of  lead 
ores.  In  composition  it  consists  of  lead  sulphate,  lead  sulphide,  lead  sulphite, 
lead  oxide  and  zinc  oxide,  with  occasional  traces  of  carbon.  It  is  finding  its  great- 
est use  as  an  inhibitive  pigment  for  the  protection  of  iron  and  steel.  Its  color 
is  a  bluish  gray. 

Prussian  blue  is  the  double  iron  and  potassium  salt  of  hydroferrocyanic  and 
hydroferricyanic  acids. 

Ultramarine  blue  is  essentially  a  silicate  and  sulphide  of  sodium  and  aluminum. 

ULTRAMARINE  BLUE 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

Silica.  Digest  1  gram  with  30  cc.  of  concentrated  HC1,  taking  care  to 
avoid  spattering.  Evaporate  to  dryness,  dehydrate,  moisten  with  cone.  HC1, 
dehydrate  a  second  time,  dilute,  filter,  and  determine  the  silica  by  volatilization 
with  H,S04  and  HF. 

Aluminum  Oxide.  In  the  filtrate  from  the  silica,  precipitate  the  aluminum 
hydroxide  and  determine  in  the  usual  manner.  Report  as  aluminum  oxide. 

Sodium  Oxide.  The  filtrate,  after  the  removal  of  the  aluminum  hydroxide  is 
acidified  with  H2S04.  Evaporate  to  dryness,  ignite  at  a  low  red  heat,  and  weigh 
the  sodium  sulphate.  Calculate  to  sodium  oxide. 

Total  Sulphur.  Fuse  1  gram  with  a  mixture  of  KN03  and  Na2C03.  Dissolve 
the  fused  mass  in  HC1,  boil  with  cone.  HN03  for  one-half  hour,  remove  the 
insoluble  residue  and  determine  the  sulphuric  acid  in  the  usual  way.  See  p.  628. 

Sulphur  Present  as  Sulphate.  Dissolve  1  gram  in  dilute  HC1  and  boil 
until  all  the  hydrogen  sulphide  is  removed.  Filter  off  the  insoluble  residue  and 
determine  the  sulphate  in  the  filtrate. 

1  Bulletin  109,  Revised,  Bureau  of  Chemistry,  U.  S.  Dept.  Agri.,  pp.  33-34. 


638  PAINT   AND  PAINT  PIGMENTS 

PRUSSIAN  BLUE— (CHINESE  BLUE)— ANTWERP  BLUE 

Moisture.  Heat  2  grams  at  105°  C.  for  two  hours.  Dry  Prussian  blue 
should  contain  less  than  7%  moisture. 

Nitrogen.    Determine  the  nitrogen  present  by  the  Kjeldahl-Gunning  method. 

Iron  and  Aluminum  Oxides.  Ignite  1  gram  at  a  low  temperature,  sufficient 
to  decompose  all  the  blue,  but  not  to  render  the  iron  difficultly  soluble.  Digest 
the  residue  with  (1  :  1)  HC1.  Any  insoluble  residue  is  examined  for  silica, 
barium  sulphate  and  alumina.  A  pure  Prussian  blue  should  show  no  insoluble 
residue.  The  filtrate  is  examined  for  alumina,  iron  and  calcium  in  the  usual 
way. 

An  aliquot  portion  of  the  filtrate  after  the  removal  of  the  calcium  is  examined 
for  the  alkaline  metals.  Calculate  any  alkaline  metal  present  to  sulphate. 

Sulphuric  Acid.  Determine  the  sulphuric  acid  in  an  aliquot  portion  after 
removal  of  the  calcium. 

Commercial  Analysis.  The  method  of  Parry  and  Coste1  is  sufficiently 
accurate  to  determine  the  Prussian  blue  in  most  instances. 

By  multiplying  the  percentage  of  iron  by  3.03  or  the  percentage  of  nitrogen 
by  4.4,  the  percentage  of  Prussian  blue  is  directly  determined. 

In  the  case  of  Chinese  blue,  tin  salts  are  frequently  found.  The  presence 
of  these  salts  should  be  sought  by  a  qualitative  examination. 

SUBLIMED  BLUE  LEAD2 

Total  Lead.  The  total  lead  content  is  determined  by  the  volumetric  method 
for  lead  as  outlined  under  Sublimed  White  Lead. 

Total  Sulphur.  Treat  0.5  gram  with  10  cc.  of  water  and  a  few  cc.  of  bromine 
water.  Boil  gently  until  all  the  bromine  has  passed  off.  Dilute  with  water, 
add  another  portion  of  bromine  water,  boil,  and  continue  the  treatment  until 
the  sediment  has  become  white  in  color.  Add  8  cc.  of  nitric  acid,  evaporate 
until  the  brown  fumes  of  nitric  acid  have  disappeared,  dilute  with  water  and  add 
an  excess  of  sodium  carbonate.  Determine  as  outlined  under  Zinc  Lead  and 
Leaded  Zinc. 

Lead  Sulphate.  On  a  separate  sample  determine  the  sulphate  directly  as 
outlined  under  Zinc  Lead  and  Leaded  Zinc,  without  any  preliminary  treatment 
for  the  oxidation  of  sulphites  and  sulphides. 

Lead  Sulphite.  Boil  1£  grams  with  3  grams  of  sodium  carbonate.  Allow 
to  stand,  filter  and  thoroughly  wash.  Treat  the  filtrate  with  bromine  water  as 
outlined  under  Total  Sulphur  and  determine  the  combined  sulphur  present  as 
sulphate  and  sulphite.  Deduct  the  amount  present  as  sulphate  and  calculate  to 
sulphite. 

Lead  Sulphide.  Deduct  the  sulphur  present  as  sulphate  and  sulphite  from 
the  total  sulphur  and  report  the  difference  as  lead  sulphide. 

Lead  Carbonate.  Determine  any  C02  present  by  the  evolution  method  and 
calculate  to  lead  carbonate.  See  p.  103. 

Lead  Oxide.  Deduct  the  lead  present  as  sulphate,  sulphite,  sulphide  and 
carbonate  from  the  total  lead  and  report  the  difference  as  lead  oxide. 

1  The  Analyst,  21,  225-230,  1896. 

•"The  Chemical  Analysis  of  Lead  and  its  Compounds,"  Schaeffer  and  White, 
pp.  22-24. 


PAINT  AND   PAINT   PIGMENTS  639 

Zinc  Oxide.  Determine  the  zinc  volumetrically  as  outlined  under  Sublimed 
White  Lead  and  report  as  zinc  oxide. 

Carbon  and  Volatile  Matter.  Ignite  the  sample  in  a  partially  covered 
crucible  at  a  low  heat  for  two  hours.  Report  the  difference  in  weight  as  carbon 
and  volatile  matter. 

YELLOW  AND  ORANGE  PIGMENTS 

Chrome  Yellows — American  Vermilion— Basic  Lead  Chromate 

The  pigments  under  this  class  all  contain  chromates,  with  the  exception  of 
orange  mineral,  which  is  analyzed  as  under  Red  Lead.  Frequently  they  contain 
lead  sulphate  and  sometimes  lead  carbonate.  A  pure  chrome  yellow  should  con- 
tain only  lead  chromate  and  insoluble  lead  compounds.  Owing  to  the  frequent 
use  of  organic  colors  to  brighten  up  the  pigment,  it  is  essential  that  a  test  be  made 
for  organic  colors  as  outlined  under  Vermilion. 

The  analysis  of  these  pigments  is  carried  out  in  the  following  manner: 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

Insoluble  Residue.  Treat  1  gram  with  25  cc.  of  concentrated  HC1,  boil 
and  during  the  boiling  add  a  few  drops  of  alcohol,  one  at  a  time.  The  solution 
is  diluted  to  100  cc.,  the  boiling  is  continued  for  ten  minutes  and  any  insoluble 
residue  is  filtered  off,  thoroughly  washed  and  examined  for  silica,  barium  sulphate 
and  alumina. 

Lead.  The  solution  is  nearly  neutralized  with  NH4OH  and  the  lead  is  pre- 
cipitated as  PbS  with  H2S.  Filter  off  the  precipitate  of  PbS,  dissolve  in  HN03, 
add  H2S04,  boil  to  strong  fumes  and  determine  as  outlined  under  Sublimed  White 
Lead  or  weigh  as  PbS04. 

Chromium.  The  filtrate  from  the  lead  precipitation  is  boiled  until  all  the 
H2S  is  driven  off.  The  solution  is  rendered  alkaline  with  NH4OH  and  the  chro- 
mium is  precipitated  and  determined  as  chromic  oxide.  Calculate  to  chromic 
anhydride. 

Zinc,  Calcium  and  Magnesium.  Precipitate  the  zinc  in  the  filtrate  with 
H2S  and  determine  as  previously  outlined,  either  volumetrically  or  gravimetrically. 

In  the  filtrate  from  the  zinc  precipitation,  determine  the  calcium  and  mag- 
nesium in  the  usual  manner. 

If  any  carbonates  are  present,  determine  by  the  evolution  method. 

Sulphuric  Acid.  Determine  the  total  sulphate  as  outlined  under  Zinc  Lead 
and  Leaded  Zinc  on  p.  627. 

Calculations.  Any  chromic  anhydride  is  calculated  to  lead  chromate,  sul- 
phuric acid  to  lead  sulphate,  if  calcium  sulphate  is  absent,  and  any  residual  lead 
is  calculated  to  lead  oxide. 

GREEN  PIGMENTS 

Chrome  Green 

Green  pigments  are  usually  mixtures  of  chrome  yellow  and  Prussian  blue, 
though  organic  color  is  sometimes  present,  which  may  be  determined  by  an 
extraction  with  alcohol. 

A  microscopic  examination  should  be  made  to  determine  whether  the  green 
is  a  combined  precipitation  product,  which  is  of  the  greater  value,  or  one  mixed 


640  PAINT   AND   PAINT   PIGMENTS 

after  separate  precipitation.  A  good  green  will  show  the  presence  of  green  and 
blue  particles,  while  a  poor  green  will  show  yellow  and  blue  particles  mixed  with 
green.  The  analysis  may  be  carried  out  as  follows : 1 

Moisture.    Heat  2  grams  at  105°  C.  for  two  hours. 

Insoluble  Residue.  Heat  1  gram  at  a  low  heat  until  the  blue  color  has  been 
decomposed,  keeping  the  temperature  sufficiently  low  so  as  not  to  render  any  of 
the  iron  or  lead  chromate  insoluble.  Determine  the  insoluble  residue  as  outlined 
under  Yellow  Pigments,  on  p.  639. 

Lead.    Determine  as  outlined  under  Yellow  Pigments. 

Iron,  Alumina  and  Chromium.  All  the  H2S  is  expelled  from  the  nitrate 
after  the  lead  precipitation  by  boiling.  Add  a  few  drops  of  HN03,  boil  a  few 
minutes  and  precipitate  the  aluminum,  iron  and  chromium  hydroxides  with 
NH4OH.  Filter,  wash,  dissolve  the  precipitate  in  HC1,  and  make  up  the  solution 
to  a  definite  volume. 

In  one  portion  the  three  hydroxides  are  precipitated  together  with  NH4OH 
and  weighed.  Another  portion  is  treated  in  a  flask  with  an  excess  of  KOH  and 
bromine  water  until  the  iron  hydroxide  has  assumed  its  characteristic  reddish- 
brown  color.  Dilute  with  water,  filter,  wash  and  determine  the  iron  in  the 
usual  way.  Render  the  filtrate  from  the  iron  precipitation  acid  with  HN03, 
precipitate  the  aluminum  hydroxide  with  NH4OH  and  weigh  as  A1203. 

Chromium  is  determined  in  the  filtrate  by  reduction  to  a  chromic  salt  with 
HC1  and  alcohol,  precipitated  with  NH4OH  and  weighed  as  oxide.  Any  method 
for  the  separation  of  the  above  hydroxides  may  be  used  in  place  of  the  one 
outlined. 

Calcium  and  Magnesium.  These  constituents  are  determined  in  the  filtrate 
from  the  precipitation  of  the  above  hydroxides. 

Sulphuric  Acid.  One  gram  after  ignition  until  all  the  blue  has  been  decom- 
posed, is  dissolved  in  30  cc.  of  cone.  HC1,  diluted  with  water,  boiled,  filtered, 
and  washed.  The  sulphuric  acid  is  determined  in  the  filtrate. 

Nitrogen.    Determine  as  outlined  under  Prussian  Blue. 

Calculation.  The  Prussian  blue  is  determined  by  multiplying  the  iron 
found  by  3.03  or  the  nitrogen  formed  by  4.4.  The  sulphate  is  calculated  to  lead 
sulphate  and  calcium  sulphate,  should  calcium  be  present,  and  the  chromium  to 
lead  chromate. 

BLACK  PIGMENTS 

The  black  pigments  include  those  which  contain  carbon  as  their  essential 
constituent.  The  introduction  of  many  black  pigments  which  are  made  from 
asphaltic  and  coal-tar  mixtures  complicates  their  chemical  analysis.  For  those 
pigments  which  contain  coal-tar  mixtures,  recourse  may  be  had  to  works  2 
covering  this  matter  thoroughly. 

The  analysis  of  the  simple  black  pigments  may  be  carried  out  in  the  following 
way: 

Moisture.    Dry  2  grams  at  105°  C.  for  two  hours. 

Oil.    Extract  2  grams,  with  ether  in  a  fat-extraction  apparatus. 

Carbon.    Determine  the  carbon  by  difference  after  determining  the  moist- 

1 "  The  Analysis  of  Paints,"  Gardner  and  Schaeffer,  pp.  36-37. 
8  Allen's  "  Commercial  Organic  Analysis,"  4th  Edition;    "  The  Analysis  of  Paints," 
Gardner  and  Schaeffer. 


PAINT   AND   PAINT   PIGMENTS  641 

ure,  oil  and  ash.  For  an  exact  determination  of  carbon  make  a  combustion  test, 
absorbing  the  carbon  dioxide  in  soda-lime  or  caustic  potash  as  usual. 

Ash.  Ignite  2  grams  to  a  bright  red  heat  until  all  the  carbon  is  driven  off. 
If  graphite  is  present,  the  ignition  must  be  carried  out  with  the  aid  of  oxygen. 
Should  carbonate  be  present,  mix  the  ash  with  a  small  amount  of  ammonium 
carbonate  and  again  ignite,  thus  reconverting  to  carbonate  any  oxide  which  may 
have  been  decomposed. 

Analysis  of  Ash.  The  ash  is  boiled  with  concentrated  HC1  and  the  insoluble 
residue  determined  in  the  usual  manner.  The  nitrate  is  examined  for  calcium, 
magnesium  and  phosphoric  acid. 

Calculate  the  magnesium  to  phosphate,  any  residual  phosphoric  acid  to 
calcium  phosphate  and  any  residual  calcium  to  carbonate. 


COMPLEX  COMPOUNDS— FERRO  AND  FERRI  CYANIDES 
Hydroferrocyanic  Acid 

One  gr.im  of  the  hydroferrocyanide  in  ICO  cc.  of  water  acidified  with  10  cc. 
of  sulphuric  acid  is  titrated  in  a  casserole  with  standard  potassium  permanganate 
to  a  permanent  pink  color.  The  end-point  is  poor,  so  that  it  is  advisable  to 
standardize  the  permanganate  against  pure  potassium  ferrocyanide. 

Reaction:  2H4Fe(CN)d+0  =  H20+2H3Fe(CN)3 

One  cc.  N  KMn04  =0.3683  gram  K4Fe(CN)6. 

Hydroferricyanic  Acid 

Ten  grams  of  hydroferricyanide  are  dissolved  in  water,  the  solution  made 
alkaline  with  KOH  and  heated  to  boiling  and  an  excess  of  ferrous  sulphate  solu- 
tion added.  The  yellowish  brown  ftrric  hydroxide  turns  black  with  excess  of 
ferrous  salt.  The  solution  is  diluted  to  exactly  5CO  cc.  and  50  cc.  of  a  filtered 
portion  titrated  with  potassium  permanganate. 

One  cc.  N  KMn04  =  .3292  gram  K8Fe(CN)6. 


CEMENT 

RICHARD  K.  MEADE  * 

ANALYSIS  AND  TESTING  OF  CEMENTS 

The  tests  ordinarily  applied  to  Portland  cement  are  as  follows: 

Fineness. 
Specific  gravity. 
Setting  time. 
Soundness. 
Tensile  strength. 

Chemical  analysis  is  also  made,  particular  attention  being  paid  to  the  deter- 
mination of  magnesia,  sulphur  trioxide,  and  loss  on  ignition.  As  a  general 
rule,  however,  it  may  be  said  that  so  far  as  the  consumer  is  concerned,  more 
attention  is  paid  to  the  physical  tests  than  to  chemical  analysis. 

Standard  specifications  covering  the  requirements  for  cement,  both  chem- 
ical and  physical,  have  been  adopted  by  the  American  Society  for  Testing 
Materials,  and  by  the  U.  S.  Government.  The  former  are  generally  recognized 
by  cement  users  as  the  standard  requirements,  while  the  latter  are  used  by  the 
various  branches  of  the  federal  government. 

The  methods  of  making  these  tests  follow. 

PHYSICAL  TESTING 

Fineness.  The  fineness  of  cement  is  usually  determined  by  sieving  a  weighed 
portion  through  sieves  having  openings  of  definite  sizes  and  observing  the  per- 
centage of  residue  caught  upon  these.  The  standard  sieves  for  cement  testing 
are  the  No.  100  and  the  No.  200.  The  No.  100  cement  test  sieve  has  100 
openings  to  the  linear  inch  and  is  called  the  100-mesh  sieve.  Since  the  size  of 
these  openings  will  be  influenced  by  the  size  of  the  wire  used  to  weave  the  cloth 
of  the  sieve,  the  No.  100  sieve  is  made  of  wire  having  a  diameter  of  0.0045  in. 
As  it  is  practically  an  impossibility  to  obtain  wire  having  exactly  100  meshes 
to  the  linear  inch,  any  sieve  will  be  considered  standard  which  contains  from 
96  to  100  meshes  to  the  linear  inch  and  is  made  of  brass  wire  of  the  proper  diam- 
eter (0.0045  inch).  Similarly  the  No.  200  sieve  (200-mesh)  should  contain 
between  192  and  208  meshes  to  the  linear  inch  and  be  made  of  brass  wire  0.0021 
in.  in  diameter.  The  spacing  should  be  regular,  and  in  purchasing  a  new  lot 
of  sieves  the  number  of  meshes  in  each  should  be  counted,  and  the  cloth  examined 
for  irregularities.  The  sieves  should  be  about  8  ins.  in  diameter,  2|  ins.  deep 
and  provided  with  a  cover  and  a  pan  2  ins.  deep.  The  standard  specifications 

1  Chemical  and  Industrial  Engineer,  Baltimore,  Md. 
642 


CEMENT 


643 


and  the  U.  S.  Government  specifications  require  the  following  degree  of  fine- 
ness: 

. 

Cement. 

Residue  on  No.  200  sieve,  not  over 22% 

There  are  now  no  longer  any  requirements  as  to  fineness  where  listed  with 
the  No.  100  sieve. 

The  method  of  making  the  test  is  as  follows :  The  cement  to  be  tested  is  dried 
for  one  hour,  in  an  air  bath,  at  a  temperature  of  from  100  to  110°  C.  (212  to 
230°  F.) ;  50  grams  of  this  are  then  weighed  into  the  No.  200  sieve,  which  should 
also  contain  a  few  large  (B.B.  size)  buck-shot  and  have  its  pan  attached.  The 
cover  is  now  placed  on  the  sieve  and  the  latter  held  in  one  hand,  in  a  slightly 
inclined  position,  and  moved  forward  and  backward,  at  the  same  tune  striking 
the  side  gently  with  the  palm  of  the  other  hand,  at  the  rate  of  about  150  strokes 
per  minute.  The  operation  is  continued  until  not  more  than  one-tenth  of  1% 
(0.05  gram)  passes  through  after  one  minute  of  continuous  sieving.  The  residue 
is  then  weighed,  placed  on  the  No.  100  sieve  and  the  operation  repeated.  The 
results  should  be  reported  to  the  nearest  tenth  of  1%. 

Specific  Gravity.  The  standard  instrument  for  determining  specific  gravity 
is  the  one  designed  by  Le  Chatelier,  which  is  shown  in  Fig.  93.  This  consists 
of  a  flask  of  120  cc.  capacity,  the  neck 
of  which  is  about  20  cm.  long.  In  the 
middle  of  this  neck  is  a  bulb,  above  and 
below  which  are  two  marks.  The 
volume  between  these  marks  is  20  cc., 
and  the  neck,  which  has  a  diameter  of 
9  cm.,  is  graduated  into  tenths  of  cc. 
above  the  bulb. 

In  making  the  determination,  which 
can  be  done  in  either  of  two  ways, 
benzine  (62°  Be*,  naphtha)  or  kerosene 
free  from  water  should  be  used,  and  the 
sample  of  cement  should  be  dried  for 
at  least  one  hour  at  from  100  to  110°  C. 
and  cooled  to  room  temperature.  To 
make  the  test  fill  the  flask  to  the  mark 
E  with  the  liquid,  next  weigh  out 
exactly  64  grams  of  cement 'and  intro- 


FIG.  93. 
Le  Chatelier's  Specific  Gravity  Apparatus. 


duce  into  the  neck  of  the  flask  by  means  of  a  funnel.  The  funnel  stem  should 
reach  below  the  mark,  F,  on  the  stem,  so  that  should  any  of  the  liquid  fall  against 
the  side  of  the  neck,  it  will  be  below  the  space  eventually  occupied  by  the  liquid. 
The  cement  is  added  cautiously  towards  the  last  until  the  liquid  fills  the  bulb, 
C,  and  rises  to  the  mark,  F,  on  the  stem.  The  remainder  of  the  cement  is  then 
weighed,  and  from  this  the  weight  of  cement  which  displaces  20  cc.  is  calculated. 
From  which 

Difference 
Specific  gravity  = — . 

Instead  of  the  above  method  the  operator  may  add  the  entire  64  grams  of 
cement.    This  will  bring  the  surface  of  the  liquid  to  one  of  the  divisions  on  the 


644 


CEMENT 


neck  above  the  mark,  F.    This  reading  on  the  neck  plus  20  will  give  the  number 
of  cc.  displaced  by  64  grams  of  cement.     Then: 


Specific  gravity  = 


64 


20+ Reading  on  neck 


Care  must  be  taken  to  keep  the  temperature  of  the  liquid  constant  during 
the  test. 

The  standard  specifications  require  a  specific  gravity  of  at  least  3.10. 
Normal  Consistency.  In  order  to  properly  make  the  pastes  and  mortars 
used  in  the  following  tests,  the  amount  of  water  to  be  used  to  make  a  paste  or 
mortar  of  a  definite  state  of  plasticity,  called  "  Normal  Consistency,"  must  be 
determined.  The  "standard  specification "  prescribes  for  doing  this  the  Vicat 
needle.  This  consists  of  a  frame,  K,  Fig.  94,  bearing  a  movable  rod,  L,  with 
the  cup,  A,  at  one  end,  and  at  the  other,  the  cylinder,  B,  1  cm.  (0.39  in.)  in 

diameter,  the  cap,  rod,  and  cylinder 
weighing  300  grams  (10.58  oz.).  The 
rod,  which  can  be  held  in  any  desired 
position  by  a  screw,  F,  carries  an  indi- 
cator, which  moves  over  a  scale  (grad- 
uated to  centimeters)  attached  to  the 
frame,  K.  The  paste  is  held  by  a 
conical,  hard  rubber  ring,  /,  7  cm. 
(2.76  ins.)  in  diameter  at  the  base, 
4  cm.  (1.57  ins.)  high,  resting  on  a 
glass  plate,  «/,  about  10  cm.  (3.894 
ins.)  square. 

Five  hundred  grams  of  cement  are 
placed  on  the  mixing  slab,  which 
should  be  about  24  ins.  square,  and 

of    plate    glass    or    sheet    brass.    A 

,    VJCAT  NEEDLET  .  crater  is  then  formed  in  the  center, 

FIG.  94.  into  which  the  proper  percentage  of 

clean  water  is  poured,  and  the  material 

turned  into  this  crater  by  the  aid  of  a  trowel.  As  soon  as  the  water  has  been 
absorbed,  which  should  not  require  more  than  one  minute,  the  operation  is  com- 
pleted by  a  vigorous  kneading  with  the  hands,  for  one  and  a  half  minutes,  the 
process  being  similar  to  that  used  in  kneading  dough.  A  sand-glass  affords  a 
convenient  guide  for  the  time  of  kneading.  The  hands  should  be  protected  by 
rubber  gloves. 

The  paste  is  now  formed  into  a  ball,  pressed  into  the  rubber  ring,  through 
the  larger  opening,  smoothed  off  and  placed  (on  its  large  end)  on  a  glass  plate 
and  the  smaller  end  smoothed  off  with  a  trowel.  The  paste,  confined  in  the  ring, 
and  resting  on  the  glass  plate,  is  placed  under  the  rod  having  the  cylinder, 
which  is  brought  in  contact  with  the  surface  and  quickly  released.  The  paste 
is  of  normal  consistency  when  the  cylinder  penetrates  to  a  point  in  the  mass 
10  mm.  below  the  top  of  the  ring.  Great  care  should  be  taken  to  fill  the  ring 
exactly  to  the  top. 

Probably  the  majority  of  cement  testers  determine  normal  consistency  by 
the  ball  test.  This  consists  in  forming  the  paste  into  a  ball  and  dropping  it 


CEMENT 


645 


onto  the  table  from  a  height  of  18  ins.  If  of  normal  consistency  the  ball  will 
neither  flatten  nor  crack — the  former  if  too  wet  and  the  latter  if  too  dry.  Most 
cements  require  about  20  to  24%  of  water  for  normal  consistency. 

The  proper  percentage  of  water  for  sand  mortar  is  found  from  the  following 
table,  the  first  column  of  which  gives  the  percentage  of  water  found  by  trial 
as  above  to  give  normal  consistency,  and  the  second  column  shows  the  per- 
centage of  water  for  sand  mortar. 


PERCENTAGE  OF  WATER  FOR  STANDARD  SAND  MORTAR 


One  cement, 

One  cement, 

Neat. 

three  standard 

N«at. 

three  standard 

Ottawa  sand. 

Ottawa  sand. 

15 

9.0 

23 

10.3 

16 

9.2 

24 

10.5 

17 

9.3 

25 

10.7 

18 

9.5 

26 

10.8 

19 

9.7 

27 

11.0 

20 

9.8 

28 

11.2 

21 

10.0 

29 

11.3 

22 

10.2 

30 

11.5 

Setting  Time.  In  making  the  test,  a  paste  of  normal  consistency  is  moulded 
and  placed  under  the  rod,  L,  Fig.  94,  as  described  above;  this  rod,  bearing  the 
cap,  D,  at  one  end  and  needle,  H,  1  mm.  (0.039  in.)  in  diameter,  at  the  other, 
weighing  300  grams  (10.58  oz.).  The  needle  is  then  carefully  brought  in  con- 
tact with  the  surface  of  the  paste  and  quickly  released. 

The  cement  has  its  initial  set  when  the  needle  ceases  to  pass  a  point  5  mm. 
above  the  glass  plate,  in  one-half  minute  after  being  released,  and  its  final  set 
the  moment  the  needle  ceases  to  sink  visibly  into  the  mass. 

A  simpler  test,  devised  by  Gen.  Gilmore,  is  much  more  used  than  the  above 
and  consists  of  mixing  cakes  of  neat  cement, 
3  ins.  in  diameter  and  \  in.  thick,  to  the 
consistency  shown  by  the  ball  test  and 
observing  when  they  will  bear  a  needle  -^  in. 
in  diameter  weighted  with  |  pound.  This 
is  noted  at  the  initial  set.  The  final  set  is 
the  time  after  which  they  will  bear  a  needle 
-£%  in.  in  diameter  weighted  with  1  Ib.  In 
both  cases  the  set  is  the  time  expressed  in 
minutes  between  the  mixing  of  the  mortar 
and  the  failure  of  the  needle  to  penetrate 
the  surface. 

The  standard  specifications  call  for  a  min- 
imum initial  set  of  45  minutes,  when  the  Vicat 

needle  is  used  or  sixty  minutes  where  the  Gilmore  needle  is  used.  The  final  set 
shall  be  attained  within  ten  hours. 

?  Fig.  95  shows  the  Gilmore  needles.  The  pats  should  be  made  with  a  flat 
top  (so  as  not  to  catch  the  edge  of  the  needle  as  shown  in  Fig.  96)  and  if  made 
to  taper  towards  the  edge  may  be  used  for  the  soundness  test  also.  They  should 


FIG.  95. — Gilmore  Needles. 


646  CEMENT 

be  kept  in  a  moist  closet  or  under  a  damp  cloth  to  prevent  drying  out.     A  large 
covered  tin  box  containing  a  wet  sponge  makes  a  good  moist  closet. 


FIG.  96. — Pat  for  Determining  Setting  Time  and  Soundness. 

Soundness  or  Constancy  of  Volume.  For  this  test,  which  is  intended  to 
show  the  endurance  of  concrete  made  from  the  cement,  pats  about  3  ins.  in 
diameter  and  |  in.  thick  at  the  center,  and  tapering  to  a  thin  edge  should  be 
made  upon  a  clean  glass  plate  4  ins.  square.  The  paste  from  which  the  pats 
are  made  should  be  of  normal  consistency  and  they  should  be  allowed  to  harden 
twenty-four  hours  in  a  moist  closet.  At  the  end  of  this  time  they  should  be 
exposed  in  an  atmosphere  of  steam,  1  in.  above  boiling  water,  in  a  loosely  covered 
vessel  for  three  hours.  At  the  end  of  this  time  the  pats  should  show  no  signs 
of  cracking,  distortion,  or  disintegration.  Distortion  has  not  taken  place  if 


FIG.  97. — Appearance  of  Pats  Made  from  Sound  and  Unsound  Cement  after  Steaming. 

the  pat  sticks  to  the  glass  plate.  Should  it  leave  the  plate,  however,  distortion 
may  be  detected  by  applying  the  edge  of  a  ruler  to  the  under  side  of  the  pat. 

Fig.  97  shows  six  pats  which  have  been  steamed.  Pats  E  and  F  have  almost 
entirely  disintegrated,  while  B  is  somewhat  better  and  A  and  D  almost  sound. 
Pat  C  has  stood  the  test  successfully. 

The  cold-water  test  is  also  used  (principally  as  a  check  upon  the  steam 
test)  and  consists  in  immersing  a  pat  (similar  to  that  used  for  steam)  in  cold  water 
for  twenty-eight  days,  at  the  end  of  which  time  it  should  show  no  signs  of 
cracking,  distortion,  or  disintegration.  . 


CEMENT 


647 


The  cracks  due  to  disintegration  should  not  be  confused  with  those  due  to 
drying  of  the  pat.  The  former  are  wedge  shaped  and  radiate  from  the  center 
of  the  pat,  while  the  latter  are  usually  running  across  the  middle  of  the  pat  or 
around  its  edges.  Shrinkage  cracks  due  to  drying  are  usually  developed  in  a 
day  or  so,  and  are  due  to  too  thin  (wet)  a  paste.  Disintegration  cracks  rarely 
appear  until  after  two  or  three  days,  and  are  due  to  expansives  in  the  cement. 
The  cracking  of  the  glass  to  which  the  pat  is  attached  during  boiling  means 
nothing  to  condemn  the  cement,  and  is  due 
merely  to  unequal  expansion  of  the  pat 
and  glass  by  the  heat  and  a  firm  adhesion 
of  the  one  to  the  other. 

Where  only  a  few  tests  have  to  be 
made,  a  convenient  form  of  boiler  consists 
of  a  tin  bucket  provided  with  a  tin  top. 
A  few  holes  to  permit  exit  of  the  steam 
are  made  in  the  top  and  a  shelf  of  wire 
net  or  perforated  tin  is  placed  in  the 
bucket.  The  pats  are  set  on  this  and 
should  be  at  least  2  ins.  above  the  water. 
Tensile  Strength.  The  tensile  strength 
of  cement  is  tested  both  neat  and  with 
sand.  In  both  tests  the  paste  or  mortar 
is  moulded  into  a  test-piece  called  a  bri- 
quette, shown  in  Fig.  98,  the  least  cross- 
section  of  which  is  1  sq.in.  in  area.  The 
moulds  (Fig.  99)  should  be  made  of  brass 
or  bronze.  They  are  made  to  permit  of 
the  making  of  but  one  briquette  at  a  time 
(single  moulds)  or  to  permit  of  moulding  a 
number  of  briquettes  simultaneously  (gang 
moulds) . 

The  mortar  is  mixed  just  as  described  under  the  heading  "Normal  Con- 
sistency/' about  125  grams  of  cement  being  used  for  each  neat  briquette,  or  500 
grams  for  a  gang  of  four  briquettes. 

Immediately  after  mixing  the  mortar  or  paste,  the  moulds  should  be  filled, 
the  material  pressed  in  firmly  with  the  fingers  and  smoothed  off  with  a  trowel 

without  ramming;  the  material 
should  be  heaped  up  on  the 
upper  surface  of  the  mould,  and, 
in  smoothing  off,  the  trowel 
should  be  drawn  over  the  mould 
in  such  a  manner  as  to  exert  a 
moderate  pressure  on  the  excess 
materials.  The  mould  should  be  turned  over  and  the  operation  repeated. 

The  moulds  containing  the  briquettes  should  then  be  kept  in  a  moist  closet, 
or  under  a  damp  cloth  until  the  briquettes  have  hardened  sufficiently  to  remove 
from  the  moulds,  usually  in  about  four  to  eight  hours.  On  removal  from  the 
mould,  the  briquettes  should  be  kept  in  the  moist  closet  until  they  are  twenty-four 
hours  old,  when,  with  the  exception  of  the  one-day  briquettes,  which  are  broken 
immediately,  they  should  be  placed  in  water,  kept  at  as  near  21°  C.  as  possible. 


DETAILS  FOR  BRIQUETTE. 
FIG.  98. 


DETAILS  FOR  GANG  MOULD. 
FIG.  99. 


648 


CEMENT 


The  briquettes  are  then  removed  from  the  water  at  intervals  and  immediately 
broken  by  means  of  some  form  of  testing  machine.  Fig.  100  shows  the  Fair- 
banks cement-testing  machine.  In  this  machine  the  briquette  is  held  in  the 
clips,  N  and  N,  and  a  stress  is  applied  to  it  through  the  levers,  C  and  R,  by  the 
weight  of  fine  shot  falling  into  the  bucket,  F.  After  the  specimen  breaks  the 
stress  required  to  rupture  it  is  found  by  weighing  the  shot;  the  beam,  R,  being 
graduated  for  this  purpose.  In  placing  the  briquette  in  the  clips  great  care 

must  be  exercised  to  center  it  properly,  as 
cross  strains  tend  to  lower  the  breaking 
strength.  The  briquettes  must  be  broken 
as  soon  as  they  are  removed  from  the 
water  and  the  flow  of  shot  into  the  bucket 
should  be  so  regulated  as  to  represent  a 
load  of  about  600  Ibs.  per  minute. 

Fig.  101  shows  the  Riehle"  automatic 
cement-testing  machine.  This  is  a  new 
type  of  machine  which  is  coming  into  general 
use  for  cement  testing,  as  it  does  away 
with  some  of  the  errors  in  the  older  form. 
In  this  type,  the  initial  load  is  avoided  by 
balancing  a  bucket  of  shot  against  a  weight 
and  the  load  is  applied  to  the  test  specimen 
by  allowing  the  shot  to  run  out  of  the 
bucket.  The  load  acting  through  the  levers 
breaks  the  briquette  when  the  shot  is  cut 
off  by  means  of  an  automatic  valve.  The 
shot  flowing  out  of  the  bucket  are  caught 
in  a  large  cup  resting  on  a  spring  scale 
which  registers  the  load.  This  can  be  read 
as  soon  as  the  briquette  breaks.  The  beam 
should  be  kept  horizontal  by  means  of  the 
lever  and  worm  gear  as  shown  by  the  pointer  on  the  beam. 

Briquettes  are  usually  broken  in  series  from  two  to  five  each.  The  periods  of 
breaking  are  after  one  day,  seven  days,  twenty-eight  days,  three  months,  six 
months,  one  year,  two  years,  three  years,  five  years,  ten  years,  etc.  The  tests 
of  one  year  and  upwards  are  usually  called  long-time  tests.  In  some  laboratories 
only  one-day,  seven-day  and  twenty-eight-day  tests  are  made.  The  one-day 
briquettes  are  broken  exactly  twenty-four  hours  after  they  are  made,  the  seven- 
day  briquettes  seven  days  after,  etc. 

Sand  briquettes  are  made  of  a  mixture  of  one  part  cement  and  three  of 
standard  sand,  and  these  are  first  mixed  dry  and  then  the  water  is  added  and 
the  moulding  done  as  for  neat  briquettes.  The  standard  sand  at  the  present 
time  is  a  natural  sand  from  Ottawa,  111.,  which  is  obtained  from  the  Ottawa 
Silica  Sand  Co.,  Sandusky,  O.  It  should  be  screened  to  pass  a  sieve  made  of 
wires  0.0165  in.  in  diameter  and  of  20  meshes  to  the  linear  inch  and  to  be 
retained  by  a  30-mesh  sieve  (of  0.0112  in.  diameter  wire).  Some  testers,  how- 
ever, use  crushed  quartz,  such  as  is  used  in  the  manufacture  of  sand-paper, 
sized  to  pass  a  No.  20  sieve  and  be  retained  on  a  No.  30.  The  Ottawa  sand, 
however,  gives  the  higher  results.  No  sand  briquettes  are  usually  broken  for 
twenty-four  hour  periods. 


FIG.  100. 
Fairbanks  Cement-testing  Machine. 


CEMENT 


649 


The  standard  specifications  require  a  minimum  strength  of  200  Ibs.  with 
sand  after  seven  days,  and  300  with  sand  after  twenty-eight  days,  and  also  that 
the  average  figures  in  each  case  must  be  higher  for  the  latter  than  for  the  former 
period. 

The  standard  specifications  now  do  not  require  a  neat  test  to  be  made,  but 
it  is  usually  done  for  information. 

Notes.    After  use,  the  moulds  should  be  scraped  free  of  hardened  cement 
with  a  piece  of  soft  metal   (such  as 
copper  or  zinc),  brushed   off   with   a 
stiff  blacking  brush,  and  wiped  with  a 
cloth  and  a  little  machine  oil. 

Neat  briquettes  should  be  marked 
with  a  stencil  so  as  to  identify  them, 
and  the  sand  briquettes  placed  in  the 
water  below  the  neat  ones  in  such  a 
manner  as  to  identify  the  former. 
Usually  the  sand  briquettes  are  placed 
edgewise  in  the  water,  and  the  cor- 
responding neats  are  placed  edgewise 
on  top  of  the  sand. 

Small  troughs  or  tanks  consisting 
merely  of  galvanized  iron  pans,  3  ins. 
deep,  may  be  purchased  and  will  an- 
swer where  only  a  few  tests  are  to 
be  made.  Otherwise  shallow  wooden 
troughs  lined  with  zinc  will  be  found 

convenient.    They  may  be  placed  one  .„.,,,  ,.  r^'  1U1/  ,    ,.      ,T    ,. 

i         fh      th        '  Riehle  Automatic  Cement-testing  Machine. 

Apparatus   Needed   for   Cement  Testing. 

be  needed  for  cement  testing  : 


101. 


The   following  apparatus  will 


1.  Apparatus  for  specific  gravity,  Le  Chatelier's. 

2.  Scale  for  fineness. 

3.  Sieve  —  100  mesh,  standard. 

4.  Sieve  —  200  mesh,  standard. 

5.  Vicat  apparatus  (or  Gilmore  needles). 

6.  Trowel—  8  ins. 

7.  Rubber  gloves. 

8.  Measuring  glass  —  500  cc.  capacity. 

9.  Slab  of  glass  (or  brass),  24X24  ins. 

10.  Scale,  capacity,  1000  grams. 

11.  Weights  for  above  scale. 

12.  Glass  plates—  4X4  ins. 

13.  Moulds. 

14.  Testing  machine. 

15.  Standard  sand. 

16.  Galvanized  iron  pan,  24X24X13  ins. 


650  CEMENT 


STANDARD   METHOD   FOR   CHEMICAL  ANALYSIS   OF 
PORTLAND   CEMENT1 

Solution 

One-half  gram  of  the  finely  powdered  substance  is  to  be  weighed  out  and, 
if  a  limestone  or  unburned  mixture,  strongly  ignited  in  a  covered  platinum  cru- 
cible over  a  strong  blast  for  fifteen  minutes,  or  longer  if  the  blast  is  not  powerful 
enough  to  effect  complete  conversion  to  a  cement  in  this  time.  It  is  then  trans- 
ferred to  an  evaporating  dish,  preferably  of  platinum  for  the  sake  of  celerity  in 
evaporation,  moistened  with  enough  water  to  prevent  lumping,  and  5  to  10  cc. 
of  strong  HC1  added  and  digested  with  the  aid  of  gentle  heat  and  agitation  until 
solution  is  complete.  Solution  may  be  aided  by  light  pressure  with  the  flattened 
end  of  a  glass  rod.2  The  solution  is  then  evaporated  to  dryness,  as  far  as  this 
may  be  possible  on  the  bath. 

Silica  (SiO2) 

The  residue  without  further  heating  is  treated  at  first  with  5  to  10  cc.  of 
strong  HC1,  which  is  then  diluted  to  half  strength  or  less,  or  upon  the  residue 
may  be  poured  at  once  a  larger  volume  of  acid  of  half  strength.  The  dish  is 
then  covered  and  digestion  allowed  to  go  on  for  ten  minutes  on  the  bath,  after 
which  the  solution  is  filtered  and  the  separated  silica  washed  thoroughly  with 
water.  The  filtrate  is  again  evaporated  to  dryness,  the  residue,  without  fur- 
ther heating,  taken  up  with  acid  and  water  and  the  small  amount  of  silica  it 
contains  separated  on  another  filter  paper.  The  papers  containing  the  residue 
are  transferred  wet  to  a  weighed  platinum  crucible,  dried,  ignited,  first  over 
a  Bunsen  burner  until  the  carbon  of  the  filter  is  completely  consumed,  and  finally 
over  the  blast  for  fifteen  minutes  and  checked  by  a  further  blasting  for  ten 
minutes  or  to  constant  weight.  The  silica,  if  great  accuracy  is  desired,  is  treated 
in  the  crucible  with  about  10  cc.  of  HF1  and  4  drops  of  H2S04,  and  evaporated 
over  a  low  flame  to  complete  dryness.  The  small  residue  is  finally  blasted,  for 
a  minute  or  two  cooled  and  weighed.  The  difference  between  this  weight  and 
the  weight  previously  obtained  gives  the  amount  of  silica.8 

Alumina  and  Iron  (A^Os  and  Fe2Os) 

The  filtrate,  about  250  cc.,  from  the  second  evaporation  for  Si02,  is  made 
alkaline  with  NH4OH  after  adding  HC1,  if  need  be,  to  insure  a  total  of  10  to  15 
cc.  of  strong  acid,  and  boiled  to  expel  excess  of  NH3,  or  until  there  is  but  a  faint 
odor  of  it,  and  the  precipitated  iron  and  aluminum  hydrates,  after  settling,  are 
washed  once  by  decantation  and  slightly  on  the  filter.  Setting  aside  the  filtrate, 
the  precipitate  is  dissolved  in  hot  dilute  HC1,  the  solution  passing  into  the 

1  Method  Suggested  for  the  Analysis  of  Limestones,  Raw  Mixtures,  and  Portland 
Cements  by  the  Committee  on  Uniformity  in  Technical  Analysis  with  the  Advice 
of  W.  F.  Hillebrand. 

2  If  anything  remains  undecomposed  it  should  be  separated,  fused  with  a  little 
NajCOj,  dissolved  and  added  to  the  original  solution.     Of  course  a  small  amount  of 
separated  non-gelatinous  silica  is  not  to  be  mistaken  for  undecomposed  matter. 

8  For  ordinary  control  in  the  plant  laboratory  this  correction  may,  perhaps,  be 
neglected;  the  double  evaporation,  never. 


CEMENT  651 

beaker  in  which  the  precipitation  was  made.  The  aluminum  and  iron  are  then 
reprecipitated  by  NH4OH,  boiled  and  the  second  precipitate  collected  and  washed 
on  the  same  filter  used  in  the  first  instance.  The  filter  paper,  with  the  pre- 
cipitate, is  then  placed  in  a  weighed  platinum  crucible,  the  paper  burned  off 
and  the  precipitate  ignited  and  finally  blasted  five  minutes,  with  care  to  pre- 
vent reduction,  cooled  and  weighed  as  Al203-hFe203.1 

Iron  (Fe2O3) 

The  combined  iron  and  aluminum  oxides  are  fused  in  a  platinum  crucible 
at  a  very  low  temperature  with  about  3  to  4  grams  of  KHS04,  or,  better,  NaHS04, 
the  melt  taken  up  with  so  much  dilute  H2S04  that  there  shall  be  no  less  than 
5  grams  absolute  acid  and  enough  water  to  effect  solution  on  heating.  The 
solution  is  then  evaporated  and  eventually  heated  till  acid  fumes  come  off 
copiously.  After  cooling  and  redissolving  in  water,  the  small  amount  of  silica 
is  filtered  out,  weighed  and  corrected  by  HF1  and  H2S04.2  The  filtrate  is  reduced 
by  zinc,  or  preferably  by  hydrogen  sulphide,  boiling  out  the  excess  of  the 
latter  afterwards  while  passing  C02  through  the  flask,  and  titrated  with  per- 
manganate.3 The  strength  of  the  permanganate  solution  should  not  be  greater 
than  .0040  gram  Fe203  per  cc. 

Lime  (CaO) 

To  the  combined  filtrate  from  the  Al203-f  Fe203  precipitate  a  few  drops  of 
NH4OH  are  added,  and  the  solution  brought  to  boiling.  To  the  boiling  solution 
20  cc.  of  a  saturated  solution  of  ammonium  oxalate  are  added,  and  the  boiling 
continued  until  the  precipitated  CaC204  assumes  a  well-defined  granular  form. 
It  is  then  allowed  to  stand  for  twenty  minutes,  or  until  the  precipitate  has 
settled,  and  then  filtered  and  washed.  The  precipitate  and  filter  are  placed 
wet  in  a  platinum  crucible,  and  the  paper  burned  off  over  a  small  flame  of  a 
Bunsen  burner.  It  is  then  ignited,  redissolved  in  HC1,  and  the  solution  made 
up  to  100  cc.  with  water.  Ammonia  is  added  in  slight  excess,  and  the  liquid 
is  boiled.  If  a  small  amount  of  A1203  separates,  this  is  filtered  out,  weighed, 
and  the  amount  added  to  that  found  in  the  first  determination,  when  greater 
accuracy  is  desired.  The  lime  is  then  reprecipitated  by  ammonium  oxalate, 
allowed  to  stand  until  settled,  filtered,  and  washed,4  weighed  as  oxide  by  ignition 
and  blasting  in  a  covered  crucible  to  constant  weight,  or  determined  with  dilute 
standard  permanganate.5  •*• 

Magnesia  (MgO) 

The  combined  filtrates  from  the  calcium  precipitates  are  acidified  with  HC1 
and  concentrated  on  the  steam  bath  to  about  150  cc.,  10  cc.  of  saturated  solution 

1  This  precipitate  contains  TiO2,  P2O5,  Mn3O4. 

2  This  correction  of  Al2O3Fe2O3  for  silica  should  not  be  made  when  the  HF1  cor- 
rection of  the  main  silica  has  been  omitted,  unless  that  silica  was  obtained  by  only 
one  evaporation  and  filtration.     After  two  evaporations  and  nitrations  1  to  2  milli- 
grams of  SiO2  are  still  to  be  found  with  the  Al2O3Fe2O3. 

3  In  this  way  only  is  the  influence  of  titanium  to  be  avoided  and  a  correct  result 
obtained  for  iron. 

The  volume  of  wash-water  should  not  be  too  large;  vide  W.  F.  Hildebrand. 
fThe  accuracy  of  this    method  admits    of  criticism,   but  its  convenience  and 
rapidity  demand  its  insertion. 


652  CEMENT 

of  Na(NH4)HP04  are  added,  and  the  solution  boiled  for  several  minutes.  It 
is  then  removed  from  the  flame  and  cooled  by  placing  the  beaker  in  ice  water. 
After  cooling,  NH4OH  is  added  drop  by  drop  with  constant  stirring  until  the 
crystalline  ammonium-magnesium  ortho-phosphate  begins  to  form,  and  then 
in  moderate  excess,  the  stirring  being  continued  for  several  minutes.  It  is  then 
set  aside  for  several  hours  in  a  cool  atmosphere  and  filtered.  The  precipitate 
is  redissolved  in  hot  dilute  HC1,  the  solution  made  up  to  100  cc.,  1  cc.  of  a  sat- 
urated solution  of  Na(NH4)HP04  added,  and  ammonia  drop  by  drop,  with 
constant  stirring  until  the  precipitate  is  again  formed  as  described  and  the 
ammonia  is  in  moderate  excess.  It  is  then  allowed  to  stand  for  about  two  hours, 
when  it  is  filtered  on  a  paper  or  a  Gooch  crucible,  ignited,  cooled  and  weighed 
as  M^PzOr.  Portland  cement  must  not  contain  more  than  4%  magnesia. 

Alkalies  (K2O  and  Na2O) 

For  the  determination  of  the  alkalies,  the  well-known  method  of  Prof.  J. 
Lawrence  Smith  is  to  be  followed,  either  with  or  without  the  addition  of  CaCOs 
with  NH4C1. 

Anhydrous  Sulphuric  Acid  (SOs) 

One  gram  of  the  substance  is  dissolved  in  15  cc.  of  HC1,  filtered  and  residue 
washed  thoroughly.1 

The  solution  is  made  up  to  250  cc.  in  a  beaker  and  boiled.  To  the  boiling 
solution  10  cc.  of  a  saturated  solution  of  BaClz  are  added  slowly  drop  by  drop 
from  a  pipette  and  the  boiling  continued  until  the  precipitate  is  well  formed, 
or  digestion  on  the  steam  bath  may  be  substituted  for  the  boiling.  It  is  then 
set  aside  over  night,  or  for  a  few  hours,  filtered,  ignited  and  weighed  as  BaS04. 
Both  specifications  require  cement  to  contain  not  more  than  1.75%  SOs. 

Total  Sulphur 

One  gram  of  the  material  is  weighed  out  in  a  large  platinum  crucible  and  fused 
with  Na2COs  and  a  little  KNOs,  being  careful  to  avoid  contamination  from  sul- 
phur in  the  gases  from  source  of  heat.  This  may  be  done  by  fitting  the  crucible 
in  a  hole  in  an  asbestos  board.  The  melt  is  treated  in  the  crucible  with  boiling 
water  and  the  liquid  poured  into  a  tall,  narrow  beaker  and  more  hot  water 
added  until  the  mass  is  disintegrated.  The  solution  is  then  filtered.  The  fil- 
trate contained  in  a  No.  4  beaker  is  to  be  acidulated  with  HC1  and  made  up  to 
250  cc.  with  distilled  water,  boiled,  the  sulphur  precipitated  as  BaS04  and  allowed 
to  stand  over  night  or  for  a  few  hours. 

Loss  on  Ignition 

Half  a  gram  of  cement  is  to  be  weighed  out  in  a  platinum  crucible,  placed 
in  a  hole  in  an  asbestos  board  so  that  about  three-fifths  of  the  crucible  projects 
below,  and  blasted  fifteen  minutes,  preferably  with  an  inclined  flame.  The 
loss  by  weight,  which  is  checked  by  a  second  blasting  of  five  minutes,  is  the  loss 
on  ignition.  This  must  not  be  more  than  4%. 

1  Evaporation  to  dryness  is  unnecessary,  unless  gelatinous  silica  should  have  sepa- 
rated, and  should  never  be  performed  on  a  bath  heated  by  gas;  vide  W.  F.  Hildebrand. 


CEMENT  653 

May,  1903:  Recent  investigations  have  shown  that  large  errors  in  results 
are  often  due  to  the  use  of  impure  distilled  water  and  reagents.  The  analyst 
should,  therefore,  test  his  distilled  water  by  evaporation  and  his  reagents  by 
appropriate  tests  before  proceeding  with  his  work. 

Insoluble  Residue 

In  addition  to  the  above  the  U.  S.  Government  specifications  require  the 
cement  to  show  not  more  than  1%  insoluble  residue  as  determined  below. 

A  1-gram  sample  is  digested  on  the  steam  bath  in  HC1  of  approximately 
1.035  sp.gr.  until  the  cement  is  dissolved.  The  residue  is  filtered,  washed  with 
hot  water,  and  the  filter  paper  and  contents  digested  on  the  steam  bath  in  a 
5%  solution  of  sodium  carbonate.  The  residue  is  then  filtered,  washed  with 
hot  water,  then  with  hot  HC1  (1.035  sp.gr.)  and  finally  with  hot  water,  then 
ignited  at  a  red  heat  and  weighed.  The  quantity  so  obtained  is  the  insoluble, 
residue. 

RAPID   METHOD  FOR   CHEMICAL  ANALYSIS   OF 
PORTLAND   CEMENT1 

Before  submitting  the  cement  to  a  chemical  analysis  it  should  be  passed 
through  a  No.  100  test  sieve  to  free  it  from  pieces  of  clinker  too  large  to  be 
quickly  attacked  by  the  acid. 

Weigh  0.5  gram  of  cement  into  a  wide  platinum  or  porcelain  dish.  The 
former  is  the  more  expensive  of  the  two,  but  it  is  a  better  conductor  of  heat 
and  there  is  no  danger  of  contaminating  the  solution  with  silica,  etc.,  from  the 
dish,  if  the  evaporation  is  conducted  in  platinum.  The  silica  can  also  be 
entirely  removed  from  a  platinum  dish.  Now  stir  up  the  sample  of  cement  in 
the  dish  with  10  cc.  of  cold  water  until  all  lumps  are  broken  up,  and  add  imme- 
diately 10  cc.  of  cold  dilute  hydrochloric  acid  (1  :  1).  Place  the  dish  on  a  water 
bath  and  evaporate  to  dryness,  stirring  occasionally.  The  water  bath  will 
evaporate  as  fast  as  anything  else  and  there  is  no  danger  of  the  silica's  spatter- 
ing, which  it  is  apt  to  do,  unless  the  operation  is  very  carefully  watched,  when 
a  hot  plate  is  used.  As  soon  as  the  contents  of  the  dish  are  dry,  cool,  add  10 
cc.  of  dilute  hydrochloric  acid  and  30  cc.  of  water,  digest  five  or  ten  minutes  on 
the  hot  plate,  filter  and  wash  ten  times  with  hot  water.  Evaporate  the  filtrate 
to  dryness.  Cool,  add  10  cc.  of  dilute  hydrochloric  acid  and  50  cc.  of  water 
to  the  contents  of  the  dish,  cover  with  a  watch-glass  and  digest  on  the  hot  plate 
for  five  or  ten  minutes.  Filter  off  the  slight  residue  of  silica  on  a  9-cm.  filter, 
wash  well  (seven  to  ten  times)  with  hot  water  and  put  in  a  weighed  platinum  crucible 
together  with  the  silica  obtained  from  the  first  filtration.  Ignite  over  the  Bunsen 
burner  until  all  the  filter  paper  is  consumed  and  then  ignite  strongly  over  a 
blast  lamp  for  ten  minutes.  Cool  in  a  desiccator  and  weigh  as  Si02;  multiply 
the  weight  by  200  for  per  cent  of  silica,  Si02. 

Heat  the  filtrate  to  boiling  and  add  a  faint  but  distinct  excess  of  ammonia. 
This  can  be  most  conveniently  done  by  means  of  a  bottle,  fitted  with  a  siphon 
tube,  the  end  of  which  terminates  in  a  jet,  connected  to  it  by  a  short  piece  of 
rubber  tubing,  which  is  closed  by  a  pinch  cock.  The  bottle  stands  on  a  shelf 

1  Method  used  in  the  laboratories  of  most  cement  companies  and  for  routine 
work. 


654  CEMENT 

over  the  reagent  table,  and  the  siphon  extends  to  within  six  inches  of  the  sur- 
face of  the  table.  The  beaker  is  placed  under  the  jet,  and  the  ammonia  can 
be  very  carefully  and  conveniently  added  by  pressing  the  pinchcock.  After 
adding  the  ammonia  replace  the  beaker  on  the  hot  plate  and  boil  for  five  minutes. 
Remove  from  the  hot  plate  and  allow  the  precipitate  to  settle.  Filter  onto 
an  11-cm.  filter  paper  and  wash  once  with  hot  water  to  collect  the  precipitate 
in  the  cone  of  the  filter.  Invert  the  funnel  over  the  beaker  in  which  the  pre- 
cipitation was  made  and  wash  practically  all  of  the  precipitate  into  this,  allowing 
the  filter  to  remain  in  the  funnel.  Dissolve  the  precipitate  in  20  cc.  of  10% 
nitric  acid  (1  :  10)  and  dilute  the  solution  to  100  cc.  Heat  to  boiling  and  repre- 
cipitate  with  ammonia  as  before.  Boil  for  five  minutes,  allow  the  precipitate 
to  settle  and  filter  through  the  same  filter  paper  as  used  for  the  first  precipitation. 
Wash  once  with  hot  water.  Ignite  carefully  in  a  weighed  crucible  over  a  Bunsen 
burner  and  finally  blast  for  five  minutes.  Cool  and  weigh  as  combined  oxides 
of  iron  and  alumina,  Fe203+Al203.  This  precipitate  also  contains  manganese 
dioxide,  phosphoric  and  titanic  acids,  all  of  which  are  present  in  small  quantities 
in  the  cement.  Determine  the  iron  oxide  as  directed  further  on,  and  deduct 
from  the  combined  weights  for  the  alumina,  A1203  (phosphoric  acid,  titanic 
acid,  etc.). 

Make  the  filtrate  from  the  iron  and  alumina  alkaline  with  ammonia;  boil 
and  add  20  cc.  of  boiling  saturated  ammonium  oxalate  solution  (or  better,  3  grams 
of  solid  ammonium  oxalate  dissolved  in  25-50  cc.  of  boiling  water  just  prior  to 
use).  Stir  well,  allow  fifteen  minutes  to  settle,  filter  on  an  11-cm.  filter,  and 
wash  ten  times  with  hot  water,  using  as  little  as  possible  (about  100-125  cc.) 
to  do  the  work  well.  Proceed  as  in  A  or  B. 

A.  Gravimetric.    Place  the    precipitate   in   a  weighed    platinum    crucible, 
ignite,  and  weigh,  after  ignition  over  a  blast-lamp  to  constant  weight,  as  cal- 
cium oxide,  CaO.    Report  as  such. 

B.  Volumetric.    Transfer  the  paper  and  precipitate  to  the  beaker  in  which 
the  latter  was  formed,..and  opening,  spread  it  out  against  the  upper  side  of  the 
beaker.    Wash  the  precipitate  off  the  paper  with  a  jet  of  hot  water,  fold  the 
paper  over,  add  50  cc.  of  dilute  (10%)  sulphuric  acid  (1  :  10)  to  the  contents 
of  the  beaker,  dilute  to  150  cc.  and  heat  until  the  liquid  is  between  60  and  90° 
C.    Titrate  with  permanganate  solution  until  the  pink  color  is  produced.    All 
this  time  the  paper  should  be  sticking  to  the  walls  of  the  beaker.     Now  drop 
this  into  the  solution  and  stir.    The  pink  color  of  the  latter  will  be  discharged. 
Finish  the  titration  very  carefully  by  adding  permanganate,  a  drop  at  a  time, 
and  calculate  the  lime. 

If  the  filtrate  from  the  lime  measures  over  250  cc.,  acidify  and  evaporate  until 
this  bulk  is  reached.  This  can  be  rapidly  done  by  using  a  large  (8  in.)  porcelain 
dish  in  the  following  manner:  Place  a  piece  of  wire  gauze  on  a  tripod  and  in  the 
center  of  this  a  round  piece  of  thin  asbestos  paper  about  the  size  of  a  silver 
dollar.  Now  place  the  dish  on  this  and  a  Bunsen  burner  turned  fairly  low 
under  the  asbestos  dish.  The  contents  of  the  dish  can  then  be  made  to  evapo- 
rate rapidly,  without  boiling,  by  regulating  the  flame.  When  the  solution 
measures  250  cc.,  transfer  to  a  beaker.  If  necessary,  cool  and,  when  perfectly 
cold,  add  15  cc.  of  a  10%  solution  of  sodium  phosphate  and  25  cc.  of  strong 
ammonia.  Stir  thoroughly  and  set  aside  in  a  cool  place  for  at  least  six  hours. 
Filter,  wash  with  a  mixture  of  water  800  cc.,  ammonia  (0.96  sp.gr.)  200  cc.,  and 
ammonium  nitrate  100  grams;  place  in  a  weighed  platinum  or  porcelain  crucible 


CEMENT  655 

and  ignite  over  a  low  flame  until  all  carbon  is  burned  off.  (Do  not  use  the 
blast  lamp.)  Cool  in  a  desiccator  and  weigh  as  magnesium  pyrophosphate, 
which  weight  multiplied  by  72.38  gives  the  percentage  of  magnesia,  MgO. 

Weigh  1  gram  of  finely  ground  cement  into  a  small  beaker  and  add  15  cc. 
of  dilute  hydrochloric  acid,  heat  from  ten  to  fifteen  minutes  and  add  a  little 
water.  Heat  to  boiling  and  filter  *•  through  a  small  filter,  washing  the  residue 
well  with  water  and  catching  the  filtrate  and  washings  in  a  small  beaker.  Add 
to  the  solution  5  cc.  of  dilute  hydrochloric  acid  and  bring  to  a  boil.  Add  care- 
fully, drop  by  drop,  stannous  chloride  solution  (25  grams  in  100  cc.  of  dilute 
1  :  3  hydrochloric  acid)  until  the  last  drop  makes  the  solution  colorless.  Add 
3  drops  in  excess.  Remove  from  the  burner  and  cool  the  liquid  by  setting  in 
a  vessel  of  cold  water.  When  nearly  cold,  add  15  cc.  of  saturated  mercuric 
chloride  solution  and  stir  the  liquid  with  a  glass  rod.  Allow  the  mixture  to 
stand  for  a  few  minutes,  during  which  time  a  slight  white  precipitate  should 
form.  Run  in  standard  bichromate  solution  carefully  from  a  burette  until  a 
drop  of  iron  solution  tested  with  a  drop  of  1%  solution  of  potassium  ferri- 
cyanide  no  longer  shows  a  blue,  but  instead  a  yellow  color.  Multiply  the 
number  of  cc.  of  bichromate  used  by  the  ferric  oxide  equivalent  per  cc.  of  the 
bichromate  and  divide  the  product  by  the  weight  of  the  sample.  The  result 
multiplied  by  100  gives  the  per  cent  of  the  ferric  oxide  in  the  cement.  The 
most  convenient  strength  for  the  standard  bichromate  solution  is  3.074  grams 
of  the  salt  to  the  liter.  One  cc.  of  this  solution  is  equivalent  to  0.005  gram 
ferric  oxide.  It  should  be  standardized  against  iron  wire  or  ferrous  ammonium 
sulphate. 

Weigh  1  gram  of  the  sample  into  a  small  dry  beaker  and  stir  it  up  \uth 
10  cc.  of  cold  water  until  all  lumps  are  broken  up  and  the  lighter  particles  are 
in  suspension.  Add  7.5  cc.  of  dilute  (1  :  1)  hydrochloric  acid  and  heat  until 
solution  is  complete.  Filter  through  a  small  paper  and  wash  the  residue  thor- 
oughly. Dilute  the  filtrate  to  250  cc.,  heat  to  boiling,  and  add  10  cc.  of  boiling 
10%  barium  chloride  solution.  Stir  well  and  allow  to  stand  overnight.  Filter, 
ignite,  and  weigh  as  BaS04,  which,  multiplied  by  34.29,  gives  the  percentage  of 
S03. 

Place  one-half  gram  of  the  cement  in  a  clean  platinum  crucible  which  has 
been  previously  ignited  to  redness  and  cooled  in  a  desiccator.  Cover  with  the 
lid  and  weigh.  Ignite  for  fifteen  minutes  over  a  good  blast  lamp.  Rinse  off 
the  crucible  lid  with  hot  water  to  remove  volatile  salts  condensed  on  the  latter. 
Ignite  the  lid  to  redness  and  cool  the  crucible  and  lid  in  a  desiccator.  Weigh 
and  the  loss  in  weight  multiplied  by  200  is  ''loss  on  ignition." 

For  the  alkalies  in  cement  see  analysis  of  clay. 

1  May  be  omitted  if  the  cement  practically  all  dissolves.     Most  cements  do. 


656  CEMENT 


RAPID   METHOD    FOR   CHECKING     THE   PERCENTAGE   OF 
CALCIUM   CARBONATE   IN   CEMENT   MIXTURE 

The  following  rapid  method  is  generally  used  in  the  cement  industry  for 
checking  the  composition  of  the  ground  mixture  of  raw  materials  before  these 
are  fed  into  the  kiln. 

Standard  Alkali 

This  should  be  exactly  2/5  normal  and  may  be  prepared  in  any  convenient 
manner.  Usually  8  or  10  liters  are  made  up  at  one  time  and  kept  in  a  bottle 
provided  with  a  siphon  tube  and  with  a  layer  of  coal  oil  on  top  of  the  solution 
about  |  in.  thick  to  prevent  the  absorption  of  carbon  dioxide  by  the  caustic 
soda. 

Phenolphthalein  should  be  used  as  an  indicator.  A  1%  solution  of  this  is 
employed. 

One  cc.  of  2/5  N  alkali  is  equivalent  to  exactly  0.02  gram  of  CaC03  or  to 
2%  where  1-gram  sample  is  used. 

Standard  Acid 

Take  the  specific  gravity  of  a  bottle  of  hydrochloric  acid,  using  a  hydrometer 
for  the  purpose.  Refer  to  a  table  of  specific  gravities  of  hydrochloric  acid  and 
calculate  from  this  the  quantity  of  acid  necessary  to  contain  97.0  grams  of  HC1. 

Measure  this  quantity  of  the  acid  into  a  liter  flask  and  dilute  to  the  mark, 
pour  into  an  8-liter  bottle  and  add  7  liters  of  water,  measuring  with  the  flask. 
Mix  the  contents  of  the  bottle  well  by  shaking.  Ten  cc.  of  this  solution  should 
be  equivalent  to  from  8.1  to  8.5  cc.  of  the  2/5  N  alkali  when  checked  by  adding 
a  drop  of  phenolphthalein  solution  and  running  in  the  alkali  to  a  purple  red 
color.  If  its  value  does  not  lie  between  these  figures  add  acid  or  water  to  make 
it  of  this  strength. 

Standard  Sample 

A  standard  sample  of  raw  material  is  necessary  to  standardize  the  acid  and 
alkali  for  actual  use.  This  sample  should  be  ground  in  the  same  manner  as 
the  daily  run  of  samples  to  be  checked  by  the  acid  and  alkali.  It  should  all 
pass  a  100-mesh  sieve  and  be  freed  from  hygroscopic  moisture,  by  drying  for 
some  hours,  at  110°  C.  Three  or  four  pounds  of  this  sample  should  be  prepared 
and  kept  in  air-tight  jars  or  bottles.  A  small  sample  (1  or  2  oz.)  of  this  should 
be  placed  in  a  2-oz.  bottle  and  stoppered  with  a  rubber  cork  when  not  in  use. 
This  small  sample  can  then  be  redried  for  an  hour  at  100-110°  C.  and  used 
for  standardizing,  avoiding  the  frequent  opening  and  mixing  of  the  contents 
of  the  large  jars  or  bottles. 

After  drying,  the  standard  sample  should  be  carefully  analyzed.  It  should 
contain  approximately  the  quantity  of  carbonate  of  lime  which  it  is  desired  to 
have  in  the  mix,  and  the  amount  of  magnesia  should  also  be  normal.  When 
the  magnesia  varies  at  different  times,  fresh  standard  samples  should  be  pre- 
pared to  contain  these  varying  percentages  of  magnesia;  otherwise  the  lime 
will  be  reported  incorrectly. 


CEMENT 


657 


Standardizing  the  Acid 

Weigh  1  gram  of  the  standard  sample  into  a  600-cc.  Erlenmeyer  flask  and 
run  in  from  a  pipette  50  cc.  of  standard  acid.  Close  the  flask  with  a  rubber 
stopper,  having  inserted  through  it  a  long  glass  tube  30  ins.  long  and  about  f  in. 
internal  diameter.  Heat  the  flask  on  a  wire  gauze  over  a  burner  as  shown  in 
Fig.  102  until  steam  just  begins  to  escape  from  the  upper  end  of  the  tube.  The 
heating  should  be  so  regulated  that  the  opera- 
tion requires  very  nearly  two  minutes,  from  the 
time  the  heat  applied,  until  steam  issues  from 
the  tube.  Remove  the  flask  from  the  heat,  as 
soon  as  the  steam  escapes  from  the  tube,  and 
rinse  the  tube  into  the  flask,  in  the  following 
manner.  Rest  the  flask,  still  stoppered,  on  the 
table  and  grasp  the  tube  between  the  thumb 
and  forefinger  of  the  left  hand.  Direct  a  stream 
of  cold  water,  from  a  wash-bottle  in  the  right 
hand,  down  the  tube,  holding  the  latter  inclined 
at  an  angle  of  45°,  and  rolling  the  flask  from 
side  to  side  on  the  table,  in  sweeps  of  2  or  3  ft., 
by  twirling  the  tube  between  the  finger  and 
thumb.  Unstopper  the  flask  and  rinse  off  the 
.ides  and  bottom  of  the  stopper,  into  the  flask, 
and  wash  down  the  sides  of  the  latter.  Add  a 
drop  or  two  of  phenolphthalein  and  run  in  the 
standard  alkali,  from  a  burette,  until  the  color 
changes  to  purple  red.  This  color  is  often 
obscured  until  the  organic  matter  settles,  so  it 
is  necessary  to  hold  the  flask  to  the  light  and 
observe  the  change  by  glancing  across  the  sur- 
face.  A  little  practice  will  easily  enable  the 
operator  to  carry  on  the  titration  with  accuracy  and  precision. 

If  the  standard  sample  contains  L  per  cent  carbonate  of  lime  and  d  cc.  of 
alkali  are  required  to  produce  the  purple  red  color,  then,  to  find  the  carbonate 
of  lime  in  other  samples  it  is  only  necessary  to  subtract  the  number  of  cc.  of  alkali 
required  in  their  case  from  d,  multiply  the  difference  by  2,  and  add  to  L  for 
the  percentage  of  carbonate  of  lime  in  them;  or  the  number  of  cc.  is  greater 
than  d,  subtract  d  from  this  number,  multiply  by  2,  and  subtract  from  L  for 
the  carbonate  of  lime. 

In  order  to  avoid  all  calculations,  prepare  a  table  giving  the  various  per- 
centages of  carbonate  of  lime  corresponding  to  different  quantities  of  alkali. 

Determination 

Weigh  1  gram  of  the  sample,  which  has  been  ground  to  pass  a  100-mesh 
sieve,  into  the  flask,  add  50  cc.  of  the  standard  acid  and  proceed  as  directed 
under  standardizing  the  acid.  The  percentage  of  carbonate  of  lime  may  be 
found  from  the  number  of  cc.  of  alkali  used  either  from  the  preceding  table  or 
by  the  formula 

Per  cent  CaC05  =  L+(d-£)X2, 


Acid  and  Alkali. 


658  CEMENT 

where  L  and  d  have  the  same  values  as  in  the  paragraph  on  "Standardizing 
the  Acid"  and  S  represents  the  number  of  cc.  required  for  the  sample  whose 
composition  is  desired. 


ANALYSIS  OF  LIMESTONE,  CEMENT  ROCK,  LIME, 
ROSENDALE  CEMENT,   ETC. 

Dr.  Porter  W.  Shimer,  of  Easton,  Pa.,  modifies  the  standard  limestone  scheme 
by  fusing  the  sample  with  half  its  weight  of  sodium  carbonate.  By  this  means 
the  silicates  are  decomposed,  and  yet  the  quantity  of  sodium  carbonate  intro- 
duced into  the  solution  is  so  small  that  the  lime  and  magnesia  precipitates  are 
not  contaminated  with  sodium  salts.  Below  is  the  method. 

Silica,  etc.  Mix  thoroughly  0.5  gram  of  the  finely  ground  sample  with  £ 
gram  of  sodium  carbonate.  Place  over  a  low  flame  for  a  few  minutes,  then 
gradually  raise  the  flame.  Heat  over  the  full  flame  for  five  minutes  and  then 
over  the  blast  lamp  for  five  minutes.  There  will  be  no  complete  fusion,  only 
a  sintering.  Put  the  crucible  in  a  small  beaker  or  casserole  and  add  30  cc.  of 
water  and  10  cc.  of  hydrochloric  acid  (sp.gr.  1.10).  When  the  mass  is  dissolved 
out  of  the  crucible,  rinse  the  latter  off  into  the  beaker  and  remove  any  adhering 
matter  with  a  rubber-tipped  rod.  To  the  solution  in  the  beaker  or  casserole 
add  a  little  bromine  water  or  a  few  drops  of  nitric  acid,  evaporate  to  dryness 
and  proceed  as  directed,  in  the  analysis  of  Portland  cement. 

For  loss  on  ignition,  weigh  into  a  tared  platinum  crucible  0.5  gram  of  the 
sample.  Heat  at  first  over  a  low  flame,  then  gradually  raise  the  temperature 
and  finally  ignite  over  a  blast  lamp  until  it  ceases  to  lose  weight  on  reheating. 
Report  such  loss  in  weight  as  "loss  on  ignition." 

To  determine  iron  and  alumina  separately,  fuse  the  precipitated  ferric  oxide 
and  alumina  with  caustic  potash  in  a  silver  crucible  or  dish.  Treat  with  water, 
boil,  and  filter.  Ignite  the  residue  after  washing  and  weigh  as  ferric  oxide. 
This  weight  subtracted  from  the  combined  weight  of  the  ferric  oxide  and  alumina 
gives  the  weight  of  the  alumina,  A1203. 

To  determine  alkalies  in  limestone  use  the  method  described  for  clay,  employ- 
ing 8  grams  of  the  sample  and  1  gram  of  ammonium  chloride,  but  no  calcium 
carbonate. 


ANALYSIS  OF  ALLOYS1 

JOHN  C. 


Difficulty  of  Complete  Separation  of  Elements.  As  the  great  majority  of 
the  substances  with  which  the  chemist  is  called  upon  to  deal  are  complex  rather 
than  simple,  a  careful  study  of  the  separation  of  the  elements  is  of  the  greatest 
importance.  Only  by  the  closest  attention  to  details  can  success  be  attained 
in  the  analysis  of  complex  substances.  The  importance  of  testing  precipitates 
for  impurities  and  the  solution  for  unprecipitated  portions  of  an  element  can- 
not be  too  strongly  urged.  Only  in  this  manner  can  the  accuracy  of  an  analysis 
be  assured. 

Limit  of  Accuracy  in  Analysis.  If  a  complete  analysis  is  made  the  sum  of 
all  the  constituents  must  be  very  close  to  100%.  A  summation  which  is  within 
.5%  can  generally  be  obtained  if  the  analysis  is  conducted  with  care  and  reliable 
methods  are  used.  In  general  the  analysis  of  an  unknown  substance  should  be 
conducted  in  duplicate.  If  the  duplicate  results  do  not  agree  within  .2  or  at  most 
.3%,  a  third  analysis  should  be  made.  As  the  error  of  most  determinations  is 
at  least  .1%,  it  is  unnecessary  to  calculate  results  to  more  than  hundredths  of  per 
cent.  As  the  error  in  each  determination  of  the  analysis  of  a  given  substance  may 
be  either  plus  or  minus,  the  practice  of  dividing  the  difference  between  the  sum- 
mation and  100%  among  the  various  determinations  is  not  justifiable. 

It  is  in  some  cases  possible  to  analyze  a  substance  in  such  a  manner  that  the 
results  are  accurate  to  the  hundredth  of  a  per  cent.  Such  results  may  be  computed 
to  the  .001  of  a  per  cent.  This  practice  is  common  in  the  analysis  of  metals. 
Large  quantities  of  the  metal  are  taken,  so  that  considerable  quantities  of  the 
impurities  which  are  present  in  small  amounts  are  obtained  for  determination. 
The  results  may  then  be  accurate  to  the  hundredth  of  a  per  cent.  This  does  not 
imply  a  higher  degree  of  accuracy  in  the  determination  of  a  given  element  than 
.1  of  a  per  cent.  For  example,  if  iron  were  present  in  copper  to  the  extent  of 
.5%,  a  determination  of  the  iron  which  is  accurate  to  .01%  of  the  impure  copper 
would  represent  an  error  of  TO  of  the  amount  of  iron  present  in  the  copper.  In 
giving  the  results  of  such  analyses  the  percentage  of  the  main  constituent  is  obtained 
by  difference,  so  that  the  summation  is  exactly  100%. 

Analysis  of  Type  Metal 

Alloy  of  Copper,  Lead,  Antimony,  Tin,  with  Small  Amounts  of  Iron 

and  Arsenic 

Solution  of  the  Alloy.  To  1  gram  of  the  alloy,  which  has  been  cut  into  small 
shavings  with  a  clean  knife,  or  sampled  by  means  of  a  clean  hack-saw  producing 
fine  "  sawings,"  are  added  15  cc.  concentrated  hydrochloric  acid.  The  solution 


Quantitative  Chemical  Analysis,  "  5th  Ed,  by  J.  C.  Olsen.     D.  Van  Nostrand 

Ch 
659 


Company,  Publishers. 

2  Professor  in  charge  of  Department  of  Chemistry,  Cooper  Union,  New  York  City. 


660  ANALYSIS   OF  ALLOYS 

is  gently  warmed  on  the  water  bath  and  a  drop  or  two  of  concentrated  nitric  acid 
is  added  occasionally  until  solution  is  effected.  All  of  the  metals  will  be  con- 
verted into  chlorides  which  will  remain  in  solution  with  the  possible  exception  of 
lead  chloride.  An  excess  of  nitric  acid  is  to  be  avoided,  as  it  tends  to  form  insoluble 
metastannic  acid,  which  can  be  readily  distinguished  from  the  crystalline  lead 
chloride.  If  metastannic  acid  forms,  the  operation  must  be  repeated,  using  less 
nitric  acid  or  adding  it  less  frequently.  After  a  few  trials  the  correct  method  of 
adding  the  nitric  acid  is  soon  acquired. 

Lead.  The  solution  is  allowed  to  cool  and  then  stand  at  least  one-half  hour 
or  better  overnight  to  allow  the  lead  chloride  to  crystallize  out.  Ten  times  the 
volume  of  absolute  alcohol  is  then  added  in  several  portions.  After  standing  for 
about  half  an  hour,  the  lead  chloride  is  filtered  off  on  a  Gooch  crucible,  washed 
with  a  mixture  of  4  parts  of  95%  alcohol  and  1  part  of  concentrated  hydrochloric 
acid,  and  finally  with  pure  alcohol.  It  is  dried  for  three  hours  at  150°  and  weighed. 
The  great  advantage  of  this  method  of  separating  the  lead  is  that  the  very  trouble- 
some treatment  of  the  sulphides  of  the  metals  present  with  sodium  or  potassium 
sulphide  is  avoided.  The  most  difficult  part  of  the  operation  is  the  solution  of  the 
alloy. 

Copper  and  Iron.  The  filtrate  from  the  lead  chloride  is  heated  until  the  alcohol 
is  expelled.  Two  grams  of  tartaric  acid  and  an  excess  of  ammonia  are  added 
and  the  solution  warmed  until  the  precipitate  dissolves.  By  the  addition  of  5  cc. 
of  saturated  hydrogen-sulphide  water,  the  copper  and  the  small  amount  of  lead 
still  unprecipitated  as  well  as  a  trace  of  iron  which  may  be  present  may  be  pre- 
cipitated without  bringing  down  any  of  the  tin  and  antimony.  The  solution  is 
warmed  and  when  the  dark-colored  precipicate  has  settled,  1  cc.  of  the  hydrogen- 
sulphide  water  is  added  to  the  clear  supernatant  liquid.  If  no  further  precipi- 
tate is  produced,  the  solution  is  filtered  and  the  precipitate  washed  with  water 
containing  hydrogen  sulphide. 

The  precipitate  is  dissolved  in  a  little  warm  dilute  nitric  acid  and  the  lead 
separated  as  sulphate,  the  nitric  acid  being  expelled  by  evaporation  after  the 
addition  of  sulphuric  acid.  The  copper  is  precipitated  from  the  filtrate  as  sulphide 
and  if  small  in  amount  may  be  ignited  and  weighed  as  oxide.  If  considerable 
copper  is  present  it  must  be  weighed  as  sulphide  or  without  precipitation  as  sul- 
phide may  be  separated  electrolytically  from  the  iron.  One  or  2  cc.  concentrated 
nitric  acid  are  added  and  a  current  of  one-half  ampere  passed  until  all  the  copper 
is  precipitated.  The  iron  may  then  be  precipitated  with  ammonia  and  weighed  as 
oxide. 

Separation  of  Antimony  and  Tin.  The  solution  of  antimony  and  tin  is  acidi- 
fied with  hydrochloric  acid,  hydrogen  sulphide  passed,  and  the  precipitate  filtered 
off  and  washed  two  or  three  times.  A  hole  is  made  in  the  point  of  the  filter-paper 
by  means  of  a  glass  rod  and  the  bulk  of  the  precipitate  washed  into  a  beaker  with 
a  little  water.  Warm  dilute  hydrochloric  acid  is  poured  over  the  paper  to  dissolve 
the  portion  of  the  precipitate  still  adhering  to  the  paper.  The  precipitate  in  the 
beaker  is  dissolved  by  warming  and  adding  concentrated  hydrochloric  acid.  The 
hydrogen  sulphide  is  decomposed  by  the  addition  of  a  crystal  of  potassium  chlorate 
and  warming.  Some  pure  metallic  iron  is  added  and  the  solution  heated  on  the 
water  bath  for  about  one-half  hour  or  until  the  iron  is  nearly  dissolved.  The  pre- 
cipitated antimony  is  filtered  off  on  a  Gooch  crucible,  a  little  iron  having  been 
sprinkled  on  the  asbestos.  The  precipitate  is  washed  with  boiled  water  to  which 
considerable  hydrochloric  acid  has  been  added. 


ANALYSIS  OF  ALLOYS  661 

The  antimony  is  dissolved  in  hydrochloric  acid  to  which  a  little  potassium 
chlorate  has  been  added.  The  solution  is  warmed  to  expel  chlorine  and,  after  the 
addition  of  tartaric  acid  and  water,  hydrogen  sulphide  is  passed.  The  antimony 
sulphide  is  filtered  off  and  washed  with  water  containing  a  little  hydrogen  sulphide. 
The  moist  precipitate  is  rinsed  into  a  capacious  porcelain  crucible  with  water.  The 
small  portion  still  adhering  to  the  paper  is  dissolved  in  a  little  warm  ammonium 
sulphide  and  the  solution  allowed  to  flow  into  the  crucible.  The  solution  is 
evaporated  on  the  water  bath  after  the  addition  of  a  few  cc.  of  concentrated  nitric 
acid.  If  sulphur  separates,  a  little  liquid  bromine  is  added  when  the  solution  has 
become  quite  concentrated.  When  the  globule  of  sulphur  has  disappeared,  expel 
the  excess  of  nitric  acid  by  heating  on  the  hot  plate  or  with  the  Bunsen  burner, 
finally  heating  to  full  redness.  Cool  a  little,  sprinkle  some  ammonium  carbonate 
over  the  precipitate,  and  ignite  again  to  completely  expel  sulphuric  acid  and  weigh 
as  antimony  tetroxide,  Sb204. 

The  antimony  may  also  be  weighed  ay  the  trisulphide,  Sb2S3.  The  precipitate 
is  filtered  on  a  weighed  Gooch  crucible,  and  heated  to  230°  in  a  stream  of  carbon 
dioxide  to  exclude  oxygen  until  constant. 

Tin.  To  precipitate  the  tin  in  the  filtrate  from  the  antimony  the  excess  of 
hydrochloric  acid  is  neutralized  with  ammonia,  the  solution  diluted  somewhat, 
warmed,  and  hydrogen  sulphide  passed  until  the  tin  is  entirely  precipitated.  The 
stannous  sulphide  is  washed  with  water  containing  hydrogen  sulphide  and  a  few 
grams  of  ammonium  sulphate.  It  is  dried  and  detached  from  the  paper  which  is 
burned.  The  precipitate  and  the  ash  are  placed  in  a  weighed  porcelain  crucible 
and  heated  very  gently  with  free  access  of  air  until  sulphur  dioxide  ceases  to  be 
given  off.  The  oxidation  may  be  assisted  by  the  addition  of  a  few  drops  of  nitric 
acid.  Finally  the  precipitate  is  strongly  heated  to  expel  sulphuric  acid,  which 
is  completely  removed  by  the  addition  of  a  little  ammonium  carbonate  and  again 
igniting.  It  is  weighed  as  stannic  oxide,  Sn02. 

Arsenic.  As  only  a  trace  of -arsenic  is  present,  a  5-  or  10-gram  portion  of  the 
alloy  should  be  taken  for  its  determination.  Dissolve  in  hydrochloric  acid  and 
potassium  chlorate  and  warm  to  expel  the  chlorine.  Filter  off  the  lead  chloride  on 
asbestos  and  wash  a  few  times  with  dilute  hydrochloric  acid.  Add  one-third  the 
volume  of  concentrated  hydrochloric  acid  and  pass  hydrogen  sulphide.  Filter  off  the 
precipitate  consisting  of  the  sulphides  of  copper  and  arsenic  on  asbestos,  wash  with 
hot  water  containing  hydrogen  sulphide  and  a  little  hydrochloric  acid.  Dissolve 
the  arsenic  sulphide  by  washing  the  precipitate  with  a  little  warm  dilute  ammonia. 
Evaporate  the  solution  nearly  to  dryness  in  a  porcelain  dish.  Oxidize  the  arsenic 
by  warming  with  concentrated  nitric  acid,  dilute  the  solution  somewhat,  neutralize 
with  filtered  ammonia,  and  add  magnesia  mixture.  After  standing  twenty-four 
hours  filter,  wash,  ignite,  and  weigh  as  magnesium  pyroarsenate  according  to  the 
directions  given  in  chapter  on  Arsenic.  See  Distillation  Method  in  Appendix. 

Analysis  of  Soft  Solder 

Alloy  of  Lead  and  Tin,  Generally  Containing  Small  Amounts  of  Arsenic, 
Antimony,  Iron,  and  Zinc 

Solution  of  the  Alloy.  One  gram  of  the  alloy  is  weighed  out  and  transferred 
to  a  beaker  of  about  500-cc.  capacity.  Ten  cc.  of  concentrated  nitric  acid  and 
5  cc.  of  water  are  added.  The  beaker  is  covered  with  a  watch-crystal  and  heated 


662  ANALYSIS   OF   ALLOYS 

on  the  water  bath  until  the  alloy  is  completely  decomposed  and  the  nitrous  fumes 
are  entirely  expelled.  One  hundred  cc.  of  water  are  added  and  the  solution  boiled 
for  five  minutes  and  allowed  to  settle  for  one  hour.  The  stannic  oxide  is  filtered  off 
and  washed  with  hot  water.  The  moist  precipitate  may  be  introduced  into  a 
weighed  porcelain  crucible,  the  paper  burned  in  the  usual  manner,  and  finally 
heated  to  redness  for  ten  minutes. 

Tin.  When  the  precipitate  has  been  brought  to  constant  weight,  it  is  fused 
with  six  times  its  weight  of  a  mixture  of  equal  parts  of  sulphur  and  sodium  car- 
bonate. The  fused  mass  is  dissolved  in  hot  water  and  the  solution  filtered.  The 
insoluble  sulphides  are  washed  with  hot  water  and  treated  with  a  little  dilute 
hydrochloric  acid  and  the  paper  washed  with  water.  If  copper  is  present  it  will 
remain  on  the  paper  and  the  small  amount  present  may  be  weighed  as  CuO  after 
burning  the  paper  in  a  porcelain  crucible  and  igniting  the  precipitate.  The  lead 
is  precipitated  by  the  addition  of  a  few  drops  of  sulphuric  acid  and  25  cc.  of  alcohol 
to  the  solution,  which  should  not  exceed  50  cc.  After  standing  one  hour,  the  pre- 
cipitate is  filtered  off  on  a  Gooch  crucible,  washed  with  alcohol,  dried  on  the  hot 
plate,  and  weighed.  The  filtrate  is  evaporated  until  the  alcohol  is  completely 
expelled.  Any  iron  present  is  precipitated  with  ammonia  and  weighed.  Hydrogen 
sulphide  is  passed  through  the  filtrate  to  precipitate  any  zinc  present,  which  is 
filtered  off.  The  filtrate  from  the  insoluble  sulphides  will  contain  the  tin  as  a 
thiostannate  and  part  of  the  antimony  present  in  the  alloy  as  a  thioantimonate. 
The  solution  is  boiled  after  the  addition  of  caustic  soda  and  hydrogen  peroxide 
until  it  is  nearly  decolorized.  On  acidifying  and  passing  hydrogen  sulphide  both 
metals  are  precipitated  as  sulphides.  If  antimony  is  present  the  metals  should  be 
separated  by  the  method  given  under  Analysis  of  Type  Metal,  page  660.  The 
weight  of  the  impurities  found,  computed  as  oxides,  is  deducted  from  the  weight  of 
the  impure  stannic  oxide. 

Lead.  The  filtrate  from  the  stannic  oxide  is  transferred  to  a  porcelain  dish, 
5  cc.  concentrated  sulphuric  acid  added,  and  evaporated  until  fumes  of  sulphuric 
acid  are  evolved.  Cool  the  dish  by  floating  it  in  cold  water  and  add  cautiously 
75  cc.  of  water.  Stir  thoroughly  and  add  25  cc.  of  alcohol.  Allow  the  solution  to 
stand  for  at  least  one  hour,  filter  off  the  lead  sulphate  on  a  weighed  Gooch  crucible, 
wash  with  alcohol  until  free  from  acid,  dry  on  the  hot  plate,  and  weigh. 

Arsenic  and  Antimony.  The  alcohol  is  completely  expelled  from  the  filtrate 
by  evaporation  and  any  arsenic  present  precipitated  by  passing  hydrogen  sulphide. 
If  this  precipitate  is  of  an  orange  color  instead  of  pure  yellow,  antimony  is  present. 
It  should  be  filtered  off  and  washed  with  water  containing  a  little  hydrochloric 
acid  until  free  from  iron  and  hydrogen  sulphide.  It  is  then  washed  with  small 
portions  of  concentrated  ammonium  carbonate  solution  until  the  arsenic  sulphide 
is  entirely  dissolved.  The  arsenic  is  reprecipitated  by  acidifying  the  solution  with 
hydrochloric  acid  and  passing  hydrogen  sulphide.  It  is  filtered  off  on  a  Gooch 
crucible  and  washed  with  water  containing  hydrogen  sulphide  and  a  little  hydro- 
chloric acid.  The  water  is  removed  by  alcohol  and  the  precipitate  digested  with 
carbon  disulphide  until  sulphur  is  entirely  removed.  The  arsenic  sulphide  is  dried 
at  100°  and  weighed.  If  antimony  is  absent  the  treatment  with  ammonium  car- 
bonate is  omitted,  the  precipitate  being  filtered  off  on  a  Gooch  crucible,  washed, 
dried,  and  weighed.  If  antimony  is  present  it  is  ignited  and  weighed  as  directed 
in  page  660  under  the  Analysis  of  Type  Metal. 

Iron.  A  few  drops  of  bromine  water  are  added  and  the  solution  is  boiled  to  oxi- 
dize the  iron  and  to  expel  the  hydrogen  sulphide.  The  iron  is  then  precipitated  by 


ANALYSIS   OF  ALLOYS  663 

making  the  filtrate  alkaline  with  filtered  ammonia  and  warming  for  a  few  minutes. 
It  is  filtered  off  on  a  small  paper  and  dissolved  by  adding  a  few  drops  of  dilute 
hydrochloric  acid.  The  paper  is  washed  with  about  75  cc.  of  water  in  small  por- 
tions. The  iron  is  reprecipitated  and  filtered  on  the  same  paper  after  moistening 
with  a  few  drops  of  ammonia.  After  washing  free  from  chlorides,  the  moist  paper 
is  transferred  to  the  weighed  platinum  crucible  and  ignited. 

Zinc.  Hydrogen  sulphide  is  passed  into  the  combined  filtrates  to  precipitate 
any  zinc  present,  which  is  filtered  off,  washed,  and  weighed  as  sulphide  after 
ignition  with  sulphur  in  a  stream  of  hydrogen. 

Analysis  of  Rose's  Metal 

Alloy  of  Lead,  Bismuth,  and  Tin,  Generally  Containing  Small  Amounts  of 
Copper,  Arsenic,  Antimony,  Iron  and  Zinc 

One  gram  of  the  metal  is  weighed  out  and  decomposed  with  nitric  acid  and  the 
stanric  cxide  is  weighed,  according  to  the  procedure  under  analysis  of  soft 
solder,  page  662. 

Lead.  To  the  filtrate  from  the  stannic  oxide  containing  the  nitrates  of  lead  and 
bismuth,  5  cc.  concentrated  sulphuric  acid  are  added.  The  solution  is  evapo- 
rated in  a  porcelain  dish  until  sulphuric-acid  fumes  are  given  off.  The  dish  may  be 
placed  on  the  hot  plate,  sand  bath,  or  wire  gauze  and  the  liquid  heated  to  just 
below  the  boiling-point  to  avoid  spattering.  When  the  acid  becomes  concentrated, 
the  heat  may  be  somewhat  increased.  The  hot  concentrated  solution  is  diluted 
by  slowly  pouring  it  with  constant  stirring  into  about  100  cc.  of  water  and  digested 
hot  for  about  half  an  hour  with  occasional  stirring.  The  lead  sulphate  is  then 
filtered  off  on  a  Gooch  crucible,  washed  with  10%  sulphuric  acid  until  the  wash- 
water  no  longer  gives  a  precipitate  on  making  it  alkaline  with  ammonia,  adding 
ammonium  carbonate,  and  warming.  The  sulphuric  acid  is  then  washed  out  with 
alcohol.  The  precipitate  is  dried  and  weighed.  It  is  tested  for  a  possible  contam- 
ination with  bismuth  as  follows :  It  is  dissolved  in  5  to  10  cc.  of  warm  concentrated 
hydrochloric  acid  and  50  cc.  of  absolute  alcohol  are  added  to  the  solution.  After 
standing  for  a  few  moments,  the  solution,  containing  the  bismuth  as  chloride,  is 
filtered  off.  By  nearly  neutralizing  with  ammonia,  and  largely  diluting  with  water, 
the  bismuth  is  precipitated  as  oxychloride  and  may  be  washed  with  water  contain- 
ing a  few  drops  of  hydrochloric  acid,  dried,  and  weighed. 

Bismuth.  In  the  filtrate  from  the  lead  sulphate,  the  bismuth  is  precipitated  by 
just  neutralizing  with  filtered  ammonia,  adding  a  few  drops  of  ammonium  carbonate 
and  warming  the  solution  gently  for  about  fifteen  minutes.  The  precipitate  is 
filtered  off  and  washed  a  few  times  with  water.  To  free  the  precipitate  from  a  small 
amount  of  basic  sulphate  it  is  dissolved  in  a  small  amount  of  dilute  nitric  acid  and 
reprecipitated.  The  precipitate  is  washed  with  water  containing  a  little  ammonium 
nitrate  and  dried.  It  is  removed  from  the  paper  as  completely  as  possible  and 
placed  on  a  watch-crystal.  The  paper  is  replaced  in  the  funnel,  moistened  with  a 
few  drops  of  dilute  nitric  acid,  and  washed  with  small  amounts  of  warm  water. 
The  wash-water  is  evaporated  to  dryness  in  a  fairly  large  weighed  porcelain  cruci- 
ble, and  the  residue  ignited  until  the  nitric  acid  is  completely  expelled.  The  main 
portion  of  the  precipitate  is  now  added,  heated  with  the  Bunsen  burner  and 
weighed  as  Bi203. 
Copper.  If  copper  is  present  in  the  alloy,  it  will  be  contained  in  the  two 


664  ANALYSIS   OF  ALLOYS 

filtrates  from  the  bismuth  precipitate.  Combine  these  filtrates,  acidify  with 
hydrochloric  acid,  and  concentrate  to  a  convenient  bulk.  Pass  hydrogen 
sulphide  through  the  warm  solution,  filter,  and  wash  with  water  containing  hydro- 
gen sulphide.  Even  if  copper  is  absent,  a  small  black  precipitate  of  bismuth 
sulphide  will  be  obtained  at  this  point  because  of  the  slight  solubility  of  the  bismuth 
hydroxide  or  carbonate.  The  precipitate  may  be  tested  for  bismuth  by  treating 
with  a  little  dilute  hydrochloric  acid  and  diluting  the  filtrate.  A  white  precipitate 
indicates  bismuth.  The  copper  sulphide,  being  insoluble  in  dilute  hydrochloric 
acid,  remains  on  the  paper  and  may  be  ignited  together  with  the  pa  T  and  weighed 
as  oxide.  If  arsenic,  antimony,  iron  or  zinc  are  present  they  "e  separated 
and  determined  by  the  methods  given  under  pages  660,  661  and  669. 

Analysis  of  Wood's  Metal 

Alloy  of  Lead,  Bismuth,  Tin,  and  Cadmium,   Generally  Containing  Small 
Amounts  of  Copper,  Arsenic,  Antimony,  Iron  and  Zinc 

One  gram  of  the  metal  is  weighed,  dissolved  in  nitric  acid,  and  the  stannic 
oxide  weighed  and  purified.  The  filtrate  from  the  tin  is  evaporated  to  dryness  on 
a  water  bath.  The  nitrates  are  converted  into  chlorides  by  evaporating  twice 
on  the  water  bath  to  a  small  bulk  after  the  addition  of  20  cc.  of  concentrated  hydro- 
chloric acid. 

Lead.  After  cooling,  25  cc.  absolute  alcohol  are  added.  The  mixture  is  stirred 
and  after  standing  some  time  the  chloride  of  lead  is  filtered  off  on  a  Gooch  crucible, 
and  washed  with  an  ice-cold  mixture  of  4  parts  of  95%  alcohol  and  1  part  of  con- 
centrated hydrochloric  acid.  It  is  dried  on  the  hot  plate  or  at  150°  for  three  hours 
and  weighed. 

Bismuth.  The  filtrate  is  diluted  with  about  one-half  liter  of  water  and  nearly 
neutralized  with  ammonia  (about  40  cc.  of  dilute  ammonia  will  be  required). 
After  standing  twenty-four  hours  the  bismuth  oxychloride  is  filtered  off  on  a  Gooch 
crucible,  washed  with  water  containing  a  few  drops  of  dilute  hydrochloric  acid, 
dried  at  110°,  and  weighed  as  BiOCl. 

The  bismuth  may  also  be  precipitated  as  bismuth  hydroxide  by  volatilizing 
most  of  the  alcohol,  neutralizing  with  ammonia  and  warming  gently.  If  iron  is 
present  this  precipitate  will  be  reddish.  In  that  case  it  is  best  to  dissolve  it  in 
hydrochloric  acid  and  precipitate  the  bismuth  as  oxychloride.  The  bismuth 
hydroxide  is  ignited  and  weighed  as  oxide,  Bi203. 

Cadmium.  The  filtrate  from  the  bismuth  oxychloride  is  evaporated  to  a  bulk 
of  200  or  300  cc.  If  the  bismuth  has  been  precipitated  by  means  of  ammonia, 
the  filtrate  is  first  acidified  with  hydrochloric  acid  and  evaporated  to  a  moderate 
bulk.  The  solution  is  saturated  with  hydrogen  sulphide  and  the  precipitate 
filtered  off  and  washed  with  water  containing  hydrogen  sulphide.  If  the  cadmium 
sulphide  is  dark  colored  or  black,  traces  of  lead  or  bismuth  sulphides  may  be  present 
because  of  incomplete  separations,  or  copper  may  have  been  present  in  the  alloy. 
Any  arsenic  which  may  have  been  in  the  alloy  or  a  trace  of  tin  or  antimony  will 
also  be  present  in  this  precipitate. 

Arsenic,  Antimony,  and  Tin.  It  should  be  tested  for  these  three  elements  by 
pouring  over  it  a  few  drops  of  warm  potassium  or  sodium  sulphide  and  washing 
two  or  three  times  with  warm  water,  being  careful  to  stir  up  the  precipitate  with 
the  stream  of  water  from  the  wash-bottle.  A  precipitate  formed  on  acidifying  the 


ANALYSIS   OF  ALLOYS  665 

filtrate  indicates  the  presence  of  arsenic,  antimony,  or  tin.  If  the  characteristic 
orange  color  of  antimony  is  absent,  the  supernatant  liquid  should  be  decanted  and 
the  precipitate  warmed  with  a  little  concentated  hydrochloric  acid.  If  it  dissolves 
completely,  arsenic  is  absent  and  the  tin  may  be  reprecipitated  by  diluting  and  pass- 
ing hydrogen  sulphide.  After  washing,  the  moist  precipitate  with  the  paper  may 
be  burned  and  the  sulphide  of  tin  converted  into  oxide  by  ignition.  If  arsenic  or 
antimony  is  present,  it  may  be  determined  as  directed  in  the  Analysis  of  Type 
Metal,  page  660. 

Separation  of  Copper  and  Cadmium.  To  dissolve  out  any  copper  which  may 
be  present  with  the  cadmium  sulphide,  a  few  drops  of  potassium  cyanide  should 
be  poured  over  the  precipitate.  It  should  be  thoroughly  stirred  up  with  water  and 
washed  a  few  times.  If  a  considerable  amount  of  copper  is  present,  the  bulk  of 
the  precipitate  should  be  transferred  to  a  beaker  by  washing  out  the  paper  while 
still  in  the  funnel  with  a  stream  of  water.  The  remainder  of  the  precipitate  on  the 
paper  is  dissolved  by  washing  with  a  little  warm  dilute  nitric  acid.  The  paper  is 
then  thoroughly  washed  with  small  portions  of  hot  water.  The  washings  are 
allowed  to  flow  into  the  beaker  containing  the  main  portion  of  the  precipitate. 
The  beaker  is  warmed  and  more  nitric  acid  is  added  if  necessary  to  dissolve  the 
precipitate.  The  solution  is  neutralized  with  sodium  carbonate  and  a  slight 
excess  of  potassium  cyanide  added.  A  small  white  precipitate  at  this  point  may 
be  lead  or  bismuth  carbonates,  which  should  be  filtered  off  and  determined.  On 
passing  hydrogen  sulphide  through  the  filtrate,  the  cadmium  is  precipitated  as 
sulphide  and  may  be  filtered  off  on  a  Gooch  crucible  and  washed  with  water  con- 
taining a  little  hydrogen  sulphide.  It  is  finally  washed  with  pure  water  and  the 
free  sulphur  extracted  by  washing  with  alcohol  and  then  with  carbon  disulphide. 
The  precipitate  is  dried  at  100°  and  weighed. 

Copper.  The  filtrate  from  the  cadmium  sulphide  contains  the  copper  and  is 
acidified  !  with  sulphuric  acid  and  a  little  nitric  acid  and  evaporated  to  fumes. 
The  residue  is  dissolved  in  water,  filtered  if  necessary,  and  the  copper  precipitated 
as  sulphide.  If  it  is  small  in  amount  it  may  be  ignited  and  weighed  as  oxide.  If 
considerable  copper  is  present,  it  must  be  ignited  with  sulphur  in  a  stream  of  hydro- 
gen and  weighed  as  cuprous  sulphide,  Cu2S.  When  much  copper  is  present,  it  is 
better  to  determine  it  electrolytically. 

Separation  of  Iron  and  Zinc.  The  filtrate  from  the  first  precipitation  with 
hydrogen  sulphide  contains  any  zinc  or  iron  which  may  have  been  present.  These 
metals  may  be  separated  in  the  following  manner : 

The  solution  is  boiled  to  expel  hydrogen  sulphide,  neutralized  with  ammonia, 
and  acidified  with  acetic  acid.  Hydrogen  sulphide  is  passed  for  some  time  and  the 
solution  allowed  to  stand  for  several  hours.  The  clear  liquid  is  carefully  decanted 
through  a  filter  paper,  and  after  replacing  the  beaker  containing  the  clear  filtrate 
with  another  beaker,  the  sulphide  of  zinc  is  brought  on  the  paper  and  washed  with 
water  containing  ammonium  acetate  and  acetic  acid.  The  precipitate  is  dissolved 
in  a  little  dilute  nitric  acid  and  the  paper  washed  with  hot  water.  The  solution  of 
the  zinc  is  evaporated  to  dryness  in  a  weighed  porcelain  crucible,  ignited  finally 
over  the  blast-lamp  to  decompose  any  zinc  sulphate  which  may  have  been  formed, 
and  weighed  as  oxide.  The  filtrate  is  boiled  to  expel  the  hydrogen  sulphide.  A 
little  nitric  acid  is  then  added  to  oxidize  the  iron,  which  is  precipitated  with 

1  This  should  be  done  under  a  hood  with  good  draught  to  avoid  any  possibility  of 
inhaling  the  very  poisonous  hydrocyanic-acid  fumes. 


666  ANALYSIS  OF  ALLOYS 

ammonia  and  weighed  as  oxide.  A  very  convenient  method  of  oxidizing  the  iron 
and  removing  the  hydrogen  sulphide  is  by  the  use  of  bromine  water.  The  bro- 
mine should  be  added  until  the  solution  is  colored,  indicating  complete  oxidation 
of  the  iron  and  the  presence  of  an  excess  of  bromine.  If  a  solution  of  bromine 
in  concentrated  hydrochloric  acid  is  used  a  few  drops  will  suffice  and  the  solution 
will  not  be  diluted  to  any  extent.  If  manganese  is  to  be  removed  together  with 
iron,  the  presence  of  an  excess  of  bromine  is  advantageous;  otherwise  it  must 
be  boiled  out.  As  the  bromine  oxidizes  hydrogen  sulphide  in  the  cold,  the  excess 
of  the  latter  need  not  be  boiled  out. 

Analysis  of  Britannia  Metal 

Alloy  of  Tin,  Antimony,  and  Copper,  with  Small  Amounts  of  Bismuth, 

Lead,  and  Iron 

Decomposition  of  the  Alloy  by  Means  of  Chlorine.  Alloys  containing  a  large 
percentage  of  tin  are  best  decomposed  by  a  stream  of  chlorine.  The  method  is 
applicable  to  alloys  containing  less  than  15%  of  lead  and  copper. 

A  hard-glass  combustion-tube  70  cm.  long  is  taken  and  one  end  drawn  out, 
making  a  small  tube  20  cm.  long,  which  is  bent  at  right  angles.  This  small  tube 
is  connected  by  means  of  a  cork  stopper  with  a  Peligot  tube  the  bulbs  of  which  are 
nearly  filled  with  dilute  hydrochloric  acid  (1:3)  containing  about  1  gram  of  tar- 
taric  acid.  A  second  Peligot  tube  is  connected  with  the  first  and  contains  a  solu- 
tion of  caustic  soda  (1  :  3).  The  chlorine  is  evolved  in  a  2-liter  flask  containing 
pieces  of  pyrolusite,  over  which  concentrated  hydrochloric  acid  is  poured.  The 
flask  is  heated  on  a  water  bath.  The  chlorine  is  passed  through  a  wash-bottle 
containing  water  and  then  through  two  wash-bottles  containing  sulphuric  acid. 
It  is  then  passed  into  the  combustion-tube,  connection  being  made  by  means  of 
a  cork  stopper.  Wherever  rubber  is  used  for  making  connections,  it  must  be  well 
coated  with  paraffin.  This  is  also  advisable  for  the  cork  stoppers.  The  chlorine 
is  not  allowed  to  pass  into  the  combustion-tube  until  all  of  the  air  has  been  displaced 
from  the  flask  and  the  wash-bottles.  All  escaping  chlorine  should  be  absorbed 
in  caustic-soda  solution. 

One  gram  of  the  alloy  in  fine  turnings  is  weighed  out  and  placed  in  a  porcelain 
boat  which  is  placed  in  the  middle  of  the  combustion-tube.  The  chlorine  is  first 
allowed  to  act  on  the  alloy  in  the  cold.  When  no  further  action  is  observed,  the 
part  of  the  tube  in  which  the  boat  is  situated  is  heated  gently  with  the  Bunsen 
burner,  and  then  more  strongly  until  the  contents  of  the  boat  fuse.  The  chlo- 
rides of  mercury,  bismuth,  arsenic,  antimony,  and  tin  volatilize  and  are  driven 
out  of  the  tube  by  heating  it  gently  from  the  boat  to  the  end  which  is  drawn  out. 
These  chlorides  are  absorbed  in  the  hydrochloric  acid  contained  in  the  first  Peligot 
tube,  while  the  excess  of  chlorine  is  absorbed  in  the  caustic-soda  solution  contained 
in  the  second  Peligot  tube. 

The  chlorine  in  the  apparatus  is  then  displaced  by  means  of  a  stream  of  dry 
air  or  carbon  dioxide,  the  chlorine  generator  having  been  removed.  The  appara- 
tus is  disconnected,  the  boat  containing  the  chlorides  of  copper,  lead,  and  iron  is 
placed  in  a  porcelain  dish,  and  the  tube  washed  out  with  hot  water  which  is  allowed 
to  flow  into  the  dish  containing  the  boat.  Hydrochloric  acid  is  added  and  the  dish 
wanned  until  the  contents  of  the  boat  are  dissolved.  The  latter  is  removed  and 
washed. 


ANALYSIS   OF   ALLOYS  667 

Lead,  Copper,  and  Iron.  The  lead  is  precipitated  by  evaporation  with  sul- 
phuric acid  and  diluting  and  is  filtered  off  and  weighed  as  sulphate.  The  copper 
is  precipitated  by  means  of  hydrogen  sulphide  and  weighed  as  sulphide  or  deter- 
mined electrolytically  from  a  nitric  acid  solution.  The  iron  is  precipitated  by 
means  of  ammonia  and  weighed  as  oxide. 

The  contents  of  the  first  Peligot  tube  are  poured  into  a  beaker  and  the  Peli- 
got  tube  well  washed  out  with  water  to  which  hydrochloric  acid  is  added  if  neces- 
sary. The  solution  is  warmed  and  hydrogen  sulphide  passed  until  precipitation 
is  complete.  The  filtrate  should  be  heated  to  boiling,  strong  hydrochloric  acid 
added,  and  hydrogen  sulphide  passed  again  to  precipitate  the  arsenic. 

Bismuth.  If  the  sulphide  precipitate  is  dark  colored,  bismuth  is  present. 
The  precipitate  is  washed  into  a  beaker,  ammonium  sulphide  added,  and  the 
solution  warmed.  The  solution  is  filtered  through  the  same  paper  and  the  pre- 
cipitate washed  with  warm  water  containing  a  little  ammonium  sulphide.  The 
bismuth  sulphide  is  dissolved  in  a  little  warm  dilute  nitric  acid  and  the  paper 
washed.  The  bismuth  is  precipitated  with  ammonia  and  ammonium  carbonate, 
ignited,  and  weighed  as  oxide,  Bi203. 

Separation  of  Tin  from  Arsenic  and  Antimony.  The  ammonium-sulphide 
solution  of  arsenic,  antimony,  and  tin  is  poured  with  vigorous  stirring  into  a  hot 
solution  of  25  grams  of  oxalic  acid  in  200  cc.  of  water.  The  solution  is  heated  to 
boiling  and  hydrogen  sulphide  passed  for  about  fifteen  minutes.  The  precipitate 
is  filtered  off  immediately  and  washed  with  hot  water  containing  hydrogen  sul- 
phide. It  is  dissolved  in  ammonium  sulphide  and  the  treatment  with  hot  oxalic 
acid  and  hydrogen  sulphide  repeated. 

Tin.  The  oxalic-acid  solution  of  tin  is  evaporated  down,  with  the  addition  of 
5  cc.  concentrated  sulphuric  acid,  to  fumes.  The  solution  is  cooled,  cautiously 
diluted  with  water,  and  hydrogen  sulphide  passed  to  insure  complete  precipita- 
tion of  the  tin.  Wash  the  precipitate  with  water  containing  ammonium  acetate 
and  a  little  acetic  acid,  dry,  ignite,  and  weigh  as  stannic  oxide,  Sn02. 

Arsenic  and  Antimony.  The  precipitate  of  arsenic  and  antimony  sulphides 
is  treated  with  a  little  concentrated  ammonium-carbonate  solution  and  washed 
to  remove  arsenic.  The  antimony  is  then  weighed  as  oxide  according  to  the  direc- 
tions given  under  the  Analysis  of  Type  Metal,  page  660.  The  arsenic  is  deter- 
mined according  to  the  directions  given  in  the  same  section. 

Analysis  of  Brass  or  Bronze 

Alloy   of   Lead,    Copper,    Tin,    and   Zinc,  with  Small  Amounts  of  Arsenic, 
Antimony,  Cadmium,  and  Iron. 

Solution  of  the  Alloy.  Weigh  out  1  gram  of  the  alloy  and  place  in  a  300-cc. 
beaker,  add  10  cc.  concentrated  nitric  acid  and  5  cc.  water.  Cover  the  beaker 
with  a  watch-crystal  and  place  in  a  dish  of  cold  water.  After  one-half  hour  place 
the  beaker  on  the  water  bath  and  evaporate  the  solution  to  dryness.  One  hun- 
dred cc.  of  boiling  water  and  a  few  drops  of  nitric  acid  are  added  and  the  solution 
boiled  for  five  minutes. 

Tin.  The  stannic  oxide  is  filtered  off  and  washed  with  hot  water.  The  moist 
precipitate  is  introduced  into  a  weighed  porcelain  crucible  and  the  paper  burned 
in  the  usual  manner.  If  the  amount  of  tin  is  small  (less  than  1%)  it  is  weighed 
at  this  point,  otherwise  it  is  fused  with  six  times  its  weight  of  a  mixture  of  equal 


668  ANALYSIS   OF   ALLOYS 

parts  of  sulphur  and  sodium  carbonate.  The  fused  mass  is  dissolved  in  hot  water 
and  the  solution  filtered.  The  copper,  lead,  and  iron  which  were  carried  down  with 
the  stannic  oxide  will  remain  on  the  paper  as  sulphides,  while  the  filtrate  will  con- 
tain all  of  the  tin  and  any  arsenic  or  antimony  which  may  have  been  present.  The 
insoluble  sulphides  are  dissolved  in  a  little  nitric  acid,  the  paper  washed,  and  the 
solution  added  to  the  filtrate  from  the  stannic  oxide. 

If  arsenic  and  antimony  are  absent,  the  tin  may  be  precipitated  out  of  the 
sodium  sulphide  solution  and  weighed.  The  excess  of  sulphur  should  first  be  re- 
moved from  the  solution  by  heating  to  boiling  after  the  addition  of  caustic  soda 
and  then  adding  hydrogen  peroxide  in  small  quantities  until  the  solution  is  nearly 
decolorized.  It  is  then  acidified  with  hydrochloric  acid  while  stirring  constantly, 
heated,  and  hydrogen  sulphide  passed.  The  stannic  sulphide  is  washed  with  hot 
water  containing  ammonium  acetate  and  a  little  acetic  acid.  It  is  ignited  and 
weighed  as  stannic  oxide  in  the  usual  manner. 

Arsenic  and  Antimony.  If  arsenic  is  present  in  the  alloy,  a  small  amount  of 
this  element  will  be  present  in  the  sodium  sulphide  solution  of  the  tin  and  will 
be  precipitated  with  the  stannic  sulphide.  It  may  be  removed  by  treating  the 
precipitate  with  a  little  concentrated  solution  of  ammonium  carbonate  and  wash- 
ing. The  solution  of  arsenic  should  be  added  to  the  nitric  acid  solution  of  the 
alloy. 

If  antimony  is  also  present  in  the  alloy,  the  sulphides  of  arsenic,  antimony, 
and  tin  must  be  separated  by  one  of  the  methods  given  under  Analysis  of  Type 
Metal,  page  660.  See  also  Distillation  Method  for  Arsenic  and  Antimony  in 
Appendix. 

Lead.  To  filtrate  from  the  stannic  oxide,  5  cc.  concentrated  sulphuric  acid 
are  added  and  the  solution  evaporated  in  a  porcelain  dish  until  the  nitric  acid  is 
entirely  expelled  and  white  fumes  of  sulphuric  acid  are  given  off.  The  solution 
is  cooled  by  floating  the  dish  on  cold  water  and  diluted  with  75  cc.  of  water. 
Lead  is  now  determined  as  PbS04.  See  page  236. 

Cadmium.     See  Appendix  for  determination. 

The  copper  is  best  determined  electrolytically.  The  filtrate  from  the  lead 
sulphate  is  heated  on  the  hot  plate  until  most  of  the  alcohol  is  expelled.  Two  cc. 
concentrated  nitric  acid  are  added  and  the  warm  solution  (about  60°)  electrolyzed 
with  a  current  of  \  to  1  ampere  for  about  six  hours.  If  a  gauze  electrode  is  used 
or  one  of  the  electrodes  is  rotated  the  time  required  is  very  much  reduced. 

Hydrogen  sulphide  is  passed  through  the  acid  filtrate  from  the  copper  to  pre- 
cipitate traces  of  arsenic,  antimony,  or  unseparated  tin  which  may  be  present. 
If  more  than  traces  are  found,  the  metals  must  be  separated  and  determined  by 
the  methods  given  in  the  preceding  methods.  When  the  amount  of  copper  is 
large,  as  is  generally  the  case,  it  is  advisable  to  divide  the  solution  into  two  por- 
tions for  the  electrolysis,  as  about  300  milligrams  of  copper  is  generally  sufficient 
for  a  good  determination.  The  solution  may  be  divided  by  weighing  it  and  then 
pouring  out  about  half  of  it  and  again  weighing  or  the  solution  may  be  diluted 
to  a  known  volume  as  250  or  500  cc.  and  a  portion  measured  out.  The  copper 
may  be  determined  in  each  portion  and  the  filtrates  combined  for  the  zinc  deter- 
mination. For  the  duplicate  zinc  determination  the  copper  may  be  precipitated 
as  sulphide,  which  is  filtered  off,  well  washed,  and  discarded. 

Iron.  The  filtrate  from  the  copper  is  boiled  to  expel  hydrogen  sulphide  and 
a  little  nitric  acid  added  to  oxidize  the  iron,  which  is  precipitated  with  ammonia 
and  weighed  as  oxide.  If  more  than  a  small  amount  of  iron  is  present,  the  pre- 


ANALYSIS   OF  ALLOYS 

cipitate  must  be  redissolved  and  reprecipitated  to  separate  it  completely  from  the 
zinc. 

Zinc.1  The  filtrate  from  the  iron  is  evaporated  to  small  bulk  and  the  zinc 
precipitated  and  weighed  as  pyrophosphate.  The  zinc  may  also  be  precipitated 
and  weighed  as  sulphide. 

Analysis  of  German  Silver 

Alloy  of  Copper,  Zinc,  and  Nickel,  with  Small  Amounts  of  Lead,  Iron,  and  Tin 

One  gram  of  the  alloy  is  weighed  out  and  dissolved  in  nitric  acid  as  directed 
in  the  preceding  exercise.  The  tin,  lead,  and  copper  are  determined  as  directed 
in  the  same  exercise. 

Hydrogen  sulphide  is  passed  through  the  acid  filtrate  from  the  copper  to  pre- 
cipitate traces  of  arsenic,  antimoy,  tin,  or  unseparated  copper  which  may  be  pres- 
ent. If  more  than  traces  are  found,  the  metals  must  be  separated  and  determined 
by  the  methods  given  under  Analysis  of  Type  Metal,  page  660. 

Zinc.1  The  filtrate  is  boiled  until  the  hydrogen  sulphide  is  expelled  and  the 
solution  concentrated  to  a  small  bulk  and  the  acid  nearly  neutralized  with  caustic 
soda.  Five  to  10  grams  of  caustic  soda  are  dissolved  in  about  50  cc.  of  water  and 
the  solution  of  zinc  and  nickel  added  slowly  with  constant  stirring.  The  solu- 
tion is  diluted  with  an  equal  bulk  of  water  and  the  precipitate  filtered  off  and 
washed.  The  zinc  in  the  filtrate  is  precipitated  with  hydrogen  sulphide,  filtered 
off,  and  washed  free  from  alkali.  The  zinc  sulphide  is  dried  and  detached  from  the 
paper  as  completely  as  possible. 

The  portion  still  adhering  to  the  paper  is  dissolved  in  nitric  acid  and  the  solu- 
tion evaporated  to  dryness  in  a  porcelain  crucible.  The  remainder  of  the  precip- 
itate is  added  and  the  whole  ignited  with  sulphur  in  a  stream  of  hydrogen.  If 
the  precipitate  is  small  it  need  not  be  dried,  but  is  immediately  dissolved  in  nitric 
acid  and  after  evaporation  converted  into  sulphide.  The  sulphide  is  tested  for 
alkali  by  digestion  with  hot  water.  If  alkali  is  found,  it  must  be  completely  ex- 
tracted and  the  sulphide  again  weighed  after  ignition  with  sulphur  in  hydrogen. 
The  precipitate  is  then  dissolved  in  nitric  acid  and  the  solution  evaporated  to  dry- 
ness.  The  zinc  nitrate  is  dissolved  in  water  and  the  silica  filtered  off,  washed, 
ignited,  and  weighed.  The  zinc  sulphide  may  also  be  dissolved  in  hydrochloric 
acid,  the  zinc  precipitated  as  zinc  ammonium  phosphate  and  weighed  as  pyro- 
phosphate. 

Iron  and  Nickel.  If  iron  is  absent,  the  nickel  hydroxide  may  be  washed  and 
after  transferring  the  precipitate  to  a  weighed  porcelain  crucible  and  burning  the 
paper  it  may  be  reduced  to  metallic  nickel  by  heating  in  a  stream  of  hydrogen 
and  weighed.  If  iron  is  present,  the  precipitate  is  dissolved  in  hydrochloric  acid 
and  the  iron  precipitated  with  ammonia.  Unless  a  very  small  amount  is  present 
it  must  be  redissolved  and  reprecipitated,  and,  after  washing,  is  ignited  and  weighed 
as  oxide.  The  nickel  is  then  reprecipitated  as  hydroxide  by  means  of  an  excess 
of  caustic  soda,  reduced  in  a  stream  of  hydrogen  and  weighed  as  the  metal. 

Optional  Procedure  for  Iron,  Nickel,  and  Zinc  is  given  in  the  Appendix. 

1  In  modern  practice  zinc  is  preferably  determined  by  weighing  as  oxide  or  by  titrat- 
ing with  ferro-cyanide  according  to  procedures  given  in  the  chapter  on  Zinc. 

Note  by  the  Editor. 


670  ANALYSIS   OF   ALLOYS 


Analysis  of  Manganese=Phosphorus=Bronze 

Alloy  of  Copper,  Lead,  Tin,  Zinc,  Manganese,  Phosphorus  (less  than  1%), 

Traces  of  Iron 

Solution.  One  gram  of  the  alloy  is  weighed  out  and  dissolved  in  nitric  acid. 
Nearly  all  of  the  phosphorus  remains  with  the  stannic  oxide  as  a  phosphate.  After 
fusing  the  impure  precipitate  and  separating  the  impurities,  and  precipitating  the 
tin  as  sulphide,  the  solution  containing  only  the  phosphorus  as  phosphoric  acid 
is  discarded,  as  this  element  is  determined  in  a  separate  portion  of  the  alloy. 

Lead,  Copper,  and  Zinc  are  determined  as  given  under  Analysis  of  Brass  and 
Bronze,  page  668.  The  phosphoric  acid  which  did  not  remain  with  the  stannic 
oxide  will  be  present  in  the  alkaline  solution  of  the  zinc.  This  element  should 
therefore  be  precipitated  and  weighed  as  pyrophosphate. 

Iron.  In  order  to  separate  manganese  and  iron  from  zinc,  bromine  or  hydro- 
gen peroxide  is  added  to  the  filtrate  from  the  copper.  The  solution  is  boiled  and 
excess  of  ammonium  added  to  redissolve  any  zinc  phosphate  which  may  be  pre- 
cipitated. The  precipitate  consisting  of  ferric  hydroxide  and  manganese  dioxide 
is  filtered  off  and  washed.  It  is  dissolved  in  a  little  hydrochloric  acid  and  the 
paper  well  washed.  The  solution  is  boiled  until  the  chlorine  is  completely  expelled, 
then  neutralized  with  ammonia,  warmed,  and  the  trace  of  iron  filtered  off  imme- 
diately. Unless  the  precipitate  is  very  small  it  is  redissolved  in  hydrochloric 
acid  and  again  precipitated  with  ammonia  and  quickly  filtered  off  and  washed. 
It  is  ignited  and  weighed  as  oxide. 

Manganese.  The  combined  filtrates  from  the  iron  contain  all  of  the  man- 
ganese unless  the  amount  of  iron  present  is  considerable.  The  solution  should  be 
evaporated  to  dryness  in  a  porcelain  dish  and  the  ammonium  chloride  volatilized 
by  gently  heating  with  the  Bunsen  burner.  The  residue  is  dissolved  in  a  few  cc. 
of  water  and  a  few  drops  of  hydrochloric  acid  and  the  manganese  precipitated 
and  weighed  as  sulphide. 

Volumetric  Determination  of  Iron  and  Manganese.  If  considerable  iron  is 
present,  the  method  of  separation  given  is  not  applicable.  In  this  case  the  sim- 
plest methods  of  determining  the  two  metals  are  volumetric.  The  ammonium 
precipitate  should  be  dissolved  in  sulphuric  acid  with  the  addition  of  a  little 
hydrogen  peroxide,  the  excess  of  which  may  be  expelled  by  boiling.  The  solu- 
tion must  be  made  up  to  a  definite  volume  and  divided  into  two  equal  portions. 
For  this  purpose  a  100-cc.  flask  should  be  used  which  has  been  calibrated  with  a 
50-cc.  pipette  by  emptying  the  pipette  twice  into  the  dry  flask  and  making  a  mark 
on  the  stem.  The  solution  of  iron  and  manganese  is  evaporated  to  small  bulk, 
transferred  to  the  flask,  made  up  to  the  mark  and  thoroughly  mixed.  Fifty  cc. 
are  withdrawn  with  the  dry  pipette.  The  solution  adhering  to  the  walls  of  the 
pipette  is  rinsed  out  with  distilled  water  and  added  to  the  portion  remaining  in 
the  flask.  One  of  these  portions  is  reduced  with  zinc  and  the  iron  titrated  with 
standard  permanganate.  (See  p.  219.)  The  other  portion  is  shaken  up  with 
zinc  oxide  until  the  free  acid  is  neutralized.  One  gram  of  zinc  sulphate  and  a 
drop  or  two  of  dilute  nitric  acid  are  added  and  the  solution  diluted  to  several  hun- 
dred cubic  centimeters.  The  manganese  is  titrated  with  standard  potassium 
permanganate  according  to  Volhard.  (See  page  266.) 

Phosphorus.  For  the  determination  of  phosphorus  a  5-gram  portion  of  the 
alloy  is  taken,  as  the  percentage  of  this  element  is  usually  small  (seldom  more  than 


ANALYSIS  OF  ALLOYS  671 

0.2%).  The  material  is  placed  in  a  200-cc.  beaker  and  20  to  30  cc.  concentrated 
nitric  acid  added.  The  beaker  is  covered  with  a  watch-crystal  and  after  the  first 
violent  action  of  the  acid  has  ceased  it  is  placed  on  the  water  bath  and  heated  until 
the  alloy  is  completely  decomposed  and  the  residue  is  pure  white.  All  of  the  phos- 
phoric acid  will  remain  with  the  tin  provided  a  sufficient  amount  of  the  latter  is 
present  in  the  alloy.  From  six  to  eight  times  as  much  tin  as  P205  must  be  present. 
Unless  at  least  5%  of  tin  has  been  found,  a  preliminary  test  should  be  made  by 
dissolving  about  a  gram  of  the  alloy  in  concentrated  nitric  acid,  filtering,  and  test- 
ing the  filtrate  for  phosphoric  acid  with  molybdate  mixture.  If  phosphoric  acid 
is  found  in  the  filtrate,  metallic  tin  must  be  added  before  dissolving  the  alloy  in 
nitric  acid.  From  ^  to  1  gram  will  usually  be  found  sufficient. 

The  nitric  acid  solution  of  the  alloy  is  diluted  and  the  stannic  oxide  containing 
the  phosphoric  acid  is  filtered  off  and  washed  a  few  times.  After  drying,  the  pre- 
cipitate is  transferred  to  a  porcelain  crucible,  the  paper  is  burned,  and  the  ash 
added.  After  adding  three  times  its  weight  of  potassium  cyanide,  cover  the  cru- 
cible and  fuse  for  a  few  minutes  at  a  red  heat.  The  stannic  oxide  is  reduced  to 
metallic  tin  and  the  phosphoric  acid  forms  potassium  phosphate.  After  cooling, 
extract  the  fused  mass  with  hot  water,  filter,  and  wash  the  paper  with  hot  water. 

Expel  the  hydrocyanic  and  cyanic  acids  by  boiling  with  concentrated  hydro- 
chloric acid.  This  operation  must  be  conducted  under  a  hood  with  good  draught. 
Evaporate  to  dryness  to  dehydrate  the  silicic  acid  which  has  been  dissolved  from 
the  porcelain  by  the  action  of  the  potassium  cyanide.  Dissolve  the  dry  residue 
in  a  little  hydrochloric  acid  and  pass  hydrogen  sulphide  to  precipitate  a  small 
amount  of  tin  and  copper  which  is  present.  Filter,  wash  the  precipitate,  and 
destroy  the  hydrogen  sulphide  in  the  filtrate  by  adding  bromine  water  and  boiling. 
If  the  volume  of  the  solution  exceeds  50  cc.,  concentrate  by  boiling.  Cool  and  pre- 
cipitate the  phosphoric  acid  by  adding  about  f  gram  of  crystallized  magnesium 
chloride  or  sulphate  dissolved  in  a  little  water  and  then  neutralizing  the  solution 
with  filtered  ammonia  while  stirring  vigorously.  Add  a  small  excess  of  ammonia. 
Assure  yourself  that  the  phosphoric  acid  is  all  precipitated  by  adding  a  little 
magnesia  mixture  to  the  clear  supernatant  liquid.  After  standing  several  hours, 
filter,  wash  with  dilute  ammonia,  ignite  in  a  porcelain  crucible,  and  weigh  as 
magnesium  pyrophosphate. 

The  precipitation  of  the  metals  present  with  hydrogen  sulphide  may  be  omitted 
and  the  separation  effected  by  precipitating  the  phosphoric  acid  as  molybdate. 
The  dry  residue  should  then  be  dissolved  in  nitric  acid,  and  after  filtering  off  the 
tiilica,  the  phosphoric  acid  is  precipitated  as  directed  in  the  chapter  on  Phosphorus. 

NOTE.  Strength  of  Adds  Used  in  Alloy  Analysis.  Concentrated  HC1,  sp.  gr.  1.19; 
concentrated  HNO3,  sp.  gr.  1.42;  concentrated  H2SO4,  sp.  gr.  1.84. 


METHODS  FOR  ANALYSIS  OF   GOAL 

FRANK  E.  HALE1 

Such  tremendous  value  attaches  in  boiler-room  economy  to  the  character 
of  the  fuel  that  the  purchase  of  coal  upon  the  results  of  laboratory  analysis 
has  grown  in  importance.  Specifications  have  been  drawn  with  such  exact 
requirements  that  fairness  to  the  coal  contractor  requires  that  only  exact  methods 
of  analysis  be  employed. 

SAMPLING 

In  order  that  the  laboratory  sample  shall  be  representative  of  the  delivery, 
great  care  must  be  taken,  however;  the  personal  element  should  be  eliminated 
as  far  as  possible.  When  possible,  coal  should  be  delivered  by  chutes  and  a 
shovelful  taken  at  regular  intervals  throughout  the  delivery.  If  delivered  in 
wagons  a  portion  should  be  taken  from  each  wagon  load.  Boat  loads  are  best 
sampled  while  being  loaded  or  unloaded.  If  a  pile  of  coal  must  be  sampled, 
portions  should  be  taken  from  all  sides,  top  and  bottom.  The  gross  sample  should 
preferably  be  200  pounds  for  deliveries  up  to  100  tons  and  one-tenth  of  1%  of  the 
amount  delivered  for  quantities  over  100  tons.  Larger  sizes  should  be  crushed 
to  at  least  pea  size  (about  f  in.)  and  preferably  under.  The  gross  sample 
should  be  thoroughly  mixed  with  a  shovel,  piled  up,  and  quartered.  Opposite 
quarters  should  then  be  mixed,  piled  up,  and  quartered  again  and  this  con- 
tinued until  a  sample  of  about  5  pounds  is  obtained.2  This  sample  should  then 
be  forwarded  to  the  laboratory  in  a  sealed  moisture-tight  container.  The  most 
satisfactory  container  is  one  made  of  galvanized  iron,  to  prevent  rusting,  cylin- 
drical in  shape  with  screw  cap  flush  with  the  sides.  A  convenient  size  is  6  ins. 
in  diameter  by  8  ins.  height.  Such  a  can  is  readily  cleaned  and  sealed.  Sealing 
is  conveniently  made  by  pasting  a  strip  of  paper  around  the  can  over  the  joint, 
or  by  means  of  wax  and  an  impression  seal. 

PREPARATION   OF  SAMPLE   FOR  ANALYSIS 

The  laboratory  sample  should  first  receive  a  number  which  should  follow 
the  sample  through  all  phases  of  preparation  in  order  to  avoid  confusion.  The 
whole  sample,  when  received  at  the  laboratory,  should  be  crushed  to  4-mesh 
size  or  less.  The  Chipmunk  Jaw  Crusher  is  rapid  and  easily  cleaned,  as  one 
jaw  is  removable.  If  too  wet  to  crush,  causing  clogging  of  the  crusher,  the 
whole  sample  should  be  dried  on  the  steam  bath,  the  moisture  so  lost  determined 
and  added  to  the  analytical  moisture  later  determined  on  the  pulverized  sample. 
Shallow  agateware  pans  large  enough  to  take  the  complete  sample  are  con- 
venient and  should  set  in  large  holes  on  the  steam  bath,  so  that  the  body  of 

1  Director  of  Laboratories,  Dept.  Water  Supply,  Gas  and  Electricity,  New  York  City. 
*  The  U.  S.  Bureau  of  Mines  uses  a  3-pound  sample  and  New  York  City  a  7-pound 
sample. 

672 


METHODS  FOR  ANALYSIS  OF  COAL 


673 


the  pan  is  exposed  to  the  steam  and  drying  is  hastened.  A  few  hours  only  is 
necessary.  The  U.  S.  Bureau  of  Mines  dries  in  a  special  oven  with  a  current 
of  dried  air  at  30-35°  C.,  but  this  occasions  a  delay  of  twelve  to  ninety-six  hours. 
The  crushed  sample  should  be  mixed  and  quartered,  preferably  by  hand. 
This  is  best  and  most  rapidly  done  in  the  old-fashioned  way  by  raising  alternately 
the  corners  of  a  large  piece  of  oilcloth  or  rubber  sheet.  The  pile  may  be  quickly 
quartered  by  two  V-shaped  pieces  of  galvanized  iron  to  cut  and  pull  away 
opposite  quarters.  The  remaining  quarters  should  be  again  mixed  and  quar- 
tered in  the  same  way  and  the  process  continued  until  a  100-gram  representative 


FIG.   103. — Illustrates  Method  of  Quartering  Coal,   Ball  Mill  for  Pulverizing,  and 

Suction  Ventilator. 


portion  is  obtained.  The  discarded  quarters  should  be  returned  to  the  can  to 
be  retained  in  case  a  second  analysis  is  desired.  Such  check  analysis  should 
always  be  made  upon  a  freshly  quartered  and  pulverized  sample  of  the  remain- 
ing portions  of  the  original  gross  laboratory  sample. 

The  100-gram  sample  should  then  be  pulverized  in  an  Abbe"  Ball  Mill  for 
three-quarters  of  an  hour.  The  jar  should  be  nearly  full  to  produce  the  most 
rapid  pulverization,  that  is,  contain  the  full  charge  of  pebbles,  about  10  pounds 
for  the  9-in.  jar.  The  speed  of  revolution  should  be  60  per  minute.  Natural 
flint  pebbles  are  least  abraded  and  produce  no  appreciable  effect  upon  the 
ash.  The  ball  mill  has  two  distinct  advantages.  It  conserves  the  moisture 


674      METHODS  FOR  ANALYSIS  OF  COAL 

of  the  coal  and  it  pulverizes  so  fine  that  the  coal  will  usually  all  pass  a  60-mesh 
screen  and  a  large  part  the  100-mesh  screen.  This  greater  fineness  prevents 
incomplete  combustion  of  anthracite  coal  in  the  bomb  determination  to  be 
described  later.  The  pebbles  and  coal  should  then  be  dumped  on  a  covered 
ash-sifter  resting  on  the  oilcloth  or  rubber  sheet,  shaken  quickly  and  pebbles 
and  sifter  brushed  clean.  The  sample  should  then  be  passed  through  the 
60-mesh  screen  and  brushed  at  once  into  a  moisture-tight  container.  Any 
material  retained  on  the  60-mesh  screen,  which  occasionally  happens,  should  be 
quickly  pulverized  in  a  small  steel  mortar.  One-half  pint,  glass-covered  lightning 
jars  are  convenient  for  this  purpose. 

As  the  dust  in  coal  sampling  is  so  fine  as  to  penetrate  through  the  clothing 
to  the  skin,  it  is  wise  to  use  an  aspirator  to  protect  the  lungs  and  also  use  a 
suction  ventilator  to  keep  the  air  fresh  and  clean.  The  suction  should  connect 
with  small  hoods  over  the  crusher  and  over  the  quartering  table. 

METHODS  OF  ANALYSIS 

Moisture.  Moisture  may  be  accurately  determined  on  a  10-gram  sample 
heated  for  one  hour  at  105°  C.  Close  checks  will  be  obtained  and  weighing  i? 
rapid,  as  the  weight  need  only  be  taken  to  the  nearest  milligram.  Glass  evap^ 
orating  dishes  of  2f-in.  diameter  are  convenient  for  this  determination.  The 
Beans  electric  thermo-regulator  for  gas  has  been  found  very  satisfactory  for 
oven  regulation,  as  the  oven  may  be  heated  rapidly  and  will  quickly  come  to 
adjustment. 

Most  laboratories  employ  a  1-gram  sample,  however,  and  later  use  the  residue 
for  ash  determination.  The  Bureau  of  Mines  uses  a  special  drying  oven  and  a 
specially  prepared  sample  for  moisture.  The  4-mesh  sample  is  crushed  in  a 
roll  or  coffee-mill  crusher  to  20-mesh,  and  bottled  quickly  without  sieving. 

Ash.  The  ash  represents  the  mineral  matter  in  coal  after  ignition.  No 
attempt  is  made  in  common  practice  to  calculate  the  original  form  of  the  con- 
stituents. It  is  best  determined  upon  a  separate  portion  of  coal,  and  pref- 
erably in  silica  crucibles,  as  the  wear  on  platinum  is  considerable.  Heating 
should  be  slow  and  careful  at  first,  to  avoid  loss  from  volatile  matter  and  to 
avoid  the  effect  of  coking.  Later  the  contents  should  be  stirred  with  a  plati- 
num wire  to  facilitate  combustion,  not  neglecting  to  tap  the  wire  free  from 
ash.  The  silica  crucibles  should  rest  on  silica  or  nichrome  triangles.  Some 
laboratories  employ  a  muffle  furnace  and  others  an  electric  furnace. 

The  residue  from  moisture  may  be  used  for  ash  determination,  but  the 
residue  from  volatile  combustible  matter  should  not  be  so  used,  as  there  is  danger 
of  mechanical  loss  of  ash  in  the  rapid  heating,  and  the  accuracy  of  the  ash- 
figure  is  far  more  important  than  the  volatile  combustible  matter. 

A  1-gram  sample  is  used  for  the  ash  determination. 

Volatile  Combustible  Matter.  This  determination  is  entirely  empirical 
and  should  be  performed  under  strictly  standard  conditions.  The  determina- 
tion is  made  upon  a  1-gram  sample  heated  for  seven  minutes,  timed  by  a  stop- 
watch, in  a  platinum  crucible  of  25-30  cc.  capacity,  and  with  tight-fitting  cover. 
The  crucible  and  cover  should  be  kept  brightly  polished.  A  special  apparatus 
should  be  arranged.  Construct  a  cylinder  of  asbestos  or  galvanized  iron  to 
protect  flame  and  crucible.  Connect  an  adjustable  Me"ker  burner  (Scimatco 
type  is  preferable)  with  a  U-tube  to  measure  gas  pressure.  Arrange  a  platinum 


METHODS  FOR  ANALYSIS  OF  COAL 


675 


wire  from  triangle  to  support  the  bottom  of  crucible  always  at  same  distance 
from  the  burner. 

Calibrate  the  apparatus  by  adjusting  the  burner  and  pressure  so  that  the 
crucible  is  entirely  surrounded  by  the  flame  and  the  temperature  is  about  950° 
C.  This  may  be  determined  by  an  optical  or  other  pyrometer,  but  most  con- 
veniently by  the  fusing-point  of  potassium  chromate.  Note  the  gas  pressure 
required  and  in  the  analyses  set  the  gas  at  this  pressure.  In  this  way  close 
checks  may  conveniently  be  obtained  when  the  right  conditions  have  been 
determined. 

The  loss  in  weight  minus  the  moisture  is  the  volatile  combustible  matter. 

A  10-20-cc.  crucible  has  recently  been  advocated  to  reduce  the  effect  of 
oxidation  by  oxygen  in  the  crucible.  Several  different  schemes  have  been 
advocated  in  order  to  obtain  uniform  results.  An  electric  furnace  is  used  by 
some.  Any  method  is  empirical,  as  the  determination  does  not  represent  any 


FIG.  104.— V.  C.  M.  Apparatus 


very  definite  constituent  of  the  coal.  Originally  intended  as  a  measure  of 
coking  ability  the  V.C.M  is  now  mainly  a  means  of  discriminating  between 
different  kinds  of  coal  and  as  a  means  of  keeping  within  the  smoke  ordinances. 

Volatile  Sulphur.  The  total  sulphur  in  a  coal  is  of  little  importance.  If 
desired,  it  may  be  determined  by  the  well-known  Eschka  method.  The  vol- 
atile sulphur  is  of  great  importance  both  in  its  bearing  upon  fusibility  by  indi- 
cating the  presence  of  pyrites  in  the  coal  and  in  its  relation  to  corrosion  by  the 
formation  of  sulphurous  acid. 

Volatile  sulphur  is  determined  in  the  bomb  washings  after  a  calorific  deter- 
mination. These  washings  are  filtered  if  necessary  and  titrated  for  acidity 
for  one  of  the  corrections  in  the  calorific  calculation.  The  sulphur  is  then  deter- 
mined most  rapidly  and  conveniently  by  a  Jackson  Candle  Turbidimeter. 

"The  titrated  solution  is  made  up  to  200  cc.  The  amount  of  acidity  found 
is  used  as  a  guide  in  selecting  the  aliquot  for  the  sulphur  determination.  In 


676 


METHODS  FOR  ANALYSIS  OF  COAL 


TURBIDIMETRIC    SULPHUR    TABLE 

For  use  with  Jackson's  candle  turbidimetei 
Sulphur  and  SO3  contained  in  100  cc.  precipitated 


Depth. 
Cm. 

s. 

Mg. 

SO3. 

Mg. 

Depth. 
Cm. 

s. 

Mg. 

SOs. 
Mg. 

Depth. 
Cm. 

S. 
Mg. 

S03. 
Mg. 

1.0 

20.0 

50.0 

5.0 

3.66 

9.15 

9.0 

2.30 

5.75 

1.1 

18.0 

45.0 

5.1 

3.60 

9.00 

9.1 

2.28 

5.70 

1.2 

16.5 

41.3 

5.2 

3.54 

8.85 

9.2 

2.26 

5.65 

1.3 

15.0 

37.5 

5.3 

3.49 

8.73 

9.3 

2.25 

5.63 

1.4 

13.5 

33.8 

5.4 

3.43 

8.58 

9.4 

2.23 

5.58 

1.5 

12.5 

31.3 

5.5 

3.38 

8.45 

9.5 

2.21 

5.53 

1.6 

11.2 

28.0 

5.6 

3.33 

8.33 

9.6 

2.19 

5.48 

1.7 

10.0 

25.0 

5.7 

3.28 

8.20 

9.7 

2.18 

5.45 

1.8 

9.5 

23.8 

5.8 

3.24 

8.10 

9.8 

2.16 

5.40 

1.9 

9.0 

22.5 

5.9 

3.20 

8.00 

9.9 

2.15 

5.38 

2.0 

8.5 

21.3 

6.0 

3.15 

7.88 

10.0 

2.13 

5.33 

2.1 

8.0 

20.0 

6.1 

3.11 

7.78 

10.1 

2.11 

5.28 

2.2 

7.6 

19.0 

6.2 

3.07 

7.68 

10.2 

2.10 

5.25 

2.3 

7.3 

18.3 

6.3 

3.03 

7.58 

10.3 

2.09 

5.23 

2.4 

7.0 

17.5 

6.4 

2.99 

7.48 

10.4 

2.07 

5.18 

2.5 

6.7 

16.8 

6.5 

2.95 

7.38 

10.5 

2.06 

5.15 

2.6 

6.5 

16.3 

6.6 

2.92 

7.30 

10.6 

2.04 

5.10 

2.7 

6.3 

15.8 

6.7 

2.88 

7.20 

10.7 

2.03 

5.08 

2.8 

6.1 

15.3 

6.8 

2.85 

7.13 

10.8 

2.02 

5.05 

2.9 

5.9 

14.8 

6.9 

2.82 

7.05 

10.9 

2.01 

5.03 

3.0 

5.7 

14.3 

7.0 

2.79 

6.98 

11.0 

2.00 

5.00 

3.1 

5.5 

13.8 

7.1 

2.76 

6.90 

11.1 

1.98 

4.95 

3.2 

5.4 

13.5 

7.2 

2.73 

6.83 

11.2 

1.97 

4.93 

3.3 

5.2 

13.0 

7.3 

2.70 

6.75 

11.3 

1.95 

4.88 

3.4 

5.1 

12.8 

7.4 

2.67 

6.68 

11.4 

1.94 

4.85 

3.5 

5.0 

12.5 

7.5 

2.64 

6.60 

11.5 

1.93 

4.83 

3.6 

4.85 

12.25 

7.6 

2.61 

6.53 

11.6 

1.92 

4.80 

3.7 

4.75 

12.  CO 

7.7 

2.59 

6.48 

11.7 

1.91 

4.78 

3.8 

4.63 

11.75 

7.8 

2.56 

6.40 

11.8 

.90 

4.75 

3.9 

4.52 

11.50 

7.9 

2.54 

6.35 

11.9 

.89 

4.73 

4.0 

4.43 

11.25 

8.0 

2.51 

6.28 

12.0 

.88 

4.70 

4.1 

4.33 

11.00 

8.1 

2.49 

6.23 

12.1 

.87 

4.68 

4.2 

4.24 

10.75 

8.2 

2.47 

6.18 

12.2 

.86 

4.65 

4.3 

4.16 

10.50 

8.3 

2.44 

6.10 

12.3 

.85 

4.63 

4.4 

4.08 

10.25 

8.4 

2.42 

6.05 

12.4 

.84 

4.60 

4.5 

4.00 

10.00 

8.5 

2.40 

6.00 

12.5 

.83 

4.58 

4.6 

3.93 

9.83 

8.6 

2.38 

5.95 

12.6 

.82 

4.55 

4.7 

3.86 

9.65 

8.7 

2.36 

5.90 

12.7 

.81 

4.53 

4.8 

3.79 

9.48 

8.8 

2.34 

5.85 

12.8 

.80 

4.50 

4.9 

3.72 

9.30 

8.9 

2.32 

5.80 

12.9 

.79 

•1      IS 

METHODS  FOR  ANALYSIS  OF  COAL 

TURBIDIMETRIC  SULPHUR  TABLE. — Continued 


677 


Depth. 
Cm. 

s. 

Mg. 

SOs. 
Mg. 

Depth. 
Cm. 

S. 
Mg. 

SOs. 
Mg. 

Depth. 
Cm. 

s. 

Mg. 

SOs. 
Mg. 

13.0 

1.78 

4.45 

17.1 

1.49 

3.73 

21.1 

1.24 

3.10 

13.1 

1.77 

4.43 

17.2 

1.49 

3.73 

21.2 

1.23 

3.08 

13.2 

1.76 

4.40 

17.3 

1.48 

3.70 

21.3 

1.23 

3.08 

13.3 

1.75 

4.38 

17  A 

1.47 

3.68 

21.4 

1.22 

3.05 

13.4 

1.74 

4.35 

17.5 

1.47 

3.68 

21.5 

1.21 

3.03 

13.5 

1.73 

4.33 

17.6 

1.46 

3.65 

21.6 

1.21 

3.03 

13.6 

1.73 

4.33 

17.7 

1.45 

3.63 

21.7 

1.20 

3.00 

13.7 

1.72 

4.30 

17.8 

1.44 

3.60 

21.8 

1.20 

3.00 

13.8 

1.71 

4.28 

17.9 

1.44 

3.60 

21.9 

1.19 

2.98 

13.9 

1.70 

4.25 

18.0 

1.43 

3.58 

22.0 

1.18 

2.95 

14.0 

1.70 

4.25 

18.1 

1.43 

3.58 

22.1 

1.18 

2.95 

14.1 

1.69 

4.23 

18.2 

1.42 

3.55 

22.2 

1.17 

2.93 

14.2 

1.68 

4.20 

18.3 

1.41 

3.53 

22.3 

1.16 

2.90 

14.3 

1.67 

4.18 

18.4 

1.41 

3.53 

22.4 

1.16 

2.90 

14.4 

1.66 

4.15 

18.5 

1.40 

3.50 

22.5 

1.15 

2.88 

14.5 

1.66 

4.15 

18.6 

1.40 

3.50 

22.6 

1.15 

2.88 

14.6 

1.65 

4.13 

18.7 

1.39 

3.48 

22.7 

1.14 

2.85 

14.7 

1.64 

4.10 

18.8 

1.38 

3.45 

22.8 

1.13 

2.83 

14.8 

1.63 

4.08 

18.9 

1.38 

3.45 

22.9 

1.13 

2.83 

14.9 

1.62 

4.05 

19.0 

1.37 

3.43 

23.0 

1.12 

2.80 

15.0 

1.62 

4.05 

19.1 

1.37 

3.43 

23.1 

1.11 

2.78 

15.1 

1.61 

4.03 

19.2 

1.36 

3.40 

23.2 

1.11 

2.78 

15.2 

1.60 

4.00 

19.3 

1.35 

3.38 

23.3 

1.10 

2.75 

15.3 

1.60 

4.00 

19.4 

1.35 

3.38 

23.4 

1.09 

2.73 

15.4 

1.59 

3.98 

19.5 

1.34 

3.35 

23.5 

1.08 

2.70 

15.5 

1.59 

3.98 

19.6 

1.34 

3.35 

23.6 

1.08 

2.70 

15.6 

1.58 

3.95 

19.7 

1.33 

3.33 

23.7 

1.07 

2.68 

15.7 

1.57 

3.93 

19.8 

1.32 

3.30 

23.8 

1.06 

2.65 

15.8 

1.57 

3.93 

19.9 

1.32 

3.30 

23.9 

1.05 

2.63 

15.9 

1.56 

3.90 

20.0 

1.31 

3.28 

24.0 

1.05 

2.63 

16.0 

1.56 

3.90 

20.1 

1.30 

3.25 

24.1 

1.04 

2.60 

16.1 

1.55 

3.88 

20.2 

1.30 

3.25 

24.2 

1.03 

2.58 

16.2 

1.54 

3.85 

20.3 

1.29 

3.23 

24.3 

1.03 

2.58 

16.3 

1.54 

3.85 

20.4 

1.28 

3.20 

24.4 

1.02 

2.55 

16.4 

1.53 

3.83 

20.5 

1.28 

3.20 

24.5 

1.02 

2.55 

16.5 

1.53 

3.83 

20.6 

1.27 

3.18 

24.6 

1.01 

2.53 

16.6 

1.52 

3.80 

20.7 

1.26 

3.15 

24.7 

1.01 

2.53 

16.7 

1.52 

3.80 

20.8 

1.26 

3.15 

24.8 

1.00 

2.50 

16.8 

1.51 

3.78 

20.9 

1.25 

3.13 

24.9 

1.00 

2.50 

16.9 

1.50 

3.75 

21.0 

1.25 

3.13 

25.0 

1.00 

2.50 

17.0 

1.50 

3.75 

678      METHODS  FOR  ANALYSIS  OF  COAL 

the  case  of  anthracite  coals,  the  amount  taken  is  one-fourth  to  one-half;  in 
the  case  of  soft  coals  from  one-fourth  to  one-tenth  of  the  whole." 

"The  aliquot  of  the  solution  to  be  tested  is  measured  into  the  turbidimeter 
tube,  diluted  to  near  the  100-cc.  mark,  shaken,  then  acidified  with  1  cc.  of  1  :  1 
hydrochloric  acid,  made  up  to  the  mark,  and  mixed  well  by  shaking.  A  barium 
chloride  tablet x  weighing  1  gram  and  compressed  without  the  use  of  a  binder 
is  then  dropped  in  and  the  tube  closed  by  means  of  a  clean  rubber  stopper. 
The  tube  is  then  tilted  up  and  down,  causing  the  tablet  to  roll  back  and  forth 
through  the  solution  by  gravity. 

When  the  precipitation  appears  to  be  complete,  the  remainder  of  the  tablet 
may  be  dissolved  by  rapidly  rotating  the  tube;  but  violent  shaking  should 
be  avoided,  since  it  would  have  a  tendency  to  cause  aggregation  of  the  pre- 
cipitate. The  turbid  liquid  is  then  transferred  to  a  beaker,  the  candle  lighted, 
a  small  quantity  of  the  liquid  poured  into  the  glass  tube  to  prevent  overheating 
and  cracking,  and  the  tube  put  in  place.  More  of  the  liquid  is  then  poured 
in,  allowing  it  to  run  down  the  side  of  the  tube,  rapidly  at  first,  until  the  image 
of  the  flame  becomes  dim,  then  more  slowly,  waiting  a  moment  after  each 
addition  until  the  liquid  in  the  tube  is  quiet,  and  continuing  thus  until  the 
image  of  the  flame  just  disappears.  The^jlepth  of  the  liquid  in  centimeters 
is  noted.  The  mixture  is  then  returned  to  the  beaker,  poured  back  and  forth 
from  beaker  to  tube  two  or  three  times,  and  read  again  as  before. 

"The  precipitated  solution  is  read  at  least  twice,  and  the  readings  usualty 
check  exactly,  unless  they  fall  in  the  upper  part  of  the  tube,  where  they  may 
differ  by  a  centimeter  without  materially  altering  the  results.  In  this  case 
readings  may  be  averaged.  The  amount  of  sulphur  corresponding  to  the  depth 
of  liquid  in  the  tube  is  found  in  the  table,  and  multiplied  by  the  proper 
factor,  depending  on  the  aliquot  of  the  original  solution  taken. 

"All  dilutions  must  be  made  before  precipitation,  for  otherwise  the  results 
will  not  be  concordant  for  different  dilutions."  The  average  time  required  is 
ten  minutes  or  less.  The  method  carried  out  as  described  is  accurate  to  about 
0.05%  sulphur. 

Fixed  Carbon.  Fixed  carbon  is  found  by  adding  the  moisture,  ash,  and 
volatile  matter  together,  and  subtracting  from  100%. 

Calorific  Value.  Heat  value  is  expressed  as  "small  calorie  (cal.),"  the 
amount  of  heat  required  to  raise  the  temperature  of  1  gram  of  water  1°  C., 
"large  calorie  (Cal.),"  the  amount  of  heat  required  to  raise  the  temperature 
of  1  kilogram  of  water  1°  C.,  and  "  British  thermal  unit  (B.t.u.)/'  the  amount 
of  heat  required  to  raise  the  temperature  of  1  pound  of  water  1°  F.,  at  or  near 
39.1°  F.  Small  calories  per  gram  of  coal  multiplied  by  1.8  equal  B.t.u.  per 
pound  of  coal. 

It  is  preferable  to  express  results  as  B.t.u.  per  pound  of  dry  coal,  instead 
of  coal  as  received,  since  comparison  between  different  samples  of  coal  and 
the  results  of  different  analysts  and  laboratories  are  facilitated.  The  other 
determinations  except  moisture  are  also  better  expressed  on  the  dry  basis. 

1  These  tablets  are  prepared  on  order  by  the  Fraser  Tablet  Co.,  of  Brooklyn. 
N.  Y.,  Formula  No.  188,663. 

On  standing  for  some  time,  some  of  the  tablets  become  coated  with  a  thin  layer 
of  effloresced  salt.  This  should  be  removed  by  gently  rubbing  between  the  fingers 
before  using  the  tablet.  It  is  not  advisable  to  keep  the  tablets  in  a  moist  atmosphere 
to  prevent  this  efflorescence,  as  they  become  extremely  hard  and  difficult  to  dissolve. 


METHODS  FOR  ANALYSIS  OF  COAL 


679 


As  a  check  upon  accuracy  of  work  and  to  catch  errors,  results  of  B.t.u. 
should  also  be  calculated  to  B.t.u.  per  pound  of  combustible,  that  is,  divide  the 
B.t.u.  dry  basis  by  (100%  minus  the  per  cent  of  ash).  For  the  same  run  of 
coal,  this  value  changes  but  little,  usually  within  200  B.t.u. 

The  calorific  determination  should  be  made  by  means  of  a  bomb  calorimeter. 
The  platinum-lined  Atwater  type  is  very  convenient  and  requires  but  little  repair. 

One  gram  of  the  60-mesh  sample  of  coal  prepared  for  analysis  is  weighed 
into  a  nickel  capsule  (28  mm.  top  width,  23  mm.  bottom  width,  and  12  mm. 


FIG.  105. — Atwater  Bomb  and  Calorimeter  with  Accessories,  in  Special  Room. 

depth)  in  the  bottom  of  which  has  been  placed  an  ignited  disc  of  asbestos  paper. 
The  latter  prevents  incomplete  combustion  of  anthracite  coal  by  preventing 
chilling  of  the  coal  after  combustion  starts.  In  weighing  large  numbers  of 
samples  a  piece  of  tared  platinum  foil  is  convenient  and  the  coal  transferred 
with  a  camel's-hair  brush  into  the  nickel  capsule.  The  capsule  is  supported  on 
a  platinum  ring  suspended  by  a  platinum  wire  from  the  head  of  the  bomb. 
A  piece  of  iron  fuse  wire,  No.  34  B.  &  S.  gauge,  and  weighing  10  milligrams, 
is  attached  at  one  end  to  the  wire  supporting  the  tray  and  at  the  other  end  to 
another  platinum  wire  extending  downward  from  the  head,  but  insulated  from 
it.  Attachment  of  the  fuse  wire  is  made  by  winding  around  the  platinum 
wires  several  times.  The  center  of  the  fuse  wire  should  dip  into  the  coal 
slightly.  A  convenient  method  of  obtaining  pieces  of  fuse  wire  of  uniform 
weight  is  to  wind  around  a  flat  piece  of  board  or  cardboard  and  cut  the  loops. 


680 


METHODS  FOR  ANALYSIS  OF  COAL 


The  shell  of  the  bomb  is  rinsed  with  water  and  sufficient  moisture,  one-half 
cc.,  is  thus  left  to  take  up  the  acids  formed  by  combustion.  The  head  is  next 
joined  gas  tight  to  the  shell  of  the  bomb  by  the  collar.  Lead  gaskets  render 
these  joints  tight.  Oxygen  gas  is  slowly  introduced,  so  as  not  to  blow  the 
coal  out  of  the  pan,  until  about  21  atmospheres  pressure  is  recorded  in  the 
bomb.  The  needle  valve  is  then  closed  just  tight  enough  to  prevent  leakage, 
the  valve  on  oxygen  tank  closed  and  the  bomb  disconnected.  Twenty  atmos- 
pheres pressure  should  remain  in  the  bomb  for  the  combustion,  an  amount 


FIG.  106. — Illustrates  Method  of  Connecting  Two  Oxygen  Cylinders  for  Filling  Bomb 
when  Pressure  in  One  is  below  Twenty  Atmospheres. 


sufficient  for  complete  combustion  of  the  coal  and  an  amount  containing  suf- 
ficient nitrogen  together  with  the  nitrogen  in  the  air  trapped  in  the  bomb  to 
cause  the  sulphur  to  burn  to  sulphuric  acid  completely,  unless  the  sulphur  is 
unusually  high. 

The  bucket  is  filled  with  enough  distilled  water,  about  3°  C.  below  the  room 
temperature,  to  make  the  water  equivalent  of  the  calorimeter  some  round 
number,  for  example,  2000  grams  with  the  Atwater,  2900  grams  with  the  Mahler. 
The  water  is  best  weighed  on  a  balance,  capable  of  delicacy  with  such  heavy 
weights,  and  the  amount  of  water  should  be  sufficient  to  cover  the  bomb.  The 
bomb  is  placed  in  its  support  and  placed  in  the  water  in  the  bucket.  The  latter 
is  set  in  the  calorimeter,  the  stirrer  added  so  as  not  to  touch  bomb  or  bucket, 


METHODS  FOR  ANALYSIS  OF  COAL      681 

covers  applied  and  thermometer  placed  in  the  water  and  adjusted  so  that  it 
can  be  read  during  the  combustion.  The  thermometers  should  be  special  and 
standardized  by  the  Bureau  of  Standards.  The  Fuess  type  of  Beckmann  is 
excellent. 

Connect  the  poles  of  six  dry  cells  to  the  stem  and  insulated  post  of  the  bomb. 
Connection  should  be  made  with  a  button  for  firing  the  coal.  It  is  also  con- 
venient to  have  a  small  electric  lamp  connected  with  the  button  to  indicate 
that  the  batteries  are  in  condition,  before  a  run  is  started. 

The  calorific  determination  should  be  made  in  a  room  protected  from 
sudden  changes  of  temperature  and  from  draughts.  If  a  current  of  air  strikes 
the  thermometer  during  a  determination,  the  results  will  be  untrustworthy. 
Mechanical  stirring  is  preferable  and  should  be  at  a  moderate  rate.  The  stirrer 
is  started  and  after  a  couple  of  minutes  or  so,  when  conditions  have  become 
uniform,  the  thermometer  is  read  by  means  of  a  telescope  and  readings  taken 
every  one-half  minute  for  six  readings.  Interpolate  to  the  0.001°  C.  A  clock 
striking  every  half  minute  is  convenient.  After  the  sixth  reading,  fire  the  coal 
by  pressing  the  button  connected  with  the  batteries  and  take  approximate 
readings  of  the  thermometer  every  half  minute,  reading  to  the  0.001°  C.  as  soon 
as  the  rise  is  slow  enough  to  do  so.  After  the  maximum  temperature  has  been 
reached,  take  six  more  readings  at  half-minute  intervals. 

Remove  the  bomb  from  the  bucket  and  allow  the  gas  to  escape  slowly.  Dis- 
connect the  head  and  rinse  out  the  bomb  thoroughly.  Titrate  the  washings 
with  N/10  sodium  carbonate,  using  methyl  orange  as  indicator.  Determine  the 
sulphur,  after  titration,  with  the  turbidimeter  as  under  Volatile  Sulphur. 

Calculation  of  B.T.U.  The  table  on  page  682  is  an  example  of  an  actual 
determination,  showing  corrections  as  applied. 

Corrections  must  be  applied  to  the  thermometer  in  accordance  with  the 
certificate  furnished  for  each  thermometer  by  the  Bureau  of  Standards,  includ- 
ing the  correction  for  temperature  of  setting  of  Beckmann  thermometers  and 
emergent  stem  correction  for  others. 

The  thermometer  should  also  be  fitted  with  a  vibrator  to  overcome  meniscus 
error.  This  is  conveniently  done  by  arranging  a  small  electric  vibrator  so 
that  the  hammer  hits  the  rubber-covered  metal  clamp  supporting  the  ther- 
mometer. The  vibrator  should,  of  course,  be  connected  to  a  push-button  and 
dry  batteries. 

Correction  must  also  be  made  for  changes  of  temperature  due  to  radiation. 
A  simple  formula  which  yields  results  within  0.002°  C.  as  compared  with  the 
more  elaborate  f ormula?  is  the  following : 

x(a+6)       .  .  . 

— \-yf)  =  radiation  correction. 

a  =  average  preliminary  period  change  per  half  minute; 

b  =  average  final  period  change  per  half  minute; 

x-  number  of  half-minute  intervals  of  combustion  period  during  which  the  rise 

of  temperature  (expressed  to  the  nearest  0.01°)  was  greater  than  10%  of 

the  total  rise.    This  is  readily  seen  by  inspection; 
y  =  remaining  number  of  half -minute  intervals  of  combustion  period. 

The  algebraic  signs  must  be  observed  in  the  formula. 


682 


METHODS  FOR  ANALYSIS  OF  COAL 


The  end  of  the  combustion  period  is  taken  as  the  first  reading  after  the 
maximum  temperature.  The  reason  for  this  rests  in  the  fact  that  the  real 
maximum  rarely  occurs  at  a  half-minute  interval  reading,  as  shown  by  a  drop, 
during  the  first  period  after  the  maximum  temperature  read,  of  less  than  the 


NO.   1   BUCKWHEAT  COAL 

Thermometer  used  (T6),  zero  set  at  20.4°  C. 

Room  Temperature  22.5°  C.     Atwater  bomb. 

Acid  found  equal  7.2  cc.  N/10  Na-jCO3  X  1.45  cal.  =  10.4  calories 

Volatile  sulphur  (aliquot  |)  8.6  cm.  =  .0048  gram  X 13  cal.  =  6.2  calories 
Iron  wire  (10  milligrams)  =16.0  calories 


Thermometer  readings, 
Half  minute  intervals 


0.979 
0.-980 
0.981 
0.983 
0.984 
.  0.986 
Average  rise  in  temperature ; 

=  .0014 


Prelimi- 
nary 
period 


Combus- 
tion 
period 


1.600 
3.270 
4.050 


225 

267 
278 
279 


4.278 


4.273 
4.270 
4.268 
4.264 
,  4.260 
Average  fall  in  temperature : 

^  =  .0036 


Final 
period 


32.6  calories 
Corrected  temperature,  end  of  combustion 

period 4. 277 

Corrected  temperature,  end  of  prelimi- 
nary period 0 . 986 


Apparent  rise  in  temperature  corrected  for 
thermometer  calibration 

Thermometer  correction  for  setting  and 
room  temperature 

Apparent  rise  in  temperature,  corrected 
for  thermometer  setting 

Radiation  correction : 

/(-.0014)  +  (  +  .0036)\ 
3  I £ )  +5(  +  .OOdo) 


3.291 
+0.022 

3.313 
+0.021 


Corrected  rise  in  temperature 3 . 334 

Water  equivalent  (grams) 2000 

Calories  (2000X3.334) 6668.0 

Correction  for  acidity,  sulphur   trioxide 
andiron 32.6 

Actual  calories,  coal  as  received 6635 . 4 

Calories  (dry  basis)  6635.4 -r- .9522  (100% 

—moisture) 6968 . 5 

B.t.u.     per    Ib.    of     coal     (dry    basis) 

(6968.5X1.8) 12,543 

B.t.u.  per  Ib.  of  combusfible  (dry  basis) 

12543  -T-  .842(100%  -ash) 14,897 


B.T.U 12,543 

V.C.M 7.7  % 

Ash 15.8 

Vol.  sulphur 0.48 

Moisture..  4.78 


average  final  change.     Correcting  for  an  extra  combustion  interval  counteracts 
this  error. 

The  nitrogen  in  the  coal  and  in  the  air  of  the  bomb  forms  nitric  acid.  This 
does  not  occur  when  coal  is  burned  in  the  furnace,  hence  the  bomb  determi- 
nation is  too  high  by  the  amount  of  heat  thus  produced.  The  calorific  value  of 
nitrogen  burning  to  nitric  acid  is  230  calories  per  gram  of  nitric  acid.  Each 


METHODS  FOR  ANALYSIS  OF  COAL       683 

cubic  centimeter  of  N/10  sodium  carbonate  used  in  the  titration  represents 
1.45  calories. 

Furthermore,  sulphur  in  the  furnace  burns  to  the  dioxide  and  in  the  bomb 
to  the  trioxide.  This  excess  heat  in  the  bomb  must  be  corrected  for  as  well 
as  the  fact  that  all  of  the  above  acidity  is  not  nitric,  but  is  partly  sulphuric 
acid.  This  correction  is  conveniently  made  by  adding  to  the  acidity  correction 
(made  as  if  it  were  all  nitric  acid)  13  calories  for  each  0.01  gram  of  sulphur. 
This  represents  the  excess  which  the  oxidation  correction  is  over  its  expression 
as  the  formation  of  nitric  acid  as  obtained  from  the  titration. 

The  correction  for  the  iron  fuse  wire  is  16  calories  for  each  10  milligrams. 

All  other  corrections  are  met  by  standardization  under  conditions  similar 
to  those  under  which  the  calorimeter  is  to  be  used.  Such  errors  arise  from  loss 
of  heat  by  evaporation  of  water  while  stirring  (probably  covered  by  the  radia- 
tion correction),  gain  in  heat  due  to  combustible  gases  in  the  oxygen,  changes 
in  specific  heat  of  water  at  various  temperatures,  changes  in  the  gases  present 
after  combustion,  and  changes  of  pressure  of  the  gases  in  the  bomb.  The  last 
three  errors  are  too  small  to  take  into  account.  The  oxygen  error  has  dis- 
appeared since  the  introduction  of  the  purer  gas  manufactured  by  the  Linde 
Air  Products  Company. 

Inspection  of  the  bomb  contents  should  always  be  made  to  insure  that 
there  are  no  sooty  deposits  or  coal  thrown  from  the  capsule.  Some  coals 
require  to  be  compressed  into  pellets  to  prevent  the  above. 

The  procedure  outlined  above,  using  half-minute  intervals,  saves  considerable 
time  (nearly  one-half)  over  the  usual  procedure  and  produces  very  accurate  results. 

Standardization  of  the  Calorimeter.  While  there  are  several  ways  of 
determining  the  water  equivalent  of  the  calorimeter,  that  is,  the  heat  capacity 
of  the  apparatus  expressed  as  though  it  were  all  water,  only  one  method  should 
be  used  by  commercial  laboratories,  and  that  is  to  burn  in  the  calorimeter  a 
known  weight  of  pure  substance,  the  calorific  value  of  which  has  been  deter- 
mined by  the  Bureau  of  Standards,  Washington,  D.  C.  Of  those  furnished, 
benzoic  acid  is  preferable,  as  it  readily  ignites  and  burns  completely.  If  cane 
sugar  should  be  used,  a  few  milligrams  of  benzoic  acid  are  necessary  to  assist 
ignition  and  correction  must  be  made  for  its  heating  value.  Cane  sugar  does 
not  always  burn  completely. 

Procure  standardized  benzoic  acid  from  the  Bureau  of  Standards.  Compress 
into  pellets  by  means  of  pellet  press  sufficient  benzoic  acid  to  produce  approx- 
imately as  many  calories  as  are  given  by  the  coal,  that  is,  about  7000  calories. 
One  gram  of  benzoic  acid  produces  6320  calories.  Determine  in  the  calorim- 
eter the  temperature  rise  produced  by  the  benzoic  acid  with  the  precautions 
used  in  a  regular  coal  analysis,  correcting  for  thermometer  and  radiation  errors. 
Multiply  the  grams  of  benzoic  acid  taken  by  6320  calories,  add  the  calories 
produced  by  formation  of  nitric  acid  as  obtained  from  the  titration  and  add  the 
calories  produced  by  the  iron  fuse  wire.  Divide  this  sum  by  the  corrected 
rise  in  temperature.  The  quotient  is  the  water-equivalent  of  the  calorimeter. 
The  amount  of  water  added  to  the  bucket  is  then  changed  so  as  to  make  the 
total  calorimeter  equivalent  a  round  number,  such  as  2000  for  the  Atwater 
or  2900  for  the  Mahler.  The  amount  of  water  should  be  sufficient  to  entirely 
immerse  the  bomb  and  avoid  spattering  by  the  stirrer.  Then  restandardize 
with  the  new  quantity  of  water.  The  conditions  of  combustion  should  be  as 
closely  as  possible  like  those  prevailing  during  regular  coal  analysis. 


684 


METHODS   FOR  ANALYSIS   OF   COAL 


DETERMINATION   OF   FUSIBILITY   OF   COAL  ASH 

This  determination  has  become  of  increasing  importance  in  recent  years, 
especially  in  relation  to  mechanical  stokers  and  gas  manufacture.  The  com- 
position of  the  ash,  not  its  amount,  is  the  determining  factor.  Alumina  is 
them  ost  refractory  constituent  and  its  fusing-point,  2000°  C.,  is  lowered  propor- 


FIG.  107. — Hoskins  Electric  Furnace,  Optical  Pyrometer  in  Position,  Also  (X)  Method 
of  Supporting  Cone  in  Graphite  Block. 


tionately  to  the  amounts  of  silica,  alkalies,  and  iron  present.  In  many  coals 
the  amounts  of  all  but  the  latter  do  not  lower  the  fusing-point  sufficiently  to 
cause  trouble,  that  is,  below  1400°  C.  The  amount  of  iron  becomes  then  of 
supreme  importance,  as  the  last  straw  that  breaks  the  camel's  back.  This  is 
popularly  shown  in  the  classification  of  coals  as  red  ash  and  white  ash.  The 


METHODS  FOE  ANALYSIS  OF  COAL      685 

condition  of  the  iron  is  of  great  importance  also,  as  in  the  ferric  condition  it 
has  but  slight  effect,  but  in  ferrous  condition  it  lowers  the  fusion-point  greatly. 
The  influence  of  sulphur  upon  fusing-point  probably  depends  upon  the  accom- 
panying presence  of  iron  as  pyrites.  In  the  coal  bed  in  the  presence  of  burning 
carbon  the  ferric  oxide  may  be  reduced  to  ferrous  oxide  or  not,  according  to 
the  care  of  the  fire  and  the  amount  of  oxygen  supplied.  This  explains  dis- 
crepancies occurring  between  the  facts  of  clinkering  of  the  coal  on  the  grates 
and  the  fusing-point  as  determined  in  a  laboratory  furnace.  The  fusing-point 
varies  in  different  types  of  furnaces  for  the  same  reasons.  It  seems  safest  to 
choose  such  furnaces  in  laboratory  tests  as  give  reducing  atmospheres  and 
hence  lower  fusing-point,  indicating  the  possible  danger. 

A  convenient  furnace,  for  high  temperatures  especially,  is  the  Hoskins  Elec- 
tric Furnace.  The  heat  is  generated  by  passing  a  heavy  alternating  current 
of  low  voltage  through  a  series  of  carbon  plates.  Temperature  is  regulated 
by  compression  of  these  plates.  This  furnace  uses  a  60-cycle  alternating  cur- 
rent, 220  volts,  about  40  amperes.  The  current  is  transformed  by  an  air-cooled 
transformer  to  a  current  of  10  volts.  The  maximum  temperature  produced 
by  the  furnace  is  about  2000°  C. 

The  coal  is  burned  to  ash  at  as  low  a  temperature  as  possible  in  clay  dishes. 
The  ash  is  moistened  with  water  and  moulded  into  the  shape  of  a  Seger  cone 
(^  in.  by  2|  ins.)  by  pressing  into  a  mould  conveniently  made  of  lead.  A  piece 
of  thin  paper,  moistened,  is  laid  in  the  mould  to  facilitate  removal  of  the  cone. 
Some  coals  may  require  10%  dextrin  paste  as  a  binder,  but  it  is  usually  unnec- 
essary. The  use  of  smaller  cones  has  recently  been  advocated.  The  cones 
may  be  set  in  triangular  holes  in  a  Dixon  graphite  block  and  placed  in  the  furnace 
so  that  the  cone  is  horizontal.  This  position  gives  as  concordant  results  as 
the  vertical  position,  if  not  closer.  The  fusing-point  is  taken  when  the  cone 
droops  into  a  vertical  position.  The  temperature  must  not  rise  too  rapidly 
when  near  the  fusing-point,  about  5°  C.  per  minute.  The  temperature  is  con- 
veniently read  by  a  fixed-focus  total-radiation  pyrometer  or  an  optical  pyrometer 
of  the  Wanner  type.  Reducing  atmospheres  preclude  the  use  of  metallic  couples 
at  high  temperatures. 

NOTE.  The  methods  in  this  chapter  are  based  upon  those  in  use  at  the  Mt. 
Prospect  Laboratory,  of  the  Department  of  Water  Supply,  Gas  and  Electricity, 
New  York  City.  The  method  for  fusibility  was  obtained  originally  from  the  Lab- 
oratory of  the  Consolidated  Gas  Company,  New  York  City. 

REFERENCES 
General 

E.  E.  Somermeier,  "Coal,  Its  Composition,  Analysis,  Utilization  and  Valuation." 
McGraw-Hill  Book  Company. 

Von  Jiiptner,  "  Heat,  Energy  and  Fuels."     McGraw-Hill  Book  Company,  1908. 

A.  Humboldt  Sexton,  "Fuel  and  Refractory  Materials."     Van  Nostrand  &  Co.     1910. 

Reports  of  Coal  Analysis  Committee,  American  Society  for  Testing  Materials  and 
American  Chemical  Society.  Jour.  Ind.  Eng.  Chem.,  Vol.  5,  1913,  p.  517. 
Proc.  Am.  Soc.  Testing  Materials,  Vol.  14,  Report  Committee  E4.  Proc.  Am. 
Soc.  Testing  Materials,  June,  1915,  convention. 

Bulletin  No.  41,  Bureau  of  Mines,  pp.  74-91. 

Technical  Paper,  No.  8,  Bureau  of  Mines.     "Methods  of  Analyzing  Coal  and  Coke." 

Fieldner,  Jour.  Ind.  Eng.  Chem.,  Vol.  5,  Apr.,  1913,  p.  270.  "Accuracy  and  Limi- 
tations of  Coal  Analysis." 

Bulletin  No.  332,  U.  S.  Geological  Survey.  "Report  of  the  Fuel  Testing  Plant  at 
St.  Louis,  Mo." 


686      METHODS  FOR  ANALYSIS  OF  COAL 

Sampling 

Technical  Paper  No.  1,  Bureau  of  Mines.     "The  Sampling  of  Coal  in  the  Mine." 
Technical  Paper  No.  76,  Bureau  of  Mines.     "Notes  on  the  Sampling  and  Analysis 
of  Coal." 

Moisture 
Bulletin  No.  28,  Bureau  of  Mines,  1911,  51  pp. 

Volatile  Combustible  Matter 

Bulletin  No.  1,  Bureau  of  Mines.     "The  Volatile  Matter  of  Coal." 

Fieldner  and  Hall,  Proc.  8th  Int.  Cong.  App.  Chem.,  Vol.  10,  1912,  p.  139.     "The 

Influence  of  Temperature  on  the  Determination  of  Volatile  Matter  in  Coal." 
Fieldner  and  Davis,  Jour.   Ind.   Eng.   Chem.,   Vol.  2,  July,    1910,  p.    304.     "Some 

Variations  in  the  Official  Method  for  the  Determination  of  Volatile  Matter  in 

Coal." 
A.  G.  Stillwell.     The  Chemist  Analyst,  No.    13,  April,   1915,  p.  9.     "Note  on  Coal 

Analysis." 

Volatile  Sulphur 

H.  F.  Muer,  Jour.  Ind.  Eng.  Chem.,  Vol.  3,  August,  1911.  "The  Determination  of 
Sulphur  in  Coal  by  Means  of  Jackson's  Candle  Turbidimeter."  See  also  S.  H. 
Register,  under  "  Calorimetry." 

Calorimetry 

Bulletin  No.  124,  Bureau  of  Animal  Industry.      "Methods  and  Standards  in  Bomb 

Calorimetry." 

Circular  No.  11,  Bureau  of  Standards.     "Standardization  of  Bomb  Calorimeters." 
S.  H.  Register,  Jour.  Ind.  Eng.  Chem.,  Vol.  6,  October,  1914,  p.  812.     "Oxidation  of 
Sulphur  Compounds  of  Coal,  and  of  Nitrogen  in  the  Bomb  Calorimeter,  and 
the  Correction  to  be  Applied  in  Determining  the  Heating  Value  of  Coal." 

Melting-point  of  Ashes 

E.  G.  Bailey,  Power,  Vol.  34,  No.  22,  p.  802.  "The  Fusing  Temperature  of  Coal 
Ash." 

E.  J.  Constan,  Z.  Ver.  Gas  und  Wasser   Oesterr.     (Jour.  Gas  Lighting,  124,  572.) 

"Melting-point  of  Coal  Ashes." 

Palmenberg,  Jour.  Ind.  Eng.  Chem.,  Vol.  6,  1914,  p.  277.  "Relation  of  Composition 
of  Ash  in  Coal  to  its  Fusing-point." 

Burgwin,  Jour.  Ind.  Eng.  Chem.,  Vol.  6,  1914,  August,  p.  694.  "Relation  of  Compo- 
sition of  Ash  in  Coal  to  its  Fusing-point." 

Fieldner  and  Hall,  Jour.  Ind.  Eng.  Chem.,  Vol.  7,  June,  1915,  p.  474;  and  May, 
p.  399;  and  Sept..  p.  742.  "Fusibility  of  Coal  Ash  in  Various  Atmospheres," 
Vol.  7,  Oct.  1915,  p.  829.  "A  New  Method  and  Furnace  for  the  Determination 
of  the  Softening  Temperature  of  Coal  Ash  under  Fuel  Bed  Conditions." 

F.  C.  Hubley,  Engineers'  Club  of  Philadelphia,   Proc.,    January,    1915,    pp.  35-83. 

"Bituminous  Coal;     Predetermination   of   Their  Clinkering  Actions  by  Labo- 
ratory Tests." 

Miscellaneous 

Technical  Paper  No.  5,  Bureau  of  Mines.     "Constituents  of  Coal  Soluble  in  Phenol." 
Technical  Paper  No.  16,  Bureau  of  Mines.     "Deterioration  and  Spontaneous  Heating 

of  Coal  in  Storage." 

Bulletin  No.  382,  U.  S.  Geological  Survey.     "Effect  of  Oxygen  in  Coal." 
Technical  Paper  No.  2,  Bureau  of  Mines.     "Escape  of  Gas  from  Coal." 
Technical  Paper  No.  65,  Bureau  of  Mines.     "Study  of  the  Oxidation  of  Coal." 
H.  C.  Porter,  Jour.  Ind.  Eng.  Chem.,  Vol.  7,  March,  1915,  p.  239.     "The  New  Knowl 

edge  of  Coal  and  Its  Practical  Application." 
Bulletins  Nos.  471J  and  531  Af,  U.  S.  Geological  Survey.     "Miscellaneous  Analyses  of 

Coal  Samples  from  Various  Fields  of  the  United  States." 
Bulletin  No.  54,  Bureau  of  Mines.     "Publications  on  Fuel  Technology." 


GAS  ANALYSIS 

AUGUSTUS  H.  GiLL1 

SAMPLING 

The  process  consists  in  the  insertion  of  a  suitable  tube  into  the  flue  or  duct, 
and  the  withdrawal  of  the  gas  sought,  by  some  sort  of  pump. 

Tubes.  The  tube  employed  varies  with  the  nature  of  the  gas  and  its  tem- 
perature. Ordinarily,  a  combustion  tube  a  meter  long  of  16-17  mm.  outside 
diameter,  which  has  been  drawn  down  to  7  mm.  at  one  end,  to  facilitate  the  at- 
tachment of  rubber  tubing,  is  used.  These  soften  at  about  500°  C.  For  higher 
temperatures  we  have  a  choice  of  quartz,  porcelain  tubes  of  about  the  same  di- 
mensions, or  water-cooled  metal  tubes.  Uncooled  metal  tubes  cannot  be  em- 
ployed above  250°  without  danger  of  reduction  of  the  oxides  of  the  metals 
composing  the  tube,  by  the  carbonic  oxide  contained  in  the  gases.2  If  porcelain 


FIG.  108. 

tubes  be  used,  they  should  be  glazed  within  and  without,  to  prevent  the  trans- 
fusion through  them  of  the  lighter  gases  like  methane  and  hydrogen:  they,  as 
well  as  glass  tubes,  should  be  warmed  before  insertion  into  a  hot  flue.  The 
construction  of  the  water-cooled  tubes  will  be  evident  from  Fig.  108. 

For  cooling  the  gas,  the  tube  should  not  be  inserted  to  its  full  length. 
Rolls  of  wire  gauze  can  be  inserted  near  the  cool,  drawn-out  end  of  the  tube: 
these  will  serve  for  the  removal  of  soot  and  dust.  The  removal  of  dust  may  be 
further  effected  by  the  use  of  plugs  of  asbestos  or  glass  wool. 

The  place  from  which  the  gas  is  collected  should  be  so  chosen  as  to  give  a 
representative  sample,  and  all  openings  except  those  intended  for  the  inlet  of  air, 
stopped  up.  In  a  circular  duct  or  chimney  the  average  velocity  of  the  gases  is 
usually  at  a  point  one-third  the  distance  from  the  wall  to  the  center.  In  case  of 
a  boiler,  the  setting  should  be  carefully  inspected,  all  cracks  filled  with  mortar, 
and  the  clean  out  doors  made  tight.  The  fact  that  bricks  themselves  are  porous 
must  not  be  lost  sight  of,  and  new  settings  should  be  sized  and  given  a  coat  of 
whitewash.  If  possible  the  tube  should  be  inserted  below  the  damper  to  avoid 

1  Professor  of  Technical  Analysis,  Massachusetts  Institute  of  Technology. 

2  Fischer,  "  Technologic  der  Brennstoffe,"  1880,  p.  221,  cites  an  instance  in  which 
C02  was  changed  from  1.5  in  the  mixture,  to  26%  by  the  passage  through  an  iron 
tube  heated  to  dull  redness. 

687 


688 


GAS  ANALYSIS 


leakage  from  that  source.  A  second  hole  should  be  made  for  the  introduction  of 
an  oil  tube  for  the  thermometer.  The  joints  around  these  tubes  should  be  made 
tight  with  mortar,  plaster  of  Paris,  or  in  the  case  of  a  temporary  connection, 
putty  or  wet  cotton  waste.  Care  should  be  taken  not  to  insert  the  tube  so  close 
to  the  source  of  heat  as  to  withdraw  the  gases  in  a  dissociated  or  partially  decom- 
posed condition.  For  sampling  the  gases  from  different  zones  of  a  blast  furnace, 
water-cooled  tubes  are  made  which  can  be  screwed  together  to  produce  the 
desired  length. 

Pumps.  Where  a  sufficient  head  of  water  (15  or  20  Ibs.  is  enough  for  our 
purpose)  is  available,  the  Richards  jet  pump,  Fig.  109,  may  be  used.  This  can  be 
easily  constructed  in  glass  as  shown 
in  Fig.  110  and  the  glass  jets  drawn 
down  to  suit  the  water  pressure.  It 
may  be  noted  that  the  pump  may  be 
operated  with  steam  equally  as  well 
as  with  water. 

In  case  a  head  of  water  be  not 
accessible,  pumps  employing  a  fall  of 
water  —  the  B  u  n  s  e  n 
pump,  Fig.  Ill,  may  be 
used.  This  consists  es- 
sentially of  a  quarter- 
inch  tee,  one  branch  of 
which  is  connected  with 
the  water  supply,  an- 
other with  the  vessel  to 
be  evacuated,  while  the 
third  is  connected  with 
10 l  or  15  ft.  of  quarter- 
inch  pipe,  preferably 
lead.  The  water  in  this 
acts  as  a  moving  piston 
and  draws  the  gas  in 
after  it. 

Where  none  of  these  is  available,  some  type  of 
a  power-driven  pump,  or  an  ordinary  rubber  syringe 
bulb  may  be  employed.  Instead  of  these,  two  aspi- 
rator bottles — of  gallon  or  two-gallon  size — will  fur- 
nish the  necessary  suction.  These  are  made  by 
passing  two  glass  tubes  bent  at  right  angles  through 
each  rubber  stopper  fitting  the  bottles :  one  branch 
of  one  elbow  stops  just  under  the  stopper,  while  a 
branch  of  the  other  goes  to  the  bottom  of  the  bottle. 
The  tubes  carrying  the  long  branches  are  connected 
by  a  3-  or  4-foot  piece  of  quarter-inch  rubber  tubing  provided  with  a  screw  pinch- 
cock.  Upon  setting  one  bottle  higher  than  the  other  and  blowing  into  its  shorter 
tube,  water  siphons  through  the  longer  into  the  lower  bottle,  producing  suction  in 
the  upper.  This  is  sometimes  used  for  taking  a  continuous  sample  extending 


FIG.  109. 


FIG.  110. 


FIG.  111. 


For  the  highest  vacuum  over  32  ft. — the  height  of  the  water  barometer. 


GAS  ANALYSIS 


689 


over  several  hours.    Strong  brine  is  a  suitable  solution  for  the  bottles,  since  it 
possesses  the  advantage  over  water  in  absorbing  less  carbon  dioxide. 

Containers  for  Samples.  These  are  of  glass,  preferably  of  the  shape  shown  in 
Fig.  112.  Being  pear  shaped,  the  vessel  is  completely  emptied,  leaving  no  liquid 
to  exercise  a  solvent  action  on  the  gas.  The  tub- 
ing shown  in  the  figure  is  of  lead,  which  can  be 
safely  used  for  chimney  gases  after  it  becomes 
attacked  by  them.  Its  obvious  advantage  is  found 
in  the  fact  that  it  bends  rather  than  breaks.  Glass 
bottles — parts  of  the  aspirator  just  described — 
may  be  used;  the  rubber  connection  should  be  thick, 
carefully  wired  on  and  provided  with  screw  pinch- 
cocks.  The  long  tube  should  carry  a  short  piece  of 
rubber  tubing  within  the  bottle  reaching  to  its  side; 
by  tipping  it  the  water  can  be  more  completely  run 
out  through  this  tube.  The  use  of  metal  containers 
in  general  is  not  recommended,  as  those  of  zinc  or 
galvanized  iron  are  attacked  by  carbon  dioxide; 
where  the  gases  do  not  act  upon  the  metals  they 
may  of  course  be  advantageously  employed.  To 
ensure  tightness,  the  rubber  stoppers  used  should 
be  held  in  by  screws  which  fit  into  a  brass  plate  on 
top  of  the  stopper  and  into  wire  loops  about  the 
neck  of  the  bottle.  This  compresses  the  stopper 
about  the  tubes  and  into  the  bottle  neck,  making 
a  thoroughly  tight  joint.  Or  the  brass  plate  may 
be  replaced  by  a  piece  of  sole  leather  and  wire 
passed  over  this  after  the  manner  of  wiring  down 
the  bottles  containing  carbonated  waters. 

The  use  of  rubber  bags  is  not  to  be  recommended,  as  they  absorb  certain  gases 
and  are  oxidized  by  others:  the  most  satisfactory  containers  are  glass'tubes  pro- 
vided with  drawn-out  ends  which  can  be  sealed  in  the  lamp  flame. 

In  connecting  up  the  sampling  tube,  container  and  pump,  the  use  of  rubber 
tubing  is  to  be  avoided  as  much  as  possible  for  the  reason  just  given. 


FIG.  112. 


MEASUREMENT   OF   GAS   IN   LARGE    QUANTITIES.     METERS 


Several  types  of  instruments  are  available  for  this  purpose. 

The  wet  meter 
The  dry  meter 


Measure  total  gas  passed — not  for  acid  gases. 


All  these  measure 
velocity  simply 


For  all  gases  par- 
ticularly acid 


The  Pitot  tube  or  Davis  anemometer 

The  Rotameter  or  Thorp  gauge 

The  Capometer 

The  Thomas  electric  meter 

The  orifice  meter 

The  anemometer 

The  first  two  meters  show  all  the  gas  passing  through  the  system  while  the 
others  simply  measure  the  rate  of  flow:  with  these  the  size  of  the  pipe  must  be 


690  GAS  ANALYSIS 

known.  Of  all  these  instruments,  the  wet  meter  and  Thomas  meter  are  probably 
the  most  accurate.  They,  however,  like  some  of  the  others,  cannot  be  used  with 
corrosive  gases,  being  constructed  of  metal;  hence  the  Pitot  tube,  rotameter  and 
capometer  are  the  ones  to  be  employed  in  chemical  works. 

The  wet  meter  consists  of  a  cylindrical  drum  divided  into  four  spiral  compart- 
ments, suspended  in  a  bath  of  water,  surrounded  by  a  tight  casing:  the  pressure 
of  the  gas  causes  the  drum  to  rotate,  emptying  a  drumful  of  gas  into  the  casing 
and  pipes.  It  must  be  set  level,  the  water  level  carefully  adjusted  to  the  mark 
on  the  glass  gauge,  with  its  top  open,  as  well  as  the  inlet  and  outlet  pipes  of  the 
meter.  The  higher  the  water  level  the  faster  the  meter.  The  dry  meter  consists 
of  a  pair  of  metal  bellows,  with  sides  of  leather  soaked  in  oil,  on  either  side  of  a 
diaphragm,  and  connected  with  slide  valves  so  that  a  bellowsful  of  gas  is  alternately 
emptied  into  the  upper  part  of  the  meter  and  piping.  The  vibrations  of  the 
bellows  produced  by  the  gas  pressure  are  transmitted  to  clockwork  and  indexes. 
It  is  to  be  noted  that  the  indexes  apparently  read  one-tenth  of  the  actual  volume 
passed:  the  index  must  make  a  complete  circuit  to  register  the  amount  stamped 
on  the  dial.  A  small  index  and  dial  are  usually  present  for  testing  the  meter,  and 
a  tolerance  of  2%  is  allowed  by  law.  This  testing  is  done  by  meter-pr overs,  care- 
fully calibrated  gas  holders  kept  at  constant  temperature  and  the  rate  determined 
at  different  speeds.  The  meter-pro vers  are,  in  their  turn,  calibrated  by  a  cubic 
foot,  standardized  at  the  Bureau  of  Standards.  It  should  be  noted  that  all  this 
calibration  is  corrected,  not  to  standard  conditions  (0°  C.  and  760  mm.),  but  to 
the  cubic  foot  as  fixed  by  law — gas  saturated  with  moisture  at  60°  F.  and  30 
inches. 

The  Pitot  Tube.  Fig.  1 13.  This  consists  of  two  glass-tubes,  D,  of  about  ^  inch 
internal  diameter,  inserted  in  the  gas  stream:  one  is  bent  at  right  angles  and  is 
set  so  that  it  receives  the  impact  of  the  gas  movement;  the  other  merely  registers 

the  pressure  of  the  gas  in  the  pipe.  The 
point  of  insertion  of  these  tubes  in  the 
chimney  or  duct  should  be  in  a  long 
straight  run  of  pipe,  so  as  to  be  as  free 
from  eddies  as  possible.  Davis1  says 
that  authorities  differ  as  to  whether  the 
tubes  should  be  a  third  or  one-sixth  of 
the  diameter  from  the  circumference  to 
show  the  mean  speed:  he  states  further 
that  each  flue  or  chimney  is  a  separate 
problem  and  as  a  result  of  hundreds  of 
measurements  there  seems  to  be  "no 
FIG.  113.  settled  proportionate  distance  corre- 

sponding to  the  mean  velocity." 

The  glass  tubes  are  connected  by  rubber  tubing,  C,  through  a  reverser,  B, 
with  a  U-tube  A,  which  is  either  set  vertically,  inclined  30°,  or  one  in  ten — this 
carries  a  vernier  reading  to  hundredths  of  an  inch  so  that  readings  to  thousandths 
are  feasible.  The  U  tube  is  filled  with  solutions  of  different  specific  gravity, 
although  ether  of  0.74  sp.gr.  is  the  one  commonly  employed.  The  difference 
between  the  arms  of  the  U-tube  represents  the  difference  between  the  kinetic  and 
static  pressures  of  the  gas  in  the  flue  or  chimney. 

1 "  Handbook  of  Chemical  Engineering,"  1, 197,  also  for  the  tables  for  its  use. 


GAS  ANALYSIS 


691 


The  formulae  for  calculating  the  velocity  are  V  =VpX 28.55  where  V  =  velocity 

in  feet  per  second,   p   the  anemometer  reading,   or  „ ( 

twice  the  height  of  the  ether  column,  the  gas  being 
at  a  temperature  of  15.5°  C.  (60°  F.)  and  30  inches 
barometric  pressure.  As  this,  however,  rarely  occurs, 
the  formula  is 

/    /I£O_I_*C 

X  28.55 

giving  the  speed  for  the  high  temperature  (°F.). 

The  Rotameter,1  Fig.  114.  This  is  a  German  in- 
strument depending  upon  the  height  to  which  a  float 
is  carried  in  a  glass  tube  by  the  velocity  of  the  stream 
of  gas.  A  modification  of  it  wras  used  by  some  of  the 
gas-lighting  companies  under  the  name  of  the  Thorp 
gauge. 

It  consists  of  a  graduated  glass  tube  fixed  upon  a 
tripod  and  provided  with  a  plumb  line  so  that  it  can 
be  set  vertically:  gas  passes  in  at  the  lower  end,  raises 
the  clay  or  talc  float  to  a  certain  height  and  passes 
out  at  the  top.  The  height  to  which  the  float  is 
raised  is  noted  on  the  graduations  of  the  tube.  The 

formula  for  its  use  is 


FIG.  114. 

V  —  volume  gas  as  shown  by  reading  of  in- 
strument, M  its  specific  gravity  =  1.0. 

V  =  volume  desired,  Mi  =sp.gr.  of  gas. 

It  is  made  in  all  capacities  from  0.2  cu.ft., 
per  hour  up. 

The  Capometer.2  Fig.  115.  This  consists 
of  a  series  of  capillary  tubes  of  different  sizes 
through  which  the  gas  is  made  to  pass  and  the 
pressure  thus  produced  noted  in  the  U-tube  A. 
Each  capillary  is  calibrated  and  curves  of  gas 
flow  are  made  corresponding  to  different  pres- 
sures in  the  U-tube  and  various  capillaries. 
An  instrument  made  with  capillaries  1-4  mm. 
in  diameter  has  a  capacity  of  0.004  to  70  cu.ft. 
per  hour. 

The  Thomas  Electric  Gas  Meter.3  This 
depends  upon  the  principle  that  if  the  specific 
heat  of  the  gas  be  known,  and  an  amount  of 
energy  be  put  into  it,  by  means  of  a  coil,  sufficient  to  keep  a  certain  difference 

1  Anon.,  Ch.  Abs.,  5, 1695,  1911. 

2  J.  Gasbeleuchtung,  55,  557,  1912. 
*  Thomas,  J.  Frank.  Inst.,  172, 411. 


FIG.  115. 


692  GAS  ANALYSIS 

of  temperature  between  two  thermometers,  one  before  and  one  after  the  coil,  this 
energy  is  a  direct  measure  of  the  volume  of  gas  flowing.  Two  electrical  thermom- 
eters are  placed  in  the  stream  of  gas  with  a  heating  coil  between  them:  2°  differ- 
ence of  temperature  is  automatically  maintained  between  the  thermometers  and 
the  energy  to  preserve  this  difference  of  temperature  (.0127  watt  hour  per  stand- 
ard unit  of  gas)  is  read  off  on  the  meter  as  cubic  feet  of  gas.  It  is  independent  of 
temperature  or  pressure  changes  in  the  gas,  and  is  used  up  to  gas  pressures  of 
180  Ibs.  per  square  inch.  This  is  used  in  a  Western  gas  works  measuring 
200,000  ft.  of  gas  per  hour. 

The  Orifice  Meter.  In  this  the  same  principle  is  used  as  in  measuring  water, 
by  determining  the  diminution  in  pressure  as  registered  on  delicate  gauges  before 
and  after  the  gas  has  passed  through  a  standard  orifice.  It  is  largely  used  for 
measuring  natural  gas. 

The  anemometer  is  used  ordinarily  for  measuring  currents  of  air  leaving  or 
entering  a  room,  analogous  to  its  employment  in  meteorology. 


MEASUREMENT    OF   GAS   IN    SMALL    QUANTITIES.      GAS 

BURETTES 

Here  may  be  mentioned  the  Hempel  gas  burette,  made  for  accurate  work  with 
a  compensation  tube;  the  bulbed  Orsat  or  Bunte  burette;  the  separatory  funnel 
and  graduate. 

The  Hempel  Gas  Burette,  Fig.  122,  consists  of  a  100-cc.  burette  graduated 
in  fifths  of  a  cubic  centimeter,  provided  with  a  short  capillary  at  the  top  and  closed 
with  a  rubber  connector  and  pinch-cock,  and  a  wider  tube  at  the  bottom,  over 
which  the  &-in.  rubber  tube  is  drawn,  which  connects  it  with  the  leveling  tube 
of  similar  size  and  length  to  the  burette.  Like  all  volumetric  instruments,  it 
should  be  carefully  calibrated.  It  is  manipulated  by  filling  the  leveling  tube 
completely  with  water,  opening  the  pinch-cock  on  the  top  of  the  burette  and 
filling  it  with  water.  The  gas  to  be  analyzed  is  sucked  in  and  measured  as 
with  the  Orsat  apparatus,  p.  697. 

For  accurate  work  the  burette  is  enclosed  in  a  water  jacket,  connected  with 
a  compensating  tube  also  contained  in  water  jacket,  and  provided  with  a 
manometer  so  that  changes  in  temperature  or  pressure  may  be  neutralized. 
Mercury,  instead  of  water,  is  the  confining  liquid.  Instead  of  a  straight  tube, 
Bleier  *  used  one  consisting  of  a  string  of  bulbs  of  about  10-cc.  capacity:  by 
means  of  a  side  connection  with  a  graduated  10-cc.  burette,  volumes  of  10-cc. 
multiples  and  fractions  can  be  measured.  The  Orsat,  Fig.  120,  and  Elliott 
apparatus,  Fig.  121,  use  bulbed  burettes  to  shorten  them,  connected  with  leveling 
bottles. 

Separatory  Funnel  and  Graduate,  Fig.  130.  From  the  water  which  has  flowed 
out,  the  quantity  of  gas  can  be  determined.  See  p.  721. 

iBerichte,  31, 1,238. 


GAS  ANALYSIS 


693 


ABSORPTION   APPARATUS,  TUBES,  AND   PIPETTES 

These  are  quite  varied  according  to  the  purpose  for  which  they  are  intended. 
A  very  efficient  form  is  the  Friedrichs  Spiral  Gas  Washing  bottle,  Fig.  116;  here 
the  gas  has  to  pass  through  a  long  spiral  path.  Dennis1  recommends  this  for 
the  absorption  of  sulphur  dioxide.  The  gas  is  run  through  a  solution  until  a 
color  change  takes  place.  Were  the  reagent  to  be  washed  out  and  titrated  it 
would  not  seem  so  well  adapted  on  account  of  the  difficulty  of  thoroughly  wash- 
ing it. 

The  Varrentrapp  and  Will  bulbs,  Fig.  117,  the  use  of  which  is  evident  from  the 
figure,  are  used  for  the  absorption  of  ammonia  in  illuminating  gas.  The  W^olff 


FIG.  117. 


FIG.  116. 


FIG.  119. 


FIG.  118. 


absorption  tube,  Fig.  118,  the  empty  arm  of  which  is  filled  with  beads  or  broken 
glass  is  used  for  the  absorption  of  carbon  monoxide  by  blood.  The  bulbed  tube, 
provided  with  a  small  jet,  is  generally  used  for  containing  standard  solutions  of 
acid,  alkali,  or  potassium  permanganate  or,  in  general,  a  solution  which  is  to 
be  titrated  after  absorption.  Where  the  presence  of  a  gas  as,  for  example,  water 
vapor,  is  to  be  determined  by  the  increase  of  weight  of  the  reagent  used,  Winkler's 
spiral,  Fig.  1192,  may  be  employed. 

Pipettes — Particularly  for  the  Orsat  Apparatus.  These  are  ordinarily  filled 
with  glass  tubes,  but  various  modifications  have  been  proposed:  these  are  the 
bubbling  type  of  Hankus,  the  spiral  bubbling  variety  of  Nowicki-Heinz  and  a 
combination  of  the  Friedrichs  wash  bottle  proposed  by  Dennis.  All  these  suffer 
from  the  very  serious  disadvantage  of  a  glass  three-way  stopcock  at  the  top,  which 
it  is  practically  impossible  to  prevent  from  sticking,  unless  the  apparatus  be  used 
by  one  person  and  that  one  exceptionally  careful  and  painstaking.  Dennis3 
has  shown  that  one  variety  is  no  more  rapid  than  the  original  and  some  of  the 
others  but  little  more  so.  When  it  is  further  considered  that  they  cost  four  times 
as  much, 4  their  use  would  seem  of  doubtful  expediency. 

*  "  Gas  Analysis,"  p.  274, 1913. 

2  Called  "  Winkler's  Bulbs  "  in  the  apparatus  catalogs. 

3  Ibid.,  p.  83. 

4  Ten  dollars. 


694 


GAS  ANALYSIS 


It  is  interesting  to  note  further  that  Anderson  1  has  shown  that  with  the  modi- 
fied potassium  pyrogallate  which  he  uses,  the  original  Orsat  slightly  modified, 
to  allow  the  precipitate  to  settle,  is  the  best. 

EXAMINATION   OF  THE  GASES 

The  qualitative  examination  of  a  gaseous  mixture  is  rarely  resorted  to  in 
technical  work:  a  sufficiently  close  idea  of  the  gases  present  can  be  obtained  by 
a  consideration  of  the  reactions  involved  in  the  various  operations.  It  is,  however, 
not  safe  to  rely  upon  this  in  matters  of  importance,  as  conditions  may  change: 
for  example  if  the  gases  be  dry  or  dilute,  hydrogen  sulphide  and  sulphurous 
anhydride  can  exist  together.  Similarly  in  sewage  gases,  all  the  gas  absorbed  by 
cuprous  chloride  is  probably  not  carbon  monoxide.  The  means  of  identifying 
the  different  gases  will  be  found  under  each  gas. 

Detection  and  Determination  of  the  Various  Gases 

Clemens  Winkler  divided  the  gases  into  seven  groups  according  to  their 
behavior  with  various  solvents.    These  were  contained  in  suitable  absorption 
tubes  or  vessels  and  the  gases  passed  through  them.    His  scheme  was  as  follows : 
Gases  absorbed  by 

I.  H2S04 1.7  sp.gr.;  NH3,  (N203),  N204. 
II.  KOH  1.3  sp.gr.;  C12,  HC1,  (CN)2,  HCN,  S02,  H2S,  SiF4,  C02. 

III.  AgN03;  PH3,  AsH3,  SbH3. 

IV.  Pyro;  O2,  (O3). 
V.  Cud;  CO. 

VI.  AcidFeS04l:2;NO. 
VII.  Unabsorbed;  H2,  CH4,  C2H2,  C2H4,  N20,  N2,  COS,  and  the  noble  gases. 

The  following  tables  give  the  specific  gravity  referred  to  air,  the  solubility 
in  water  at  20°,  the  qualitative  tests  and  quantitative  methods  of  determination 
of  these  gases :  additional  means  will  be  found  mentioned  under  the  several  gases 
themselves.  GRonpI 

Gases  Absorbed  by  H2SO4 1.7  sp.gr. 


Name  

Ammonia. 

Nitrous  anhydride. 

Nitrogen  tetroxide. 

Gravity,  air  =  1  

0.589 

1.590 

Qualitative  Tests  

Fumes  w.  HC1  on  a 

Acts  like  a  mixture 

Absorb  in  KOH, 

rod.     Nessler's  re- 

of NO  and  NO2. 

test  for  nitrites. 

agent. 

Quantitative  Det'n  .  . 

Absorption  in  stand- 

Absorption in  N/10 

ard  acid.     Or 

KMnO4-2KMnO4 

3NaBrO+2NH3 

+  10NO2+3H2SO4 

=  N2+3NaBr+ 

+2H2O  =  10HN03 

3H2O.    Or  absorp- 

+K2S04+ 

tion  in  water  and 

2MnSO4.     Or  in 

Nesslerization. 

standard  alkali. 

pp.  291,  537. 

Solubility  20°  C.,  Ice. 

water  absorbs  cc.  .  . 

678 

Forms  HNO3,HNO2. 

1  J.  Ind.  and  Eng.  Chem.,  8,  131-3,  1916. 


GAS  ANALYSIS 


695 


GROUP  II 
Gases  Absorbed  by  KOH  1.3  sp.gr. 


Name 

Chlorine. 

Hydrochloric  acid. 

Cyanogen. 

Gravity  air  =  1  . 

2.449 

1.259 

1.799 

Qualitative  Test  

KI  starch  paper. 

Fumes  w.  NH3. 

Pass  through  mix- 

ture of  FeSO4 

1  :  10+KOH, 

1  :  3. 

and  ppt.  as  Prus- 
sian blue  w.  ferric 

alum  and  H2S04.1 

Quantitative  Det'n  .  . 

2KI+C12  =  2KC1  + 
12.     Or  absorption 

Absorption  in  stand- 
ard alkali   or  sil- 

w. KOH. 

ver  nitrate. 

Solubility  20°  C.,  Ice. 

water  absorbs  cc  .  . 

2.15 

442 

4.5 

Hydrocyanic  acid 

Sulphur  dioxide. 

Hydrogen  sul- 

Silicon fluoride. 

Carbon  dioxide. 

phide. 

0.936 

2.213 

1.177 

3.60 

1.520 

Absorption  in 
KOH  and 

Fuchsine  paper 
bleached  or 

PbAc2  paper, 
absorption  by 

None 
3SiF4+4H20 

BaO2H2  on 
black  rod. 

FeSO4  and 

KIO3  starch 

I  solution. 

=  SiO4H4+ 

Absorption 

FeCl2  =  Prus- 

paper. 

2H2SiF6. 

w.  KOH  or 

sian  blue.    Ab- 

SO2+2I+2H2O 

H2S+2I  = 

BaO2H2  and 

sorption  w. 

=  H2SO4+2HI. 

2HI+S. 

titration. 

KOH  or  acid 

AgNO3.2 

Very  sol 

36.4 

2.67 

Decomposed. 

0.892 

GROUP  III 

Gases  Absorbed  by  AgNO3. 


Name              

Hydrogen  phosphide, 

Hydrogen  arsenide, 

Hydrogen  antimo- 

Gravity,  air  =  1  

Phosphine, 
1.175 

arsine. 
2.696 

nide,  stibine. 
4.330 

Qualitative  Test  

Neutral  H2O  Solu- 
tion KI+HgI2= 
cryst.  orange  yel. 
ppt.  PHg3I3.3 

Blk.  ppt.  of  AsAg3  w. 
AgN03, 

Blk.ppt.ofSbAg,w. 
AgN03. 

Quantitative  Det'n  .  . 

Pass  through  Br 
water  and  ppt. 
H3PO4  as  usual. 

Absorb  w.  NaCIO 
cont.  3%  Cl.4 

Decompose  w. 
tartaric  acid  and 
det.  Sb. 

Solubility  20°  C.,  Ice. 
water  absorbs  cc.  .  . 

0.02 

about  5 

Slight. 

iNauss,  J.  Gasbeleuchtung,  43,  969,  1900. 
2  Rhodes,  J.  Ind.  and  Eng.  Ch.,  4,  652,  1912. 
3Lemoult,  Compt.  rend,  139,  478,  1904. 
4Reckleben,  Z.  ang.  Ch.,  19,  275,  1906. 


696 


GROUP  IV 


GAS  ANALYSIS 

GROUP  V 


GROUP  VI 


Absorbed  by  p 
gal 

Name  

rtassium  pyro- 
late 

Oxygen. 
1.105 

Darkening  of 
light  brown 
"  pyro." 

By"Pyro." 
CuCl   in    ab- 
sence of  CO. 

0.028 

Ozone. 
1.62 

MnCl2  paper;  KI 
Starch  paper, 
N2O4  and  H2O2 
being  removed 
by  KMnO4. 

0.6atO° 

Absorbed  by 
cnprous  chloride 

Carbon  monoxide. 
0.967 

Absorb  in  blood, 
and  examine 
w.  spectroscope. 

Absorption  w. 
CuCl. 

0.023 

Absorbed  by 
FeSOt  1  :  2  acidu- 
lated w.  HiSO* 

Xitric  oxide. 
1.038 

Oxidize,  absorb  in 
KOH  and  test 
for  nitrites. 

Absorb  in  FeSO4 
1  :  2  acidulated 
w.EkSChorwith 
KMnO4asN2O4. 

0.267 

Gravity,  air  =  1 

Qualitative 
Test 

Quantitative 
Det'n  

Solubility 
20°  C.,  1  cc. 
water  ab- 
sorbs cc  

GROUP  VII 

Unabsorbed 

Name  

Hydrogen. 

Methane. 

Ethylene 

Acetylene 

(ethene). 

(ethine). 

Gravity,  air  =  l..  . 

.0696 

0.554 

0.968 

0.899 

Qualitative  Test.  . 

None. 

None. 

Red  ppt.  w. 

am.  CuCl 

(explosive!). 

Quantitative  Det  'n 

By  combustion 
or  explosion  w. 

By  combustion 
or    explosion 

Absorption  w. 
Br  water  or 

As  C2Hi,  which 
see. 

Ob, 

w.  O2. 

H2S207 

Solubility  20°  C., 

1  cc:  water  ab- 

absorbs  cc.  . 

0.0182 

0.035 

0.15 

1.03 

Nitrous  oxide. 

Carbon  oxy  sulphide. 

Nitrogen. 

The  noble  gases. 

1.523 

2.074 

0.970 

Helium,  Neon, 
Argon,  Krypton, 
Xenon. 

None. 
By  explosion  with  H2 
or  combustion  w. 
CuO. 

None. 
Alcoholic  KOH  1  :  3 
in  66%  alcohol  by 
weight. 

None. 
By    absorption    or 
combustion  of  all 
other   gases   and 
measuring      the 
residue  which  also 
contains  the  noble 

gases. 

0.670 

0.3 

0.014 

GAS  ANALYSIS 


697 


NOTES.  GROUP!:  NaBrO  is  made  by  saturating  a  10%  solution  of  caustic  soda 
with  bromine. 

GROUP  II:  Chlorine  can  be  removed  from  hydrochloric  acid  by  passing  the 
gases  over  finely  powdered  antimony:  hydrochloric  acid  can  be  removed  from  chlorine 
by  means  of  manganese  dioxide  or  zinc  oxide. 

The  following  reactions  will  serve  to  discriminate  between  HCN  and  (CN)2: 

(CN)2+2H2O  +  (HC1)  =2CO(NH2)2  +  (HC1)  oxamide. 

HCN+2H2O  +  (HC1)=HCOOH+NH3  +  (HC1)  formic  acid. 

Cyanogen  is  not  absorbed  by  acid  silver  nitrate  solution,  from  which  it  can  be 
separated  by  drawing  air  through  it:  hydrocyanic  acid  is  precipitated  under  these 
conditions. 

GROUP  IV :  Ozone  can  be  determined  by  Wurster's  1  method,  consisting  in  pass- 
ing the  gas  over  paper  moistened  with  fresh  para  phenylene  diamine 2  and  comparing 
the  depth  of  color  produced  with  a  standard  paper.  In  large  quantities  it  can  be 
determined  according  to  Treadwell  and  Anneler 3  by  passing  through  standard  neutral 
potassium  iodide  and  titration  of  the  liberated  iodine  with  N/10  sodium  thiosulphate. 


Analysis  of  Gaseous  Mixtures 

The  analysis  of  a  gaseous  mixture  is  effected  by  absorbing  the  various  con- 
stituents and  observing  the  diminution  in  volume :  in  case  the  gas  be  unabsorbable, 
as  for  example  methane  (CH4),  it  is 
burned  and  the  carbon  dioxide  and 
water  determined. 

(a)  Analysis  of  mixtures  for  carbon 
dioxide,   oxygen    and    carbon   monoxide 
(e.g.  chimney  gases,  producer  and  blast 
furnace  gas)  can  be  done  with  any  of 
the  apparatus  to  be  described.     The 
Orsat,  or  Elliott  are  the  forms  usually 
employed. 

(b)  Analysis  of  mixtures   as  in  (a) 
and  also  containing  combustible  gases  as 
hydrogen  and  methane,  e.g.,  illuminating 
gas. 

The  Orsat  Apparatus.  Descrip- 
tion. The  apparatus,  Fig.  120,  is  en- 
closed in  a  case  to  permit  of  transpor- 
tation from  place  to  place;  furthermore, 
the  measuring-tube  is  jacketed  with 
water  to  prevent  changes  of  tempera- 
ture affecting  the  gas-volume.  The 
apparatus  consists  essentially  of  the 
leveling-bottle  A,  the  burette  B,  the 
pipettes  P',  P",  P'",  and  the  connecting  tube  T.  Pipette  P'  is  filled  with 
potassium  (or  sodium)  hydroxide  solution  (see  Reagents)  so  that  when  it  is 
drawn  up  into  the  front  arm  about  half  an  inch  in  depth  is  left  in  the  rear  arm. 
Pipettes  P"  and  P'"  are  similarly  filled  with  potassium  (or  sodium)  pyrogallate 
and  cuprous  chloride  solutions  respectively.  These  reagents  require  to  be  pro- 

1  Berichte,  20,  921  (1888). 

2  Obtainable  from  Schuchardt,  Gorlitz/ 

3  Tread  well-Hall,  "  Quantitative  Analysis,  "j 


FIG.  120. 


698  GAS  ANALYSIS 

tected  from  the  oxygen  of  the  air  by  collapsible  rubber  bags.  As  the  oxygen  in 
the  air  over  the  reagent  is  absorbed,  a  diminution  in  pressure  takes  place  rendering 
it  difficult  to  bring  the  reagent  to  the  point  on  the  stem:  the  obvious  remedy  is 
to  remove  the  bag  temporarily  and  adjust  the  reagent.  When  the  apparatus  is 
is  first  set  up,  one  or  two  blank  analyses  should  be  made,  to  saturate  the  water 
and  reagents  with  the  gases.  For  example  the  potassium  hydroxide  absorbs  carbon 
dioxide,  it  also  absorbs  about  3  cc.  of  oxygen,  2  cc.  of  carbon  monoxide  and  1.5 
cc.  of  nitrogen,  by  virtue  of  the  100  cc.  of  water  which  it  contains.  A  change  of 
temperature  of  1°  makes  a  change  of  0.36%  of  the  volume  of  the  gas:  a  change 
of  pressure  of  1  mm.  produces  0.13%  change  in  the  volume. 

Manipulation.  The  reagents  in  the  pipettes  should  be  adjusted  in  the  capil- 
lary tubes  to  a  point  on  the  stem  about  midway  between  the  top  of  the  pipette 
and  the  rubber  connector.  This  is  effected  by  opening  wide  the  pinchcock  upon 
the  connector,  the  bottle  being  on  the  table,  and  very  gradually  lowering  the 
bottle  until  the  reagent  is  brought  to  the  point  above  indicated.  Six  inches  of 
the  tubing  used  correspond  to  but  0.1  cc.,  so  that  an  error  of  half  an  inch  in  adjust- 
ment of  the  reagent  is  without  influence  upon  the  accuracy  of  the  result.  The 
reagents  having  been  thus  adjusted,  the  burette  and  connecting  tube  are  com- 
pletely filled  with  water  by  opening  d  and  raising  the  leveling-bottle.  The 
apparatus  is  now  ready  to  receive  a  sample  of  gas  (or  air  for  practice).  In  case  a 
flue-gas  is  to  be  analyzed  d  is  connected  with  i,  Fig.  112,  A  lowered  and  about  102  cc. 
of  the  gas  forced  over  by  opening  h;  or  d  may  be  connected  with  a  T- joint  in  the 
gas-stream;  the  burette  after  filling  is  allowed  to  drain  one  minute  by  the  sand- 
glass, c  snapped  upon  its  rubber  tube,  and  the  bottle  A  raise  d  to  the  top  of  the 
apparatus.  By  gradually  opening  c  the  water  is  allowed  to  run  into  the  burette 
until  the  lower  meniscus  stands  upon  the  100  or  0  mark  (according  to  the  gradu- 
ation of  the  apparatus).  The  gas  taken  is  thus  compressed  into  the  space  occupied 
by  100  cc.,  and  by  opening  d  the  excess  escapes.  Open  c  and  bring  the  level  of  the 
water  in  the  bottle  to  the  same  level  as  the  water  in  the  burette  and  take  the  reading, 
which  should  be  100  cc.  Special  attention  is  called  to  this  method  of  reading: 
if  the  bottle  be  raised,  the  gas  is  compressed;  if  lowered,  it  is  expanded. 

Determination  of  Carbon  Dioxide.  The  gas  to  be  analyzed  is  invariably 
passed  first  into  pipette  P',  containing  potassium  hydroxide  for  the  absorption  of 
carbon  dioxide,  by  opening  e  and  raising  A.  The  gas  displaces  the  reagent  in  the 
front  part  of  the  pipette,  laying  bare  the  tubes  contained  in  it,  which  being  covered 
with  the  reagent  present  a  large  absorptive  surface  to  the  gas;  the  reagent  moves 
into  the  rear  arm  of  the  pipette,  displacing  the  air  over  it  into  the  flexible  rubber 
bag  which  prevents  its  diffusion  into  the  air.  The  gas  is  forced  in  and  out  of  the 
pipette  by  raising  and  lowering  A,  the  reagent  finally  brought  approximately  to 
its  initial  point  on  the  stem  of  the  pipette,  the  burette  allowed  to  drain  one  minute, 
and  the  reading  taken.  The  difference  between  this  and  the  initial  reading 
represents  the  cubic  centimeters  of  carbon  dioxide  present  in  the  gas.  To  be 
certain  that  all  the  carbon  dioxide  is  removed,  the  gas  should  be  passed  a  second 
time  into  Pr  and  the  reading  taken  as  before;  these  readings  should  agree  within 
0.1%. 

Determination  of  Oxygen.  The  residue  from  the  absorption  of  carbon 
dioxide  is  passed  into  the  second  pipette,  P",  containing  an  alkaline  solution  of 
potassium  pyrogallate,  until  no  further  absorption  will  take  place.  The  difference 
between  the  reading  obtained  and  that  after  the  absorption  of  carbon  dioxide, 
represents  the  number  of  cubic  centimeters  of  oxygen  present. 


GAS   ANALYSIS  699 

Determination  of  Carbon  Monoxide.  The  residue  from  the  absorption  of 
oxygen  is  passed  into  the  third  pipette,  P'",  containing  cuprous  chloride,  until  no 
further  absorption  takes  place;  that  is,  in  this  case  until  readings  agreeing  exactly 
(not  merely  to  0.1)  are  obtained.  The  difference  between  the  reading  thus  obtained 
and  that  after  the  absorption  of  oxygen,  represents  the  number  of  cubic  centi- 
meters of  carbonic  oxide  present. 

Determination  of  Hydrocarbons.  The  residue  left  after  all  absorptions  have 
been  made  may  consist,  in  addition,  to  nitrogen,  the  principal  constituent,  of  hydro- 
carbons and  hydrogen. 

Accuracy.  The  apparatus  gives  results  accurate  to  0.2  of  1%,  hence  figures 
obtained  by  division  to  0.01  should  not  be  reported. 

Time  Required.  About  twenty  minutes  are  required  for  an  analysis;  two 
may  be  made  in  twenty-five  minutes,  using  two  apparatus. 

NOTES.  The  method  of  adjusting  the  reagents  is  the  only  one  which  has 
been  found  satisfactory:  if  the  bottle  be  placed  at  a  lower  level  and  an  attempt 
made  to  shut  the  pinchcock  c  upon  the  connector  at  the  proper  time,  it  will  almost 
invariably  result  in  failure. 

The  process  of  obtaining  100  cc.  of  gas  is  exactly  analogous  to  filling  a  measure 
heaping  full  of  grain  and  striking  off  the  excess  with  a  straightedge;  it  saves 
arithmetical  work,  as  cubic  centimeters  read  off  represent  per  cent  directly. 

It  often  happens  when  e  is  opened,  c  being  closed,  that  the  reagent  P'  drops, 
due  not  to  a  leak,  as  is  usually  supposed,  but  to  the  weight  of  the  column  of  the 
reagent  expanding  the  gas. 

The  object  of  the  rubber  bags  is  to  prevent  the  access  of  air  to  the  reagents, 
those  in  P"  and  P'"  absorbing  oxygen  with  great  avidity,  and  hence  if  freely  exposed 
to  the  air  would  soon  become  useless. 

Carbon  dioxide  is  always  the  first  gas  to  be  removed  from  a  gaseous  mixture. 
In  the  case  of  air  the  percentage  present  is  so  small,  0.08  to  0.1,  as  scarcely  to  be 
seen  with  this  apparatus.  It  is  important  to  use  the  reagents  in  the  order  given; 
if  by  mistake  the  gas  be  passed  into  the  second  pipette,  it  will  absorb  not  only 
oxygen,  for  which  it  is  intended,  but  also  carbon  dioxide;  similarly  if  the  gas  be 
passed  into  the  third  pipette,  it  will  absorb  not  only  carbonic  oxide,  but  also 
oxygen  as  well. 

The  use  of  pinchcocks  and  rubber  tubes,  original  with  the  author,  although 
recommended  by  Naef,  is  considered  by  Fischer  to  be  inaccurate.  The  experi- 
ence of  the  author,  however,  does  not  support  this  assertion,  as  they  have 
been  found  to  be  fully  as  accurate  as  glass  stopcocks,  and  very  much  less  trouble- 
some and  expensive. 

In  case  any  potassium  hydroxide  or  pyrogallate  be  sucked  over  into  the  tube  T 
or  water  in  A,  the  analysis  is  not  spoiled,  but  may  be  proceeded  with  by  connecting 
on  water  at  d,  opening  this  cock,  and  allowing  the  water  to  wash  the  tubes  out 
thoroughly.  The  addition  of  a  little  hydrochloric  acid  to  the  water  in  the  bottle 
A  will  neutralize  the  hydroxide  or  pyrogallate,  and  the  washing  may  be  postponed 
until  convenient. 

After  each  analysis  the  number  of  cubic  centimeters  of  oxygen  and  carbonic 
oxide  should  be  set  down  upon  the  ground-glass  slip  provided  for  the  purpose. 
By  adding  these  numbers  and  subtracting  their  sum  from  the  absorption 
capacity  (see  Reagents)  of  each  reagent,  the  condition  of  the  apparatus  is 
known  at  any  time,  and  the  reagent  can  be  renewed  in  season  to  prevent  incor- 
rect analyses. 


700 


GAS  ANALYSIS 


Elliott  Apparatus.  Description.  The  apparatus  Fig.  121  consists  of  a  burette 
holding  100  cc.  graduated  in  tenths  of  a  cubic  centimeter  and  bulbed  like  the 
Bunte  apparatus — the  bulb  holding  about  30  cc.;  it  is  connected  with  a  leveling- 
bottle  similar  to  the  Orsat  apparatus.  The  top  of  the  burette  ends  in  a  capillary 
stopcock,  the  stem  of  which  is  ground  square  to  admit  of 
close  connection  with  the  "  laboratory  vessel/'  an  ungradu- 
ated  tube  similar  to  the  burette,  except  of  125  cc.  capacity. 
The  top  of  this  "  vessel  "  is  also  closed  with  a  capillary  stop- 
cock, carrying  by  a  ground-glass  joint,  or  better  a  rubber  stop- 
per, a  thistle-tube  F,  for  the  introduction  of  the  reagents. 
The  lower  end  of  this  "  vessel  "  is  closed  by  a  rubber  stop- 
per carrying  a  three-way  cock  o,  and  connected  with  a  level- 
ing bottle  D.  The  burette  and  vessel  are  held  upon  a  block 
of  wood — supported  by  a  ring  stand — by  fine  copper  wire 
tightened  by  violin  keys. 

Manipulation.  The  ground-glass  joints  are  lubricated 
with  stopcock  grease,  p.  725.  The  leveling-bottles  are  filled 
with  water,  the  stopcocks  opened,  and  the  bottles  raised  until 
the  water  flows  through  the  stopcocks  m  and  n.  m  is  con- 
nected with  the  source  whence  the  gas  to  be  analyzed  is  to 
be  taken,  n  is  closed,  D  lowered  and  rather  more  than  100  cc. 
drawn  in,  and  m  closed,  n  is  opened,  D  raised  and  E  low- 
ered, nearly  100  cc.  of  gas  introduced,  and  n  closed;  by  open- 
ing m  and  raising  D  the  remainder  of  the  gas  is  allowed  to 
escape,  the  tubes  being  filled  with  water  and  m  closed,  n  is 
opened  and  the  water  brought  to  the  reference  mark;  the 
burette  is  allowed  to  drain  one  minute,  the  level  of  the  water 
in  E  is  brought  to  the  same  level  as  in  the  burette,  and  the 
reading  taken. 

Determination  of  Carbon  Dioxide.  By  raising  E,  open- 
ing n,  and  lowering  D,  the  gas  is  passed  over  into  the  labora- 
tory vessel;  F  is  filled  within  half  an  inch  of  the  top  with 
potassium  hydroxide,  o  closed,  m  opened,  and  the  reagent 
allowed  slowly  to  trickle  in.  A  No.  3  evaporating  dish  is 
placed  under  o,  and  this  turned  to  allow  the  liquid  in  the 
laboratory  vessel  to  run  into  the  dish.  At  first  this  is  mainly 
water,  and  may  be  thrown  away;  later  it  becomes  diluted 
reagent  and  may  be  returned  to  the  thistle-tube.  When  the 
depth  of  the  reagent  in  the  thistle-tube  has  lowered  to  half  an 
inch,  it  should  be  refilled  either  with  fresh  or  the  diluted  reagent  and  allowed  to 
run  in  until  the  absorption  is  judged  to  be  complete,  and  the  gas  passed  back 
into  the  burette  for  measurement.  To  this  end  close  o  and  then  m,  raise  E, 
open  n,  and  force  some  pure  water  into  the  laboratory  vessel,  thus  rinsing  out 
the  capillary  tube.  Now  raise  D  and  lower  E,  shutting  n  when  the  liquid  has 
arrived  at  the  reference-mark.  The  burette  is  allowed  to  drain  a  minute,  the 
level  of  the  water  in  the  bottle  E  brought  to  the  same  level  as  the  water  in  the 
burette,  and  the  reading  taken. 

Determination  of  Oxygen.  The  manipulation  is  the  same  as  in  the  pre- 
ceding determination,  potassium  pyrogallate  being  substituted  for  potassium 
hydrate;  the  apparatus  requiring  no  washing  out. 


FIG.  121 


GAS  ANALYSIS  701 

Determination  of  Carbonic  Oxide.  The  laboratory  vessel,  thistle-tube,  and 
bottle  if  necessary,  are  washed  free  from  potassium  pyrogallate  and  the  absorption 
made  with  acid  cuprous  chloride  similarly  to  the  determination  of  carbon  dioxide. 
The  white  precipitate  of  cuprous  chloride  may  be  dissolved  by  hydrochloric  acid. 

Accuracy  and  Time  Required.  The  apparatus  is  as  accurate  for  absorptions 
as  that  of  Orsat ;  it  is  stated  to  be  much  more  rapid — a  claim  which  the  writer 
cannot  substantiate.  It  is  not  as  portable,  is  more  fragile,  and  more  troublesome 
to  manipulate,  and  as  the  burette  is  not  jacketed,  it  is  liable  to  be  affected  by 
changes  of  temperature. 

NOTES.  In  case  at  any  time  it  is  desired  to  stop  the  influx  of  reagent,  o  should  be 
closed  first  and  then  m;  the  reason  being  that  the  absorption  may  be  so  rapid  as  to 
suck  air  in  through  o,  m  being  closed. 

The  stopcock  should  be  so  adjusted  as  to  cause  the  reagent  to  spread  itself  as  com- 
pletely as  possible  over  the  sides  of  the  burette. 

By  the  addition  of  an  explosion  tube  it  is  used  for  the  analysis  of  illuminating  gas,1 
bromine  being  used  to  absorb  the  "  illuminants,"  Winkler  2  states  that  this  absorption 
is  incomplete;  later  work  by  Treadwell  and  Stokes,  and  also  Korbuly,3  has  shown 
that  bromine  water,  by  a  purely  physical  solution,  does  absorb  the  "  illuminants  " 
completely;  Hempel 4  states  that  explosions  of  hydrocarbons  made  over  water  are 
inaccurate,  so  that  the  apparatus  can  be  depended  upon  to  give  results  upon  methane 
and  hydrogen  only  within  about  2%.  It  is,  however,  very  rapid,  a  complete  analysis 
of  illuminating  gas  can  be  made  with  it  in  fifty-five  minutes. 

Hempel's  Apparatus.  Description.  The  apparatus,  Figs.  122  and  123,  is 
very  similar  in  principle  to  that  of  Orsat;  the  burette  is  longer,  admitting  of  the 
reading  of  small  quantities  of  gas,  and  the  pipettes  are  separate  and  mounted  in 
brass  clamps  on  iron  stands.  P  shows  a  "  simple  "  pipette  5  provided  with  a 
rubber  bag;  this  form,  after  twenty-five  years  of  use,  can  be  said  satisfactorily  to 
take  the  place  of  the  cumbersome  "  compound  "  pipette. 

The  pipette  for  fuming  sulphuric  acid 6  is  shown  at  F,  and  differs  from  the 
ordinary  in  that  vertical  tubes  after  the  manner  of  those  in  the  Orsat  pipettes 
replace  the  usual  glass  beads.  This  prevents  the  trapping  of  any  gas  by  the 
filling,  which  was  so  common  with  the  beads  and  glass  wool.  E  represents  the 
large  explosion  pipette,7  of  about  250-cc.  capacity,  with  walls  half  an  inch  thick; 
the  explosion  wires  enter  at  the  top  and  bottom  to  prevent  short-circuiting; 
mercury  is  the  confining  liquid.  The  small  explosion  pipette  holds  about  110  cc. 
and  is  of  glass,  the  same  thickness  as  the  simple  pipettes.  Water  is  here  used  as 
the  confining  liquid,  and  also  usually  in  the  burette. 

An  induction  coil  capable  of  giving  a  half-inch  spark,  with  six  dry  cells,  four 
"  simple  "  pipettes  and  a  mercury  burette,  complete  the  outfit. 

The  burette  should  be  carefully  calibrated  and  the  corrections  may  very  well 
be  etched  upon  it  opposite  the  10-cc.  divisions. 

In  working  with  the  apparatus  the  pipettes  are  placed  upon  the  adjustable 
stand  S  and  connection  made  with  the  doubly  bent  capillary  tube. 

Manipulation.  To  acquire  facility  with  the  use  of  the  apparatus  before 
proceeding  to  the  analysis  of  illuminating  gas,  it  is  well  to  make  the  following 

1  Mackintosh,  Am.  Chem.  Jour.,  9,  294. 

2  Zeit.  f .  Anal.  Chem.,  28,  286. 

8  Treadwell-HalTs  "  Quantitative  Analysis/'  p.  569. 
4  "  Gasanalytische  Methoden,"  p.  102. 
*  Gill,  Am.  Chem.  J.,  14,  231,  1892. 

6  Ibid.,  J.  Am.  Chem.  Soc.,  18,  67,  1896. 

7  Gill,  J.  Am.  Chem.  Soc.,  17,  771,  1895. 


702 


GAS  ANALYSIS 


determinations,  obtaining  "  check-readings  "  in  every  case:  I.  Oxygen  in  air,  by 
(1)  absorption  with  phosphorus;  (2)  absorption  with  potassium  (or  sodium) 
pyrogallate;1  (3)  by  explosion  with  hydrogen. 

I.  DETERMINATION  OF  OXYGEN  IN  AIR 

(1)  By  Phosphorus.  100  cc.  of  air  are  measured  out  as  with  the  Orsat  appa- 
ratus, the  burette  being  allowed  to  drain  two  minutes.  The  rubber  connectors 
upon  the  burette  and  pipette  are  filled  with  water,  the  capillary  tube  inserted,  as 
far  as  it  will  go,  by  a  twisting  motion,  into  the  connector  upon  the  burette,  thus 
filling  the  capillary  with  water;  the  free  end  of  the  capillary  is  inserted  into  the 


FIG.  122. 

pipette  connector,  the  latter  pinched  so  as  to  form  a  channel  for  the  water  con- 
tained in  it  to  escape,  and  the  capillary  twisted  and  forced  down  to  the  pinchcock. 
There  should  be  as  little  free  space  as  possible  between  the  capillaries  and  the  pinch- 
cock.  Before  using  a  pipette,  its  connector  (and  rubber  bag)  should  be  carefully 
examined  for  leaks,  especially  in  the  former,  and  if  any  found  the  faulty  piece 
replaced. 

The  pinchcock  on  the  burette  and  pipette  are  now  opened,  the  ah-  forced  over 
into  the  phosphorus,  and  the  pinchcock  on  the  pipette  closed;  action  immediately 

1  The  writer  finds  after  an  experience  of  more  than  twenty-five  years  in  the  lab- 
oratory with  hundreds  of  students,  that  sodium  pyrogallate  can  be  used  with  practically 
the  same  results  as  the  potassium  compound.  The  absorption  is  complete,  as  shown 
by  subsequent  treatment  with  cuprous  chloride. 


GAS  ANALYSIS 


703 


ensues,  shown  by  the  white  fumes;  after  allowing  it  to  stand  fifteen  minutes  the 
residue  is  drawn  back  into  the  burette,  the  latter  allowed  to  drain  and  the  reading 
taken.  The  absorption  goes  on  best  at  20°  C.,  not  at  all  below  15°  C.;  it  is 
very  muclj  retarded  by  small  amounts  of  ethane  and  ammonia.  It  cannot  be 
used  to  absorb  commercial  oxygen.  No  cognizance  need  be  taken  of  the  fog  of 
oxides  of  phosphorus. 

(2)  By  Pyrogallate  of  Potassium.  100  cc.  of  air1  are  measured  out  as  before, 
the  carbon  dioxide  absorbed  with  potassium  hydrate  and  the  oxygen  with  potassium 
pyrogallate,  as  with  the  Orsat  apparatus;  before  setting  aside  the  pyrogallate 
pipette,  the  number  of  cubic  centimeters  of  oxygen  absorbed  should  be  noted  upon 
the  slate  s  on  the  stand.  This  must  never  be  omitted  with  any  pipette  save  pos- 


FIQ.  123. 


sibly  that  for  potassium  hydroxide,  as  failure  to  do  this  may  result  in  the  ruin  of 
an  important  analysis.  The  reason  for  the  omission  in  this  case  is  found  in  the 
large  absorption  capacity — four  to  five  liters  of  carbon  dioxide — of  the  reagent. 
(3)  By  Explosion  with  Hydrogen.  Forty-three  cc.  of  air  and  57  cc.  of 
hydrogen  are  measured  out,  passed  into  the  small  explosion  pipette,  the  capillary 
of  the  pipette  filled  with  water,  the  pinchcocks  and  glass  stopcock  all  closed,  a 
heavy  glass  or  fine  wire  gauze  screen  placed  between  the  pipette  and  the  operator, 
the  spark  passed  between  the  spark  wires,  and  the  contraction  in  volume  noted. 
The  screen  should  never  be  omitted,  as  serious  accidents  may  occur  thereby.  The 
oxygen  is  represented  by  one-third  of  the  contraction.  For  very  accurate  work 
the  sum  of  the  combustible  gases  should  be  but  one-sixth  that  of  the  non-com- 
bustible gases,  otherwise  some  nitrogen  will  burn  and  high  results  will  be  obtained;2 
that  is,  (H+0)  :  (N+H)  ::1  :  6. 

1  See  Anderson's  work,  J.  Ind.  and  Chem.,  7,  587,  1915. 

a  This  is  shown  in  the  work  of  Gill  and  Hunt,  J.  Am.  Chem.  Soc.,  17,  987,  1895. 


704  GAS   ANALYSIS 

H.  ANALYSIS  OF  ILLUMINATING  GAS 

One  hundred  cc.  of  gas  are  measured  from  the  bottle  containing  the  L  uple 
into  the  burette. 

Determination  of  Carbon  Dioxide.  The  burette  is  connected  with  the 
pipette  containing  potassium  hydroxide  and  the  gas  passed  into  it  with  shaking 
until  no  further  diminution  in  volume  takes  place. 

Illuminants,  CnH2n,  CnH2n_6  Series. — The  rubber  connectors  are  carefully  dried 
out  with  filter-paper,  a  dry  capillary  used,  and  the  gas  passed  into  the  pipette 
containing  fuming  sulphuric  acid  and  allowed  to  stand,  with  occasional  passes 
to  and  fro,  for  forty-five  minutes.  On  account  of  the  extremely  corrosive  nature 
of  the  absorbent  it  is  not  advisable  to  shake  the  pipette,  as  in  case  of  breakage 
a  serious  accident  might  occur.  For  water  gas  this  is  sufficient,  although  in  case 
of  doubt  or  with  richer  gases  check  readings  to  0.2  cc.  should  be  obtained.  It  is 
then  passed  into  potassium  hydroxide,  as  in  the  previous  determination,  to  remove 
any  sulphurous  acid  which  may  have  been  formed  and  any  sulphuric  anhydride 
vapor,  these  having  a  higher  vapor  tension  than  water.  The  difference  between 
this  last  reading  and  that  after  the  absorption  of  the  carbon  dioxide  represents 
the  volume  of  "  illuminants  "  or  "  heavy  hydrocarbons  "  present. 

As  has  already  been  stated,  page  701,  saturated  bromine  water  may  replace 
the  fuming  sulphuric  acid.  Fuming  nitric  acid  is  not  recommended,  as  it  is  liable 
to  oxidize  carbonic  oxide. 

Oxygen.  This  is  absorbed,  as  in  the  analysis  of  air,  by  potassium  or  sodium 
pyrogallate. 

Carbonic  Oxide.  The  gas  is  now  passed  into  ammoniacal  cuprous  chloride, 
until  the  reading  is  constant  to  0.2  cc.;  it  is  then  passed  into  a  second  pipette, 
which  is  fresh,  and  absorption  continued  until  constant  readings  are  obtained. 
The  second  pipette  should  not  have  absorbed  more  than  10  cc.  of  CO. 

Gautier  and  Clausmann1  have  shown  that  some  carbonic  oxide  escapes  solution 
in  cuprous  chloride,  so  that  for  very  accurate  work  it  may  be  necessary  to  pass 
the  gas  through  a  U-tube  containing  iodic  anhydride  heated  to  70°  C. 

This  is  done  by  interposing  this  tube  between  the  burette  and  a  simple  pipette 
filled  with  potassium  hydrate.  The  reaction  is  5CO+I206  =5C02+2I.  The  dimi- 
nution in  volume  represents  directly  the  volume  of  carbonic  oxide  present. 

The  volume  of  air  contained  in  the  tube  should  be  corrected  for  as  follows: 
One  end  of  the  tube  is  plugged  tightly  and  the  other  end  connected  with  the  gas 
burette  partly  filled  with  air.  A  bath  of  water  at  9°  C.  is  placed  around  the 
U-tube  and  the  reading  of  the  air  in  the  gas  burette  recorded  when  constant; 
the  bath  is  now  heated  to  100°  and  the  burette  reading  again  recorded  when 
constant.  The  increase  in  reading  represents  one-third  the  volume  of  the  U-tube, 
273  :273+(100-9)  ::3  :  4. 

Methane  and  Hydrogen,  (a)  Hinman's  Method.2  The  gas  left  from  the 
absorption  of  carbonic  oxide  is  passed  into  the  large  explosion  pipette.  About 
half  the  requisite  quantity  of  oxygen  (40  cc.)  necessary  to  burn  the  gas  is  now 
added,  mercury  introduced  through  the  T  in  the  connector  sufficient  to  seal  the 
capillary  of  the  explosion  pipette,  all  rubber  connectors  carefully  wired,  the  pinch- 
cocks  closed,  and  the  pipette  cautiously  shaken.  A  screen  of  heavy  glass  or  fine 
wire  gauze  is  interposed  between  the  operator  and  the  apparatus,  the  explosion 

1  Bull.  Soc.  Chem.,  35,  513;  Abstr.  Analyst,  31,  349,  1906. 
8  GUI  and  Hunt,  J.  Am.  Chem.  Soc.,  17,  987,  1895. 


GAS  ANALYSIS  705 

wires  are  connected  with  the  induction  coil,  a  spark  passed  between  them  and  the 
pinchcocks  opened,  sucking  in  the  remainder  of  the  oxygen.  The  capillary  is 
again  sealed  with  mercury,  the  stopcock  opened  and  closed,  to  bring  the  contents 
of  the  pipette  to  atmospheric  pressure,  and  the  explosion  repeated  as  before,  and 
the  stopcock  opened. 

It  may  be  found  expedient  to  increase  the  inflammability  of  the  mixture, 
to  introduce  5  cc.  of  "  detonating  gas/'  the  hydrolytic  mixture  of  hydrogen  and 
oxygen.  The  gas  in  the  pipette  containing  carbon  dioxide,  oxygen,  and  nitrogen 
is  transferred  to  the  mercury  burette  and  accurately  measured.  The  carbon 
dioxide  resulting  from  the  combustion  of  the  marsh  gas  is  determined  by  absorption 
hi  potassium  hydroxide;  to  show  the  presence  of  an  excess  of  oxygen,  the  amount 
remaining  is  determined  by  absorption  with  potassium  pyrogallate. 

The  calculation  is  given  on  page  706.  For  very  accurate  work  a  second  analysis 
should  be  made,  making  successive  explosions,  using  the  percentages  of  methane 
and  hydrogen  just  found  as  a  basis  upon  which  to  calculate  the  quantity  of  oxygen 
to  be  added  each  time.  The  explosive  mixture  should  be  so  proportioned  that 
the  ratio  of  combustible  gas  (i.e.,  CH4,  H  and  0)  is  to  the  gases  which  do  not 
burn  (i.e.,  N  and  the  excess  of  CH4  and  H)  as  100  is  to  about  50  (from  26  to  64)  j1 
otherwise  the  heat  developed  is  so  great  as  to  produce  oxides  of  nitrogen,  which, 
being  absorbed  in  the  potassium  hydroxide,  would  affect  the  determination  of  both 
the  methane  and  the  hydrogen.  The  oxygen  should  preferably  be  pure,  although 
commercial  oxygen,  the  purity  of  which  is  known,  can  be  used;  the  oxygen 
content  of  the  latter  should  be  tested  from  time  to  time,  especially  with  different 
samples. 

(6)  Hempel's  Method.2  From  12  to  15  cc.  of  the  gas  are  measured  off  into  the 
burette  (e.g.,  13.2  cc.)  and  the  residue  is  passed  into  the  cuprous  chloride  pipette 
for  safe  keeping.  That  in  the  burette  is  now  passed  into  the  small  explosion 
pipette;  a  volume  of  air  more  than  sufficient  to  burn  the  gas,  usually  about  85  cc., 
is  accurately  measured  and  also  passed  into  the  explosion  pipette,  and  in  so  doing 
water  from  the  burette  is  allowed  partially  to  fill  the  capillary  of  the  pipette  and 
act  as  a  seal.  The  rubber  connectors  upon  the  capillaries  of  the  burette  and 
pipette  are  carefully  wired  on,  both  pinchcocks  shut,  and  the  stopcock  closed. 
The  pipette  is  cautiously  shaken,  the  screen  interposed,  the  explosion  wires  con- 
nected with  the  induction  coil,  a  spark  passed  between  them,  and  the  stopcock 
immediately  opened.  The  gas  in  the  pipette,  containing  carbon  dioxide,  oxygen, 
and  nitrogen,  is  transferred  to  the  burette,  accurately  measured,  by  reading 
immediately,  to  prevent  the  absorption  of  carbon  dioxide,  and  carbon  dioxide 
and  oxygen  determined  in  the  usual  way. 

Calculation,  (a)  Hinman's  Method.  56.2  cc.  of  gas  remained  after  the 
absorption;  77.4  cc.  of  oxygen  were  introduced,  giving  a  total  volume  of  133.6  cc. 

Residue  after  explosion 46 . 9  cc. 

Residue  after  C02  absorption 28 . 2 

Carbon  dioxide  formed 18.7 

Contraction 133. 6-46. 9  *=  86.7 

Residue  after  O  absorption 25 . 6 

Oxygen  in  excess 28.2-25.6=     2.6 

1  Bunsen,  "  Gasometrische  Methoden,"  2d  ed.,  73,  1877. 
aHempel,  "  Gas  Analytische  Methoden,"  3d  ed.,  245,  1901. 


706 


GAS   ANALYSIS 


The  explosion  of  marsh  gas  or  methane  is  represented  by  the  equation 

+ 

From  this  it  is  evident  that  the  volume  of  carbon  dioxide  is  equal  to  the  volume 
of  methane  present;  therefore  in  the  above  example,  in  the  56.2  cc.  of  gas  burned, 
there  were  18.7  cc.  methane. 

The  total  contraction  is  due  (1)  to  the  disappearance  of  oxygen  in  combining 
with  the  hydrogen  of  the  methane,  and  (2)  to  the  union  of  the  free  hydrogen  with 
oxygen.  The  volume  of  the  methane  having  been  found,  (1)  can  be  ascertained 
from  the  equation  above,  equals  twice  the  volume  of  the  methane;  hence 

86.7-(2Xl8.7)=49.3cc., 

contraction  which  is  due  to  the  combustion  of  hydrogen.  This  takes  place 
according  to  the  following  reaction:1 


H20 


Hydrogen  then  requires  for  its  combustion  half  its  volume  of  oxygen,  hence 
this  49.3  cc.  represents  a  volume  of  hydrogen  with  |  its  volume  of  oxygen,  or  f 
volumes;  hence  the  volume  of  hydrogen  is  32.9  cc. 

(6)  HempeUs  Method.  Of  the  82  cc.  of  gat  remaining  after  the  absorptions,  13.2 
cc.  were  used  for  the  explosion;  86.4  cc.  air  introduced,  giving  a  total  volume  of  99.6  cc. 

Residue  after  explosion 78 .0  cc. 

Residue  after  C02  absorption 73.2 

Carbon  dioxide  formed 4.8 

Contraction 99.6-78.0=  21.6 

Residue  after  O  absorption 70 . 2 

Oxygen  in  excess 73.2-70.2  =  3.0 

The  carbon  dioxide  being  equal  to  the  methane  present,  in  the  13.2  cc.  of  gas 
burned  there  were  4.8  cc.  of  methane.  The  volume  of  methane  is  found  by  the 
proportion  13.2  :  82  ::4.8  :  x,  whence  2  =29.8  cc. 

The  hydrogen  is  calculated  similarly. 

Another  method  for  the  estimation  of  hydrogen  is  by  absorption  with  palladium 
sponge;2  it,  however,  must  be  carefully  prepared,  and  it  is  the  author's  experience 
that  one  cannot  be  sure  of  its  efficacy  when  it  is  desired  to  make  use  of  it.  A 
still  better  absorbent  of  hydrogen 3  is  a  1%  solution  of  palladous  chloride  at  50°  C.; 
when  fresh  this  will  absorb  20-50  cc.  of  hydrogen  in  ninety  minutes.  A  pro- 
portionately longer  time  is  required  if  more  hydrogen  be  present  or  the  solution 
nearly  saturated.  The  methane  could  then  be  determined  by  explosion  or  by 
mixing  with  air  and  passing  to  and  fro  over  a  white-hot  platinum  spiral  in 
tubulated  pipette  called  the  grisoumeter 4  (grisou  =  methane). 

Nitrogen.    There  being  no  direct  and  convenient  method  for  its  estimation 
with  this  apparatus,  the  percentage  is  obtained  by  finding  the  difference  betwt 
the  sum  of  all  percentages  of  the  gases  determined  and  100%. 

1  H2O  being  as  steam  at  100°  C.     At  ordinary  temperatures  this  is  condei 
giving  rise  to     total  contraction." 

*  Hempel,  Berichte,  12,  636  and  1006,  1879. 

«  Campbell  and  Hart,  Am.  Chem.  J.,  18,  294,  1896. 

«  Winkler,  Fres.  Zeit.,  28,  269  and  288. 


GAS   ANALYSIS  707 

New  1  determined  nitrogen  in  illuminating  gas  directly  after  the  method  of 
Dumas  in  organic  substances;  150  cc.  of  gas  are  used,  the  hydrocarbons  partially 
absorbed  by  fuming  sulphuric  acid  and  the  remainder  burned  in  a  combustion 
tube  with  copper  oxide;  the  carbon  dioxide  is  absorbed  and  the  residual  nitrogen 
collected  and  measured. 

Accuracy  and  Time  Required.  For  the  absorptions  the  apparatus  is  accurate 
to  0.1  cc.;  for  explosions  by  Hinman's  method2  the  methane  can  be  determined 
within  0.2%,  the  hydrogen  within  0.3%;  by  Hempel's  method  within  1%  for  the 
methane  and  7.5%  for  the  hydrogen.  The  time  required  for  the  analysis  of 
illuminating  gas  is  from  three  to  three  and  one-half  hours;  for  air,  from  fifteen  to 
twenty  minutes. 

NOTES.  The  object  in  filling  the  capillaries  of  the  explosion  pipettes  with 
water  or  mercury  before  the  explosion  is  to  prevent  the  bursting  of  the  rubber 
connectors  on  them.  With  mercury  this  is  effected  by  introducing  it  through 
the  T-joint  in  the  connector.  After  testing  for  oxygen  with  the  pyrogallate  a 
small  quantity  of  dilute  acetic  acid  is  sucked  into  the  burette  to  neutralize  any 
alkali  which  by  any  chance  may  have  been  sucked  over  into  it.  The  acid  is  rinsed 
out  with  water  and  this  is  forced  out  by  mercury  before  the  burette  is  used  again. 

The  water  in  the  burette  should  be  saturated  with  the  gas  which  is  to  be  analyzed 
— as  illuminating  gas — before  beginning  an  analysis.  The  reagents  in  the  pipettes 
should  also  be  saturated  with  the  gases  for  which  they  are  not  the  reagent.  For 
example,  the  fuming  sulphuric  acid  should  be  saturated  with  oxygen,  carbon 
monoxide,  methane,  hydrogen,  and  nitrogen;  this  is  effected  by  making  a  blank 
analysis,  using  illuminating  gas. 

The  method  of  analysis  of  the  residue  after  the  absorptions  have  been  made 
by  explosion  is  open  to  two  objections*  1st,  the  danger  of  burning  nitrogen  by 
the  violence  of  the  explosion;  and  2d,  the  danger  of  breakage  of  the  apparatus 
and  possible  injury  to  the  operator.  These  may  be  obviated  by  employing  the 
apparatus  of  Dennis  and  Hopkins,3  which  is  practically  a  grisoumeter  with  mercury 
as  the  confining  liquid;  or  that  of  Jaeger,4  who  burns  the  gases  with  oxygen  in  a 
hard-glass  or  quartz  tube  filled  with  copper  oxide.  By  heating  to  250°  C.  nothing 
but  hydrogen  is  burned;  higher  heating  of  the  residue  burns  the  methane.  Recent 
work  shows  this  procedure  to  be  very  slow  and  not  very  accurate.  Or  the  mix- 
ture of  oxygen  and  combustible  gases,  bearing  in  mind  the  ratio  mentioned  at  the 
bottom  of  page  703,  can  be  passed  to  and  fro  through  Drehschmidt's 5  capillary 
heated  to  a  bright  redness.  This  consists  of  a  platinum  tube  20  cm.  long,  2  mm. 
thick,  1.7  mm.  bore,  filled  with  three  platinum  or  palladium  wires.  The  ends  of 
the  tube  are  soldered  to  capillary  brass  tubes  and  arranged  so  that  these  can  be 
water  cooled.  It  is  inserted  between  the  burette  and  a. simple  pipette,  mercury 
being  the  confining  liquid  in  both  cases.  The  air  contained  in  the  tube  can  be 
determined  as  in  the  case  of  the  tube  containing  iodic  anhydride,  page  704. 

To  the  method  of  explosion  by  the  mixture  of  an  aliquot  part  of  the  residue  with 
air,  method  (6),  there  is  the  objection  that  the  carbon  dioxide  formed  is  measured 
over  water  in  a  moist  burette,  giving  abundant  opportunities  for  its  absorption,  and 
that  the  errors  in  analysis  are  multiplied  by  about  six,  in  the  example  by  fff. 

1  J.  Soc.  Chem.  Ind.,  11,  415,  1802. 

2  Gill  and  Hunt,  loc.  cit. 

3  J.  Am.  Chem.  Soc.,  21,  398,  1899. 

4  J.  Gasbeleuchtung,  41,  764.     Abstr.  J.  Soc.  Chem.  Ind.,  17,  1190,  1898. 

5  Berichte,  21,  3242,  1888. 


708 


GAS   ANALYSIS 


APPLICATIONS  OF  GAS  ANALYSIS  AND  INTERPRETATION 

OF  RESULTS 

It  is  only  within  comparatively  recent  times  that  Gas  Analysis  has  assumed 
any  importance.  The  reasons  are  that  the  substances  with  which  it  deals  are  so 
intangible,  the  apparatus  is  complicated  and  fragile,  and  until  lately,  competition 
has  not  compelled  manufacturers  to  seek  every  possible  source  of  loss. 

Some  of  its  applications  are  to : 

I.  Chimney  and  flue  gases; 
II.  Producer  and  fuel  gases; 

III.  Illuminating  gas; 

IV.  Sulphuric  acid  gases; 
V.  Mine  gases; 

VI.  Electrolytic  gases; 
VII.  Acetylene; 
VIII.  Atmospheric  air. 


I.  CHIMNEY   AND   FLUE    GASES 

Here  the  object  is  to  keep  the  carbonic  acid  (C02)  as  high  as  possible,  and  to 
avoid  the  formation  of  carbon  monoxide :  in  large  plants  every  additional  per  cent 
of  carbonic  acid  means  the  saving  of  tons  of  coal.  Savings  of  20  to  33%  by  the 
use  of  gas  analysis  alone,  have  frequently  come  to  the  writer's  notice.  A  satis- 
factory procedure  is  to  post  in  the  fire-room  the  percentage  of  carbonic  acid 
obtained  by  each  stoker,  and  stimulate  a  rivalry  among  the  men — a  bonus  in  the 
pay  envelope  is  also  effective.  The  determinations  to  be  made  are: 

Analysis  of  Chimney  Gases.  Determination  of  carbon  dioxide,  oxygen, 
carbon  monoxide,  nitrogen,  and  in  some  case  hydrocarbons.  For  this  purpose 
the  Orsat  apparatus  is  widely  employed:  the  hydrocarbons  may  be  determined 
by  the  Hempel  apparatus. 

Usually  a  few  determinations  of  carbonic  acid  will  suffice,  but  for  regular  work 
the  installation  of  some  form  of  registering  carbonic  acid  indicator  should  be 
installed. 

Carbonic  Acid  Indicators.1  These  usually  depend  upon  the  principle  of 
collecting  100  cc.  of  the  gas,  causing  it  to  pass  through  a  suitable  absorber  and 
collecting  the  residue  in  a  bell  which  floats  to  a  greater  or  less  height  according  to 
the  residual  volume.  The  fluctuations  of  this  bell  are  recorded  after  the  usual 
manner  of  self-registering  barometers  or  thermometers:  the  usual  time  for  this 
analysis  and  record  is  five  minutes. 

By  modifying  this  apparatus  slightly,  it  can  be  applied  to  the  determination 
of  any  absorbable  gas  as,  for  example,  sulphurous  acid  or  chlorine.  It  has  been 
adapted  to  carbon  monoxide  absorption,  but  it  is  not  usual  or  easy. 

Haber 2  employs  the  refractive  index  of  gases  to  determine  the  amount  of 
carbonic  acid  in  chimney  gas;  it  gives  results  within  half  of  1%;3  it  has  also  been 

1  These  can  be  obtained  from  the  following:   Combustion  Appliance  Co.,  Chicago; 
Precision  Instrument  Co.,  Detroit;    Uehling  Instrument  Co.,  Passaic. 

2  Z.  Ang.  Chem.,  19,  1418,  1906;  ibid.,  23,  1393,  1910. 
»  Mohr,  ibid.,  25,  1313,  1912. 


GAS  ANALYSIS  709 

applied  to  other  gaseous  mixtures.  The  instrument  is  called  the  Interferometer 
or  Gas  Refractometer  and  is  made  by  Z-eiss  of  Jena. 

The  Determination  of  Temperature.  This  is  done  by  inserting  a  ther- 
mometer, mounted  in  a  metal  tube,  on  the  chimney  side  of  the  gas  sampling  tube. 
These  resemble  those  usod  for  determining  steam  temperatures  or  for  "  running  " 
varnish.  It  should  register  to  360°  and,  under  certain  circumstances,  one  showing 
550°  may  be  desirable.  A  chemical  thermometer  with  long  stem  may  also  be 
employed;  it  should  never  be  inserted  naked  into  the  flue  —  as  a  sudden  hot  blast 
may  break  it  —  but  always  in  a  tube  of  cotton-seed  oil  or  sea  sand.1  These  ther- 
mometers should  be  tested  for  accuracy  by  comparison  with  a  standard,  in  a  care- 
fully stirred  oil  bath.  The  standard  should  be  kept  exclusively  for  the  purpose 
and  be  allowed  to  stay  in  the  bath  until  cool.  Sudden  cooling  of  a  thermometer 
changes  the  zero  point.  The  standard  can  be  certified  by  the  makers  or  the 
United  States  Bureau  of  Standards. 

Electric  pyrometers  are  also  of  course  available  for  these  measurements.  An 
error  of  five  degrees  (5°)  in  the  reading  of  the  thermometer  affects  the  final  result 
by  about  20  calories. 

In  case  none  of  these  appliances  be  at  hand,  the  maximum  temperature  can 
be  determined  by  utilizing  the  melting-points  of  certain  pure  salts  or  metals; 
as  tin  232°,  bismuth  270°,  cadmium  302°,  lead  327°,  zinc  419°,  cadmium 
chloride  541°,  antimony  630°,  etc.  These  can  be  suspended  in  the  chimney 
in  small  covered  cast-iron  boxes. 

Composition  of  the  Coal.  This  is  determined  by  the  usual  methods  of 
organic  combustion  and  is  required  only  for  very  accurate  work. 

Calculation: 

a.  Heat  passing  up  chimney; 

b.  Pounds  of  air  per  pound  of  coal. 

(a)  Heat  Passing  up  Chimney.  The  accurate  calculation  resolves  itself  into 
finding  what  volume  of  gas  of  the  composition  determined  by  analysis  would  be 
produced  by  a  kilo  of  the  coal  used,  and  whose  analysis  is  known.  The  temperature 
of  the  escaping  chimney  gases  being  also  known,  and  their  specific  heat,  the 
quantity  of  heat  they  carry  off  can  be  calculated:  this  divided  by  the  calorific 
power  of  the  coal  gives  the  per  cent  of  heat  lost  in  the  chimney  gases.  The  cal- 
culation is  rather  long  and  will  be  found  in  detail  in  the  author's  book.2 

The  formula  of  Shields.3 

Per  cent  carbon  in  coal 
Per  cent  heat  lost  =  —  —  -  -  -  -  -  -  r 

Heatmg  value  of  coal 

200+per  cent  COz  .    0^  vx^  00^,1 

'  Xnse  in  temperature  in  °C.X  0.2864, 


, 
Per  cent  C02+per  cent  CO 

gives  results  usually  0.5%  low,  as  no  cognizance  has  been  taken  of  the  water 
vapor. 

Another  formula4  in  which  only  the  carbon  dioxide  and  its  temperature  enters 
was  proposed  by  Bunte  and  gives  close  results. 

For  every  per  cent  of  carbonic  acid  present  43.43  calories  per  cubic  meter  of 

1  With  rounded  grains,  not  river  sand,  as  it  would  make  scratches. 

2  "  Gas  and  Fuel  Analysis  for  Engineers."     Wiley. 

3  "  Power/'  30,  1121,  1909. 

*  J.  J.  Gasbeleuchtieng,  43,  637,  1900. 


710 


GAS   ANALYSIS 


flue  gases  have  been  developed  =W;  C=  specific  heat  of  the  flue  gases  per  cubic 
meter;  then  W/C  represents  the  initial  temperature  (which  is  never  attained)  the 
ratio  of  which  to  the  actual  exit  temperature  of  the  flue  gases  shows  the  heat 
lost.  If  T  =this  initial  temperature  and  t  the  rise  of  temperature  of  the  flue  gases, 
then  t/T  represents  the  heat  lost  in  the  chimney  gases. 

The  following  table  gives  the  data  for  the  calculation  for  both  pure  carbon  and 
coal  of  average  value : 


Per  Cent  of  COi  in 
Chimney  Gas. 

Specific  Heat  of 
Chimney  Gas. 

Initial  Temperature,  W/C.     Degrees  C. 

For  Carbon  =  T. 

For  Coal  =r. 

Diff.for0.1%COi. 

1 

0.308 

141 

167 

1  « 

2 

0.310 

280 

331 

1O 

1ft 

3 

0.311 

419 

493 

J.O 

1ft 

4 

0.312 

557 

652 

J.  U 
1C 

5 

0.313 

694 

808 

Xtl 
1  K 

6 

0.314 

830 

961 

-LtJ 

i  "> 

7 

0.315 

962 

1112 

xu 
1  ^ 

8 

0.316 

1096 

1261 

JLO 

1  f* 

9 

0.318 

1229 

1407 

10 

14 

10 

0.319 

1360 

1550 

H 

11 

0.320 

1490 

1692 

14 

12 

0.322 

1620 

1830 

11 
14. 

13 

0.323 

1750 

1968 

11 
1  °. 

14 

0.324 

1880 

2102 

Id 

10 

15 

0.324 

2005 

2237 

lo 

10 

16 

0.325 

2130 

2366 

lo 

If  there  were  11.5%  carbonic  acid,  the  initial  temperature  T  would  be  1762°; 
the  rise  of  temperature  in  the  chimney  gases  is  250°,  the  loss  is  fffa  or  14.2%. 
The  accurate  calculation  gives  14.1. 

Finally,  for  very  rapid  work,  Bunte's  Chart,  Table  V,  may  be  used.  The 
results  are  within  .2%  for  about  12%  of  carbonic  acid.  It  is  used  by  noting  the 
point  where  the  diagonal  line  representing  C02  cuts  the  ordinate  of  temperature — 
the  abscissa  corresponding  to  this  point  represents  the  per  cent  loss. 

The  following  table  shows  roughly  the  excess  of  air,  and  per  cent  of  heat  lost 
in  the  chimney  gases,  their  temperature  being  518°  F. 


Per  cent  CO2.  . 
Vol.  air  more 
than  theory 
=  10 

2 
9  5 

3 
6  3 

4 

4  7 

5 
3  8 

6 
3  2 

7 
2  7 

8 
2  4 

9 
2  1 

10 
1  0 

11 

1  7 

12 

1  6 

13 
1  5 

14 
1.4 

15 
1  3 

Per  cent  loss 
of  heat  

90 

60 

45 

36 

30 

26 

23 

20 

18 

16 

15 

14 

13 

12 

If  the  oxygen  be  from  1.5%  to  2%  with  the  temperature  of  escaping  gases  at 
400-500°  F.,  the  fires  are  too  thick;  if  it  be  less  than  8%  they  are  too  thin. 

(6)  Pounds  of  Air  per  Pound  of  Coal.  This  can  be  determined  by  calculat- 
ing the  ratio  of  carbon  to  oxygen  in  the  carbonic  acid  and  carbon  monoxide  and 
oxygen  of  the  chimney  gases,  or  by  the  formula  of  Shields.1 


1  Loc.  cit. 


GAS  ANALYSIS 


711 


,    Per  cent  of  carbon  in  coal 

Pounds  of  air  per  pound  of  coal  =2.31 

Per  cent  C02+per  cent  CO 

Loss  Due  to  Carbonic  Oxide.  For  every  gram  of  carbon  burned  to  carbonic 
oxide  there  is  a  loss  of  5.66  calories. 

Smoke.  For  the  determination  of  the  amount  of  smoke  in  the  chimney  gases, 
use  may  be  made  of  the  Ringelmann  smoke  scale.  This  consists  l  of  a  series  of 
rectangles  f  in.X|  in.  filled  with  cross-hatching  lines  a  greater  or  less  distance 
apart,  with  which  the  density  of  the  smoke  can  be  compared.  Or  the  Eddy 
smoke  recorder2  may  be  employed;  this  consists  of  a  tube  of  standard  length 
through  which  the  smoke  gases  are  drawn.  A  standard  electric  light  is  fixed  at 
one  end  of  the  tube  and  viewed  through  the  smoke;  its  density  is  measured  by 
the  extent  to  which  the  light  is  obscured. 


II.  PRODUCER  AND  FUEL  GASES.     BLAST=FURNACE  GAS 

Here  the  object  is  the  reverse  of  that  in  the  chimney  gases,  to  keep  the  per- 
centage of  carbon  monoxide  as  high  as  possible  and,  for  gas-engine  purposes,  the 
per  cent  of  hydrogen  constant. 

The  determinations  made  are  the  same  as  in  chimney  gas — C02,  0,  CO,  N,  and 
oftentimes  hydrogen  and  hydrocarbons;  the  quantity  of  dust  is  sometimes  impor- 
tant. The  heating  value  is  determined  as  in  illuminating  gas,  p.  713.  The 
efficiency  of  conversion  would  be  found  by  measuring  the  number  of  cubic  feet  of 
gas  made  per  ton  of  coal  gasified;  the  calorific  power  of  each  (gas  and  coal)  being 
known,  their  quotient  represents  the  efficiency.  The  heat  contained  in  the  gas 
due  to  its  sensible  heat,  found  after  the  manner  of  calculating  the  loss  in  chimney 
gases  (i.e.,  volume  gas  X weight  X rise  of  temperature X specific  heat)  is  to  be 
added  to  this  for  accurate  work. 

As  showing  producer  gas  practice,  the  following  typical  analyses  are  cited: 


Anthra- 
cite.4 

Bitu- 
minous.4 

BlueWater 
Gas.4 

Lignite.4 

Peat.5 

Tan.«,  4 

Wood.* 

CO 

27.0 

27.0 

45.0 

22.0 

30.6 

14.2 

13.3 

H2  

12.0 

12.0 

45.0 

9.6 

6.1 

8.7 

21.0 

CH4     

1.2 

2.5 

2.0 

1.6 

5.1 

5.6 

2.6 

C2H4  

0.4 

0.7 

0.3 

C02  

2.5 

2.5 

4.0 

6.4 

5.7 

15.0 

16.0 

N2  

57.0 

55.3 

2.0 

58.9 

52.5 

56.0 

46.7 

O2  

0.3 

0.3 

0.5 

0.8 

0.4 

0.1 

B  tu 

137 

157 

322 

132 

140 

1  Power,  40,  66. 

2  Made  by  the  Hamler-Eddy  Smoke  Recorder  Co.,  Chicago. 

3  With  38.7%  H2O,  3.2%  ash. 

4  From  "Gas  Producers  and  Producer  Gas  Power  Plants,"  R.  D.  Wood  &  Co., 
1906. 

5  Richards,  J.  W.,  J.  Frank.  Inst.,  415,  1900,  quoted    from    V.  Ihering,    "Gas 
Maschinen." 


712 


GAS  ANALYSIS 


GAS  FROM  DIFFERENT  KINDS  OF  PRODUCERS 


Down 
Draft.a 

Up  Draft.' 

Suction.1 

Pressure, 
Taylor,  i,  2 

MoncU 

Blast 
Furnace.* 

Siemens.* 

CO.. 

17  5 

18  3 

26   0 

22-30 

16  0 

24 

28 

H2  

11  8 

12  9 

18  5 

15-7 

24  0 

2 

2 

CH4  

1.1 

3.1 

0.5 

3-1  5 

2  2 

C2H4  

.04 

0  2 

2 

2 

C02  

9.2 

9  8 

8  0 

6-1  5 

12  4 

12 

3 

N2  

60.1 

55.6 

47  0 

54-60 

45  4 

60 

65 

O2  

0.2 

.04 

o 

B.t.u  

110 

145 

138 

146 

106 

122 

Determination  of  Dust.  Liddell6  recommends  the  following:  lump  sugar  is 
crushed,  and  that  which  is  retained  by  a  90-mesh  sieve  packed  in  a  2-in.  layer 
upon  copper  or  brass  gauze  contained  in  a  glass  tube.  The  sugar  is  slightly 
moistened  and  the  gas  sucked  through  it:  it  is  then  dissolved  in  water  and  the 
dust  collected  upon  a  tared  Gooch  crucible  and  weighed.  Another  procedure  and 
apparatus  recommended  by  the  Sargent  Steam  Meter  Co.,  of  Chicago,6  consists 
in  sucking  the  gas  through  a  diaphragm  consisting  of  a  weighed  filter  4J  ins,  in 
diameter,  drying  and  noting  the  increase  in  weight. 


III.  ILLUMINATING  GAS 


The  determinations  usually  made  are  as  follows: 


a.  Candle  power; 

b.  Calorific  power; 

c.  Sulphur; 

d.  Ammonia; 


e.  Analysis; 
/.   Carbon  dioxide; 
g.  Specific  gravity; 
h.  Tar. 


(a)  Candle  Power.  This  can  be  very  satisfactorily  found  using  a  60-in.  open- 
bar  photometer  and  Leeson  contrast  disc.  The  gas  should  be  burned  from  a 
burner  commercially  obtainable  which  gives  the  highest  candle  power;  for  gas 
from  14  to  21  candle  power,  Sugg's  London  argand  burner,  sizes  C  to  F,  should 
be  used;  for  richer  gases,  Sugg's  table  top  or  the  Bray  slit  burner.  For  a  standard 
of  comparison,  the  sperm  candle  is  convenient,  satisfactory,  and  very  extensively 
used  :  the  Elliott  kerosene  and  Hefner  amyl  acetate  lamps  are  also  employed. 

For  accurate  work  the  Lummer-Brodhun  disc  and  electric  standards,  or  the 
Hefner  lamp  should  be  used.  For  the  determination  of  candle  power,  reference 


"Gas  Producers  and  Producer  Gas  Power  Plants,"  R.  D.  Wood  &  Co., 
1906. 

2  With  anthracite  buckwheat. 

*  "Resume"  of  Producer  Gas  Investigations,"  Bureau  of  Mines  Bulletin  13,  Fernald 
&  Smith. 

4  Richards,  J.  W.,  J.  Frank.  Inst.,  415,  1900,  quoted  from  V.  Ihering,  "Gas 
Maschinen." 

6  Power,  38,  93. 

6  Power,  27,  331. 


GAS  ANALYSIS 


713 


may  be  had  to  Circular  No.  48  of  the  Bureau  of  Standards  on  "  Standard  Methods 
of  Gas  Testing,"  1914,  or  Stone,  "Practical  Testing  of  Gas  and  Gas  Meters," 
Wiley,  1909. 

Carburetted  water  gas  shows  from  20-28  candle  power,  coal  gas  14-20, 
oil  gas  45-60,  oil-air  gas  30-35,  gasolene  12-17,  acetylene  170-200.  (Stone, 
op.  cit.) 

(b)  Calorific  Power,     (a)   Direct    Determination.     This  is  most   commonly 


FIG.  125. 


determined  by  the  Junkers  calorimeter,  although  others  in  use  are  the  Sargent, 
Doherty,  and  in  England  the  Boys  and  Simmance-Abady. 

The  original  form  is  shown  in  section  in  Fig.  124  and  the  later  modification  in 
Fig.  125.  As  seen  in  Fig.  124  it  consists  of  a  combustion-chamber,  28,  surrounded 
by  a  water-jacket,  15  and  16,  this  being  traversed  by  a  great  many  tubes.  To 
prevent  loss  by  radiation  this  water-jacket  is  surrounded  by  a  closed  annular 
air-space,  13,  in  which  the  air  cannot  circulate.  The  whole  apparatus  is  con- 
structed of  copper  as  thin  as  is  compatible  with  strength.  The  water  enters  the 
jacket  at  1,  passes  down  through  3,  6,  and  7,  and  leaves  it  at  21,  while  the  hot 
combustion  gases  enter  at  30  and  pass  down,  leaving  at  31.  There  is  therefore 


714 


GAS  ANALYSIS 


not  only  a  very  large  surface  of  thin  copper  between  the  gases  and  the  water, 
but  the  two  move  in  opposite  directions,  during  which  process  all  the  heat  generated 
by  the  flame  is  transferred  to  the  water,  and  the  waste  gases  leave  the  apparatus 
approximately  at  atmospheric  temperature.  The  gas  to  be  burned  is  first  passed 
through  a  meter/Tig.  126,  and  then,  to  insure  constant  pressure,  through  a  pressure- 
regulator.  The  source  of  heat  in  relation  to  the  unit  of  heat  is  thus  rendered 
stationary;  and  in  order  to  make  the  absorbing  quantity  of  heat  also  stationary, 
two  overflows  are  provided  at  the  calorimeter,  making  the  head  of  water  and  over- 


FIG.  126. 


flow  constant.  The  temperatures  of  the  water  entering  and  leaving  the  appann  us 
can  be  read  by  12  and  43;  as  shown  before,  the  quantities  of  heat  and  \v;ii<  r 
passed  through  the  apparatus  are  constant.  As  soon  as  the  flame  is  lighted, 
43  will  rise  to  a  certain  point  and  will  remain  nearly  constant. 

Manipulation.  The  calorimeter  is  placed  as  shown  in  Fig.  126,  so  that  one 
operator  can  simultaneously  observe  the  two  thermometers  of  the  entering  and 
escaping  water,  the  index  of  the  gas-meter,  and  the  measuring-glasses. 

No  draft  of  air  must  be  permitted  to  strike  the  exhaust  of  the  spent  gas. 

The  water-supply  tube  w  is  connected  with  the  nipple  a  in  the  center  of  the 
upper  container;  the  other  nipple,  b,  is  provided  with  a  waste-tube  to  carry  away 
the  overflow,  which  latter  must  be  kept  running  while  the  readings  are  taken. 


GAS   ANALYSIS  715 

The  nipple  c,  through  which  the  heated  water  leaves  the  calorimeter,  is  con- 
nected by  a  rubber  tube  with  the  large  graduate,  d  empties  the  condensed  water 
into  the  small  graduate. 

The  thermometers  being  held  in  position  by  rubber  stoppers  and  the  water 
turned  on  by  e  until  it  discharges  at  c,  no  water  must  issue  from  d  or  from  39, 
Fig.  19,  as  this  would  indicate  a  leak  in  the  calorimeter. 

The  cock  e  is  now  set  to  allow  about  two  liters  of  water  to  pass  in  a  minute 
and  a  half,  and  the  gas  issuing  from  the  burner  ignited.  Sufficient  time,  about 
twenty  minutes,  is  allowed  until  the  temperature  of  the  inlet-water  becomes  con- 
stant and  the  outlet  approximately  so;  the  temperature  of  the  inlet-water  is 
noted,  the  reading  of  the  gas-meter  taken,  and  at  this  same  time  the  outlet-tube 
changed  from  the  funnel  to  the  graduate.  Ten  successive  readings  of  the  out- 
flowing water  are  taken  while  the  graduate  (2-liter)  is  being  filled  and  the  gas 
shut  off. 

A  better  procedure  is  to  allow  the  water  to  run  into  tared  8-liter  bottles,  three 
being  used  for  a  test,  and  weighing  the  water.  The  thermometer  in  the  outlet 
can  then  be  read  every  half-minute. 

Example. — Temp,  of  incoming  water,  17.2° 

Temp,  of  outgoing  water,  43.8° 

Increase,  26.6° 


Gas  burned,  0.35  cu.ft. 

Liters  water X Increase  of  temp.     2X26.6 

Heat= =  =152.3  C. 

Cu.ft.  gas  0.35 

From  burning  1  cu.ft.  of  gas  27.25  cc.  of  water  were  condensed.  This  gives 
off  on  an  average  0.6  C.  per  cc. 

27.25X0.6=16.3  C.;  152.3-16.3=136  C.  per  cubic  foot;  136X3.968=540 
B.t.u. 

NOTES.  After  setting  up  the  apparatus  the  first  thing  to  be  done  is  to  turn  on  the 
water — (not  the  gas).  Similarly,  the  water  should  be  shut  off  last.  All  connections 
and  the  meter  should  be  tested  for  leaks  before  each  test.  The  water  level  in  the  meter 
should  be  checked  daily.  Slight  drafts  caused  by  moving  suddenly  near  the  apparatus 
will  vary  outlet  readings  and  vitiate  the  test.  The  instrument  should  not  be  set  up 
near  a  window  or  heating  apparatus  where  radiant  heat  might  affect  the  readings. 

If  0.2  cu.ft.  of  gas  are  burned,  then  an  error  of  0.1°  F.  in  temperature  of  water  means 
an  error  of  4  B.t.u.;  an  error  of  0.01  Ib.  water,  0.9  B.t.u.;  1°  F.  in  gas  temperature,  1.8 
B.t.u.;  0.1  in.  (barometer),  2  B.t.u.;  1  in.  water  pressure  of  gas,  1.5.  B.t.u.1 

The  calorific  power  obtained  without  subtracting  the  heat  given  off  by  the  con- 
densation of  the  water  represents  the  total  heating  value  of  the  gas.  This  is  the  heat 
given  off  when  the  gas  is  used  for  heating  water  or  in  any  operation  where  the  products 
of  combustion  pass  off  below  100°  C.  The  net  heating  value  represents  the  conditions 
in  which  by  far  the  greater  quantity  of  gas  is  consumed,  for  cooking,  heating  and  gas 
engines,  and  is  one  which  should  be  reported.  It  should,  however,  be  corrected,2 
to  the  legal  cubic  foot,  that  is,  measured  at  30  ins.  barometric  pressure,  and  60°  F. 
saturated  with  moisture. 

The  apparatus  has  been  tested  for  three  months  in  the  German  Physical  Technical 
Institute  with  hydrogen,  with  but  a  deviation  of  0.3%  from  Thomson's  value.  This 

1  Kept.  Joint  Committee  on  Calorimetry  Public  Service  Commission  and  Gas  Cor- 
porations in  the  Second  Public  Service  District  of  New  York  State,  p.  81,  1910. 

2  A  difference  of  1°  C.  or  of  3  mm.  pressure  makes  a  change  of  0.3%  in  the  volume. 
Pfeiffe,  J.  Gasbeleucht.,  50,  67,  1907. 


716 


GAS   ANALYSIS 


value  may  vary  nearly  that  amount  from  the  real  value  owing  to  the  method  which 
he  employed. 

The  chief  sources  of  error  are,1  in  adjusting  the  meter,  in  measuring  the  tem- 
perature— rise  of  the  water,  and  in  changing  over  the  outflow  water  to  the  weighed 
vessels. 

(b)  By  Calculation.2  Let  us  suppose  an  illuminating  gas  gave  the  following 
analysis:  Illuminants  15,  carbon  monoxide  25.3,  methane  25.9,  hydrogen  27.9%; 
the  heating  value  of  these  gases  according  to  Table  3,  page  737  is  as  follows: 

0.15  X2000  =300.0  B.t.u. 
0.253X341   =  86.3 
0.259X1065=276.0 
0.279X345   =  96.3 

758.6  B.t.u. 

which  is  the  gross  heating  value  of  the  gas.  The  correction  for  the 
heat  lost  is  found  as  with  chimney  gases,  by  multiplying  the  volume 
of  the  combustion  gases  by  their  weight  X  specific  heat  X  rise  of  temp- 
erature. 

(c)  Sulphur.  Sulphur,  being  present  in  gas  in  so  many  forms, 
is  determined  by  combustion  and  usually  reported  in  grains  of  sul- 
phur per  hundred  cubic  feet. 

One  of  the  most  easily  portable  and  satisfactory  forms  is  that  of 
Hinman  and  Jenkins  described  as  follows:3  The  upper  vessel,  Fig. 
127,  is  a  "  bead  glass  "  300  mm.  long  and  60  mm.  in  diameter;  this 
is  filled  with  large  cut-glass  beads,  held  up  by  a  suitable  fluted  glass, 
giving  a  large  condensing  surface  without  obstructing  the  draft.  To 
this  bead  glass  is  attached,  by  a  rubber  connector,  the  adapter, 
410  mm.  long  and  50  mm.  lower  internal  diameter.  To  the  upper 
adapter  is  attached,  by  means  of  the  "  connecting  piece,"  the  lower 
adapter,  400  mm.  long  and  40  mm.  lower  diameter.  The  connect- 
ing piece  projects  12  mm.  above  the  top  of  a  rubber  stopper,  fitting 
the  upper  adapter,  and  is  surmounted  by  a  watch-glass  deflector 
carried  on  platinum  wires.  An  overflow  tube  carries  the  condensation 
to  the  Erlenmeyer  flask  hung  on  the  stopper  as  shown;  this  tube  is  so 
adjusted  that  some  liquid  remains  on  the  stopper  to  keep  it  cool  and  to  absorb 
some  of  the  ascending  gases.  The  Bunsen  burner  is  fitted  with  a  lava  tip  having 
a  5-mm.  hole;  surrounding  the  burner  is  a  glass  tube  20  mm.  in  diameter,  forming 
the  inner  wall  of  an  annular  chamber,  of  which  the  outer  wall  is  a  glass  ring 
50  mm.  in  diameter.  Into  this  chamber,  which  serves  to  contain  10%  ammonium 
hydroxide,  the  lower  adapter  dips  10  mm. 

The  lower  adapter  is  joined  to  the  "  connecting  piece  "  by  a  short  cork-lined 
metal  tube.  Although  radically  different  in  form,  this  apparatus  is  very  similar 
to  the  Referees'  hi  general  principle  and  in  method  of  use,  the  principal  difference 

technologic  Papers  of  the  Bureau  of  Standards  No.  36.  "Gas  Calorimetry," 
Waidner  and  Mueller,  page  100,  1914. 

2  U.  S.  Geol.  Survey  Paper  No.  48;  Part  III,  page  1005. 

•Jenkins,  J.  Am.  Chem.  Soc.,  28,  543,  1906,  also  Technologic  Paper  No.  20, 
Bureau  of  Standards,  McBride  and  Weaver  "  Determination  of  Sulphur  in  Illuminat- 
ing Gas,"  1913,  also  Stone,  op.  cit. 


FIG.  127. 


GAS  ANALYSIS  717 

being  the  use  of  ammonium  hydroxide  instead  of  dry  ammonium  carbonate  as 
a  source  of  ammonia.  About  10  cc.  of  concentrated  ammonium  hydroxide  is 
placed  in  the  reservoir  about  the  burner  at  the  beginning  of  the  test  and  about 
5  cc.  more  added  every  fifteen  or  twenty  minutes.  The  gas  is  consumed  at  the 
rate  of  0.4  to  0.6  cu.ft.  per  hour,  and  2.5  to  3  ft.  burned,  if  the  sulphur  is  to  be 
estimated  gravimetrically,  otherwise  1  cu.ft.  is  enough.  When  the  run  is  com- 
pleted the  apparatus  is  allowed  to  cool  and  is  then  flushed  four  times  by  pouring 
50  cc.  portions  of  water  in  at  the  top  of  the  bead  tube.  To  the  solutions  and  wash- 
ings are  added  2-3  cc.  bromine  water,  and  it  is  evaporated  to  30  or  40  cc. ;  an  excess 
of  a  hydrochloric  acid  solution  of  barium  chromate  is  added  to  the  hot  solution, 
it  is  gently  boiled,  an  excess  of  dilute  ammonia  added,  again  boiled  for  a  minute, 
filtered  and  washed.  The  ammonium  chromate  in  the  filtrate  (the  chromic 
acid  being  equivalent  to  the  sulphuric  acid  in  the  original  solution)  after  being 
boiled  in  a  stout  flask,  with  a  Bunsen  valve,  to  expel  the  air,  is  cooled  and  titrated 
directly  with  stannous  chloride  (3.25  grams  Sn  per  liter)  using  starch  and  potassium 
iodide  to  accentuate  the  end  point. 
The  equations  are : 

(NH4)2S04+BaCr04  =  BaS04+  (NH4)2Cr04, 
2(NH4)2Cr04+2HCl  =  (NH4)2Cr207+2NH4Cl+H20, 
3SnCl2+(NH4)2  Cr207+14HCl  =3SnCl4+2NH4Cl+2CrCl3+7H20. 

The  strength  of  the  stannous  chloride  should  be  determined  at  the  same  time 
by  standard  bichromate  of  potassium. 

Or  the  sulphuric  acid  can  be  determined  with  the  turbidimeter  as  for  sulphur 
in  oils,  page  570.  The  amount  of  sulphur  is  usually  from  20  to  30  grains  per 
100  cu.ft. 

Sulphuretted  Hydrogen.1  The  test  is  made  by  hanging  a  strip  of  paper 
moistened  with  lead  acetate  solution  (1  :  20)  in  a  bell-jar  or  tube  through  which 
the  gas  is  passing  at  about  5  cu.ft.  per  hour  and  allowing  it  to  act  for  one  minute. 
Usually  several  tests  are  made.  The  gas  should  be  taken  fresh  from  the  main 
and  care  should  be  taken  not  to  confound  any  black  tarry  spots  with  lead  sulphide. 
A  properly  purified  gas  should  give  no  test. 

It  is  quantitatively  determined  by  drawing  a  known  volume  of  the  gas  through 
standard  iodine  solution.  Tutweiler2  measures  the  gas  in  a  modified  Bunte 
burette  over  mercury,  and  having  added  starch  solution,  runs  in  a  known  quantity 
of  standard  iodine  solution  until  it  is  in  slight  excess.  If  100  cc.  of  gas  were  taken, 
the  number  of  cubic  centimeters  of  solution  gives  the  grains  of  H2S  per  100  cu.ft., 
1  cc.  iodine  =0.0017076  gram  iodine  =100  grains  H2S  per  100  cu.ft. 

(d)  Ammonia.  This  is  determined  by  absorption  in  standard  acid  colored 
with  cochineal:  10  cc.  of  HC1  are  placed  in  the  bulb,  Fig.  117,  2-3  drops  cochineal 
solution  added,  and  the  gas  allowed  to  bubble  through  it  until  the  yellow  color 
changes  to  a  deep  purple;  the  meter  is  now  read.  The  acid  is  made  by  diluting 
38.2  cc.  N/10  HC1  to  1  liter,  10  cc.  =0.01  grain  of  NH3;  the  cochineal  solution  is 
made  by  treating  3  grams  of  the  ground  insect  with  250  cc.  20%  alcohol,  allowing 
to  stand  forty-eight  hours  and  filtering.  The  bubble  tube  is  inserted  in  series 

1  Tech.  Paper  No.  41,  Bureau  of  Standards,  "  Lead  Acetate  Test  for  Hydrogen 
Sulphide  in  Gas." 

2  J.  Am.  Chem.  Soc.,  23,  173,  1901. 


718 


GAS   ANALYSIS 


with  the  gas  supply  to  the  sulphur  apparatus,  Fig.  127,  (c)  so  that  both  determi- 
nations are  run  at  one  time:  the  gas  is  passed  through  at  the  rate  of  0.6  to  0.8 
cu.ft.  per  hour.  Massachusetts  law  limits  the  amount  of  ammonia  to  10  grains 
per  100  cu.ft. 

(e)  Analysis.  The  volumetric  analysis  is  carried  out  according  to  pages  704; 
either  bromine  water  or  fuming  sulphuric  acid  can  be  used  to  absorb  the  "  illumi- 
nants."  Besides  ethylene,  it  may  be  desirable  to  determine  benzol:  this  is  best 
done  according  to  Dennis,  O'Neill  and  McCarthy  1  by  absorption  in  an  ammoniacal 
solution  of  nickel  cyanide. 

Naphthalene.  This  is  determined  in  purified  gas  by  passing  it  through  N/20 
picric  acid  solution.  White  2  determines  it  in  raw  gas  by  precipitation  of  the 
picrate  and  subsequent  recovery  of  the  naphthalene. 


COMPOSITION  OF  COMMERCIAL  GASES  3 


C02 

i  nrts. 

Of. 

CO. 

H2. 

CH4. 

C2H6. 

N2. 

Candle 
Power. 

B.t.u. 

Coal 

1  6 

4  0 

0  4 

8  5 

49  8 

29  5 

3  2 

3  2 

16  1 

622 

Carb.  water. 

3  0 

13  3 

0  4 

30  4 

37  7 

10  0 

3  2 

2  1 

22  1 

643 

Blue  water 

3  4 

0  0 

0  9 

40  9 

50  8 

0  2 

o 

3  5 

299 

Pintsch  

0  ? 

30.0 

0 

0  1 

13  ?, 

45.0 

9.0 

1  6 

43  0 

1276 

Blau  

0 

51.9 

0 

0  1 

?,  7 

44.1 

0. 

1  ?, 

48  2 

1704 

Oil-  water  
Oil  
Gasolene  
Acetylene  

Natural  

2.6 
0.3 

0  3 

7.0 
31.3 
1.5 

96.0 

0.3 

0.2 
0. 
18.5 
0.8 

0  3 

9.2 

2.4 

0  5 

39.8 
13.5 

?,  3 

34.6 
46.5 
CeHi4 

92.6 

'3^9 
=  10.3 

6.6 
1.1 
69.7 
3.2 

3  5 

19.7 
38.0 
16.0 
225.0 
H2S 

680 
1320 
514 
1350 

840-1170' 

0.2 

(f)  Carbon  dioxide.     This  is  best  determined  by  Rudorff 's  method 6  which 
consists  in  titrating  about  a  liter  of  the  gas  with  standard  potassium  hydroxide. 
The  arrangement  and  manipulation  of  this  apparatus  will  be  evident  from  Fig.  128: 
the  capacity  of  the  Woulff  bottle  must  be  known  and  if  the  gas  contains  hydrogen 
sulphide,  it  must  be  absorbed  by  passage  over  manganese  dioxide. 

(g)  Specific  Gravity.    The  readiest  method  depends  upon  the  time  of  efflux 

of  the  gas  compared  with  air;  sp.gr.  =~rG  and  A  represent  the  times  of  efflux 

Az 

in  seconds  of  gas  and  air.    The  apparatus  is  obtainable  from  the  dealers,  or  may 
be  constructed  according  to  Jenkins 6  as  follows : 

"  It  consists,  Fig.  129,  of  two  large  rubber  stoppers,  each  having  a  brass  tube, 
projecting  laterally  near  the  large  end,  and  connecting  with  the  hole  in  the  stopper. 
A  glass  piece  A  in  the  form  of  a  truncated  cone  fits  tightly  over  one  stopper;  it  is 
9  ins.  long,  l£  ins.  diameter  at  the  base  and  1  in.  at  the  top.  A  similarly  shaped 
piece  B  9  ins.  long  by  l£  ins.  diameter  at  the  lower  end  fits  over  the  second  stopper; 
2  ins.  above  the  latter  the  tube  has  a  constriction  1  in.  in  diameter,  and  at  its 

1  J.  Am.  Chem.  Soc.,  30,  236,  1908. 

2  Proc.  Mich.  Gas  Association,  83,  1904,  1905. 

8  Fulweiler,  Rogers'  and  Aubert's,  "  Industrial  Chemistry,"  2d  Ed.,  404. 
4  Orton,  Geol.  of  Ohio,  VI,  137. 
6  Hempel,  op.  cit.,  262. 
6  Stone,  op.  cit.,  261. 


GAS  ANALYSIS 


719 


upper  part  is  narrowed  to  a  neck  -f^  in.  in  diameter  which  is  ground  on  the  inside 
to  receive  the  end  of  a  tube  7|  ins.  long  and  j  in.  in  diameter,  in  the  upper  end  of 
which  is  fitted  a  platinum  plate  containing  the  emission  orifice.  One  and  three- 
fourths  inches  below  this  plate  is  a  three-way  glass  stopcock,  and  3  ins.  below  the 
latter  a  scratch  surrounds  the  tube  and  serves  as  the  upper  mark  in  the  escape 
of  the  gas. 

"  Fitted  into  the  hole  in  the  stopper  is  a  hollow  cylinder  of  brass  to  which  is 
soldered  a  curved  piece  of  brass  wire  pointed  at  the  end,  which  rises  1^  ins.  above 
the  surface  of  the  stopper.  The  two  brass  tubes  projecting  from  the  outside  of 
the  stoppers  are  joined  by  a  piece  of  rubber  tubing  15  to  18  ins.  long. 

"  In  using  this  instrument  the  larger  tube  B  is  filled  with  water,  of  the  tem- 
perature of  the  room,  nearly  to  the  top,  the  stopcock  being  turned  so  that  egress 


FIG.  128. 


FIG.  129. 


of  air  from  the  smaller  tube  is  prevented.  The  larger  tube  is  placed  on  an  elevated 
surface  just  high  enough  so  that  its  bottom  is  above  the  level  of  the  scratch  on 
the  narrow  outlet  tube,  the  cock  is  turned  so  that  the  air  may  escape  through  the 
orifice  in  the  platinum  plate,  and  on  the  second,  when  the  point  of  the  brass  wire 
breaks  the  surface  of  the  rising  water,  a  stop  watch  is  started.  The  latter  is  stopped 
when  the  water  exactly  reaches  the  scratch. 

"  The  large  tube  is  lowered,  and  the  stopcock  turned  so  that  air  may  enter 
through  its  hollow  point.  When  the  water  is  again  all  in  the  large  cylinder,  the 
cock  is  turned  to  connect  the  small  vessel  with  the  outside  air  through  the  platinum 
tip,  the  large  cylinder  is  replaced  on  the  elevation  and  the  operation  repeated. 
Results  should  be  obtained  which  check  within  one-fifth  second. 


720  GAS   ANALYSIS 

"  Now  connect  a  rubber  tube  to  the  gas  supply  and  to  the  tip  of  the  stopcock, 
lower  the  large  cylinder  and  force  the  water  into  the  latter  by  means  of  the  gas 
pressure.  Thoroughly  saturate  the  water  with  the  gas  to  be  tested;  this  may  be 
done  by  shaking  gas  and  water  together  and  by  forcing  the  water  up  and  down 
in  the  small  vessel  in  contact  with  the  gas.  Repeat  the  operation  with  gas  in 
in  the  same  manner  as  described  for  air.  The  calculation  is  made  in  accordance 
with  the  formula. 

"  The  advantages  of  this  apparatus  are  its  portability,  its  cheapness,  its  rapidity 
and  accuracy.  When  set  up,  the  cylinders  are  inclined  to  be  a  trifle  unstable; 
this  may  be  overcome  by  fastening  a  lead  plate  to  the  base  of  each  stopper. 
Four  precautions  in  connection  with  its  use  should  be  emphasized:  (1)  The  water 
must  be  of  the  room  temperature;  (2)  the  water  must  be  thoroughly  saturated 
with  the  gas;  (3)  the  platinum  tip,  stopcock,  and  upper  part  of  the  tube  must  be 
kept  dry  and  clean;  (4)  the  large  cylinder  must  always,  in  any  one  determination, 
be  placed  at  the  same  height." 

Another  method  consists  in  the  use  of  the  Lux  gas  balance.  This  consists  of 
a  balanced  globe  into  which  the  gas  previously  filtered  through  cotton,  passes  and 
its  specific  gravity  is  read  off  directly  on  a  scale. 

The  knowledge  of  the  specific  gravity  is  important,  as  it  is  involved  in  the 
formula  for  the  calculation  of  the  flow  of  gas  in  pipes;  it  also  enables  the  gas 
manager  to  ascertain  the  weight  of  gas  produced  from  the  coal,  and  to  get  an  idea 
of  the  nature  and  amount  of  impurities  in  the  gas,  all  these  being  heavier. 

(h)  Tar.  For  the  estimation  of  tar,  Clemens  Winkler  l  recommends  the  pro- 
cedure of  Tief trunk:  This  consists  in  passing  the  gas  through  25%  alcohol  and 
collecting  and  weighing  the  tar  on  a  tared  filter. 

IV.  SULPHURIC  ACID  GASES, 

the  gases  involved  in  the  manufacture  of  sulphuric  acid : 

a.  Burner  gases; 

b.  Nitrogen  gases; 

c.  Oxygen; 

d.  Gases  involved  in  the  contact  process. 

(a)  Burner  Gases.   Sulphur  Dioxide 

This  gas  may  be  determined  by  the  method  of  Reich.  It  consists  in  aspirating 
the  gas  through  standard  iodine  solution  (N/10  is  suitable)  until  it  is  decolorized. 
The  amount  of  iodine  used  in  the  test  and  the  volume  of  the  aspirated  gas  being 
known,  the  percentage  of  S02  can  readily  be  calculated. 

Fig.  130  shows  a  form  of  apparatus  for  making  this  determination.  The 
standard  iodine,  5  to  25  cc.  N/10  I,  diluted  to  150  to  200  cc.,  is  placed  in  the 
bottle,  about  400  cc.  capacity,  and  starch  indicator  added.2  The  gas  to  be  tested 
is  aspirated  through  the  iodine  until  the  color  of  the  starch  blue  fades  completely. 
Water  which  flows  out  from  the  graduated  cylinder  by  lowering  the  aspirating 
bottle,  produces  the  suction,  and  the  amount  measures  the  volume  of  the  aspirated 
gas.  From  the  quantity  of  iodine  used  and  the  volume  of  the  gas  required  to 
decolorize  the  solution  the  per  cent  of  sulphur  dioxide  is  calculated. 

1  "  Die  Industrie  Case,"  page  52,  also  Hempel,  op.  cit.,  239. 

2  Starch  indicator  may  be  omitted  if  the  light  is  good  for  observing  the  fading  out  of 
the  iodine  color. 


GAS  ANALYSIS 


721 


Should  the  contact  gas  contain 
S03,  this  is  absorbed  by  passing  the 
gas  through  50  to  100  cc.  of  strong 
H2SO4,  to  avoid  the  action  of  S03 
on  the  rubber  tubing  of  the  appara- 
tus. A  rapid  current  of  the  gas  is 
passed  through  the  acid  to  saturate 
it  with  S02  before  making  the  tests. 

The  Reich  method  is  more  appli- 
cable for  determining  small  amounts 
of  S02.  A  12-15-liter  graduated  as- 
pirating bottle  is  used  in  works  tests 
of  exit  gases  for  measuring  the  gas. 
Since  these  volumes  are  under  stand- 
ard conditions  (760  mm.  and  0°  C.), 
it  will  be  necessary  to  convert  the 
volumes  obtained  in  the  tests  to  these 
conditions,  using  the  formula  V  = 

F° 


760(l+oo3670' 
measured  volume,  P°  =  observed  bar- 
ometric pressure,  t=  temperature  of 
the  gas,  and  w  =  aqueous  vapor  pres- 
sure at  temperature  of  the  test. 


Asp  i  rat  in  a 

Bottle 
/200c.c. 


iodine 
Solution 


Graduated 

Measuring  ^ 

Cylinder 


FIG.  130.    Portable  Reich  Apparatus. 


TABLE  FOR  REICH'S  TESTS  FOR  PERCENTAGE  S02. 

IODINE  SOLUTION 


USING  TENTH  NORMAL 


Volume  Per  cent  SO2 

25  cc.  N/10  Iodine. 

10  cc.  N/10  Iodine. 

5  cc.  N/10  Iodine. 

12 
11.5 
11 
10.5 
10 
9.5 
9 
8.5 
8 
7.5 
7 
6.5 
6 
5.5 
5 
4.5 
4 
3.5 
3 
2.5 
2 
1.5 
1.4 
1.3 
1.25 

205  c 
215 
226 
238 
252 
265 
283 
300 
321 
344 
371 
402 
438 

c-  g 

as 





148  cc.  gas 
161 
175 
192 
212 
237 
268 
308 
361 
436 

154  cc.  gas 
181  "    " 
218  "    " 
274  "    " 
367  "    " 
393  "    " 
424  "     " 
442  "     " 

722 


GAS  ANALYSIS 


Sulphur  Dioxide  in  Exit  Gases.1  Sulphur  dioxide  is  seldom  above  1%  in 
exit  gases  leaving  the  absorption  tower  of  the  sulphuric  acid  plant.  Generally 
the  loss  is  below  0.2%  on  a  carefully  regulated  unit.  The  Reich  method  is  suffi- 
ciently accurate  for  this  determination,  for  all  practical  purposes.  If  10  cc.  of 
N/10  iodine  are  used  the  percent  S02  may  be  calculated  by  the  formula: 


11.17 


Vo+11.17 


=  %S02. 


Fo= volume  of  the  gas  reduced  to  standard  condition  0°  C  and  760  mm. 
11.17  =  cc.  of  S02  gas  equivalent  to  10  cc.  of  N/10  iodine. 

The  following  table  is  calculated  on  the  assumption  that  the  gas  is  under  a 
pressure  of  760  mm. + vapor  pressure  of  17  mm.,  at  room  temperature  of  20°  C. 


Measured  Vol.  Per 

1000  cc 1.22 

1100  cc 1.09 

1200  cc 1.01 

1300  cc 93 

1400  cc 87 

1500  cc 81 

1600  cc 76 

1700  cc 72 

1800  cc 67 

1900cc 64 

2000cc 61 

2100cc 58 

2200  cc 

2300  cc 

2400  cc 

2500  cc 

2600  cc 

2700  cc 

2800  cc 

2900  cc 

3000  cc..  .41 


S02 
22 

Measured  Vol.           Per  cer 
3200  cc    

09 

3400  cc 

01 

3600  cc  .  . 

93 

3800  cc  

87 

4000  cc  

81 

4200  cc  

76 

4400  cc  

7?, 

4600  cc  

67 

4800  cc  

64 

5000  cc  .  

61 

5500  cc  

58 

6000  cc  

55 

6500  cc  

53 

7000  cc  

51 

7500  cc 

49 

8000  cc 

47 

8500  cc 

45 

9000  cc   

44 

9500  cc  

4?, 

10000  cc  

41 

S02 
.38 
.36 
.34 
.32 
.31 
.29 
.28 
.27 
.26 
.25 
.22 
.20 
.18 
.17 
.16 
.15 
.14 
.14 
.13 
.12 


Sulphur  Dioxide  in  the  Inlet  Gases  of  the  Sulphuric  Acid 

Contact  System 1 

Apparatus.  Burette.  This  should  be  of  the  bulb  type  with  a  graduated 
capacity  of  100  cc.,  the  bulb  holds  about  87  cc.;  the  stem  is  graduated  in  tenths 
of  a  cubic  centimeter  from  0  to  12  cc.  The  diameter  of  this  graduated  portion 
is  such  that  each  cubic  centimeter  occupies  approximately  18  mm.  in  length.  The 
total  length  of  the  burette  is  45  to  50  cc. 

There  is  a  constriction  at  the  lower  end  of  the  burette,  or  the  rubber  tube 
connecting  the  burette  with  the  leveling  tube  may  be  pinched  down  so  that  it 
requires  10  to  15  seconds  to  pass  100  cc.  of  tnercury  in  or  out  of  the  burette. 

The  burette  has  a  water  jacket  of  sufficient  capacity  to  include  the  chamber  of 
the  burette  and  its  graduated  portion.  The  diameter  should  be  sufficient  to 
accommodate  the  bulbed  portion  of  the  burette  and  a  thermometer  suspended  by 
its  side.  Distilled  water  boiled  free  of  air  is  used  in  this  water  jacket. 


Communicated  by  W.  W.  Scott 


GAS  ANALYSIS 


723 


A  thermometer  registering  from  5  to  35°  graduated  in  tenths  of  a  degree  is 
left  suspended  in  the  water  jacket  next  to  the  bulb. 

Leveling  Tube.  This  is  preferably  a  straight  glass  cylinder  constricted  at 
lower  end  to  accommodate  the  heavy-walled  rubber  tubing,  connecting  the  tube 
with  the  burette.  This  tube  is  about  52  cm.  long  and  has  a  diameter  of  18  to 
25  mm.  The  lower  portion  of  the  tube,  where  this  is  held  by  the  hand,  has  a  cover- 
ing either  of  rubber,  or  of  a  heat-insulating  material,  to  prevent  warming  of  the 
mercury  while  making  the  test. 

Capillary  Tube.    The  tube  connecting  the  burette  with  the  pipettes  and  the 


FIG.  131.1 


sampling  pipe   should  have  a  fine  capillary — the  entire  internal  capacity  should 
not  exceed  1  cc.     Details  of  construction  shown  in  the  figure. 

Pipette.  The  cylinder  of  the  pipette  has  a  capacity  of  150  to  175  cc.  The 
pipette  reservoir  of  500  to  550  cc.  capacity  is  recommended. 

Reagents.  Mercury.  Mercury  is  used  in  the  measuring  burette.  This 
should  be  kept  bright  and  clean  and  "  drag  no  tail."  To  keep  the  gas  saturated 
with  moisture  the  burette  should  contain  about  0.2  cc.  of  distilled  water  over  the 
mercury. 

Water  Solution  of  Chromic  Acid.  A  50%  solution  is  recommended,  although 
a  weaker  solution  may  be  used.  The  strength  of  the  reagent,  however,  should 
be  over  25%  Cr03. 

Sampling.  The  iron  pipes  carrying  the  gas  to  and  from  the  testing  appara 
tus  have  a  diameter  of  |  in.  to  f  in.  The  line  is  run  from  the  positive  pressure 

1  Orsat  apparatus  modified  by  T.  L.  Briggs  and  W.  W.  Scott 


724  GAS   ANALYSIS 

flue  near  the  blower  to  the  testing  apparatus  and  back  to  the  minus  pressure  flue 
entering  the  blower,  and  the  gas  allowed  to  flow  continuously  through  this  shunt 
line. 

Making  the  Test.  A  volume  of  100  cc.  of  the  gas  is  drawn  into  the  chamber 
burette  (Fig.  131),  by  opening  the  stopcock  A  (B  being  closed)  and  lowering  the 
leveling-tube — Stopcock  A  is  closed,  B  opened  and  the  gas  expelled  into  the  air  by 
raising  the  leveling  tube  H,  using  care  to  prevent  mercury  bumping  at  the  top 
of  the  reservoir.  (Mercury  carried  into  the  chromic  acid  will  reduce  this  reagent.) 
A  second  100  cc.  of  the  gas  is  taken  and  expelled  as  before.  Finally  a  third 
100  cc.,  carefully  measured,  is  taken  for  the  test.  The  top  of  the  mercury 
columns  in  the  burette  and  leveling]  tubes  should  be  exactly  level.  The  water 
surface  should  be  at  the  0  mark  on  the  burette.  Stopcock  B  is  always  closed 
during  the  drawing  in  of  the  gas.  The  temperature  of  the  water  jacket  is  now 
observed.  Stopcock  A  is  closed  and  stopcock  C  leading  to  the  absorption  pipette 
opened.  The  leveling  tube  is  raised  as  before  and  the  gas  completely  passed 
into  the  pipette.  The  gas  is  drawn  back  into  the  measuring  burette  by  lower- 
ing the  leveling  tube  and  measured.  The  mercury  columns  should  stand  at  the 
same  level,  the  reading  being  taken  at  the  surface  of  the  water  over  the  mercury. 
A  second  pass  into  the  pipette  is  now  made  and,  if  no  further  contraction  of  the 
gas  occurs,  the  reading  taken.  The  temperature  is  observed  and  a  correction 
made  of  0.36  cc.  per  degree  (centigrade)  rise  or  fall  of  temperature.  This  correc- 
tion is  added  if  the  temperature  rises,  or  is  subtracted  if  the  temperature  falls. 

The  contraction  of  the  gas,  due  to  absorption  of  S02,  in  terms  of  cc.  gives 
the  direct  per  cent  reading. 

Example: 

100  cc.  gas  taken. 

Final  reading  91.5,  i.e.,  direct  =8. 5  cc. 
Temperature  change  =0.4°  rise. 
Then  8.5  +  (.4  X. 36)  =8.6%  S02. 

Tests  should  be  made  in  duplicate,  each  Orsat  having  two  pipettes.  Very 
little  more  time  is  required  to  run  the  check  test  if  the  following  method  is  observed. 
The  first  sample  is  taken  and  passed  into  one  of  the  pipettes;  a  second  sample, 
immediately  taken,  is  passed  into  the  second  pipette.  The  first  sample  is  now 
again  measured  and  then  returned  to  the  first  pipette  and  then  the  check  sample 
measured  and  returned  to  its  pipette.  The  first  sample  is  again  measured  and  if 
a  further  contraction  is  observed  it  is  again  passed  into  its  pipette  and  the  process 
repeated  with  the  second  sample.  By  thus  alternating  the  tests  and  allowing  the 
gas  to  stand  in  the  pipettes  the  second  pass  will  cause  complete  absorption  of  S03, 
third  pass  seldom  being  necessary. 

Notes  and  Precautions.  Burette.  The  constriction  preventing  a  rapid  flow 
of  mercury  accomplishes  the  following: 

1.  It  prevents  the  wave  motion  of  mercury,  which  results  from  a  rapid  flow. 
This  wave  motion  makes  it  exceedingly  difficult  to  draw  in  100  cc.  of  gas  accurately, 
and  makes  it  necessary  to  hold  the  tube  several  seconds  until  the  motion  has  ceased 
before  taking  a  reading. 

2.  The  constriction  prevents  mercury  bumping  into  the  capillary  and  from 
being  thus  carried  into  the  absorption  reagent. 


GAS   ANALYSIS  725 

3.  It  minimizes  the  danger  of  drawing  the  absorption  reagent  into  the  chamber 
burette. 

Water  in  the  Burette.  The  burette  should,  as  stated,  always  contain  about 
0.2  cc.  of  water,  over  the  mercury  to  saturate  the  gas  with  moisture.  Results  1  to 
4%  low  will  be  obtained  if  the  burette  is  allowed  to  become  dry,  the  amount  of 
error  depending  upon  the  temperature  of  the  gas.  One  hundred  cc.  of  dry  gas 
expand  upon  absorbing  moisture  to  101.2  cc.  at  10°;  101.7  cc.  at  15°;  102.3  cc. 
at  20°;  103.1  cc.  at  25° and  104.1  cc.  at 30°. 

Leveling  Tube.  The  covering  recommended  prevents  warming  of  the  mer- 
cury with  the  hand.  When  the  apparatus  is  kept  stationary,  practically  no 
change  of  temperature  takes  place  during  the  test  if  the  mercury  is  thus  pro- 
tected, so  that  a  temperature  correction  will  not  be  required.  If  the  apparatus 
is  moved  from  a  warm  to  cold  zone  or  vice  versa,  temperature  corrections  will 
become  necessary. 

Pipette.  The  form  of  pipette  shown  in  the  illustration  is  simple  and  com- 
pact. The  bottle  affords  both  protection  and  acts  as  a  water  jacket.  The  pipette 
is  filled  with  thin-walled  tubes  having  a  small  bore.  The  pipette  should  be  tightly 
packed  as  loose  packing  and  large-bored  tubes  both  lessen  the  efficiency  of  the 
pipette,  cutting  down  the  surface  for  absorption. 

Rubber  Tube  Connection.  Since  sulphuric  anhydride  acts  on  rubber,  in 
presence  of  this  gas,  rubber  tubing  for  connecting  the  testing  apparatus  to  the 
sampling  pipe  should  not  be  used,  except  in  flush  connections  with  the  pipe  in 
contact  with  the  inlet  tube  of  the  apparatus.  In  absence  of  sulphuric  anhydride 
the  use  of  rubber  tubing  is  not  objectionable. 

Cleaning  the  Burette  upon  Accidental  Drawing  in  of  Chromic  Acid.  Should 
the  reagent  be  accidentally  sucked  into  the  capillary  or  into  the  burette,  it  may 
be  easily  washed  out  with  distilled  water  by  drawing  this  through  stopcock  B 
and  flushing  out  several  times  by  lowering  and  raising  the  leveling  tube.  The 
excess  water  may  be  removed  from  the  capillary  by  opening  stopcock  C  and 
allowing  to  flow  out.  If  mercuric  oxide  is  formed  in  the  burette  it  may  be  dis- 
solved by  flushing  with  sodium  hydroxide  solution. 

Chromic  Acid  Reagent.  Theoretically,  a  charge  of  50%  aqueous  chromic 
acid  solution  (100  g.  Cr03+100  g.  H20)  amounting  to  300  cc.,  is  sufficient  to  absorb 
the  S02  of  over  12,000  determinations.  In  practice,  however,  the  reagent  should 
be  renewed  long  before  the  chromic  acid  has  been  used  up  by  the  sulphurous 
acid. 

Number  of  Passes.  Although  two  passes  are  generally  sufficient  to  completely 
absorb  the  S02,  it  is  necessary  to  make  a  third  pass  and  observe  whether  any 
further  contraction  takes  place.  If  the  reagent  is  effective  and  there  are  no 
leaks  in  the  apparatus  the  third  pass  will  show  no  change. 

Lubrication  of  Stopcocks.  A  mixture  of  beeswax  and  vaseline  or  wool 
grease  (1  :  2)  has  been  found  excellent  for  this  purpose.  Not  only  does  it  lubricate 
the  stopcock,  but  it  prevents  leaks.  Eighty  parts  rubber  melted  with  20  parts 
beeswax  is  also  good  and  is  acid  resisting. 

Rubber  Tube  Connections.  Coating  the  glass  tube  with  a  viscous  solution 
of  sealing  wax,  dissolved  in  alcohol,  or  etching  it  with  hydrofluoric  acid,  on  the 
portion  covered  by  the  rubber  will  make  a  tight  joint  so  that  wiring  the  joint  will 
not  be  necessary. 

Parallel  Leveling  Lines  are  placed  behind  the  burette  to  enable  more  accurate 
leveling  of  the  mercury  columns. 


726 


GAS   ANALYSIS 
(b)    Nitrogen  Oxides 


Nitrogen  tetroxide,  N204,  and  nitrous  acid,  N203,  can  best  be  determined  by 
absorption  in  standard  permanganate  (acidulated  with  sulphuric  acid)  according 
to  p.  694. 

Nitric  oxide  can  be  determined  by  passing  the  gases  through  soda  lye,  then  by 
adding  air  to  the  collected  volume,  converting  it  to  nitrogen  tetroxide  and  deter- 
mining it  as  above  indicated. 

Nitrous  oxide  is  determined  in  the  acid-free  gases  by  explosion  with  hydrogen. 

(c)  Oxygen  is  usually  determined  by  acid  or  ammoniacal  cuprous  chloride — 
phosphorus  is  also  employed.  The  percentage  of  oxygen  should  not  exceed  six; 
a  larger  amount  means  that  heat  is  being  lost  from  the  chambers  by  the  exhaust 
gases.  Knowing  their  temperature,  the  loss  of  heat  can  be  calculated  as  with 
chimney  gases. 

V.  MINE  GASES1 

The  gases  to  be  sought  are  those  found  in  illuminating  gas  and  for  most  pur- 
poses the  procedure  on  p.  704  can  be  followed.  For  small  quantities  of  methane 
the  apparatus  of  Haldane,  modified  and  described  by  Burrell  and  Seibert 2  should 
be  used.  This  is  practically  an  Orsat,  using  mercury  as  the  confining  liquid 
and  with  a  compensating  tube  and  grisoumeter  for  burning  the  methane. 

For  determination  of  methane  alone,  the  apparatus  of  Shaw  3  may  be  recom- 
mended. This  determines  first  the  per  cent  of  illuminating  gas  necessary  to  make 
an  explosion  of  definite  strength  with  ordinary  air;  when  this  has  been  done, 
mine  air  is  used  in  place  of  the  ordinary  air  and  a  smaller  percentage  of  illuminat- 
ing is  required — smaller  by  the  amount  of  combustible  gas  in  the  mine  air.  The 
strength  of  the  explosion  is  measured  by  noting  by  the  ear  the  force  with  which 
the  plunger  is  driven  out  from  the  explosion  cylinder  against  a  bell. 

In  case  this  apparatus  be  not  at  hand,  Brunck's 4  method  can  be  employed. 
This  consists  in  burning  the  methane  in  a  2-liter  Erlenmeyer  flask  by  means  of 
an  electrically  heated  platinum  spiral.  The  flask  carrying  the  spiral  in  the 
stopper  is  sunk  inverted  in  a  vessel  of  water  and  the  current  allowed  to  pass  for 
half  an  hour,  which  is  sufficient  to  burn  the  methane.  It  is  then  cooled  and 
25  cc.  Ba02H2  (1  cc.  =1  cc.  CO2)  added,  time  allowed  for  absorption  of  the  carbon 
dioxide  and  the  excess  of  Ba02H2  determined,  p.  728,  and  the  quantity  of  methane 
calculated. 

Clowes  and  Redwood 6  have  worked  out  a  method  for  the  detection  of  inflam- 
mable gas  in  air,  employing  the  "  flame  cap."  When  an  inflammable  atmosphere 
is  brought  in  contact  with  a  candle  or  better  a  hydrogen  flame,  the  gas  burns, 
forming  a  "  cap,"  like  the  colorless  flame  above  the  blue  cone  in  a  Bunsen  burner: 
the  length  of  the  flame  is  a  measure  of  the  percentage  of  gas,  and  as  little  as  0.1% 
is  visible  using  the  hydrogen  flame. 

Carbon  Monoxide.  Besides  combustible  gases  or  "  fire  damp,"  it  is  some- 
times necessary  to  get  an  idea  of  the  amount  of  carbon  monoxide  ("  white  damp  ") 

1  See  Technical  Paper  14,  Bureau  of  Mines,  "  Apparatus  for  Gas  Analysis  Labora- 
tories at  Coal  Mines." 

2  Bull.  42,  U.  S.  Bureau  of  Mines,  17,  42,  1913,  also  Technical  Paper  39,  13. 

*  Berichte,  27.  692. 

*  O.  Brunck,  "  Die  Chem.  Unters.  d.  Gruben wetter,"  1908. 

6 "  Detection  and  Estimation  of  Inflammable  Gas  and  Vapor  in  the  Air," 
also  Clowes,  J.  Soc.  Arts,  41,  307. 


GAS  ANALYSIS  727 

in  the  mine  air  after  an  explosion  or  in  the  "  after  damp  ";  chemical  methods, 
p.  704,  being  too  slow,  use  is  made  of  the  behavior  of  birds  and  mice  when  exposed 
to  such  an  atmosphere.  To  this  end  they  are  carried  in  cages  by  the  rescuing 
party  and  their  behavior  noticed.  Canaries  show  distress  in  an  atmosphere 
containing  0.15%  of  CO  in  five  to  twelve  minutes,  or  with  0.20%  in  half  this  time: 
Mice  are  less  sensitive,1  and  men  may  display  distress  when  carbon  monoxide  is  as 
little  as  0.1%,  whereas  animals  may  be  unaffected.  In  case  either  is  overcome  by 
the  gas,  resuscitation  can  be  effected  by  bringing  them  out  into  the  open  air  again. 
Repeated  exposure  of  the  gas  would  seem  to  be  without  influence. 


VI.  ELECTROLYTIC  GASES 

Gases  from  electrolytic  chlorine,  hydrogen  and  oxygen  generators.  The  follow- 
ing are  to  be  sought  for : 

(a)  Chlorine,  (6)  oxygen,  (c)  carbon  dioxide,  (d)  carbon  monoxide,  (e)  hydrogen. 

(a)  Chlorine.  Hempel 2  recommends  measuring  the  gas  quickly  in  his  burette 
over  water  and  then  sucking  in  5  cc.  of  50%  potassium  iodide  solution  through 
the  capillary  and  shaking;  the  diminution  in  volume  gives  the  chlorine. 

The  other  gases  are  determined  in  the  usual  way.  As  phosphorus  cannot  be 
used  for  pure  oxygen,  a  specially  prepared  potassium  pyrogallate,  p.  735,  is 
employed;  cuprous  chloride  or  ammoniacal  cuprous  carbonate  in  the  absence  of 
carbon  monoxide  is  very  satisfactory. 

VII.  ACETYLENE 

Commercial  acetylene  may  contain  the  following  gases: 

1.  Oxygen;  4.  Nitrogen; 

2.  Hydrogen;  5.  Sulphur-containing  gases; 

3.  Methane;  6.  Phosphine. 

Oxygen  is  estimated  after  the  absorption  of  the  acetylene  itself  in  fuming  sul- 
phuric acid,  in  the  usual  way  with  potassium  pyrogallate.  Methane  and  hydrogen 
would  be  determined  in  this  residue,  after  treatment  with  ammoniacal  cuprous 
chloride  to  complete  the  removal  of  acetylene,  by  the  ordinary  explosion  methods, 
p.  704.  Nitrogen  would  be  left  as  a  residue. 

Sulphur-containing  gases.  These  are  most  likely  organic  sulphides,  as 
hydrogen  sulphide  is  probably  absent,  since  the  solution  is  strongly  alkaline  from 
which  the  acetylene  escapes.  They  can  be  determined  by  combustion,  as  in  illu- 
minating gas,  p.  716,  and  best  be  reported  as  "  total  sulphur." 

Phosphine  is  also  similarly  estimated  and  the  phosphoric  acid  determined  in 
the  usual  way:  the  quantity  of  PH3  rarely  exceeds  0.05%.  Acetylene  can  be 
purified  by  passing  over  bleaching  powder,  through  acid  cuprous  chloride  or 
chromic  acid:  The  candle  power  is  usually  given  as  fifty  per  cubic  foot,  or  180-200, 
when  burned  at  the  rate  of  5  cu.ft.  per  hour.  The  explosive  limits  are  according 
to  Clowes  3  3  to  82%. 

1  Burrell,    Seibert   and  Robertson,    Bureau   of   Mines  Technical  Paper  62,  1914i 
"  Relative  Effects  of  Carbon  Monoxide  on  Small  Animals." 

2  "  Gas-Analytische  Methoden,"  4th  Ed.,  1913,  p.  278. 

3  Op.  cit. 


728 


GAS  ANALYSIS 


VIII.  ATMOSPHERIC  AIR 

(a)  Moisture;  (6)  Carbon  dioxide;  (c)  Ozone;  (d)  Carbon  monoxide;  (e) 
Bacteria. 

(a)  Moisture  1  by  chemical  means,  see  p.  731.    The  amount  of  moisture  can 
be  determined  by  the  sling  psychrometer,  or  wet-  and  dry-bulb  thermometer  or 
by  the  hair  hygrometer.    The  sling  psychrometer  is  the  most  rapid  and  accurate — 
the  wet-  and  dry-bulb  thermometers  are  so  arranged  that  they  can  be  rapidly 
whirled  for  fifteen  or  twenty  seconds,  stopped  and  quickly  read,  the  wet  bulb 
first;  this  is  repeated  until  closely  agreeing  readings  are  obtained.    The  humidity 
is  determined  in  the  usual  manner  from  the  meteorological  tables. 

The  amount  of  moisture  in  the  air  is  probably  indirectly  responsible  for  our 
sensations  of  comfort  or  discomfort,  rather  than  the  amount  of  carbon  dioxide, 
as  was  formerly  thought.  This  moisture  controls  the  heat  loss  from  the  body, 
which  loss  must  be  normal — neither  too  high  nor  too  low.  The  greater  the 
humidity  the  less  the  evaporation,  consequently  the  less  the  cooling. 

For  comfort,  the  higher  the  temperature  the  less  should  be  the  humidity; 
the  following  shows  the  relation  between  the  two: 

Temp.,°F 60  68 '         70  80  90 

Relative  humidity,  per  cent    67  40  49  31  16 

(b)  Carbon  Dioxide.    One  of  the  most  satisfactory  methods  is  that  of  Hesse.' 
This  consists  in  absorbing  the  carbon  dioxide  from  a  definite  volume  of  air  with 

standard  barium  hydroxide  and  determining  its 
loss  of  strength. 

The  air  is  collected  in  heavy  Erlenmeyer  flasks 
of  100-500  or  1000  cc.  capacity,  or  clear  glass 
bottles;  these  are  stoppered  with  doubly  per- 
forated rubber  stoppers  carrying  glass  plugs  and 
the  capacity  of  the  flask  or  bottle  noted  to  the 
depth  of  the  stopper.  A  10-cc.  pipette  and  a 
15-cc.  glass-stoppered  burette  graduated  in  cc./lO 
with  an  8-cm.  tip,  complete  the  outfit;  a  solution 
of  1.7  grams  of  barium  hydroxide  and  chloride 
(20  :  1)  in  a  liter  of  water,  B  Fig.  132,  and  of 
oxalic  acid  5.6325  grams  per  liter  (1  cc.  =1  cc. 
C02),  with  phenolphthalein  1  :  250,  are  required. 
The  bottles  are  filled  with  steam  by  exposure 
for  three  minutes  and  the  vaselined  stoppers  in- 
serted, or  they  may  be  filled  with  distilled  water 
and  opened  in  the  place  the  air  of  which  is  to  be 
examined. 

In  all  this  work,  it  should  be  remembered  that  the  exhaled  breath  contains 
from  30  to  40  parts  carbon  dioxide  per  10,000,  consequently  care  should  be  taken 
not  to  contaminate  the  samples,  nor  should  they  be  warmed  with  the  hand. 

1  Benedict,  "  The  Composition  of  the  Atmosphere  with  Special  Reference  to  il 
Oxygen  Content,"  Carnegie  Institution  of  Washington,  1912,  Publication  No.  166. 
1  For  indoor  work. 
1  Eulenberg's  Vierteljahrschr.  f .  ger.  Med.  u.  San.  N.  F.,  31,  2. 


FIG.  132. 


GAS  ANALYSIS  729 

The  10-cc.  pipette  is  partly  filled  from  the  tube  A,  Fig.  132,  by  means  of  the 
rubber  connector  and  sucking  the  liquid  into  the  pipette:  it  is  rinsed,  filled  and 
inserted  through  one  of  the  holes  in  the  rubber  stopper  of  the  bottle,  the  other 
plug  being  momentarily  opened.  The  plugs  are  replaced  and  the  bottles  allowed 
to  rest  on  their  sides,  with  occasional  rolling,  for  twenty  minutes.  Not 
more  than  one-fifth  of  the  solution  should  be  used  up  by  the  carbon  dioxide 
present. 

During  this  time,  the  barium  hydroxide  should  be  standardized;  to  this  end 
a  few  drops  of  phenolphthalein  and  a  quantity  of  the  oxalic  acid  almost  sufficient 
to  neutralize  the  hydroxide  should  be  run  into  a  100-cc.  Erlenmeyer  flask  from  the 
burette;  this  should  be  passed  through  the  doubly  perforated  stopper;  10  cc.  of 
the  barium  hydroxide  solution  are  run  into  the  flask  as  above  described,  and  also 
the  oxalic  acid  until  a  pink  color  appears. 

Phenolphthalein  is  added  to  the  bottle's  containing  the  samples,  the  oxalic 
acid  burette  inserted  through  the  stopper  and  the  excess  of  barium  hydroxide 
titrated. 

The  barometric  pressure  and  temperature  in  the  laboratory  are  noted  and 
the  volume  of  the  bottle  less  10  cc.  (Ba02H2)  calculated  to  standard  conditions; 
the  difference  in  the  titer  of  the  barium  hydroxide  solution  gives  the  volume  of 
carbon  dioxide  in  the  bottle;  this  is  calculated  into  parts  per  10,000. 

Other  methods  for  this  determination  are  more  strictly  gasometric,  measuring 
the  diminution  in  volume  by  absorption :  Benedict l  used  Sonden's,  and  Anderson 2 
recommends  a  shortened  form  of  the  Pettersson-Palmquist  apparatus. 

This  may  be  described  as  an  Orsat  apparatus  using  mercury  instead  of  water 
and  with  a  25-cc.  burette  the  lower  part  of  which  is  graduated  to  0.0025  cc.;  this 
is  connected  to  a  pipette  of  potassium  hydroxide,  a  delicate  manometer  and  com- 
pensating tube.  The  apparatus  is  delicate  and  rapid,  but  requires  a  skilled 
operator  to  manipulate  it. 

The  amount  of  carbon  dioxide  in  the  outdoor  air  in  the  city  is  about  3.1  parts 
per  10,000,  in  the  house,  3.7-3.9;  with  6-7  parts  in  a  room,  the  ventilation  may 
be  considered  as  excellent,  with  10  parts  as  about  the  upper  limit.  In  some 
theaters  which  were  lighted  by  gas  it  approached  50  parts. 

(c)  Ozone.    Probably  most  conveniently  determined  by  Wurster's  method, 
p.  697. 

(d)  Carbon  Monoxide.    The  qualitative  detection  is  most  certainly  effected 
by  the  blood  test;  to  this  end  the  gas  is  drawn  through  a  solution  of  blood  con- 
ained  in  a  Wolff,  Fig.  118,  or  similar  absorption  tube  and  examined  for  its  absorp- 
tion spectrum.    The  blood  solution  is  made  by  mixing  ox  blood  which  has  been 
defibrinated  by  whipping,  with  an  equal  quantity  of  a  cold  saturated  solution  of 
borax;  this  can  be  kept  (as  a  side-shelf  reagent)  in  the  laboratory  for  months. 
This  solution  is  diluted  with  19  volumes  of  water,  giving  a  solution  of  blood  of 
1  in  40  which  is  placed  in  the  absorption  tube.    The  air  is  drawn  through  it  at 
a  rate  of  3  liters  per  hour,  requiring  10  liters  in  some  cases;  the  solution  is  put 
a  thin  flat-sided  bottle  and  spectroscopically  examined. 

Pure  diluted  blood,  Fig.  133,  shows  two  dark  absorption  bands,  spectrum  2, 
between  the  D  and  E  line ;  these  are  welded  into  one  broad  band  by  reducing  agents 
as  NH4SH,  spectrum  4;  blood  which  has  absorbed  carbon  monoxide  shows  two 

1  Op.  cit. 

2  J.  Am.  Chem.  Soc.,  35, 162, 1913. 


730 


GAS  ANALYSIS 


broader  bands  in  the  same  place,  spectrum  3,  which  are  unaffected  by  reducing 
agents.  The  quantitative  determination  depends  upon  the  equation, 

5CO+I2Oa=5C02+I2. 

This  has  been  studied  by  Kinnicutt  and  Sanford  1  and  recently  by  Morgan  and 
McWhorter2  and  by  the  writer.  The  process  consists  in  sucking  the  air  through 
the  iodine  pentoxide  contained  in  a  U-tube  heated  in  cottonseed  oil  or  glycerin 
bath  to  150°,  passing  the  iodine  into  potassium  iodide  solution  and  then  absorbing 

the  carbon  dioxide  in  standard  barium 
hydroxide.  Both  the  iodine  and  bar- 
ium hydroxide  solutions  are  titrated. 
The  last  two  investigators  call  par- 
ticular attention  to  the  ease  with 
which  iodine  pentoxide  at  150°  is 
decomposed  by  organic  matter,  par- 
ticularly stopcock  grease;  the  pen- 
toxide should  be  sealed  into  the 
U-tube,  as  glass  stopcocks  cannot  be 
used.  The  writer  can  substantiate 
this  statement,  and  would  suggest 
further  that  the  U-tube  be  chemically 
H^SO^  before  filling  with  I206,  as  well 
as  the  tubes  through  which  the  gas  is  sucked  before  reaching  the  U-tube;  rubber 
connections  should,  if  possible,  be  avoided,  and  the  tubing  should  have  been 
cleansed  by  warming  with  dilute  soda  lye  and  washing.  The  U-tube  should  be 
drawn  down  to  the  same  size  as  the  connecting  glass  tubing  and  the  two  butted 
closely  together  in  the  cleansed  rubber  connector. 

The  iodine  is  titrated  with  N/1000  thiosulphate  and  every  2.27  mg.  of  iodine 
corresponds  to  1  cc.  of  carbon  monoxide  under  standard  conditions;  the  carbon 
dioxide  is  absorbed  in  the  hydroxide  contained  in  a  long  test-tube  24X2.5  cm.  and 
titrated  with  oxalic  acid  (1.1265  grams  crystallized  acid  to  1  liter)  using  phenolph- 
thalein;  5  cc.  of  the  acid  are  equivalent  to  1  cc.  of  carbon  dioxide. 

Haldane3  states  that  as  little  as  .01%  of  carbon  monoxide  can  be  determined 
colorimetrically  by  absorbing  in  diluted  blood  and  comparing  it  with  standard 
carmine  solution;  carbon  monoxide  turns  the  brownish  yellow  color  of  the  blood 
to  pink. 

(e)  Bacteria.  See  "  Standard  Methods  for  Bacterial  Examination  of  Air." 
Am.  J.  Pub.  Health,  6,  No.  3,  1910. 

1  J.  Am.  Chem.  Soc.,  22,  14,  1900. 

2  Ibid.,  29,  1589,  1907. 
8  Clowes,  op.  cit.,  138. 


FIG.  133. 
cleaned  with  cleaning  solution 


GAS   ANALYSIS 


731 


FIG.  134. 


THREE  WAY 


DETERMINATION   OF  MOISTURE    IN   GASES 

The  gas  to  be  tested  is  passed  through  a  dehydrating  agent  such  as  phosphorus 
pentoxide,  P205,  alumina,  A1203,  or  lime,  CaO,  contained  in  a  weighed  U-tube, 
Fig.  134.  The  following  facts  should  be  borne  in  mind  in 
selecting  the  dehydrating  agent :  (a)  It  should  not  absorb 
the  gas;  (6)  it  should  not  react  chemically  with  the  gas. 
For  example — lime  or  alumina  could  not  be  used  for 
determining  moisture  in  sulphur  dioxide,  nor  could  phos- 
phorus pentoxide  be  used  in  determining  moisture  in 
ammonia.  For  the  former,  phosphorus  pentoxide  is  best, 
and  for  the  latter,  lime.  Alumina  that  has  been  care- 
fully heated  to  1400°  is  useful  for  determining  moisture 
in  neutral  gases.  It  should  be  remembered  that  gases 
dried  over  calcium  chloride  will  give  up  moisture  to 
strong  sulphuric  acid,  and  these  in  turn  will  give  up 
moisture  to  phosphorus  pentoxide:  Professor  Morley  has  even  determined  the 
amount  of  moisture  that  is  left  after  this  latter  treatment. 

Procedure.  The  volume  of  the  gases  required  for  the  test  varies  widely 
according  to  the  percentage  of  moisture  in  the  gas,  1000  cc.  to 
10,000  cc.  are  generally  required.  For  minute  amounts  of  moist- 
ure it  may  be  necessary  to  lead  the  gas  over  the  dehydrating 
agent  for  a  given  length  of  time,  using  a  manometer  or  differ- 
ence gauge,  or  a  gas  meter.  The  absorption  tube  is  weighed 
before  and  after  the  test  and  the  increase  in  weight  taken  as  the 
moisture  content  of  the  gas. 

Method  of  Determining  Gasolene  Vapor  in  Gaseous 
Mixtures.1  Fig.  135  shows  the  apparatus  for  the  gasolene-vapor 
determination.  The  bulb  a  contains  phosphorus  pentoxide  for 
removing  water  vapor.  If  the  latter  were  not  removed  it  would 
also  be  retained  at  low  temperatures  and  would  subsequently 
exert  pressure  when  measurement  was  being  made  of  the  pres- 
sure exerted  by  the  gasolene  vapor. 

To  start  a  determination  the  apparatus  is  connected  to  a 
vacuum  pump  and  its  air  exhausted.  The  mixture  of  gasolene 
vapor  and  air  is  then  introduced  at  atmospheric  pressure,  the 
barometer  is  read,  and  the  two  bulbs  are  immersed  in  liquid  air 
contained  in  a  Dewar  flask.  After  about  ten  minutes,  the  air  is 
removed  from  the  apparatus  with  a  vacuum  pump.  The  stop- 
cock on  the  apparatus  is  then  closed,  the  liquid  air  in  the 
Dewar  flask  removed,  the  gasolene  allowed  to  vaporize,  and  its 
pressure  read  on  the  mercury  manometer  attached  to  the  appa- 
ratus. The  ratio  of  this  pressure  to  the  pressure  of  the  atmos- 
phere gives  the  percentage  of  gasolene  vapor  originally  in  the  air. 


FIG.  135. 


U.  S.  Bureau  of  Mines,  Technical  Paper  No.  115,  Burrell  and  Boyd. 


732 


GAS  ANALYSIS 


DETERMINATION  OF  NITROGEN  BY  THE  NITROMETER1 

The  nitrometer,  Fig.  136,  consists  of  a  gas-generating  bulb  fitted  at  the  top 
with  a  two-way  cock  leading  to  a  dissolving  cup  and  a  gas-exit  tube,  and  which 
has  at  the  bottom  a  connection  for  a  rubber  tube  leading  to  a  leveling  tube,  the 
whole  being  filled  with  mercury  to  a  level  just  below  the  upper  cock;  a  cylindrical 
glass  measuring  tube  graduated  from  0-100  cc.  connected  to  a  leveling  tube  through 


Holde 
Gas  Generating  Bulbj 


Clomp 


FIG.  136. 

a  T-tube  leading  to  an  equilibrium  tube.  The  latter  is  shaped  like  an  inverted 
100-cc.  pipette  graduated  downward  below  the  bulb  from  100-130  cc.  The  whole 
system  is  filled  with  mercury  so  that  the  measuring  tube  may  be  completely  dis- 
charged by  raising  the  leveling  tube. 

Adjusting  the  Equilibrium  Tube.  The  volume  of  100  cc.  of  dry  ah-  at  0°  C. 
and  760  mm.  under  the  temperature  and  barometric  conditions  prevailing  at  the 
time  is  calculated,  3  drops  of  98%  sulphuric  acid  are  drawn  into  the  tube  and 
the  level  of  the  mercury  fixed  in  accordance  with  the  calculation.  The  cock  of 
the  tube  is  then  closed  and  sealed  with  melted  paraffin.  The  volume  in  this  tube 
may  be  confirmed  at  any  time  by  opening  the  measuring  tube  and  adjusting 
the  leveling  tube  so  that  the  level  is  the  same  in  the  three  tubes.  The  volume  of 
gas  in  the  equilibrium  tube  is  then  read  and  compared  with  the  calculated  volume 

1  Joyce  and  La  Tourette,  J.  Ind.  and  Eng.  Chem.  5,  1017,  1913. 


GAS  ANALYSIS 


733 


at  the  time,  a  correction  in  the  subsequent  gas  readings  in  the  measuring  tube 
being  made  accordingly. 

Nitrogen  in  Potassium  Nitrate.  Approximately  0.4  gram  potassium  nitrate 
is  placed  in  a  weighing  tube,  dried  two  hours  at  110°  C.,  desiccated  twenty-four 
hours  over  sulphuric  acid  and  weighed  exactly  by  difference  into  the  cup  of  the 
gas-generating  bulb.  This  is  dissolved  in  9  cc.  95%  sulphuric  acid,  added  through 
a  siphon,  thistle  tube,  entering  the  top  of  the  dissolving  cup  through  a  tight-fitting 
rubber  stopper.  When  the  salt  is  dissolved  it  is  drawn  into  the  gas-generating 
bulb  and  followed  by  two  washings  1.5  cc.  each  of  95%  acid.  The  bulb  is  then 
shaken,  with  a  motion  normal  to  its  long  dimension  until  the  volume  of  gas  deter- 
mined by  a  rough  paper  scale  pasted  on  the  leveling  tube  becomes  constant,  this 
operation,  taking  from  three  to  five  minutes. 

The  gas  is  passed  into  the  measuring  tube,  and  after  standing  five  minutes  the 
leveling  and  measuring  tubes  are  so  adjusted  that  the  level  in  the  equilibrium  tube 
reads  100  cc.  and  is  the  same  as  the  level  in  the  measuring  tube.  The  reading  of 
the  latter  is  then  taken.  As  the  temperature  and  barometric  conditions,  in  so  far 
as  they*  affect  the  measured  volume  of  the  gas,  are  automatically  compensated 
by  the  equilibrium  tube,  and  as  the  gas  is  washed  with  sulphuric  acid  and  is,  there- 
fore, dry,  the  percentage  of  nitrogen  may  be  calculated  directly,  correcting  only 
for  the  calibration  of  the  equilibrium  and  measuring  tubes.  Seventeen  deter- 
minations made  when  the  room  temperature  ranged  from  20-28°  gave  13.71% 
nitrogen,  the  theoretical  being  13.84%. 

The  nitrometer  gives  reliable  results  within  0.02%  in  nitrate  nitrogen,  using 
0.4-0.5  gram  sample.  It  is  not  available  for  the  determination  of  nitrogen  in 
celluloid  or  other  substances  containing  carbon  ring  compounds  which  appear 
to  prevent  the  complete  liberation  of  nitric  oxide  in  the  presence  of  sulphuric 
acid  and  mercury. 

Besides  the  corrections  for  calibration  and  standardization  of  the  nitrometer 
in  accordance  with  temperature  and  barometer,  the  gas  readings  should  be  cor- 
rected for  solubility  of  nitric  oxide,  which  diminishes  when  the  temperature  goes 
above  28°  C.,  and  the  formation  of  other  gases  by  the  breaking  up  of  the  cellulose 
molecule  which  increases. 

The  following  table  gives  the  algebraic  sum  of  these  two  corrections  for  tem- 
peratures ranging  from  20°  to  35°  C. 


Temp. 

Cc. 

Temp. 

Cc. 

20.0-27.5 
28.0 
29.0 

+0.90 
+0.74 
+0.34 

30.0 
30.5 
31.0-35.0 

-0.14 
-0.70 
-0.94 

734  GAS   ANALYSIS 


REAGENTS  AND  TABLES 

The  reagents  used  in  gas  analysis,  particularly  in  the  absorption  apparatus, 
are  comparatively  few  and  easily  prepared. 

Hydrochloric  Acid,  Sp.  gr.  1.10.  Dilute  "  muriatic  acid  "  with  an  equal 
volume  of  water.  In  addition  to  its  use  for  preparing  cuprous  chloride,  it  finds 
employment  in  neutralizing  the  caustic  solutions  which  are  unavoidably  more 
or  less  spilled  during  their  use. 

Fuming  Sulphuric  Acid.  Saturate  "  Nordhausen  oil  of  vitriol "  with  sul- 
phuric anhydride.  Ordinary  sulphuric  acid  may  be  used  instead  of  the  Nord- 
hausen; in  this  case  about  an  equal  weight  of  sulphuric  anhydride  will  be  necessary. 
Absorption  capacity,  1  cc.  absorbs  8  cc.  of  ethene  (ethylene). 

Acid  Cuprous  Chloride.  The  directions  given  in  the  various  text-books 
being  troublesome  to  execute,  the  following  method,  which  is  simpler,  has  been 
found  to  give  equally  good  results:  Cover  the  bottom  of  a  two-liter  bottle  with 
a  layer  of  copper  oxide  or  "  scale  "  f  in.  deep,  place  in  the  bottle  a  number  of 
pieces  of  rather  stout  copper  wire  reaching  from  top  to  bottom,  sufficient  to  make 
a  bundle  an  inch  in  diameter,  and  fill  the  bottle  with  common  hydrochloric  acid 
of  1.10  sp.gr.  The  bottle  is  occasionally  shaken,  and  when  the  solution  is  color- 
less, or  nearly  so,  it  is  poured  into  the  half-liter  reagent  bottles,  containing  copper 
wire,  ready  for  use.  The  space  left  in  the  stock  bottle  should  be  immediately 
filled  with  hydrochloric  acid  (1.10  sp.gr.). 

By  thus  adding  acid  or  copper  wire  and  copper  oxide  when  either  is  exhausted, 
a  constant  supply  of  this  reagent  may  be  kept  on  hand. 

The  absorption  capacity  of  the  reagent  per  cc.  is,  according  to  Winkler,  15  cc. 
CO;  according  to  Hempel  4  cc.  The  author's  experience  with  Orsat's  apparatus 
gave  1  cc. 

Care  should  be  taken  that  the  copper  wire  does  not  become  entirely  dissolved 
and  that  it  extend  from  the  top  to  the  bottom  of  the  bottle;  furthermore  the 
stopper  should  be  kept  thoroughly  greased  the  more  effectually  to  keep  out  the 
air,  which  turns  the  solution  brown  and  weakens  it. 

Ammoniacal  Cuprous  Chloride.  The  acid  cuprous  chloride  is  treated  with 
ammonia  until  a  faint  odor  of  ammonia  is  perceptible;  copper  wire  should  be 
kept  in  it  similarly  to  the  acid  solution.  This  alkaline  solution  has  the  advantage 
that  it  can  be  used  when  traces  of  hydrochloric  acid  vapors  might  be  harmful  to 
the  subsequent  determinations,  as,  for  example,  in  the  determination  of  hydrogen 
by  absorption  with  palladium.  It  has  the  further  advantage  of  not  soiling 
mercury  as  does  the  acid  reagent. 

Absorption  capacity,  1  cc.  absorbs  1  cc.  CO. 

Cuprous  chloride  is  at  best  a  poor  reagent  for  the  absorption  of  carbonic  oxide; 
to  obtain  the  greatest  accuracy  where  the  reagent  has  been  much  used,  the  gas 
should  be  passed  into  a  fresh  pipette  for  final  absorption,  and  the  operation  con- 
tinued until  two  consecutive  readings  agree  exactly.  The  compound  formed  by 
the  absorption — possibly  Cu2COCl2 — is  very  unstable,  as  carbonic  oxide  may  be 
freed  from  the  solution  by  boiling  or  placing  it  in  vacuo;  even  if  it  be  shaken  up 
with  air,  the  gas  is  given  off,  as  shown  by  the  increase  in  volume  and  subsequent 
diminution  when  shaken  with  fresh  cuprous  chloride. 

Hydrogen.  A  simple  and  effective  hydrogen  generator  can  be  made  by 
joining  two  G-in.  calcium  chloride  jars  by  their  tubulatures.  Pure  zinc  is  filled 


GAS   ANALYSIS  735 

in  as  far  as  the  constriction  in  one,  and  the  mouth  closed  with  a  rubber  stopper 
carrying  a  capillary  tube  and  a  pinchcock.  The  other  jar  is  filled  with  sulphuric 
acid  1  :  5  which  has  been  boiled  and  cooled  out  of  excess  of  air.  The  mouth  of 
this  jar  is  closed  with  a  rubber  stopper  carrying  one  of  the  rubber  bags  used  on 
the  simple  f)ipettes. 

Mercury.  The  mercury  used  in  gas  analysis  should  be  of  sufficient  purity 
as  not  to  "  drag  a  tail "  when  poured  out  from  a  clean  vessel.  It  may  perhaps 
be  most  conveniently  cleaned,  except  from  gold  and  silver,  by  the  method  of 
J.  M.  Crafts,  which  consists  in  drawing  a  moderate  stream  of  air  through  the  mer- 
cury contained  in  a  tube  about  3  ft.  long  and  1|  ins.  internal  diameter.  The  tube 
is  supported  in  a  mercury-tight  V-shaped  trough,  of  size  sufficient  to  contain  the 
metal  if  the  tube  breaks,  one  end  being  about  3  ins.  higher  than  the  other.  Forty- 
eight  hours'  passage  of  air  is  sufficient  to  purify  any  ordinary  amalgam.  The 
mercury  may  very  well  be  kept  in  a  large  separatory  funnel  under  a  layer  of 
strong  sulphuric  acid. 

Or  Meyer's  method  l  may  be  used.  A  separatory  funnel  is  used  to  hold  the 
mercury.  The  delivery  tube  of  the  funnel  is  slightly  narrowed  0.5  cm.  from  the 
lower  end.  Over  this  side  is  bound  with  twine  a  piece  of  rather  closely  woven 
muslin.  The  mercury  is  allowed  to  flow  through  the  cloth  into  a  solution  of 
mercury  nitrate  contained  in  a  tall  cylinder,  with  stopcock  at  the  lower  end. 
The  tip  of  the  funnel  with  the  muslin  dips  under  the  surface  of  the  cleaning 
solution.  The  purified  mercury  is  drained  off  from  the  bottom  of  the  cylinder. 
It  can  also  be  purified  except  from  traces  of  zinc  by  distillation. 

Palladous  Chloride.  Five  grams  palladium  wire  are  dissolved  in  a  mixture 
of  30  cc.  hydrochloric  and  2  cc.  nitric  acid,  this  evaporated  just  to  dryness  on  a 
water  bath,  redissolved  in  5  cc.  hydrochloric  acid  and  25  cc.  water,  and  warmed 
until  solution  is  complete.  It  is  diluted  to  750  cc.  and  contains  about 
1%  of  palladous  chloride.  It  will  absorb  about  two-thirds  of  its  volume  of 
hydrogen. 

Phosphorus.  Use  the  ordinary  white  phosphorus  cast  in  sticks  of  a  size 
suitable  to  pass  through  the  opening  of  the  tubulated  pipette. 

Potassium  Hydrate,  (a)  For  carbon  dioxide  determination,  500  grams  of 
the  commercial  hydrate  are  dissolved  in  1  liter  of  water. 

Absorption  capacity.     One  cc.  absorbs  40  cc.  C02. 

(6)  For  the  preparation  of  potassium  pyrogallate  for  special  work,  120  grams 
of  the  commercial  hydrate  are  dissolved  in  100  cc.  of  water. 

Potassium  Pyrogallate.  Except  for  use  with  the  Orsat  or  Hempel  apparatus, 
this  solution  should  be  prepared  only  when  wanted.  The  most  convenient  method 
is  to  weigh  out  5  grams  of  the  solid  acid  upon  a  paper,  pour  it  into  a  funnel  inserted 
in  the  reagent  bottle,  and  pour  upon  it  100  cc.  of  potassium  hydrate  (a)  or  (6). 
The  acid  dissolves  at  once,  and  the  solution  is  ready  for  use. 

If  the  percentage  of  oxygen  in  the  mixture  does  not  exceed  28,  solution  (a) 
may  be  used;2  if  this  amount  be  exceeded,  (6)  must  be  employed.  Otherwise 
carbonic  oxide  may  be  given  off  even  to  the  extent  of  6%. 

Attention  is  called  to  the  fact  that  the  use  of  potassium  hydrate  purified  by 
alcohol  has  given  rise  to  erroneous  results. 

Absorption  capacity.    One  cc.  absorbs  2  cc.  0. 

1  J.  H.  Hilderbrand,  J.  Am.  Chem.  Soc.,  31,  934. 

2  Clowes,  Jour.  Soc  Chem.  Industry,  15,  170. 


736 


GAS  ANALYSIS 


Sodium  Hydrate.  Dissolve  the  commercial  hydrate  in  three  times  its  weight 
of  water.  This  may  be  employed  in  all  cases  where  solution  (a)  of  potassium 
hydrate  is  used.  The  chief  advantage  in  its  use  is  its  cheapness.  Sodium 
pyrogallate  is,  however,  a  trifle  slower  in  action  than  the  corresponding  potas- 
sium salt. 

TABLE  1 

TABLE  SHOWING  THE  TENSION  OF  AQUEOUS  VAPOR  AND  'ALSO  THE  WEIGHT  IN  GRAMS 
CONTAINED  IN  A  CUBIC  METER  OP  AIR  WHEN  SATURATED 

From  5°  to  30°  C. 


Temp. 

Tension, 
mm. 

Grams. 

Temp. 

Tension, 
mm. 

Grams. 

Temp. 

Tension, 
mm. 

Grams. 

5 

6.5 

6.8 

14 

11.9 

12.0 

23 

20.9 

20.4 

6 

7.0 

7.3 

15 

12.7 

12.8 

24 

22.2 

21.5 

7 

7.5 

7.7 

16 

13.5 

13.6 

25 

23.6 

22.9 

8 

8.0 

8.1 

17 

14.4 

14.5 

26 

25.0 

24.2 

9 

8.5 

8.8 

18 

15.4 

15.1 

27 

26.5 

25.6 

10 

9.1 

9.4 

19 

16.3 

16.2 

28 

28.1 

27.0 

11 

9.8 

10.0 

20 

17.4 

17.2 

29 

29.8 

28.6 

12 

10.4 

10.6 

21 

18.5 

18.2 

30 

31.5 

29.2 

13 

11.1 

11.3 

22 

19.7 

19.3 

Moisture  in  the  Air.1  Twenty  tests  made  On  different  days  extending  from  October 
17th  to  November  10th,  1916,  at  a  period  agreeing  closely  with  the  average  atmospheric 
conditions,  gave  results  varying  from  0.1510  gram  to  0.5031  gram  water  vapor  per 
standard  cubic  foot.  The  average  of  the  results  was  0.2469  gram  moisture  per  cubic  foot 
of  air.  Omitting  three  rainy  days  of  this  period  the  average  moisture  of  the  air  in  the 
laboratory  (75°  F.)  was  found  to  be  0.2141  gram  per  cubic  foot. 

It  is  an  interesting  fact  that  at  75°  F.,  52  per  cent  sulphuric  acid  (recommended  as  a 
standard)  is  in  equilibrium  with  air  containing  0.2137  gram  moisture  per  cubic  foot, 
according  to  an  average  of  results  by  W.  W.  Scott  and  a  calculation  from  Sorel's  table 
on  tension  of  aqueous  vapor  in  mixtures  of  sulphuric  acid  and  water. 


TABLE  2 
SPECIFIC  HEATS  OF  GASES  AT  CONSTANT  VOLUME 

Volumetric.8 

Air 0.243  0.019 

Carbon  dioxide 0.234  0.027 

Carbonic  oxide 0 . 245  0 . 019 

Hydrogen 3.41  0.019 

"  Illuminants  " 0.4043  0.040 

Methane 0.593  0.027 

Nitrogen 0.244  0.019 

Oxygen 0.217  0.019 

Aqueous  vapor 0 . 480     

The  "  volumetric  "  specific  heat  is  the  quantity  of  heat  necessary  to  raise  the  tem- 
perature of  1  cu.ft.  of  gas  from  32°  F.  to  33°  F. 

1  Communicated  by  W.  W.  Scott. 

8  H.  L.  Payne,  Jour.  Anal,  and  Applied  Chem.,  7,  233. 

•Ethylene. 


GAS  ANALYSIS 


737 


TABLE    3 

CALORIFIC  POWER  OP  VARIOUS  GASES  l    IN  BRITISH  THERMAL  UNITS  PER  CUBIC 

FOOT 


Name. 

Symbol. 

60°  F.  Initial. 

32°  F.  Initial. 
32°  F.  Final. 

Ignition 
Point  °F. 

Hydrogen  

H2 

326  2 

345  4 

1085  4 

Carbonic  oxide 

CO 

323  5 

341  2 

1200  4 

Methane 

CH4 

1009  2 

1065  0 

1230 

Illuminants  2 

2000  0 

Ethane. 

C2H6 

1764  4 

1861  0 

1140 

Propane. 

C3H8 

2521 

2657  0 

1015 

Butane.  ...         .       .       .    . 

3274 

3441  0 

Pentane  

4255  0 

Hexane  3  

5017  0 

1400 

Ethylene  

C2H, 

1588 

1674  0 

1010  4 

Propylene 

C3H6 

2347  2 

2509  0 

940 

Benzene. 

C6H6 

3807  4 

4012  0 

Acetylene  

C2H2 

1476.7 

1477.0 

788  4 

1  cubic  inch    =  16 . 39  cc. 
1  cubic  foot    =  28 . 3 1 5  liters 
1  cubic  meter  =  35. 31  cu.ft. 


TABLE  4 

1  calorie  =  3 . 969  B.t.u, 
1  pound  =  453 . 59  grams 


1  H.  L.  Payne,  loc.  cit. 

2  Where  the  ' '  illuminants  "  are  derived  chiefly  from  the  decomposition  of  mineral 
oil. 

3  The  chief  constituent  of  the  "  gasolene  "  used  in  the  gas  machines  for  carbureting 
air. 

4  Dixon  and  Coward,  Proc.  Chem.  Soc.,  26,  67. 


738 


GAS   ANALYSIS 


FURNACE   METHODS  OF  ASSAYING   FOR 
GOLD  AND  SILVER 

WALLACE  G.  DERBY  l 

THE  SAMPLE 

The  unit  of  weight  in  assaying  all  classes  of  material  except  gold  and  silver 
bullion  is  the  assay  ton,  29166.6  milligrams;  the  same  number  of  milligrams  as 
there  are  ounces  troy  in  a  ton  of  2000  avoirdupois  pounds.  If  one  A.T.  of  material 
be  taken  for  assay,  the  number  of  milligrams  gold  or  silver  obtained  represents 
ounces  per  ton  and  is  so  designated  in  reports.  In  the  assay  of  all  classes  of  bullion 
except  copper  and  lead,  results  are  calculated  to  and  reported  in  terms  of  parts 
per  thousand.  Synonymous  with  parts  per  thousand  are  the  terms  fine,  fineness, 
parts  or  degrees  fineness. 

The  sample  received  by  the  assayer  should  not  only  be  representative  of  the 
material  undergoing  valuation  or  investigation,  but  should  be  in  such  a  state  that 
the  operator  can,  without  extraordinary  manipulation  or  precaution,  weigh  out 
portions  which  are  exactly  like  the  sample.  As  a  general  rule  no  sample  of  pul- 
verized material  should  have  a  fineness  of  less  than  80  mesh.  With  increase  of 
value  or  decrease  of  proportion  of  the  constituent  of  the  material  which  carries 
the  values,  the  fineness  should  be  increased  to  100,  120  or  even  200  mesh,  unless 
the  attempt  to  obtain  such  homogeneity  is  accompanied  by  introduction  of  so  much 
matter  worn  from  the  grinding  mill  or  plate,  or  by  change  of  weight  due  to  oxida- 
tion of  some  constituent,  as  to  decrease  rather  than  increase  the  representative 
character  of  the  assay  portions.  The  sample  of  material  which  is  composed  of 
particles  very  unlike  in  value  and  so  dissimilar  in  such  physical  properties  as  size, 
weight,  magnetism,  hardness,  etc.,  which  make  separation  practicable,  should 
be  presented  to  the  assayer  in  fractions  representative  of  the  components.  A 
convenient  rule  (an  algebraical  contraction  of  the  arithmetical  operation),  for 
calculating  the  assay  of  the  whole  from  the  assays  of  the  components  which  for 
convenience  will  be  called  coarse  and  fine,  may  be  stated  as  follows:  Multiply 
the  difference  of  the  assays  of  the  coarse  and  fine  by  the  decimal  fraction  represent- 
ing the  percentage  of  fine  in  the  material  and,  if  the  assay  of  the  fine  is  greater  than 
that  of  the  coarse,  add  the  product  to  the  assay  of  the  coarse;  but  if  the  assay  of 
the  fine  is  less  than  that  of  the  coarse,  subtract  the  product  from  the  assay  of  the 
coarse.  To  a  known  weight  of  some  sorts  of  material,  during  the  process  of 
sampling,  reagents  are  added  to  neutralize  and  dry  acid  substances  or  water  is  added 
to  prevent  dusting  of  light  and  fine  substances.  To  calculate  the  assay  to  original 
basis;  multiply  by  1  plus  the  decimal  fraction  representing  the  per  cent  increase 
of  weight.  Occasionally  organic  matter  is  removed  by  combustion,  barren  matter 
by  magnetism  or  other  methods,  and  very  commonly  moisture  by  drying.  To 
calculate  to  original  basis;  multiply  the  assay  by  1  minus  the  decimal  representing 

1  Research  Chemist,  Nichols  Copper  Company,  New  York. 
739 


740  ASSAYING   FOR  GOLD   AND   SILVER 

the  per  cent  decrease  in  weight  of  the  sample.  Samples  of  material  which  have  the 
property  of  changing  weight  with  atmospheric  conditions,  should  be  kept  in  tightly 
stoppered  bottles.  The  assay  of  such  material  is  best  made  on  the  portion  of  the 
sample  used  in  the  determination  of  moisture.  The  distribution  of  values  in  solid 
copper  or  lead  bullion  is  never  uniform.  Unhomogeneity  tends  to  increase  with 
quantity  of  impurity  and  with  decrease  in  the  rate  of  cooling  from  the  molten  state. 
The  sample  of  copper  bullion  should  be  composed  of  drill  shavings  from  every  part 
of  the  piece  which  is  practicable  to  attack  with  a  \  or  f-in.  twist  drill  in  such  a 
manner  that  the  particles  from  each  part  shall  have  the  same  proportionate  weight 
in  the  sample  as  the  part  is  of  the  whole  piece.  This  principle  is  applied  to  the 
sampling  of  the  multiplicity  of  pieces  composing  a  lot  of  copper.  In  lot  sampling 
a  single  hole  is  drilled  through  the  top  or  bottom  of  each  piece  of  a  definite  fraction 
of  the  total  pieces  in  a  lot.  The  position  of  the  drill  is  changed  with  successive 
pieces  so  that  it  will  attack  in  turn  the  center  of  all  the  equal-sized  squares  compos- 
ing a  pattern  or  "  templet  "  which  will  exactly  cover  one-quarter,  one-half  or  the 
whole  of  the  top  of  the  average  piece.  The  squares  should  be  as  small  as  is  practi- 
cable to  drill,  about  1  in.  It  is  considered  the  best  practice  to  drill  one-half  of  the 
holes  in  blister  copper  top  to  bottom,  the  remainder  bottom  to  top,  also  when 
drilling  according  to  a  quarter  or  half  templet,  to  change  hand  side  with  every 
other  round  of  the  templet.  All  the  shavings  are  ground  to  pass  a  20-mesh  screen 
by  a  drug  mill  with  hard  steel  grinding  plates.  The  sample  of  lead  bullion,  like 
that  of  copper,  should  be  composed  of  the  due  proportion  of  particles  from  every 
part  of  the  single  piece.  The  end  is  attained  by  using  for  sample  the  sawdust 
from  complete  cuts  with  a  circular  saw  at  equal  and  definite  intervals  along  the 
length  of  the  piece.  In  lot  sampling  a  single  cut  is  made  in  a  definite  fraction 
of  the  total  number  of  pieces  in  the  lot.  The  position  of  the  cut  is  changed  with 
successive  pieces,  so  that  it  will  pass  through  the  longer  axis  of  each  of  the  equal- 
sized  rectangles  composing  the  pattern  or  templet  which  will  exactly  cover  one- 
half  or  the  whole  of  the  top  of  the  average  piece  of  the  lot.  To  make  accurate 
sampling  possible,  it  is  evident  that  the  pieces  composing  a  lot  of  either  copper 
or  lead  bullion  should  be  symmetrical  in  form  and  alike  in  size,  shape  and  grade. 
At  regular  intervals  during  the  process  of  pouring  lead  bullion  into  moulds,  samples 
may  be  taken  in  the  form  of  shot,  but  most  satisfactorily  in  the  form  of  slugs  or 
bullets,  each  weighing  close  to  the  amount  customarily  taken  for  assay  (J  or  1 
A.T.)  and  composed  of  the  entire  contents  of  the  ladle  used  for  dipping.  All  classes 
of  gold  or  silver  bullion  and  Dore*  metal  are  most  accurately  sampled  by  taking 
just  after  thorough  stirring  and  immediately  before  pouring  several  dip  samples 
of  about  3  grams  each  with  graphite  ladles.  The  metal  is  allowed  to  cool  in  the 
ladle  or  may  be  granulated  by  pouring  into  warm  water.  When  the  lot  of  bullion 
is  large,  samples  are  taken  at  definite  and  regular  intervals  throughout  the  ladling 
period.  Except  in  the  case  of  bullion  of  a  high  degree  of  fineness,  sampling  by 
drilling  or  by  cutting  chips  from  the  corners  of  bars  is  not  as  satisfactory  as  the 
methods  described. 

References  on  the  Subject  of  Sampling 
Ores: 

Woodridge,  Technical  Paper  86,  Bureau  of  Mines. 
Clarkson,  J.  Soc.  Chem.  Ind.,  1894,  214. 
Brunton,  Trans.  Am.  Inst.  Min.  Eng.,  25,  826. 
Brunton,  Trans.  Am.  Inst.  Min.  Eng.,  40,  567. 
Richards,  Ore  Dressing,  Vols.  2  and  3. 


ASSAYING  FOR  GOLD  AND   SILVER  741 

Copper  Bullion: 

Keller,  Bulletin  122,  Bureau  of  Mines/ 

Wraith,  Trans.  Am.  Inst.  Ming.  Eng.,  Bull.  39,  209. 

Keller,  Eng.  and  Min.  J.,  April  6,  1912. 

Smoot,  Eng.  and  Min.  J.,  June  22,  1912. 

Liddell,  Eng.  and  Min.  J.,  Nov.  12,  1910;  Dec.  16,  1911. 

Lead  Bullion: 

Roberts,  Trans.  Am.  Inst.  Min.  Eng.,  28,  413. 

Gold  or  Silver  Bullion: 

Rose,  "Metallurgy  of  Gold." 
Dewey,  Am.  Inst.  Min.  Eng.,  1909. 


FURNACE   OPERATIONS 

The  several  furnace  operations  employed  in  assaying  have  for  their  object: 

(1)  To  eliminate  in  part  or  entirely  from  the  material  undergoing  assay,  organic 
matter  and  such  elements  as  sulphur,  arsenic,  antimony  or  selenium  when  present  in 
sufficient  quantity  to  cause  excessive  reducing  effect  in  the  crucible  fusion,  interference 
with  decomposition,  mechanical  or  other  loss  by  either  method  of  fusion.     When  the 
operation  does  not  cause  greater  loss  of  values  than  its  avoidance  by  skillful  fluxing, 
elimination  by  combustion  or  roasting  is  practiced. 

(2)  To  produce  such  conditions  that  the  greatest  quantity  of  gold  or  silver  in  the 
material  subjected  to  assay  can  through  their  affinity  be  concentrated  in  molten  lead. 
This  is  brought  about  by  two  methods. 

a.  By  the  crucible  method,  the  material  is  mixed  with  no  larger  quantity  of  re- 
agents called  fluxes  than  will  form,  with  all  its  basic  or  acid  constituents  at  a  moderate 
temperature,  compounds  of  the  greatest  degree  of  fluidity.  Simultaneously  with  the 
progress  of  the  fusion,  lead,  generated  from  lead  oxide  by  an  added  reducing  agent  or  by 
the  property  of  the  material  itself,  percolating  the  fluid,  collects  the  precious  metals  and 
also  some  portion  of  such  other  constituents  which  combine  or  alloy  with  lead  under 
the  conditions  of  the  fusion. 

6.  By  the  scorification  method,  the  material,  in  contact  with  a  relatively  large 
mass  of  lead  in  shallow  dishes  called  scorifiers,  is  decomposed  and  fluxed  chiefly 
by  lead  oxide,  the  greater  part  of  which  is  formed  by  the  action  of  atmosphere  on  the 
molten  lead.  When  the  proportion  of  volume  of  material  or  flux  is  not  too  great, 
the  fluid  slag  collects  about  the  sides  of  the  scorifier  leaving  the  surface  of  the  lead, 
exposed  to  oxidation,  which  may  be  allowed  to  progress  until  the  increasing  proportion 
of  slag  covers  the  lead.  The  precious  metals  and  a  portion  of  other  allowable 
metals  in  the  charge  are  collected  by  contact  with  the  molten  lead.  During  scorifica- 
tion, elements  forming  readily  volatile  oxides  such  as  sulphur,  arsenic,  and  selenium 
are  in  process  of  elimination  in  the  form  of  vapor,  while  the  elements — iron,  manga- 
nese, antimony,  zinc,  cobalt,  tin,  nickel,  cadmium,  copper,  bismuth,  selenium  and 
tellurium — when  taken  up  in  one  form  or  another  by  lead  during  the  fusion  period  of 
the  operation,  are  carried  into  the  slag  at  rates  which  depend  in  part  upon  the  property 
to  oxidize  characteristic  of  the  element,  in  part  upon  the  concentration  of  the  element 
in  the  lead,  and  in  part  on  the  properties  of  the  associated  elements. 

(3)  To  procure  with  the  least  loss  of  gold  and  silver  their  alloy  with  lead  in  the 
form  of  a  lead  button  which  can  be  cleaned  of  adherent  slag  and  is  of  suitable  size 
(10  to  20  grams)  and  sufficiently  free  of  base  elements  to  make  possible  by  the  operation 
of  cupellation,  the  production  without  greater  loss  than  if  the  base  elements  were 
absent,  of  a  silver-gold  bead  of  normal  purity.     Size  of  button  is  controlled  in  scori- 
fication by  observation,  in  crucible  fusion  by  incorporation  in  the  charge  of  the  proper 
amount  (which  is  determined  by  trial  or  experience  with  similar  material),  of  oxidizing 
reagents  when  the  material  has  an  excessive  reducing  property;    of  reducing  reagent 
when  the  material  has  an  oxidizing,  neutral  or  deficient  reducing  property.     Purity 
of  button  is  obtained  by  the  scorification  method  by  repetition  of  the  operation,  with 
addition  each  time  of  lead  until  the  shade  of  color  of  the  glazed  portion  of  the  scorifier 


742  ASSAYING  FOR  GOLD   AND   SILVER 

or  appearance  or  properties  of  the  lead  button  indicate  to  the  experienced  operator 
the  presence  of  impurity  in  less  quantity  than  will  prevent  faultless  cupellation.  By 
each  method  the  amount  of  metallic  impurity  in  the  button  can  be  diminished  by 
increasing  the  proportion  of  litharge  in  the  charge.  With  increase  of  quantity  of  base 
element,  its  restraint  from  the  button  becomes  impracticable  by  the  crucible  method; 
purification  of  the  button  by  process  of  scorification  is  therefore  resorted  to  in  all  cases 
except  when  bismuth  or  copper  associated  with  selenium  or  tellurium  are  present. 
These  elements  are  best  eliminated  by  a  wet  method. 

(4)  To  separate  from  lead  which  may  contain  a  small  amount  of  other  metals  an 
alloy  of  the  precious  metals  in  weighable  form  and  in  a  definite  state  of  purity,  996-998 
fine. 

Separation  by  cupellation  is  effected  by  taking  advantage  of  the  non-susceptibility 
of  gold  or  silver  to  oxidation,  the  heat  of  formation  of  lead  and  other  metallic  oxides, 
the  fluid  character  of  lead  oxide  at  the  temperature  of  its  formation,  the  solubility 
of  a  limited  amount  of  metallic  oxides,  and  the  sparing  solubility  of  gold  and  silver  in 
fluid  lead  oxide,  the  perviousness  to  fluid  lead  oxide  of  bone  ash  of  about  the  same  tem- 
perature and  the  imperviousness  of  the  same  material  to  molten  gold,  silver  or  lead. 

Consequent  to  the  furnace  operations,  except  when  it  is  known  that  gold  is  absent, 
is  the  wet  process  of  separating  in  weighable  form  and  in  a  very  definite  state  of  purity 
(997  to  998  fine)  gold  from  silver  in  the  bead  obtained  by  cupellation. 

The  process  of  parting  depends  upon  the  fact  that  when  the  proportion  of  gold 
in  the  alloy  is  not  too  great,  silver  can  be  dissolved  almost  completely  by  hot  dilute 
nitric  acid  with  but  small  corrosive  effect  upon  the  gold. 

Preliminary  to  furnace  operations,  it  is  advantageous  in  the  assay  of  some 
classes  of  material  to  subject  the  sample  to  treatment  by  nitric  or  sulphuric  acid  with 
the  object  of  eliminating  all  or  a  greater  part  of  the  base  elements  and  of  concentrating 
the  precious  metals  into  a  mass  of  small  volume.  The  procedure  is  practicable  when 
the  character  of  the  material  is  such  that  the  residue  resulting  from  the  treatment 
does  not  interfere  with  filtration  and  when  gold  is  not  dissolved  or  liberated  in  so 
fine  a  state  that  it  cannot  be  retained  by  a  filter.  Dissolved  silver  is  precipitated  as 
chloride,  bromide,  sulphide  or  metal.  Procedures  which  introduce  the  feature  of  pre- 
liminary acid  treatment  are  called  combination  methods. 

Silver  and  gold  are  retained  in  the  slag  from  both  the  crucible  and  scorification 
method  of  fusion.  When  the  product  of  assay  of  slag  is  added  to  the  result  of  the 
primary  operation,  the  assay  is  said  to  be  carried  out  with  slag  correction. 

Silver  and  gold  are  carried  into  the  cupel  to  a  greater  extent  per  unit  of  lead  oxi- 
dized than  into  slag  by  scorification  of  lead  containing  the  same  concentration  of  pre- 
cious elements.  When  the  silver  or  gold  so  retained  is  determined,  either  by  sub- 
jecting the  cupel  to  assay  processes  or  by  check  cupellation  of  a  known  and  similar 
quantity  of  the  precious  metals  under  the  same  conditions,  and  the  result  obtained  added 
to  the  product  of  the  primary  operation,  the  assay  is  said  to  be  carried  out  with  correc- 
tion for  cupellation  loss. 

Corrected  assay  is  the  term  applied  to  the  result  which  includes  a  correction  for 
silver  and  gold  lost  into  the  slag  and  cupel.  It  is  not  customary  to  take  account  of 
the  fineness  of  the  silver  or  gold  mass,  or  of  gold  dissolved  in  the  operation  of  parting. 

Determination  of  gold,  even  when  silver  is  known  to  be  absent,  is  much  more  accu- 
rately made  by  weighing  the  product  of  the  operation  of  parting  its  alloy  with  a  suitable 
proportion  of  silver  than  the  gold  bead  resulting  from  cupellation.  Loss  of  gold  in 
cupellation  tends  to  decrease  with  increase  of  the  ratio  of  silver  present. 

The  precautions  taken  in  furnace  operations  to  prevent  abnormal  silver  loss  should 
be  observed  as  a  rule  in  the  assay  for  gold  only. 

Determination  of  silver  is  performed  bj  weighing  the  bead  resulting  from  cupel- 
lation and  subtracting  from  this  weight  the  amount  of  gold  obtained  from  the  operation 
of  parting. 

Influence  of  quantity  of  sample  taken  for  a  single  determination  can  be  derived 
relatively  from  Chart  Fig.  138,  which  shows  that  the  per  cent  of  loss  in  the  operation 
of  assaying  blister  copper  by  the  sulphuric  acid  combination  method  decreases  as  the 
proportion  of  precious  metals  in  the  charge  increases.  Cupellation  has  a  larger 
influence  ordinarily  in  this  direction  than  the  operation  of  fusion.  The  fact  is  of 
consequence  in  the  assay  of  material  for  purchase  and  sale,  for  it  is  evident  that  unless 
the  valuation  be  made  on  the  basis  of  corrected  assay,  or  a  complete  understanding  by 
all  parties  interested  exists  as  to  the  details  of  the  methods  of  assaying  employed,  con- 


ASSAYING  FOR  GOLD  AND   SILVER 


743 


troversy  may  arise  because  of  the  consistently  higher  value  which  will  be  put  on  the 
material  by  the  assayer  who  uses  the  larger  assay  portion  in  his  practice.  For  in- 
stance, in  the  valuation  of  blister  copper  containing  50  ozs.  silver  per  ton,  should 
assayer  A  representing  one  party  be  in  the  habit  of  using  2  A.T.  assay  portions,  his 


0.025 
0.023 
0.021 
0.019 

0.017 
1.6 
0.015  ^ 
g             01-4 

r  0.013  z 
r>           ol.2 
<O.OM    < 
1.0 
0.009 
0.8 
0.007 
0.6 
0.005 
0.4 
0.003 

0.001 

AU.  MGM. 
I                        2                       3 

x 

x 

x 

^ 

/ 

lA 

X] 

x 

f1  c 

x 

x 

x 

x 

\ 

/ 

X 

/ 

x 

/ 

x 

x 

/ 

r^ 

gx 

' 

I 

^ 

x 

/ 

X 

x 

? 

/ 

/ 

f 

/ 

y 

/ 

iO      20      30      40       50      60      70       80      90    IOO 
AO.  MGM. 

FIG.  138. 

valuation  of  the  lot  will  be  on  the  basis  of  — ^—  or  49.2  ozs.  per  ton,  while  B,  who  uses 

the  same  method  as  A  but  customarily  carries  out  his  operations  on  1  A.T.  portions, 
will  report  48.82  ozs.  per  ton,  or  a  result  about  0.8%  lower  than  A. 


ROASTING   INCINERATION 

In  laboratories  performing  many  assays  by  combination  methods,  incinera- 
tion of  niters  is  accomplished  by  placing  the  scorifiers  on  trays  which  fit  the  shelves 
of  an  oven  like  that  of  a  gas  stove.  The  furnace  muffle  is,  however,  commonly 
employed  for  the  purpose.  Loss  of  particles  of  the  charge  is  prevented  by  cov- 
ering the  folded  paper  with  granulated  or  sheet  lead  and  burning  slowly  at  a 
low  temperature.  Sprinkling  the  inside  of  filters  with  litharge  hastens  com- 
bustion. Carbonaceous  matter  in  material  like  reverberatory  or  blast-furnace 
flue-dust  is  removed  by  combustion  in  a  muffle.  The  same  matter  in  zinc  retort 
residue  cannot  be  removed  by  incineration  without  considerable  loss  of  silver. 
Roasting  of  pyritic  material  is  carried  out  on  the  portions  weighed  out  for  assay 
in  scorifiers  if  the  sulphur  has  little  other  metallic  base  than  iron;  in  large  roast- 


744 


ASSAYING   FOR  GOLD   AND   SILVER 


ing  dishes  when  the  sulphide  is  that  of  copper,  lead,  antimony  or  zinc.  In  the 
latter  case,  unless  there  is  considerable  earthy  base  or  silica  in  the  sample,  stir- 
ring is  required  to  prevent  sintering,  which  obstructs  complete  oxidation.  In  both 
cases,  at  the  beginning,  the  temperature  should  be  no  higher  than  is  sufficient  to 
start  and  maintain  oxidation.  When  evolution  of  sulphur  dioxide  has  practically 
ceased,  the  temperature  may  be  raised  to  about  700°  C.  to  decompose  the 
sulphates  which  have  formed  at  lower  temperature.  Decomposition  of  refractory 
sulphates — lead,  zinc,  silver,  nickel,  may  be  achieved  by  mixing  the  roast  with  one- 
third  of  its  weight  of  ammonium  carbonate  and  heating  at  about  400°  C.  Arsenic 
and  antimony  oxidize  in  part  to  volatile  trioxides,  but  a  portion,  large  if  the 
temperature  is  high  or  draft  strong,  becomes  changed  to  higher  oxides  which  form 
with  metallic  bases  salts  stable  at  higher  temperatures.  These  salts  tend  to 
increase  the  slag  loss  of  silver  in  the  fusion  stage  of  the  assay.  By  mixture  with  an 
equal  volume  of  powdered  charcoal  and  roasting  again  at  550°  to  600°  C.  in  a 
muffle  with  reduced  draft,  the  quantity  of  arsenic  or  antimony  is  diminished. 
Several  repetitions  of  the  reducing  and  oxidizing  process  may  be  required  to  bring 


FIG.  139. 


about  complete  elimination  of  the  objectionable  elements  except  in  the  case  of 
copper  arsenate,  on  which  charcoal  has  little  reducing  action. 

Because  roasting  takes  up  muffle  space,  requires  considerable  attention  in  the  case 
of  ores  containing  much  other  base  for  sulphur  than  iron,  and  is  usually  attended 
by  some  loss,  especially  of  silver,  its  practice  is  limited  to  the  assay  of  pyrites 
or  pyrrhotite  ores  which  contain  very  low  gold  and  silver  values. 


ASSAYING  FOR  GOLD  AND  SILVER 


745 


CRUCIBLE  METHOD  OF  FUSION 

This  operation  may  be  performed  in  a  wind  or  crucible  furnace,  but  best  in  a 
muffle.  If  the  furnace  is  to  be  used  for  crucible  fusion  alone,  the  muffle  need  have 
a  single  draft  hole  only  in  the  top.  Although  the  operation  is  less  subject  to 
irregularities  when  carried  out  in  a  muffle  tight  to  the  products  of  combustion, 
satisfactory  fusions  are  made  in  gas  or  liquid  fuel  furnaces  from  which  the 
muffles  have  been  removed.  The  most  convenient  shape  and  size  of  crucible 
to  muffle  fusions  are  the  5,  10,  20  or  30  grams,  Colorado  form.  The  10  and 
sometimes  the  5-gram  crucible  is  used  for  fusion  of  filter  paper  residues 
from  combination  methods.  The  20-gram  is  used  for  \  A.T.,  the  30-gram  crucible 
for  1  A.T.  ore  portions.  The  cinder  from  roasted  fine  pyrite  mixed  with  water 
makes  a  good  paint  for  marking  crucibles  or  scorifiers. 

Litharge,  melting  at  888°  C.,  is  a  basic  flux,  an  oxidizing  and  therefore  desulphuriz- 
ing agent.  It  is  the  source  of  metallic  lead  for  collecting  the  precious  metals.  With 
borax  it  forms  a  very  fluid  glass.  Its  functions  are  expressed  by  the  following 
reactions : 


2PbO  +Si02  =  2PbO  •  SiO2 
PbO+Na2CO3+SO2  = 
ZnS+3PbO  =  ZnO+3Pb+SO2 
Ag2S+2PbO  =  2PbAg+S02 
PbS+2PbO  =  3Pb+SO2 


Lead  oxide  dissolves  metallic  oxides. 
of  this  property. 


C+2PbO  =  2Pb+CO2 
Sb2S3+9PbO  =  9Pb+Sb2O3+3S02 
Sb2S3 +6Pb  O  =  Pb6Sb2 +3SO2 
2Cu2S+7PbO  =  2CuO+Cu2O+7Pb+2SO2 
Sb2+3PbO  =  Sb2O3+3Pb 

The  following  table  l    shows  the    extent 


Per  one  part  of  
Parts  of  litharge  required  .  . 

Per  one  part  of.  

Cu2O 
1.5 

SbO2 

CuO 
1.8 

As2O3 

ZnO 

8 

As2O5 

Fe3O4 

4 

Fe2O3 
10 

MnO 
10 

Sn02 

,     13 

Parts  of  litharge  required.  . 

5 

0.8 

1 

Sb2O3  is  very  soluble  in  litharge. 

Five  hundred  grams  of  lead  oxide  should  contain  no  gold,  less  than  0.0005  gram 
silver,  and  no  bismuth.  According  to  the  amount  of  litharge  used,  such  silver  as  it 
contains  should  be  deducted  from  the  weight  of  the  bead  in  the  assay  of  material  in 
which  the  normal  range  of  assay  error  is  measured  in  hundredths  rather  than  tenths  of 
an  ounce. 

Floated  silica,  analyzing  over  95%  Si02,  and  so  fine  that  90%  will  pass  a  200-mesh 
screen  is  an  excellent  and  easily  obtainable  form  of  the  reagent.  Silica  in  the  form 
of  powdered  glass,  averaging  70%  to  75%  SiO2,  is  an  acid  flux.  Its  addition  to  a  basic 
charge  should  be  limited  to  the  formation  of  a  slag  which  is  less  than  a  bisilicate. 

Borax  glass,  Na2O-2B2O3,  melting  at  878°  C.,  may  be  considered  an  acid  or  basic 
flux.  As  an  acid  flux,  it  combines  with  the  metallic  oxides  to  form  a  very  fluid  slag. 
As  a  basic  flux  it  may  be  employed  in  the  assay  of  acid  ores,  with  a  value  nearly 
equal  in  weight  to  that  of  litharge. 

Soduim  carbonate,  anhydrous,  melting  at  849°  C.,  sodium  bicarbonate  which  com- 
mences to  decompose  at  270°  C.,  and  potassium  carbonate,  anhydrous,  melting  at 
909°  C.  are  basic  fluxes.  Sodium  bicarbonate  in  its  decomposition  and  reaction  with 
silica  liberates  three  times  as  much  gas  per  unit  of  base  as  the  normal  carbonate. 

1  Hofman,  "Metallurgy  of  Lead." 


746  ASSAYING  FOR  GOLD   AND   SILVER 

By  some  assayers  this  property  is  considered  a  virtue  on  account  of  the  stirring-up  action 
on  the  charge.  In  the  use  of  bicarbonate  the  danger  of  spoiled  assays  due  to  boiling 
over  and  mechanical  loss  through  dusting  is  great.  Potassium  carbonate  in  the 
form  of  refined  pearl  ash,  is  of  value  on  account  of  the  fluidity  of  the  potash  sili- 
cates. It  is  deliquescent  and  when  dried  and  in  form  for  use  as  a  flux  must  be  kept 
out  of  contact  with  moist  atmosphere.  Sodium  carbonate  is  used  in  the  form  of 
refined  soda  ash.  A  mixture  of  equal  weights  of  soda  and  pearl  ash  is  a  good  form 
of  flux.  Besides  its  function  as  a  base  for  silica  in  the  charge,  the  alkali  flux  operates 
to  increase  the  amount  of  lead  reduced  from  lead  oxide  by  a  sulphide. 

4Na2C03 + 15PbO +2FeS2  =  Fe2O3 +4CO2 + 15Pb +4Na2S04. 

By  the  addition  of  3.1  parts  of  Na2CO3,  23  parts  of  lead  are  reduced  by  1  part  of  sulphur. 
In  the  absence  of  the  alkali,  the  reaction  would  be  FeS2+5PbO  =  FeO+2SO2+5Pb, 
according  to  which  only  16  parts  of  lead  are  reduced  by  1  part  of  sulphur.  The  reac- 
tion of  the  alkali  flux  with  lead  sulphide  is  like  the  following: 

7PbS  +4Na2CO3  =  4Pb + Na2SO4 +3  (PbS  •  Na2S)  +4CO2. 

Reducing  Agents.  In  case  the  charge  is  not  of  a  reducing  nature,  one  of  the  reagents 
in  the  table  is  added  in  quantity  which  experience  with  the  same  type  of  material, 
knowledge  of  its  composition  or  preliminary  trial  indicates  is  sufficient  to  reduce  a 
suitable  amount  of  lead  to  collect  the  precious  metals. 

The  following  table  shows  the  approximate  reducing  power  of  the  reagents  in  com- 
mon use: 

Grams  lead  reduced  by  1  gram  of  reagent. 

22    -30  Charcoal 

6    -11  Argol  (crude  tartar) 

4.5-  6.5  Cream  of  tartar 

10  -15  Wheat  flour 
11.5-14.5                                            Sugar 

22    -25  Coal  or  coke 

11 . 5-13  Corn  or  laundry  starch 

11  -12  Pyrite  (FeS2) 

To  assist  distribution  or  contact  with  the  largest  number  of  particles  of  litharge 
it  is  of  advantage  to  use  an  agent  which  is  in  a  very  fine  state  of  division  and  of  low 
reducing  power  per  unit  of  volume.  Argol  is  a  popular  reagent.  The  writer  uses  starch. 
A  carbonaceous  reducing  agent  reacts  with  silicate  of  lead  with  a  sluggishness  which 
increases  with  the  silicate  degree  above  the  monosilicate,  but  the  presence  of  other 
bases,  especially  the  alkaline,  operates  to  make  the  reaction  more  complete. 

2PbO  •  SiO2+2Na2O+C  =  2Na2O  •  SiO2 +CO2 +2Pb. 

Iron  in  the  form  of  twenty-penny  nails  or  £-in.  iron  wire  can  be  used  as  a  reducing 
agent  and  desulphurizing  agent  in  the  assay  of  material  which  contains  little  or  no 
base  impurities,  such  as  copper,  tin,  antimony.  Its  functions  are  expressed  by  the 
following  reactions: 

Fe+PbS=FeS+Pb 

Fe+FeS2=2FeS 

PbO+Fe=FeO+Pb 

2PbO  -Si02+2Fe =2FeO  •  SiO2+2Pb 

PbS.Na2S+Fe=FeS+Na2S+Pb 

Potassium  nitrate,  saltpeter,  melting  when  pure  at  337°  C.,  or  sodium  nitrate,  nitre, 
melting  when  pure  at  316°  C.,  are  oxidizing  and  therefore  desulphurizing  agents.  Sodium 
nitrate  is  deliquescent.  Either  salt  should  be  dried,  very  finely  pulverized  and  kept 
in  a  stoppered  bottle. 

The  nitrates  decompose  on  heating, 

2KN08=2KN02+Oa; 


ASSAYING  FOR  GOLD  AND   SILVER 


747 


and  at  a  higher  temperature, 

2KNO2  =  K2O  +2NO  +O. 
Their  behavior  in  fusions  is  illustrated  by  the  following  reactions: 

4FeS2  +  10KNO3  =  4FeO  +5K2SO4  +3SO2  +5N2  ; 

4ZnS  +6KNO3  =  4ZnO  +3K2SO4  +SO2  +3N2. 
When  an  alkaline  base  is  present  the  reaction  is 


Nitrates  act  on  metallic  lead 

7Pb+6KNO8  =  7PbO  +3K2O+3N2+4O2. 

Salt,  melting  at  804°  C.,  is  used  in  a  thin  layer  as  a  cover  over  the  top  of  the  charge 
in  the  crucible.  It  is  very  fluid  when  melted  and  haying  a  low  gravity,  floats  on  the 
fusion.  Its  function  is  to  prevent  the  charge  from  boiling  over  or  spattering.  When 
moist  it  decrepitates  and  on  that  account  may  cause  loss  of  particles  of  the  charge. 
It  should  be  dried  before  use. 

Fluxing.  All  substances  from  which  precious  metals  are  to  be  effectively  col- 
lected by  crucible  fusion  must  necessarily  be  in  a  fine  state  of  division,  and  mainly 
composed  of  compounds  which  may  be  classified  as  acid  or  basic.  Acid  is  the 
characteristic  applied  to  material  which  contains  silica,  free  or  combined  with  too 
little  base  to  form  a  readily  fusible  substance.  Basic  is  the  term  applied  to 
metallic  or  earthy  oxides,  or  compounds  which  may  be  brought  to  the  state  of 
oxide  in  the  process  of  fusion.  In  this  form  they  are  capable  of  forming 
salts  with  silica.  These  salts  are  defined  by  the  ratio  to  each  other  of  oxygen 
in  the  acid  and  base.  By  the  metallurgical  classification  their  names  are  as 
follows  : 


Formula. 

Name. 

Oxygen  Ratio 
[  Base  to  Acid. 

Example. 

4RO  •  SiO2  

Subsilicate 

2  to  1 

4PbO-SiO2 

2RO-SiO2  

Monosilicate 

1  to  1 

2Al2O3-3SiO2 

RO-SiO2 

Bisilicate 

1  to  2 

CaO-SiO2 

4RO  •  3SiO2 

Sesquisilicate 

2  to  3 

4MgO-3SiO2 

2RO-3SiO2.. 

Trisilicate 

1  to  3 

2PbO-3SiO2 

The  silicates  of  Na20,  K20  and  PbO  are  readily,  MnO,  FeO,  and  Cu20,  less; 
and  MgO,  CaO,  and  A1203  difficultly  fusible.  To  make  the  refractory  silicates 
fusible  and  fluid  at  moderate  temperatures,  the  proportion  of  their  bases  should 
be  less  in  the  fusion  than  the  bases  of  the  readily  fusible  silicates.  Advantage 
is  also  taken  of  the  fact  that  the  multibasic  silicates  are  more  fusible  generally 
than  the  single  of  the  same  degree. 

A  rule  governing  the  fluxing  of  a  crucible  charge  is  very  definitely  stated  by 
Fulton,1  "  The  most  desirable  constitution  for  an  assay  slag,  in  general,  is  that  of 
a  monosilicate  or  sesquisilicate,  sometimes,  but  more  rarely,  a  bisilicate.  If  the 
ore  is  basic,  a  bisilicate  slag  may  be  approached,  if  acid,  a  monosilicate  or  even 
a  subsilicate." 

1  "Fire  Assaying/'  2d  ed.,  69. 


748 


ASSAYING  FOR  GOLD  AND   SILVER 


To  FORM  A  MONOSILICATE  THE  REQUIREMENT 


Na20 

K20 

PbO 

MnO 

FeO 

Per  unit  of  base  silica  required 

0  486 

0  320 

0  135 

0  425 

0  419 

Per  unit  of  silica,  base  required  

2.06 

3.12 

7.40 

2.35 

2  37 

A1203 

CuO 

ZnO 

CaO 

MgO 

Per  unit  of  base  silica  required    . 

0  886 

0  379 

0  371 

0  359 

0  748 

Per  unit  of  silica  base  required 

1  13 

2  64 

2  70 

2  64 

1  34 

A  crucible  fusion  should  not  be  fluxed  by  borax  or  litharge  alone.  No 
more  borax  should  be  used  than  is  required  to  combine  with  bases  and  silica  in  the 
proportion  illustrated  by  the  equations: 

2(Na20,  2B203)+Si02  =2Na20 •  Si02+4B203, 
B203  +3FeO  =3FeO  •  B203. 

As  a  flux  for  silica,  6.7  parts  borax  will  take  the  place  and  can  be  substituted 
for  7.4  parts  litharge,  3.5  parts  Na2C03,  5.4  parts  NaHC03  or  4.6  parts  K2C03. 
As  a  flux  for  bases,  assumption  of  3RO,  B203  works  out  well  in  practice. 


FeO 

CaO 

MgO 

ZnO 

PbO 

Required  of  borax  per  unit  of 
base                                    .... 

0  937 

1.20 

1.67 

0.807 

0.302 

"  In  the  fusion  of  a  mixture  containing  silica,  various  bases  and  borax  glass, 
that  silicate  borate  having  the  lowest  formation  point  will  form  and  then  as  the 
temperature  rises,  absorbs  either  silica,  base  or  both,  as  these  are  in  excess  of  the 
ratio  required  to  form  the  lowest  formation  point  compound.  If  the  temperature 
does  not  rise  high  enough  to  cause  this  absorption,  the  excess  of  silica  or  base  or 
both  will  remain  in  suspension  in  the  formed  silicate  borate,  practically  in  an 
unaltered  condition."  l 

Materials  intended  for  crucible  assay  are  characterized  according  to  their 
behavior  toward  lead  or  lead  oxide  as  oxidizing,  reducing  or  neutral.  The  oxidiz- 
ing constituents  of  an  ore  are  practically  limited  to  Fe203,  Fe304,  Mn02  and  CuO. 
Substances  containing  unoxidized  sulphur,  antimony,  arsenic  or  carbon,  on  fusion 
with  litharge  produce  metallic  lead.  When  an  arsenide  is  present  with  iron, 
nickel  or  cobalt  a  brittle  fusible  substance  called  speiss  will  be  found  in  the  crucible 
above  the  lead.  Also  when  iron  is  present  and  the  quantity  of  litharge  has  not 
been  sufficient  to  oxidize  all  the  sulphur,  a  sulphide  compound  of  iron  and 
lead  called  matte  will  be  found  above  the  layer  of  speiss.  When  the  silver 
content  of  the  ore  is  small,  the  ore  can  be  roasted  in  the  manner  already 
described.  The  roasted  ore  then  as  a  rule  becomes  oxidizing  in  its  behavior. 
To  obtain  a  lead  button  of  suitable  size,  knowledge  of  the  oxidizing  power 

9  Fulton,  "  Fire  Assaying,"  2d  ed.,  64. 


ASSAYING  FOR  GOLD   AND   SILVER  749 

of  the  ore  is  obtained  from  experience  or  by  trial  assay.  Having  once  determined 
the  reducing  power  of  the  reducing  reagent,  for  instance  starch,  by  fusion  of  its 
intimate  mixture  with  the  charge  without  the  ore,  ^  A.T.  of  the  ore  is  roasted 
and  then  fused  with  50  grams  litharge,  2  grams  starch,  accurately  weighed  out,  10 
grams  soda  ash  and  8  grams  silica.  A  thin  layer  of  borax  or  salt  covers  the  charge 
in  the  crucible.  If  the  reducing  power  of  the  2  grams  of  starch  is  known  to  be  22 
grams  and  only  15  grams  of  lead  are  produced  by  fusion  of  the  ore,  the  oxidizing 

2(22  —  15) 
power  of  the  ore  is  equivalent  to — =0.636  gram  starch  per  half  A.T. 

2.636  grams  of  starch  therefore  should  be  used  to  obtain  a  22-gram  button. 

Since  roasting  causes  inappreciable  loss  as  a  rule  only  in  the  case  of  material 
of  low  silver  value,  oxidation  by  addition  of  nitre  to  the  fusion  is  the  more  generally 
practiced.  Theoretically  the  oxidizing  value  of  1  gram  of  KN03  is  2.39  grams  of 
lead  according  to  the  reaction 

7Pb  +6KNO3  =  7PbO  +3K20  +6N  +80. 

The  reducing  power  of  ^  A.T.  of  the  ore  is  determined  by  trial  fusion  with 
60  grams  of  litharge,  5  grams  silica,  7  grams  Na2C03  and  borax  cover.  Assume 
the  product  is  a  button  weighing  16  grams.  A  fusion  may  then  be  made  with 
the  same  charge  but  with  1  gram  of  nitre  added.  Assuming  the  product  of  the 
nitre  fusion  to  be  12  grams,  then  the  oxidizing  power  per  gram  of  nitre  is  16—12 
or  4  grams  under  the  conditions  of  the  fusion.  If  the  assay  is  to  be  made  on  a 
^  A.T.  portion  and  a  25-gram  button  is  desired,  then  (16x5)  — 25=55,  and 
1^  =  13.75  grams  nitre  to  be  added.  When  sulphur  is  oxidized  by  nitre,  care 
should  be  taken  that  sufficient  Na2C03  is  in  the  charge  to  carry  out  the  reaction: 

6KN03+Na2C03+2FeS2=FeiO3+3K2S04+Nai!S04+6N+C02. 

Theoretically  the  quantity  of  Na2C03  required  is  0.84  of  the  sulphur  present 
or  0.175  of  the  nitre  used. 

The  oxidizing  power  per  gram  of  nitre,  when  sufficient  Na2C03  is  present, 
ranges  from  the  equivalent  of  4.7  to  5.6  grams  lead  in  a  litharge  soda  charge  and 
4.0  to  4.2  grams  in  a  charge  containing  so  much  silica  that  little  of  the  alkaline 
base  is  left  to  form  a  sulphate. 

In  practice,  the  requirement  of  quick  results  does  not  always  permit  of  trial 
assays  for  determination  of  oxidizing  or  reducing  power.  Estimation  of  the  re- 
ducing value  of  sulphide  ores  can  be  made  by  experience  gained  by  observation 
of  the  proportion  of  heavier  sulphide  to  gangue  on  vanning  a  definite  weight  of  a 
sample  in  a  shovel  or  porcelain  spot  plate. 

Instead  of  weighing  out  each  of  the  fluxes  at  the  time  of  dressing  a  crucible, 
it  is  the  practice  to  make  up  for  each  type  of  ore  a  stock  mixture  of  all  or  part  of 
the  reagents  adapted  to  its  assay,  and  to  measure  out  the  flux  with  a  graduate. 

Oxidizing  and  reducing  reagents,  when  not  incorporated  in  a  stock  flux,  are 
weighed  out  carefully. 

The  following  are  examples,  the  first  from  Fulton  1  "  Reducing  flux  designed 
to  give  a  22-gram  button  with  a  neutral  charge : 

1  "Fire  Assaying,"  150;  Hawley,  Eng.  and  Min.  Jo.,  89,  1122;  90,  647. 


750 


ASSAYING  FOR  GOLD   AND   SILVER 


PbO,        15    parts  

Grams  per 

60 

Na>CO,,,    4       "    

16 

Borax,       2       "    

8 

Flour,        0.44"   , 

1. 

A.T. 


"  A  scoopful  of  flux  weighing  84  grams  is  used  per  £  A.T. 
"  Non-reducing  flux  to  be  used  in  connection  with  nitre  for  sulphide  ores 
which  will  give  a  button  larger  than  22  grams. 

Grama  per  i  A.T. 

PbO,       15     parts 60 

Na2COs,    3.5      "  14 

Borax,       2.5      "  10 

Silica,        0.5      "  2 

Nitre As  required 

"When  sulphide  ores  are  assayed  which  do  not  contain  sufficient  sulphides 
for  a  22-gram  button,  the  reducing  and  non-reducing  fluxes  are  mixed  in  such  pro- 
portion as  to  obtain  the  desired  result.  Ore  3.64  grams;  non-reducing  flux  50 
grams.  This  is  run  in  a  10-gram  crucible.  This  charge  will  give  a  lead  button 
weighing  as  much  as  the  nitre  necessary  to  oxidize  all  the  sulphides  in  a  0.5  A.T. 
portion  of  the  ore.  Place  the  lead  button  obtained  in  one  scale  pan  of  the  pulp 
scale  and  from  the  hook  above  the  other  suspend  by  fine  wire  a  weight  so  that  the 
wire  amounts  to  6  grams.  Then  add  nitre  to  the  pan  having  the  6-gram  weight 
until  the  scale  is  in  balance.  The  amount  of  nitre  is  the  proper  quantity  neces- 
sary to  reduce  a  22-gram  button  with  the  ore  and  the  non-reducing  flux  is  0.5 
A.T.  be  taken  for  assay." 

The  following  stock  fluxes  are  used  by  a  well-known  New  York  firm  of  assayers. 

No.  1  flux  for  free  acid  ores  without  much  sulphides  or  reducing  agents. 


Lb3. 

% 

Grams  per  A.T. 

Sods,  ash                                     

6| 

22  8 

31  9 

Pearl  ash 

2? 

8  8 

12  3 

Silica                            

24 

8  8 

12  3 

Borax  glass                 

4 

14  0 

19  6 

Litharge                      '  

12^ 

44  0 

61  6 

Argol                       

1.7 

2  4 

Use  140  grams  per  A.T.  of  pulp.    Argol  may  be  increased  as  the  individual 
charge  requires. 

No.  2  flux  for  basic  ores  without  much  sulphate  or  other  reducing  agents. 


Lbs. 

% 

Grams  per  A.T. 

Soda  ash           

5 

17  2 

24  1 

Pearl  ash  

2} 

18  6 

12  0 

Silica 

41 

15  5 

21  7 

Borax  glass 

4 

13  8 

19  3 

Litharge.         

12i 

43  1 

60  3 

Argol   

i 

1  0 

2  4 

ASSAYING  FOR   GOLD  AND   SILVER  751 

Use  140  grams  per  A.T.  of  material.     Argol  may  be  increased  in  the  individual 
charge. 

No.  3  flux  for  heavy  copper  sulphides  containing  but  little  silicious  matter. 


Lbs. 

% 

Per  i  A.T. 

Litharge                                   

40 

84.2 

252.6 

Soda  ash                      

3| 

7.4 

22.2 

Silica                   

4 

8.4 

25.2 

Use  200  to  300  grams  flux  per  \  A.T.  of  pulp,  less  for  lighter,  more  for  heavier 
sulphides.  Reduce  the  very  large  lead  button  weighing  90  to  120  Ibs.  by  scori- 
fication.  Varying  mixtures  of  No.  1  and  No.  3  are  employed  for  sulphides  ores 
carrying  considerable  silica.  High  grade  litharge  free  of  bismuth  is  essential. 
Soda  ash  is  the  ordinary  high  test  commercial  variety.  All  ingredients  should 
be  finely  powdered  and  thoroughly  mixed  by  repeatedly  passing  the  flux  through 
a  coarse  screen  or  by  turning  a  mixing  cylinder. 

By  the  following  method  l  a  large  excess  of  litharge  is  supplied  to  dissolve  or 
prevent  reduction  of  metal  oxides.  Because  the  silver  loss  into  the  slag  tends  to 
increase  with  excess  of  litharge  and  volume  of  the  slag,  the  method  is  applicable 
to  material  which  contains  copper  or  other  metals  in  such  quantity  that  repeated 
scorification  is  required  to  complete  their  removal  when  a  less  proportion  of  litharge 
is  used. 

The  type  of  charge  per  crucible  usually  is: 

Ore 0.25-0.5  A.T. 

PbO 8-10 

Na2C03      12  grams 

Si02 10     " 

Nitre  or  reducing  agent  in  quantity  sufficient  to  obtain  a  20-gram  button. 

Proportion  of  PbO  to  assay  portion  is  increased  or  diminished  according  to 
experience  with  the  kind  and  quantity  of  metal  which  is  to  be  kept  from  the 
button. 

The  iron  nail  method  is  applicable  to  sulphur-bearing  ores  which  do  not  con- 
tain much  copper  or  other  impurities  alloyable  with  lead. 

Since  iron  reduces  PbO,  the  amount  of  litharge  in  the  charge  is  limited  to  25  to 
30  grams.  The  slag  should  be  below  the  monosilicate  and  the  charge  should  be 
sufficiently  high  in  soda  to  make  certain  the  completion  of  the  reaction  7PbO  +FeS2 
+2Na2C03=7Pb+2Na2S04+FeO+2C02,  else  matte  will  be  formed.  When 
arsenic  is  present  the  temperature  should  not  be  above  1050°  C.,2  else  speiss  may 
form.  A  typical  charge  is: 

Grams. 

Ore 0.5 

Na2C03 20 

PbO 30 

Si02 2 

Borax 8 

Iron  equivalent  to  three  twenty-penny  nails  is  introduced  in  such  a  form  and 

1  Perkins,  Trans.  Am.  Inst.  Min.  Eng.,  31,  913. 

2  Fulton,  "  Fire  Assaying,"  122. 


752 


ASSAYING  FOR  GOLD   AND   SILVER 


manner  that  just  before  pouring,  the  portion  above  the  charge  can  be  seized 
firmly  by  suitable  tongs,  freed  of  adherent  lead  by  knocking  against  the  side  of 
the  crucible  and  then  withdrawn. 

Ores  containing  a  great  deal  of  silica  and  little  of  metallic  oxides  may  be 
fused  with  a  charge  similar  to  the  following : 

Ore J  A.T. 

PbO 30  grams 

Na2C03 30    " 

Reducing  agent  sufficient  to  produce  a  20-gram  button. 

In  the  assay  of  ores  containing  selenium  or  tellurium,  these  metals  must  be 
practically  eliminated  from  the  lead  before  cupellation.  Both  have  a  great  affinity 
for  lead  and  copper  and  unless  the  fluxes  are  well  proportioned  and  the  fusion 
skillfully  carried  out,  the  product  will  be  a  brittle  button  which  cannot  be  detached 
from  the  slag.  Tellurium  reacts  with  litharge  at  moderate  temperature,  700  to 
900°  C.,1  before  silicates  of  lead  are  formed  according  to  the  reaction  2PbO+Te 
=  Pb20+TeO.  Partial  reversion  of  the  reaction  takes  place  during  the  forma- 
tion of  silicates.  When  litharge  has  reacted  sufficiently  to  form  silicates  there  is 
no  longer  any  oxidizing  effect  on  tellurium.2  In  the  assay  of  gold  telluride  ores 
it  is  the  best  practice  to  make  a  crucible  fusion  with  a  large  quantity  of  litharge 
and  to  cupel  directly  or  after  scorification.  The  passage  of  tellurium  into  the 
slag  is  more  complete  in  the  case  of  a  basic  than  an  acid  slag.  The  following  are 
type  charges : 3 


Hillebrand  and 
Allen's  charge  for 
Cripple  Creek  Ore. 

Silicious  Ore  with 
Slight  Reducing 
Power. 

Cripple  Creek  Ore 
Containing  15-25% 
AhOs. 

Flour. 

1  A.T 

0  5  A.T. 

0  5  A.T. 

Ore 

6  A.T. 

100    grams 

45  5  grams 

Litharge.         .                    ... 

30         " 

9      '   " 

Na2CO3 

10  5      " 

K2CO3 

10  grams 

6        " 

85      " 

Borax..                              .    .  . 

when  required 

11" 

Charcoal. 

when  required 

1.5      " 

NaHCO3 

1  A.T. 

Litharge  cover.     Salt  should  not  be  used. 

The  fusion  of  1  and  2  should  be  carried  out  at  a  low  temperature  950-10C00  C., 
for  45  minutes,  and  finished  by  quickly  raising  the  temperature,  for  a  short  period. 
Fusion  of  3,  which  is  not  an  excess  litharge  charge,  is  conducted  at  a  tempera- 
ture above  the  melting-point  of  gold,  1063°  C.,  for  the  same  length  of  time. 

Silicious  furnace  by-products  from  the  smelting  of  electrolytic  slime  from  a  copper 
refinery  may  contain  selenium  and  tellurium  in  much  larger  percentage  than  is  usual 
in  ores.  Especially  when  associated  with  copper,  uniform  results  are  most  certainly 
obtained  by  a  crucible  fusion  with  a  large  excess  of  litharge  of  the  largest  assay  portion 
which  will  produce  a  button  which  can  be  detached  from  the  slag.  Copper,  selenium 
and  tellurium  are  removed  by  wet  treatment  described  on  page  772. 

In  the  assay  of  zinc-bearing  material,  loss  of  the  precious  metals  through 
entrainment  may  be  great  if  in  any  part  of  the  process  fume  of  zinc  oxide  is  evolved. 

1  Smith,  Trans.  Inst.  Min.  and  Met.,  17,  473. 

» E.  A.  Smith,  "  Assay  of  the  Precious  Metals,"  227. 

8  Fulton,  Fire  Assaying,  131-136. 


ASSAYING  FOB  GOLD  AND  SILVER 


753 


On  that  account,  whenever  it  is  practicable  material  containing  metallic  zinc 
should  be  subjected  to  acid  treatment  preliminary  to  the  furnace  operation.  Loss 
into  the  slag  may  occur,  through  incomplete  decomposition  on  account  of  the 
refractoriness  of  zinc  silicate  or  because  of  the  low  solubility  of  zinc  oxide  in  litharge. 
The  following  is  a  type  charge  for  \  A.T.  of  ore  containing  a  high  percentage 
of  zinc  sulphide. 

Grams. 

Litharge 100-200 

Soda 10-15 

Silica 5-10 

Borax 5 

Nitre  sufficient  to  produce  a  20  to  25-gram  button.    Borax  glass  cover. 

The  final  temperature  of  the  fusion  should  be  about  1100°  C. 

When  antimony  in  quantity  is  present,  the  crucible  charge  should  contain  a 
larger  proportion  of  either  litharge  or  soda.  The  following  are  type  charges  for 
\  A.T.  of  an  ore  containing  a  high  percentage  of  sulphide  of  antimony. 


No.  1.* 
Grams. 

No.  2.f 
Grams. 

Litharge                                                        

150 

50 

Soda                                                       

10 

35 

Borax.                         .        

6 

10 

Silica      .            

10 

*  Fulton,  Manual  of  Fire  Assaying,    146. 

t  E.  A.  Smith,  Assaying  of  Precious  Metals,  222. 

Nitre  sufficient  to  produce  a  25-gram  button. 

Salt  used  as  cover. 

As  a  rule  a  little  antimony  will  contaminate  the  button  and  should  be  removed 
by  a  five  or  ten-minute  scorification  with  about  10  grams  of  litharge. 

In  the  assay  of  tin  ores  or  concentrates,  consideration  must  be  given  to  the 
low  solubility  of  tin  oxide  in  litharge.  The  following  are  type  charges: 


No.  1. 

No.  2.* 

Ore                                                                     .    .  . 

i  A.T. 

\  A.T. 

Litharge.                                                        

150  grams 

35  grams 

Soda.                                                          

10     " 

25     " 

Borax.  ...                     .                         

5     " 

5     " 

*  Bannister,  Trans.  Inst.  Min.  and  Met.,  15,  513. 

Reducing  agent  sufficient  to  produce  a  20-gram  button. 

By  method  No.  2  it  has  been  found  necessary  to  clean  the  slag  when  the  ore 
contains  over  1  oz.  of  gold.  The  slag  is  therefore  pulverized  and  fused  with  a 
mixture  of  20  grams  litharge,  6  grams  soda  and  sufficient  reducing  agent  to 
produce  a  20-gram  button. 

Nickel  and  cobalt  silver  ores  always  contain  arsenic,  usually  antimony  and 
sometimes  as  much  as  10%  of  silver,  of  which  a  portion  may  be  in  the  form  of 
large  particles  of  very  pure  metal.  Handy1  describes  the  following:  The  charge 

1  Eighth  Int.  Cong.  Appl.  Chem.,  1912,  Sect.  IIIA. 


754  ASSAYING  FOR  GOLD  AND   SILVER 

for  the  crucible,  0.2  oz.  pulp,  12  grams  K2C03,  12  grams  Na2C03,  6  grams  borax, 
60  grams  litharge  and  1  gram  of  flour.  "  These  are  mixed  by  rolling  in  a  rubber 
cloth,  transferred  to  a  crucible,  covered  with  borax  glass  and  heated  to  a  medium 
red  heat  for  twenty  minutes.  The  door  of  the  gas-fired  muffle  is  then  shut  and 
the  crucible  heated  to  a  bright  yellow  for  thirty  minutes." 

The  following  are  efficient  charges  employed  in  the  process  of  corrected  assay. 
Because  calcium  phosphate  is  not  decomposed  by  the  fusion,  it  is  necessary  in 
the  assay  of  the  cupel  that  it  should  be  very  finely  powdered — no  coarser  than 
120  mesh. 


Slag. 

Saturated  Portion 
of  Cupel. 

Material      

100  parts 

100  parts 

25      " 

100     " 

Soda                                        

10      " 

40     " 

Borax                                          

5      " 

75     " 

Reducing  agent,  sufficient  to  produce  a  20-gram  button,  is  added  and  thoroughly 
mixed  with  each  material  while  it  is  being  pulverized.  Salt  is  used  for  cover. 
The  fusion  of  the  cupel  powder  should  be  finished  at  a  high  temperature.  The 
button  from  slag  containing  copper,  antimony,  tin,  nickel  or  cobalt  may  require 
scorification  with  addition  of  lead  before  it  becomes  suitable  for  cupellation. 
Purification  of  the  lead  button  may  also  be  accomplished  by  melting  it  in  a  crucible 
or  scorifier  with  litharge  sufficient  to  cover  it  and  a  pinch  of  silica  or  borax. 
When  the  slag  is  fluid,  the  crucible  is  given  a  rotary  motion,  either  within  or 
without  the  furnace.  This  treatment  is  continued  at  intervals  for  five  to  ten 
minutes  before  pouring. 

In  the  conduct  of  the  crucible  method,  it  is  of  extreme  consequence  when  the 
material  is  neutral  or  oxidizing  in  its  action  that  there  should  be  very  intimate 
mixture  of  the  assay  portion  with  the  reducing  agent  and  with  litharge.  When 
reducing  in  action,  the  finely  pulverized  nitre  should  be  thoroughly  mixed  with 
the  assay  portion. 

The  operation  of  mixing  is  conveniently  accomplished  by  use  of  a  10-  or  12-in. 
porcelain  mortar  with  glazed  inner  surface,  or  by  rolling  on  a  30-in.  square  piece 
of  smooth  rubber  cloth.  Soda  should  be  well  mixed  with  the  charge  but  not 
necessarily  so  intimately  as  to  lose  its  identity.  Silica  and  borax  may  be  roughly 
mixed.  The  use  of  a  cover  of  salt  or  borax  is  of  advantage  in  all  fusions  in  which 
much  gas,  C02,  CO,  S02  or  H20  is  liberated. 

Salt  is  not  recommended  as  a  cover  of  charges  high  in  silver  or  gold.  If 
the  crucible  is  heated  too  slowly,  the  greater  part  of  the  lead  may  be  reduced 
and  run  to  the  bottom  of  the  crucible  before  complete  decomposition  of  that 
constituent  of  the  ore  which  carries  the  precious  metal  has  taken  place.  When 
heated  too  speedily,  that  compound  of  base  and  borax  with  the  silica  of  the  ore 
which  has  the  lowest  formation  point  will  sink  to  the  bottom  of  the  charge, 
leaving  a  pasty,  unbalanced  charge  above.  Moreover,  evolution  of  the  gases 
may  not  only  cause  mechanical  loss,  but  on  account  of  their  expulsion  before  the 
material  undergoing  assay  is  entirely  decomposed,  the  effect  of  their  stirring 
action  is  lost. 

Fusion.  As  a  rule  it  is  good  practice  to  place  crucible  into  a  muffle  which  is 
at  about  850  to  900°  C.  The  introduction  of  the  crucibles  cool  the  furnace  to 
about  550  to  600°  C.  Without  altering  the  sate  of  introduction  of  heat  to  the  fur- 


ASSAYING  FOR  GOLD  AND   SILVER  755 

nace,  the  flow  of  heat  to  the  crucible  charge  continues  until  at  the  end  of  twenty- 
five  to  thirty  minutes  evolution  of  gas  ceases.  The  fire  is  then  urged  for  ten  to 
fifteen  minutes  until  a  temperature  of  about  1100°  is  reached,  when  the  crucibles 
are  withdrawn  from  the  muffle  and  poured  into  a  dry,  clean,  shallow-bottomed  or 
conical  mould.  The  slag  should  be  very  fluid  and  free  of  any  evidence  of  unde- 
composed  ore.  If  the  slag  is  pasty,  the  necessity  of  modifying  the  flux  is  indicated. 
If  the  nature  of  the  flux  is  such  that  the  crucible  is  very  much  corroded,  it  is 
good  practice  to  pour  off  most  of  the  slag  and  permit  the  lead,  covered  with  slag, 
to  solidify  in  the  crucible. 

SCORIFICATION 

Scorification   is    most    efficiently   carried    out    in  a  muffle   sealed  from  the 
products  of  combustion  and  having  a  rectangular  opening  in  the  back  nearly  the 


FIG.  140. 

full  width  of  the  muffle  and  about  on  the  level  with  the  top  of  the  scorifiers.  The 
opening  should  be  connected  with  a  flue  pipe  fitted  close  to  the  furnace  with  an 
easily  controlled  damper.  The  draft  head  from  a  chimney  10  ft.  in  height  is 
effective.  The  life  of  a  muffle  is  prolonged  by  a  layer  of  bone  ash  or  silica  sand 
over  its  floor  and  by  adequate  support  of  the  entire  bottom.  Mixture  of  1  part 
fire-clay  with  3-4  parts  silica  sand  serves  well  to  lute  the  muffle  to  the  furnace. 
Alundum  cement  is  better  for  filling  cracks  in  the  muffle. 

The  best  form  of  scorifier  is  the  Bartlett  shape.  The  nearly  flat  bottom  of 
this  type  gives  room  for  a  larger  accumulation  of  slag  about  the  molten  lead 
than  a  rounder  bottomed  scorifier  of  the  same  diameter.  The  sizes  of  scorifier 


756  ASSAYING  FOR  GOLD   AND   SILVER 

commonly  employed  are  the  2,  2£,  and  3  inch.  For  the  fusion  of  ore  or  other  mate- 
rial, when  it  is  of  advantage  to  use  as  large  as  possible  charge  of  either  assay 
portion  or  of  lead,  the  3-in.  size  is  employed.  For  the  fusion  of  filter  paper  residue, 
from  which  a  moderate  quantity  of  impurity  such  as  copper,  silica  or  iron,  is  to 
be  removed,  the  2^-in.  size  is  adapted.  The  2-in.  size  is  used  for  filter  paper 
residue  of  small  volume,  which  contains  so  little  impurity  objectionable  in  the 
process  of  cupellation  that  only  short  scorification  is  required. 

Moisture  and  especially  salts  absorbed  by  a  scorifier  will  cause  spurting  of  the 
lead  during  scorification.  For  this  reason,  scorifiers  should  be  kept  dry,  and  those 
intended  for  reception  of  moist  substances  should  be  first  glazed  with  lead  borate 
or  silicate,  or  lined  with  a  single  sheet  of  lead  foil. 

The  reagents  used  are  limited  to  granulated  test  lead,  sheet  lead,  borax  glass, 
silica  and  litharge. 

Granulated  lead  is  commonly  of  such  degree  of  fineness  that  50%  or  more  will  pass 
a  60-mesh  screen.  The  sheet  lead  most  generally  used  weighs  1.5  to  1.75  grams  per 
square  inch.  The  amount  of  gold  in  500  grams  of  lead  should  be  and  generally  is 
unweighable.  While  the  lead  should  contain  no  bismuth  or  silver,  it  too  frequently 
carries  as  much  as  0.005%  of  bismuth,  and  0.0002%  of  silver.  The  silver  content 
should  be  known  and  correction  on  account  of  it  should  be  applied  to  results  from 
material,  the  assay  error  of  which  is  measured  in  hundredths  rather  than  tenths 
of  a  milligram. 

Borax  glass  alone  is  always  used  as  a  flux  for  silicious  material.  Silica  alone  is  used 
in  all  rescorifications.  A  mixture  of  equal  parts  of  borax  and  silica  is  used  to  flux 
basic  charges. 

Litharge  mixed  with  the  assay  portion  of  any  refractory  material  increases  the  rate 
of  its  decomposition. 

The  scorification  method  is  especially  applicable  to  the  fusion  of  filter  paper 
residue  in  combination  methods  of  assaying,  to  gold  or  silver  ores  and  to  cop- 
per or  lead  refinery  by-products  which  are  so  rich  that  0.1  or  0.05  A.T.  con- 
stitutes the  test  portion,  and  to  the  assay  for  gold  in  material  in  which  gold 
is  less  and  silver  more  accurately  determined  by  combination  methods,  such 
as  some  high  copper  ores,  furnace  and  refinery  products.  Scorification  is 
employed  to  purify  lead,  either  as  sample  or  the  product  of  the  crucible  fusion, 
of  impurities  which  are  objectionable  in  the  process  of  cupellation.  The  scorifi- 
cation method  of  fusion  can  be  applied  to  low-grade  silver-and  gold-bearing 
silicious  material,  but  usually  gives  the  lower  result  and  requires  more  furnace 
space  and  attention  of  the  operator  than  the  crucible  method.  Of  such  material, 
it  is  the  practice  to  make  fusions  of  portions  of  0.1  to  0.25  A.T.  each,  and  on  the 
single  button  or  on  combinations  of  the  buttons,  with  or  without  addition  of  more 
lead,  second,  third  or  even  fourth  scorifications  are  made  until  a  button  of  suitable 
purity  and  size  is  obtained  which  represents  0.5  or  1  A.T. 

The  size  of  charge  and  detail  of  method  of  manipulation  to  produce  the  button 
for  cupellation  in  the  assay  of  any  single  type  of  material  depends  upon  the  size 
and  shape  of  muffle  and  scorifiers,  and  the  quality  of  draft.  For  instance,  with  a 
muffle  of  6  ins.  or  more  of  inside  height,  having  a  draft  hole  and  flue  area 
10-12%  of  the  area  of  cross-section  of  the  inside  of  the  muffle,  it  is  possible  to 
scorify  at  the  back  of  the  muffle  without  pouring  off  the  slag  60  grams  of  lead 
in  a  3-in.  Bartlett-shaped  scorifier  of  American  manufacture,  to  a  15-  to  20-gnun 
button.  While  a  30-  to  50-gram  button  will  be  the  product  of  the  scorification  in 
a  muffle  of  such  low  form  that  it  is  difficult  to  keep  the  surface  of  the  slag  cool, 
or  in  one  unequipped  to  maintain  a  rapid  rate  of  oxidation,  or  in  a  scorifier  of 


ASSAYING  FOR  GOLD   AND   SILVER  757 

smaller  size,  or  of  the  same  diameter  but  of  a  shape  which  does  not  provide 
amply  for  accumulation  of  slag  before  the  lead  becomes  covered. 

The  ratio  of  weight  of  assay  portion  to  that  of  lead  is  limited  by  the  specific 
volume  of  the  material  and  by  the  characteristic  solubility  of  the  actual  and 
potential  bases  and  of  silica  by  lead  oxide. 

The  volume  of  the  assay  portion,  except  in  the  case  of  material  which  is 
wholly  metallic,  when  mixed  intimately  with  one-half  of  the  charge  of  granulated 
lead,  should  be  no  greater  than  can  be  covered  by  the  remainder  of  the  charge,  else 
a  part  of  the  assay  portion  may  adhere  to  the  side  of  the  scorifier  out  of  contact 
with  the  slag.  The  assay  portion  should  be  no  greater  than  will  be  completely 
dissolved  by  flux  and  lead  oxide  during  the  first  few  minutes  of  the  scorifi- 
cation  with  formation  of  much  less  volume  of  slag  than  will  cover  the  molten 
lead,  else  particles  of  the  assay  portion  may  float  to  the  side  of  the  scorifier 
and  will  remain  undecomposed  because  out  of  reach  of  the  portion  of  the  slag 
which  is  in  active  circulation.  In  the  dry  or  "  all-fire  "  assay  of  metals  alloyable 
with  lead,  the  proportion  of  the  assay  portion  and  the  concentration  of  metals 
during  the  first  or  succeeding  scorifications  should  be  no  greater  than  will  allow 
of  the  ready  solution  of  the  oxides  by  lead  oxide  at  the  rate  of  its  formation,  else 
a  solid  scum  of  oxide  may  form  over  the  lead,  preventing  further  scorification;  or 
the  oxides  may  aggregate  in  pasty  lumps  which  tend  to  retain  values  in 
the  slag.  Oxidation  of  the  metals  progresses  in  approximately  the  following 
order:  iron,  zinc,  tin,  arsenic,  antimony,  lead,  cobalt,  nickel,  copper,  bismuth, 
selenium  and  tellurium.  It  is  sometimes  impracticable  to  eliminate  completely 
the  last  three  elements  from  lead  by  process  of  scorification.  Because  of  their  effect 
on  the  bead  obtained  by  cupellation,  whenever  consistent  assays  for  silver  are 
sought,  they  are  best  removed  from  the  lead  button  by  the  method  described  on 
page  772.  The  presence  of  selenium  unassociated  with  other  colored  oxides  is  indi- 
cated by  a  ruby-colored  slag.  Tellurium  gives  a  dark  stain  over  the  bottom  of  the 
scorifier.  Antimony  is  indicated  by  orange-yellow  patches  on  the  scorifier. 
Iron  gives  a  reddish  brown,  cobalt  a  brilliant  blue  and  nickel  a  light-brown 
color  to  the  scorifier  glaze.  Copper  is  oxidized  comparatively  slowly  by  scori- 
fication and  the  progress  of  its  elimination  by  repeated  scorification  is  indicated 
by  the  shade  of  the  green  glaze  on  the  scorifier.  When  the  concentration  of 
copper  in  the  lead  has  been  reduced  to  such  an  extent  that  the  lighter  shades 
of  green  are  obtained,  the  experienced  operator  is  able  to  judge  by  observation 
of  the  size  of  button  and  the  depth  of  color  of  the  scorifier  how  much  lead  is 
required  in  the  charge  for  final  scorification,  and  when  the  button  is  sufficiently 
free  of  copper  to  permit  of  cupellation.  A  10-gram  button  suitable  for  cupellation 
should  be  from  a  scorifier  which  is  no  darker  than  a  very  light  apple  green;  a 
20-gram  button  may  be  from  a  somewhat  deeply  shaded  scorifier.  If  too  little  flux, 
silica  or  borax  is  supplied  to  a  scorification,  the  scorifier  is  apt  to  be  so  deeply 
corroded  or  pitted  that  lead  will  be  retained,  while  if  too  much  borax  is  added  the 
slag  will  be  so  viscous  as  to  prevent  aggregation  of  the  particles  of  lead. 

Silica,  if  unmixed  with  the  assay  portion,  may  be  added  in  moderate  excess, 
but  may  give  some  trouble  in  pouring.  It  is  not  uncommon  practice  to  make 
a  poor  batch  of  scorifiers  usable  for  assay  of  basic  material  by  tamping  a 
layer  of  fine  silica  over  the  bottom  of  each  dish.  In  the  assay  of  basic  or 
acid  ores  or  furnace  products,  as  quick  fusion  as  possible  should  be  made.  The 
scorifiers  are  put  into  a  muffle  having  a  temperature  between  1050°  and  1100° 
C.  and  the  door  and  damper  are  closed  tightly  until  (within  ten  minutes)  the 


758  ASSAYING  FOR  GOLD   AND   SILVER 

scorifiers  are  of  the  same  temperature  as  the  muffle.  The  door  and  damper  are 
then  opened  and  by  regulation  of  the  means  of  supplying  heat,  the  scorification 
is  conducted  at  as  low  temperature  as  is  practicable,  until  experience  indicates 
that  the  buttons  are  of  the  size  desired.  The  temperature  of  the  muffle  is  then 
raised  by  closing  the  door  and  urging  the  fire  for  several  minutes,  when  the  con- 
tents of  the  scorifiers  are  poured  into  shallow  iron  moulds.  Pouring  with  certainty 
of  not  shotting  the  slag  is  made  easy  of  accomplishment  by  use  of  a  mould  no 
deeper  than  will  just  hold  the  contents  of  the  scorifier,  tongs  with  a  very  short 
prong  on  the  pouring  side  and  a  motion  which  introduces  the  greater  part 
of  the  slag  a  distinct  interval  before  the  lead  is  allowed  to  flow  without 
much  drop  into  the  middle  of  the  mould.  When  the  scorifier  remains  in 
the  furnace  for  some  time  after  the  lead  is  submerged,  the  slag  becomes 
pasty  and  tends  to  cause  more  or  less  loss  of  lead  in  pouring.  Thickening  of  the 
slag  through  entrance  of  the  constituents  of  the  scorifier  is  also  brought  about 
even  before  the  lead  is  closed  over,  when  the  scorification  is  carried  out  at  too  a 
high  a  temperature  or  under  any  condition  which  causes  corrosion  of  the  scori- 
fier at  a  greater  rate  than  the  production  of  the  quantity  of  lead  oxide  requisite 
to  keep  the  slag  fluid. 

Rescorifications  to  purify  or  concentrate  the  buttons  are  made  at  as  low  tem- 
perature as  possible.  Scorification  of  filter  paper  residues  containing  little  else  than 
gold  and  a  silver  precipitate  may  be  commenced  at  a  low  temperature,  but  such 
as  contain  sulphur  in  any  form  should  be  started  at  a  high  temperature,  else  a 
portion  of  the  sulphur  oxidizing  to  S04  forms  with  the  base  of  the  borax  flux, 
sodium  sulphate,  which  may  cover  the  lead  and  prevent  oxidation  of  the  sulphur 
which  has  combined  to  form  lead  sulphide. 

Placing  powdered  charcoal  on  the  surface  of  the  slag  before  raising  the  tem- 
perature to  pour,  is  not  an  effective  method  of  cleaning  the  slag  or  of  making  an 
assay  with  slag  correction.  Because  it  introduces  a  factor  likely  to  be  personal 
and  not  wholly  under  control,  the  practice  is  not  good  in  the  appraising  assay  of 
commercial  material. 

Type  Schemes.  The  following  are  illustrative  of  the  details  of  manipulation 
of  the  scorification  method  of  fusion,  purification  of  lead  and  preparation  of  the 
button  for  cupellation. 

Cobalt,  Nickel  Silver  Ore.  For  each  test  of  an  ore  containing  over  2000  to  4000  pz. 
per  ton,  a  button  representing  \  A.T.  is  cupelled.  For  each  test  of  an  ore  containing 
1000  to  2000  oz.  per  ton,  a  button  representing  \  A.T.  is  cupelled.  For  each  test  of 
an  ore  containing  less  than  1000  oz.  a  button  representing  1  A.T.  is  cupelled.  For 
each  test  of  the  metallic  scale,  which  is  quite  pure  silver,  a  button  representing  -£5  A.T. 
is  cupelled.  Of  the  2000  oz.  ore,  \  A.T.  is  weighed  out  and  mixed  on  smooth  paper  or 
rubber  cloth  with  90  grams  of  finely  granulated  lead  and  9  grams  powdered  borax 
glass.  The  charge  is  distributed  between  three  3-in.  scorifiers  and  each  portion  is 
covered  with  30  grams  of  lead.  Scorification,  commencing  at  a  high  temperature,  is 
continued  at  a  low  temperature  until  15-  to  20-gram  buttons  are  produced.  The  buttons 
are  combined  in  a  single  3-in.  scorifier,  and  rescorified  to  production  of  a  15-  to  20-^rum 
button  which  represents  \  A.T.  Of  the  1000  to  2000  oz.  ore,  £  A.T.  is  weighed  out, 
mixed  with  150  grams  of  lead  and  15  grams  powdered  borax,  and  distributed  annum 
five  3-in.  scorifiers.  The  content  of  each  scorifier  is  covered  with  20  grams  of  lead. 
After  scorification  to  production  of  10-  to  15-gram  buttons,  all  the  buttons  are  combined 
in  a  single  3-in.  scorifier  and  scorified  to  production  of  a  15-  to  20-gram  button.  The 
1000  oz.  or  less  ore  is  treated  in  exactly  the  same  manner  as  the  1000-  to  2000-oz.  grudo 
with  the  exception  that  two  lots  of  \  A.T.  each  are  weighed  out  and  distributed  among 
two  groups  of  five  scorifiers  each.  The  two  buttons  resulting  from  the  second  scorifica- 
tion are  combined  in  a  2^-iu,  scorifier  and  by  a  third  scorificatiou  a  single  button 


ASSAYING  FOR  GOLD   AND   SILVER  759 

representing  1  A.T.  is  produced.  Of  the  metallic  scale  TO  A.T.  is  weighed  out,  placed 
in  a  2|-in.  scorifier  with  30  grams  of  lead  and  scorified  to  production  of  a  15-  to  20- 
gram  button.  It  is  customary  in  the  case  of  nickel  silver  ore  to  report  results  on  the 
basis  of  assay  with  both  slag  and  cupel  correction,  therefore  all  the  slag  in  the  produc- 
tion of  each  bead  for  cupellation  should  be  collected,  ground  finely  and  the  whole,  or 
a  convenient  aliquot,  assayed  by  the  method  described  on  page  754. 

Assay  of  Blister  Copper  for  Gold.  For  each  test  of  \  A.T.,  five  lots  of  the  sample  of 
TO  A.T.  each  are  placed  in  three  scorifiers  and  covered  with  60  grams  lead  and  2  to  3 
grams  of  the  borax  silica  flux.  Scorification  is  continued  to  production  of  20-  to  25-gram 
buttons.  Sufficient  lead  is  added  to  each  button  to  make  the  total  charge  60  grams 
and  each  -n>  A.J.  portion  is  rescorified  until  about  20  grams  of  lead  remain  in  each  scpri- 
fier.  From  each  scorifier  the  slag  is  decanted  on  the  shelf  in  front  of  the  muffle.  With- 
out removal  from  the  furnace,  all  the  buttons  are  combined  by  pouring  into  a  single 
hot,  fresh  scorifier.  Scorification  is  continued  until  about  25  grams  of  lead  remains, 
the  temperature  is  then  raised,  the  slag  decanted  and  the  metal  poured  into  a  fresh 
scorifier  holding  40  grams  of  molten  lead.  Scorification  is  continued  to  production 
of  a  15-  to  20-gram  button.  From  the  shade  of  the  scorifier  and  size  of  the  button,  the 
operator  judges  how  much  lead  is  required  to  be  added  to  procure  from  the  fourth 
Scorification  a  button  suitable  for  cupellation.  Throughout  the  operation  the  copper 
should  not  be  allowed  to  become  so  concentrated  or  the  temperature  so  low  that  lead 
will  liquate  from  the  copper. 

Whenever  muffle  space  is  more  valuable  than  time  saved  by  combining  portions 
of  the  assay  by  pouring  from  one  scorifier  into  another  in  the  furnace,  it  is  the  bet- 
ter practice  to  pour  the  portions  into  moulds  and  combine  the  slag-free  buttons. 

Copper  Matte  for  Gold.  For  each  test  of  £  A.T.,  three  lots  of  |  A.T.  each  are  placed 
on  a  layer  of  30  grams  of  lead  in  three  3-in.  scorifiers.  The  charge  in  each  scorifier  is 
covered  with  30  grams  of  lead  and  5  grams  of  borax-silica  flux.  The  scorifiers  are  placed 
in  a  very  hot  muffle  which  is  opened  only  after  the  scorifiers  are  of  the  same  temperature. 
The  Scorification  is  continued  at  as  low  temperature  as  possible,  until  15  to  20  grams 
of  lead  remains  in  each  scorifier.  The  heat  is  then  raised  for  three  to  five  minutes 
before  pouring. 

If  the  matte  is  very  low  in  copper  the  buttons  may  be  combined  and  rescorified 
to  suitable  size  for  cupellation.  If  the  matte  contains  10%  to  20%  copper,  the  product 
of  the  second  Scorification  is  rescorified  with  sufficient  lead  to  make  the  total  charge, 
according  to  the  judgment  of  the  operator,  30  to  60  grams. 

If  the  matte  contains  20%  to  40%  copper,  each  button  of  the  first  Scorification  is 
put  into  a  fresh  3-in.  scorifier  and  sufficient  lead  added  to  make  the  charge  up  to  30 
to  60  grams.  The  product  of  the  15-  to  20-gram  buttons  of  the  second  rescorification 
are  combined  and  reduced  to  cupellation  size. 

If  the  matte  contains  40%  to  60%  copper,  the  product  of  the  third  Scorification 
is  scorified  a  fourth  time  with  addition  of  sufficient  lead  to  make  the  total  charge 
30  to  60  grams. 

If  the  matte  contains  more  than  60%  of  copper,  each  lot  of  £  A.T.  is  rescorified 
twice  with  addition  each  time  of  sufficient  lead  to  make  the  total  charge  in  each  scori- 
fier 40  to  60  grams.  The  resulting  buttons  are  combined  into  a  single  charge  for  a 
fourth  and  final  Scorification  to  a  15-  to  20-gram  button.  The  details  of  the  scheme  are 
the  same  for  the  assay  for  silver  or  gold  in  ore  of  similar  copper  content,  except  that 
several  grams  of  borax  are  mixed  with  the  charge  to  flux  the  initial  fusion. 

1  Tin  Concentrates  for  Gold  and  Silver.     For  each  test,  1  A.T.  mixed  with  200- 
grams  test  lead,  100  grams  litharge  and  30  grams  borax  on  smooth  paper,  rubber  or  oil 
cloth,  is  distributed  among  ten  3-in.  scorifiers  and  each  charge  covered  with  30  grams  lead. 
Scorification,  commenced  at  a  high  temperature,  is  continued  low  until  the  lead  is  covered 
over.     The  resulting  buttons  are  pounded  free  of  adherent  slag,  distributed  among 

2  or  3  scorifiers  and  rescorified.     When  the  lead  has  been  reduced  in  each  to  15  to 
20  grams,   the   charges  may  be  poured  and  the  resulting  buttons  combined  and 
scorified  to  a  final  button;  or  the  slag  maybe  poured  off  and  all  the  lead  poured  into 
a  single  scorifier.      This  method  is  also   adapted  to  the  assay  of  highly  silicious 
material. 

The  methods  described  may  be  modified  in  the  following  details:  For  purpose  of 
accounting,  factory,  mine  or  mill  control,  or  by  agreement  between  buyer  and  seller, 
the  button  to  be  cupelled  may  represent  a  smaller  portion;  because  it  is  difficult  to 
pick  from  the  cupel  and  clean  very  small  silver  beads,  cupellation  of  a  portion  repre- 


760  ASSAYING  FOR   GOLD   AND   SILVER 

senting  two  or  more  A.T.  may  be  undertaken.  When  scorifiers  are  of  uncertain  quality, 
it  is  the  better  practice  to  weigh  out  the  portion  designed  for  each  scorifier  and  mix 
the  flux  and  lead  with  spatula  with  the  charge. 

CUPELLATION 

Cupels  are  best  made  by  a  cupel  machine  from  perfectly  dry  cupel  bone  ash. 
Cupels  so  made  can  be  used  immediately  after  manufacture.  If  water  is  employed 
to  make  the  bone  ash  coherent,  cracking  is  liable  to  occur  on  exposure  to  muffle 
temperature  unless  the  cupels  are  dried  out  very  slowly  by  allowing  them  to  stand 
in  a  warm,  dry  spot,  days  or  weeks  according  to  the  amount  of  water  used.  When 
a  brand  of  bone  ash  makes  a  dry  pressed  cupel  which  is  inclined  to  crack  or  split, 
this  tendency  is  overcome  by  admixture  of  the  unsaturated  portion  of  old  cupels  or 
of  bone  ash  which  has  been  heated  in  a  muffle  to  about  1000°  C.  Bone  ash 
which  evidently  has  not  been  completely  decarbonized  should  not  be  used,  because 
complete  oxidation  of  its  content  of  organic  matter  requires  that  the  cupels  be 
kept  hot  for  a  long  period  before  commencing  cupellation,  else  spurting  of  molten 
lead  will  take  place  during  the  operation.  When  the  form  of  the  saturated  portion 
of  the  cupel  show,  that  lead  oxide  is  not  absorbed  freely,  an  unsatisfactory  quality 
of  bone  ash  is  indicated.  The  bottom  of  the  saturated  portion  of  a  well-made  cupel 
of  bone  ash  of  first  class  quality  is  concave  in  shape,  free  of  knobs  or  projections, 
and  can  be  cleanly  separated  by  hand,  with  exercise  of  little  effort,  from  the  unsat- 
urated portion.  The  proportion  of  the  different  sizes  of  particles  of  bone  ash  is  a 
matter  of  consequence.  Cupels  made  wholly  of  very  fine  particles  are  apt  to  be  too 
dense,  unless  moulded  with  so  little  pressure  that  they  are  so  fragile,  that  their 
manipulation  must  be  conducted  with  great  care.  Those  made  entirely  of  coarse 
particles  (through  40  and  left  on  60  mesh)  have  such  a  rough  cup  surface  that 
the  cupellation  loss  is  excessive  and  not  uniform. 

A  very  satisfactory  cupel  is  made  from  bone  ash  which  contains  approximately 
75%  of  particles  which  will  pass  a  100-mesh  screen  and  the  remaining  25%  finer 
than  40  mesh. 

The  following  shows  the  range  of  screen  analyses  of  samples  taken  from  28  barrels 
of  the  same  brand : 

Per  Cent. 

Left  on  40  mesh 0-8.7 

Through  40  left  on  60  mesh 2.2-6.3 

Through  60  left  on  70  mesh 3.7-9.6 

Through  80  left  on  100  mesh 12.5-20.3 

Through  100  mesh 59.1-83.2 

Samples  from  seven  of  the  barrels  wet-screened  through  a  200-mesh  sieve  gave 
Quantities  of  fine  product  ranging  from  42%  to  58%. 

Patent  and  ready-made  cupels,  in  which  magnesium  or  calcium  oxides, 
plaster  of  Paris,  Portland  cement  or  organic  matter  may  enter  as  constituents, 
because  they  will  survive  shipment,  are  of  use  in  situations  where  the  manufacture 
of  the  laboratory-moulded  cupel  is  impracticable.  When  silver  beads  of  997- 
998  fineness  are  obtained  from  such  cupels,  the  cupellation  loss  is  usually  greater 
than  is  common  from  bone  ash  cupels  of  normal  quality. 

The  patent  cupels  require  the  higher  temperature  generally  throughout,  always 
at  the  finish  of  the  operation,  else  freezing  will  take  place,  or  beads  will  be 
obtained  which  may  retain  quite  as  much  lead  as  will  balance  the  normal  loss  of 
silver. 


*  ASSAYING  FOR  GOLD  AND   SILVER  761 

The  brands  of  patent  cupels  which  preserve  a  smooth,  hard  surface  after 
cupellation  will  retain  a  trace  of  silver  (0.10  milligram  or  less)  in  easily  dis- 
coverable form.  This  amount  is  difficult  to  find  in  a  bone  ash  cupel  unless 
made  entirely  or  cup  finished  with  a  grade  of  very  fine  quality. 

While  a  bone  ash  cupel  absorbs  practically  its  own  weight  of  lead  in  the  form  of 
lead  oxide,  it  is  well  to  make  the  size  such  that  the  saturated  portion  will  not  reach 
quite  to  the  bottom.  A  cupel  f  in.  in  height,  1  in.  in  diameter  is  suitable  for  a 
12-gram  button;  1  in.  in  height,  1|  ins.  diameter  for  a  20-gram  button;  1  in.  in 
height  1|  in  diameter  for  a  25-gram  button. 

The  cup  of  the  cupel  should  be  perfectly  smooth  and  free  of  any  particles  of 
loose  bone  ash.  Such  particles  as  may  adhere  may  be  removed  by  blowing  on 
them.  Loosening  the  particles  by  the  finger  may  roughen  the  surface  and  increase 
the  cupellation  loss. 

The  lead  button  is  prepared  for  cupellation  by  freeing  it  all  of  adherent  par- 
ticles of  slag.  Presence  of  slag  corrodes  the  cupel.  It  is  pounded  on  a  smooth 
anvil  with  a  flat-faced  hammer  and  then  shaped  into  a  cube  or  disk  which  will 
fit  the  cupel  and  be  firmly  held  by  the  tongs.  It  is  good  practice  to  round  the 
corners  of  the  button.  A  soft,  brittle  button  may  result,  through  the  presence 
of  lead  oxide  in  its  composition,  from  completion  of  scorification  at  too  low  a 
temperature.  A  button  containing  more  than  25%  of  silver  or  gold  is  bril- 
liantly smooth,  hard  and  brittle.  Selenium  or  tellurium  in  considerable  quantity 
makes  the  button  rough,  brittle  and  difficult  to  separate  from  the  slag.  A 
small  quantity  of  sulphur  will  make  the  surface  of  the  button  scale.  Arsenic 
and  antimony  have  a  similar  effect. 

Operation.  In  a  small  or  low-formed  muffle,  cupellation  of  only  a  single  or 
possibly  two  rows  of  cupels  placed  near  the  front  can  be  carried  out  successfully. 
When  cupellation  is  carried  out  in  a  single  row  near  the  front,  the  position  and 
shape  of  the  row  is  determined  by  experience.  Besides  regulation  of  fuel  supply, 
temperature  of  the  cupel  is  controlled  by  placing  scorifiers  or  old  cupels  in  front 
and  back  of  the  row  and  by  manipulation  of  the  muffle  door  and  damper.  Large 
and  small  buttons  can  be  cupelled  simultaneously  by  this  method.  Because 
the  action  tends  to  increase  silver  loss  into  the  cupel,  a  cupel  should  not,  while 
cupellation  is  in  progress,  be  moved  in  a  manner  which  will  cause  change  of 
position  of  the  metal  in  the  cup.  In  a  muffle  high  enough  to  allow  view  of 
metal  inside  of  a  cupel  placed  near  the  back  wall  and  of  size  large  enough  to  be 
unaffected  quickly  by  small  heat  changes,  cupellation  is  conducted  in  a  series  of 
rows  of  cupels  extending  from  close  to  the  back  wall  to  within  4  or  5  ins.  of  the 
front.  To  hold  the  heat  in  the  front  and  back  rows,  it  is  common  practice  to 
bank  against  the  cupels  in  these  rows  bone  ash,  old  cupels,  scorifiers  or  pieces  of 
thin  brick.  Some  operators  make  it  possible  to  do  very  artistic  feathering  by 
building  a  dam  of  bone  ash  several  inches  high  near  the  door  of  the  muffle  to 
break  and  heat  the  current  of  air  over  the  cupels.  Cupellation  by  this  method 
should  be  of  buttons  of  nearly  uniform  size. 

Entrance  of  the  products  of  combustion  to  the  muffle  retards   cupellation. 

By  nice  adjustment  of  temperature  previous  to  commencement  of  the  opera- 
tion in  a  large  muffle  carrying  many  cupels,  little  regulation  of  the  fuel  supply  is 
required.  Heat  effects  are  produced  by  manipulation  of  the  muffle  door  and  of 
I  in.  thick  cooling  irons  with  3-ft.  handles.  The  irons  are  shovel  shaped  to  cool 
the  entire  top  of  the  muffle  and  of  rectangular  form  to  cool  a  single  lateral  or  longi- 
tudinal row.  During  the  early  part  of  the  operation  heat  is  supplied  and  tempera- 


762  ASSAYING  FOR  GOLD   AND   SILVER 

ture  raised  by  oxidation  of  the  lead  in  the  cupels.  Toward  the  end  of  the  opera- 
tion, the  rise  of  temperature  produced  by  moderate  reduction  of  the  rate  of  flow 
of  air  through  the  muffle,  together  with  the  heat  retained  by  the  closely  packed 
cupels  is  usually  sufficient  to  produce  silver  beads  of  standard  purity,  when  the 
cupels  are  of  good  quality. 

Previous  to  commencement  of  the  operation,  to  expel  moisture,  burn  organic 
matter,  decompose  CaCOa  in  the  cupels,  to  give  them  time  to  gain  a  temperature 
uniform  with  the  atmosphere  of  the  closed  muffle  and  to  permit  the  furnace  as 
a  whole  to'acquire  a  condition  of  temperature  and  equilibrium  of  flow  of  heat  which 
will  allow  control  of  muffle  temperature  without  application  of  extreme  methods 
of  heating  or  cooling,  the  cupels  in  the  tight  muffle  should  be  brought  to  and 
allowed  to  remain  for  at  least  ten  minutes  at  a  temperature  only  very  little  above 
that  which  will  cause  scum  of  oxide  on  the  surface  of  molten  lead  to  melt  and  be 
absorbed  by  the  cupel  material. 

"  The  temperature  of  cupellation  of  pure  lead  buttons  should  be  850°  C.  to 
uncover  the  button;  this  may  be  lowered  to  770°  C.  during  the  major  part  of  the 
cupellation,  but  must  be  raised  to  about  830°  C.  near  the  end  to  finish  the  opera- 
tion." * 

The  muffle  damper  being  closed,  the  lead  buttons  are  placed  in  the  cupels  in 
the  order  of  the  numbers  on  the  scorifiers  in  a  tray.  The  muffle  door  is  closed 
until  the  lead  in  all  the  cupels  will  "  uncover  "  or  "  drive."  Immediately  the 
damper  is  opened  somewhat.  >  •  •  • 

The  temperature  of  the  top  of  the  cupel  is  then  cooled  by  the  methods  mentioned 
until  the  appearance  of  the  margin  of  the  molten  metal  within  the  cupel  and  the 
color  of  the  saturated  portion  of  the  cupel  indicates  to  the  experienced  operator 
that  a  fringe  of  crystalline  or  "  feather  "  litharge  is  forming  just  above  the  lead. 
If  the  cooling  is  carried  too  far,  the  cupel  becomes  too  cold  to  absorb  the  litharge 
and  "  freezing  "  is  the  result.  Approach  to  this  condition  is  manifested  by  the 
tendency  of  the  line  of  juncture  of  metal  and  cupel  to  appear  indefinite.  If, 
in  an  attempt  to  raise  the  temperature  of  a  charge  of  cupels,  the  flow  of  air  through 
the  furnace  is  stopped,  cupellation  will  cease  because  a  coating  of  solid  oxide  will 
form  on  the  surface  of  the  lead  which  will  require  a  considerable  rise  of  tempera- 
ture to  melt.  The  operation  of  alternately  cooling  and  allowing  the  temperature 
to  rise  is  continued  until  little  lead  remains.  As  the  quantity  of  lead  and  the  heat 
imparted  to  the  cupel  through  its  oxidation  diminishes,  the  temperature  of  the 
cupel  must  be  increased  until  at  the  moment  when  the  silver-gold  bead  is  prac- 
tically free  of  lead,  the  temperature  should  be  close  to  that  at  which  cupellation 
was  started.  If  the  temperature  is  too  high  at  this  moment  the  silver  bead  will 
not  at  once  solidify  and  while  molten  will  asborb  oxygen.  When  the  bead  solid- 
ifies, the  oxygen  is  expelled  with  the  projection  of  rough  points  on  the  bead  and 
sometimes  of  particles  entirely  separate  from  the  bead.  The  tendency  to  "  sprout  " 
or  "  spurt  "  increases  with  the  size  of  the  beads.  When  a  cupel  is  kept  in  a  muffle 
at  a  high  temperature  for  a  considerable  period  previous  to  commencement  of 
cupellation,  the  silver  bead  exhibits  a  tendency  to  remain  liquid  at  a  temperature 
far  below  the  normal  freezing-point  of  silver.  The  same  inclination  is  also  quite 
characteristic  of  cupellation  in  a  dense  cupel  of  fine  bone  ash.  When  such  a 
bead  solidifies  the  expulsion  of  oxygen  has  been  known  to  be  so  violent  as  to  break 
the  beads  apart.  When  a  bead  is  induced  to  become  solid  by  taking  the  cupel 
out  of  the  muffle  and  giving  it  a  series  of  shocks,  if  sprouting  does  not  take  place, 
1  Fulton,  "  Fire  Assaying,"  2d  ed.,  41. 


ASSAYING  FOR  GOLD   AND   SILVER  763 

the  bead  is  often  found  to  be  hollow.  Silver  loss  tends  to  increase  with  length  of 
time  that  the  bead  remains  in  a  state  of  suffusion.  Rootlets  extending  into  the  cupel 
are  peculiar  to  beads  which  have  been  in  this  state.  A  silver  bead  having  once 
solidified  in  its  cupel  does  not  require  immediate  removal  from  the  furnace,  but  may 
remain  for  any  reasonable  period  without  loss  or  gain  of  weight,  providing  the  tem- 
perature of  the  cupel  is  not  raised  so  high  that  its  fringe  of  feather  litharge  is  melted. 
If  the  temperature  is  too  low  during  the  oxidation  of  the  last  portion  of  the  lead, 
"  freezing  "  with  accumulation  of  unabsorbed  litharge  is  likely  to  occur.  Solidi- 
fication of  a  lead  silver  alloy  which  forms  a  flat  dull-colored  bead  with  smooth  under 
surface  and  is  non-adherent  to  the  cupel,  may  sometimes  occur.  This  alloy  may 
contain  as  much  as  10%  of  lead.  Because  the  heat  of  oxidation  of  copper  is  greater 
than  that  of  lead,  freezing  is  less  likely  to  occur  in  the  cupellation  of  buttons  con- 
taining no  greater  quantity  of  copper  than  is  suited  to  the  process. 

Except  when  the  bead  contains  more  than  20%  of  gold,  it  should  be  silvery 
white,  globular  and,  when  hot,  adherent  to  the  cupel.  As  the  ratio  of  gold  in- 
creases, unless  the  cupellation  is  finished  at  a  high  temperature,  the  bead  is  apt  to  be 
dull  on  account  of  retained  lead,  or  copper  when  that  metal  is  present  in  the  button. 

An  indented  bead  if  silvery  white  is  not  an  indication  of  impurity,  but  if  the 
luster  is  dull  the  presence  of  bismuth,  copper,  selenium  or  tellurium  may  be 
suspected.  Bismuth  in  moderate  quantity  (a  few  tenths  per  cent  of  the  lead  alloy) 
is  taken  up  by  large  beads  to  such  an  extent  that  the  bismuth  content  may  more 
than  balance  the  excessive  cupellation  loss  on  account  of  its  presence.  Through 
the  inclination  to  leave  particles  of  the  precious  metal  on  the  sides  of  the  cupel,  the 
excessive  loss  may  exhibit  itself  in  the  case  of  small  beads.  Copper  being  absent, 
bismuth  produces  a  brownish  stain  under  the  silver  bead  and  dark  green  rings 
about  it.  When  a  large  quantity  of  bismuth,  selenium  or  tellurium  is  present 
the  surface  tension  of  the  silver  bead  is  diminished  to  such  an  extent  that  it  may 
spread  over  the  surface  and  into  the  bottom  of  the  cupel.  These  impurities  in 
lesser  quantity  modify  the  appearance  of  the  silver  bead  according  to  the  amount 
of  silver  and  the  finishing  temperature  of  the  cupellation.  In  the  assay  for  gold, 
the  result  obtained  from  parting  the  product  of  cupellation  of  a  tellurium-bear- 
ing bead  is  usually  higher  than  that  obtained  by  removal  of.  tellurium  by  wet 
methods.  Recupellation  is  of  necessity  occasionally  resorted  to  in  order  to  obtain 
a  silver  bead  sufficiently  pure  to  favor  the  production  of  a  gold  mass  which  can 
be  collected  in  the  process  of  parting. 

The  presence  of  a  large  proportion  of  silver  decreases  the  gold  loss  especially 
in  the  cupellation  of  buttons  containing  selenium  or  tellurium.  In  the  assay  for 
silver  and  for  silver  and  gold  in  bismuth-bearing  material,  selenium,  tellurium 
and  bismuth  should  be  separated  by  the  combination  method  described  on 
page  772. 

Copper  eliminated  before  the  last  of  the  lead  causes  no  abnormal  cupellation 
loss.  When  its  proportion  in  the  lead  button  is  large  enough  to  extend  the  dark 
stain  on  the  cupel  to  the  seat  of  the  bead,  but  insufficient  to  prevent  cupellation 
with  "  feathers,"  the  cupellation  loss  is  somewhat  more  than  normal  when  the 
final  temperature  is  hot  enough  to  bring  about  a  bead  of  standard  purity.  But 
if  the  ratio  of  gold  to  silver  is  low  in  the  bead  or  the  final  temperature  is  not  high, 
copper  may  be  retained  in  the  bead  in  quantity  sufficient  to  offset  a  part  or  more 
than  the  whole  of  the  abnormal  amount  of  silver  absorbed.  No  attempt  should 
be  made  to  cupel  a  lead  button  containing  a  greater  proportion  of  copper  than  will 
allow  cupellation  with  "  feathers."  Antimony  to  the  extent  of  2%  may  be  present 


764 


ASSAYING  FOR  GOLD   AND  SILVER 


in  the  lead  button.1  A  large  quantity  produces  scoria  and  causes  cracking  of  the 
cupel.  The  presence  of  antimony  and  any  of  the  base  metals  whose  oxides  are 
not  very  soluble  in  lead  oxide  causes  large  and  not  uniform  loss  of  the  precious 
metals  into  the  cupel  because  of  the  high  heat  required  to  start  and  sometimes  to 
continue  cupellation,  and  through  retention  of  particles  in  the  scoria  of  oxide 
about  the  sides  of  the  cupel. 

The  presence  of  platinum  or  palladium  raises  the  temperature  of  the  melting- 
point  of  the  silver-gold  alloy  and  increases  the  tendency  to  retain  lead  by  the 
product  of  cupellation.  The  presence  of  but  a  very  small  proportion  of  either 
gives  a  steely  hue  to  the  silver  bead.  With  increase  of  proportion  of  the  platinum 


1.7 
1.6 
1.5 
1.4 
1.3 

8   1.1 
J   1.0 

£0.9 

is 

I  0.5 


01 


4.0 


3.0 


1.0 


10       20       30      40       50      60       70       80       90     100 
MILLIGRAMS  SILVER  CUPELED  WITH  15GMS.TEST 
LEAD 

FIG.  141. 

metals  and  influenced  by  the  final  temperature  of  cupellation,  the  bead  becomes 
flat,  its  [surface  dull,  crystalline,  rough  or  irregular  and  its  color  gray  or  almost 
black.  The  effect  of  either  metal  alone  is  similar  but  not  exactly  alike.  Palladium 
shows  a  tendency  to  produce  beads  of  less  luster,  darker  in  color  and  of  more  irreg- 
ular surface. 

Since  the  freezing-point  of  the  silver-gold  alloy  increases  rapidly  with  the  per- 
centage of  gold,  care  is  required  when  the  ratio  of  silver  to  gold  is  less  than  6  to  1, 
that  the  final  temperature  of  cupellation  be  higher  than  is  required  to  obtain  a 
gold-free  silver  bead  of  standard  purity. 

Loss  of  both  gold  and  silver  into  the  cupel  increases  with  the  quantity  of  lead 
used.  Custom  and  convenience  have  made  it  the  very  common  practice  to  carry 
out  cupellation  on  buttons  of  15  to  25  grams,  resulting  from  crucible  fusion,  and 
on  those  between  10  and  20  grams  which  are  the  product  of  scorification. 
Amount  of  lead  remaining  constant,  cupellation  loss  of  silver  decreases  in  per- 
centage with  increase  of  quantity.  Chart  Fig.  141  is  the  product  of  several  hun- 
dred cupellations,  chiefly  of  pure  silver,  made  in  the  course  of  trials  of  different 
brands  and  graded  mixtures  of  bone  ash  and  other  experiments.  The  lead  used 
was  reduced  from  litharge  made  from  the  best  grade  of  test  lead;  200  grams  gave  an 
unweighable  amount  of  silver  and  bismuth.  The  beads  assayed  996.5-998  fineness. 
1 E.  A.  Smith,  "Sampling  and  Assaying  of  Precious  Metals,"  168. 


ASSAYING  FOR  GOLD   AND   SILVER  765 

Temperature  higher  than  is  required  to  produce  "  feather  "  litharge  increases 
the  loss  of  silver  and  gold.  The  effect,  however,  of  temperature  of  cupellation 
on  small  quantities  of  gold  alloyed  with  silver  is  so  little  that  ordinarily 
when  the  assay  is  for  gold  alone  care  is  only  taken  that  the  bead  does  not 
"  spurt." 

Weighing  the  Beads.  Error  may  be  introduced  in  the  assay  for  silver  through 
lack  of  care  in  cleaning  particles  of  bone  ash  from  the  bead.  The  bottom  of  the 
bead  held  firmly  by  pliers  is  scoured  with  a  bristle  assay  brush  before  weighing. 
Weighing  of  the  silver  bead  is  made  to  the  tenth  or  twentieth  milligram  and  on 
a  button  or  assay  balance  sensitive  to  one  or  two  hundredths  of  a  milligram. 
In  the  assay  of  low-grade  material,  appraised  in  large  parcels,  and  when  the  accu- 
racy of  the  method  warrants  such  action,  weighings  are  made  to  the  hundredth 
milligram  on  a  gold  assay  balance. 

To  check  balance  and  mathematical  errors  it  is  common  practice  to  weigh  and 
record  separately  each  bead  and  then  the  combination  of  all  the  beads  from 
the  same  sample. 

Direct  cupellation  is  applied  to  the  assay  for  silver  in  lead,  and  preliminary 
assay  of  base  and  Dore*  bullion,  when  no  sulphur-  or  scoria-forming  metals  and  but 
a  few  hundredths  per  cent  of  selenium  and  tellurium  enter  into  their  composition. 
When  such  impurities  are  present  in  lead  bullion,  10  grams  each  of  lead  and  lith- 
arge and  2  or  3  grams  borax-silica  flux  are  added  and  the  test  portion  subjected 
to  long  enough  scorification  to  produce  a  15-gram  button  whether  1  or  J  A.T.  be 
taken  for  the  assay  portion. 

Lead  bullion  which  contains  no  impurity  interfering  with  cupellation  is  cupelled  in 
portions  of  \  A.T.  each.  Each  portion  is  wrapped  in  a  2-in.  square  of  assayer's  sheet 
lead  which  weighs  about  7  grams.  Cupellation  is  carried  out  under  conditions  which 
favor  the  production  of  feather  litharge.  Correction  for  slag  and  cupel  loss  is  applied 
in  the  assay  of  lead  bullion  usually  by  direct  assay  of  cupel  and  slag,  but  sometimes 
from  the  loss  sustained  by  a  similar  and  known  quantity  of  silver  cupelled  or  scorified 
at  the  same  time  and  under  exactly  the  same  conditions. 

Cupellation  of  base  or  Dore  bullion  is  most  commonly  practiced  to  prepare  the 
assay  portion  for  the  parting  process,  and  as  a  convenient  method  of  making  the  trial 
assay  preliminary  to  performance  of  some  form  of  the  Gay-Lussac  method  of  determi- 
nation of  silver.  Settlement  assays  for  silver  are,  however,  sometimes  made  on  the 
purer  grades  of  bullion  by  the  cupellation  method. 

A  preliminary  assay  of  500  milligrams  of  the  sample  is  made  by  wrapping  that 
quantity  with  15  or  25  grams  of  assay ers'  sheet  lead  and  cupelling  with  feathers  if  pos- 
sible. The  experienced  operator  judges  from  the  quantity  of  silver  and  gold  present, 
from  the  stain  on  the  cupel  and  from  the  appearance  of  the  bead,  how  much  copper  is 
present  and  how  much  lead  to  add.  To  prevent  "  spurting  "  some  prefer  to  add 
a  definite  amount  (less  than  10%)  of  copper  to  bullion  which  contains  none.  The 
suitable  amount  of  lead  to  employ  in  the  cupellation  may  be  calculated  by  multiplying 
the  copper  present  in  grams  by  100  and  adding  2  when  the  copper  is  less  than  20% 
of  the  bullion;  multiplying  by  40  and  adding  8  when  the  copper  content  is  between 
20  and  60%;  multiplying  by  20  and  adding  14  when  the  per  cent  of  copper  is  over  60. 
As  an  illustration,  a  500-milligram  assay  portion  containing  no  copper  is  cupelled  with 
2  grams  lead,  while  such  containing  50,  200  or  450  milligrams  of  copper  would  be 
cupelled  with  7,  16  and  23  grams  of  lead  respectively.  One  or  two  check  portions  are 
made  containing  the  same  amounts  of  silver,  gold  and  copper  as  were  determined  by  the 
preliminary  assay.  In  making  up  the  checks,  the  silver  weighed  up  in  the  preliminary 
assay  is  corrected  for  cupellation  loss  by  adding  in  the  case  of  base  bullion  1.25%  to  its 
weight.  Gold  under  1%  of  the  silver  is  not  ordinarily  included  in  the  check  assays 
when  silver  only  is  to  be  taken  account  of. 

The  check  and  two  or  more  assay  portions  are  cupelled  each  with  the  same  amount 
of  lead  at  the  same  time  and  under  as  precisely  the  same  conditions  as  it  is  possible 
to  obtain.  In  calculating  fineness  the  average  of  the  silver  and  the  gold  found  in  the 


766  ASSAYING  FOR  GOLD   AND   SILVER 

assay  portion  is  corrected  by  the  actual  loss  or  gain  sustained  by  each  precious  metal 
in  the  check  portions. 

In  making  the  cupellation,  conditions  of  temperature  and  draft  which  will  affect 
all  the  cupels  uniformly  are  sought  rather  than  the  production  of  feather  litharge. 
The  temperature,  however,  should  not  be  so  high  that  the  beads  are  likely  to  sprout. 
Less  confidence  is  placed  in  results  from  check  portions  which  show  a  gain  than  in  those 
which  show  a  loss,  when  it  is  apparent  that  the  loss  is  not  mechanical. 

PARTING 

To  the  process  of  separating  gold  from  silver  in  such  form  that  it  can  be  col- 
lected and  weighed  with  certainty  and  facility,  the  action  of  suitably  diluted  nitric 
acid  is  better  adapted  than  that  of  sulphuric  acid.  On  account  of  the  solubility 
of  platinum  in  its  silver  gold  alloy  by  nitric  acid,  parting  with  hot  sulphuric  acid 
is  used  only  when  the  assay  is  intended  to  include  that  metal.  Except  by  employ- 
ment of  methods  of  manipulation  and  treatment  practiced  in  the  assay  of  gold 
bullion,  silver  does  not  dissolve  with  sufficient  completion  from  beads  in  which 
the  ratio  of  silver  to  gold  is  less  than  4  or  5  to  1.  When  this  ratio  is  natural 
to  the  material  undergoing  assay,  the  bead,  after  weighing,  may  be  cupelled  with 
several  grams  of  lead  after  addition  of  about  10  parts  silver.  It  is  the  better 
and  more  commonly  followed  procedure  when  low  ratios  prevail,  because  a  high 
proportion  of  silver  in  the  bead  tends  to  prevent  gold  loss  into  the  cupel,  to  make 
a  separate  assay  for  gold,  and  add  about  ten  times  as  much  silver  as  gold  present 
to  the  assay  portion  at  some  period  previous  to  cupellation. 

Nitric  acid  and  water  used  in  parting  should  be  free  of  any  form  of  chlorine 
or  other  halogen,  and  of  the  presence  of  another  acid.  The  gold  mass  in  the 
operation  is  somewhat  more  conveniently  handled  if  the  silver  bead  be  flattened 
somewhat.  But  flattened  buttons  containing  large  amounts  of  gold  (over  50 
milligrams)  appear  to  require  annealing  to  obtain  an  uniform  parting  loss.  The 
gold  mass  is  less  liable  to  break  up  if  the  bead  is  dropped  into  hot  than  into  cold 
acid.  It  is  more  apt  to  be  coherent  when  the  silver  is  dissolved  in  a  high  than  in 
a  low  column  of  acid.  On  account  of  the  solvent  action  on  gold  in  spongy  form 
by  hot  nitric  acid  of  a  strength  approaching  1.42  sp.gr.,  parting  solutions  should 
never  be  allowed  to  become  so  highly  concentrated. 

The  following  methods  are  employed  in  a  laboratory  which  has  investi- 
gated the  solvent  effect  of  the  acids  and  the  purity  of  the  gold  masses  pro- 
duced. All  the  heating  operations  are  conducted  on  a  f-in.  copper  plate 
covered  with  strips  of  asbestos  paper  and  heated  by  lateral  rows  of  perforated 
pipe  burners.  The  gas  supply  to  each  burner  is  separately  controlled.  The  silver 
bead  containing  less  than  2  milligrams  of  gold  is  dropped  into  25  cc.  of  hot  acid 
of  1.07  sp.gr.  (1  part  1.42  sp.gr.  acid  and  6  parts  water)  in  a  1  oz.  casserole  and  the 
liquid  is  kept  a  little  below  the  boiling-point  for  forty  minutes.  The  gold  mass 
is  washed  with  water  by  decantation  three  times,  dried  and  annealed  by  plac- 
ing the  casserole  over  a  Bunsen  flame  until  change  of  color  of  the  mass.  A  silver 
bead  containing  more  than  2  milligrams  and  less  than  10  is  dropped  into  25  cc. 
of  hot  acid  of  1.04  sp.gr.  (1  part  strong  acid  and  9  parts  water)  in  a  1-oz.  casserole. 
When  visible  action  has  ceased,  the  silver  solution  is  decanted,  the  casserole  filled 
up  with  acid  of  1.16  sp.gr.  and  the  gold  mass  digested  for  fifteen  to  twenty  minutes 
at  a  temperature  a  little  below  the  boiling-point.  When  the  quantity  of  gold 
is  more  than  10  milligrams,  the  two-strength  acid  treatment  is  carried  out  in  a 
2-oz.  parting  flask.  During  the  final  treatment  the  acid  is  kept  boiling  gently 
for  twenty  minutes.  After  decantation  of  the  acid  liquid,  the  flask  is  filled  up 


1  ASSAYING   FOR  GOLD  AND   SILVER 


767 


to  the  brim  with  water,  the  brim  closed  with  the  cup  of  a  1-oz.  casserole,  the  flask 
quickly  inverted  and  tapped  to  dislodge  particles  of  gold  from  the  side.  The  flask 
is  raised  until  the  brim  is  near  the  surface  and  removed  with  a  quick  motion  to 
the  side.  The  gold  mass  is  then  washed,  dried  and  annealed. 

When  platinum  and  palladium  are  present  the  gold  mass  is  apt  to  break  up  into 
dark-colored  particles,  coarse  or  very  fine,  according  to  the  proportion  of  the  plat- 
inum metals.  Selenium  or  tellurium  in  the  bead  will  also  produce  a  similar  effect. 
When  gold  only  is  to  be  determined,  the  single  1  to  6  acid  treatment  in  a  casserole  is 
pursued;  but  if  platinum  is  to  be  determined  the  parting  with  1  to  6  acid  takes  place 
in  a  flask  or  covered  beaker.  The  residue  is  transferred  to  a  filter,  about  20  parts 
of  silver  added,  the  filter,  covered  with  25  grams  of  lead  in  a  small  scorifier.  is 


•H^P^^MMI 


FIG.  142. 


incinerated,  scorified,  cupelled  and  parting  repeated.  These  operations  may 
require  repetition  several  times  before  the  coherency  and  color  of  the  gold  mass 
indicates  absence  of  platinum.  The  presence  of  even  0.05  milligram  of  palladium 
gives  a  yellow  hue  to  20  cc.  of  parting  liquor.1 

Gold  is  usually  weighed  to  hundredths  milligram.  When  the  demand,  the 
sensitiveness  of  the  balance  and  the  accuracy  of  the  method  of  assay  warrant 
such  procedure,  weighings  to  thousandths  milligram  are  made.  The  low-column 
type  of  gold  balance  is  in  every  way  superior  to  the  high.  The  weights  and 
riders  employed  should  be  frequently  checked  by  a  set  which  has  been  verified 

1  For  methods  of  treatment  of  the  parting  liquor  for  determination  of  platinum 
refer  to  chapter  on  Platinum,  also  see  article  by  A.  M.  Smoot,  Eng.  and  Min.  Jour., 
April  17,  1915. 


768 


ASSAYING  FOR  GOLD   AND   SILVER 


by  the  Bureau  of  Standards.1  To  lessen  balance  and  other  errors,  it  is  common 
practice  to  obtain  the  weight  of  each  in  turn  and  finally  all  of  the  gold  masses 
from  the  same  sample  without  removal  of  any  from  the  balance  pan. 

Gold  Bullion.  A  preliminary  assay  of  500  milligrams  is  made  to  determine  very 
closely  the  gold  and  silver  content.  The  weighed  quantity  of  standard  silver  to  be  added 
to  make  the  ratio  of  silver  to  gold  in  the  trial  assay  between  2.5  and  2  to  1,  can  usually 
be  judged  from  the  color  of  the  gold.  When  the  gold  contains  no  copper,  50  milligrams 
should  be  added  and  the  same  quantity  used  in  the  final  assay.  The  function  of  the 
copper  is  to  toughen  the  gold  silver  alloy  and  make  possible  its  reduction  by  jewelers 
rolls  to  sheet  form  without  cracking.  The  cupellation  of  the  trial  assay  is  with  10 
grams  of  lead  and  at  a  temperature  slightly  above  that  which  will  obtain  feather  lith- 
arge. The  button  is  thoroughly  cleaned  with  a  button  brush,  weighed  and  rolled 
into  a  fillet  about  2  ins.  long.  During  rolling,  softening  or  annealing  by  heating  to  dull 
redness  may  occasionally  be  required  to  prevent  cracking.  The  fillet  is  finally  annealed, 
rolled  into  a  "  cornet  "  and  parted  in  a  parting  flask  by  digestion  for  thirty  minutes 
with  25  to  30  cc.  of  1.16  sp.gr.  acid  at  just  under  the  boiling-point.  The  solution  of 
silver  is  decanted  and  washed  once  by  decantation,  25  to  30  cc.  more  of  1  to  2  acid  are 
added  and  digestion  continued  for  thirty  minutes  longer.  The  gold  is  transferred  to 
a  porcelain  casserole  in  the  manner  already  described,  washed  by  decantation  several 
times,  dried  and  annealed.  If  the  attempt  is  made  to  dry  the  gold  mass  on  a  too 
hot  plate,  particles  are  liable  to  be  scattered.  The  weight  of  the  gold  found  and  that 
of  the  added  silver  subtracted  from  the  weight  of  the  bead  is  closely  the  silver  content 
of  the  bullion.  The  silver  plus  the  gold  content  subtracted  from  the  amount  of  bul- 
lion taken  for  the  trial  assay  gives  approximately  the  quantity  of  base  metal  present. 
When  copper  is  present  in  a  bullion  or  alloy  containing  much  base,  it  should  be  deter- 
mined by  separate  analysis. 

To  two  or  more  assay  portions  of  500  milligrams  each  are  added  just  the  amount 
of  proof  silver  determined  by  the  trial  assay  to  make  the  ratio  of  silver  to  gold  2  to  1. 
If  the  base  does  not  consist  of  copper  such  is  added  sufficient  to  make  the  total  10% 
of  the  gold  present.  One  or  more  check  portions  are  made  containing  the  same  amount 
of  gold,  silver  and  copper  as  are  in  the  assay  portions.  Each  of  the  check  and  assay 
portions  are  wrapped  with  exactly  10  grams  of  lead  and  cupelled  under  precisely  the 
same  conditions  at  a  temperature  somewhat  higher  than  will  produce  feather  litharge. 
If  the  bullion  contains  copper,  the  same  quantity  is  added  to  the  check  portions.  The 
quantity  of  lead  to  be  used  in  cupellation  depends  upon,  but  as  in  the  assay  of  silver 
copper  alloys  is  not  in  direct  ratio  to  the  quantity  of  copper  present.  The  object  is 
not  to  remove  all  the  copper  by  cupellation,  but  to  leave  just  so  much  as  will  toughen 
the  silver  gold  alloy.  Temperature  and  draft  are  factors  which  affect  the  elimination 
of  copper. 

Subject  to  modification  on  account  of  the  quantity  and  character  of  other  impurity, 
the  following  table  will  in  a  general  way  serve  as  a  guide  to  the  quantity  of  lead  to  use 
when  500  milligrams  of  gold  bullion  are  weighed  out. 


Copper  Present 
in  Milligrams. 

Lead  to  Use 
in  Grams. 

50 

10 

100 

16 

150 

22 

200 

24 

250 

26 

300 

28 

350 

30 

The  thoroughly  cleaned  buttons  are  rolled  to  the  same  thickness  and  length.  When 
cupelled  with  just  the  proper  amount  of  copper  and  lead  the  edges  will  not  crack. 
If  annealed  at  too  high  a  temperature  the  surface  will  blister  and  particles  are  likely 

1  See  Circular  No.  3,  U.  S.  Bureau  of  Standards. 


ASSAYING  FOR   GOLD   AND   SILVER  769 

to  fall  off  in  parting.  If  the  annealing  is  not  uniform  or  complete,  the  results  will  not 
agree  and  the  value  of  the  check  assays  is  vitiated.  The  cornets  at  this  point  may  be 
stamped  by  a  small  die  with  figures  or  dots  indicating  the  note-book  record  of  the  assay 
and  check  portions.  Each  cornet  is  then  coiled  into  a  roll  with  index  mark  outward 
and  placed  in  a  platinum  capsule  with  perforated  bottom  which  will  fit  the  cornets 
not  too  loosely  or  tightly.  The  capsules  set  in  a  platinum  tray  which  has  an  upright 
handle  and  rests  on  a  platinum  stand  about  1£  ins.  above  the  bottom  of  ja,  beaker. 

With  some  experience  in  soldering  platinum  with  gold  and  without  requirement 
of  much  skill,  boiling  apparatus  with  capacity  for  nine  tests  can  be  laboratory  made 
from  17  ins.  of  0.06-in.  wire,  nine  strips  13  by  31  mm.  each  of  unperforated  0.005-in. 
sheets,  nine  circular  pieces  10  mm.  in  diameter  and  one  circular  sheet  2  ins.  in  diameter 
of  0.005  sheet  platinum  perforated  with  0.062-in.  holes,  144  to  the  square  inch.  Each 
capsule  is  a  cylinder  10  mm.  in  diameter,  13  mm.  long,  closed  at  the  bottom  with 
perforated  metal.  To  the  center  of  the  bottom  is  soldered  a  £-in.  length  of  0.06-in. 
wire.  This  wire  through  a  perforation  holds  the  capsule  upright  as  it  rests  on  the  cir- 
cular sheet  which  is  soldered  to  a  2-in.  diameter  loop  in  the  wire;  the  wire  should  extend 
beyond  the  loop  1|  ins.  on  one  side  and  6  ins.  or  more  on  the  other.  The  sheet  in  the 
loop  is  bent  at  right  angle  to  the  wire  and  two  pieces  of  wire  each  1£  ins.  long  are  sol- 
dered to  the  loops  to  form  a  tripod.  The  wire  extending  above  the  frame  is  bent  to 
form  a  handle  over  the  side  of  a  beaker  and  out  of  direct  range  of  acid  fumes. 

Two  strengths  of  acids  are  used,  the  first  of  equal  parts  of  1.42  sp.gr.  nitric  acid  and 
water  the  second  of  2  parts  of  acid  to  1  of  water.  The  600-cc.  beaker,  half  filled  with 
No.  1  acid,  is  brought  to  boiling,  the  frame  with  capsules  is  slowly  introduced  to  avoid 
boiling  over,  and  allowed  to  remain  ten  to  fifteen  minutes.  The  frame  is  taken  out,  drained 
of  the  acid,  dipped  in  a  large  beaker  of  hot  water,  and  then  introduced  into  a  beaker 
half  filled  with  boiling  No.  2  acid.  After  fifteen  minutes'  boiling  the  frame  is  removed, 
dipped  successively  into  two  beakers  of  hot  water,  boiled  for  five  to  ten  minutes  in  a 
third,  dipped  in  the  fourth,  drained  and  dried  by  placing  in  an  oven  or  on  a  hot  plate. 
The  contents  of  each  capsule  are  removed  to  an  annealing  cup  or  porcelain  casserole, 
annealed  and  weighed  to  hundredths  milligrams.  The  actual  loss  or  gain  sustained 
by  the  check  portion  is  added  to  or  subtracted  from  the  assay  portions.  The  corrected 
results  are  calculated  to  parts  per  thousand  and  reported  as  fineness.  More  confidence 
is  placed  in  check  assays  which  show  a  loss  when  such  loss  is  known  to  be  not  mechanical. 

COMBINATION  METHODS 

Copper  Bullion.  The  sulphuric  acid  method  when  skillfully  carried  out  gives 
results  for  gold  in  blister  and  refined  copper  equal  to  those  by  the  "  all  fire,  "  and 
for  silver  the  same  as  the  nitric  acid  combination  method.  For  each  test  1  A.T. 
is  placed  in  a  1000-cc.  beaker  of  resistance  glass  and  shaken  with  5  cc.  of  a  solu- 
tion of  mercuric  nitrate  (mercuric  nitrate  solution  is  made  by  dissolving  10  grams  of 
mercury  with  the  least  quantity — about  25  cc. — of  hot  nitric  acid,  making  the  solu- 
tion up  to  1000  cc.  Just  sufficient  nitric  acid  is  added  to  keep  the  solution  clear). 
80  cc.  of  1.84  sp.gr.  sulphuric  acid  are  added.  Some  brands  of  blister,  especially 
such  as  contain  arsenic,  dissolve  best  when  20  or  more  cc.  of  water  are  also 
added  and  the  quantity  of  mercury  solution  is  increased.  The  beaker  cov- 
ered with  a  clock-glass  is  placed  on  a  very  hot  plate,  and  boiled  vigorously 
for  ten  minutes.  The  temperature  is  then  decreased  so  low  that  the  accu- 
mulation of  sulphur  on  the  sides  of  the  beaker  will  remain,  but  not  so 
low  as  to  stop  quite  copious  fuming  of  the  acid.  The  beaker  is  taken  off 
just  before  the  liquid  becomes  grayish  in  color.  This  point  is  determined 
by  expert  observation  of  the  appearance  of  the  hot  solution.  The  tempera- 
ture of  the  hot  plate,  size  of  the  particles  of  copper,  the  quantity  and  char- 
acter of  impurities  in  the  copper,  as  well  as  amount  of  sulphuric  acid  used  are 
factors  which  influence  the  time  required  for  solution.  The  time  will  vary  from 
thirty  to  ninety  minutes.  Since  the  gold  is  in  a  very  finely  divided  condition  and 


770  ASSAYING  FOR  GOLD   AND   SILVER 

a  little  copper  sulphide  acts  efficiently  as  an  entangling  agent,  no  attempt  should 
be  made  to  continue  the  treatment  with  sulphuric  acid  until  the  clear  liquid,  which 
will  result  from  low  silver-bearing  copper,  indicates  complete  solution  of  copper 
sulphide.  Silver  sulphide  is  also  effective  in  preventing  gold  from  passing  through 
the  filter,  and  in  the  assay  of  very  high  gold-bearing  copper  containing  little  silver, 
it  is  of  advantage  to  add  the  silver  required  to  carry  the  gold  with  minimum  loss 
through  cupellation  to  the  beaker  before  solution  rather  than  to  the  scorifier  or 
cupel.  After  the  beaker  has  become  cold  through  standing  on  an  asbestos  mat, 
a  little  standard  salt  solution  is  added  to  precipitate  the  trace  or  more  of  silver 
which  may  be  in  solution.  Although  only  a  trace  of  silver  may  be  dissolved  it  is 
safe  to  assume  that  2%  of  that  present  is  in  solution.  At  least  600  cc.  of  boiling 
hot  water  are  added  a  little  at  a  time  while  the  lumps  of  anhydrous  salt  are  being 
broken  up  by  a  stirring  rod.  The  liquid  is  filtered  hot  through  three  or  four  15- 
cm.  No.  1  F  Swedish  filter  paper  folded  together  in  a  funnel  (2f  to  2J  ins.  in  diam- 
eter) whose  brim  is  about  j  in.  below  the  edge  of  the  paper.  During  filtration 
copper  sulphate  must  not  be  allowed  to  stretch  the  pores  of  the  paper  by  crystal- 
lizing. Solution,  therefore,  should  be  maintained  by  addition  of  hot  water  to  the 
contents  of  the  funnel  as  required.  The  beaker  is  wiped  very  thoroughly  with  a 
piece  of  common  filter  paper.  The  inside  of  the  filter  is  sprinkled  with  15  grams 
test  lead.  The  filter  is  folded,  placed  in  a  2|-in.  scorifier  and  covered  with  15  grams 
more  lead.  The  filter  is  incinerated  in  an  oven  or  muffle.  After  adding  a  pinch 
(about  2  grams)  of  borax  or  borax  silica  flux,  scorification  is  continued  to  pro- 
duction of  10-  to  15-gram  button. 

The  nitric  acid  method  of  solution  of  blister  or  other  copper  is  resorted  to  when 
the  sample  is  in  such  coarse  form  that  the  sulphuric-acid  method  is  impracticable. 
The  results  for  gold  tend  to  be  lower  than  those  from  the  sulphuric-acid  method, 
partly  because  of  the  solvent  action  of  nitric  acid,  which  is  especially  noticeable 
when  the  copper  contains  selenium  and  partly  on  account  of  the  very  fine  state 
of  the  liberated  particles.  The  solvent  action  is  hindered  by  alloying  the  copper 
with  a  considerable  quantity  of  mercury  and  by  dissolving  with  weak  acid.  In  the 
assay  of  copper  in  coarse  form  some  heat  must  be  applied  or  stronger  acid  used  to 
complete  the  solution,  but  when  the  sample  is  fine  the  heat  of  the  reaction  is  suf- 
ficient. 

One  A.T.  in  a  covered  1000-cc.  beaker  is  shaken  with  5  cc.  of  a  solution  of  nitrate 
of  mercury  which  contains  1  gram  of  mercury,  400  cc.  (or  a  larger  amount  if  the 
sample  is  fine)  of  water  and  100  cc.  of  nitric  acid,  sp.gr.  1.42  are  added.  The  beaker 
is  allowed  to  stand  overnight,  and  in  the  morning  solution  is  completed  if  neces- 
sary by  heating  gently  on  a  hot  plate.  An  emulsion  of  lead  sulphate  is  poured 
in  with  constant  stirring  until  a  permanent  precipitate  forms.  Ten  cc.  of  thick 
paper  pulp  is  then  stirred  in  and  the  beaker  allowed  to  stand  for  an  hour  on  a 
plate  sufficiently  hot  to  promote  circulation  of  the  liquid.  Filtration  is  through 
two  15-cm.  papers  of  S.  &  S.  No.  590  quality.  The  beaker  is  wiped  thoroughly 
after  taking  care  to  transfer  to  the  filter  every  trace  of  the  mercury  flour  which 
sometimes  forms.  The  inside  of  the  paper  is  sprinkled  with  7\  grams  test  lead. 
The  paper  is  folded  and  placed  in  a  2^-in.  scorifier,  the  cup  of  which  has  been 
glazed  with  lead  silicate  or  borate;  7|  grams  of  lead  are  placed  on  the  paper,  which 
is  then  incinerated.  To  the  filtrate  with  constant  stirring  is  added  saturated  salt 
solution — a  few  drops  at  a  time — until  a  permanent  precipitate  remains.  The 
beaker  is  heated  nearly  to  boiling  and  more  salt  solution  added  in  the  same  way 
if  the  precipitate  first  formed  dissolves.  When  the  silver  has  become  granular 


L   lAVs 

ray 

5 


ASSAYING  FOR  GOLD   AND   SILVER  771 

digestion  on  the  hot  plate  is  stopped  and  the  liquid  cooled  to  room  temperature 
before  filtering  through  a  single  15-cm.  paper  of  No.  590  quality.  When  the 
quantity  of  silver  is  high  (200  milligrams  or  over),  the  copper  solution  is  filtered 
without  disturbing  the  precipitate.  The  precipitate  is  washed  quite  free  of  copper 
by  decantation.  7|  grams  of  lead  are  stirred  into  the  precipitate  and  allowed  to 
remain  until  the  appearance  indicates  that  all  the  silver  chloride  is  reduced. 
The  contents  of  the  beaker  are  then  transferred  to  the  filter.  The  beaker  and 
stirring  rod  are  thoroughly  wiped  with  filter  paper.  When  the  silver  tenor  of 
the  sample  is  low,  the  inside  of  the  paper  is  sprinkled  with  7|  grams  of  load.  The 
paper  is  folded,  placed  on  the  residue  of  the  paper  containing  the  product  of  the 
previous  filtration,  covered  with  1\  grams  of  lead  and  incinerated.  Scorification 
when  lead  sulphate  is  present  should  commence  at  rather  high  temperature. 

Copper  Matte.  The  following  combination  method  of  assaying  iron-copper 
matte  gives  results  for  gold  equal  to  that  from  any  of  the  all-fire  methods.  One 
A.T.  in  an  1000-cc.  beaker  is  gently  boiled  with  350  cc.  of  a  mixture  of  1  part 
concentrated  sulphuric  acid  and  10  parts  water.  Boiling  is  continued  until  but 
little  gas  is  given  off.  The  solution  is  then  filtered  through  a  single  15-cm.  paper 
and  the  residue  washed  with  hot  water  twice.  The  filtrate  is  discarded.  The 
filter  paper  and  its  contents  are  placed  in  the  beaker.  Twenty  cc.  of  a  solution  of 
mercuric  nitrate  containing  200  milligrams  of  mercury  are  poured  over  the  residue 
and  the  beaker  immediately  shaken  until  all  its  particles  are  wet  by  the  mercury. 
150  cc.  of  water  and  100  cc.  of  nitric  acid  are  added  and  the  beaker  allowed  to  stand 
for  at  least  half  an  hour.  The  liquid  is  then  boiled  until  no  fumes  are  given  off. 
The  solution  is  then  filtered  through  two  15-  cm.  filters  of  No.  589  quality  folded 
together.  The  beaker  is  wiped  thoroughly  with  filter  paper.  The  bulky  precipi- 
tate, sprinkled  with  20  grams  lead,  is  placed  in  a  3-in.  Bartlett-shaped  scorifier 
which  has  been  glazed  with  lead  silicate.  The  folded  paper  is  covered  with  20 
grams  lead,  incinerated,  fluxed  with  2  grams  of  borax  and  scorified  to  a  10-gram 
button  which  is  reserved  for  addition  to  the  scorifier  containing  the  silver  residue. 
Scorification  should  commence  at  a  high  temperature.  Silver  is  precipitated  as 
chloride  and  manipulated  in  the  same  manner  as  has  been  described  in  the  nitric 
acid  method  for  blister  and  refined  copper.  The  total  charge  of  lead  in  the  2|-in. 
scorifier  containing  the  silver  residue  after  addition  of  the  button  containing 
the  gold,  is  25  to  30  grams. 

On  account  of  slow  filtration,  slag  in  matte  interferes  with  the  operation  of 
this  method. 

The  following  method  of  treatment  of  matte  tends  to  give  higher  silver  but 
lower  gold  results.  To  1  A.T.  in  a  1000-cc.  beaker  are  added  cautiously  at  first 
100  cc.  strong  nitric  and  then  50  cc.  cone,  sulphuric  acid  with  beaker  covered, 
the  liquid  is  boiled  until  the  sample  is  completely  decomposed  and  the  precipi- 
tated sulphur  is  yellow.  When  the  liquid  is  cold,  the  salts  are  dissolved  with 
400  cc.  hot  water  and  the  solution  is  filtered  hot.  The  procedure  from  this  point 
is  the  same  as  described  in  the  nitric  acid  treatment  of  blister  copper. 

Silver  Slime  for  Gold  and  Silver.  Each  assay  portion  of  0.1  or  0.05  A.T.  is 
wet  in  a  1000-cc.  resistance-glass  beaker  with  10  cc.  of  a  solution  of  nitrate  of 
mercury  which  contains  10  milligrams  of  mercury.  Fifty  cc.  of  1.84  sp.gr.  sul- 
phuric acid  are  added  and  boiled  for  about  thirty  minutes.  When  cold,  400  cc.  of 
hot  water  are  added  and  after  all  salts  are  in  solution,  a  solution  of  sodium  chloride 
of  approximately  known  silver  precipitating  strength  is  dropped  in  with  constant 
stirring  until  it  is  evident  that  a  slight  excess  has  been  added.  The  liquid  is  stirred 


772  ASSAYING  FOR   GOLD   AND   SILVER 

until  silver  chloride  is  coagulated.  When  cold,  the  clear  liquid  is  decanted  through 
a  15-  cm.  No.  589  paper  without  disturbing  the  precipitate.  The  precipitate 
is  washed  free  of  copper  by  decantation.  Ten  grams  of  40-mesh  test  lead  are 
sprinkled  over  the  inside  of  the  filter.  Twenty  grams  of  test  lead  and  a  few  drops 
of  a  solution  of  sodium  sulphide  are  mixed  with  the  precipitate  of  silver  chloride 
with  a  stirring  rod.  When  it  is  apparent  that  reduction  of  silver  is  quite  complete 
the  residue  is  washed  into  the  filter  and  the  beaker  thoroughly  wiped  with  filter 
paper.  After  draining  the  filter  is  folded,  placed  in  a  3-in.  scorifier,  covered  with 
10  grams  of  lead,  dried  and  incinerated.  Fluxed  with  a  pinch  (2  to  3  grams) 
of  borax  glass,  scorification  is  continued  to  production  of  a  15-  to  20-gram  button. 
Corrected  assay  is  made  of  the  slag  and  cupel. 

Removal  of  Interfering  Metals.  Inasmuch  as  bismuth,  selenium  or  tellurium 
are  not  readily  removed  from  a  lead  button  by  dry  oxidation,  with  the  object  of 
avoiding  repeated  scorifications,  it  is  expedient  to  remove  these  elements  by  dis- 
solving the  well-cleaned  lead  button  with  twelve  times  as  many  cc.  as  its  weight  in 
grams  of  a  mixture  of  1  part  of  strong  nitric  acid  with  5  parts  water.  The  gold 
is  filtered,  the  silver  precipitated,  reduced  when  high,  filtered  and  the  filters  con- 
taining each  of  the  precious  metals  manipulated  as  has  been  described.  In  the 
treatment  of  a  bismuth-bearing  button,  the  filter  should  be  washed  with  acidu- 
lated water.  When  platinum  is  present  in  the  material  undergoing  assay  in 
quantity  sufficient  to  interfere  with  the  purity  of  the  silver  bead  produced  by 
cupellation  at  the  usual  temperature,  the  solution  of  the  lead  button  by  nitric 
acid  is  filtered  through  a  small  filter.  The  content  of  the  thoroughly  washed 
filter  is  treated  for  determination  of  platinum  and  gold  by  methods  described  in 
chapter  on  Platinum.  Silver  in  the  filtrate  is  precipitated  as  chloride  and 
determined  by  the  described  procedures  of  filtration,  scorification  and  cupellation. 
By  this  method  may  be  conducted  the  assay  for  silver  in  material  containing 
gold  in  excess  of  silver. 

When  the  precipitate  of  silver  chloride  is  colored  a  deep  pink,  indicating  the 
presence  of  considerable  palladium,  the  button  resulting  from  its  scorification  is 
dissolved,  silver  again  precipitated,  filtered,  scorified  and,  if  the  silver  chloride  is 
not  too  highly  colored,  cupelled.1 

Assay  of  Cobalt— Silver  Ore.2  i  or  |  A.T.  portions  are  taken,  the  former  when 
the  sample  carries  over  2000  oz.  silver  per  ton.  Nitric  acid  is  added  a  little  at  a 
time  to  the  pulp  in  a  covered  beaker,  about  75  cc.  for  a  £-A.T.  or  100  cc.  for  a 
£  A.T.  portion.  After  heating  on  a  steam  bath  until  action  has  ceased,  200  cc. 
water  are  added  and  the  solution  allowed  to  stand  (best  over  night)  until  cold 
before  filtration.  From  some  ores  containing  much  arsenic,  a  white  crystalline 
coating  containing  a  little  silver  forms,  and  unless  allowed  to  form  in  the  original 
nitric  acid  solution  will  cause  trouble  later.  If  the  coating  cannot  be  detached 
by  filter  paper  it  is  treated  in  the  beaker  with  a  hot  solution  of  sodium  hydrate. 
The  alkaline  liquid  is  acidulated  with  nitric  acid  and  washed  into  the  filter  with  the 
insoluble  residue.  If  the  insoluble  residue  is  large  in  volume,  it  is  dried,  burned 
in  a  crucible  and  fused  with  litharge,  borax,  sodium  carbonate  and  a  reducing 
agent.  If  the  residue  is  small,  it  is  scorified.  In  either  case  the  lead  button  from 
the  residue  is  reserved. 

Standard  sodium  chloride  solution  is  added  to  the  filtrate  from  the  insoluble 
residue  in  quantity  sufficient  to  precipitate  all  the  silver,  but  carefully  avoiding 

1  See  article  by  A.  M.  Smoot,  End.  and  Min.  Jour.,  April  17,  1915,  p.  701. 
2Smoot,  Eng.  and  Min.  J.,  28,  1100,  1914. 


ASSAYING  FOR  GOLD   AND  SILVER  773 

any  considerable  excess.  The  precipitate  is  stirred  briskly  until  it  coagulates 
and  then  is  allowed  to  stand  for  an  hour  until  the  supernatant  liquid  becomes 
clear.  The  precipitate  is  transferred  to  a  double  filter  and  washed  slightly  with 
water.  Traces  of  silver  chloride  in  the  beaker  are  wiped  off  with  filter  paper  and 
placed  in  the  filter.  The  filter  is  transferred  to  a  scorifier  which  has  been  glazed 
with  molten  litharge.  As  a  further  precaution  against  absorbing  moisture,  a 
small  disk  of  lead  is  placed  under  the  paper.  The  paper  in  the  scorifier  is  dried 
and  burned  in  a  closed  oven  at  250  to  300°  C.  Fine  test  lead  is  sprinkled  over  the 
residue  and  the  button  resulting  from  the  crucible  or  scorifier  fusion  of  the  in- 
soluble residue  is  added.  Scorification  at  a  low  temperature  is  conducted  to 
production  of  a  15-gram  button  which  is  cupelled  with  care  to  avoid  "  sprouting." 
The  influence  of  bismuth  which  cobalt  ores  sometimes  contain  is  eliminated  by 
the  combination  method. 

CYANIDE  SOLUTIONS 

Inasmuch  as  cyanide  solutions  have  but  little  greater  gravity  than  water, 
29.2  cc.  is  regarded  as  the  volume  equivalent  of  1  A.T.  The  quantity  taken  for 
assay  depends  upon  the  gold  or  silver  content;  1  A.T.  of  a  rich  solution,  50  to  100 
A.T.  when  traces  of  the  metals  are  sought;  5,  10  or  10  A.T.  are  the  test  portions 
most  commonly  employed.  When  gold  only  is  to  be  determined,  there  should 
be  in  the  lead  button  prepared  for  cupellation  sufficient  silver  to  permit  parting 
of  the  bead  resulting  from  the  operation.  Silver  may  be  added  to  the  button 
or  solution  in  the  form  of  metal  or  to  the  solution  in  the  form  of  a  standard  solution 
of  silver  nitrate  if  the  electrolytic  or  evaporation  method  is  employed. 

The  methods  of  preparation  of  the  solution  for  fire  assay  may  be  grouped  as 
follows : 

(a)  Evaporation.1 

(6)  Metallic  Reagent.2  Aluminum  foil,3  cement  copper,3  zinc  dust,  zinc  lead 
couple  formed  by  the  addition  of  lead  acetate  to  the  cyanide  solution  and  precipita- 
tion of  spongy  lead  by  zinc  shavings,4  by  zinc  dust,5  by  stick  zinc,6  aluminum-lead 
couple.7 

(c)  Electrolytic.9 

(d)  Liquid  reagent ,  potassium  ferrocyanide  and  cuprous  chloride,9  copper  sulphate 
and  sodium  sulphite,10  ferrous  sulphate,  oxalic  acid. 

(3)  Gaseous  reagent,  hydrogen  sulphide.11 

The  evaporation  method  is  the  standard  with  which  all  other  methods  are 
compared,  and  on  account  of  the  requirement  of  little  manipulation,  is  practiced 

1  All  Manuals  or  Text  Books  of  Assaying. 

2  Seamon,  West.  Chem.  and  Met.,  Aug.,  1909,  291. 
3Arents,  Trans.  A.I.M.E.,  34,  184. 

4  Chiddy,  Eng.  and  Min.  J.,  Mar.  28,  1903,  473. 

5  Magenau,  Min.  and  Sci.  Press,  Apr.  14,  1906,  259;    Stines,   Min.  and  Sci.   Press, 
Apr.  28,  1906,  278;    Durant,  Proc.  Chem.  Met.  and  Min.  Soc.  of  S.A.,  1902-3,  105; 
Clark,  Fulton's  "  Manual  of  Fire  Assaying,"  2d  ed.  156. 

6  Bahney,  Trans,  A.I.M.E.,  51,  131. 

7  Holt,  Min.  and  Sci.  Press,  June  11,  1910,  863. 

8  Miller,  J.  Chem.  Met.  and  Min.  Soc.  of  S.  A.,  Feb.  15,  1905,  216;    Crichton,  J. 
Chem.  Met.  and  Min.  Soc.  of  S.  A.,  1911-12,  90. 

9  White,  J.  Chem.  Met.  and  Min.  Soc.  of  S.  A.,  Oct.,  1909,  136. 

10  Whitby,  Proc.  Chem.  Met.  and  Min.  Soc.  of  S.  A.,  1902-3,  15. 

11  Watson,  Eng.  and  Min.  J.,  Mar.  28,  1911,  443. 


774  ASSAYING  FOR  GOLD   AND   SILVER 

with  considerable  variety  of  detail  in  laboratories  which  make  a  large  number 
of  assays.  From  a  6-  by  4-in.  strip  of  assayers'  sheet  lead,  a  flat-bottom  dish 
4  by  2  by  1  in.  deep  can  be  made,  which  will  weigh  30  to  40  grams  and  hold  3  A.T. 
A  test  portion  of  this  or  a  larger  amount  of  cyanide  solution  introduced  from  time 
to  time  is  evaporated  to  dryness.  To  avoid  spattering  the  heat  of  the  hot  plate  is 
reduced  toward  the  last  of  the  operation.  The  dish  is  folded  carefully  and  scori- 
fied to  a  15-  to  20-gram  button  in  a  3-in.  scorifier.  A  10  or  20  A.T.  test  portion 
may  be  evaporated  to  small  volume  in  an  evaporating  dish  or  casserole,  and  then 
to  dryness  in  a  lead  dish.  When  it  is  the  practice  to  complete  the  evaporation 
in  porcelain  or  earthen  ware,  50  to  60  grams  of  litharge  are  added  with  the  object 
of  facilitating  removal  of  the  residue.  The  residue,  which  should  not  be  heated 
so  strongly  as  to  make  a  hard  cake,  is  removed  with  a  spatula  and  intimately  mixed 
with  a  charge  l  consisting  of  25  grams  litharge,  15  grams  sodium  carbonate, 
2  grams  fine  silica,  5  grams  borax  glass  and  2  grams  argol.  Fusion  is  made  in  a 
20-gram  crucible.  When  the  scorification  method  of  fusion  is  preferred,  10  grams 
of  granulated  lead  are  added  to  the  solution  instead  of  litharge,  the  residue  trans- 
ferred to  a  2-in.  scorifier,  covered  with  15  grams  test  lead  and  a  pinch  of  borax 
glass  and  scorified  to  a  15-  to  20-gram  button.  Whether  litharge  or  lead  is  used, 
the  dish  should  be  wiped  thoroughly  with  moist  filter  paper  which  is  placed  in  the 
bottom  of  the  crucible  or  retained  in  place  in  the  scorifier  by  the  15  grams  of  test 
lead. 

Of  the  metallic  reagent  methods,  the  zinc-lead  couple  is  most  commonly 
practiced.  The  details  of  manipulation  vary  with  different  operators.  The  fol- 
lowing method  combines  the  features  of  Clark's  2  and  Bahney's.3  To  the  test 
portion  of  cyanide  solution  in  a  beaker  of  capacity  several  hundred  cc.  in  excess 
of  its  liquid  content,  are  added  25  cc.  of  a  20%  solution  of  lead  acetate.  From  a 
bottle  having  a  |-in.  glass  tube  through  the  stopper  and  holding  silver-free  zinc 
dust  and  water  in  the  proportion  of  1  gram  in  3  cc.,  the  equivalent  of  4  grams  of 
dust  is  shaken  out  into  a  suitable  graduate  and  added  to  the  cyanide  liquor. 
When  moderately  heated,  but  before  boiling,  a  volume  of  1.18  to  1.19  S.G.  C.P. 
hydrochloric  acid  equal  to  10%  of  the  cyanide  solution  is  added.  The  mixture 
is  then  boiled  not  too  vigorously  until  the  spongy  lead  aggregates  (five  to  ten 
minutes). 

Since  some  zinc  may  remain  undissolved  in  the  mass  above  the  surface  of  the 
liquid,  after  removal  of  the  beaker  from  the  hot  plate,  the  precipitate  is  collected 
and  confined  below  the  surface  by  an  overturned  funnel  which  has  a  diameter 
1  in.  less  than  the  diameter  of  the  beaker  and  whose  constricted  throat  is  sealed 
with  a  small  ball  of  barren  lead  sponge.  After  standing  hot  for  five  to  ten  minutes 
the  funnel  is  removed  and  washed  free  of  adherent  particles.  The  beaker  is  then 
filled  up  with  cold  water.  From  a  circular  piece  of  assayers'  sheet  lead  3  ins.  in 
diameter  and  weighing  7  to  9  grams  a  filter  cone  is  made  by  pricking  a  dozen  fine 
holes  through  and  about  the  apex.  This  cone  is  fitted  to  a  2-in.  funnel  in  a  filter 
flask  which  is  connected  to  aspirating  apparatus.  A  layer  of  5  grams  of  test  lead, 
finer  than  60  mesh,  is  shaped  over  the  perforated  portion  of  the  cone.  The  clear 
liquid  is  decanted  as  completely  as  is  practicable  without  loss  of  precipitate.  The 
beaker  is  again  filled  with  cold  water  and  decanted.  A  portion  of  the  sponge  is 
drawn  with  the  flattened  end  of  a  glass  rod  onto  the  filter  cone  and  tamped  into 

1  Fulton,  "Manual  of  Fire  Assaying,"  2d  ed.,  157. 
'Fulton's  "Manual  of  Fire  Assaying,"  2d  ed,  156. 
»  Trans.  A.I.M.E.,  51,  129. 


ASSAYING  FOR  GOLD  AND  SILVER  775 

place.  After  complete  removal  of  the  precipitate  to  the  cone,  it  is  washed  several 
times  and  then  dewatered  by  tamping  with  the  rod.  The  edges  of  the  filter  cone  are 
folded  tightly  over  the  precipitate  to  form  a  cone-shaped  button  which  will  fit 
a  1^-in.  cupel.  The  button  is  placed  in  a  hot  cupel  which  is  brought  to  the  front 
of  the  muffle  and  allowed  to  remain  there  no  longer  than  is  sufficient  to  expel 
moisture.  A  piece  of  glowing  charcoal  placed  in  front  of  the  cupel  will  help  to 
clear  the  lead  shortly  after  the  muffle  door  is  closed,  if  the  muffle  has  been  kept 
at  the  temperature  which  prevails  in  the  usual  practice  of  starting  cupellation. 

If  suspended  matter  insoluble  in  hydrochloric  acid  or  considerable  copper  is 
present  in  the  solution,  cupellation  without  previous  scorification  is  impracticable, 
the  other  details  of  the  method,  however,  may  be  carried  out  as  described.  In 
such  cases  the  lead  button  is  placed  in  a  2-in.  scorifier,  10  grams  of  test  lead  and 
borax  flux  are  added  and  scorification  continued  to  production  of  a  10-  to  15-gram 
button.  In  case  much  copper  is  present,  it  may  be  necessary  to  rescorify  with 
addition  of  more  lead. 

By  the  electrolytic  method,1  gold  is  deposited  on  a  cylinder  of  assay  lead  foil 
which  fits  closely  the  inside  and  rests  on  the  bottom  of  the  beaker.  The  lower 
edge  of  the  foil  is  serrated  to  promote  circulation.  The  anode  is  a  i^-in.  carbon 
rod.  The  current  is  adjusted  to  the  KCN  strength  of  the  solution;  0.1  amp. 
for  a  0.3%  to  0.04  amp.  for  a  0.02%  solution.  To  avoid  plating  out  on  the  anode, 
care  is  taken  to  have  the  current  on  all  the  time  it  is  in  contact  with  the  solution. 
A  little  cyanide  added  to  a  weak  solution  facilitates  the  deposition  of  gold; 
and  ammonium  hydrate  is  added  when  the  solution  is  impure.  When  deposition 
is  complete  (four  hours),  the  lead  foil  is  washed,  dried,  folded  into  a  button  and 
cupelled. 

Christy's  liquid  reagent  method,  as  modified  by  Whitby  and  described  by 
Clennell,2  is  based  on  the  fact  that  when  a  copper  salt  together  with  a  reducing 
agent  is  added  to  an  acidulated  cyanide  solution,  a  precipitate  of  cuprous  cyanide  is 
formed  which  precipitates  silver  and  all  but  a  trace  of  gold.  To  10  A.T.  are  stirred 
in  successively  20  cc.  10%  solution  of  blue  vitriol,  20  cc.  15%  solution  of  sodium 
sulphite  and  10  cc.  10%  sulphuric  acid.  Addition  of  a  little  ferrocyanide  of  potas- 
sium hastens  settling.  The  mixture  is  stirred  thoroughly,  allowed  to  settle  for 
fifteen  minutes,  filtered  and  the  filtrate  refiltered  until  clear.  When  drained 
the  precipitate  is  covered  with  a  mixture  of  30  grams  litharge,  30  grams  borax 
glass  and  1  gram  charcoal.  The  paper  and  contents  are  placed  in  a  hot  E  or  F 
crucible  and  the  operations  of  fusion  and  cupellation  carried  out. 

1  Crichton,  J.  Chem.  Met.  and  Min.  Soc.  of  S.  A.,  1911-12,  90. 

2  Cyanide  Hand  Book,  443, 


PART  III 
TABLES  AND   USEFUL  DATA 


TABLES  AND   USEFUL  DATA 


I.— INTERNATIONAL  ATOMIC   WEIGHTS,    1917 


1 
. 

Symbol. 

Atomic 
Weight. 

Symbol 

Atomic 
Weight. 

Aluminum  

Al 

27  1 

Neodymium   

Nd 

144  3 

Antimony 

Sb 

120  2 

Neon 

Ne 

20  2 

Argon  

A 

39.88 

Nickel  

Ni 

58.68 

Arsenic  

As 

74  96 

Niton  (radium  em- 

Barium 

Ba 

137  37 

anation) 

Nt 

222  4 

Bismuth  

Bi 

208.0 

Nitrogen    

N 

14.01 

Boron 

B 

11  0 

Osmium.       ....... 

Os 

190  9 

Bromine 

Br 

79  92 

Oxygen 

o 

16  00 

Cadmium       

Cd 

112.40 

Palladium  

Pd 

106  7 

Caesium 

Cs 

132  81 

Phosphorus  

P 

31  04 

Calcium  

Ca 

40.07 

Platinum  

Pt 

195.2 

Carbon.         

c 

12.005 

Potassium  

K 

39  10 

Cerium 

Ce 

140  25 

Praseodymium.  .  .  . 

Pr 

140  9 

Chlorine 

Cl 

35  46 

Radium 

Ra 

226  0 

Chromium. 

Cr 

52.0 

Rhodium  

Rh 

102  9 

Cobalt 

Co 

58  97 

Rubidium       .  .  . 

Rb 

85  45 

Columbium. 

Cb 

93.1 

Ruthenium  

Ru 

101.7 

Copper 

Cu 

63  57 

Samarium    

Sa 

150  4 

Dysprosium 

Dv 

162  5 

Scandium 

Sc 

44  1 

Erbium 

Er 

167  7 

Selenium   

Se 

79.2 

Europium 

Eu 

152  0 

Silicon 

Si 

28  3 

Fluorine. 

F 

19.0 

Silver  

Ag 

107.88 

Gadolinium 

Gd 

157  3 

Sodium 

Na 

23  00 

Gallium  

Ga 

69.9 

Strontium  

Sr 

87.63 

Germanium 

Ge 

72  5 

Sulphur       

s 

32  06 

Glucinum  

Gl 

9.1 

Tantalum  

Ta 

181.5 

Gold  

Au 

197.2 

Tellurium  

Te 

127.5 

Helium 

He 

4  00 

Terbium         

Tb 

159  2 

Holmium 

Ho 

163  5 

Thallium 

Tl 

204  0 

Hydrogen 

H 

1.008 

Thorium  

Th 

232.4 

Indium 

In 

114  8 

Thulium     

Tm 

168  5 

Iodine 

I 

126  92 

Tin 

Sn 

118  7 

Iridium 

Ir 

193.1 

Titanium  

Ti 

48.1 

Iron 

Fe 

55  84 

Tungsten  

W 

184  0 

Krypton 

Kr 

82  92 

Uranium 

u 

238  2 

Lanthanum  . 

La 

139.0 

Vanadium  

V 

51.0 

Lead 

Pb 

207  20 

Xenon       

Xe 

130  2 

Lithium.       

Li 

6.94 

Ytterbium   (Neoyt- 

Lutecium. 

Lu 

175  0 

terbium)  

Yb 

173.5 

Magnesium 

Me; 

24  32 

Yttrium  

Yt 

88.7 

Manganese 

Mn 

54  93 

Zinc 

Zn 

65.37 

Mercury 

Hg 

200  6 

Zirconium  ,  ,  

Zr 

90.6 

Molybdenum  

Mo 

96.0 

779 


780 


TABLES   AND   USEFUL   DATA 


II.— MELTING-POINTS  OF  THE  CHEMICAL  ELEMENTS  > 

Reproduced    from    Circular    No.    35    (2d    edition)    of    U.    S.  Bureau    of 
Standards. 

Element. 
Helium 
Hydrogen 
Neon 
Fluorine 
Oxygen 
Nitrogen 
Argon 
Krypton 
Xenon 
Chlorine 
Mercury 
Bromine 
Caesium 
Gallium 
Rubidium 
Phosphorus 
Potassium 
Sodium 
Iodine 

Sulphur 

Indium 

Lithium 

Selenium 

TIN 

Bismuth 

Thallium 

CADMIUM 

LEAD 

ZINC 

Tellurium 

ANTIMONY 

Cerium 

Magnesium 

ALUMINUM 

Radium 

Calcium 

Lanthanum 

Strontium 

III.  OTHER  TEMPERATURE  STANDARDS 

Temperatures  of  Flames.2 

Cent.       Deg.  of  Accuracy. 

Bunsen,  open 1870  Within  100°  C. 

Bunsen,  half  open 1810  Within  100°  C. 

Bunsen,  shut 1710  Within  100°  C. 

Acetylene 2550  Within  100°  C. 

Oxyhydrogen  with  illuminating  gas 2200  Within  100°  C. 

Oxyhydrogen  with  H2+0 2420  Within  100°  C. 

Electric  arc 3500  Within  150°  C. 

Sun..  .  6000  Within  500°  C. 


C. 

F. 

Element. 

C. 

F. 

<-271 

<-456 

Neodymium 

840? 

1544 

-259 

-434 

Arsenic 

850? 

1562 

-253? 

-423 

Barium 

850 

1562 

-223 

-369 

Praseodymium             940? 

1724 

-218 

-360 

Germanium 

958 

1756 

-210 

-346 

SILVER 

960.5 

1761 

-188 

-306 

GOLD 

1063.0 

1945.5 

-169 

-272 

COPPER 

1083.0 

1981.5 

-140 

-220 

Manganese 

1260 

2300 

-101.5 

-150.7 

Samarium 

1300-1400 

2370-2550 

-  38.9 

-38.0 

Beryllium 

-     7.3 

-f-18.9 

(glucinum) 

1350? 

2462 

+  26 

79 

Scandium 

? 

30 

86 

Silicon 

1420 

2588 

38 

100 

NICKEL 

1452 

2646 

44 

111.2 

Cobalt 

1480 

2696 

62.3 

144 

Yttrium 

1490 

2714 

97.5 

207.5 

Chromium 

1520 

2768 

113.5 

236.3 

IRON 

1530 

2786 

fS,    112.8 

235.0 

PALLADIUM 

1549 

2820 

Jsn   H9.2 

246.6 

Zirconium 

1700? 

3090 

ISni  106.8 

224.2 

Columbium 

155 

311 

(Niobium) 

1700? 

3090 

186 
217-220 

367 

422-428 

Thorium 

f>1700 
\<Pt 

>3090 
<Pt 

231.9 

449.4 

Vanadium 

1720 

3128 

271 

520 

PLATINUM 

1755 

3191 

302 

576 

Ytterbium 

? 

320.9 

609.6 

Titanium 

1800 

3272 

327.4 

621.3 

Uranium 

<1850 

<3362 

419.4 

786.9 

Rhodium 

1950 

3542 

452 

846 

Boron 

2200-2500?  4000-4500 

630.0 

1166 

Iridium 

2350? 

4262 

640 

1184 

Ruthenium 

2450? 

4442 

651 

1204 

Molybdenum 

2500? 

4500 

658.7 

1217.7 

Osmium 

2700? 

4900 

700 

1292 

Tantalum 

2850 

5160 

810 

1490 

TUNGSTEN 

3000 

5430 

810? 
>Ca<Ba? 

1490 

Carbon          < 

>3600    f 
for  p.  =  1  at.  \ 

>6500 
for  p.  =  1  at. 

1  Metallurgical  and  Chemical  Engineering,  Vol.  XIII,  No.  5,  May,  1915. 

2  Measurement  of  High  Temperatures,  G.  K.  Burgess  and  H.  Le  Chatelier. 


TABLES  AND   USEFUL   DATA 


781 


III.— OTHER   TEMPERATURE  STANDARDS  (Continued) 

Approximate  Temperatures  by  Colors. 

Cent.  Fahr. 

First  visible  red 525  977 

Dull  red 700  1292 

Cherry  red 900  1652 

Dull  orange 1100  2012 

White 1300  2372 

Dazzling  white 1500  2732 


Substance. 

Phenomenon. 

C. 

F. 

Variation  with  pressure 
(pressure  in  mm.  of  Hg.) 

Oxvcren 

Boiling  

-183  0 

-297  4 

C    °  —  183  0+0  01258  (p    760) 

Carbon  dioxide.  . 

Sodium  sulphate 
Na2SO4+10H2C 

Water  

Sublimation  in 
inert  liquid  .  . 
Transforma- 
tion into  an- 
hydrous salt  . 
Boiling  

-  78.5 
32.384 

100 

-109.3 
90.291 

212 

-0.0000079  (p.  760) 
C.  °  =  -78.5+0.017  (p.  760) 

C.  °  —  100+0.03670  (p.  760) 

N  aphthalene 

Boiling 

217  96 

423  73 

-0.00002046  (p.  760) 
C   °  =  217  96+0  058  (p  760) 

Benzophenone 

Boiling 

305  9 

582  6 

C.  °—  3059+0063  (p  760) 

Sulphur   

Boiling 

444  6 

832  3 

C.  °  =  444  6  +00908  (p  760) 

AgsCua 
Sodium  chloride  . 

Eutectic 
Freezing  
Freezing  

779 

801 

1434 
1472 

-0.000047  (p.  760) 

IV.— ELECTROMOTIVE  ARRANGEMENT  OF  THE  ELEMENTS 

Each  element  is  positive  to  the  element  placed  after  it  and  negative  to  the  element 
placed  above. 


1.  Cs 

2.  Rb 

3.  K 

4.  Na 

5.  Li 

6.  Ba 

7.  Sr 

8.  Ca 

9.  Mg 

10.  Be 

11.  Yt 

12.  Er 

13.  Sc 


14.  Al 

15.  Zr 

16.  Th 

17.  Ce 

18.  Di 

19.  La 

20.  Mn 

21.  Zn 

22.  Fe 

23.  Ni 

24.  Co 

25.  Cd 

26.  Pb 


27.  Ge 

28.  In 

29.  Ga 

30.  Bi 

31.  U 

32.  Cu 

33.  Ag 

34.  Hg 

35.  Pd 

36.  Ru 

37.  Rh 

38.  Pt 

39.  Ir 


40.  Os 

41.  Au 

42.  H 

43.  Sn 

44.  Si 

45.  Ti 

46.  Cb 

47.  Ta 

48.  Te 

49.  Sb 

50.  C 

61.  Bo 

62.  W 


53.  Mo 

54.  V 

55.  Cr 

56.  As 

57.  P 

58.  Se 

59.  I 

60.  Br 

61.  Cl 

62.  F 

63.  N 

64.  S 

65.  O 


782 


TABLES  AND  USEFUL  DATA 


ACID  AND  ALKALI  TABLES 

V.— HYDROCHLORIC  ACID 
BY  W.  C.  FERGUSON 


Degrees 

Baume. 

Sp.  Gr. 

Degrees 
Twaddell. 

Per  Cent 
HC1. 

Degrees 
Baume. 

Sp.  Gr. 

Degrees 
Twaddell. 

Per  Cent 
HC1. 

1.00 

1.0069 

1.38 

1.40 

14.25 

1.1090 

21.80 

21.68 

2.00 

1.0140 

2.80 

2.82 

14.50 

.1111 

22.22 

22.09 

3.00 

1.0211 

4.22 

4.25 

14.75 

.1132 

22.64 

22.50 

4.00 

1.0284 

5.68 

5.69 

15.00 

.1154 

23.08 

22.92 

5.00 

1.0357 

7.14 

7.15 

15.25 

.1176 

23.52 

23.33 

5.25 

1.0375 

7.50 

7.52 

15.50 

.1197 

23.94 

23.75 

5.50 

1.0394 

7.88 

7.89 

15.75 

.1219 

24.38 

24.16 

5.75 

1.0413 

8.26 

8.26 

16.0 

.1240 

24.80 

24.57 

6.00 

1.0432 

8.64 

8.64 

16.1 

1.1248 

24.96 

24.73 

6.25 

1  .0450 

9.00 

9.02 

16.2 

1.1256 

25.12 

24.90 

6.50 

1.0469 

9.38 

9.40 

16.3 

1.1265 

25.30 

25.06 

6.75 

1.0488 

9.76 

9.78 

16.4 

1.1274 

25.48 

25.23 

7.00 

1.0507 

10.14 

10.17 

16.5 

1.1283 

25.66 

25.39 

7.25 

1.0526 

10.52 

10.55 

16.6 

1.1292 

25.84 

25.56 

7.50 

1.0545 

10.90 

10.94 

16.7 

1.1301 

26.02 

25.72 

7.75 

1.0564 

11.28 

11.32 

16.8 

1.1310 

26.20 

25.89 

8.00 

1.0584 

11.68 

11.71 

16.9 

1.1319 

26.38 

26.05 

8.25 

1.0603 

12.06 

12.09 

17.0 

1.1328 

26.56 

26.22 

8.50 

1.0623 

12.46 

12.48 

17.1 

1.1336 

26.72 

26.39 

8.75 

1.0642 

12.84 

12.87 

17.2 

1.1345 

26.90 

26.56 

9.00 

1.0662 

13.24 

13.26 

17.3 

1.1354 

27.08 

26.73 

9.25 

1.0681 

13.62 

13.65 

17.4 

1.1363 

27.26 

26.90 

9.50 

1.0701 

14.02 

14.04 

17.5 

1.1372 

27.44 

27.07 

9.75 

1.0721 

14.42 

14.43 

17.6 

1.1381 

27.62 

27.24 

10.00 

1.0741 

14.82 

14.83 

17.7 

1.1390 

27.80 

27.41 

10.25 

1.0761 

15.22 

15.22 

17.8 

1.1399 

27.98 

27.58 

10.50 

1.0781 

15.62 

15.62 

17.9 

1.1408 

28.16 

27.75 

10.75 

1.0801 

16.02 

16.01 

18.0 

1.1417 

28.34 

27.92 

11.00 

1.0821 

16.42 

16.41 

18.1 

1.1426 

28.52 

28.09 

11.25 

1.0841 

16.82 

16.81 

18.2 

1.1435 

28.70 

28.26 

11.50 

1.0861 

17.22 

17.21 

18.3 

1  .  1444 

28.88 

28.44 

11.75 

1.0881 

17.62 

17.61 

18.4 

1.1453 

29.06 

28.61 

12.00 

1.0902 

18.04 

18.01 

18.5 

1.1462 

29.24 

28.78 

12.25 

1.0922 

18.44 

18.41 

18.6 

1.1471 

29.42 

28.95 

12.50 

1.0943 

18.86 

18.82 

18.7 

1.1480 

29.60 

29.13 

12.75 

1.0964 

19.28 

19.22 

18.8 

1.1489 

29.78 

29.30 

13.00 

1.0985 

19.70 

19.63 

18.9 

1.1498 

29.96 

29.48 

13.25 

1.1006 

20.12 

20.04 

19.0 

1.1508 

30.16 

29.65 

13.50 

1.1027 

20.54 

20.45 

19.1 

1.1517 

30.34 

29.83 

13.75 

1.1048 

20.96 

20.86 

19.2 

1.1526 

30.52 

30.00 

14.00 

1.1069 

21.38 

21.27 

19.3 

1.1535 

30.70 

30.18 

TABLES   AND   USEFUL   DATA 
V— HYDROCHLORIC   ACID    (Continued) 


783 


Degrees 
Baume. 

Sp.  Gr. 

Degrees 
Twaddell. 

Per  Cent 
HC1. 

Degrees 
Baume. 

Sp.  Gr. 

Degrees 
Twaddell. 

Per  Cent 
HC1. 

19.4 

1.1544 

30.88 

30.35 

22.5 

1  .  2  836 

36.72 

36.16- 

19.5 

1.1554 

31.08 

30.53 

22.6 

1.1846 

36.92 

36.35 

19.6 

1.1563 

31.26 

30.71 

22.7 

1.1856 

37.12 

36.54 

19.7 

1.1572 

31.44 

30.90 

22.8 

1.1866 

37.32 

36.73 

19.8 

1.1581 

31.62 

31.08 

22.9 

1.1875 

37.50 

36.93 

19.9 

1.1590 

31.80 

31.27 

23.0 

1.1885 

37.70 

37.14 

20.0 

1.1600 

32.00 

31.45 

23.1 

1.1895 

37.90 

37.36 

20.1 

1.1609 

32.18 

31.64 

23.2 

1.1904 

38.08 

37.58 

20.2 

1.1619 

32.38 

31.82 

23.3 

1.1914 

38.28 

37.80 

20.3 

1.1628 

32.56 

32.01 

23.4 

1.1924 

38.48 

38.03 

20.4 

1.1637 

32.74 

32.19 

23.5 

1.1934 

38.68 

38.26 

20.5 

1.1647 

32.94 

32.38 

23.6 

1.1944 

38.88 

38.49 

20.6 

1.1656 

33.12 

32.56 

23.7 

1.1953 

39.06 

38.72 

20.7 

1.1666 

33.32 

32.75 

23.8 

1.1963 

39.26 

38.95 

20.8 

1.1675 

33.50 

32.93 

23.9 

1.1973 

39.46 

39.18 

20.9 

1.1684 

33.68 

33.12 

24.0 

1.1983 

39.66 

39.41 

21.0 

1.1694 

33.88 

33.31 

24.1 

1.1993 

39.86 

39.64 

21.1 

1.1703 

34.06 

33.50 

24.2 

1.2003 

40.06 

39.86 

21.2 

1.1713 

34.26 

33.69 

24.3 

1.2013 

40.26 

40.09 

21.3 

1.1722 

34.44 

33.88 

24.4 

1.2023 

40.46 

40.32 

21.4 

1.1732 

34.64 

34.07 

24.5 

1.2033 

40.66 

40.55 

21.5 

1.1741 

34.82 

34.26 

24.6 

1.2043 

40.86 

40.78 

21.6 

1.1751 

35.02 

34.45 

24.7 

1.2053 

41.06 

41.01 

21.7 

1.1760 

35.20 

34.64 

24.8 

1.2063 

41.26 

41.24 

21.8 

1.1770 

35.40 

34.83 

24.9 

1.2073 

41.46 

41.48 

21.9 

1.1779 

35.58 

35.02 

25.0 

1.2083 

41.66 

41.72 

22.0 

1.1789 

35.78 

35.21 

25.1 

1.2093 

41.86 

41.99 

22.1 

1.1798 

35.96 

35.40 

25.2 

1.2103 

42.06 

42.30 

22.2 

1.1808 

36.16 

35.59 

25.3 

1.2114 

42.28 

42.64 

22.3 

1.1817 

36.34 

35.78 

25.4 

1.2124 

42.48 

43.01 

22.4 

1.1827 

36.54 

35.97 

25.5 

1.2134 

42.68 

43.40 

Sp.  Gr.  determinations  were  made  at  60°  F.,  compared  with  water  at  60°  F. 
From  the  Specific  Gravities,  the  corresponding  degrees  Baume"  were  calcu- 
lated by  the  following  formula:  Baum6  =  145  -  145/Sp.  Gr. 
Atomic  weights  from  F.  W.  Clarke's  table  of  1901.     O  =  16. 

ALLOWANCE  FOR  TEMPERATURE: 
10-15°  Be\     -     1/40°  B<§.  or  .0002  Sp.   Gr.  for  1°  F. 
15-22°  Be".     -     1/30°  Be*,  or  .0003    "       "    "    1°  F. 
22- 25°  Be".     -     1/28°  Be",  or  .00035  "       "    "    1°  F. 

AUTHORITY  —  W.  C.  FERGUSON. 

This  table  has  been  approved  and  adopted  as  a  Standard  by  the  Manu- 
facturing Chemists'  Association  of  the  United  States. 

W.  H.  BOWER,  JAS.  L.  MORGAN, 

HENRY  HOWARD,        ARTHUR  WYMAN, 

A.   G.   ROSENGARTEN, 

New  York,  May  14,  1903.  Executive  Committee 


784 


TABLES   AND   USEFUL   DATA 


VI.— HYDROCHLORIC   ACID 
LUNGE  AND  MARCHLEWSKI 


Specific 

i  Liter 

Specific 

i  Liter 

Specific 

i  Liter 

Gravity. 

Per  Cent 

con- 

Gravity 

Per  Cent 

con- 

Gravity 

Per  Cent 

con- 

is! 

4° 
In  Vacuo. 

HC1 

by  Weight. 

tains 
Grams 
HC1. 

15° 

4° 
in  Vacuo. 

HC1 
by  Weight. 

tains 
Grams 
HC1. 

is! 

4° 
in  Vacuo. 

HC1 
by  Weight. 

tains 
Grama 
HC1. 

1.000 

0.16 

1.6 

1.075 

15.16 

163 

1.145 

28.61 

328 

1.005 

1.15 

12 

1.080 

16.15 

174 

1.150 

29.57 

340 

1.010 

2.14 

22 

1.085 

17.13 

186 

1.152 

29.95 

345 

1.015 

3.12 

32 

1.090 

18.11 

197 

1.155 

30.55 

353 

1.020 

4.13 

42 

1.095 

19.06 

209 

1.160 

31.52 

366 

1.025 

5.15 

53 

1.100 

20.01 

220 

1.163 

32.10 

373 

.030 

6.15 

64 

1.105 

20.97 

232 

1.165 

32.49 

379 

.035 

7.15 

74 

1.110 

21.92 

243 

1.170 

33.46 

392 

.040 

8.16 

85 

1.115 

22.86 

255 

1.171 

33.65 

394 

.045 

9.16 

96 

1.120 

23.82 

267 

1.175 

34.42 

404 

.050 

10.17 

107 

1.125 

24.78 

278 

1.180 

35.39 

418 

.055 

11.18 

118 

1.130 

25.75 

291 

1.185 

36.31 

430 

.060 

12.19 

129 

1.135 

26.70 

303 

1.190 

37.23 

443 

.065 

13.19 

141 

1.140 

27.66 

315 

1.195 

38.16 

456 

.070 

14.17 

152 

1.1425 

28.14 

322 

1.200 

39.11 

469 

COMPOSITION  OF  CONSTANT  BOILING 
HYDROCHLORIC  ACID* 


Pressure  mm.  of 
Mercury. 

Per  Cent  of 
HC1. 

Grams  constant 
boiling  distillate 
for  i  mol.  HC1. 

770 

20.218 

180.390 

760 

20.242 

180.170 

750 

20.266 

179.960 

740 

20.290 

179.745 

730 

20.314 

179.530 

Temperature  of  constant  boiling  hydrochloric  acid  is  108.54°  at  763  mm. 
Specific  gravity  1.09620". 

*  Hulett  and  Bonner,  Jour.  Am.  Chem.  Soc.  mi,  398. 


TABLES   AND   USEFUL  DATA 


785 


VII.— NITRIC   ACID 
BY  W.  C.  FERGUSON 


Degrees 
Baume. 

Sp.  Gr. 

^!F 
60°  *• 

Degrees 
Twaddell. 

Per  Cent 
HN03. 

Degrees 
Baume. 

Sp.  Gr. 

60°  F 
60° 

Degrees 
Twaddell. 

Per  Cent 
HN03. 

10.00 

1.0741 

14.82 

12.86 

21.25 

1.1718 

34.36 

28.02 

10.25 

.0761 

15.22 

13.18 

21.50 

1.1741 

34.82 

28.36 

10.50 

.0781 

15.62 

13.49 

21.75 

1.1765 

35.30 

28.72 

10.75 

.0801 

16.02 

13.81 

22.00 

1.1789 

35.78 

29.07 

11.00 

.0821 

16.42 

14.13 

22.25 

1.1813 

36.26 

29.43 

11.25 

.0841 

16.82 

14.44 

22.50 

1.1837 

36.74 

29.78 

11.50 

.0861 

17.22 

14.76 

22.75 

1.1861 

37.22 

30.14 

11.75 

1.0881 

17.62 

15.07 

23.00 

1.1885 

37.70 

30.49 

12.00 

1.0902 

18.04 

15.41 

23.25 

1.1910 

38.20 

30.86 

12.25 

1.0922 

18.44 

15.72 

23.50 

1.1934 

38.68 

31.21 

12.50 

1.0943 

18.86 

16.05 

23.75 

1.1959 

39.18 

31.58 

12.75 

1.0964 

19.28 

16.39 

24.00 

1.1983 

39.66 

31.94 

13.00 

1.0985 

19.70 

16.72 

24.25 

1.2008 

40.16 

32.31 

13.25 

1.1006 

20.12 

17.05 

24.50 

1.2033 

40.66 

32.68 

13.50 

1.1027 

20.54 

17.38 

24.75 

1.2058 

41.16 

33.05 

13.75 

1.1048 

20.96 

17.71 

25.00 

1.2083 

41.66 

33.42 

14.00 

1.1069 

21.38 

18.04 

25.25 

1.2109 

42.18 

33.80 

14.25 

1.1090 

21.80 

18.37 

25.50 

1.2134 

42.68 

34.17 

14.50 

1.1111 

22.22 

18.70 

25.75 

1.2160 

43.20 

34.56 

14.75 

1.1132 

22.64 

19.02 

26.00 

1.2185 

43.70 

34.94 

15.  CO 

1.1154 

23.08 

19.36 

26.25 

1.2211 

44.22 

35.33 

15.25 

1.1176 

23.52 

19.70 

26.50 

1.2236 

44.72 

35.70 

15.50 

1.1197 

23.94 

20.02 

26.75 

1.2262 

45.24 

36.09 

15.75 

1.1219 

24.38 

20.36 

27.00 

1.2288 

45.76 

36.48 

16.00 

1.1240 

24.80 

20.69 

27.25 

1.2314 

46.28 

36.87 

16.25 

1.1262 

25.24 

21.03 

27.50 

1.2340 

46.80 

37.26 

16.50 

1.1284 

25.68 

21.36 

27.75 

1.2367 

47.34 

37.67 

16.75 

1.1306 

26.12 

21.70 

28.00 

1.2393 

47.86 

38.06 

17.00 

1.1328 

26.56 

22.04 

28.25 

1.2420 

48.40 

38.46 

17.25 

1.1350 

27.00 

22.38 

28.50 

1.2446 

48.92 

38.85 

17.50 

1.1373 

27.46 

22.74 

28.75 

1.2473 

49.46 

39.25 

17.75 

1  .  1395 

27.90 

23.08 

29.00 

1.2500 

50.00 

39.66 

18.00 

1.1417 

28.34 

23.42 

29.25 

1.2527 

50.54 

40.06 

18.25 

1.1440 

28.80 

23.77 

29.50 

1.2554 

51.08 

40.47 

18.50 

1  .  1462 

29.24 

24.11 

29.75 

.2582 

51.64 

40.89 

18.75 

1.1485 

29.70 

24.47 

30.00 

.2609 

52.18 

41.30 

19.00 

1.1508 

30.16 

24.82 

30.25 

.2637 

52.74 

41.72 

19.25 

1.1531 

30.62 

25.18 

30.50 

.2664 

53.28 

42.14 

19.50 

1.1554 

31.08 

25.53 

30.75 

.2692 

53.84 

42.58 

19.75 

1.1577 

31.54 

25.88 

31.00 

.2719 

54.38 

43.00 

20.00 

1.16CO 

32.00 

26.24 

31.25 

.2747 

54.94 

43.44 

20.25 

1.1624 

32.48 

26.61 

31.50 

.2775 

55.50 

43.89 

20.50 

1.1647 

32.94 

26.96 

31.75 

.2804 

56.08 

44.34 

20.75 

1.1671 

33.42 

27.33 

32.00 

.2832 

56.64 

44.78 

21.00 

1.1694 

33.88 

27.67 

32.25 

.2861 

57.22 

45.24 

786 


TABLES   AND   USEFUL   DATA 


VII.— NITRIC   ACID    (Continued) 


Decrees 

Baume. 

Sp.  Gr. 

6o°F 
6^>*' 

Degrees 

Twaddell. 

Per  Cent 
HN03. 

Degrees 
Baume. 

V?" 

60°    ' 

Degrees 
Twaddell. 

Per  Cent 
HN03. 

32.50 

1.2889 

57.78 

45.68 

40.75 

1.3909 

78.18 

63.48 

32.75 

1.2918 

58.36 

46.14 

41.00 

1.3942 

78.84 

64.20 

33.00 

1.2946 

58.92 

46.58 

41.25 

1.3976 

79.52 

64.93 

33.25 

1.2975 

59.50 

47.04 

41.50 

1.4010 

80.20 

65.67 

33.50 

1.3004 

60.08 

47.49 

41.75 

1.4044 

80.88 

66.42 

33.75 

1.3034 

60.68 

47.95 

42.00 

1.4078 

81.56 

67.18 

34.00 

1.3063 

61.26 

48.42 

42.25 

1.4112 

82.24 

67.95 

34.25 

1.3093 

61.86 

48.90 

42.50 

1.4146 

82.92 

68.73 

34.50 

1.3122 

62.44 

49.35 

42.75 

1.4181 

83.62 

69.52 

34.75 

1.3152 

63.04 

49.83 

43.00 

1.4216 

84.32 

70.33 

35.00 

1.3182 

63.64 

50.32 

43.25 

1.4251 

85.02 

71.15 

35.25 

1.3212 

64.24 

50.81 

43.50 

1.4286 

85.72 

71.98 

35.50 

1.3242 

64.84 

51.30 

43.75 

1.4321 

86.42 

72.82 

35.75 

1.3273 

65.46 

51.80 

44.00 

1.4356 

87.12 

73.67 

36.00 

1.3303 

66.06 

52.30 

44.25 

1.4392 

87.84 

74.53 

36.25 

1.3334 

66.68 

52.81 

44.50 

1.4428 

88.56 

75.40 

36.50 

1.3364 

67.28 

53.32 

44.75 

1.4464 

89.28 

76.28 

36.75 

1.3395 

67.90 

53.84 

45.00 

1.4500 

90.00 

77.17 

37.00 

1.3426 

68.52 

54.36 

45.25 

1.4536 

90.72 

78.07 

37.25 

1.3457 

69.14 

54.89 

45.50 

1.4573 

91.46 

79.03 

37.50 

1.3488 

69.76 

55.43 

45.75 

1.4610 

92.20 

80.04 

37.75 

1.3520 

70.40 

55.97 

46.00 

1.4646 

92.92 

81.08 

38.00 

1.3551 

71.02 

56.52 

46.25 

1.4684 

93.68 

82.18 

38.25 

1.3583 

71.66 

57.08 

46.50 

1.4721 

94.42 

83.33 

38.50 

1.3615 

72.30 

57.65 

46.75 

1.4758 

95.16 

84.48 

38.75 

1.3647 

72.94 

58.23 

47.00 

1.4796 

95.92 

85.70 

39.00 

1.3679 

73.58 

58.82 

47.25 

1.4834 

96.68 

86.98 

89.25 

1.3712 

74.24 

59.43 

47.50 

1.4872 

97.44 

88.32 

39.50 

1.3744 

74.88 

60.06 

47.75 

1.4910 

98.20 

89.76 

39.75 

1.3777 

75.54 

60.71 

48.00 

1.4948 

98.96 

91.35 

40.00 

1.3810 

76.20 

61.38 

48.25 

1.4987 

99.74 

93.13 

40.25 

1.3843 

76.86 

62.07 

48.50 

1.5026 

100.52 

95.11 

40.50 

1.3876 

77.52 

62.77 

Specific  Gravity  determinations  were  made  at  60°  F.,  compared  with  water  at  60°  F. 
From  the  Specific  Gravities,  the  corresponding  degrees  Bauru6  were  calculated  by  the 

following  formula ;  Baume  =  145 ™-  . 

Sp.  Gr. 

Baume"  Hydrometers  for  use  with  this  table  must  be  graduated  by  the  above  formula, 
Which  formula  should  always  be  printed  on  the  scale. 

Atomic  weights  from  F.  W.  Clarke's  table  of  1901.     O  =  16. 

ALLOWANCE  FOR  TEMPERATURE: 

At  10°  —  20°     Be\  —  1/30°  Be\    or    .00029  Sp.  Gr.  =  1°  F. 

20°  —  30°     B£.  —  1/23°  Be.    or    .00044  "      "    =  1°  F. 

30°  _  40°     Be\  —  1/20°  Be\    or    .00060  "      "    =  1°  F. 

40°  —  48.5°  Be\  —  1/17°  Be\    or    .00084  "      "    =  1°  F. 

AUTHORITY— W.  C.  FERGUSON. 

This  table  has  been  approved  and  adopted  as  a  Standard  by  the  Manufacturing  Chemists' 
Association  of  the  United  States. 

W.  H.  BOWER,  JAS.  L.  MORGAN, 

HENRY  HOWARD,     ARTHUR  WYMAN, 
New  York,  May  14,  1903.  A.  G.  ROSENGARTEN,  Executive  Committee 


TABLES  AND   USEFUL  DATA 
VIII.— NITRIC  ACID 

LUNGE  AND  REY 


787 


Specific 

Gravity 

is! 

in  vacuo 

100  parts  by  weight 
contain 

i  liter  con- 
tains grams 

Specific 
Gravity 
15° 

4° 
in  vacuo 

100  parts  by  weight 
contain 

i  liter  con- 
tains grams 

% 
N205 

% 
HN03 

N2O5 

HN03 

N205 

HNO3 

N205 

HN03 

1.000 

0.08 

0.10 

1 

1 

1.195 

27.10 

31.62 

324 

378 

1.005 

0.85 

1.00 

8 

10 

1.200 

27.74 

32.36 

333 

388 

1.010 

1.62 

1.90 

16 

19 

1.205 

28.36 

33.09 

342 

399 

1.015 

2.39 

2.80 

24 

28 

.210 

28.99 

33.82 

351 

409 

1.020 

3.17 

3.70 

33 

38 

.215 

29.61 

34.55 

360 

420 

1.025 

3.94 

4.60 

40 

47 

.220 

30.24 

35.28 

369 

430 

1.030 

4.71 

5.50 

49 

57 

.225 

30.88 

36.03 

378 

441 

1.035 

5.47 

6.38 

57 

66 

.230 

31.53 

36.78 

387 

452 

1.040 

6.22 

7.26 

64 

75 

.235 

32.17 

37.53 

397 

463 

1.045 

6.97 

8.13 

73 

85 

.240 

32.82 

38.29 

407 

475 

1.050 

7.71 

8.99 

81 

94 

.245 

33.47 

39.05 

417 

486 

1.055 

8.43 

9.84 

89 

104 

.250 

34.13 

39.82 

427 

498 

1.060 

9.15 

10.68 

97 

113 

.255 

34.78 

40.58 

437 

509 

1.065 

9.87 

11.51 

105 

123 

1.260 

35.44 

41.34 

447 

521 

1.070 

10.57 

12.33 

113 

132 

1.265 

36.09 

42.10 

457 

533 

1.075 

11.27 

13.15 

121 

141 

1.270 

36.75 

42.87 

467 

544 

1.080 

11.96 

13.95 

129 

151 

1.275 

37.41 

43.64 

477 

556 

1.085 

12.64 

14.74 

137 

160 

1.280 

38.07 

44.41 

487 

568 

1.090 

13.31 

15.53 

145 

169 

1.285 

38.73 

45.18 

498 

581 

1.095 

13.99 

16.32 

153 

179 

1.290 

39.39 

45.95 

508 

593 

1.100 

14.67 

17.11 

161 

188 

1.295 

40.05 

46.72 

519 

605 

1.105 

15.34 

17.89 

170 

198 

1.300 

40.71 

47.49 

529 

617 

1.110 

16.00 

18.67 

177 

207 

1.305 

41.37 

48.26 

540 

630 

1.115 

16.67 

19.45 

186 

217 

1.310 

42.06 

49.07 

551 

643 

1.120 

17.34 

20.23 

195 

227 

1.315 

42.76 

49.89 

562 

656 

1.125 

18.00 

21.00 

202 

236 

.320 

43.47 

50.71 

573 

669 

1.130 

18.66 

21.77 

211 

246 

.325 

44.17 

51.53 

585 

683 

1.135 

19.32 

22.54 

219 

256 

.330 

44.89 

52.37 

597 

697 

1.140 

19.98 

23.31 

228 

266 

.3325 

45.26 

52.80 

603 

704 

1.145 

20.64 

24.08 

237 

276 

.335 

45.62 

53.22 

609 

710 

1.150 

21.29 

24.84 

245 

286 

.340 

46.35 

54.07 

621 

725 

1.155 

21.94 

25.60 

254 

296 

.345 

47.08 

54.93 

633 

739 

1.160 

22.60 

26.36 

262 

306 

.350 

47.82 

55.79 

645 

753 

1.165 

23.25 

27.12 

271 

316 

.355 

48.57 

56.66 

658 

768 

1.170 

23.90 

27.88 

279 

326 

1.360 

49.35 

57.57 

671 

783 

1.175 

24.54 

28.63 

288 

336 

1.365 

50.13 

58.48 

684 

798 

1.180 

25.18 

29.38 

297 

347 

1.370 

50.91 

59.39 

698 

814 

1.185 

25.83 

30.13 

306 

357 

1.375 

51.69 

60.30 

711 

829 

1.190 

26.47 

30.88 

315 

367 

1.380 

52.52 

61.27 

725 

846 

788 


TABLES   AND   USEFUL   DATA 
VIII.— NITRIC   ACID    (Continued) 


Specific 
Gravity 

2g 

in  vacuo 

ioo  parts  by  weight 
contain 

i  liter  con- 
tains grams 

Soecific 
Gravity 
I5£ 

4° 
in  vacuo 

i  oo  parts  by  weight 
contain 

i  liter  con- 
tains grams 

% 
N205 

HNO3 

N205 

HNO3 

& 

HNO3 

N206 

HNO3 

1.3833 

53.08 

61.92 

735 

857 

1.495 

78.52 

91.60 

1174 

1369 

1.385 

53.35 

62.24 

739 

862 

.500 

80.65 

94.09 

1210 

1411 

1.390 

54.20 

63.23 

753 

879 

.501 

81.09 

94.60 

1217 

1420 

1.395 

55.07 

64.25 

768 

896 

.502 

81.50 

95.08 

1224 

1428 

1.400 

55.97 

65.30 

783 

914 

.503 

81.91 

95.55 

1231 

1436 

1.405 

56.92 

66.40 

800 

933 

.504 

82.29 

96.00 

1238 

1444 

1.410 

57.86 

67.50 

816 

952 

.505 

82.63 

96.39 

1244 

1451 

1.415 

58.83 

68.63 

832 

971 

.506 

82.94 

96.76 

1249 

1457 

1.420 

59.83 

69.80 

849 

991 

.507 

83.26 

97.13 

1255 

1464 

1.425 

60.84 

70.98 

867 

1011 

1.508 

83.58 

97.50 

1260 

1470 

1.430 

61.86 

72.17 

885 

1032 

1.509 

83.87 

97.84 

1265 

1476 

1.435 

62.91 

73.39 

903 

1053 

1.510 

84.09 

98.10 

1270 

1481 

1.440 

64.01 

74.68 

921 

1075 

1.511 

84.28 

98.32 

1274 

1486 

1.445 

65.13 

75.98 

941 

1098 

1.512 

84.46 

98.53 

1277 

1490 

1.450 

66.24 

77.28 

961 

1121 

1.513 

84.63 

98.73 

1280 

1494 

1.455 

67.38 

78.60 

981 

1144 

1.514 

84.78 

98.90 

1283 

1497 

1.460 

68.56 

79.98 

1001 

1168 

1.515 

84.92 

99.07 

1287 

1501 

1.465 

69.79 

81.42 

1023 

1193 

1.516 

85.04 

99.21 

1289 

1504 

1.470 

71.06 

82.90 

1045 

1219 

1.517 

85.15 

99.34 

1292 

1507 

1.475 

72.39 

84.45 

1068 

1246 

1.518 

85.26 

99.46 

1294 

1510 

1.480 

73.76 

86.05 

1092 

1274 

1.519 

85.35 

99.57 

1296 

1512 

1.485 

75.18 

87.70 

1116 

1302 

1.520 

85.44 

99.67 

1299 

1515 

1.490 

76.80 

89.60 

1144 

1335 

TABLES  AND  USEFUL  DATA 


789 


IX.— PHOSPHORIC   ACID    AT,"  17.5° 


Specific 
Gravity 

Per 
Cent. 
P205. 

Per  Cent. 
H3P04. 

Specific 
Gravity 

Per 
Cent. 
P205. 

Per  Cent. 
H3P04. 

Specific 
Gravity 

Per 
Cent. 
P206. 

Per  Cent. 
H3PO<. 

1.809 

68.0 

93.67 

1.462 

46.0 

63.37 

1.208 

24.0 

33.06 

1.800 

67.5 

92.99 

1.455 

45.5 

62.68 

1.203 

23.5 

32.37 

1.792 

67.0 

92.30 

1.448 

45.0 

61.99 

1.198 

23.0 

31.68 

1.783 

66.5 

91.61 

1.441 

44.5 

61.30 

1.193 

22.5 

30.99 

1.775 

66.0 

90.92 

1.435 

44.0 

60.61 

1.188 

22.0 

30.31 

1.766 

65.5 

90.23 

1.428 

43.5 

59.92 

1.183 

21.5 

29.62 

1.758 

65.0 

89.54 

1.422 

43.0 

59.23 

1.178 

21.0 

28.93 

1.750 

64.5 

88.85 

1.415 

42.5 

58.55 

1.174 

20.5 

28.24 

1.741 

64.0 

88.16 

1.409 

42.0 

57.86 

1.169 

20.0 

27.55 

1.733 

63.5 

87.48 

1.402 

41.5 

57.17 

1.164 

19.5 

26.86 

1.725 

63.0 

86.79 

1.396 

41.0 

56.48 

1.159 

19.0 

26.17 

1.717 

62.5 

86.10 

1.389 

40.5 

55.79 

1.155 

18.5 

25.48 

1.709 

62.0 

85.41 

1.383 

40.0 

55.10 

1.150 

18.0 

24.80 

1.701 

61.5 

84.72 

1.377 

39.5 

54.41 

1.145 

17.5 

24.11 

1.693 

61.0 

84.03 

1.371 

39.0 

53.72 

1.140 

17.0 

23.42 

1.685 

60.5 

83.34 

1.365 

38.5 

53.04 

1.135 

16.5 

22.73 

1.677 

60.0 

82.65 

1.359 

38.0 

52.35 

1.130 

16.0 

22.04 

1.669 

59.5 

81.97 

1.354 

37.5 

51.66 

1.126 

15.5 

21.35 

1.661 

59.0 

81.28 

1.348 

37.0 

50.97 

1.122 

15.0 

20.66 

1.653 

58.5 

80.59 

1.342 

36.5 

50.28 

1.118 

14.5 

19.97 

1.645 

58.0 

79.90 

1.336 

36.0 

49.59 

1.113 

14.0 

19.28 

1.637 

57.5 

79.21 

1.330 

35.5 

48.90 

1.109 

13.5 

18.60 

1.629 

57.0 

78.52 

1.325 

35.0 

48.21 

1.104 

13.0 

17.91 

1.621 

56.5 

77.83 

1.319 

34.5 

47.52 

1.100 

12.5 

17.22 

1.613 

56.0 

77.14 

1.314 

34.0 

46.84 

1.096 

12.0 

16.53 

1.605 

55.5 

76.45 

1.308 

33.5 

46.15 

1.091 

11.5 

15.84 

1.597 

55.0 

75.77 

1.303 

33.0 

45.46 

1.087 

11.0 

15.15 

1.589 

54.5 

75.08 

1.298 

32.5 

44.77 

1.083 

10.5 

14.46 

1.581 

54.0 

74.39 

1.292 

32.0 

44.08 

1.079 

10.0 

13.77 

1.574 

53.5 

73.70 

1.287 

31.5 

43.39 

1.074 

9.5 

13.09 

1.566 

53.0 

73.01 

1.281 

31.0 

42.70 

1.070 

9.0 

12.40 

1.559 

52.5 

72.32 

1.276 

30.5 

42.01 

1.066 

8.5 

11.71 

1.551 

52.0 

71.63 

1.271 

30.0 

41.33 

1.062 

8.0 

11.02 

1.543 

51.5 

70.94 

1.265 

29.5 

40.64 

1.058 

7.5 

10.33 

1.536 

51.0 

70.26 

1.260 

29.0 

39.95 

1.053 

7.0 

9.64 

1.528 

50.5 

69.57 

1.255 

28.5 

39.26 

1.049 

6.5 

8.95 

1.521 

50.0 

68.88 

1.249 

28.0 

38.57 

1.045 

6.0 

8.26 

1.513 

49.5 

68.19 

1.244 

27.5 

37.88 

1.041 

5.5 

7.57 

1.505 

49.0 

67.50 

1.239 

27.0 

37.19 

1.037 

5.0 

6.89 

1.498 

48.5 

66.81 

1.233 

26.5 

36.50 

1.033 

4.5 

6.20 

1.491 

48.0 

66.12 

1.228 

26.0 

35.82 

1.029 

4.0 

5.51 

1.484 

47.5 

65.43 

1.223 

25.5 

35.13 

1.025 

3.5 

4.82 

1.476 

47.0 

64.75 

1.218 

25.0 

34.44 

1.021 

3.0 

4.13 

1.469 

46.5 

64.06  1 

1.213 

24.5 

33.75 

1.017 

2.5 

3.44 

790 


TABLES   AND   USEFUL   DATA 


X.— SULPHURIC   ACID 
BY  W.  C.  FERGUSON  AND  H.  P.  TALBOT 


Degrees 
Baume. 

Specific 
Gravity 

^F 
60° 

Degrees 
Twaddell. 

Per 

Cent 
H2S04. 

Weight  of 
i  Cu.  Ft.  in 
Lbs.  Av. 

Per  Cent 
0.  V.* 

Pounds  0.  V. 
in 
i  Cubic  Foot. 

0 

1.0000 

0.0 

0.00 

62.37 

0.00 

0.00 

1 

1.0069 

1.4 

1.02 

62.80 

1.09 

0.68 

2 

1.0140 

2.8 

2.08 

63.24 

2.23 

1.41 

3 

1.0211 

4.2 

3.13 

63.69 

3.36 

2.14 

4 

1.0284 

5.7 

4.21 

64.14 

4.52 

2.90 

5 

1.0357 

7.1 

5.28 

64.60 

5.67 

3.66 

6 

1.0432 

8.6 

6.37 

65.06 

6.84 

4.45 

7 

1.0507 

10.1 

7.45 

65.53 

7.99 

5.24 

8 

1.0584 

11.7 

8.55 

66.01 

9.17 

6.06 

9 

1.0662 

13.2 

9.66 

66.50 

10.37 

6.89 

10 

1.0741 

14.8 

10.77 

66.99 

11.56 

7.74 

11 

1.0821 

16.4 

11.89 

67.49 

12.76 

8.61 

12 

1.0902 

18.0 

13.01 

68.00 

13.96 

9.49 

13 

1.0985 

19.7 

14.13 

68.51 

15.16 

10.39 

14 

1  .  1069 

21.4 

15.25 

69.04 

16.36 

11.30 

15 

1.1154 

23.1 

16.38 

69.57 

17.58 

12.23 

16 

1.1240 

24.8 

17.53 

70.10 

18.81 

13.19 

17 

1.1328 

26.6 

18.71 

70.65 

20.08 

14.18 

18 

1.1417 

28.3 

19.89 

71.21 

21.34 

15.20 

19 

1  .  1508 

30.2 

21.07 

71.78 

22.61 

16.23 

20 

1  .  1600 

32.0 

22.25 

72.35 

23.87 

17.27 

21 

1.1694 

33.9 

23.43 

72.94 

25.14 

18.34 

22 

1.1789 

35.8 

24.61 

73.53 

26.41 

19.42 

23 

1.1885 

37.7 

25.81 

74.13 

27.69 

20.53 

24 

1.1983 

39.7 

27.03 

74.74 

29.00 

21.68 

Sp.  Gr.  determinations  were  made  at  60°  F.,  compared  with  water  at  60°  F. 

From  the  Sp.  Grs.,  the  corresponding  degrees  Baume"  were  calculated  by 
the  following  formula:  Baume  =145  — 145/Sp.  Gr. 

Baume"  Hydrometers  for  use  with  this  table  must  be  graduated  by  the 
above  formula,  which  formula  should  always  be  printed  on  the  scale. 

*  66°  Baume*  =  Sp.  Gr.  1.8354  =  Oil  of  Vitriol  (O.  V.). 

1  cu.  ft.  water  at  60°  F.  weighs  62.37  Ibs.  av. 

Atomic  weights  from  F.  W.  Clarke's  table  of  1901.     O  =  16. 

H2S04   =  100  per  cent. 


%  H2S04 

O.  V.   =  93.19  = 

60°      =  77.67  = 

50°      =  62.18  = 


/o 


O.  V.  %60° 

100.00  =  119.98 

83.35  =  100.00 

66.72  =  80.06 


TABLES   AND   USEFUL   DATA 


791 


X.— SULPHURIC    ACID    (Continued) 


*  Freezing 

Degrees 
Baume. 

(Melting) 
Point. 

APPROXIMATE   BOILING  POINTS 

F. 

50°  B,    295°  F. 

60°         386°  " 

0 

32.0 

61°         400° 

1 

31.2 

62°         415° 

2 

30.5 

63°         432° 

3 

29.8 

64°         451° 

4 

28.9 

65°         485° 

66°  "     538° 

5 

28.1 

97  9 

7 

4Uf    •  M 

26.3 

FIXED  POINTS 

8 

25.1 

9 

24.0 

Specific 

Per  Cent 

Specific 

Per  Cent 

Gravity. 

H2S04. 

Gravity. 

H2S04. 

10 

99  8 

1U 

11 

.*-*-  .  O 

21.5 

1.0000 

.00 

1.5281 

62.34 

12 

20.0 

1.0048 

.71 

1  .  5440 

63.79 

13 

18.3 

1.0347 

5.14 

1.5748 

66.51 

14 

16.6 

1.0649 

9.48 

1.6272 

71.00 

15 

14.7 

1.0992 

14.22 

1.6679 

74.46 

16 

12.6 

1.1353 

19.04 

1.7044 

77.54 

17 

10.2 

1.1736 

23.94 

1.7258 

79.40 

18 

7.7 

1.2105 

28.55 

1.7472 

81.32 

19 

4.8 

1.2513 

33.49 

1.7700 

83.47 

1  .  2951 

38.64 

.7959 

86.36 

20 

+   1.6 

1.3441 

44.15 

.8117 

88.53 

21 

-   1.8 

1.3947 

49.52 

.8194 

89.75 

22 

-   6.0 

1.4307 

53.17 

.8275 

91.32 

23 

-11 

1.4667 

56.68 

.8354 

93.19 

24 

-16 

1.4822 

58.14 

Acids  stronger  than  66°  Be.  should  have  their  percentage  compositions 
determined  by  chemical  analysis. 

*  Calculated  from  Pickering's  results,  Jour,  of  Lon.  Ch.  Soc.,  vol.  57,  p.  363. 

AUTHORITIES  —  W.  C.  FERGUSON;  H.  P.  TALBOT. 

This  table  has  been  approved  and  adopted  as  a  standard  by  the  Manu- 
facturing Chemists'  Association  of  the  United  States. 

W.  H.  BOWER, 
HENRY  HOWARD, 
JAS.  L.  MORGAN, 
ARTHUR  WYMAN, 
A.  G.  ROSENGARTEN, 
New  York,  June  23,  1904.  Executive  Committees 


792 


TABLES  AND  USEFUL  DATA 


X.— SULPHURIC   ACID    (Continued) 


Degrees 

Baume 

Specific 
Gravity 
60° 
&F« 

Degrees 
Twaddell. 

Per 
Cent 
H3S04. 

weight  of 
i  Cu.  Ft.  in 
Lbs.  Av. 

Per  Cent 
0.  V. 

Pounds  0.  V. 
in 
i  Cubic  Foot. 

25 

1.2083 

41.7 

28.28 

75.36 

30.34 

22.87 

26 

1.2185 

43.7 

29.53 

76.00 

31.69 

24.08 

27 

1.2288 

45.8 

30.79 

76.64 

33.04 

25.32 

28 

1.2393 

47.9 

32.05 

77.30 

34.39 

26.58 

29 

1.2500 

50.0 

3H.33 

77.96 

35.76 

27.88 

30 

1.2609 

52.2 

34.63 

78.64 

37.16 

29.22 

31 

1.2719 

54.4 

35.93 

79.33 

38.55 

30.58 

32 

1.2832 

56.6 

37.26 

80.03 

39.98 

32.00 

33 

1.2946 

58.9 

38.58 

80.74 

41.40 

33.42 

34 

1.3063 

61.3 

39.92 

81.47 

42.83 

34.90 

35 

1.3182 

63.6 

41.27 

82.22 

44.28 

36.41 

36 

1.3303 

66.1 

42.63 

82.97 

45.74 

37.95 

37 

1.3426 

68.5 

43.99 

83.74 

47.20 

39.53 

38 

1.3551 

71.0 

45.35 

84.52 

48.66 

41.13 

39 

1.3679 

73.6 

46.72 

85.32 

50.13 

42.77 

40 

1.3810 

76.2 

48.10 

86.13 

51.61 

44.45 

41 

1.3942 

78.8 

49.47 

86.96 

53.08 

46.16 

42 

1.4078 

81.6 

50.87 

87.80 

54.58 

47.92 

43 

1.4216 

84.3 

52.26 

88.67 

56.07 

49.72 

44 

1.4356 

87.1 

53.66 

89.54 

57.58 

51.56 

45 

1.4500 

90.0 

55.07 

90.44 

59.09 

53.44 

46 

1.4646 

92.9 

56.48 

91.35 

60.60 

55.36 

47 

1.4796 

95.9 

57.90 

92.28 

62.13 

57.33 

48 

1.4948 

99.0 

59.32 

93.23 

63.65 

59.34 

49 

1.5104 

102.1 

60.75 

94.20 

65.18 

61.40 

50 

1.5263 

105.3 

62.18 

95.20 

66.72 

63.52 

51 

1.5426 

108.5 

63.66 

96.21 

68.31 

65.72 

52 

1.5591 

111.8 

65.13 

97.24 

69.89 

67.96 

53 

1.5761 

115.2 

66.63 

98.30 

71.50 

70.28 

54 

1.5934 

118.7 

68.13 

99.38 

73.11 

72.66 

55 

1.6111 

122.2 

69.65 

100.48 

74.74 

75.10 

56 

1.6292 

125.8 

71.17 

101.61 

76.37 

77.60 

57 

1.6477 

129.5 

72.75 

102.77 

78.07 

80.23 

58 

1.6667 

133.3 

74.36 

103.95 

79.79 

82.95 

59 

1.6860 

137.2 

75.99 

105.16 

81.54 

85.75 

TABLES  AND   USEFUL  DATA 


793 


X.— SULPHURIC    ACID    (Continued) 


Degrees 
Baume  . 

*  Freezing 

(Melting) 
Point. 

°F. 

\1  T  OW  \  NPF    TTOT?    TPMPFP  \  TTTR  T? 

25 

-23 

A.Liij\J  VV  AiN  \jHi     -T  L^-CL     J.  HilVJ.i  H/XWl.  1  U  Xvll* 

26 

-30 

At  10°    B6.  .029°B6.or    .00023  Sp.  Gr.    =  1°  F. 

27 

-39 

"    20°      "    .036°         "     .00034       "        =  1°  " 

28 

-49 

"    30°      "    .035°         "     .00039       "        =  1°  " 

29 

-61 

"    40°      "    .031°         "     .00041       "        =  1°  " 

"    50°      "    .028°         "     .00045       "        =  1°  " 

30 

-74 

"    60°      "    .026°         "     .00053       "        =  1°  " 

31 

-82 

"    63°      "    .026°         "     ,00057       "        =  1°  " 

32 

-96 

"    66°      "    .0235°        "     .00054       "       =  1°  " 

33 

-97 

34 

-91 

35 

81 

36 

—  70 

37 

-60 

Per  Cent 

Pounds 
60°  Baume 

Per  Cent 

50° 

Pounds 
50°  Baume 

38 
39 

-53 

-47 

Baume. 

in 
i  Cubic  Foot. 

Baume. 

in 
i  Cubic  Foot. 

40 

-41 

61.93 

53.34 

77.36 

66.63 

41 

-35 

63.69 

55.39 

79.56 

69.19 

42 

-31 

65.50 

57.50 

81.81 

71.83 

43 

-27 

67.28 

59.66 

84.05 

74.53 

44 

-23 

69.09 

61.86 

86.30 

77.27 

45 

-20 

70.90 

64.12 

88.56 

80.10 

46 

-14 

72.72 

66.43 

90.83 

82.98 

47 

-15 

74.55 

68.79 

93.12 

85.93 

48 

-18 

76.37 

71.20 

95.40 

88.94 

49 

-22 

78.22 

73.68 

97.70 

92.03 

50 

-27 

80.06 

76.21 

100.00 

95.20 

51 

-33 

81.96 

78.85 

102.38 

98.50 

52 

-39 

83.86 

81.54 

104.74 

101.85 

53 

-49 

85.79 

84.33 

107.15 

105.33 

54 

-59 

87.72 

87.17 

109.57 

108.89 

55 

A 

89.67 

90.10 

112.01 

112.55 

56 

!!  s 

91.63 

93.11 

114.46 

116.30 

57 

•  •   ~£ 

93.67 

96.26 

117.00 

120.24 

58 

•  •    W 

95.74 

99.52 

119.59 

124.31 

59 

-  T 

97.84 

102.89 

122.21 

128.52 

794 


TABLES  AND   USEFUL  DATA 


X.— SULPHURIC    ACID    (Continued) 


Degrees 
Baumd. 

Specific 
Gravity 
60°  F. 

Degrees 
Twaddell. 

Per  Cent 
HiSCU. 

Weight  of 
1  Cu.  Ft.  in 
Lbs.  Av. 

Per  Cent 
O.  V. 

Pounds  O.  V. 
in 
1  Cubic  Foot. 

60° 

60 

1.7059 

141.2 

77.67 

106.40 

83.35 

88.68 

61 

1.7262 

145.2 

79.43 

107.66 

85.23 

91.76 

62 

1.7470 

149.4 

81.30 

108.96 

87.24 

95.06 

63 

1.7683 

153.7 

83.34 

110.29 

89.43 

98.63 

64 

1.7901 

158.0 

85.66 

111.65 

91.92 

102.63 

64i 

1.7957 

159.1 

86.33 

112.00 

92.64 

103.75 

64^ 

1.8012 

160.2 

87.04 

112.34 

93.40 

104.93 

64| 

1.8068 

161.4 

87.81 

112.69 

94.23 

106.19 

65 

1.8125 

162.5 

88.65 

113.05 

95.13 

107.54 

65* 

1.8182 

163.6 

89.55 

113.40 

96.10 

108.97 

65* 

1.8239 

164.8 

90.60 

113.76 

97.22 

110.60 

65| 

1.8297 

165.9 

91.80 

114.12 

98.51 

112.42 

66 

1.8354 

167.1 

93.19 

114.47 

100.00 

114.47 

Degrees 
Baume. 

Freezing 
(Melting) 
Point. 

Per  Cent 
60°  Baume. 

Pounds 
60°  Baume  in 
Cubic  Foot. 

Per  Cent 
50°  Baume. 

Pounds 
50°  Baum6  in 
Cubic  Foot. 

60 

+  12.6 

100.00 

106.40 

124.91 

132.91 

61 

27.3 

102.27 

110.10 

127.74 

137.52 

62 

39.1 

104.67 

114.05 

130.75 

142.47 

63 

46.1 

107.30 

118.34 

134.03 

147.82 

64 

46.4 

110.29 

123.14 

137.76 

153.81 

64* 

43.6 

111.15 

124.49 

138.84 

155.50 

64| 

41.1 

112.06 

125.89 

139.98 

157.25 

64f 

37.9 

113.05 

127.40 

141.22 

159.14 

65 

33.1 

114.14 

129.03 

142.57 

161.17 

65J 

24.6 

115.30 

130.75 

144.02 

163.32 

65| 

13.4 

116.65 

132.70 

145.71 

165.76 

65| 

-  1 

118.19 

134.88 

147.63 

168.48 

66 

-29 

119.98 

137.34 

149.87 

171.56 

XL— SULPHURIC  ACID  TABLE 

94-100%  H2S04 
BY  H.  B.  BISHOP 


Be. 

Sp.  Gr.  at  60°  F. 

Per  Cent. 
HjSOi 

Wt.  1  Cu.  Ft. 

Allowance  for  Temperature. 

66 

.8354 

93.19 

114.47 

At    94%  .00054  sp.gr.  =  1  ° 

F. 

66.12 

.8381 

94.00 

114.64 

"    96      .0053       "     =1° 

\<" 

66.23 

.8407 

95.00 

114.80 

"    97.5  .00052      "     =1° 

F. 

66.31 

.8427 

96.00 

114.93 

"  100      .00052     "     =1° 

F. 

66.36 

.8437 

97.00 

114.99 

66.36 

.8439 

97.50 

114.99 

66.36 

.8437 

98.00 

114.99 

66.30 

.8424 

99.00 

114.91 

66.16 

.8391 

100.00 

114.70 

TABLES   AND   USEFUL   DATA 
FUMING  SULPHURIC  ACID  EQUIVALENTS 


795 


Total 
S03 

Equivalent 
H2S04       1 

Per  Cent 
H2S04 

Per  Cent 
Free  SO3 

Total 
S03 

Equivalent 
H2SO4 

Per  Cent 
H2SOi 

Per  Cent 
Free  SOs 

81.63 

100.00 

100 

0 

90.82 

111.25 

50 

50 

81.82 

100.23 

99 

1 

91.00 

111.48 

49 

51 

82.00 

100.45 

98 

2 

91.18 

111.70 

48 

52 

82.18 

100.67 

97 

3 

91.37 

111.93 

47 

53 

82.37 

100.90 

96 

4 

91.55 

112.15 

46 

54 

82.55 

101.13 

95 

5 

91.73 

112.37 

45 

55 

82.73 

101.35 

94 

6 

91.92 

112.60 

44 

56 

82.92 

101.58 

93 

7 

92.10 

112.82 

43 

57 

83.10 

101.80 

92 

8 

92.29 

113.05 

42 

58 

83.29 

102.03 

91 

9 

92.47 

113.28 

41 

59 

83.47 

102.25 

90 

11 

92.65 

113.50 

40 

60 

83.65 

102.47 

89 

11 

92.84 

113.73 

39 

61 

83.84 

102.70 

88 

12 

93.02 

113.95 

38 

62 

84.02 

102.92 

87 

13 

93.20 

114.17 

37 

63 

84.20 

103.15 

86 

14 

93.39 

114.40 

36 

64 

84.39 

103.38 

85 

15 

93.57 

114.62 

35 

65 

84.57 

103.60 

84 

16 

93.76 

114.85 

34 

66 

84.75 

103.82 

83 

17 

93.94 

115.08 

33 

67 

84.94 

104.05 

82 

18 

94.12 

115.30 

32 

68 

85.12 

104.27 

81 

19 

94.31 

115.53 

31 

69 

85.31 

104.50 

80 

20 

94.49 

115.75 

30 

70 

85.49 

104.73 

79 

21 

94.67 

115.97 

29 

71 

85.67 

104.95 

78 

22 

94.86 

116.20 

28 

72 

85.86 

105.18 

77 

23 

95.04 

116.42 

27 

73 

86.04 

105.40 

76 

24 

95.22 

116.65 

26 

74 

86.22 

105.62 

75 

25 

95.41 

116.88 

25 

75 

86.41 

105.85 

74 

26 

95.59 

117.10 

24 

76 

86.59 

106.07 

73 

27 

95.78 

117.33 

23 

77 

86.78 

106.30 

72 

28 

95.96 

117.55 

22 

78 

86.96 

106.53 

71 

29 

96.14 

117.77 

21 

79 

87.14 

106.75 

70 

30 

96.33 

118.00 

20 

80 

87.33 

106.98 

69 

31 

96.51 

118.22 

19 

81 

87.51 

107.20 

68 

32 

96.69 

118.45 

18 

82 

87.69 

107.42 

67 

33 

96.88 

118.68 

17 

83 

87.88 

107.65 

66 

34 

97.06 

118.90 

16 

84 

88.06 

107.87 

65 

35 

97.25 

119.13 

15 

85 

88.24 

108.10 

64 

36 

97.43 

119.35 

14 

86 

88.43 

108.33 

63 

37 

97.61 

119.57 

13 

87 

88.61 

108.55 

62 

38 

97.80 

119.80 

12 

88 

88.80 

108.78 

61 

39 

97.98 

120.03 

11 

89 

88.98 

109.00 

60 

40 

98.16 

120.25 

10 

90 

89.16 

109.22 

59 

41 

98.35 

120.48 

9 

91 

89.35 

109.45 

58 

42 

98.53 

120.70 

8 

92 

89.53 

109.67 

57 

43 

98.71 

120.92 

7 

93 

89.71 

109.90 

56 

44 

98.90 

121.15 

6 

94 

89.90 

110.13 

55 

45 

99.08 

121.37 

5 

95 

90.08 

110.35 

54 

46 

99.27 

121.60 

4 

96 

90.27 

110.58 

53 

47 

99.45 

121.83 

3 

97 

90.45 

110.80 

52 

48 

99.63 

122.05 

2 

98 

90.63 

111.02 

51 

49 

99.82 

122.28 

1 

99 

100.00 

122.50 

0 

100 

Compiled  from  the  table  by  H.  B.  Bishop,  Van  Nostrand's  Chemical  Annual,  1913. 


796 


TABLES  AND   USEFUL  DATA 
XII.— ACETIC  ACID  AT  15° 

OUDEMANS 


Specific 
Gravity. 

IS- 
IS 

Specific 
Gravity. 

1°: 

oW 
S30- 

ftB 

Specific 
Gravity. 

oW 

is0" 

z.~ 

Specific 
Gravity. 

1°- 
o« 

ti<* 

£w 

0.9992 

0 

1.0363 

26 

1.0623 

51 

.0747 

70 

1.0007 

1 

1.0375 

27 

1.0631 

52 

.0748 

77 

1  .0022 

2 

1.0388 

28 

1.0638 

53 

.0748 

78 

1.0037 

3 

1.0400 

29 

1.0646 

54 

.0748 

79 

1.0052 

4 

1.0412 

30 

1.0653 

55 

.0748 

80 

1.0067 

5 

1.0424 

31 

1.0660 

56 

.0747 

81 

1.0083 

6 

1  .0436 

32 

1.0666 

57 

.0746 

82 

1.0098 

7 

1.0447 

33 

1.0673 

58 

.0744 

83 

.0113 

8 

1.0459 

34 

1.0679 

59 

1.0742 

84 

.0127 

9 

1.0470 

35 

1.0685 

60 

1.0739 

85 

.0142 

10 

1.0481 

36 

.0691 

61 

1.0736 

86 

.0157 

11 

1.0492 

37 

.0697 

62 

1.0731 

87 

.0171 

12 

1.0502 

38 

.0702 

63 

1  .0726 

88 

.0185 

13 

1.0513 

39 

.0707 

64 

1.0720 

89 

.0200 

14 

1.0523 

40 

.0712 

65 

1.0713 

90 

.0214 

15 

1.0533 

41 

.0717 

66 

1.0705 

91 

1.0228 

16 

1  .0543 

42 

.0721 

67 

1.0696 

92 

1  .0242 

17 

1.0552 

43 

1.0725 

68 

1.0686 

93 

1.0256 

18 

1.0562 

44 

1.0729 

69 

.0674 

94 

1.0270 

19 

1.0571 

45 

1.0733 

70 

.0660 

95 

1.0284 

20 

1.0580 

46 

1  .0737 

71 

.0644 

96 

1.0298 

21 

1.0589 

47 

1.0740 

72 

.0625 

97 

1.0311 

22 

1.0598 

48 

1.0742 

73 

.0604 

98 

1.0324 

23 

1.0607 

49 

1.0744 

74 

.0580 

99 

1.0337 

24 

1.0615 

50 

1.0746 

75 

.0553 

100 

1  .0350 

25 

XIII.— MELTING   POINTS   OF  ACETIC    ACID 
RUDORFF,  Ber.  3,  390. 


ioo  gr. 
H.C2Ha02 
mixed  with 
gr.  water. 

ioo  parts 
by  weight  con- 
tain parts 
water. 

Melting  (solidi- 
fying) point 
°C. 

ioo  gr. 
H.C2H3O2 
mixed  with 
gr.  water. 

ioo  parts 
by  weight  con- 
tain parts 
water. 

Melting 
(solidifying) 
point  °C. 

0.0 

0.0 

16.7° 

8.0 

7.407 

6.25° 

0.5 

0.497 

15.65 

9.0 

8.257 

5.3 

1.0 

0.990 

14.8 

10.0 

9.090 

4.3 

1.5 

1.477 

14.0 

11.0 

9.910 

3.6 

2.0 

1.961 

13.25 

12.0 

10.774 

2.7 

3.0 

2.912 

11.95 

15.0 

13.043 

-0.2 

4.0 

3.846 

10.5 

18.0 

15.324 

-2.6 

6.0 

4.761 

9.4 

21.0 

17.355 

-5.1 

6.0 

5.660 

8.2 

24.0 

19.354 

-7.4 

7.0 

6.542 

7.1 

Boiling  point  100%  acid  117  8°. 


TABLES    AND   USEFUL  DATA 


797 


XIV.— AQUA  AMMONIA 
ACCORDING  TO  W.  C.  FERGUSON 


Degrees 
Baume. 

Sp.  Gr. 

*?¥. 
60° 

Per  Cent 
NH3. 

Degrees 
Baume. 

Sp.  Gr. 

*£F. 

60° 

Per  Cent 
NH3. 

Degrees 
Baume. 

Sp.  Gr. 

*°F. 
60° 

Per  Cent 
NHu 

10.00 

1.0000 

.00 

16.50 

.9556 

11.18 

23.00 

.9150 

23.52 

10.25 

.9982 

.40 

16.75 

.9540 

11.64 

23.25 

.9135 

24.01 

10.50 

.9964 

.80 

17.00 

.9524 

12.10 

23.50 

.9121 

24.50 

10.75 

.9947 

1.21 

17.25 

.9508 

12.56 

23.75 

.9106 

24.99 

11.00 

.9929 

1.62 

17.50 

.9492 

13.02 

24.00 

.9091 

25.48 

11.25 

.9912 

2.04 

17.75 

.9475 

13.49 

24.25 

.9076 

25.97 

11.50 

.9894 

2.46 

18.00 

.9459 

13.96 

24.50 

.9061 

26.46 

11.75 

.9876 

2.88 

18.25 

.9444 

14.43 

24.75 

.9047 

26.95 

12.00 

.9859 

3.30 

18.50 

.9428 

14.90 

25.00 

.9032 

27.44 

12.25 

.9842 

3.73 

18.75 

.9412 

15.37 

25.25 

.9018 

27.93 

12.50 

.9825 

4.16 

19.00 

.9396 

15.84 

25.50 

.9003 

28.42 

12.75 

.9807 

4.59 

19.25 

.9380 

16.32 

25.75 

.8989 

28.91 

13.00 

.9790 

5.02 

19.50 

.9365 

16.80 

26.00 

.8974 

29.40 

13.25 

.9773 

5.45 

19.75 

.9349 

17.28 

26.25 

.8960 

29.89 

13.50 

.9756 

5.88 

20.00 

.9333 

17.76 

26.50 

.8946 

30.38 

13.75 

.9739 

6.31 

20.25 

.9318 

18.24 

26.75 

.8931 

30.87 

14.00 

.9722 

6.74 

20.50 

.9302 

18.72 

27.00 

.8917 

31.36 

14.25 

.9705 

7.17 

20.75 

.9287 

19.20 

27.25 

.8903 

31.85 

14.50 

.9689 

7.61 

21.00 

.9272 

19.68 

27.50 

.8889 

32.34 

14.75 

.9672 

8.05 

21.25 

.9256 

20.16 

27.75 

.8875 

32.83 

15.00 

.9655 

8.49 

21.50 

.9241 

20.64 

28.00 

.8861 

33.32 

15.25 

.9639 

8.93 

21.75 

.9226 

21.12 

28.25 

.8847 

33.81 

15.50 

.9622 

9.38 

22.00 

.9211 

21.60 

28.50 

.8833 

34.30 

15.75 

.9605 

9.83 

22.25 

.9195 

22.08 

28.75 

.8819 

34.79 

16.00 

.9589 

10.28 

22.50 

.9180 

22.56 

29.00 

.8805 

35.28 

16.25 

.9573 

10.73 

22.75 

.9165 

23.04 

ALLOWANCE  FOR  TEMPERATURE 

The  coefficient  of  expansion  for    ammonia    solutions,  varying  with 
temperature,  correction  must  be  applied  according  to  the  following  table: 


the 


Corrections  to  be  Added  for  Each 
Degree  Below  60°  F. 

Corrections  to  be  Subtracted  for  Each  Degree 
Above  60°  F. 

Degrees 
Baume. 

40°  F. 

50°  F. 

70°  F. 

80°  F. 

90°  F. 

100°  F. 

14°  B6 

.015°  Be" 

.017°  Be" 

.020°  Be" 

.022°  B6 

.024°  Be 

.026°  B6 

16° 

.021      " 

.023     " 

.026     " 

.028     " 

.030     " 

.032      " 

18° 

.027     " 

.029     " 

.031      " 

.033     " 

.035     " 

.037      " 

20° 

.033     " 

.036     " 

.037     " 

.038     " 

.040     " 

.042      " 

22° 

.039      " 

.042     " 

.043     " 

.045     " 

.047     " 

26° 

.053     " 

.057     " 

.057      " 

.059      " 

798 


TABLES   AND   USEFUL   DATA 


XV.— SODIUM   HYDROXIDE  SOLUTION  AT  15° 
LUNGE 


Specific 

Degrees 
Bdume. 

Degrees 

Twadrfpll 

Per  Cent 
Nfl  O 

Per  Cent 

NaOW 

i  Liter  c 
Grai 

ontains 
ns 

Grfl.vi.ty. 

i.  Wauoeii. 

lie^vs. 

RMXtt. 

Na2O. 

NaOH. 

1.007 

1.0 

1.4 

0.47 

0.61 

4 

6 

1.014 

2.0 

2.8 

0.93 

1.20 

9 

12 

1.022 

3.1 

4.4 

1.55 

2.00 

16 

21 

1.029 

4.1 

5.8 

2.10 

2.70 

22 

28 

1.036 

5.1 

7.2 

2.60 

3.35 

27 

35 

1.045 

6.2 

9.0 

3.10 

4.00 

32 

42 

1.052 

7.2 

10.4 

3.60 

4.64 

38 

49 

1.060 

8.2 

12.0 

4.10 

5.29 

43 

56 

1.067 

9.1 

13.4 

4.55 

5.87 

49 

63 

1.075 

10.1 

15.0 

5.08 

6.55 

55 

70 

1.083 

11. 

16.6 

5.67 

7.31 

61 

79 

1.091 

12. 

18.2 

6.20 

8.00 

68 

87 

1.100 

13.2 

20.0 

6.73 

8.68 

74 

95 

1.108 

14. 

21.6 

7.30 

9.42 

81 

104 

1.116 

15. 

23.2 

7.80 

10.06 

87 

112 

1.125 

16. 

25.0 

8.50 

10.97 

96 

123 

1.134 

17. 

26.8 

9.18 

11.84 

104 

134 

1.142 

18.0 

28.4 

9.80 

12.64 

112 

144 

1.152 

19.1 

30.4 

10.50 

13.55 

121 

156 

1.162 

20.2 

32.4 

11.14 

14.37 

129 

167 

1.171 

21.2 

34.2 

11.73 

15.13 

137 

177 

1.180 

22.1 

36.0 

12.33 

15.91 

146 

188 

1.190 

23.1 

38.0 

13.00 

16.77 

155 

200 

1.200 

24.2 

40.0 

13.70 

17.67 

164 

212 

1.210 

25.2 

42.0 

14.40 

18.58 

174 

225 

1.220 

26.1 

44.0 

15.18 

19.58 

185 

239 

1.231 

27.2 

46.2 

15.96 

20.59 

196 

253 

1.241 

28.2 

48.2 

16.76 

21.42 

208 

266 

1.252 

29.2 

50.4 

17.55 

22.64 

220 

283 

1.263 

30.2 

52.6 

18.35 

23.67 

232 

299 

1.274 

31.2 

54.8 

19.23 

24.81 

245 

316 

1.285 

32.2 

57.0 

20.00 

25.80 

257 

332 

1.297 

33.2 

59.4 

20.80 

26.83 

270 

348 

1.308 

34.1 

61.6 

21.55 

27.80 

282 

364 

1.320 

35.2 

64.0 

22.35 

28.83 

295 

381 

1.332 

36.1 

66.4 

23.20 

29.93 

309 

399 

1.345 

37.2 

69.0 

24.20 

31.22 

326 

420 

TABLES   AND  USEFUL  DATA  799 

XV.— SODIUM  HYDROXIDE  SOLUTION  AT  15°   (Continued) 


i  Liter  contains 

Gr&ms 

Specific 
Gravity. 

Degrees 
Baume. 

Degrees 
Twaddell. 

Per  Cent 
Na2O. 

Per  Cent 
NaOH. 

Na2O. 

NaOH. 

.357 

38.1 

71.4 

25.17 

32.47 

342 

441 

.370 

39.2 

74.0 

26.12 

33.69 

359 

462 

.383 

40.2 

76.6 

27.10 

34.96 

375 

483 

.397 

41.2 

79.4 

28.10 

36.25 

392 

506 

.410 

42.2 

82.0 

29.05 

37.47 

410 

528 

.424 

43.2 

84.8 

30.08 

38.80 

428 

553 

.438 

44.2 

87.6 

31.00 

39.99 

446 

575 

.453 

45.2 

90.6 

32.10 

41.41 

466 

602 

.468 

46.2 

93.6 

33.20 

42.83 

487 

629 

1.483 

47.2 

96.6 

34.40 

44.38 

510 

658 

1.498 

48.2 

99.6 

35.70 

46.15 

535 

691 

1.514 

49.2 

102.8 

36.90 

47.60 

559 

721 

1.530 

50.2 

106.0 

38.00 

49.02 

581 

750 

800 


TABLES  AND  USEFUL  DATA 


XVI.— VAPOR  TENSION  OF  WATER  IN  MILLIMETERS  OF  MERCURY 

-2°   TO    -f36°C. 

ACCORDING  TO  REGNAULT,  BROCH,  AND  WEIBB 


°c. 

0 

.1 

.2 

.3 

.4 

.5 

.6 

.7 

.8 

.9 

-2 

mm. 
3.958 

mm. 
3.929 

mm. 
3.900 

mm. 
3.872 

mm. 
3.844 

mm. 
3.815 

mm, 

3.787 

mm. 
3.760 

mm. 
3.732 

mm. 
3.705 

-1 

4.258 

4.227 

4.197 

4.166 

4.136 

4.106 

4.076 

4.046 

4.016 

3.987 

-0 

4.579 

4.546 

4.513 

4.481 

4.448 

4.416 

4.384 

4.352 

4.321 

4.289 

0 

4.579 

4.612 

4.646 

4.679 

4.713 

4.747 

4.782 

4.816 

4.851 

4.886 

1 

4.921 

4.957 

4.992 

5.028 

5.064 

5.101 

5.137 

5.174 

5.211 

5.248 

2 

5.286 

5.324 

5.362 

5.400 

5.438 

5.477 

5.516 

5.555 

5.595 

5.635 

3 

5.675 

5.715 

5.755 

5.796 

5.837 

5.878 

5.920 

5.961 

6.003 

6.046 

4 

6.088 

6.131 

6.174 

6.217 

6.261 

6.305 

6.349 

6.393 

6.438 

6.483 

5 

6.528 

6.574 

6.620 

6.666 

6.712 

6.759 

6.806 

6.853 

6.901 

6.949 

6 

6.997 

7.045 

7.094 

7.143 

7.192 

7.242 

7.292 

7.342 

7.392 

7.443 

7 

7.494 

7.546 

7.598 

7.650 

7.702 

7.755 

7.808 

7.861 

7.914 

7.968 

8 

8.023 

8.077 

8.132 

8.187 

8.243 

8.299 

8.355 

8.412 

8.469 

8.526 

9 

8.584 

8.642 

8.700 

8.759 

8.818 

8.877 

8.937 

8.997 

9.057 

9.118 

10 

9.179 

9.240 

9.302 

9.364 

9.427 

9.490 

9.553 

9.616 

9.680 

9.745 

11 

9.810 

9.875 

9.940 

10.006 

10.072 

10.139 

10.206 

10.274 

10.342 

10.410 

12 

10.479 

10.548 

10.617 

10.687 

10.757 

10.828 

10.899 

10.970 

11.042 

11.114 

13 

11.187 

11.260 

11.333 

11.407 

11.481 

11.556 

11.631 

11.706 

11.782 

11.859 

14 

11.936 

12.013 

12.091 

12.169 

12.247 

12.326 

12.406 

12.486 

12.566 

12.647 

15 

12.728 

12.810 

12.892 

12.974 

13.057 

13.141 

13.225 

13.309 

13.394 

13.480 

16 

13.565 

13.651 

13.738 

13.825 

13.913 

14.001 

14.090 

14.179 

14.269 

14.359 

17 

14.450 

14.541 

14.632 

14.724 

14.817 

14.910 

15.003 

15.097 

15.192 

15.287 

18 

15.383 

15.479 

15.575 

15.672 

15.770 

15.868 

15.967 

16.066 

16.166 

16.266 

19 

16.367 

16.469 

16.571 

16.673 

16.776 

16.880 

16.984 

17.088 

17.193 

17.299 

20 

17.406 

17.513 

17.620 

17.728 

17.837 

17.947 

18.057 

18.167 

18.278 

18.390 

21 

18.503 

18.616 

18.729 

18.844 

18.959 

19.074 

19.190 

19.307 

19.424 

19.542 

22 

19.661 

19.780 

19.900 

20.021 

20.142 

20.264 

20.386 

20.510 

20.634 

20.758 

23 

20.883 

21.010 

21.137 

21.264 

21.393 

21.522 

21.652 

21.782 

21.913 

22.045 

24 

22.178 

22.311 

22.446 

22.581 

22.716 

22.853 

22.990 

23.128 

23.266 

23.406 

25 

23.546 

23.686 

23.828 

23.970 

24.113 

24.257 

24.401 

24.547 

24.693 

24.839 

26 

24.987 

25.135 

25.284 

25.434 

25.584 

25.736 

25.888 

26.041 

26.195 

26.349 

27 

26.505 

26.661 

26.818 

26.976 

27.134 

27.294 

27.454 

27.615 

27.777 

27.939 

28 

28.103 

28.267 

28.432 

28.599 

28.766 

28.933 

29.102 

29.271 

29.442 

29.613 

29 

29.785 

29.958 

30.132 

30.307 

30.482 

30.659 

30.836 

31.015 

31.194 

31.374 

30 

31.555 

31.737 

31.919 

32.103 

32.288 

32.473 

32.660 

32.847 

33.036 

33.225 

31 

33.416 

33.607 

33.799 

33.992 

34.187 

34.382 

34.578 

34.775 

34.973 

35.172 

32 

35.372 

35.573 

35.775 

35.978 

36.182 

36.387 

36.593 

36.800 

37.008 

37.217 

33 

37.427 

37.638 

37.851 

38.064 

38.278 

38.493 

38.710 

38.927 

39.146 

39.365 

34 

39.586 

39.807 

40.030 

40.254 

40.479 

40.705 

40.933 

41.161 

41.390 

41.621 

35 

41.583 

42.085 

42.319 

42.554 

42.791 

43.028 

43.266 

43.506 

43.747 

43.989 

TABLES   AND  USEFUL  DATA 


801 


XVII.— USEFUL  DATA  OF  THE  MORE  IMPORTANT  INORGANIC 

COMPOUNDS  * 


Substance. 

Formula. 

Molecular 
or  Atomic 
Weight. 

Normal 
Coefficient 
1  c.c.  =  gm. 

Solubility 
in  100  Gms. 
Water. 

Indi- 
cator. 

Acetic  acid 

HC2H3O2 

60  03 

06003 

Aluminium 

Al 

27  10 

009033 

chloride 

A12C16 

266  96 

04449 

69  8715° 

P. 

chloride 

A12C16-12H2O 

483  15 

08053 

40 

P. 

oxide 

A12O3 

102  20 

01703 

insol. 

sulphate. 

A12(SO4)3 

342  38 

05706 

36  120° 

P. 

sulphate. 

A12(SO4)318H2O 

666  67 

11111 

87 

P. 

Ammonia  

NH3 

17  03 

01703 

M. 

Ammonium  

NH4 

18.04 

.01804 

M. 

chloride  

NH4C1 

53.50 

.  05350 

29.  4°° 

M. 

hydroxide  

NH4OH 

35.05 

.  03505 

M. 

nitrate  

NH4NO3 

80.05 

.08005 

118°° 

M. 

sulphate. 

(NH4)2SO4 

132  14 

06607 

71°° 

M. 

Antimony 

Sb 

120  20 

06010 

Arsenic. 

As 

74  96 

03748 

oxide 

As2O5 

229  92 

03832  l 

150 

Arsenous  oxide 

As2O3 

197.92 

03299 

1  716° 

Arsenious  oxide      .  . 

As2O3 

197.92 

04948  3 

1  7150 

Barium    

Ba 

137.37 

.  068685 

carbonate  

BaC03 

197.37 

.  098685 

.0022200 

M. 

chloride  

BaCl2 

208.29 

.  104145 

30.  9°° 

chloride  

BaCl22H2O 

244.32 

.12216 

36.  2°° 

hydroxide  

Ba(OH)2 

171.38 

.08569 

hydroxide 

Ba(OH)28H2O 

315  51 

15775 

5  5615° 

sulphate 

BaSO4 

233  44 

11672 

000172°° 

oxide 

BaO 

153  37 

076685 

1  5°° 

peroxide  

BaO2 

169.37 

.08469 

insol. 

Bromine.  

Br 

79.92 

.07992 

4.1700 

Cadmium  carbonate  . 
chloride  
chloride  

CdCO3 
CdCl2 
CdCl22H2O 

172.40 
183.32 
219  35 

.08620 
.09166 
109675 

insol. 
14020° 
16820° 

sulphide  

CdS 

144  47 

072235 

insol. 

Calcium  

Ca 

40  00 

.  020035 

carbonate 

CaCO3 

100  07 

050035 

0013 

M 

chloride  

CaCl2 

110.99 

.  055495 

59.  5°° 

chloride 

CaCl26H2O 

219  086 

109543 

117  4°° 

hydroxide  . 

Ca(OH)2 

74  09 

037045 

17°° 

oxide    

CaO 

56  07 

028035 

13°° 

sulphate  

CaSO4 

136  14 

06807 

1790° 

sulphide  

CaS 

72  14 

03607 

15100 

Carbon  

c 

12  005 

003002 

insol. 

dioxide 

CO2 

44  005 

022003  x 

179  67  cc  9° 

dioxide 

CO2 

44  005 

044005  2 

(  t 

p 

Chlorine 

Cl 

35  46 

03546 

150  cc  °° 

Chromic  anhydride  .  . 
oxide 

Cr03 
Cr2O3 

100.00 
152  00 

.  033333  3 
025333  3 

163.  4°° 
insol 

Citric  acid. 

H3C6H5O7 

192  06 

06402 

133 

Cobalt 

Co 

58  97 

029485 

Copper. 

Cu 

63  57 

031785 

oxide    .  .        .... 

CuO 

79  57 

07957 

sulphate  

CuSO4 

159  63 

15963 

20°  ° 

sulphate  

CuSO45H2O 

249.71 

.24971 

31  61°° 

CuS 

95.63 

.  047815 

000033 

1  Precipitation  reagents.  2  Acids  and  bases.  8  Oxidizing  and  reducing  agents. 

M.  Methyl  orange.  P.  Phenolphthalein.  Temp.  C. 

*  Compiled  and  arranged  by  R.  M.  Meiklejohn. 


802 


TABLES  AND  USEFUL  DATA 


XVII.— USEFUL  DATA  OF  THE  MORE  IMPORTANT  INORGANIC 
COMPOUNDS  (Continued) 


Substance. 

Formula. 

Molecular 
or  Atomic 
Weight. 

Normal 
Coefficient 
1  c.c.  =  gm. 

Solubility 
in  100  Cms. 
Water. 

Indi- 
cator. 

Cyanogen            .  . 

CN 

26.005 

.  026005 

Ferric  oxide. 

Fe2O3 

159.68 

.  07984  3 

Ferrous  oxide  

FeO 

71.84 

.07184  3 

insol. 

sulphate  
sulphate  

FeSO4 
FeSO47H2O 

151.90 
278.01 

.  15190  3 
.27801  3 

32  8°° 

ammon'm  sulphate 
Hydrobromic  acid  .  .  . 
Hydrochloric  acid  .  .  . 
Hydrocyanic  acid.  .  .  . 
Hydrofluoric  acid.  .  .  . 
Hydroiodic  acid  .  . 

FeS04(NH4)2S046H20 
HBr 
HC1 
HCN 
HF 
HI 

392.14 
80.928 
36.47 
27.02 
20.01 
127.93 

.39214 
.08093 
.03647 
.02702 
.02001 
.  12793 

18°° 
221.  2°° 

82.5100 

264 

Hydrogen  peroxide  .  . 
Hydrogen  sulphide  .  . 
Iodine  

H202 
H2S 

34.016 
34.076 
126.92 

.017008 
.017038 
.  12692 

437  cc.°° 
.0182110 

Iron   »  

Fe 

55.84 

.05584 

Lead  

Pb 

207.20 

.  10360 

carbonate  

PbC03 

267.20 

.  13360 

.00198 

M. 

chromate  

PbCrO4 

323.20 

.  16160 

.  00002"° 

oxide      

PbO 

223.20 

.11160 

peroxide  

PbO2 

239.20 

.11960 

sulphide  

PbS 

239.26 

.11963 

.0001 

Magnesium  

Mg 

24.32 

.01216 

carbonate 

MgCO3           

84.32 

.04216 

.0106 

M. 

chloride  

MgCl2 

95.24 

.04762 

52.  2°° 

M. 

chloride  

MgCl26H2O 

203.34 

.10167 

167 

M. 

oxide  

MgO 

40.32 

.02016 

.00062 

M. 

sulphate  

MgSO4 

120.38 

.06019 

26.  9°° 

M. 

sulphate  

MgSO47H2O 

246.49 

.  123245 

76.  9°° 

M. 

Malic  acid  

H2C4H4O6 

134.06 

.06703 

Manganese  

Mn 

54.93 

.027465 

chloride 

MnCl2  

125.85 

.062925 

62.16100 

peroxide  

MnO2 

86.93 

.043465 

insol. 

sulphate 

MnSO4  

150.99 

.075495 

53.  2°° 

Mercuric  chloride.  .  .  . 
Nickel 

HgCl2 

Ni 

271.52 
58.68 

.13576 
.02934 

5.73°° 

Nitric  acid 

HNO3  

63.02 

.  06302  2 

Nitric  acid 

HNO3 

63.02 

.  021006  3 

Nitrogen  trioxide.  .  .  . 
pentoxide. 

N203 
N2O6 

76.02 
108.02 

.  019005  3 
.05401  2 

pentoxide.   .  .    . 

N2O5 

108.02 

.  018033  3 

Nitrous  acid  .  . 

HNO2 

47.02 

.04702 

Nitrogen  

N 

14.01 

.01401 

Oxalic  acid  .... 

H2C2O4 

90.02 

.04501 

Oxalic  acid  
Phosphoric  acid    .    . 

H-AO^HaO 
H3PO4 

126.05 
98.06 

.063025 
.  09806  2 

4.9°° 
v.  sol. 

M. 

Phosphoric  acid  
Phosphoric  acid  
potassium 

H3P04 
H.PO. 

98.06 
98.06 
39.10 

.  04903  2 
.03268 
.03910 

v.  sol. 
v.  sol. 

P. 

bicarbonate.  . 

K2CO3 

100.11 

.10011 

22.  4°° 

M. 

bitartrate  
bromide  

KHC4H4Oa 
KBr 

188.14 
119.02 

.18814 
.11902 

.37°° 
53.  48°° 

P. 

carbonate 

K2CO$ 

138  20 

.06910 

89.  4°° 

chlorate 

KC1O3. 

122  .  56 

.  020427  3 

3.3°° 

M. 

» Precipitation  reagents.  J  Acida  and  bases.  8  Oxidizing  and  reducing  agents. 

M.  Methyl  orange.  P.  Phenolphthalein.  Temp.  C. 


TABLES   AND   USEFUL  DATA 


803 


XVII— USEFUL  DATA  OF  THE  MORE  IMPORTANT  INORGANIC 
COMPOUNDS  (Continued) 


Substance. 

Formula. 

Molecular 
or  Atomic 
Weight. 

Normal 
Coefficient 
1  c.c.  =  gm 

Solubility 
in  100  Cms. 
Water. 

Indi- 
cator. 

Potassium  chloride  . 
chromate 

KC1 
K2CrO4 

74.56 
194.20 

.07456 
.  06473  3 

28.  5°° 
61.  5°° 

cyanide  
dichromate  
dichromate  
f  erro  cyanide 

KCN 

K2Cr2O7 
K2Cr2O7 

K4Fe(CN)6 

65.11 
294.20 
294.20 
368.30 

.06511  l 
.  14710  2 
.04903  3 
.36830 

v.  sol. 
4.9°° 
4.9°° 

P. 

f  errocyanide  
hydroxide  

K4Fe(CN)63H2O 
KOH 

422.35 
56.11 

.42235 
.05611 

27.812° 
107150 

iodate  

KIO3 

214.02 

.03567 

4.7400 

iodide  

KI 

166.03 

.  16603 

126.  1°° 

nitrate  

KNO3 

101.11 

.033703 

13.  3°° 

nitrite  

KNO2 

85.11 

.08511 

3QQ15-50 

oxide  

K2O 

94.20 

.04710 

v.  sol. 

permanganate 

KMnO4 

158  03 

.031606 

2.83°° 

sulphide  
sulphocyanate  
tartrate  
Silver 

K2S 
KCNS 
K2H4C406 
Ag 

110.26 
97.18 
226.23 

107.88 

.05513 
.09718 
.11312 

.  10788 

EOl, 

177.  2°° 
sol. 

nitrate 

AgNO3 

169.89 

.  16989 

122°° 

Sodium 

Na 

23.00 

.02300 

bromide  
bicarbonate. 

NaBr 
NaHCO3 

102.92 
84.01 

.  10292 
.08401 

79.  5°° 
6.90°° 

M. 

carbonate 

Na2CO3 

106  .  00 

.05300 

7.1°° 

M. 

chloride  
cyanide                  .  . 

NaCl 

NaCN 

58.46 
49.01 

.05846 
.04901 

35.  7°° 
sol. 

hydroxide 

NaOH 

40.01 

.04001 

133.3180 

iodide.            .        .  . 

Nal 

149.92 

.  14992  i 

158.  7°° 

nitrate  
nitrite.               .  .  . 

NaNO3 
NaNO2 

85.01 
69.01 

.02834 
.06901 

72.  9°° 
83.3200 

oxalate.            .    .  . 

Na2C2O4 

134.00 

.06700 

3.2215'50 

oxide    .  . 

Na2O 

62.00 

.03100 

decomp. 

phosphate  (mono)  . 
phosphate  (disod) 

NaH2PO4 
Na2HPO4 

120.06  2 
142  05  2 

.  12006 
14205 

v.  sol. 

M. 
p 

phosphate  (disod)  . 
phosphate  (trisod)  . 

Na2HPO412H2O 
Na3PO4 

358.  24  2 
164.  04  2 

.35824 
.  16404 

6.3°° 

P. 
M. 

sulphide  

Na2S 

78.06 

.03903 

15.4100 

thiosulphate  
Stannous  chloride  .  .  . 
chloride  
oxide                .... 

Na2S2O35H2O 
SnCl2 

SnCl22H2O 
SnO 

248.20 
189.62 
225.65 
134.70 

.24820 
.09481 
.112825 
.  06735 

74.  7°° 
83.  9°° 
118.  7°° 
insol. 

Sulphur  dioxide  
trioxide  

SO2 
SO3 

64.06 
80.06 

.03203 
.04003 

7979  cc.°° 

Sulphuric  acid  
Tartaric  acid  
Tin  

H2S04 
H2C4H406 

Sn 

98.076 
150.05 
118.70 

.049038 
.075025 
.05935 

115°° 

Zinc  

Zn 

65.37 

.037685 

carbonate  

ZnCO3 

125.37 

.062685 

00115° 

chloride  

ZnCl2 

136.29 

.068145 

209°° 

oxide 

ZnO 

81.37 

.  040685 

001 

sulphate  
sulphate  

ZnSO4 
ZnSO47HoO 

161.43 

287.54 

.080715 
.  14377 

43.02°° 
115  2°° 

sulphide 

ZnS 

97  43 

048715 

00069 

1  Precipitation  reagents.  2Acids  and  bases.  3  Oxidizing  and  reducing  agents. 

M.  Methyl  orange.  P.  Phenolphthalein.  Temp  C. 


804 


TABLES   AND   USEFUL   DATA 
XVIII.— CONVERSION  FACTORS  * 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

Ag  

Ag  
As 

AgBr  
AgCl  
AgCN      . 

1.7408 
1.3287 
1.2411 
2.1765 
1  .  5748 
1.0742 
1.2935 
1.4030 
0.2316 
0.7408 
0.7505 
0.3287 
0.3380 
1  .  1859 
1  .  1765 
1  .  1033 
0.6911 
1  .  1361 
1.2844 
0.6035 
1  .  5390 
0.9562 
0.5419 
1.3897 
0.4256 
0.6811 
0.4311 
0.6337 
0.8893 
0.5480 
0.7526 
1.1852 
0.2474 
0.2545 
0.5202 
0.8550 
0.4078 
0.3732 
0.4863 
0.2020 
0.6175 
0.5448 
0.5406 
0.7450 
0.8131 
0.7109 
0.7071 
0.9115 
0.6385 
0.3055 
0.3709 
0.3441 
0.2470 

0.5744 
0.7526 
0.8057 
0.4595 
0.6350 
0.9310 
0.7731 
0.7126 
4.3175 
1.3489 
1.3324 
3.0423 
2.9590 
0.8433 
0.8500 
0.9064 
1.4469 
0.8802 
0.7786 
1.6568 
0.6498 
1.0458 
1.8453 
0.7196 
2.3498 
1.4681 
2.3195 
1.5779 
1  .  1244 
1.8257 
1.3287 
0.8437 
4.0423 
3.9305 
1.9225 
1  .  1695 
2.4519 
2.6793 
2.0564 
4.9500 
1.6194 
1.8354 
1.8500 
1.3423 
1.2298 
1.4067 
1.4143 
1.0971 
1.5661 
3.2729 
2.6959 
2.9061 
4.0487 

A1C13 

Cl 

0.7970 
1  .  1023 
1  .  3925 
0  .  5303 
2.6121 
2.2336 
2.3902 
3.3504 
6.5235 

2.1088 
1.5625 
2  8792 

1.2547 
0.9072 
0.7182 
1.8856 
0.3828 
0.4482 
0.4184 
0.2985 
0.1533 

0.4742 
0  .  6400 
0.3473 

0.1077 
0.6224 

0.1127 
.04255 
4.5070 
2.3894 
1.7197 
1.6067 
1.7193 
0.7334 
1  .  1636 
0.6793 
1.4255 

A1C13   .  . 

H2SO4 

A1F3.  .  . 

CaF2  
Al 

•"•6  

Ac 

Agl  
AgNO3.  .  . 

A12O3  .  .  . 

A12O3  .  . 

A1C13 

Ac 

Ag2O  
Ag3P04  
Ag4P2O7 

A12O3   .  .  . 

A12P207  
A12P2OS  

Aucsol)!;;;; 

.  18H2O 
FeO  
Fe203  
H2SO4 

Ag. 

A12O3  
A12O3  

Ac 

Ac 

As. 

A12O3  

Ag. 

Br..  . 

A12O3  .  . 

Ac 

HBr 

Ac 

Cl 

A1203  
A12O3  

Ag  
Ac 

HC1 

HI  
I 

A12O3  

K2A12(S04)4 
•24H2O 
Na2Al204.... 
(NH4)2A12 
(SO4)4-24H2O 
(S03)3  
Al  .    . 

1.2863 
1.6067 

8.8742 
2.3504 
0.2219 
0.4185 
0.5815 
0.6224 
0.5816 
1.3635 
0.8594 
1.4721 
0.7015 

Ac 

A1203  
A12O3  

Ag  
Ac 

KBr  
KC1 

v^  
Ac.. 

KC103  
KC104  
KCN 

A1203  
A1PO4  

A 

Ac 

KI 

A1PO4  

Ac 

NaBr  
NaCl  
Nal  
Br 

A1PO4  

p  Q 

Ac 

A12P2O7  
A12P2O8  

P205  
P206 

Ag 

AgBr 

A12(S04)3.... 

Ai2(so4)3  .'!.': 

A12(S04)3.... 

BaSO4 

AgBr 

BrO3 

H2SO4.  .  .  . 
NaHCO3... 
303  

AgBr  

HBr  
KBr  
KBrO3  
NaBr  
Ag  
AgNO3. 

AgBr  
AirRr 

AgBr 

As.. 

Ag. 

4.3175 
1.3201 
1.5336 
1.6417 
3.3862 
2.4809 
1.1616 
1.2435 
1.5674 
2.5652 
1.4264 
1.6177 
2.2081 

0.2316 
0.7575 
0.6521 
0.6091 
0.2953 
0.4031 
0.8609 
0.8042 
0.6380 
0.3898 
0.7011 
0.6182 
0.4529 

AgCl  
AgCl  
AgCl 

As  
As  
As  
As  

As203  

AS205  

As2S3  
21 

Cl 

AgCl 

HC1 

AgCl. 

KC1 

As  

AgCl  
AgCl  
AgCl  
AgCN  

KC103  
NaCl.  
NH4C1     .  . 

As2O3  

AS^OO 

As2O3  

As2S3. 

As203  
As2O3  

As2S6  
41 

KCN  

AgCN  
AgL. 

HCN  

As2O0  
As2O5  
As2O6  

NaH2AsO4  .  . 
Na2HAsO4  . 
41  

NH4I  

AgL. 

HI  

Ael 

I 

Agl  
Agl  
Agl  
Agl  
Agl  
AirT 

I03  
I203  
I207  
KI  
KIO3  
NflT 

Au.  . 

AuCl3.  . 
HAuCl4 
•4H20 

KAu(CN)4 
•H2O 

1.5394 
2.0898 
1.8172 

0.6496 
0.4785 
0.5503 

Au  

Au  

AgN02  
AgNO,  
AgNOi  
AgN03  

HNO2.  . 

Ba  
Ba. 

Ba(C2H302)2  . 
BaCrO4  
BaSO4  
BaSO4 

1.8594 
1.8457 
1.7010 
1  1207 

0.5378 
0.5420 

)  .  5SS5 
0.8923 

HNO3  

NaCl  
N20,  

Ba  

BaCl2  

AXA'=B  and  BXB'= A. 
*  Compiled  and  arranged  by  W.  W.  Scott  and  B.  S.  Clark. 


TABLES  AND   USEFUL   DATA 

XVIII.— CONVERSION  FACTORS  (Continued) 


805 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

BaCl2  
BaCO3  
C(in  BaCO3) 
BaCrO4  
BaCrO4  
BaCrO4  
BaCrO4  
BaCrO4  
BaCrO4  
Ba(OH)2..  .. 

HoSO4.  . 
CO2  
H2SO4  
Ba  

0.4709 
0.2229 
8.1740 
0.5420 
0.9213 
0.2055 
0.3002 
0.7666 
0.5807 
0.5723 
0.8208 
0.4912 
0.6271 
0.5484 
0.4076 
0.4292 
0.5160 
0.3729 
0.2156 
0.7334 
0.5885 
0  8928 

2.1236 
4.4857 
0.1223 
1.8457 
1.0854 
4.8651 
3.3308 
1.3046 
1.7220 
1.7473 
1.2184 
2.0359 
1.5948 
1.8235 
2.4533 
2.3297 
1.9379 
2.6814 
4.6380 
1.3635 
1.7010 
1  .  1207 
0.9554 
1  .  1827 
0.9213 
0.8931 
.5219 
.3782 
1.1826 
.3778 
.9429 
1.7147 
2.6554 
6.8493 
2.8437 
2.3801 

0.9839 
1.7141 

5.7897 
0.9469 
1  .  5458 
2.2022 
2.2432 
3.7651 
2.9904 
1.8515 
2.9524 
1.6431 

0.7244 
1.7665 
0.7700 

7.2812 
3  .  6443 

BaSO4.  . 
BaSO4  
BaSO4   .  .  . 

SO,  
S04  

ZnS 

0.3430 
0.4115 
0.4174 
1.2318 

2.9155 
2.4301 
2.3957 
0.8118 

BaSO4  

ZnSO4-7H2O 

Cr.. 
Cr2O3  
K2CrO4  
K2Cr2O7 

Be  

SeeGl. 

Bi  

Bi2O3  
Bi 

1.1154 
0.5994 
0.8017 

1.8658 
0.8942 
1.1024 
0.8965 
1.2328 

2.0867 
0.8122 
0.9059 

0.8965 
1.6683 
1.2474 

0.5359 
1  .  1184 
0.9072 
1.1154 
0.8112 

0.4792 
1.2313 
1  .  1039 

BiAsO4 

H2SO4  
Ba 

BiOCl. 

Bi 

BiOCl. 

Bi(N03)3 
•5H2O 
Bi2O3 

BaSiFe  
BaSiFe 

Ba  
BaF2  

BiOCl.., 
BiOCl  
Bi2O3  
Bi203  
Bi2O3  

Bi2S3.  . 

BaSiFe  
BaSiFe 

BaO  

BiONO3  
Bi  
BiONO3  

Bi(N03)3 
•5H2O 
Bi 

F  

BaSiFe  
BaSiFe  
BaSiFe 

HF  

H2SiF6  

SiF4  

BaSiFe 

SiO2  
A12(SO4)3.  ... 
Ba  
Bad? 

BaSO4 

Bi2S3  

Bi2O3  

BaSO4  ... 
BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaS04  
BaSO4  
BaSO4...... 
BaSO4  
BaSO4  
BaSO4  
BaSO4 

B..  . 

KBF4 

11.464 
0.3143 
3.6029 
1.7721 

5.4594 
0.4919 

0.7576 

0.0872 
3.1819 
0.2775 
0.5643 

0.1832 
2.0331 

1.3199 

BaCl2-2H2O  . 
BaCO3  

1.0466 
0.8455 
1.0854 
1.1197 
0.6571 
0.7256 
0.8456 
0  7258 
0.5147 
0.5832 
0.3766 
0.1460 
0.3517 
0.4202 

1  0167 

0.5834 
0.1727 
1.0560 
0.6469 
0.4541 
0.4458 
0.2656 
0.3344 
0.5401 
0.3387 
0.6086 

1.3804 
0.5661 
1.2987 
0.1373 
0.2744 

B2O3  

B  

B2O3  
B2O3  

KBF4  
H3BO3  
Na2B4O7 
•  10H2O 
H3BO3  
Na2B4O7 
•  10H2O 

BaCrO4  
Ba(NO3)2.  .  .  . 
BaO  
BaO2  
Ba3(PO4)2.... 
BaS  

B2O3  

KBF4 

KBF4  

CaSO4.  . 
FeS 

Br..  , 

Ag 

1.3498 
2.3498 
1.0130 
0.1001 
0.8433 
1.4681 

0.7408 
0.4256 
0.9877 
9.9913 
1  .  1858 
0.6811 

Br  

AgBr 

BaSO4 

H2S 

Br  

HBr 

BaSO4  
BaSO4 

H,SO3  
H2SO4  

Br  

O  

BrO3  
BrOj 

Ag  
AgBr  

BaSO4  

BaS04  
BaSO4  

K2A12(SO4)4- 
24H2O 
KHSO4  
MgO  
MgSO4-7H2O 
MnSO4  

Ca.. 
Ca  
Ca  
Ca(CH3C02)2 
Ca(CH3CO2)2 
Ca(CH3CO2)2 
CaCl2  . 
CaCl2  
CaCl2  
CaCl2  
CaCO3  
CaCO3  
CaCO3  
CaCO3  
CaCO3  
CaCO3  
CaCO3  

CaCl2.. 
CaO  
C12  
CaO.. 
CH3CO2H... 
H2SO4  
CaCO3  
CaO  
CaS04  
C12  
Ca  
CaCl2  

2.7687 
1.3993 
1.7690 
0.3546 
0.7594 
0.6203 
0.9016 
0.5052 
1.2265 
0.6390 
0.4006 
1  .  1091 
1.6197 
0.5603 
0.4397 
1.3604 
1.7204 

0.3612 
0.7146 
0.5653 
2.8200 
1.3169 
1.6120 
1.1091 
1.9795 
0.8153 
1.5650 
2.4966 
0.9016 
0.6174 
1.7847 
2.2743 
0.7351 
0.5813 

BaSO4 

BaSO4 

BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaSO4  
BaSO4 

Na2CO3  

NaHSO3  
Na2O 

Na2S  
Na2SO3  
Na2S2O3  

Na2SO4  
Na2SO4- 
10H2O 
'NH4)2S04.  .  . 
PbSO4  
S  

BaS04  
BaSO4  

Ca(HCO3)2  .  . 
CaO  .  .  . 

CO2  
CaSO4  
CaSO4-2H2O. 

BaSO4  

BaS04  

S02  

AXA'=B  and  BXB'=A. 


806 


TABLES  AND   USEFUL  DATA 

XVIII.— CONVERSION  FACTORS  (Continued) 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

CaCO3 

Na2CO3.  . 

1.0593 

0.9441 

CaSO4.  . 

CaCl2  . 

0  8153 

1  2265 

CaCO3 

HC1  

0.7288 

1.3720 

CaSO4  

CaF2  

0  5735 

1  7438 

CaF> 

A1F3  

0.7182 

1.3925 

CaSO4.  . 

CaO  

0  4119 

2  4280 

CaF2 

Ca  

0.5128 

1.9501 

CaSO4.  . 

F  

0  2791 

3  5827 

CaF2 

CaSO4  

1.7438 

0.5735 

CaSO4.. 

HF  

0  2539 

3  4021 

CaF2    . 

F  

0.4867 

2.0545 

CaSO4  

H2SO4  

0  .  7205 

1  3875 

CaF^ 

HF  

0.5126 

1.9508 

CaSO4  

SO3  

0  .  5881 

1  7003 

CaF2 

H2SiF6  

1.8485 

0.5410 

CaSO4-2H2O 

CaO  

0.3257 

3  0707 

r^oi? 

"NFaT? 

1    07AO 

0  Q9Q4. 

L/ar2  
Ca(HCO3)2 

CaO 

0  3459 

2  8908 

Cb.  .  . 

Cb2O5 

1  4278 

0  7004 

P«  f  TTPO  ^ 

POo 

0  "vl2Q 

1    841  Q 

CaHPO4 

CaO 

0  4119 

2  4276 

Cd.  . 

CdO 

1  1426 

0  8754 

CaHPO4 

Ca2P2O7 

0  9338 

1  0709 

Cd  

CdS 

i  2853 

0  7780 

CaHPO4 

P2O5 

0  5219 

1  9161 

Cd  

CdSO4 

1  8547 

0  5392 

Ca(H»PO^» 

NaHCO3 

0  7175 

1  3938 

Cd  

S.     .  . 

0  2853 

3  5048 

CaTILPOd)* 

P2O5 

0  6067 

1  6483 

CdO  

CdS.    . 

1  1251 

0  8888 

CaH2P207  .  .  . 
CaH2P2O- 

Ca(H2P04)2  . 
CaO 

1.0827 
0  .  2594 

0.9236 
3  .  8553 

CdS  

CdS  

H2S  

S.  .  . 

0.2327 
0  2220 

4.2975 
4  5048 

pQTT   p  f\     * 

MaTTPO 

0  777*3 

1    9&fifi 

oauair^/7    .  . 
CaH2P2O7 

P2O5 

0  .  6573 

1.5214 

Ce..  , 

Ce(NO3)4.  .  . 

2  7685 

0  3612 

Ca  HSO3)2 

CaO  

0.2773 

3.6067 

Ce  

Ce2O3  

1.1711 

0.8539 

Ca  HSO3)2 

SO2 

0.6336 

1  .  5783 

Ce  

CeO2  

1  .  2282 

0  8142 

Ca  N03)2.  .  . 

N2O5  

0.6582 

1.5192 

Ce  

Ce(SO4)3.  .  .  . 

2.0275 

0.4932 

CaO 

Ca 

0.7146 

1  .  3993 

Ce2O3. 

CeO2  

1  .  0487 

0  9536 

f\,f) 

Pa  (PH,POo"U 

2  8200 

0  3546 

CaO 

CaCl2 

1  .  9795 

0.5052 

CH2ClCOoII  . 

Cl  

0.3753 

2  .  6645 

CaO 

CaCO3 

1.7847 

0  .  5603 

CH3CHOH 

CaO  

CaF2  

1.3924 

0.7182 

CO2K 

H2SO4.. 

0.5446 

1.8361 

CaO  

Ca(HCO3)2  .  . 

2.8908 

0.3459 

CH3CO2H.  .. 

Ca(CH3CO2)2 

1.3169 

).7594 

CaO  

Ca(H2PO4)2  . 

4.1766 

0.2394 

CH3CO2H... 

CH3CO2Na.. 

1.3663 

0.7319 

CaO  

CaH2P2O7  .  .  . 

3.8553 

0.2594 

CH3CO2H... 

(CH3CO)2O  . 

0.8499 

1  .  1766 

CaO  

Ca(HSO3)2.  .  . 

3.6067 

0.2773 

CN3CO2H.  .. 

H2SO4  

0.8169 

1.2241 

CaO 

Ca3P2O8 

1.8446 

0.5421 

CH3CO2H.  .  . 

Na2CO3  

0.8828 

1  .  1327 

CaO.  . 

CaSOa  

2.1427 

0.4667 

CH3CO2H... 

Na2O  

0.5164 

1.9365 

CaO 

CaS04 

2.4280 

0.4119 

CH3CO2H.  .  . 

Pb  

1.7249 

0.5797 

CaO 

CaSO4-2H2O 

3.0707 

0.3257 

CH3CO2Na.  . 

H2SO4  

0.5979 

1.6725 

CaO  
CaO 

CH3CO2H... 
CO2 

2.1413 

0  7874 

0.4670 
1  2743 

CH3CO2Na.  . 
CH3CO2Na  . 

Na,0  
Na2SO4  

0.3779 
0  8660 

2.6459 
1   1547 

CaO. 

II2SO4.   .  .  . 

1.7494 

0.5716 

(CH3CO)2O  . 

H2SO4  

0.9612 

1.0404 

CaO.    . 

NaCl   

2.0852 

0.4786 

C2H2O4  

H2SO4  

1.0897 

0.9177 

CaO.. 

Na2CO3  

1.8905 

0.5290 

C2H2O4-2H2O 

H2S04  

0.7782 

1.2851 

CaO.  .. 

NazSO4  

2.5338 

0.3947 

C4H6O6  

H2SO4  

0.6537 

1.5298 

CaO 

S 

0  5720 

1  7484 

C4H6O6  

NaHCO3  

1.1197 

0.8931 

CaO  

SO3  

1.4280 

0.7003 

C4H4O6HK... 

H2SO4  

0.2607 

3.8362 

Cn,«PoO 

PnO 

0  5421 

1  8446 

CajPjOg 

Mg2P2O7 

0.7178 

1.3932 

Cl.  . 

Ag... 

3.0423 

).3287 

Ca8P203  

(NH4)3P04- 
12MoO3 

!2  102 

0  0826 

Cl  
Cl           .    . 

AgCl  
AgNO3. 

4.0423 
4  7910 

0.2474 
0  2088 

CaiPoOa 

p,O6 

0  4579 

2  1839 

Cl       

A1C13     

1  2547 

0  7970 

CaS   

BaSO4  

3.2347 

0.3091 

Cl  

BaCrO4  

3.5741 

).2798 

CaSOj 

BaSO4 

1.9429 

0  5147 

Cl  

CH2C1CO2H  . 

2.6645 

).3753 

CnSO, 

CaO 

0  4667 

2  1427 

Cl 

Ca 

0  5653 

1  7690 

CaSO4 

BaSO4  

1.7147 

0.5832 

Cl  

CaCl2  

1.5650 

0.6390 

AxA'=BandBXB'=A. 

*  Phenolphthalein  indicator. 


TABLES  AND  USEFUL  DATA 

XVIII.— CONVERSION  FACTORS  (Continued) 


807 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

Cl 

CsCl.  . 

4.7454 
1.0284 
1.3831 
3.5792 
1  1027 

0.2107 
0.9724 
0.7230 
0.2794 
0.9069 
0.4756 
0.5386 
0.5919 
5.0657 
2.9162 
0.7447 
0.3488 

1.7590 
0.8158 
1.5417 
0.6066 
0.3331 
0.2896 
1.9656 
0.6628 
0.4150 
0.2933 
1.1919 
0.5438 
0.2551 
0.2194 
0.5204 

CO2.  .  . 

Mg(HC03)2  . 
MgO  
MnCO3  
Mn(HCO3)2.. 
MnO  

1.6629 
0.9164 
2.6121 
2.0108 
1.6121 
2.4091 
1.9093 
3.6667 
1.4091 
2.1836 
6.0705 
5.2477 
3.3273 
4.2478 
3.3551 
2.3823 
2.3550 
2.8493 

0.6013 
1.0913 
0.3828 
0.4973 
0.6203 
0.4151 
0.5238 
0.2727 
0.7097 
0.4579 
0.1647 
0.1906 
0.3006 
0.2354 
0.2981 
0.4198 
0.4246 
0.3510 

Cl 

HC1  

C02  
CO2  

T    2 

CO2  

Cl 

K 

CO2  

Cl 

KC1  

2.1027 
3.4563 
3.9075 
0.1974 
0.3429 
1.3429 
2.8672 

0.5685 
1.2257 
0.6486 
1.6486 
3.0023 
3.4535 
0.5088 
1.5088 
2.4098 
3.4098 
0.8390 
1.8390 
3.9202 
4.5572 
1.9217 

CO2  
CO2. 

NaSeoi!  ;  ;  '. 

Na2SO4  
Na2O  
(NH4)2C03... 
PbCO3  
Rb2C03  
RbHCO3.... 
Rb2O  

Cl  
Cl     

KC103  
KC1O4  

C02  
C02  

Cl 

Li  

Cl  
Cl  
Cl 

Mg  
MgCl2  
MgCl2-6H2O 
MgOin 
MgCl2 
Mn02  
Na  

CO2  
CO2 

CO2.  .  . 

Cl 

CO2  

Cl  
Cl 

C02  
CO2  

SrC03  
Sr(HC03)2  .  . 
SrO  

CO2  

NaCl  
NaClO3  

CO2  

Cl 

C02  

ZnCO3  

NaClO4  
NH4  
NH4C1   

Cl  
Cl 

Cr..  , 

BaCrO4.. 
Cr203  
PbCrO4  
K2Cr2O7  
BaCrO4  
CrO3  

4'.  8651 
1.4606 
6.2136 
2.8029 
3.3308 
1.3157 
4.2513 
2.5322 
1.9411 
1.4706 
3.2233 

0.2055 
0.6846 
0.1609 
0.3535 
0.3002 
0.7602 
0.2352 
0.3949 
0.5152 
0.6800 
0.3097 

Cr  

Cl 

Rb  

Cr  
Cr  
Cr20  
Cr2O  

Cl 

RbCl   

Cl  . 

SninSnCU.  . 
SnCl4  
PbCl2  

Cl 

Cl 

Cr2O  

PbCr04  
BaCrO4  
K2CrO4  

Cl 

PbCrO4  

CrO3  

Cl 

ZnCl2 

CrO3  

CrO, 

K2Cr2O7  
PbCrO4  

Co 

CoNO3-6H2O 

Co(N02)3 
(KN02)3 
CoO  

4.9361 
7.6706 

1.2714 
1.3053 
4.7677 
2.0680 

0.2026 
0.1304 

0.7866 
0.7661 
0.2097 
0.9336 

Cr03  

Co.  . 

Cs 

CsCl 

1.2670 
1.0602 
1.2258 
1.3617 
0.3945 
0.41S2 

0.7893 
0.9432 
0.8157 
0.7344 
2.5351 
2.3911 

Cs  
Cs  
Cs 

Cs2O  
Cs2CO3  

Co 

Co3O4  
CoSO4-7H2O 
Co3O4  

Co 

Cs2SO4  

CoO 

CsPtCU  
CsPtCU  

Cs  

PO 

R  CO 

4.4857 
3.4857 
2.9476 
0.2727 
2.2743 
1.8419 
1.2743 
1.3636 
7.4005 
2.6327 
2.0211 
2.2292 
3.1409 
2.1409 
1.6818 
1.5457 
0.6818 
1.9164 

0.2229 
0.2869 
0.3393 
3.6667 
0.4397 
0.5429 
0.7847 
0.7333 
0.1351 
0.3798 
0.4948 
0.4486 
0.3184 
0.4671 
0.5946 
0.6470 
1.4667 
0.5218 

2 

COa 

BaO 

Cu.. 
Cu  
Cu  
Cu  
Cu     

CuO  
Cu2O  

1.2517 
1.1258 
1.2522 
2.5112 
3.9283 
0.5226 
0.6541 
2.0062 
1.2327 
3.1383 
0.3353 
0.9996 
0.8991 

0.7989 
0.8888 
0.7986 
0.3982 
0.2546 
1.9137 
1.5288 
0.4985 
0.8112 
0.3186 
2.9822 
1.0004 
1.1.122 

1.1433 

CO2 

Ba(HC03)2.. 
C  

CO2 

Cu2S  
CuS04  
CuSO4-5H2O 
Cu  

CO2 

CaCO3  

CO2 

Ca(HCO3)2.. 
CaO 

CO2 

CuCNS  

C02  
CO2 

C03  
CsCO3  

CuCNS  
CuO.. 

CuO  

CuSO4  

CO2 

FeCO3  

CuO.. 

H2SO4  

CO2 

Fe(HC03)2... 
H2SO4 

CuO  
CuS  

CuSO4-5H2O 

s  . 

CO2 

CO2 

K2CO3   

Cu2S  

CuO 

CO2 

K2O   

Cu2S  

Cu2O  

LiCO3 

CO2 

LiHCOs  
Li2O  
MgCO3  

Er2O3  

Er  

0.8746 

C02  
CO2 

F  

BaSiF6 

2.4533 

0.4076 

AXA'=BandBXB'=A. 


808 


TABLES  AND  USEFUL  DATA 

XVIII.— CONVERSION  FACTORS  (Continued) 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

F 

CaF2.  .  , 

2.0545 
3.5827 
1.0531 
1.2660 
1.9342 
2.2105 

0.4868 
0.2791 
0.9496 
0.7899 
0.5170 
0.4524 

FeS2 

S  

0.5346 
0.6457 
0.3528 
0.7358 

0.1114 

1.8706 
1.5487 
2.8345 
1.3590 

8.9808 

1.3434 

1.6882 

F        

CaSO4  

FeSO4.  . 
FeSO4-7H2O. 
Fe,(S04)i.... 

FeSO4(NH4)2 
SO4-6H2O 

H2SO4  

F  
F  
F  
F  

HF  
H2SiF6  
K2SiF6  
NaF  

H2SO4  

H2SO4 

Na2Cr2O7.... 

Fe  

FeCl2  .  . 

2.2701 
4.8410 
3.1851 
1.2865 
1.4298 
1.3820 
2.7020 
1.5743 
2.7205 
4.9789 
3.5807 

7.0225 
0.5643 
0.7820 
0.3798 
0.4948 
0.4742 
1.6125 
2.4757 
1.1114 
2.1002 
1.2237 
2.1146 
3.8700 
1.3653 
1.1146 
0.6400 
2.0318 
1.4509 
2.2277 
0.9666 
1.8898 
1.1011 
1.5028 
1.9027 
3.4822 

4.9118 
2.5032 
1.8428 
1.5032 
0.4708 
2.6554 
0.3877 
1.1155 
0.3648 
0.6654 

0.4405 
0.2066 
0.3140 
0.7773 
0.6994 
0.7236 
0.3701 
0.6352 
0.3676 
0.2008 
0.2793 

0.1424 
1.7721 
1.2788 
2.6327 
2.0211 
2.1088 
0.6202 
0.4039 
0.8998 
0.4761 
0.8172 
0.4729 
0.2584 
0.7324 
0.8972 
1.5625 
0.4922 
0.6892 
0.4489 
1.0346 
0.5292 
0.9082 
0.6655 
0.5256 
0.2872 

0.2036 
0.3993 
0.5427 
0.6648 
2.1239 
0.3766 
2.5791 
0.9863 
2.7431 
1.5029 

Ga2O3  

Ga.. 

0.7444 
0.5923 

Fe  
FP 

FeCl3-6H2O.. 
Fe(HC03)2... 
FeO  

Ga2S3 

Ga 

Fe  

Ge02... 
K2GeF6  

Ge  
Ge  

0.6938 
0.2739 

1.4414 
3.6510 

Fe  
Fe  
Fe  
Fe  

Fe2O3  
Fe3O4  
FePO4  
FeS  

G10   . 

Gl. 

0.3626 
3.1881 
7.0607 

2.7582 
0.3137 
0.1416 

G10  

G!C12  

Fe  
Fe  

FeSO4-7H2O 

G10  

G1SO4-4H2O.. 

Fe  

Fe2(SO4)3.... 
FpSO.fNH.-'U 

H  

H2O.  . 

8.9363 
0.5643 
1.3324 
2.3195 
3.9305 
1.3720 
0.9724 
1.2893 
1.7280 
1  .  1255 
1.3448 
2.0445 
1.2915 
1.6030 
1.4533 
1.4669 
1.7882 

0.1119 
1.7721 
0.7505 
0.4311 
0.2544 
0.7288 
1.0284 
0.7756 
0.5787 
0.8885 
0.7436 
0.4891 
0.7743 
0.6239 
0.6881 
0.6817 
0.5592 

Fe.(titr.equiv.) 

Fe  

S04 
HNO3  

H3BO3  
HBr  
HBr  
HC1  
HC1  
HC1... 

B203  
Ag  
AgBr  
AgCl  
CaC03  
Cl  

bX.*..7:;:: 

C02  

FeCO3  
Fe(HC03)2... 

Fp/S 

FeO 

FeCO3 

HC1  

HNO2  
HNO3  
H2SO3  

FpO 

Fe(HC03)2... 

HC1  

FpO 

HC1  

FeO 

FePO4   . 

HC1  
HC1  

H2S04  
KC1  

FpO 

FP$ 

FeO 

FeSO4. 

HC1  
HC1  

K2O  
NaCl  
Na2CO3  

FpO 

FeS04-7H20. 
HoSO,, 

FpO 

HC1  

FeO  
FpoO, 

S03  
ALO, 

HC1  

NH4C1   

HC1  

SnCl4  

FejOs 

FeCO3k 

HC02H  

H2S04  

1.0658 

0.9383 

Fe(HC03)2... 
Fe3O4 

FeW  

HF.. 

BaSiF6  

2.3297 
1.9508 
3.4021 
0.9496 
2.4510 
1.8368 
3.6065 
1.2022 

0.4292 
0.5126 
0.2939 
1.0531 
0.4080 
0.5444 
0.2773 
0.8318 

0.8498 
0.7388 
0.9261 
0.8622 
2.4859 
1.8100 
1.1502 
1.1670 

FeY)3 

FePO4 

HF  

CaF2  

Fe2Oi 

FeS  

HF  

CaSO4  

Fe2O3 

HF  

F  

FeSO4.. 
FeSO4-7H2O 
FeSO4(NH4)2 
SO4-6H2O 
Fe^SO^s.... 
H2SO4  

HF  

H2SO4  

FeiOs 

HF  

K2feiF6  

FeiO,... 

HF(2HF)  .  .  . 
HF(6HF)  .  .  . 

H2SiF6  

TP  O 

H2SiF6  

Fe.0,  
Fe,0,  
FeP04  
FeS 

Hg  
Hg 

HgCl  
HgCl2  

1.1768 
1.3535 
1.0798 
1.1599 
0.4023 
0.5525 
0.8694 
0.8569 

SO,  
P205  
BaSO4 

Hg  
Hg 

HgO  
HgS  

FeS  
FeS  

H2S  
H2SO4  

HgCl 

fends 

HgCl  
HgCl2 

SnCl4  
HgCl  

FeS  
FeS,  

S  

HgCl2  

HgS  

AXA'=BandBXB'=A. 


TABLES   AND   USEFUL   DATA 
XVIII.— CONVERSION  FACTORS   (Continued) 


809 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

HffO 

HgCl 

.1827 
.1321 
.0860 
.1290 
.3962 
0.8963 
0.9307 
1.2758 

0.8455 
0.8834 
0.9208 
0.8857 
0.7162 
1.1158 
1.0744 
0.7838 

H2SiF6 

BaSiF6  .  . 

1.9379 
0.54  0 
0.7899 
0.2773 
0.8318 
2.0391 
1.5279 
0.7227 
0.9860 
0.7699 

0.5160 
1.8485 
1.2660 
3.6065 
1.2022 
0.4904 
0.6545 
1.3837 
1.0141 
1.2988 

Hg2O  

HgCl  
Hg(CN)2.... 
HgN03  
Hg(N03)2.... 
Hg20  
HgO  
HgS04  

H2SiF6  
H2SiF6  
H2SiF6  
H2SiF6  
H2SiF6  
H2SiF6  
H2SiF6 

CaF2  
F  
2HF  

HgS  
HgS  
HgS  
HgS  

HgS 

6HF  

H2SO4  

K2SiF6 

He:S 

SiF4 

H2SiF6 

SiF6 

HI.  . 

A  -  

0.8433 
1.8354 
0.4170 
1.4092 

2.5868 

1  .  1859 
0.5448 
2.3979 
0.7097 
0.3866 

H2Si03  

SiO2  

Ao-T 

HI 

J^fe1  

Pd 

H2SO3. 

BaSO4 

2.8437 

0.8885 
1.1949 
0.7805 

0.3517 
1.1255 

0.8369 
1.2812 

HI  
HI 

PdI2  

Tl 

H2SO3. 

HC1 

H2SO3  

H2SO4. 

H2SO3  

SO2  

HNO2.  .  , 
HNO2  

AgN02  
HC1   

3.2729 
0.7756 
1.0431 
0.6382 
.5627 
0.5787 
).7782 
1.6045 
0.2223 
1.3490 
0.2702 
0.8489 
3.5215 
0.4  62 
0.6032 
0.7301 
0.8571 
1.5471 

0.3055 
1.2893 
0.9587 
1.5667 
1.7772 
1.7280 
1.2850 
0.6233 
4.4981 
0.7413 
3.7006 
1.1780 
0.2840 
2.0999 
1.6579 
1.3697 
1.1668 
0.6464 

H2S04  
H2S04  
H2SO4  
H2SO4 

A1C13  
A12O3  

A12(S04)3.... 
Ba(OH)2..  .. 
BaSO4  
C(in  BaCO3) 
Ca(CH3CO2)2 
CaO 

0.9072 
0.3473 
1  .  1636 
1.7473 
2.3800 
0.1223 
1.6120 
0.5716 
1.3878 

1.8361 
1.2241 
1.6725 
1.0404 
0.9177 
1.2851 
1.5298 
0.7230 
0.4487 
1.6275 
0.5203 
0.7324 
0.5427 
0.8963 
1.5487 
2.8345 
1.3590 
0.9648 
0.7436 
0.9177 
0.9383 
0.4080 
0.9587 
1.2850 
0.9998 
0.6950 
0.8369 

1  .  1023 
2.8792 
0.8594 
0.5723 
0.4202 
8.1740 
0.6203 
1.7494 
0.7205 

0.5446 
0.8169 
0.5979 
0.9612 
1.0897 
0.7782 
0.6537 
1.3831 
2.2287 
0.6144 
1.9220 
1.3653 
1.8428 
1.1155 
0.6457 
0.3528 
0.7358 
1.0365 
1.3448 
1.0898 
1.0658 
2.4510 
1.0431 
0.7782 
1.0002 
1.4388 
1  .  1949 

HNO2  

H2SO4  

HNO2  

NO  

HNO3 

Cl 

HNO3  

HC1  
H2SO4 

H2S04  
H2SO4. 

HNO3 

HNO3  

KNO3  
N  
NaNO3  
NH3  
NH4C1  
(NH4)2PtCl6.  . 
NO 

H2S04  
H2SO4. 

HNO3  
HNO3 

H2S04  
H2S04  

H2SO4. 

CaS04  
CH3CHOH 
CO2H 
CH3CO2H.  .. 
CH3CO2Na  .  . 
(CH3CO2)2O 
C2H2O4  
C2H2O4-2H2O 
C4H606  
Cl,  
CO2  
CuSO4  
Fe 

HNO3  
HNO3  
HN03  
HNO3. 

H2SO4. 

HNO3. 

N2O3. 

H2SO4  

HNO3  

N2O4  

H2S04  
H2S04  
H2S04  
H2SO4  
H2SO4  
H2SO4 

HNO3  

N2O5  

HNO3.  .  . 

Pt. 

H3PO4.. 
H3PO4 

HPO3.. 
H4P2O7  . 

0.8163 
0.9081 
1.0002 
1.1356 
0.3165 
0.7244 

0.376 

1.2251 
1.1012 
0.9998 
0.8806 
3.1593 
1.3804 

2.6558 

H3PO4 

H2SO4  
Mg2P2O7  
P  

H2SO4. 

H3PO4   . 

H2SO4  
H2S04  
H2SO4  

FeO  
Fe2O3  
FeS. 

H2PO4  

H3PO4  

p,O5  

H2PtCl6 
•6H2O 

Pt  

H2SO4  

FeS04  
FeSO4-7H2O 

Fe2(SO4)3.... 
H3AsO4 

H2SO4  
RoSO, 

H2S. 

As2S3 

2.4074 
6.8493 
4.2379 
2.5791 

1.4388 
0  9388 

0.4154 
0.1460 
0.2360 
0.3877 
0.6950 
1.0629 
0.5309 
0.4258 

H2SO4 

H2S. 

BaSO4 

H2SO4  
H2SO4  
H2S04  
H2SC4  
H2SO4  
H2SO4  

HC1  
H2C2O4  
HCO2H  
HF  
HNO2. 

H2S. 

CdS 

H2S.. 

FeS. 

H2S*  
H2S  

H2SO4  

H2S  

H2S. 

SO2.., 
S03  

1.8835 

2.3488 

HN03  
H3P04  
H2S  
H2SO3  

H2SO4*  
H2SO4*  
H2SO4*  

H2Se03  

Se  

0.6129 

1.6315 

AXA'=B  and  BXB'=A. 

*  Phenolphthalein. 


810 


TABLES  AND  USEFUL  DATA 

XVIII.— CONVERSION   FACTORS  (Continued) 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

H2S04  
H2S04  

H2SO4 

H2SiF« 

0.4904 

3.2253 
3.8362 
2.0617 
0.9604 
1.1442 
0.7493 
1.7767 
0.4111 
1.2274 
1.1920 
1.0808 
1.3661 
2.6711 
1.7132 
2.4583 
2.8964 
2.1222 
1.7334 
0.6321 
0.8158 
3.3448 
0.7959 
0.9598 
2.5706 
1.4404 
0.3473 
1.0909 
0.5310 
0.6948 
1.3473 
2.3268 
0.7750 
0.9382 
1.1013 

0.0275 
0.7243 

0.0629 
0.3267 
0.6532 
1.3064 
0.8163 
0.7309 
0.7921 
0.6665 
0.8296 
1.6459 

2.0391 

0.3101 
0.2607 
0.4850 
1.0413 
0.8740 
1.3345 
0.5628 
2.4325 
0.8147 
0.8389 
0.9252 
0.7320 
0.3744 
0.5837 
0.4068 
0.3453 
0.4712 
0.5769 
1.5820 
1.2258 
0.2990 
1.2564 
1.0418 
0.3  90 
0.6904 
2.8792 
0.9167 
1.8382 
1.4392 
0.7422 
0.4298 
1.2903 
1.0659 
0.9080 

36.364 
1.3806 

15.878 
3.0590 
1.5309 
0.7655 
1.2250 
1.3683 
1.2625 
1.5004 
1.2054 
0.6076 

I 

KI 

1.3081 
1.6863 
1.55  4 
0.4967 
0.4203 
1.4204 
2.6074 

0.7645 
0.5930 
0.6413 
2.0135 
2.3790 
0.7040 
0.3835 

K2A12(S04)4 
•24H2O 
KHC4H4O6  .  . 
KNOj. 

I   .. 

KIO3   .  .  . 

NaI03  

H2SO4 

Pd. 

H2SO4  
H2SO4 

K2O  
KOH   .  .  

PdI2  

Tl  

H.erv 

K,SiF« 

H2SO4 

K2SO4  

In.. 
In  

In2O3   . 

1.2090 
1.4187 

0.8271 
0.7047 

H2SO4. 

MgO  

In2S3  

HnSO, 

H2SO4 

Nafol 

Ir  

Ir203  

1.2491 

0.8006 

0.8302 
0.1609 
0.4487 

17.510 
9.2863 
2.1949 
3.2253 
2.4190 

7.3984 
12.1363 
1.0251 

1.3199 
1.4892 
3.0440 
0.6911 
0.5202 
2.1027 
2.0445 
0.3963 
0.3069 
0.8557 
0.4010 
0.8550 
0.4863 
0.8550 
3.1409 
1.2315 
0.7930 
0.7666 
1.9411 
O..r807 
1.4706 
0.8782 
3.1252 
2.2752 
0.5834 
3.0440 

TT  Q/~)    J. 

Na2CO3  
Na2C2O4. 

H2SO4 

K.. 
K  

K2O.. 
K2PtCl6  

1.2046 
6.2143 

2.2285 

0.0571 
0.1077 
0.4561 
0.3101 
0.4134 

0.1352 
0.0824 
0.9756 

0.7570 
0.6715 
0.3285 
1.4469 
1.9225 
0.4756 
0.4891 
2.5233 
3.2589 
1.1686 
2.4935 
1.1696 
2.0564 
1.1696 
0.3184 
0.8120 
1  2610 
1.3046 
0.5153 
1.7220 
0.6800 
1.1388 
0.3200 
0.4395 
1.7141 
0.7645 

H2SO4 

Na%C03.'  .'  .'  .' 
NaH2PO4  .  .  . 
Na2HP04.... 
NaHSO3.   . 

H2S04f  
H2S04*  
H2SO4f 

K.  . 

K2S04  

K2A12(SO4)3 
24H20 
ditto 
ditto 
ditto  * 
ditto  (total) 

ditto 
ditto 

K2A12(S04)3.. 
KBF4  

Al.. 

H2SO4 

A12O3  

H2SO4 

NaN03. 

H2O  
H2SO4  

H2SO4 

Na2O 

H2SO4 

NaOH 

H2S04(+A1 
S... 

H2SO4 

Na3P04   .  . 

H2SO4 

Na1sb3!'.  ;::: 

K 

H2SO4 

NaHCO3.  ... 

4  10H20 
Br. 

H2SO4 

H2SO4 

NH3 

KBr 

NH.C1  
(NH4)2O 

H2SO4 

KBr 

K 

H2SO4. 

(NH4)2S  

KCl  
KCl  
KCl 

Ag  
AgCl. 

H9SO.1 

(NH4)2S04..  . 
(NHO&O..  . 
N2O3 

H,SO4 

Cl 

H2SO4 

KCl 

HC1 

H2S04  
H2S04  
H2S04t 

H2S04'f  ' 
HW^1*0 

N204  
N206  

p 

KCl  
KCl 

KHC4H40«  .  . 
K2PtCl4  

KCl 

K2SO4  

KCl 

Pt  

P206  

P205 

KC1O3   

AgCl  

KCN  
KCN  
K2CO3  

AgCN  

AgCl  

s 

CO2  

H2S04f  
H2S04*  
H2SO4. 

S02  
S02  

SO3. 

K2CO3   

KOH  

K2CO3   

K2SO4  

K2Cr04  
K2CrO4  
K2Cr2O7  

BaCrO4  
CrO3 

S205C12  
SO3HC1.  . 

H2SoI 

BaCrO4  

H2SO4.  . 

Zn  

K2Cr2O7  
K2Cr2O7  
K2Cr2O7  
KHCO3  
KHSO4.   .  .  . 

CrO3  
Fe  
K2O  
C02  
BaSO4  

H2SO4  

ZnO  

ZnSO4. 

* 

I 

AeL. 

1.8500 
0.2794 

0.5405 
3.5792 

1  

Cl  

KI   

AXA'=BandBXB'  =  A. 

*  Phenolphthalein.  f  Methyl  Orange, 

t  Titration  of  yellow  precipitate,  ammonium  phosphomolybdate. 


TABLES  AND   USEFUL  DATA 

XVIII —CONVERSION  FACTORS  (Continued) 


811 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

KI       

K  

0.2355 
0.4826 
0.4850 
2.4041 
0.8408 
0.2968 
0.5342 
0.8741 
1.2315 
0.8394 
0.7529 
0.4671 
0.7743 
1.0413 
2.8302 
2.5270 
1.5830 
1.0627 
1.4671 
3.9936 
3.1252 
3.5248 
1.1913 
2.1466 
5.1609 
1.8500 
0.8500 
0.1609 
0.3068 
0.2844 
0.4159 
0.1938 
0.3585 

1.9530 

2.0559 
0.4013 
0  6931 
0.8785 
0.5170 
0.5444 
0.6545 
1.3345 
0.5270 
0.4730 
0.2735 
0.3903 
0.5628 
0.4487 
0.8557 
0.7930 
0.5405 
2.7897 
0.4595 

4.2460 
2.0721 
2.0617 
0.4159 
1.1894 
3.6898 
1.8721 
1  .  1440 
0.8120 
1.1913 
1.3282 
2.1409 
1.2915 
0.9604 
1.2046 
0.3957 
0.6317 
0.9410 
0.6816 
0.2504 
0.3200 
0.2837 
0.8394 
0.4658 
0.1938 
0.5406 
1.1765 
6.2143 
3.2589 
3.5162 
2.4041 
5.1609 
2.7897 

0.5120 

0.4964 
2.4921 
1.4427 
1.1383 
1.9342 
1.8368 
1.5276 
0.7493 
1.8976 
2.1141 
3.6567 
2.5622 
1.7767 
2.2285 
1.1686 
1.2610 
1.8500 
0.3585 
2.1765 

La  

La2O3  

1  .  1727 

0.8528 

KMnO4  
KNO3  
KNO3 

Mn  Ox 

H2SO4 

Li 

LiCl 

6.1096 
5.3227 
2.1539 
5.5629 
7.1296 
0.3523 
2.4630 
3.6799 
2.5842 
0.9569 
1.7601 
1.4240 
0.1262 
0.7712 

0.1637 
0.1879 
0.4643 
0.1798 
0.1262 
2.8381 
0.4044 
0.2718 
0.3870 
1.0451 
0.5682 
0.7023 
7.9216 
1.2966 
1.3732 

K2PtCl6 

Li 

Li2CO3  .... 

KNO3 

NaNO3.    .  . 

Li  
Li 

Li20  
Li2PO4  

KN03      

NO  

KNO3  
KOH     

N205  
H2S04  
K2CO3  

LiCl  
LiCl  

Li3S04  
Li^O  

KOH     

Li2O  

Li2CO3  
Li2SO4  
Li3PO4  
Li2CO3  
LiHCO3 

KOH  
K2O 

K2O  
Cl 

Li2O  
Li2O  
Li3PO4  
Li3PO4 

K2O  
K2O  
KoO 

C02  
HC1  

H2SO4  

Li3PO4  

Li2SO4 

Li2SO4  

K2O       

K  

Li 

K2O 

KBr  

Li2SO4  
Li2SO4  

LiCl  

K2O         

KC1  

S03  

0.7282 

K2O  
K2O   

KHCO3  
K2CO3  
KHC4H4O6  .  . 
K2Cr2O7  
KI 

Mg  
Mg  
Mg  
Me 

Cl.. 
MgO 

2.9162 
1.6579 
4.5789 
4.9450 
0.7447 
0.3488 
0.5218 
0.6013 
5.7897 
1.7590 
1.0913 
2.4325 
2.3621 
2.0913 
3.6294 
2.7619 
2.9859 
3.5236 
0.7954 
1.9859 
1.3932 
0.8806 
0.2184 
1.2784 
0.8552 
1.8260 
0.7575 
1.3141 
0.3621 
1.0811 
2.2143 
1.4731 
1.2755 
1.2758 
1.0336 
1  .  1865 
0.2787 

0.3429 
0.6032 
0.2184 
0.2020 
1.3429 
2.8672 
1.9164 
1.6629 
0.1727 
0.5685 
0.9164 
0.4111 
0.4234 
0.4782 
0.2755 
0.3621 
0.3349 
0.2838 
1.2572 
0.5036 
0.7178 
1  .  1356 
4.5789 
0.7822 
1  .  1692 
0.5477 
1.3203 
0.7610 
2.7619 
0.9250 
0.4516 
0.6789 
0.7840 
0.7838 
0.9675 
0.8428 
3.5877 

K2O 

K2O  

Mg2P207  
MgSO4  
Cl 

K2O 

K2O 

KOH 

MgCl2 

K2O 

KNO3 

MgCI2'6H2O 
MgCO3  
Mg(HC03)2.. 
MgO  
MgO. 

Cl  
CO2  
CO2  
BaSO4  
Cl  

K2O  
K2O  

K2PtCl6  
K2SO4  
SO3 

K2O 

K2PtCle 

K 

K2PtCl6 

KC1 

MgO  
MgO.  .  .  . 

C02  
H2SO4  
MgCl2  
MgC03  
Mg(HC03)2  . 
Mg2P2O7 

K2PtCl6 

K2C03  
KNO3.     .  .    . 

K2PtCl6  
K2PtCl6  
K2PtCl6  
K2PtCl6  

K2PtCl6  

MgO  
MgO  

K2O   

K2SO4  

MgO  

K2A12(S04)4 
•24H2O 
K2Cr2(SO4)4 
•24H2O 
Pt  
PtCl4  

MeO 

MgO 

MgSO4 

MgO  
Me:O 

Na2SO4  
S 

K2PtCl6... 
K2PtCl6 

MgO  
Mg2P2O7  

SO3  
Ca3(P04)2.... 
H3P04  
Mg  

K2PtCl6  
K2SiF6  .  .   . 

PtCl4-5H2O.. 
F  

Mg2PoO7  

Mg2P207  
Mg2P2O7  
Mg2P2O7  
Mg2P2O7  
Mg2P2O7  
Mg2P2O7  
Mg2P207  
Mg2P207  
Mg2P207  
Mg2P207  
Mg2P2O7  
Mg2P2O7  
Mg2P207  
Mg2P2O7  
Mg2P207  

K2SiF6  

HF  

Mg(CH3C02) 
MgCl2  

K2SiF6  

H2SiF6  
H2SO4. 

K2SiF6 

MgCl2-6H2O 
MgC03  
Mg(HCO3)2  . 
MgO  
MgSO4. 

K2SiF6  . 

KF 

K-SiF6. 

SiF4  

K2SiF6  

K2SiO3  
K2SO4  

SiO2  

SiO2  

H2SO4  

MgSO4-7H2O 
Na3PO4.  .  .  . 

K2S04  
K2SO4 

K....  
KC1 

Na2HPO4.... 
Na2SO4  
(NH4)H2P04. 
(NH4)2HP04. 
P  

K2SO4 

K2CO3  

K2SO4.     . 

K2O  
K2PtCl6  
SO3  

K2SO4  
K2SO4 

AXA'=BandBXB'=A. 


812 


TABLES  AND   USEFUL  DATA 
XVIIL— CONVERSION  FACTORS  (Continued) 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

Mg2P207  
MgSO4 

P205  
BaSO4 

0.6379 
1.9389 
0.8147 
u.6651 
0.3248 
0.9469 

1.5676 
0.5158 
1.2274 
1.5036 
3.0786 
1.056 

Na.. 
Na 

Nal.. 
Na2O 

6.5183 
1.3478 
1.7391 
2.6754 
3.0885 
0.6224 

0.1399 
0.6931 
1.2282 

0.1832 
0.6492 
1.3199 
1.0458 
1.8247 
0.7765 
2.4519 
2.9061 
.4786 
0.6066 
0.6239 
0.8389 
0.9066 
1.4370 
1.2149 
1.7803 
0.5303 
1.2151 
1  .  1656 
0  3331 
0.2896 
2.2022 
0.9441 
0.5290 
1.1327 
0.4151 
0.6881 
0.9253 
0.4340 
1.1030 
0.7925 
1.9637 
0.7549 
0.5849 
0.7320 
1.9944 
1.2788 
0.3744 
1.2367 
0.9294 
0.9135 
0.4031 
0.6182 
0.8349 

0.1534 
0.7419 
0.5750 
0.3738 
0.3238 
1.6067 

7.1474 

1.4429 
0.8142 

5.4594 
1.5404 
0.7577 
0.9562 
0.5480 
1.2878 
0.4078 
0.3441 
2.0852 
1.6486 
1.6030 
1  .  1920 
1  .  1030 
0  .  6959 
0.8231 
0.5617 
1.8858 
0.8230 
0.8579 
3.0023 
3.4535 
0.4541 
1.0593 
1.8905 
0.8828 
2.4091 
1.4533 
1.0807 
2.3044 
0.9066 
1.2618 
0.5092 
1.3247 
1.7097 
1.3661 
0.5014 
0.7820 
2.6711 
0.8086 
1.0760 
1.0947 
2.4809 
1.6177 
1  .  1978 

MgSO4 

H2SO4 

Na 

NaOH 

MgS04  
MgSO4-7H2O 
MgSO4-7H2O 

S03  

SO3 

Na  
Na 

Na,SO3  
NaoSO4. 

BaSO4 

Na^ALA.... 
Na2Al2(S04)4 
•24H2O 
Na2B4O7  
Na2B4O7  
Na2B4O7 
•10H2O 
ditto 
ditto 
NaBr  
NaBr  
NaBr   

A12O3  
S            .... 

Mn 

MnCO3 

2.0923 
1.2913 
1.4369 
1.3884 
2.5846 
1.5838 
0.3828 
0.4973 
1.6203 
1.1128 
1.2266 
1.1289 
2.0721 
0.9662 
2.0398 
0.2032 
2.5848 
1.5458 
0.5303 

0.4779 
0.7744 
0.6959 
0.7203 
0.3869 
0.6314 
2.6121 
2.0108 
0.6172 
0.8987 
0.8153 
0.8859 
0.4826 
1.0349 
0.4902 
4.9224 
0.3869 
0.6469 
1.8858 

Mn           

MnO 

B203  
H3BO3  

Mn  
Mn  
Mn      

Mn2O3  
Mn3O4  
Mn2P2O7  
MnS. 

BaOg    . 

Mn        

H3BO3  

MnCO3  
Mn(HCO3)2.. 
MnO 

C02  
C02  
MnCO3 

KBF  

Ag  
AgBr  
Br  

MnO   

Mn2O3  
MnS  
S03  
KMnO4  
Mn3O4 

MnO  
MnO  
Mn2O3  
Mn2O3 

NaCl  

A  Cl  

NaCl  
NaCl  

AgNO3  
CaO  

NaCl  

Cl  

Mn2O3  
Mn2O3   .  .    .  . 

MnSO4. 

NaCl  

HC1  

S. 

NaCl  

H2SO4  

Mn3O4  
MnSO4 

K2MnO4  
BaSO4 

NaCl  
NaCl  

Na2CO3  
NaHCO3.... 
Na2HPG4.... 
NaHSOa  
Na2O  

MnSO4. 

SO3  

NaCl  

NaCl  
NaCl  

Mo  
Mo 

MoO3.. 
MoS3 

1.5000 
2.0022 
3.8239 
1.3348 
1.3617 

1.0863 
2.5494 
1.8722 

0.6667 
0.4995 
0.2615 
0.7492 
0.7344 

0.9205 
0.3923 
0.5342 

NaCl  

Na2SO4  

Mo 

PbMoO4  
MoS3 

NaCl  

ZnCl2  

Mo03  
MoO3.. 
MoO3  

MoO3 

NaClO3  . 

Cl  

(NH4)2MoO4. 
(NH4)3P04 
(Mo03)12 
PbMo04  
PbMoO4  

NaClO4  .  .  . 

Cl  

Nft2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2CO3  
Na2C2O4  
Na2CrO4  
Na2Cr2O7 

BaSO4 

CaCO3  

CaO  
CHaCOoH... 

POo 

MoO4-(NH4)2 

N., 

N.  .  . 

HNO3.. 
NO2  

4.4981 
3.2841 
2.7131 
3.2841 
3.8551 
6.0678 
1.2155 
6.9665 
2.8576 

0.2223 
0.3045 
0.3686 
0.3045 
0.2594 
0.1648 
0.8227 
0.1435 
0.3499 

HC1 

H2SO4  
Na  
NaCl  
NaHCO3.... 
NaHSO3  
NaOH     

N  
N  

N. 

N203  
N204  
N2Ofi 

N. 

NaNO3 

N.  .  . 

NH3 

N..  . 

Pt 

NaizO   

N.  .  . 

SO« 

H2SO4  

PhCrO, 

Na.. 
Na.. 

Br... 
Cl 

3.4748 
1.5417 
5.5182 
4.4747 
2.5417 
2.3044 
1.8261 
3.6525 

0.2878 
0.6486 
0.1812 
0.2235 
0.3934 
0.4340 
0.5476 
0.2740 

Fe  

Na2Cr2O7  
Na2Cr2O7  
NaF  
Na2HAsO3.  .  . 
Na2HAsO4.  .  . 
Na2HAsO4.  .  . 
Na2HAsO4.  .  . 

HoSO4  
Na2CrO4  
CaF2  

MfeAsaO,.... 

As  
As2O6 

Na.. 

I 

Na  

Na.  .  . 

NaBr 

NaCl 

Na.  .  . 

NajCOs 

Na  

NaF 

Na  

NaHCO3.... 

MgzAszO,..  .. 

AXA'=B  and  BXB'=A. 


TABLES  AND  USEFUL  DATA 
XVIII.— CONVERSION  FACTORS   (Continued) 


813 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

Na2HAsO4.  '  . 
NaHCO3.  ... 
NaHCOa*... 
NaHCO3*... 
NaHCOa  
NaHCOa  
NaHCOa  
NaHCOs.  ... 
NaHCOs.  ... 
NaHCOa.  ... 
NaHCOa.  ... 
NaHCOa.  ... 
NaHCOa*... 
NaHCOa*... 
NaHCOa.  ... 
NaH,PO4*... 
NaH2PO4*... 
NaH2PO4*... 

NaH2PO4*.  . 
NaH2PO4* 

As2O5.. 
A12(S04)3.... 
Ca(H2PO4)  .  . 
CaH2P2O7... 
C4H606  
CO2  
H2SO4 

0.7011 
0.6793 
1.3938 
1.2866 
0.8931 
0.5238 
0.5838 
1.0251 
2.2395 
0.4717 
0.2740 
1.2618 
1.4291 
1.3219 
0.3690 
0.4068 
0.6997 

1.6003 
0.2582 
0.2585 
0.5917 
0.3453 

2.5220 
0.4365 
0.5001 
0.7565 
0.2792 
0.6397 

0.3395 
0.2990 
0.6789 
0.5669 
1.2991 

2.3179 

0.4331 
2.2432 
0.4712 
0.5617 
0.2979 
0.9134 
6.6150 
0.1534 
0.2068 
0.6413 
0.7413 
0.5769 
1.1894 
0.8117 
0.3647 

1.4264 
1.4721 
0.7175 
0.7773 
1.1197 
1.9039 
1.7129 
0.9756 
0.4465 
2.1260 
3.6525 
0.7925 
0.6997 
0.7565 
2.7099 
2.4583 
1.4291 

0.6249 

3.8728 
3.8678 
1.6900 
2.8964 

0.3965 
2.2911 
1.9995 
1.3219 
3.5822 
1.5632 

2.9452 
3.3448 
1.4731 
1.7639 
0.7698 

0.4314 
2.3091 
0.4485 
2.1222 
1.7803 
3.1574 
1.0948 
1.6244 
6.5183 
4.8350 
1.5594 
1.3490 
1.7334 
0.8408 
1.2319 
2.7423 

NaNO3  .  . 
NaNO3. 

NH».. 

NO. 

0.2004 
0.3530 
0.6353 
1.2258 
0.7748 
0.8499 

2.0400 
3.7651 
1.9365 
2.6459 
1.582 
0.7419 
1.8858 
1.7097 
1.3548 
2.7099 
2.2911 
3.8728 
3.5822 
3.3574 
2.7423 
1.2906 
1.7639 
1.2592 
2.0334 
2.2915 
1.1458 
1.2915 
2.9904 
0.4237 
1.2564 
0.7942 
0.4108 
1.8515 
0.3890 
2.0135 
0.4918 
0.5082 
0.2541 
2.9524 

1.5696 
1.6431 
0.3947 
1.1547 
0.6904 
0.2838 
0.7838 
0.3238 
0.8230 
0.7461 
0.5913 

4.9906 
2.8327 
1.5740 
0.8158 
1.2906 
1.1766 

0.4902 
0.2656 
0.5164 
0.3779 
0.6321 
1.3478 
0.5303 
0.5849 
0.7381 
0.3690 
0.4365 
0.2582 
0/.792 
0.2979 
0.3647 
0.7748 
0.5669 
0.7942 
0.4918 
0.4364 
0.8727 
0.7743 
0.3344 
2.3602 
0.7959 
1.2592 
2.4343 
0.5401 
2.5706 
0.4966 
2.0334 
1.9677 
3.9360 
0.3387 

0.6371 
0.6086 
2.5338 
0.8660 
1.4484 
3.5236 
1.2758 
3.0835 
1.2151 
1.3403 
1.6905 

NaNO3.... 
NaOH  

N205  
H2SOi. 

NaOH  

Na2O 

NaOH  
NaOH  

Na20 

Na2SiF6  
(NH4)3P04 

(MoOs)r; 

BaSO4  
CH3CO2H.  .. 
CH3CO2Na.. 
H2SO4  

K2A12(S04)4.. 
KHC4H4O6  .  . 
KMnO4  
Na  
Na2CO3  
NaH2PO4.  .  .  . 
Na2H2P2O4.  .  . 
Na2O  

Na2O  

Na2O 

Na2O  
Na2O  
Na2O   

Na  

NaCl 

NaoO  
Na2O  
Na2O  

Na2CO3  
NaF  
NaHCO3.... 
Na2HPO4  
NaHoPO4.  .  .  . 
Na2H2P2O7.  .  . 
NaHSOa  
NaNOa  
NaOH  
Na3PO4. 

H2S04  
NaHCOs.  ... 
NaH2PO4 
•4H2O 
Na2O  
p. 

Na2O  

Na2O  
Na2O  

Na2O 

NaH2PO4*... 
Na2HPO4f... 
Na2HPO4.  .  .  . 

Na2HPO4.. 
Na2HPO4.... 
Na2H2P2O7.  .  . 
Na2H2P2O7.  .  . 
Na2H2P2O7. 

P205  
H2SO4 

Na2O  

Na.2O 

Na2HPO4 
•12H2O 
Na20  
P205  
NaHCOa  .... 
Na2O  

Na2O  

Na2O  
Na2O  

Na2S  
Na2SO3.  . 

Na2O  

Na2SO4.  . 

Na2O*  

P2O5  

Na2O  

SO3  

P2O5  

Na2S 

BaSO4 

Na(NH4) 
HPO4-4H2O 
Na3PO4  
Na3PO4  
Na3PO4  
Na3PO4  

P205  
H2SO4. 

Na2S  

H2S.  .  . 

Na2S  

Na2S 

H2SO4  

Na2O  
S  

Mg2P2O7  
Na,O  

Na2S  

Na2SO3  
Na2S03  
Na2SO3.  . 

BaSO4  
H2SO4 

Na2SO4  
Na3PO4 
•12H2O 
P2O5. 

Na3PO4.  .  .  . 
Na3PO4 

Na2SO3  
Na2SO3 

Na2O.. 

SO2 

NaHSOa  
NaHSOs. 

BaSO4  .... 

Na2SO4-7H2O 

Na2S2O3 

SO2 

H2SO4  

BaSO4.  .  .  . 
Na2S2O3 
•5H2O 
BaSO4  
CaO 

NaHSO3  
NaHSOs  
NaHSOa  
NaHSO3  
Nal  

NaCl  
Na2O  
Na2S2O5  
S02  
Na  

Na2S2O3 

Na2SO4. 

Na2SO4.  . 

Na2SO4  

CH3CO2Na.. 
H2SO4. 

Nal  

Na2O  

Na2SO4  
Na2SO4  
Na2SO4  
Na2SO4  

NalOa 

I 

MgO  
Mg2P2O7  

Na  . 

NaNOa  
NaNOs  

HNO3  

H2SO4  

NaNOs  

KNO3  

Na2SO4 

NaCl  
Na2CO3  
NaF...  

NaNOa  
NaNO3  

NaNO2 

Na2SO4:  
Na2S04  

Na2O  

AXA'=BandBXB'=A. 

*  Phenolphthalein.  f  Methyl  Orange. 


814 


TABLES  AND  USEFUL  DATA 
XVIIL— CONVERSION  FACTORS  (Continued) 


A 

B 

A' 

B' 

0.6825 
2.2915 
1.8198 
1  .  1269 

0.4409 
1.7743 

A 

B 

A' 

B' 

tffwSO, 

NaHSO3 

1.4652 
0.4364 
0.5495 
0.8874 

2.2681 
0.5636 

Ni  

NiSO4-7H2O. 

4.7863 

0.2089 

^S04  
s  a2oO4  
S  a2oO4  

Nn  O 

Ma2S  

NO.. 

HNO2.  . 

1.5667 
2.0999 
3.3689 

2.8327 

or  0.00 
.  KNC 

)0134  g 
0.00205 

4.0487 
0.9594 
1.6579 
1.0798 
1.2903 
0.3686 
2.0787 
0.7895 
1.2104 
0.7928 
1.3697 
0.9820 
1.0659 
0.3045 
0.6523 
0.6752 
1  .  1668 
0.7599 
0.9080 
1.8721 
1.5740 
0.3153 
0.5556 

0.6382 
0.4762 
0.2968 
0.3530 

28143 
>s,    or 
.  NO, 
45  g. 

0.2470 
1.0423 
0.6032 
0.9261 
0.7750 
2.7131 
0.4810 
1.2666 
0.8262 
1.2617 
0.7301 
1.1210 
0.9382 
3.2841 
1.5332 
1.4810 
0.8571 
1.3159 
1.1013 
0.5342 
0.6353 
3.1714 
1.7997 

NO  

HNO3. 

5  -410H20 
S03  

NO  

KNO3  
NaNO3  

021  g.  HNO2, 
or    0.00415    g 
NaNO3,  or  0.( 
g.    N2O3,   or 

AgN03  
HC1  
HNO3. 

NO  

lccNO  =  O.C 
g.    HNO3, 
0.003796  g. 
or  0.001696 
N204. 

N2O3.  . 

sr  d  

Nd2O3  

1  .  1674 

0.8566 

HNO3. 

3.6995 
2.8792 
0.8227 
4.0513 
4.9906 
3  .  1409 
3.8785 
6.7570 
2.0577 
13.032 
3.8700 
3.1714 

0.1127 
0.1414 
2.6793 
0.6628 
0.6817 
0.9167 
0.9675 
0.1480 
0.8428 
0.2578 
1.8832 

0.0165 
0.0378 
0.2840 
0.4393 
0.7589 
1.4392 
1.7665 
0.7422 
0.2120 
0.2578 
0.8174 
0.4298 

0.2704 
0.3473 
1.2155 
0.2468 
0.2005 
0.3184 
0.2578 
0.1480 
0.4860 
0.0764 
0.2578 
0.3153 

8.8742 
7.0696 
0.3732 
1.5088 
1.4669 
1.0909 
1.0336 
6.7570 
1.1865 
3.8785 
0.5310 

60.475 
26.424 
3.5215 
2.2761 
1.3177 
0.6948 
0.5661 
1.3473 
4.7162 
3.8790 
1.2234 
2.3268 

NTH,  

H2S04  
N         

<TTT3 

NaNO2  
NaNO3 

N203  
N2O3. 

\TH3  

NH4C1  
(NH4)2HP04. 
(NH4)H2PO4. 
NH4OH  
(NH4)2PtCl6  . 
(NH4)2S04.  .  . 
N206  

2A12O3    

N203*  
N203  

N2O3.  . 

H2SO3  
H2S04  

N 

^H, 

N2O3  

NaNO2.  . 

^H3 

N2O3  

NO.    . 

N203  
N2O4  

N204  
HC1       .... 

S  H3  
(NH4)2Ala 
[SO4)4-24H2O 
ditto 
^H4C1 

N2O4  

HNO3  

N2O4*  

H2SO3  

S 

N2O4  

H2SO4  

N2O4  

N   

^H4C1 

Cl 

N2O4  

NO  

VH4C1 

HC1.. 
H2SO4  
Mg2P2O7  

N2O5  

HC1  

SfH4Cl  
[NH4)H2P04. 
(NH4)H2P04. 
(NH4)2HP04. 
(NH4)2HP04. 
(NH4)20  
(NH4)3P04 
(MoO3)12 
ditto 

;NH4)2PtCl6' 
(NH4)2PtCl6  . 
NH4)2S  
NH4)2S04.  .  . 
NH4)2S04.  .  . 
(NH4)2S04.  .  . 
(NH4)2S04.  .  . 
(NH4)2S04.  . 
(NH4)2S208  . 

N205  
N205*  
N2O6.   .  .    . 

HNO3  

H2SO3  

NH3 

H2SO4  

Mg2P2O7.     .  . 

N2OB. 

KNO3  

NH3 

N2O6..    .    . 

NH3. 

H2S04  
p 

N2OB  

N2OB  

NO  

P20B  
HNO3  
Pt  
PtCl6 

Os  

OsO4  

1.3353 

0.7489 

P... 

H3PO4  

3  .  1593 
3.5877 
3.8678 

CO.  476 
2.2887 
1.7197 
1.7193 
1.9161 
1.6483 
1.5214 
2.1839 
2.1239 
1.3804 
1.3806 

0.3165 
0.2787 
0.2585 

0.0165 
0.4369 
0.5815 
0.5816 
0.5219 
0.6067 
0.6573 
0.4579 
0.4708 
0.7244 
0.7243 

P  

NaH2p64.'.' 
(NH4)3P04 
(MoO3)12 
P206  
A1PO4 

H2SO4  

P  

BaSO4  

P  

H2SO4  

P  
P206  
P2O6 

N  

NH3  
N2O3 

A12P2OS  
CaHPO4  
Ca(H2P04)2.  . 
CaH2P207... 
Ca3P2O8 

H2SO4  

P2O6 

P20B  
P205  

Ni.. 

NiC8H4N4O4  . 

Ni(N03)2 
•6H2O 
NiO      • 

4.9221 

4.9556 
1.2727 
2.6371 

0.2032 

0.2018 
0.7858 
0.3792 

Ni 

Ni  
Ni  

p,O5 

FePO4 

H3PO4 

NiSO4. 

P2O6 

H2S04  

AXA'=BandBxB'=A. 

*  Phenolphthalein. 


TABLES   AND   USEFUL  DATA 
XVIII.— CONVERSION  FACTORS   (Continued) 


815 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

1.1731 
1.2679 
1.3272 
1.2676 

P206  
P2O5 

Mg2P2O7 

1.5676 
1.9995 
1.6900 
1.5632 

2.9452 
0.8727 
2.3091 

26.424 

0.6379 
0.5001 
0.5917 
0.6397 

0.3395 
1.1458 
0.4331 

0.0378 

PbSO4  

(PbCO3)2Pb 
(OH), 
PbO2  
Pb3O4 

0.8525 
0.7887 
0.7535 
0.7889 

Na2HPO4..  .. 
NaH2PO4.  .  .  . 
Na2H2P2O7.  .  . 
Na(NH4) 
HPO4-4H2O 
Na2O 

PbSO4.. 
PbSO4 

P2O5  

P2OB 

P2O6  

PbS04  

PbS  

P2O5* 

Pd... 

K2PdCl6. 

3.7270 
2.0024 
3.3791 
2.1623 
2.3970 
2.3790 
0.7096 
0.7040 

0.2683 
0.4994 
0.2959 
0.4625 
0.4170 
0.4203 
1.4092 
1.4204 

P2Oa 

Na3PO4  
(NH4)3P04 
(MoO3)i2 

Pd  

PdCl2-2H2O. 
PdI2  

P2O6 

Pd  

Pd  

HI....3.2." 
I 

Pd  
Pd. 

Pb 

CH3CO2H.. 

Pb(C2H3O2)2  . 
PbCl2 

0.5797 
.5700 
.3424 

.2897 

.2479 
.5601 
.0773 
.1545 
.1643 
.1549 
.4639 
0.1548 
0.2551 
0.1547 
0.1612 
0.2352 
0.5014 
0.6410 

1.1733 

0.7996 
0.6905 
0.7070 
0.9383 
0.5642 
0.2615 
0.3923 
1.2461 
1  .  1972 
0.9283 
1.2461 
1.1972 
1.4842 
1.3589 
0.8659 
0.9328 
0.1341 
0.7700 

1.2507 

1.7249 
0.6369 
0.7449 
0.7754 

0.8014 
0.6410 
0.9283 
0.8662 
0.8589 
0.8659 
0.6831 
6.4599 
3.9202 
6.0705 
6.2034 
4.2531 
1.9944 
1.5600 

0.8523 

1.2505 
1.4482 
1.4142 
1.0657 
1.7722 
3.8241 
2.5491 
0.8025 
0.8353 
1.0772 
0.8025 
0.8353 
0.6738 
0.7359 
1.1549 
1.0720 
7.4577 
1.2987 

0.7995 

Pb  

Pb...  
pu 

PdI2 

HI 

PdI2 

I 

PbCO3.. 

(PbCO3)2Pb 
(OH)2 
PbCrO4  
PbO 

Pb 

Pt..  . 

K2PtCl6 

2.4921 
2.6558 
2.2761 
1.7266 
2.1881 
1.4427 
1.3177 
1.1383 

0.1609 
0.3765 
0.4393 
0.5792 
0.4570 
0.6931 
0.7589 
0.8785 

Pb 

Pt  

H2PtCl6-6H2O 
(NH4)2PtCl6  . 
PtCl4.  .  . 

Pt  

Pb 

Pt  
Pt. 

Pb 

PbO2  
Pb(OH)2.... 
PbS 

PtCl4-5H2O.. 
K2PtClfi  
(NH4)2PtCl«  . 
K2PtCl6  

Pb 

PtCl4.. 

Pb. 

PtCl4  

Pb 

PbSO4 

PtCl4-5H2O.. 

Pb 

g 

PbCl2 

C12 

Pr  

Pr2O3 

1.1707 

0.8542 

PKPO 

ro 

PbCrO4 

Cr  

Rh.. 

Na3RhCl6.... 
RhCl3  

3.7382 
2.0338 

0.2675 
0.4917 

PbCr04  
PbCrO4  
PbCrO4..... 
PbCrO4 

Cr203  
Na2CrO4  
Pb  
Pb(C2H302)2 
•3H2O 
(PbCO3)2Pb 
(OH), 
PbO 

Rh  

Rb.  . 

AeCl. 

1.6775 
2.4098 
1.4150 
1.3510 
1.0937 
1.5622 
3.3862 
1.8550 
0.2933 
1.2686 
1.2939 
1.4284 
0.4178 
0.3987 
0.5060 
0.3229 

0.5961 
0.4150 
0.7067 
0.7402 
0.9144 
0.6402 
0.2952 
0.8435 
3.4098 
0.7883 
0.7729 
0.7001 
2.3938 
2.5071 
1.9762 
3.0972 

Rb  

Cl 

PbCrO4  

PbCr04  
PbCrO4  

Rb  

RbCl  

Rb 

RbCO3  
Rb2O  
Rb2SO4 

Rb  

Rb  
Rb  
RbCl 

Pb2O4  

Rb2PtCl6.... 

PbCrO4 

PbSO4  
Pb  
Mo. 

PbMoO4... 
PbMoO4 

RbCl   

Cl 

Rb2C03  
Rb2O  

RbHCOa.... 
RbCl    

PbMoO4  
PbO 

MoO3  .... 

PbCl2  .    . 

Rb2O  

Rb2S04  
RbCl  
Rb2CO3  

PbO  
PbO 

PbCO3  

RbPtCle  
RbPtCle  
RbPtCle. 

Pb  

PbO.. 
PbC  

PhO 

PbCl2  
PbCO3  
Fb(NOOi.... 
PbS04  
Pb  

RbHCO3.... 
Rb2O  

RbPtCle  

PbO 

S... 

BaSO4.  . 

7.2791 
1.0629 
3.0585 
2.7412 
1.8706 
2.4344 
6.4599 

0.1374 
0.9388 
0.3270 
0.3648 
0.5346 
0.4108 
0.1548 

PbS 

S  

S. 

H2S  
H2SO4 

PbS 

PbO 

PbS   . 

S  

S  
3  
S  
S  

FeS  
FeS2  
Na2S  
Pb. 

PbSO4  

BaSO4  

PbSO4 

Pb(C2H302)2 
•3H20 

AXA'=BandBxB'=A. 
*  Phenolphthalein. 


816 


TABLES   AND   USEFUL   DATA 
XVIII.— CONVERSION  FACTORS  (Continued) 


A 

B 

A' 

B' 

A 

B 

A' 

3.6567 
2.5622 
1.7296 
0.7727 
1.5975 
2.3495 

B' 

S... 

s  

SO2  

S02  
SO3  
BaSO4  

1.9978 
2.4967 
3.6430 
1.5783 
1.2812 
1.5309 
0.7655 
1.6244 
1.9677 
3.9360 
0.4255 
1.4255 
2.9155 
0.7003 
1.7003 
1.2250 
2.1765 

0.5036 
1.5036 
1.8858 
0.7743 
1.7743 
1.3146 
2.0162 
2.4298 
1.2625 
1.3683 

0.5005 
0.4005 
0.2745 
0.6336 
0.7805 
0.6532 
1.3064 
0.6156 
0.5082 
0.2541 
2.3504 
0.7015 
0.3430 
1.4280 
0.5881 
0.8163 
0.4595 

1.9859 
0.6651 
0.5303 
1.2915 
0.5636 
0.7607 
0.4960 
0.4116 
0.7921 
0.7309 

SiO2.  . 

K2SiF6 

0.2735 
0.3903 
0.5782 
1.2942 
0.6259 
0.4256 

SiO2  

K2Si03  
SiF4...    . 

SiO2  

SO2 

Ca(HSO3)2.  .  . 
H2SO3. 

SiO2  
SiO2 

SO3  
Si(OH)4 

SO2 

SO2* 

H2SO4. 

SiO2 

ZnSiO3 

so«t 

H2SO4  
NaHSO3  
NasSOs  
Na2SO3-7H2O 
A1203  
A12(S04)3.... 
BaS04  

SO2 

Sn 

C12 

0.5975 
1.5974 
1  .  7325 
2.1945 
1  .  1348 
1.2696 
0.3740 
0.3847 
1.0952 
1.0846 
0.5444 
0.5568 
1.4974 
1.7288 

2.4389 
0.8938 

1.6771 
0.6261 
0.5772 
0.4555 
0.8812 
0.7877 
2.6738 
2.6000 
0.9130 
0.9221 
1.8369 
1.7959 
0.6678 
0.5784 

0.4100 
1.1188 

SO2 

Sn  

Sn. 

SnCl2.. 
SnCl2-2H2O.. 
SnCl4  
SnO  
SnO2  
Cl 

SO2 

SO3 

Sn  
!Sn  
Sn  
SnCl2 

SO3 

SO3. 

SO3. 

CaO     

SO3. 

CaSO4   .  .  . 

SnCl2 

HC1  
Fe2O3  
SnCl2-2H2O.. 
Cl 

S03  
S03  
SO3. 

H2SO4  

SnCl2 

K2SO4  

SnCl2 

MgO(in 
MgS04) 
MgS04  
MnSO4  

SnCl4 

SO3 

SnCl4 

HC1 

SnO2. 

SnCl2-2H2O.. 
SnCl4 

SO3 

SnO2.  . 

SO3  
SO3. 

Na2O   

SnO2  

SnCl4 
(NH4C1)2 
SnO  

Na2SO4  

SnO2  

S03  
S03  
SO4 

66°  O.  V.... 
ZnSfh 

BaSO4  

Sr 

SrCCT3  
SrO. 

1.6848 
1.1826 
2.0963 
1.5300 
0.4357 

0.5935 
0.8456 
0.4770 
0.6536 
2.2943 

SO3-HC1.... 
S2O8C12. 

H2SO4  

Sr         

H2SO4  

Sr         

SrSO4 

SrO  
SrS04  

QrPl 

Sb  

Sb  
Sb  
Sb  
Sb  
Sb  
Sb2O3  

KSbOC4H406 
•|H20 

SbCl3  

2.7649 
.8850 
.1997 
.3328 
.4002 
.2662 
.1109 
.3462 

0.3617 
0.5305 
0.8336 
0.7503 
0.7142 
0.7897 
0.9001 
0.7428 

S03  

Ta. 

TaCl6  . 

1.9767 
1.2162 

0.5059 
0.8207 

Sb2O3  

Ta  

Ta2O5  

Sb205  
Sb2S3  
Sb2O4  

Te.. 

H2TeO4.  . 

1.5177 
1.8003 
1.2509 
1.3765 

0.6587 
0.5554 
0.7994 
0.7265 

Te  

H2TeO42H2O. 
TeO2  

Sb2O5  

Te  

Sb2S3  

SbCl3  

Te  

TeO3  

Se.. 

H2SeO3  

1.6315 
1.8336 
1.4040 
1.6060 

0.6129 
0.5454 
0.7123 
0.6227 

ThO3.. 
IThO2 

Th.. 
ThCl4 

0.8790 
1.4155 

2.2226 

1  .  1379 
0.7065 

0.4492 

Se 

H2SeO4  
SeO2  

Se.. 

Th02  

Th(N03)4 
•  6H2C 

Se  

SeO3  

Si.. 
Si 

SiO2.. 

SiO, 

2.1307 
1.2653 
1.5307 
2.6814 
1.3837 
2.1141 
1.0141 
4.6380 
1.2988 

0.4693 
0.7903 
0.6533 
0.3729 
0.7227 
0.4730 
0.9860 
0.2156 
0.7699 

|Ti     

TiO2  

1.6652 

0.6005 

Si 

SiO4 

Tl  . 

T1C1.  . 

1.1738 
1.1470 
1.622 
1.3040 
1.0392 
0.7786 
0.6775 

0.8519 
0.8718 
0.6165 
0.7669 
0.9623 
1.2843 
1.4759 

SiF4  
SiF4  

BaSiF6 

Tl  

T12CO3  

H2SiF6  
K2SiF6 

Tl  

Til  

SiF4 

Tl 

T1NO3  
T120  
Tl  .      .. 

SiF«.  . 

H2SiF6  

Tl  
Tl2CrO4 

SiO2 

BaSiFe 

SiOj.  .  . 

H2SiO3 

T1HSO4  

Tl  

AXA'=BandBXB'=A. 

*  Fhenolphtbalein.  t  Methyl  Orange. 


TABLES  AND  USEFUL  DATA 
XVIII.— CONVERSION  FACTORS  (Continued) 


817 


A 

B 

A' 

B' 

A 

B 

A' 

B' 

Til 

Tl 

0.6165 
0.5000 
0.5869 
0.5738 
0.8111 
0.6520 
0.5196 
0.6178 
0.8094 

1.6222 
1.9999 
1.7038 
1.7435 
1.2329 
1.5337 
1.9244 
1.6187 
1.6187 

WO3 

W 

0.7931 
1.9610 

1.2609 
0.5099 

Tl2PtCl6  

Tl 

WO3 

PbWO4 

TloPtOl* 

T1C1 

Tl2PtCl6  
Tl2PtCl6  
Tl2PtCl6  
Tl2PtCl6  
Tl2PtCl6  
T12SO4   

T12CO3  

Zn.     .  .     . 

H2SO4. 

1.5004 
1.4229 
2.0849 
1.2448 
2.3309 
1.4906 
2.1035 
0.5204 
0.8579 
1.2054 
0.9840 
1.6749 
1.5407 
1.^726 
1.1975 
1.9840 
3.5340 
2.3957 
2.9510 
0.4250 
0.4960 

0.6665 
0.8164 
0.4796 
0.8034 
0.4290 
0.6709 
0.4754 
1.9217 
1.1656 
0.8296 
1.0162 
0.5970 
0.6490 
0.5340 
0.8351 
0.5040 
0.2830 
0.4174 
0.3389 
2.3495 
2.0162 

Til  

Zn  
Zn  

S03  
ZnCl2 

T1NO3  

T12O  
T12S04  
Tl       

Zn  

ZnO     . 

Zn  

ZnP2O7  

Zn 

ZnS 

7nPl 

AgCl... 

UO2.  . 

U.  . 

0.8817 
0.8482 
0.9621 

1.7876 
0.6671 
0.7566 

1  .  1342 
1  .  1789 

1.0394 

0.5594 
1.4990 
1.3216 

ZnCl2 

U3O8 

u 

ZnCl2 

NaCl 

U3O8  

UO2  

ZnO.  . 

H2S04. 

U3O8  

U02(N03)2 
•6H20 

u 

ZnO  

SO3. 

U2P2OU 

ZnO  

ZnCl2  .    . 

ZnO 

ZnCO3 

U2P2On  

u62  

ZnO 

ZnP2O7 

ZnO  

ZnO 

ZnS  
ZnSO4 

V2O4.  . 

v. 

0.6024 
0.5604 
1.2638 

1.6276 
1.7843 
0.7913 

V2O5  

v  

ZnO 

ZnSO4-7H2O 
BaSO4 

V2O5  .... 

VO4  

ZnS. 

ZnS 

ZnSO4-7H2O 

SiO2 

Yb2O3.  . 

Yb.  . 

0.8775 
0.7876 

1  .  1396 
1.2697 

ZnSiO3 

Y2O3 

Y 

ZnSO4  

SO3  

W.. 
WO2  

PbWO4.  . 

3.4477 
0.8519 

0.2900 
1.1739 

ZrO2 

Zr 

0.7390 

1.3532 

W 

AXA'=B  and 

NOTE. — The  editor  will  welcome  additional  factors  not  appearing  in  these  tables. 
A  number  of  factors  appearing  in  this  list  were  taken  from  Van  Nostrand's  Chemical 
Annual.  Olsen.  1913. 

Example  of  Method  for  Using  Factors.  Suppose  the  product  weighed  is  0.8535 
gram  AgCl  and  the  equivalent  weight  of  Cl  is  desired;  hunt  up  the  factors  AgCl-Cl. 
This  may  be  found  on  the  first  page  of  the  conversion  fact9rs,  a  little  below  the  middle 
of  the  page.  Using  the  formula  A  X A'  =B,  and  substituting  the  values  for  A  (weight 
of  AgCl)  and  A'  (factor)  we  have  0.8535X0.2474  =  0.21124  gram  Cl.  If  on  the 
other  hand,  the  weight  of  Cl  were  known  to  be,  say,  0.2501  gram  and  the  weight  of 
the  equivalent  AgCl  were  desired,  we  would  use  the  formula  BXB'  =  A  and,  sub- 
stituting the  values  for  B  and  B't  we  would  have  0.2501  X 4.0423  =  1.01098  gram  AgCl. 

VOLUMETRIC  FACTORS 

1  cc.  N/2  HC1=. 018185  gram  HC1. 

1  cc.  N/10HC1=. 003637  gram  HC1. 

1  cc.  N/2  KOH=.028  gram  KOH. 

1  cc.  N/6  KOH=.047  gram  oleic  acid=. 008133  gram  H2SO4. 

1  cc.  N/10  KOH=  .0056  gram  KOH. 

1  co.  K2Cr2O7  3.8633  gram  per  liter  =.0038633  gram  K2Cr2O7=.010  gram  I. 

1  cc.  N/10  Na2S2O8+5H2O=.0248  gram  Na2S203-f  5H2O=. 01265  gram  I. 


818  TABLES   AND   USEFUL   DATA 

XIX.— COMPARISON  OF  CENTIGRADE  AND  FAHRENHEIT  SCALE 


°c. 

-100 

-0 

+0 

+  100 

+200 

+300 

+400 

+500 

+600 

+700 

+800 

+900 

°C. 

0 

-148 

F 

F 

F. 

F. 

F. 

F. 

F. 

F 

F 

F 

F. 

0 

+  32 

32 

+212 

392 

572 

752 

932 

1112 

1292 

1472 

1652 

5 

-157 

+  23 

41 

221 

401 

581 

761 

941 

1121 

1301 

1481 

1661 

5 

10 

-166 

+  14 

50 

230 

410 

590 

770 

950 

1130 

1310 

1490 

1670 

10 

15 

-175 

+  5 

59 

239 

419 

599 

779 

959 

1139 

1319 

1499 

1679 

15 

20 

-184 

-  4 

68 

248 

428 

608 

788 

968 

1148 

1328 

1508 

1688 

20 

25 

-193 

-  13 

77 

257 

437 

617 

797 

977 

1157 

1337 

1517 

1697 

25 

30 

-202 

-  22 

86 

266 

446 

626 

806 

986 

1166 

1346 

1526 

1706 

30 

35 

-211 

-  31 

95 

275 

455 

635 

815 

995 

1175 

1355 

1535 

1715 

35 

40 

-220 

-  40 

104 

284 

464 

644 

824 

1004 

1184 

1364 

1544 

1724 

40 

45 

-229 

-  49 

113 

293 

473 

653 

833 

1013 

1193 

1373 

1553 

1733 

45 

50 

-238 

-  58 

122 

302 

482 

662 

842 

1022 

1202 

1382 

1562 

1742 

50 

55 

-247 

-  67 

131 

311 

491 

671 

851 

1031 

1211 

1391 

1571 

1751 

55 

60 

-256 

-  76 

140 

320 

500 

680 

860 

1040 

1220 

1400 

1580 

1760 

60 

65 

-265 

-  85 

149 

329 

509 

689 

869 

1049 

1229 

1409 

1589 

1769 

65 

70 

-274 

-  94 

158 

338 

518 

698 

878 

1058 

1238 

1418 

1598 

1778 

70 

75 

-283 

-103 

167 

347 

527 

707 

887 

1067 

1247 

1427 

1607 

1787 

75 

80 

-292 

-112 

176 

356 

536 

716 

896 

1076 

1256 

1436 

1616 

1796 

80 

85 

-301 

-121 

185 

365 

545 

725 

905 

1085 

1265 

1445 

1625 

1805 

85 

90 

-310 

-130 

194 

374 

554 

734 

914 

1094 

1274 

1454 

1634 

1814 

90 

95 

-319 

-139 

203 

383 

563 

743 

923 

1103 

1283 

1463 

1643 

1823 

95 

100 

-328 

-148 

+212 

392 

572 

752 

932 

1112 

1292 

1472 

1652 

1832 

100 

°C. 

-200 

-100 

+  100 

+200 

+300 

+400 

+500 

+600 

+700 

+800 

+900 

+  1000 

°G 

1100   1200   1300 
2012   2192   2372 


1400   1500 
2552   2732 


1600   1700 
2912   3092 


1800   1900   2000 
3272   3452   3632 


Degrees  C.X  1.8 +32  =  Degrees  F.  Degrees  F.- 32 -7-1.8= Degrees  C. 

Absolute  zero,  -273°  C.  =  -459°  F. 


COMPARISON  OP  CENTIGRADE  AND  FAHRENHEIT  SCALE  FOR  EVERT  1°  C.  PROM 

0°  TO  100°  C. 


C. 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

C. 

F. 

F. 

F. 

F. 

F. 

F. 

F. 

F. 

F. 

F. 

0 

32 

50 

68 

86 

104 

122 

140 

158 

176 

194 

0 

1 

33.8 

51.8 

69.8 

87.8 

105.8 

123.8 

141.8 

159.8 

177.8 

195.8 

1 

2 

35.6 

53.6 

71.6 

89.6 

107.6 

125.6 

143.6 

161.6 

179.6 

197.6 

2 

3 

37.4 

55.4 

73.4 

91.4 

109.4 

127.4 

145.4 

163.4 

181.4 

199.4 

3 

4 

39.2 

57.2 

75.2 

93.2 

111.2 

129.2 

147.2 

165.2 

183.2 

201.2 

4 

6 

41.0 

59 

77 

95 

113 

131 

149 

167 

185 

203 

5 

6 

42.8 

60.8 

78.8 

96.8 

114.8 

132.8 

150.8 

168.8 

186.8 

204.8 

6 

7 

44.6 

62.6 

80.6 

98.6 

116.6 

134.6 

152.6 

170.6 

188.6 

206.6 

7 

8 

46.4 

64.4 

82.4 

100.4 

118.4 

136.4 

154.4 

172.4 

190.4 

208.4 

8 

9 

48.2 

66.2 

84.2 

102.2 

120.2 

138.2 

156.2 

174.2 

192.2 

210.2 

9 

C. 

9 

19 

29 

39 

49 

59 

69 

79 

89 

99 

C. 

100°  C.  =212°  F. 


TABLES   AtfD  USEFUL  DATA 


819 


XX.— RELATION  OF  BAUMfe  DEGREES  TO  SPECIFIC  GRAVITY  AND 
THE  WEIGHT  OF  ONE  UNITED  STATES  GALLON  AT  60°  F.— LIQUIDS 
LIGHTER  THAN  WATER 


. 

>> 

if 

.2  = 

TJ   C 

L 

U, 
%'> 

'•*•  rt 

ll 

1 

£ 

11 

Is 

. 

i 

fi 

« 

[J 

r/j 

go 

3 
rt 
« 

^ 
do 

30 

1 

f 

go 

I 

i° 

§0 

10 

1.0000 

8.33 

31 

0.8095 

7.24 

52 

0.7692 

6.41 

73 

0.6896 

5.75 

11 

0  .  9929 

8.27 

32 

0.8041 

7.20 

53 

0.7650 

6.37 

74 

0.6803 

5.62 

12 

0.9859 

8.21 

33 

0.8588 

7.15 

54 

0.7008 

6.34 

75 

0.0829 

5.09 

13 

0  9790 

8.10 

34 

0.8530 

7.11 

55 

0.7507 

0.30 

76 

0.6796 

5.06 

14 

0  .  9722 

8.10 

35 

0.8484 

7.07 

56 

0.7520 

6.27 

77 

0.6763 

5.63 

15 

0  .  9055 

8.04 

36 

0.8433 

7.03 

57 

0.7486 

6.24 

78 

0.6730 

5.60 

16 

0  .  9589 

7.99 

37 

0.8383 

6.98 

58 

0.7446 

6.20 

79 

0.0098 

5.58 

17 

0  .  9523 

7.93 

38 

0.8333 

6.94 

59 

0.7407 

6.17 

80 

O.OMO 

5.55 

18 

0  .  9459 

7.88 

i  39 

0  .  8284 

6.90 

60 

0.7308 

6,14 

81 

0.0035 

5.52 

19 

0  .  9395 

7.83 

40 

0.8235 

6.86 

61 

0.7329 

6.11 

82 

0.0604 

5.50 

20 

0.9333 

7.78 

41 

0.8187 

6.82 

62 

0.7290 

6.07 

83 

0.6573 

5.48 

21 

0.9271 

7.72 

42 

0.8139 

6.78 

63 

0.7253 

6.04 

84 

0.0542 

5.45 

22 

0.9210 

7.07 

1  43 

0  .  8092 

6.74 

64 

0.7216 

6.01 

85 

0.6511 

5.42 

23 

0.9150 

7.02 

44 

0  .  8045 

6.70 

65 

0.7179 

5.98 

86 

0.6481 

5.40 

24 

0  .  9090 

7.57 

45 

0  .  8000 

6.66 

66 

0.7142 

5.95 

87 

0.6451 

5.38 

25 

0  .  9032 

7.53 

46 

0.7954 

6.63 

67 

0.7106 

5.92 

88 

0.6422 

5.36 

20 

0  .  8974 

7.48 

47 

0.7909 

6.59 

68 

0.7070 

5.89 

89 

0.0392 

5.33 

27 

0.8917 

7.43 

48 

0.7865 

6.55 

69 

0.7035 

5.86 

90 

0.0303 

5.30 

28 

0.8800 

7.38 

49 

0.7821 

6.52 

70 

0.7000 

5.83 

95 

0.6222 

5.18 

29 

0  .  8805 

7.34 

50 

0.7777 

6  .  48 

71 

0  0905 

5  80 

30 

0  .  8750 

7  .  29 

51 

0.7734 

6.44 

72 

0.6930 

5.78 

XX.— (a)  RELATION    OF   BAUME   DEGREES   TO    SPECIFIC   GRAVITY- 
LIQUIDS  HEAVIER  THAN  WATER 


Baume 

D<;jm:<:.H. 

Specific 
Gravity. 

Baum4 

\)<-V.r<:<-». 

Specific 
Gravity. 

Baum6 

DIW-.'-.H. 

Specific 
Gravity. 

Baum£ 

1*<W.'*. 

Specific 
Gravity. 

0.0 

.0000 

6.0 

.0432 

24.0 

1.1983 

42.0 

1.4078 

0.1 

.0007 

7.0 

.0507 

25.0 

1.2083 

43.0 

.4216 

0.2 

00  1  4 

8.0 

.0584 

26.0 

1.2185 

44.0 

.4356 

0  .  3 

0021 

9.0 

.0662 

27.0 

1.2288 

45.0 

.4500 

0.4 

.  0028 

10.0 

.0741 

28.0 

1.2393 

46.0 

.4646 

0.5 

.  0035 

11.0 

.0821 

29.0 

1.2500 

47.0 

.4796 

0.0 

0042 

12.0 

.0902 

30.0 

1.2609 

48.0 

.4948 

0.7 

.0049 

13.0 

.0985 

31.0 

.2719 

49.0 

.5104 

0.8 

.0055 

14.0 

.1069 

32.0 

.2832 

50.0 

.5263 

0.9 

.0062 

15.0 

.1154 

33.0 

.2946 

51.0 

.5426 

1.0 

.0069 

16.0 

.1240 

34.0 

.3063 

52.0 

.5591 

1.5 

.0105 

17.0 

.1328 

35.0 

.3282 

53.0 

.5761 

2.0 

.0140 

18.0 

.1417 

36.0 

.3303 

54.0 

.5934 

2.5 

.0175 

19.0 

.1508 

37.0 

.3426 

55.0 

.6111 

3.0 

.0211 

20.0 

.1600 

38.0 

.3551 

50.0 

.6292 

3.5 

.0247 

21.0 

.1694 

39.0 

.3679 

57.0 

.6477 

4.0 

.0284 

22.0 

.1789 

40.0 

.3810 

58.0 

.  0007 

5.0 

1.0357 

23.0 

.1885 

41.0 

,3942 

59.0 

.6860 

60  0 

1.7059 

820 


TABLES  AND   USEFUL  DATA 


XXI— COMPARISON  OF  METRIC  AND  CUSTOMARY  UNITS  (U.  S.). 

Length 


1  millimeter,  mm.  =0.03937  inch. 

1  centimeter,  cm.  =0.39371  inch. 

1  meter,  m.  =3.28083  feet. 

1  meter  =  1.09361  yards. 

1  kilometer  =0.62137  (U.  S.)  mile. 


1  inch  =25.4001      millimeters. 
1  inch  =  2.54001    centimeters. 
1  foot  =  0.304801  meter. 
1  yard  =  0.914402  meter. 
1  mile  =  1.60935    kilometers. 


1  square  millimeter,  sq.mm. 

1  square  centimeter,  sq.cm. 

1  square  meter,  sq.m. 

1  square  meter 

1  square  kilometers 

1  hectare 


Areas 

=  0.00155  sq.in. 
=  0.1550  sq.in. 
=  10.764    sq.ft. 
=  1.196  sq.yd. 
=  0.3861  sq.mi. 
=  2.471  acres. 


1  sq.in. 
1  sq.in. 
1  sq.ft. 
1  sq.yd.  = 
1  sq.mi.  = 


645.16  sq.mm. 
6.452  sq.cm. 
0.0929  sq.m. 
0.8361  sq.m. 
2.5900  sq.km. 


1  acre     =     0.4047  hectare. 


Volumes 

1  cubic  millimeter,  cu.mm.  =  0.000061  in. 
1  cubic  centimeter,  cc.         =  0.06103  cu.in. 
1  cubic  meter  =35.314      cu.ft. 

=  61,028  cu.ins. 
1  cubic  meter  =  1.3079  cu.yd. 


1  cu.in.  =  16,387.2  cu.mm. 
1  cu.in.  =  16.3872  cc. 
1  cu.ft.  =  0.02832  cu.m. 

=  28. 32  liters. 
1  cu.yd.  =  0.7645  cu.m. 


Capacities 

1  cubic  centimeter,  cc.  =0.03381  (U.S.)  liquid  ounce.  1  ounce   =29.574  cc. 
1  cubic  centimeter        =0.2705  (U.  S.)  apothecaries' 

dram.  1  dram    =3.6967  cc. 
1  cubic  centimeter        =0.8115  (U.  S.)  apothecaries' 

scruple.  1  scruple  =  1 .2322  cc. 

1  liter  =1.05668  (U.  S.)  liquid  quarts.  1  quart    =0.94636  liter. 

1  liter  =0.26417  (U.  S.)  gallon.  1  gallon  =3.78543  liters. 

1  liter  =0.11351  (U.  S.)  peck.  1  peck      =8.80982  liters. 

1  hectoliter  =2.83774  (U.  S.)  bushels.  1  bushel  =0.35239  hectoliter. 


Masses 


1  gram  =  15.4324  grains. 

1  gram  =  0.03527  avoirdupois  ounce. 

1  gram  =  0.03215  troy  ounce. 

1  kilogram  =  2.20462  pounds  (av.) 

1  kilogram  =  2.67923  pounds  (troy). 


1  grain  =  0.06480  gram. 

1  ounce  (av.)    =28.3495  grams. 
1  ounce  (troy)  =31.10348  grams. 
1  pound  (av.)   =  0.45359  kilogram. 
1  pound  (troy)  =  0.37324  kilogram. 


Table  of  Equivalents,  U.  S.  Bureau  of  Standards.     For  British  Imperial  We 
and  Measures  see  Van  Nostrand's  Chemical  Annual. 

Avoirdupois  Weight 

The  system  of  weights  in  ordinary  use  by  which  common  or  heavy  articles 
are  weighed. 

16  drams     =1  ounce  =  28.35    grams. 

16  ounces    =1  pound  =453.59    grams. 

25  pounds  =1  quarter  =  11.34    kilograms. 

4  quarters  =  1  hundred  weight  =  45.359  kilograms. 
1  avoirdupois  pound  contains  7000  grains. 
1  avoirdupois  ounce  contains  437.5  grains. 


TABLES  AND  USEFUL  DATA  821 

Apothecaries'  Weight 

The  system  of  weights  employed  in  weighing  medicines. 

1  grain  =     0.0648  gram. 

20  grains     =1  scruple  =     1.296  grams. 
3  scruples  =  1  drachm  =     3.888  grams. 
8  drachms  =  1  ounce    =  31.103  grams. 
12  ounces    =1  pound   =373.236  grams. 
1  apothecaries'  (or  troy)  pound  contains  5760  grains. 
1  apothecaries'  (or  troy)  ounce  contains  480  grains. 

Fluid  Measure 

1  minim  =       .06161  cubic  centimeter. 

60  minims  =  1  fluid  drachm  =     3.696      cubic  centimeters. 

8  fluid  drachms  =  1  fluid  ounce    =  29.573      cubic  centimeters. 
16  fluid  ounces    =lpint  =473.179      cubic  centimeters. 

8  pints  =1  gallon  =     3.785      liters. 

1  gallon  contains  231  cubic  inches. 

The  minim,  fluid  drachm,  fluid  ounce  and  pint  are  the  fluid  measures  employed 
by  apothecaries. 


822 


TABLES  AND  USEFUL  DATA 


XXII.— A  TABLE  OF  CONSTANTS 

THE  UNITED  GAS 


All  Volumes  of  Gases  and  Vapors  are  given  at  60*  F.  and  30"  pressure. 


I. 

ii. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

HAMBOJT 

OA80R 
VAPOR. 

SYMBOL   OR 
FORMULA. 

Molecular  Weight. 

Sp.  Gravity  Gas  or 
Vapor  at  60°  F. 
Air  «=  1.0. 

Bolllng-polnt 
°Fahr. 

Sp.  Gravity  Liquid 
at  60°  F. 
Water  -1.0. 

Sp.  Heat  EQ.  Wts. 
at  Const.  Pr. 
Water  «•  1.0. 

Cubic  Feet  per 
Pound. 

Weight  1  Cubic 
Foot  In  Pounds. 

Heat  of  ( 

i 

fc«2 

Combustion. 


British 
Thermal 
Units. 

Calories  t 
Molecu 
In  Gran 

Per 
Cu. 

Ft. 

I1 

Carbon  to  CO 
Certron  to  COj 
Carbonic  Ox..  . 
Hydrogen  
Methane  
Ethane 

C 

c 

C( 
H 

• 

111 
&s»° 
||| 

iiJ 

«  «  a  < 

•<0&Q 

BOB  ip 

3    o 

Ciol 
Hi 
NI 
HC 
C»I 
C6 
CB 
CtH 
CC 
Hi 
BC 
O 
N 

> 

CH« 
CtHe 
CiH, 
CiHio 
CjHu 
CeHu 
CjH4 
Cilia 
CiHs 
CjHio 
CjHj 
CtH4 
CiH, 
CeH« 
C7Hi 
CiHio 

C.HH 

Ell 
8 
b 
N 

ii 

\t 

40 
60 

ta 

tO 

4 

12 
12 
28 
1 
16 
30 
44 
58 
72 
86 
28 
42 
66 
70 
26 
40 
54 
78 
92 
106 
120 
128 
34 
17 
27 
52 
76 
32 
46 
44 
18 
64 
16 
14 

0.8292 
0.8292 
0.9671 
0.0692 
0.5529 
1.0368 
1.5206 
2.0045 
2.4883 
2.9721 
0.9676 
1.4514 
1.9353 
2.4191 
0.8984 
1.3823 
1.8661 
2.6953 
3.1792 
3.6630 
4.1468 
4.4230 
1.1769 
0.5888 
0.9348 
1.8000 
2.6298 
1.1121 
1.5894 
1.5195 
0.6217 
2.2128 
1.1052 
0.9701 
1  0000 

15.749 
15.749 
13.503 
188.620 
23.626 
12.594 
8.587 
6.514 
6.248 
4.393 
13.495 
8.997 
6.747 
6.398 
14.534 
9.447 
6.998 
4.845 
4.107 
3.565 
3.149 
2.952 
11.096 
22.178 
13.968 
7.258 
4.965 
11.742 
8.216 
8.593 
21.004 
5.901 
11.816 
13.460 
13.059 

.06350 
.06350 
.07407 
.00530 
.04234 
.07940 
.11645 
.15350 
.19055 
.22760 
.07410 
.11115 
.  14820 
.  18525 
.06880 
.10585 
.  14290 
.20640 
.24345 
.28050 
.31755 
.33870 
.09012 
.04509 
.07159 
.  13779 
.20139 
.08516 
.  12172 
.11637 
.04761 
.16945 
.08463 
.07429 
.07658 

29.000 
96.960 
67.960 
68,360 
211.930 
370.440 
529,210 
687.190 
847.110 
999.200 
333.350 
492.740 
650.620 
807.630 
310.050 
467.550 

276.2 
923  5 
323.5 
326.2 
1009.0 
1764.4 
2521.0 
3274.0 
4035.6 
4759.8 
1588.0 
2347.2 
3099.2 
3847.2 
1476.7 
2227.1 

4.350 
14.544 
4.368 
61.523 
23.838 
22.226 
21.651 
21.326 
21.177 
20.914 
21,430 
21,120 
20.913 
20,767 
21.465 
21.040 



0.2450 
3.0490 
0.5929 



-  13« 

+  33° 
+  100° 
+  156' 

Butane  

6;  6273 
0.6640 

0.  4040 

Pent  ane  

Hexane  
Ethylene  
Propylene  
Butylene  
Amylene  
Acetylene  
Allylene 

+  23° 
+  102° 

6!65ii 



Crotonylene.  . 
Benzene  
Toluene 

+  64' 
+  177° 
+  230° 
+  287° 
+  326' 
+424.4° 

6'.  8846 
0.8720 
0.8692 

0.  3754 

799.350 
955.680 

1.282.310 

3807.5 
4552.0 

6108  !0 

18.447 
18.699 

19.235 

7,549 
9,598 
10.575 
8.986 
6.279 
10.250 
13.325 

Xylene  
Mesltylene..  .  . 
Naphthalene.  . 
Hydrogen  Bui. 
Ammonia  
Hydrocy.  acid. 
Cyanogen  .... 
Carbon  Bl-Sul. 
Methyl  Ale.... 
Ethyl  Alcohol. 
Carbonic  Acid. 
Water  
Sulphur  Dlox  . 
Oxygen  
Nitrogen  
Air 

i.isi? 

6.2423 
0.5083 

140.900 
90.560 
158,620 
259.620 
265.130 
182.230 
340,530 

672.2 
432.8 
757.0 
1238.2 
1264.6 
872.9 
1622.0 

+  114.8° 
+  131.2° 
+  172.9° 

+"2i2° 

6!  8027 
0.7946 

iioooo 

L4534 
0.2163 
0.4805 
0.1553 
0.2174 
0  2438 
0.2374 

.... 

AUTHORITIES  AND  METH 

In  Column  IX.  the  figures  given  In  Hempel's  "  Gas  Analysis,"  p.  375,  were  selected  for  the  fundamental  weight 
of  Oxygen,  Nitrogen,  Hydrogen,  Carbonic  Oxide  and  Air. 

The  formula  used  for  the  conversion  to  English  units,  Is — grams  per  liter  at  0°  C.  and  760  mm.  X  .05922 
-  pounds  per  cu.ft.  at  60°  F.  and  30"  pressure.  The  derivation  of  the  factor  employed  Is 


.05922  - 


28.316  X  .0022046  X  30.00  X  492 


29.92X520 
The  weights  of  the  compound  gases  are  calculated  from  these  data  by  Avogadro's  law. 


Column  IV.  Is  calculated  by  the  formula:  sp.gr- 


wt.  1  cu.  ft.  gas 


wt.  1  cu.ft.  air 


.  and  the  figures  thus  obtained  agree  with 


the  theoretical  formula:  sp.gr.- 


mol.  wt. 
28.04   ' 


TABLES  AND  USEFUL  DATA 


823 


FOR  CERTAIN  GASES  AND  VAPORS 

IMPROVEMENT  COMPANY 

The  Temperature  of  Products  of  Combustion  Is  reduced  to  18°  C.  -  64.4*  F. 


XIII. 

XIV. 

XV. 

XVI. 

XVII. 

XVIII 

XIX. 

XX. 

XXI. 

XXII. 

XXIII. 

XXIV. 

XXV. 

XXVI. 

Cu.  Ft.  per  Cu.  Ft.  of 
Combustible. 

Pounds  per  Pound  of  Combustible. 

Heat  of  Formation 
at  Const.  Pres. 

NAME  OF 

OA8  OR 
VAPOB. 

Req.  for 
Combus- 
tion. 

Products  of 
Combustion. 

Req.  for 
Combus- 
tion. 

Products  of  Combustion. 

ft 

Hi 

III 

|sa 

B.t.u. 

Air. 

4.785 
9.570 
2.393 
2.393 
9.570 
16.748 
23.925 
31.103 
38.280 
45.458 
14.355 
21.533 
28.710 
35.888 
11.963 
19.140 
26.318 
35.888 
43.065 
50.243 
57.420 
57.420 
7.178 
3.589 
6.981 
9.570 
14.355 
7.178 
14.355 

Oxy- 
gen. 

C02 

HzO. 

Air 

Oxy- 
gen. 

COs 

H*0 

Per 

Cu.  Ft. 

Per 
Pound. 

1.0 
2.0 
0.5 
0.5 
2.0 
3.5 
5.0 
6.5 
8.0 
9.5 
3.0 
4.5 
6.0 
7.5 
2.5 
4.0 
5.5 
7.5 
9.0 
10.5 
12.0 
12.0 
1.5 
0.75 
1.25 
2.0 
3.0 
1.5 
3.0 

2^0 
1.0 

i!o 
2.0 
3.0 
4.0 
5.0 
6.0 
2.0 
3.0 
4.0 
5.0 
2.0 
3.0 
4.0 
6.0 
7.0 
8.0 
9.0 
10.0 

i!o 

2.0 
1.0 
1.0 
2.0 

i!o 

2.0 
3.0 
4.0 
5.0 
6.0 
7.0 
2.0 
3.0 
4.0 
5.0 
1.0 
2.0 
3.0 
3.0 
4  0 
5.0 
6.0 
4.0 
1.0 
1.5 
0.5 

2^0 
3.0 

CO-2.0 

5  771 
11.541 
2.471 
34.624 
17.312 
16.156 
15.737 
15.520 
15.386 
15.295 
14.836 
14.836 
14.836 
14.836 
13.313 
13.850 
14.105 
13.313 
13.547 
13.720 
13.850 
12.984 
6.111 
6.111 
6.410 
5.323 
5.466 
6.492 
9.033 

1.333+ 
2.666+ 
.571 
8.000 
4.000 
3.733 
3.636 
3.586 
3.555 
3.534 
3.428 
3.428 
3.428 
3.428 
3.076 
3.200 
3.259 
3.076 
3.130 
3.170 
3.200 
3.000 
1.412 
1.412 
1.481 
1.230 
1.263 
1.500 
2.087 

CO-2.333+ 

Carbon  to  CO 
Carbon  to  COj 
Carbonic  Ox. 
Hydrogen 
Methane 
Ethane 
Propane 
Butane 
Pentane 
Hexane 
Ethylene 
Propylene 
Butylene 
Amylene 
Acetylene 
Allylene 
Crotonylene 
Benzene 
Toluene 
Xylene 
Mesltylene 
Naphthalene 
Hydrogen  Sul. 
Ammonia 
Hydrocy.  acid 
Cyanogen 
Carbon  Bl-Sul. 
Methyl  Ale. 
Ethyl  Alcohol. 
Carbonic  Acid 
Water 
Sulphur  DIox. 
Oxygen 
Nitrogen 
Air 

3.666  + 
1.571 

2!  750 
2.933 
3.000 
3.034 
3.055 
3.069 
3.142 
3.142 
3.142 
3.142 
3.384 
3.300 
3.259 
3.384 
3.348 
3.311 
3.300 
3.437 

L630 
1.692 
0.579 
1.375 
1.913 

9!660 
2.250 
.800 
.636 
.552 
.500 
.465 
.286 
1.286 
1.286 
1.286 
0.692 
0.900 
1.300 
0.692 
0.782 
0.849 
0.900 
0.563 
0.529 
1.588 
0.333 

l!i25 
1.174 

+138.4 

+1869.2 



+21,750 
+28,560 
+35,110 
+42,450 
+47.850 
+61.080 
-2.710 
+3.220 
+10,660 
+18.970 
-47,770 
-39.650 

+103.1 
+136.0 
+167.2 
+202.2 
+227.9 
+290.9 
-12.9 
+15.3 
+50.7 
+113.7 
-227.5 
-188.8 

+2435.6 
+1713.6 
+1436.3 
+1317.3 
+1196.2 
+1278.4 
-174.2 
+138.1 
+342.6 
+614.1 
-3300.7 
-1784.2 



'/.;'..; 





-12.510 
-3.520 

-47.3 
+16.7 

-229.3 
-68.8 



+490 

+2.3 

+7.3 

SOj-l.O 
N-0.5 
N-0.5 
N-1.0 
SOz-2.0 

SOa-  1.883 
N-0.823 
N-0.518 
N-0.538 
SO*-  1.684 

+4.740 
+11.890 
-27.480 
-65.700 
-26.010 
+51.450 
+58.470 

+22.6 
+56.7 
-131.1 
-313.2 
-124.0 
+248.4 
+278.5 
+463.1 
+327.  1 
+337.3 

+250.9 
+1259.0 
-1832.0 
-2273.9 
-616.0 
+2894.0 
+2288.0 
+3979.1 
+6870.4 
+1999.1 

ODS  OF  CALCULATION. 

Columns  V.  and  VI.  are  taken  chiefly  from  Lunge's  "  Coal  Tar  and  Ammonia." 
Column  VII.  Is  from  Ganot's  "  Physics."  edition  1896.  page  445. 

Column  X.  and  XXIII.  are  from  Julius  Thomson's   "  Thermochemical  Investigations,"  and  his  results  »re 
translated  Into  English  units  In  columns  XI.-XII.  and  XXIV.-XXV. 

Columns  XIII.  and  XVIII.  are  calculated  on  the  assumption  that 
air -20.9%  oxygen +79.1%  nitrogen  by  Volume. 
air -23. 13%  oxygen +76.87%  nitrogen  by  Weight. 


824 


TABLES   AND   USEFUL   DATA 
XXIII.— SOLUBILITY   TABLE 


Since  no  salt  is  absolutely  insoluble,  the  term  "  insoluble  "  is  only  relative.    For  solubility 
of  the  salts  formed,  see  Van  Nostrand's  Chemical  Annual,  edited  by  Professor  John  C.  Olsen. 


. 

V 

Vi 

q 

t 

5 

^ 

^ 

^ 

5 

^w 

/—  s 

V 

pi 

fa 

U 

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—  . 

U 

2 

6 
0 

u 

ch 

6 
u 

o 
c/5 

6 

U 

w*"c» 

O  O 

£ 

O 

C-D 

o 

O) 

z 
y^ 

"iT 

U 

>—  ^ 

2: 

CATION. 

—  ^— 

fa 

fa 

K- 

W 

W 

w 

w 

W 

W 

w 

w 

W 

w 

W 

w 

w 

w 

W 

W 

W 

W 

W 

w 

Na- 

W 

w 

w 

w 

w 

w 

w 

w 

W 

w 

W 

w 

w 

w 

W 

w 

w 

W 

w 

w 

Li- 

W 

w 

w 

w 

w 

w 

w 

w 

W 

w 

w 

w 

w 

w 

w 

w 

w 

w 

w 

w 

Ba" 

wa 

w 

w 

w 

wA 

w 

w 

w 

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A 

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wA 

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Sr- 

wa 

w 

w 

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w 

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Ca- 

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w 

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wa 

wA 

A 

A 

A 

A 

w 

W 

— 

Mg- 

wa 

w 

w 

w 

W 

w 

w 

wA 

w 

A 

A 

W 

W 

wA 

A 

A 

A 

w 

W 

— 

Al- 

W 

w 

w 

w 

— 

w 

w 

w 

— 

— 

wa 

W 

— 

A 

A 

A 

— 

— 

— 

— 

Mn- 

A 

w 

w 

w 

A 

w 

w 

wA 

A 

A 

A 

W 

W 

A 

A 

A 

A 

I 

A 

— 

Zn- 

wA 

w 

w 

w 

A 

w 

w 

w 

A 

A 

A 

W 

w 

A 

A 

A 

— 

A 

wa 

— 

Cr- 

W 

w 

w 

w 

A 

w 

w 

wA 

— 

— 

A 

W 

A 

A 

A 

A 

— 

— 

— 

— 

Cd- 

wA 

w 

w 

w 

A 

w 

w 

w 

A 

A 

A 

W 

W 

wA 

A 

— 

— 

— 

— 

— 

Fe" 

wA 

w 

w 

w 

wa 

w 

w 

w 

A 

A 

A 

W 

— 

A 

A 

A 

A 

I 

— 

Fe- 

W 

w 

w 

— 

— 

w 

w 

A 

— 



A 

W 

W 

A 

A 

A 

A 

W 

— 

Co" 

wA 

w 

w 

w 

wa 

w 

w 

w 

A 

A 

A 

W 

A 

A 

A 

A 

A 

I 

— 

Ni- 

wA 

w 

w 

w 

wa 

w 

w 

w 

A 

A 

A 

W 

A 

A 

A 

A 

A 

I 

— 

Sn- 

W 

w 

— 

w 

— 

w 

w 

A 

A 

— 

— 

W 

A 

A 

A 

— 

— 

I 

— 

Sn— 

W 

w 

— 

w 

— 

— 

— 

— 

A 

— 

— 

— 

— 

— 

A 

A 

A 

— 

— 

Pb" 

A 

w 

w 

w 

A 

w 

w 

w 

A 

A 

A 

I 

I 

A 

A 

A 

— 

wA 

A 

— 

Cu- 

A 

w 

w 

I 

I 

w 

w 

w 

A 

A 

— 

W 

W 

A 

A 

A 

A 

— 

I 

— 

Sb- 

W 

A 

A 

wA 

— 



— 

A 

A 

— 

— 

A 

A 

— 

A 

A 

— 

— 

— 

— 

Bi- 

W 

A 

A 

A 

— 

A 

w 

A 

A 

A 

A 

A 

A 

A 

A 

A 

— 

— 

— 

— 

Hg- 

— 

I 

I 

I 

— 

w 

w 

A 

— 

A 

— 

wA 

A 

— 

A 

A 

A 

— 

— 

— 

Hg" 

wA 

W 

W 

A 

W 

w 

w 

A 

A 

A 

— 

W 

wA 

— 

A 

A 

A 

— 

— 

Ag' 

W 

I 

I 

I 

I 

w 

w 

A 

A 

A 

A 

wA 

A 

A 

A 

A 

A 

A 

I 

— 

Pt— 

— 

w 

W1 

w 

I 

W 

w 

— 

— 

A 

— 

— 

W 

— 

— 

— 

— 

A 

— 

— 

— 

ABBREVIATIONS.  — W  =  soluble  in  water;  A  =  soluble  in  acids;  wA  =  slightly  soluble 
in  water,  readily  soluble  in  acids ;  wa  =  difficultly  soluble  in  water  and  in  acids ;  I  =  insol- 
uble in  water  and  acids. 

The  metals  are  arranged  in  order  of  their  electromotive  series. 


QUALITATIVE   TESTS 

OF 
SUBSTANCES 


QUALITATIVE  TESTS   OF   SUBSTANCES 

XXIV.— BLOWPIPE   AND   FLAME   TESTS   OF  SOLIDS 
Blowpipe  Tests  on  Charcoal 

Heat  a  small  portion  of  the  material  on  charcoal  in  the  reducing  flame,  using  a 
blowpipe.  Scoop  out  a  round  hole  in  the  charcoal,  place  a  little  of  the  substance 
in  the  cavity,  and  direct  the  inner  flame  of  the  blowpipe  against  it  at  an  angle  of 
thirty  degrees. 


RESULT  OF  TEST. 

Melts  and  runs  into  the  charcoal 
An  alkaline  residue  on  charcoal 
A  residue  which,  when  moistened  with  a  drop  of 
Co(NOs)3  and  heated  in  O.  F.,  produces  a  color 
which  is  blue 

Produces  a  color  which  is  green 

Produces  a  color  which  is  red 

Produces  a  color  which  is  pink  or  rose-red 
Deflagrates 
Leaves  an  incrustation  which  is  white  near  flame 

White,  garlic  odor 

Dark  red 

Red  to  orange 

Lemon  yellow  (hot),  light  yellow  (cold) 

Orange  yellow  (hot),  light  yellow  (cold) 

Yellow  (hot),  white  (cold) 


INFERENCE. 
Alkalies,  K,  Na,  etc. 
Ca,  Sr,  Ba,  Mg. 


Aluminum,  silicon. 
Zinc,  tin,  antimony. 
Barium. 
Manganese. 
Nitrates,  chlorates. 
Antimony. 
Arsenic. 
Silver. 
Cadmium. 
Lead. 
Bismuth. 

Zinc  or  tin,  latter  nonvola- 
tile. 


Blowpipe  Tests.  —  Substance  fused  with  Na2COa  on  Charcoal.  Place  a  small 
amount  of  the  substance  on  charcoal  with  a  little  sodium  carbonate,  and  fuse,  using 
reducing  flame. 


RESULT  OF  TEST. 
Metallic  globules,  without  incrustation 

Yellow  flakes 

Red  flakes 

White  globule,  moderately  soft 
Metallic  globules,  with  incrustation 

White,  moderately  soft  beads 

White,  brittle  beads 

Yellow  in  O.  F. 
Green  in  O.  F. 
A  substance  (in  R.  F.)  which,  when  moistened  and 

placed  on  a  silver  coin,  leaves  a  brown  or  black 

stain 


INFERENCE. 

Gold. 

Copper. 

Silver. 

Lead  or  tin  (volatilized 
lead  leaves  yellow  coat). 

Bismuth  or  antimony  (yel- 
lowish). 

Chromium. 

Manganese. 


Sulphur  compounds. 


827 


828 


TABLES   AND   USEFUL  DATA 


TEST. 

Dark  gray  magnetic  powder  which,  when  moistened 
on  a  filter  paper  with  a  drop  of  dil.  HC1  and  HN03, 
and  gently  dried  over  a  flame,  leaves  a  stain  which 
is  faint  pink,  turning  blue 
Green  stain,  turning  yellow 
A  stain  turned  blue  by  K4Fe(CN)6 


INFERENCE. 


Cobalt. 
Nickel. 
Iron. 


In  place  of  using  charcoal  the  above  tests  may  be  made  with  a  splinter  of 
wood  covered  with  a  coating  of  fused  Na2C03.  The  test  is  made  by  dipping  the 
heated  splinter  into  a  mixture  of  the  powdered  substance  with  fused  sodium 
carbonate  and  plunging  for  a  moment  in  the  reducing  flame.  Examine  the 
material  on  the  splinter,  scrape  off  on  a  piece  of  glazed  paper  and  examine. 

Blowpipe  Test.    Substance  moistened  with  cobalt  nitrate  solution  and  ignited. 


COLOR  OF  RESIDUE  OR  INCRUSTATION. 

Brick  red 

Pink 

Gray 

Yellowish  green 

Dark  muddy  green 

Bluish  green 

Blue 


INFERENCE. 


BaO 

MgO 

SrO,  CaO. 

ZnO 

Sb205 

SnO 

A1203,  Si02 


Flame  Test 

Flame  Test.  Moisten  a  platinum  wire  in  cone.  HC1,  dip  into  the  powdered 
substance  and  insert  into  a  Bunsen  flame.  If  sodium  is  prominent,  examine 
through  a  blue  glass.  (Test  the  cobalt  glass  to  see  if  it  is  effective  in  cutting  out 
the  yellow  sodium  light  by  examining  a  sodium  flame  through  it.) 


FLAME  COLOR.      COLOR  THROUGH  BLUE  GLASS. 


Carmine  red 

Dull  red 

Crimson 

Golden  yellow 

Greenish  yellow 

Green 

Blue 

Violet 


Purple 
Olive  green 
Purple 
Absorbed 
Bluish  green 


Violet  red 


ELEMENT. 
Lithium 
Calcium 
Strontium 
Sodium 

Barium,  molybdenum 
Cu,  -P04,  -B203, 
Cu,  Bi,  Pb,  Cd,  Zn,  Sb,  As 
Potassium 


The  platinum  wire  should  be  cleaned  before  making  the  test.  This  can  be  ac- 
complished by  dipping  it  into  cone.  HC1  and  holding  it  in  the  Bunsen,  or,  better, 
a  flame  of  a  blast  lamp,  until  the  flame  is  no  longer  colored.  Repeatedly  dipping 
into  the  HC1  may  be  necessary. 

Examine  the  flame  through  a  spectroscope,  if  available,  and  compare  the 
spectra  with  a  spectra  chart.  Mere  traces  of  the  alkali  and  alkaline  earth  metals 
can  be  detected  in  this  way  by  their  characteristic  spectral  lines. 


TABLES  AND   USEFUL   DATA 


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« 


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^  e 


t  g  I 

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ft  g  ^ 

S  ^  8 


«c    ^J 

••s     O 


••s 


0-2     rSJ 

^|l 

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s 


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Yellow 
or 
Brownis 


he  same  a 
cosmic  sal 


s 


i 


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TABLES  AND  USEFUL  DATA 


XXV.     TABLE  FOR  REVIEW  OF  THE  SEPARATE 
§  PbCI,    Tests  («)  +H2SO4=PbSO4  white.     (6)  +H2S=PbSbl; 

Add.raM1^''1''"1"1'11^1181'1'*- 
AgCl    J  I  Solution— (NH3)3(AgCl)2)  acidify  with 


PbCI,  (w) 
HgCl (w) 


HgS  (bk) 
PbS  (bk) 
Bi,S,  (br) 
C«2S  (bk) 
CuS  (bk) 
I  CdS  (y) 


Dissolve  in  nitrohydrochlc 


Pb(N03)2 
Bi(N03)3 
Cu(N03)2 


Al(OH),  (w) 
Cr(OH)3  (g) 

Fe(OH),  (r) 


Add  NH.C1  or  render  a 


Cr(OH)3    1      Fuse  on  platinum 
KN03  and  Na2CO3. 
Fe(OH)3    j      Extract  with  wate 


0- white;  (y)« yellow;  (o) -orange;  (br) -brown;  (bk)-bla 


TABLES  AND  USEFUL  DATA 

F  THE  METALS.     ANALYSIS  OF  THE  SOLUTION. 
i;)  +E2Cr04=PbCrO,  yellow,     (d)  +EI=PbI2  yellow. 


=AgCl  white. 


AsH3  gas 


SbH,  gas+Sb 


Eg"! 


H3AsO3  ]  Remove  AgNO3  with  CaCl2i  and  add  H2S  ( As»S3  Lemon  yellow. 

Gutzeit  Test — AsH3  colors  HgCl2  paper  a  deep  maroon. 

See  method  on  page  40. 
SbAg3   j  Dissolve  in  hot  HC1,  dilute,  filter  and  add  H^SbzS,  Orange. 


Sn 


<S 
SnCl2  } Test  with  HgCl2.     { HgCl,  White;  or  Hg  Gray. 

4.     SbCli  reject  or  test  in  Marsh  apparatus. 


Sb 
Au 
Pt 


SbCl5 
AuCl3 
PtCl4 


iAuC!3.  NH4C1     Evaporate  and 
ignite  to  Au°,  Yellow. 
(NH4)2PtCl«  Ignite  to  Pt°,  Gray. 


Blue  to  green-brown  \    Evaporate  to  dryness  with  excess  of  HNO3.     Dissolve  res.  in  NH4OH  and  add  to  an 
or  black  solution.   /  excess  of  HC1.    Test  this  sol.  with  Na2PHO< }  Ammonium  phosphomolybdate,  Yellow. 

1 1  and  test  with  (a)  SnCl2  =  White  HgCl  or  Gray  to  Black  Hg.     (6)  Au  wire  =  Hg  on  wire. 

|  by  formation  of  PbI2  or  PbCrO4.     See  Pb  above. 

!  (  -g.  Bi(OH)3    Add  hot  K2SnO2  pouring  over  ppt.  on  filter.  \  Bi  Black. 


Cu(OH)2.2NH4OH.2NH4NO3 
Cd(OH)22NH4OH.2NH4NO3 


Deep  blue  solution  evidence  of  copper. 

For  traces  add  HC2H3O2  and  test  with  Z4Fe(CN)6  {  Cu»Fe(CN)«  Red-brown. 

Add  KCN  till  blue  color  disappears,  then  HjSJ  CdS    Lemon-yellow. 


HC1  and  precipitate  with  (NH4)2CO3  { A1(OH)3    White,  gelatinous. 

h  f  Q  ,    (K2CrO4and 

1  W-  \    Na2Cr04 

Res.  Fe(OH)3 


Acidify  with  HC2H3O2  and  add  Pb(C2H3O2)2PbCrO4    Lemon-yellow. 
Dissolve  in  Hcl  and  add  KCNS  |  Fe(CNS)3    Blood  red.    Test  original  solution  (acid) 
with  KCNS  for  Fe'"  and  with  K3Fe(CN)6  for  Fe" { Fe3[Fe(CN)6]2    Blue, 


CoCl2 


NiCl2 


a.  Test  with  borax  bead.     Blue  bead.          c.  Or  evaporate  +H2SO4  and  add  nitroso-/3-naphthol. 
6.  Add  NaHCO3  and  H2O2,  Green  solution.  Co — Red  precipitate.    Test  with  borax  bead, 

a.  Test  with  borax  bead.     Brown  bead.       c.  Or  make  sol.  ammoniacal  and  add  1% 
6.  Heat  with  Br  /  wj/nTTN  \add  El.  alcoholic  sol.  nitrosobetanaphthol  = 

and  NaOH  \  NH°H^  f     Free  I  in  CS,.         [(CH3)2C2N2O2H]2Ni    Red. 


Mn(OH)2  {  Boil  with  pbO2  and  HNO3}HMnO4  ,  Purple. 

Na2ZnO2    {AddH2S}ZnS    White,    Ppt.  is  insoluble  in  dilute  acetic  acid. 


:-BaCrO4 


Dissolve  in  HCl  and  add  H2SO4{.BaSO4    White, 


I 

Ca(C2H302)2 


SrCO, 
CaC03 


Sr(C2H302)2 
Ca(C2H302)2 


1.  Add  CaSO4  set  aside  10  minutes  \  SrSO4  White. 
Moisten  SrSO4  with  HC1  and  applv  flame  test. 

2.  Add  E2SO4,  boil,  set  aside  ten  minutes. 


Precipitate  MgNH4PO4  White. 


•  E — Apply  flame  test  using  cobalt  glass.    Violet. 
•J  Na — Af ter  removal  of  Mg  apply  flame  test,  yellow. 

^  NIL, — To  the  original  solution  add  EOH  in  strong  excess,  warm  (note  odor)  and  test  with  moist  litmus 
paper;  pass  gas  into  Nessler's  reagent  EjHgL.  sol.  {  NHg2I,  Brown. 

)=red;  (g)=»green;  (pk)=pink.    Ppt.  =  precipitate.    Res.  =  residue.    Sol.  =  solution. 


432  TABLES  AND   USEFUL   DATA 

XXVI.— GENERAL   SUMMARY   OF    TESTS    FOR    ACIDS 


ACIDS. 


Acetates 
Arsenates 


Arsenites 
Bromides 

Borates 

Carbonates 

Chlorates 

Chlorides 
Chromates 


Cyanides 

Ferricyanides 
Ferrocyanides 
Fluorides 

Hypochlorites 
Iodides 

Nitrates 

Nitrites/ 

Oxalates 

Permanganates 

Phosphates 

Silicates 


Sulphates 

Sulphides 

Sulphites 

Sulphocyanides 

Thiosulphates 

Tartrates 

Organic  acids 


DETECTING  REAGENTS. 


H2SO4  (cone.) 

(a)  (NH4 

(b)  Magnesia  mixture 

(c)  Reduced  on  C  +  Na2CO3 

(a)  Magnesia  mixture 

(b)  H2S  +  HC1 

(a)  H2SO4  (cone.) 

(£)  Chlorine  water  +  CS2 
H2SO4  (cone.)  -f  alcohol 
Dilute  acids 
(0)  H2SO4  (cone.) 

(b)  Heated  alone 
AgNO3  +  HNO3 
(a)  H2SO4  (cone.) 
(J)  HC1 

(a)  Alcohol +  NaOH 

H2SO4  (cone.) 

FeSO4  +  HCl 
FeCl3  +  HCl 
H2SO4  (cone.) 

Dilute  acids 

(a)  H2SO4  (cone.) 

(£)  Chlorine  water -fCS2 

FeSO4  +  H2SO4  (cone.) 

Dilute  acids 

H2SO4  (cone.) 

Reducing  agents 

HN03  +  (NH4)2Mo04at4o0 

(a)  Fused  with  Na2CO8  and 

HC1  added 
(£)  HF 
HCl+BaCl2 
Dil.  acids 
Dilute  acids 
FeCl3 

Dilute  acids 
Ignited 
Heated 


REACTIONS  RESULTING  FROM  TEST. 


Odor  of  vinegar 

Yellow  precipitate 

White  granular  precipitate 

Garlic  odor,  arsenic  mirror 

No  reaction 

Yellow  precipitate 

Red  Br  vapor 

Reddish  color,  due  to  Br 

Green  flame 

CO2  evolved.     Limewater  test 

Explosive  liberation  of  Cl  +  C1O4 

O  given  off 

White  precipitate,  sol.  inNH4OH 

O  liberated  (sol.  yellow  to  green) 

Chlorine  of  HC1  liberated 

Reduced  and  Cr(OH)3  precipi- 
tated 

HCN  (POISON).  Odor,  bitter 
almonds 

TurnbulFs  blue  precipitate 

Prussian  blue  precipitate 

HFgas  liberates  silicic  acid  from 
glass  rod  with  drop  of  H2O 

Cl  liberated,  yellow  gas 

Violet  vapor  of  iodine 

Violet  color  to  CS2 

Brown  ring 

N2O3  brown  evolved 

CO +  CO2  evolved 

Decolorized 

Yellow  precipitate 

Silicic  acid  precipitated 

SiF4  gas  liberated 

White  precipitate  of  BaSO4 

H2S  gas  blackens  Pb(C2H8O2)j 

SO2  gas 

Deep  red  color 

SO2  gas  +  free  S 

Char.     Odor  of  burnt  sugar 

Generally  char. 


1  Nitrites  +  KI  -f  CS,  =  violet  color  in  CSa  due  to  free  I. 


TABLES  OF  REACTIONS 
BASES  AND  ACIDS 


833 


834 


TABLES   AND   USEFUL   DATA 


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TABLES   AND   USEFUL   DATA 


The  Soluble  H2S 


ARSENIC,  As'",  As  

ANTIMONY,  Sb*",  Sb  

(ous)  K3As03. 

(ic)  KH2As04. 

(ous)  SbCl3. 

(ic)  KSbO,. 

Hydrogen 
sulphide, 
H2S. 

Arsenic  trisul- 
phide,  As2S3, 
yellow  ppt.  Sol. 
in  alkalies, 
(NH4)2SX, 
(NH4)2S.  Insol. 
in  cone.  HC1. 

Arsenic  trisul- 
phide  +  S. 
As2S3  +  S2,  yel- 
low.    The  ppt. 
forms  slowly  by 
heat. 

Antimony  trisul- 
phide,  Sb2S3, 
orange  ppt.  Sol. 
in  alkalies, 
(NH4)2SX, 
(NH4)2S,  HC1 
(cone.),  o.i/mg. 

Antimony  penta- 
sulphide,  Sb2S5, 
orange  ppt.    Sol. 
in  alkalies, 
(NH4)2SX, 
(NH4)2S,  HC1 
(cone.). 

Ammonium 
hydroxide, 
NH4OH. 

Antimonious 
hydroxide, 
Sb(OH)3,  white 
ppt.    Sol.  in 
excess. 

Ammonium 
metantimonate, 
NH4SbO3. 
Very  slightly 
sol.  in  excess. 

Copper  sul- 
phate, 
CuSO4. 

Copper  arsenite, 
CuHAsO8,  yel- 
lowish green 
ppt.    Sol.  in 
NH4OH,NaOH, 
HN03. 

Copper  arsenate, 
Cu3(AsO4)2, 
greenish  blue 
ppt.     Sol.  in 
NH4OH  and  in 
HN03. 

Antimony  oxy- 
chloride,  white, 
SbOCl,  caused 
by  dilution. 
Insol.  alk. 
Sol.  HC1,  CS2. 

Copper  antimo- 
nate,  brown  ppt 

Mercuric 
chloride, 
HgCl2. 

Mercuric  arse- 
nite,Hg3(AsO3)2, 
white  ppt.    Sol. 
in  acids. 

Antimony  oxy- 
chloride,  caused 
by  dilution. 
Sol.  in  cone. 
HC1. 

Silver  ni- 
trate, AgNO3. 

Silver  arsenite, 
Ag3AsO3,  yel- 
low ppt.  Sol.  in 
HN03,  NH4OH, 
HC2H3O2. 

Silver  arsenate, 
Ag3AsO4,  red- 
dish brown  ppt. 
Sol.  in  HNO3 
and  NH4OH. 

Silver  chloride 
and  antimony 
trioxide, 
AgCl-f  Sb2O3, 
•white  ppts. 

Silver  antimo- 
nate,  Ag2SbO3, 
white  ppt.    Sol. 
in  NH4OH. 

Miscellany. 

Magnesia  mix- 
ture.    No  ppt. 
Arsenic  sol.  in 
HNO,,  Cl«, 
HjO,    aq.    reg., 
hot  alkalies. 

Marsh  test 
(Zn  +  HCl,etc.) 

Magnesia  mix- 
ture ppts. 
MgNH4AsO4, 
white  crys.  ppt. 
Sol.  in  acetic 
acid. 
AsH3  flame  de- 
posits arsenic. 
Sol.  in  NaOCl. 
Sol.in(NH4)2S. 
Residue  insol.  in 
HC1  (cone.). 

KOH  ppts. 
Sb(OH)3. 
Na2CO3  ppts. 
Sb(OH)3. 

Marsh  test 
(Zn  +  HCl). 

Sb.  sol.  in  hot 
cone.  H2SO4 
and  in  aq.  reg. 

SbH3  in  flame 
deposits  anti- 
mony.   Insol.  in 
NaOCl. 

•  See  Van  Nostrand's  Chemical  Annual  for  solubility  of  salts. 


TABLES   AND   USEFUL   DATA 


839 


Subgroup. 


TIN,  Sn",  Sn'—  . 

PLATINUM,  Pt"". 

GOLD,  Au"% 

(ous)  SnC^. 

(ic)  SnCl4. 

PtCl4. 

Audi. 

Stannous  sulphide, 
SnS,  dark  brown. 
Sol.  in  alkalies. 
Difficultly  sol.  in 
(NH4)2SX.     Sol.  in 
HC1  (cone.).  100  c.c. 
H2O  diss.  0.002  mg. 

Stannic  sulphide, 
SnS2,  yellow  ppt. 
Sol.  in  alkalies, 
(NH4)2SX,(NH4)2S 
and    alkali    carbon- 
ates.    HC1  (cone.). 
H2O  =  o.o2  mg. 

Platinic  sulphide, 
PtS2,  dark  brown 
ppt.     Difficultly 
sol.  in  alkali  sul- 
phides.    Sol.  in 
aqua  regia.     Insol. 
in  HC1  (cone.). 

Gold  sulphide, 
Au2Ss,  black  ppt. 
Sol.  in  alkali  sul- 
phides, aqua  regia. 
Insol.  in  HC1 
(cone.). 

Stannous  hydroxide, 
SnO(OH)2         Insol. 
in  excess.     Darkens 
on  cooling.   Insol.  in 
H2O.    Sol.  in  dilute 
acids,  alk. 

Stannic  hydroxide, 
Sn(OH)4.    Slightly 
sol.  in  excess. 

Ammonium  chlo- 
roplatinate, 
(NH4)2PtCl6,  yel- 
low ppt.     Sol.  in 
large  excess. 
6792°°  mg. 

Fulminating  gold, 
Au2O3.  2  NH3,  yel- 
low ppt.,     Insol.  in 
excess. 

Cuprous  chloride, 
2  CuCl,  white  ppt. 
Sol.  in  acids. 
Reduction  by  SnCl2. 

Mercurous  chloride, 
HgCl,  white  ppt. 
Insol.  in  cold 
HC1  (cone.). 
Reduction  by  SnCl2. 

Silver  chloride  and 
silver,  AgCl  +  Ag. 
Reduction  by  SnCl2. 

Silver  chloride, 
AgCl. 

Silver  chloride  and 
platinum  oxide, 
AgCl  +  PtO, 
brown  ppt. 

Silver  chloride  and 
gold  oxide, 
AgCl  +  Au2O3, 
brown  ppt. 

KOH  ppts.  Sn(OH)2, 
Na2CCh  ppts. 
Sn(OH)2.     Insol.  in 
excess. 

Metallic  Sn  depos- 
ited by  Zn  in 
Marsh  test. 

KOH  ppts. 
Sn(OH)2.     NaCO3 
ppts.  Sn(OH)2. 
Insol.  in  excess. 

Stannic  salts 
reduced  by  H,  gen- 
erated by  Sn. 

KOH  ppts. 
K2PtCl6.    Na2CO3 
gives  no  ppt. 
Pt  sol.  in  aq.  r., 
fused  alk. 

Zn  ppts.  Pt,  black, 
from  its  salts. 
Also  see  Electro- 
motive Series,  p.  10. 

SnCl2  solution 
ppts.     "  Purple  of 
Cassius,"  red  ppt. 
Au  sol.  in  KCN, 
aq.  reg. 

Zn  ppts.  Au  from 
its  salts. 

840 


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General  References 

Allen,  A.  H.,  Organic  Analysis,  v.  1-8,  4th  Ed.,  1909-1913.    P.  Blakiston's  Son  &  Co. 
Arnold  and  Mandel,  Compendium  of  Chemistry.     John  Wiley  &  Sons,  New  York. 

Authenrieth,  W.,  and  Warren,  W.  H..  Laboratory  Manual  for  the  Detection  of  Poisons. 
P.  Blakiston's  Son  &  Co.,  Philadelphia,  Pa. 

Baskerville,  C.,  and  Curtman,  L.  J.,  Quantitative  Analysis,  1910.    The  Macmillan  Co. 

Blair,  A.  A.,  The  Chemical  Analysis  of  Iron,  7th  Ed.,  1912.    Lippincott  &  Co.,  Phila- 
delphia, Pa. 

Brearly,  H.,  and  Ibbotson,  F.,  The  Analysis  of  Steel  Works  Materials,  1902.    Long- 
mans, Green  &  Co.,  London  and  New  York. 

Browning,  P.  E.,  Introduction  to  the  Rarer  Elements,  3d  Ed.,  1914.    John  Wiley 
&  Sons,  New  York. 

Cahen,  E.  and  Wootton,  W.  O.,  The  Mineralogy  of  Rarer  Metals,  1912.    J.  B.  Lippin- 
cott Co. 

Carins,  F.  A.,  Quantitative  Chemical  Analysis,  3d  Ed.,  1896.    H.  Holt  &  Co.,  New 
York. 

Clowes  and  Coleman,  Quantitative  Analysis,  5th  Ed.     P.  Blakiston's  Sons  &  Co. 

Classen,  A.,  Quantitative  Analysis.     Translated   by  N.  H.  Harriman,  1902.     Geo. 
Wahr,  Pub.,  Ann  Arbor,  Mich. 

Comey,  A.  M.,  Dictionary  of  Chemical  Solubilities.     Macmillan  &  Co. 

Crookes,  W.,  Select  Methods  in  Chemical  Analysis,  4th  Ed.,  1905.    Longmans,  Green 
&  Co.,  New  York,  London. 

Dennis,  L.  M.,  Gas  Analysis.    Macmillan  &  Co.,  New  York. 

Fresenius,  K.   M.,   Quantitative  Chemical  Analysis,  6th  Ed.    Translated  by  A.  I 
Cohn,  1911.    John  Wiley  &  Sons,  New  York. 

Fulton,  C.  M.,  FirelAssaying,  2d  Ed.,  1911.    McGraw-Hill  Co.,  New  York. 

Furman,  H.  Van  F.,  Practical  Assaying,  5th  Ed.,  1901.    John  Wiley  &  Sons,  New 
York. 

Gardner,  H.  A.,  Paint  Technology  and  Tests,  1911.    McGraw-Hill  Book  Co.,  New  York. 

Gardner,  H.  A.,  and  Schaeffer,  J.  A.,  Analysis  of  Paints  and  Painting  Materials,  1911. 
McGraw-Hill  Book  Co.,  New  York. 

Gill,  A.  H.,  Gas  and  Fuel  Analysis  for  Engineers,  3d  Ed.,  1903.    J.  Wiley  &  Sons, 
New  York. 

Gill,  A.  H.,  A  Short  Hand-book  of  Oil  Analysis,  6th  Ed.,  1911.    J.  B.  Lippincott  Co., 
Philadelphia  and  London. 

Gooch,  F.  A.,  Methods  in  Chemical  Analysis,  1912.    John  Wiley  &  Sons,  New  York. 
Hempel,  W.,  Gas  Analysis.    Macmillan  &  Co.,  New  York. 

HUlebrand,  W.  F.,  The  Analysis  of  Silicate  and  Carbonate  Rocks,  Bull.  422,  U.  S.  Geo- 
logical Survey,  1910.    Washington  Gov.  Print.  Office. 

Johnson,  C.  M.,  Rapid  Methods  for  the  Chemical  Analysis  of  Special  Steels.  2d  Ed., 
1914.    John  Wiley  &  Sons,  New  York. 

Julian,  F.  A.,  Text  Book  of  Quantitative  Analysis,  1902.    Ramsey  Publishing  Co.. 
St.  Paul,  Minn. 

Langbein,  Electro  Deposition  of  Metals. 


TABLES  AND  USEFUL  DATA  857 

Leach,  A.  E.,  Food  Inspection  and  Analysis,  3d  Ed.,  1913,  John  Wiley  &  Sons,  New 
York. 

Levy,  §.  I.,  The  Rare  Earths,  1915.     Edward  Arnold  Pub. 

Lewkowitsch,  J.,  Chemical  Analysis  of  Oils,  Fats,  Waxes,  1913-1916.   The  Macmillan  Co. 

Liddell,  Metallurgists  and  Chemists'  Handbook. 

Low,  A.  H.,  Technical  Methods  of  Ore  Analysis,  7th  Ed.,  1914.     John  Wiley  &  Sons, 
New  York. 

Lunge,  G.,  The  Manufacture  of  Sulphuric  Acid  and  Alkali,  4th  Ed.,  1913.     Van  Nos- 
trand  Co.,  New  York. 

Lunge,  G.,  Technical  Methods  of  Chemical  Analysis.     Trans.  Edited  by  Chas.  A. 
Keane.     Gurney  &  Jackson,  London.     D.  Van  Nostrand  Co.,  New  York. 

Mead,  R.  K.,  Portland  Cement,  2d  Ed.,  1911.     The  Chemical  Pub.  Co.,  Easton,  Pa. 
Ibid.,  Chemists'  Pocket  Manual,  The  Chemical  Pub.  Co.,  Easton,  Pa. 

Mellor,   J.  W.,  Treatise  on  Quantitative  Inorganic  Analysis,   1913.    Chas.  Griffin 
&  Co.,  Ltd.,  London. 

Olsen,  J.  C.,  Quantitative  Chemical  Analysis,  5th  Ed.,   1916.     D.  Van  Nostrand 
Company,  New  York. 

Perkin,  F.  M.,  Electro  Chemistry.     Longmans,  Green  &  Co.,  London  and  New  York. 

Prescott,  A.  B.,  and  Johnson,  O.  C.,  Qualitative  Chemical  Analysis,  7th  Ed.,  1916. 
Revised  by  J.  C.  Olsen.     D.  Van  Nostrand  Co.,  New  York. 

Rhead,  E.  L.,  and  Sexton,  A.  H.,  Assaying  and  Metallurgical  Analysis,  2d  Ed.,  1911. 
Longmans,  Green  &  Co.,  London  and  New  York. 

Rogers,  A.,  Manual  of  Industrial  Chemistry,  2d  Ed.,  1915.     D.  Van  Nostrand  Co. 
Roscoe,  H.  E.,  and  Schorlemmer,  C.,  Treatise  on  Chemistry,  1911.     Macmillan  &  Co. 
Scott,  W.  W.,  Qualitative  Analysis,  3d  Ed.,  1918.    D.  Van  Nostrand  Co.,  New  York. 
Segerblom,  W.,  Tables  of  Properties.     Exeter  Book  Pub.  Co.,  Exeter,  N.  H. 

Seidell,  A.,  Solubilities  of  Inorganic  and  Organic  Substances,  1911.     D.  Van  Nos- 
trand Co.,  New  York. 

Smith,  E.  F.,  Electro-analysis.    P.  Blakiston's  Son  &  Co. 

Stillman,  T.  B.,  Engineering  Chemistry,  5th  Ed.,  1916.     The  Chemical  Publishing  Co., 
Easton,  Pa. 

Sutton,  F.  A.,  Systematic  Handbook  of  Volumetric  Analysis,  10th  Ed.,  1911.     P, 
Blakiston  &  Sons,  Philadelphia. 

Talbot,  H.  P.,  An  Introductory  Course  in  Quantitative  Chemical  Analysis,  1899. 
Macmillan  &  Co.,  New  York. 

Thorpe,  E.,  A  Dictionary  of  Applied  Chemistry,  Five  Volumes,  1913.     Longmans, 
Green  &  Co.,  London  and  New  York. 

Treadwell,  E.  P.,  Analytical  Chemistry.    Translated  by  W.  T.  Hall,  4th  Ed.,  1914, 
J.  Wiley  &  Sons.,  New  York. 

Van  Nostrand's  Chemical  Annual.    Edited  by  J.  C.  Olsen,  3d  Issue,  1913.    D.  Van 
Nostrand  Company,  New  York. 

White,  C.  H.,  Methods  in  Metallurgical  Analysis,  1915.     D.  Van  Nostrand  Co.,  New 
York. 

Wiley,  H.  W.,  Principles  and  Practice  of  Agricultural  Analysis,  1914.     The  Chemical 
Pub.  Co.,  Easton,  Pa. 


APPENDIX 

ANALYSIS   OF   BRASS-DETERMINATION   OF  ARSENIC  AND 

CADMIUM 

Distillation  Method  for  Determination  of  Arsenic  in  Brass.  If  arsenic  ia 
present  in  amounts  less  than  0.10  per  cent,  100  gram  sample  is  taken  and  dis- 
solved in  400  cc.  HN03  (sp.  gr.  1.42).  The  fumes  are  expelled  by  boiling  and 
the  solution  diluted  with  water  to  500  cc.  NH4OH  is  added  until  a  slight  pre- 
cipitate of  copper  hydroxide  forms;  about  5  grams  of  Fe2(SO4)3  and  just  enough 
NH4OH  to  cause  precipitation  are  added,  the  solution  diluted  to  1000  cc.  and 
boiled.  Then  again  diluted  and  the  precipitate  allowed  to  settle  several  hours. 
The  clear  solution  is  decanted  off  and  the  Fe(OH)3  containing  all  the  arsenic  and 
antimony  is  washed,  dissolved  in  hot  HC1,  about  2  cc.  of  hypophosphorous  acid 
added  and  the  arsenic  distilled  according  to  the  procedure  described  on  page  34, 
omitting  the  addition  of  Cu2Cl2.  Arsenic  may  now  be  determined  in  the  distillate 
either  as  AszSs  or  by  titration  with  iodine  (see  pages  36  and  39). 

If  antimony  is  desired  in  the  analysis  it  may  be  obtained  in  the  residue  re- 
maining in  the  flask  (see  page  23). 

Dr.  Price  recommends  treating  the  sulphides  with  CS2  to  remove  any  free 
sulphur  that  may  be  present.  ("  Technica  Analysis  of  Brass,"  pages  225-227.) 

If  arsenic  is  present  in  amounts  over  0.10  per  cent,  5  grams  of  the  alloy  are 
dissolved  in  20  cc.  HN03  (sp.  gr.  1.42)  and  then  evaporated  with  15  cc.  H2SO4 
(sp.  gr.  1.84)  to  fumes.  Concentrated  HC1  may  now  be  added,  together  with 
2  cc.  30%  hypophosphorous  acid  and  the  arsenic  distilled  and  determined  as 
outlined  above. 

Determination  of  Cadmium  in  Brass.  Ten  grams  of  drillings  are  dissolved 
in  HN03  (sp.  gr.  1.42),  50  cc.  H2S04  (sp.  gr.  1.84)  added  and  the  mixture  evapor- 
ated to  fumes.  The  cooled  mixture  is  diluted  to  200  cc.  with  water  and  boiled. 
The  precipitate  is  allowed  to  settle  (several  hours)  and  filtered  off.  The  solution 
containing  the  cadmium  is  treated,  boiling  hot,  with  H2S  for  thirty  minutes,  the 
precipitated  sulphides  filtered  off  and  washed  with  hot  water.  The  precipitate 
is  dissolved  in  400  cc.  of  10  per  cent  H2S04. 

After  boiling,  the  hot  solution  is  filtered,  cooled  and  treated  with  H2S  for  ten 
minutes.  NH4OH  is  added  cautiously  until  ZnS  begins  to  precipitate.  The 
solution  is  again  treated  with  H2S  for  about  five  minutes,  whereupon  CdS  is 
completely  precipitated.  The  sulphide  is  purified  by  redissolving  in  100  cc.  of 
10  per  cent  H2SO4,  applying  heat.  The  solution  is  filtered,  diluted  to  300  cc. 
and  again  treated  with  H2S.  Ammonia  is  added  drop  by  drop  until  the  cadmium 
sulphide  is  completely  precipitated.  The  treatment  is  repeated  to  remove  traces 
of  impurities  and  the  CdS  then  weighed  in  a  tared  Gooch  crucible  after  drying 
for  two  hours  at  110°  C. 

Weight  CdS  X0.778=  weight  of  cadmium. 

NOTE.— Details  of  the  procedure  for  determining  minute  amounts  of  cadmium  (less 
than  0.01  per  cent)  may  be  found  in  Price  and  Mead,  '•  Technical  Analysis  of  Brass," 
2d  Ed.,  page  232,  John  Wiley  &  Sons,  Publishers. 

858 


INDEX 


859 


INDEX 


SUBJECT    INDEX 


Absorption  bulbs: 
carbon  dioxide,   Fleming,   Geissler,   Ger- 

hardt,  Liebig,  Vanier,  95,  98 
gas  analysis,  Friedrich,  Hanjkus,  Nowicki- 

Heinz,   Varrentrapp,  Winkler,  Wolff, 

693 
Absorption  spectrum,  carbon  monoxide  in 

air,  730 

Accuracy  in  methods  of  gas  analysis,  707 
Accuracy,  limit  of,  in  alloy  analysis,  659 
Acetate  extraction  of  lead,  235,  241 
Acetic  acid,  complete  analysis  of  acetone, 
formic    acid,    furfurol,    hydrochloric 
acid,  metals,  sulphuric  acid,  sulphur- 
ous acid,  527-529 

determination  in  corroded  white  lead,  626 
method  for  nitrite,  292 
Acetyl  value  for  oils,  591 
Acetylene  flame,  temperature  of,  780 
Acid  extraction  of  rare  earth  ores,  114 
extraction  of  silicates,  369 
reagent  for  calcium  carbonate  in  cement, 

656 

Acidimetric   and   alkalimetric   methods   for 
metabisulphites,    sulphites,    sulphurous 
acid,  411 
Acid  number,  Chinese  wood  oil  (Tung  oil), 

613 

general  tests.    See  Oils, 
varnish,  618 
Acids,  chapter  on,  499 
analysis  of  acetic.    See  subject  above,  527 
citric  acid,  530 

hydrochloric,    determination    of    total 
acidity,    arsenic,    barium   chloride, 
chlorine,  nitric  acid,  sulphuric  acid, 
silica,  total  solids,  509,  510 
hydrofluoric,  determination  of  acidity, 
hydrofluosalicic  acid,  sulphuric  acid, 
sulphurous  acid,  510-512 
nitric,    determination   of,    acidity,   free 
chlorine,  hydrochloric  acid,  iodine, 
nitric  and  nitrous  acids,  non- volatile 
solids,  sulphuric  acid,  512,  515 
procedure  for  determining,  in  arsenic 
acid,  ferrous  sulphate  method,  519 
in  oleum  and  mixed  acids,  518 
in  phosphoric  acid,  519 
in  sulphuric  acid,  517 


Acids,  analysis    of  nitrous,    permanganate 

titration  of,  520 

oleum  and  mixed  acids,  complete  anal- 
ysis, determination  of  total  acidity, 
lower  oxides,  nitric  acid,  sulphuric  acid 
and  free  SOs,  calculations,  table,  522- 

5-26'  -A 

arsenic  in  acids,  43 

formulae  for  diluting  or  strengtheningpf,525 

free  acids  in  aluminum  salts,  estimation  of, 

12 

in  aluminum  salts,  test  for,  13 
in  presence  of  iron  salts,  estimation  of, 

530 

indicators  for  determination  of,  499 
number  in  oil  analysis.     See  Oils, 
standards,  preparation  of  benzoic,  hydro- 
chloric, sulphuric,  501-504 
test  for  in  animal  and  vegetable  oils,  596 
in  burning  oils,  571 
in  Chinese  wood  oil,  613 
in  varnish,  618 
titration  of,  505,  508 
tungstic,  solution  of,  449 
weighing  dilute  acids,  506 
strong   acids,  Blay-Burkhard    burette, 
bulb   tube,   Deli  tube,' Lunge-Ray 
pipette,  snake  tube,  506-508 
Acker  process  for  determination  of  tin,  425 
Adolph's  apparatus  for  fluorine  determina- 
tion, 182 
modification   of   Offerman's   method   for 

fluorine,  182 
Ahlum's  method  for  free  acids  in  presence 

of  iron  salts,  530 
Air,  composition  of,  292 

examination  of.     See  Gas  Analysis,  728. 
oxygen  in,  hydrogen  combustion  method, 

703 

phosphorus  method,  702 
pyrogallate  method,  703 
pound  per  cubic  foot  of  coal  burned,  cal- 
culation of,  710 
Albuminoid  ammonia,  determination  of,  in 

water,  537 

Alexander's  volumetric   method   for   deter- 
mining lead,  239 

Alizarine  S  for  detection  and  determination 
of  aluminum,  14 


861 


862 


INDEX 


Alkali  arsenates,  arsenic  determination  in,  31 
standard  for  acidimetry  and  alkalimetry, 

501-504 

Alkalies,  chapter  on,  341 
detection  of  csesium,  lithium,  potassium, 

rubidium,  sodium,  341-342 
estimation  in  alunite,  356 
in  Portland  cement,  652 
in  silicates,  hydrofluoric  acid  method,  356 

J.  Lawrence  Smith  method,  355 
volumetric  methods,  357 
physical  properties,  341 
preparation  of  the  sample,  fertilizers,  343 
plants,  ashes  of,  344 
rocks  and  insoluble  mineral  products,  343 
saline  residues,  soluble  salts,  brines,  344 
soils,  343 

potassium  and  sodium.     See  subjects, 
reagent  f  normal  for  calcium  carbonate  in 

cement,  656 

separation  from  aluminum,  chromium,  iron, 
phosphoric  acid,  titanium,  uranium, 

345 

from  barium,  calcium,  strontium,  sul- 
phuric acid,  345 
from  above  elements  in  one  operation, 

Hick's  method,  346 
from  each  other,  347 
from  the  hydrogen  sulphide  group  and 

silica,  344 

from  magnesium,  by  means  of  ammoni- 
um phosphate,   barium  hydroxide 
or  mercuric  oxide  methods,  344 
test  for  iridium,  330 
for  palladium,  332 
Alkalimeter,  Mohr's,  106 

Schroetter's,  106 

Alkalimetric  method  for  determining  phos- 
phorus, 316 

for  determining  strontium,  389 
Alkaline  earths.    See  Barium. 

separation  from  one  another,  54 
Alkalinity  determination  in  water,  552 
Allen,  method  for  traces  of  iron,  223 
Allen,  modification  of  Devarda's  method  for 

nitrates,  300 
Allen  and  Bishop  method  for  sulphur  in 

pyrites  and  sulphur  ores,  396 
Allen  and  Palmer  modification  of  Gutzeit's 

method  for  arsenic,  40 

Alloys,  decomposition  of,  63,  85,  141,  150, 
153,.  234,  659,  661,  664,  666, 667,  669,  670 
detection  of  gold  in,  192 
general,  alloys  with: 
antimony,  20,  21 
iridium,  337 
iron-titanium,  259 
lead,  21,  234 
manganese,  258 
molybdenum,  259 
nickel,  285,  290 
rhodium,  337 


Alloys,  general,  silicon,  259 
tin,  21 

titanium,  434 
tungsten,  259,  448,  450,  451 
vanadium,  259 
special  alloys,  analysis  of: 

bearing    metal,    determination    of    bis- 
muth, 63 

brass  and  bronze,  determination  of: 
arsenic,  antimony,  copper,  lead,  iron, 

zinc,  667-668 
vanadium  in,  476 

Britannia    metal,   determining    arsenic^ 
antimony,   bismuth,   copper,   lead, 
iron,  manganese,  tin,  666-667 
German  silver,  determining  iron,  nickel, 

zinc,  etc.,  669 

manganese,  phosphorus   bronze — deter- 
mining   copper,    lead,    iron,    man- 
ganese, phosphorus,  zinc,  670 
Rose's  metal,  determining  copper,  bis- 
muth, lead,  663 

soft  solder,   determining  arsenic,   anti- 
mony, iron,  lead,  tin,  zinc,  661-663 
Wood's  metal,  determining  arsenic,  an- 
timony, bismuth,  cadmium,  copper, 
iron,  lead,  tin,  zinc,  664-665 
Alpha  benzildioxime  method  for  determining 

nickel,  286 
test  for  nickel,  273 
Alumina  in  nitrate  of  soda,  304 

in  phosphate,  together  with  iron,  320 
in  Prussian  blue,  633 
in  ultramarine  blue,  638 
in  sand,  374 
in  silicate  of  soda,  373 
in  titaniferous  ores,  446 
in  water,  547 
basic,  determination  of,  in  aluminum  salts, 

13 
and  iron  oxide  in  composite  white  paint, 

633 

in  green  paint  pigments,  640 
in  metallic  lead,  252 
in  Portland  cement,  650 
together  in  phosphate  rock,  320 
Alumina  ores,  arsenic  determination  in,  44 
Aluminum,  detection  of,  3,  14 
estimation,  general  procedures: 

gravimetric,  by  hydrolysis  with  ammo- 
nium hydroxide,  7 
by  hydrolysis   with  sodium   thiosul- 

phate,  9 
by  precipitation  as  aluminum  chloride, 

10 

as  phosphate,  9 
volumetric,  determination  of  combined 

alumina,  u 

free  alumina  or  free  acid,  1 2 
special  procedures: 

analysis  of  metallic  for  silicon  and 
iron,  1 6, 17 


SUBJECT  INDEX 


863 


Aluminum,  estimation,  in  iron  and  steel,  16 
in  presence  of  iron,  phenylhydrazine 

method,  446 

impurities  in  metallic  aluminum,  16 
industrial  application,  3 
occurrence,  minerals  and  ores,  3 
preparation  and  solution  of  the  sample, 

3~5 

extraction  of  ores  for  commercial  valu- 
ation, 4 

metallic  aluminum  and  its  alloys,  5 
properties,  3 

aluminum  phosphate,  10 
separation  from   glucinum,   iron,  manga- 
nese,   nickel,    phosphoric  acid,  silica, 
titanium,  uranium,  zinc,  5,  6 
from  chromium,  134,  135 
from  glucinum,  190 
solubilities,  metal  and  its  oxide,  3 
traces,  detection  and  estimation  of  with 

alizarine  S,  14 
Aluminum  Company  of  America,  method  for 

aluminum,  16 
Alunite,  alkalies  in,  356 
American  Vanadium  Company,  methods  of 

analysis,  474-476 
Amino-nitrosophenyl-hydroxylamine  method 

for  iron,  214 
Ammonia,  albuminoid,  in  water,  estimation 

of,  537 

free  in  water,  estimation  of,  536,  555 
gravimetric    method    for,  determining  as 

platino-chloride,  296 
volumetric  method,  297 
total,  in  ammoniacal  liquor,  297 
volatile,  in  ammoniacal  liquor,  297 
traces,  determination  of,  in  gas,  717 
Ammonium  chloride,  fusion  with  perchlorate 

(note),  128 
test  for  iridium,  330 
test  for  palladium,  333 
test  for  platinum,  324 
test  for  vanadium,  463 
hydroxide  method  for  determining  traces 

of  copper,  167 
test  for  iron,  210 
test  for  palladium,  332 
test  for  rhodium,  336 
iridium  chloride,  determination  of  iridium 

as,  331 
magnesium  phosphate,  acid  titration  of, 256 

properties  of,  256 
nitrate    washing    solution    for   aluminum 

hydroxide,  8 
oxalate    reagent    for    oxygen    consumed, 

water  analysis,  541 

phospho  molybdate  method  for  phosphor- 
us, 314 

phosphate  method  for  separating  magne- 
sium from  alkalies,  347 
platinochloride   method   for   determining 
ammonia,  296 


Ammonium  salts,  effect  on  magnesium  pre- 
cipitation, 255 

effect  on  sulphur  determinations,  395 
determination  of  ammonia  in,  295 
mixtures,  ammonia  in,  297 
sulphide  group,  separation  of,  142,  254, 344 
sulphide  method  for  mercury,  273 
test  for  ruthenium,  334 
test  for  vanadium,  463 
sulphocyanate  test  for  cobalt,  140 

test  for  iron,  210 
Andrew's  method  for  silver,  384 
Andre w-Burgarszk's  method  for  analysis  of 

crude  bromide  and  bromine,  82 
Anemometer,  692 
Animal  and  vegetable  oils,  analysis  of,  580 

test  for,  590 

Antifluorescence,  tests  for,  591 
Antimonous  and  antimonic  salts,  distinction 

between,  18 

Antimony,  detection  of,  by  hydrogen  sulphide 
test,  hydroxysis,  in  minerals,  traces,  18 
estimation,  general  procedures: 
gravimetric,     electrolytic     as    metallic 

antimony,  24 
as  trisulphide,  Sb2S3 
volumetric,  bromate  method,  26 
indirect  evolution  method,  28 
iodide  method,  26 
oxidation  with  iodine,  27 
permanganate  method,  28 
special  procedures: 
determination  in  alloys,  in  brass  and 

bronze,  668 

in  Britannia  metal,  667 
in  copper,  170 
in  hard  lead,  25 
in  metallic  lead,  250 
in  Rose's  metal,  664 
in  soft  solder,  23,  662 
in  tin  and  lead  alloys,  23 
in  type  metal,  66 1 
in  Wood's  metal,  664 
in  presence  of  vanadium,  472 
industrial  application  of  analysis,  18 
occurrence,  minerals,  ores,  and  alloys,  18 
preparation  and  solution  of  the  sample: 
alloys  of  antimony,  tin,  and  lead,  hard 
lead,  low-grade  oxides,  mattes,  slags, 
speisses,  sulphides,  rubber  materials, 
19-21 

properties,  antimony  trisulphide,  24 
separation  from  members  of  the  subsequent 
groups,  aluminum,  chromium,  cobalt, 
iron,  manganese,  nickel,  zinc,  alkaline 
earths  and  alkalies,  21 
from  bismuth,  cadmium,  copper,  lead 

and  mercury,  21 

from  arsenic,  antimony  and  tin,  22-23 
from  tin  in  alloys,  660,  667 
solubility  of  the  element  and  its  oxides,  19 
traces,  determination  of,  28 


864 


INDEX 


Antwerp  blue,  analysis  of,  638 

Apparatus  for  cement  testing,  649 

Arc,  electric,  temperature  of,  780 

Argon  in  the  atmosphere,  292 

Arsenates,  alkali,  31 

Arsenates,  distinction  from  arsenites,  30 

Arsenic,  detection  of,  by  Gutzeit  test,  by 

hydrogen  sulphide,  volatility  test,  30 
estimation,  general  procedures: 
gravimetric,    determination   as   arsenic 

trisulphide,  A^Ss,  36 
determination    as    magnesium    pyro- 

arsenate,  37 
volumetric,  oxidation  with  iodine,  Mohr's 

method,  39 

silver  arsenate  method,  40 
special  procedures: 
determination   in    alloys,   brass   and 

bronze,  668 

in  Britannia  metal,  667 
in  Rose's  metal,  664 
in  soft  solder,  662 
in  type  metal,  66 1 
in  Wood's  metal,  664 
determination  in  brimstone,  415 
in  copper,  170 
in  hydrochloric  acid,  510 
in  metallic  lead,  250 
in  presence  of  vanadium,  473 
impurities  in  "arsenic  acid,"  determina- 
tion of  moisture,  antimony,  arsenic, 
calcium,   cobalt,   copper,   iron,   lead, 
nickel  and  zinc  oxides,  silica,  sulphuric 
acid,  47-49 

industrial  application  of  methods,  30 
occurrence,  minerals,  ores,  30 
preparation  and  solution  of  the  sample, 
alkali  arsenates,  arsenic  acid,  arsenous 
oxide,    hydrochloric    and    sulphuric 
acids,  pyrites  ore,  31 
lead  arsenate,  zinc  arsenite  insecticides, 

32 

mispickel,  copper,  iron  and  steel,  33 
properties,  30 

separation  from  other  elements  by  dis- 
tillation, 33 

from  antimony  and  tin,  35 
from  tin  in  alloys,  637 
solubility  of  oxides,  sulphides  and  other 

salts,  30 
stains,  preservation  of  for  Gutzeit  method, 

4i 

traces,  determination  of  by  modified  Gut- 
zeit method  : 
in  acids,  hydrochloric,  nitric,  sulphuric, 

33-34 
in  baking  powders,  canned  goods,  meat, 

organic  matter,  etc.,  45 
in  ores,  alumina-bearing,  bauxite,  cin- 
ders, pyrites,  44 

in  salts,   sodium  chloride,  magnesium 
sulphate,  etc.,  45 


Arsenous  acid,  determination  of  with  iodine 

39 
reduction  of  bromates  with,  82 

chloride,  volatility  of,  30 

oxide  in  paint  pigments,  629 

in  zinc  oxide,  629 
Asbestine  paint  pigment,  631 
Ash,  in  black  paint  pigments,  641 

in  coal,  determination  of,  684 
fusibility,  684 

in  plants,  determining  alkalies  in,  244 

in  turpentine,  determination  of,  618 
Assaying,  chapter  on  furnace  methods  of,  739 

combination  methods,  769 

consequent  to  furnace  operations,  742 

corrected  assay,  742 

crucible  method  of  fusion,  744 

cupellation,  759 

cyanide  solutions,  gold  in,  773 

furnace  operations,  741 
preliminary  to,  742 

gold  determination,  742   • 

parting,  766 

preliminary  to  furnace  operations,  742 

quantity  of  sample,  influence  of,  742 

roasting,  incineration,  743 

sampling,  739 

scorification,  755 

silver  determination,  742 

silver  and  gold  retained  in  the  slag,  742 

type  schemes,  758 

weight,  unit  of,  definition,  739 
A.S.T.M.  standards  for  Chinese  wood  oil,  615 
for  linseed  oil,  boiled  and  raw,  616 
turpentine,  618 

Atomic  weights,  international,  table  of,  779 
Attack's  method  for  traces  of  aluminum,  14 
At  water  bomb  calorimeter  (Fig.  105),  679 

Bach's  test  for  rapeseed  oil,  595 

Baker  and  Clark,  chapter  on  tin,  419-430 

Baker's  method  for  tin,  426 

Baking  powder,  arsenic  determination  in,  45 

lead  determination  in,  243 

phosphate,    determination   of   phosphoric 

acid  in,  313 
Balance,    Christian    Becker,    chain     type, 

(Fig.  ssa),  323 
Ball  mill  (Fig.  103),  673 
Bank's  hydrogen  sulphide  generator  (Fig.  4), 

39 
Barium,  detection  of  with  sat.  sol.  of  calcium 

or  strontium  sulphates,  50 
with  soluble  chromates,  fluosilicic  acid, 

flame,  50 
spectrum  of,  50 
estimation,  general  procedures: 

gravimetric,  determination  as  chromate, 

BaCrO<,  57 

as  sulphate,  BaSO<,  58 
volumetric,  acid  titration  of  carbonate, 
60 


SUBJECT   INDEX 


865 


Barium,  estimation,  volumetric,  dichromate 

method,  59 

permanganate  method,  59 
potassium  iodide  method,  59 
estimation,  special  procedures: 

determination  in  insoluble  residue,  57 
in  ores,  57 
in  silicates,  57 

ore,  valuation  of.     See  Barytes. 
industrial  application,  50 
occurrence,  ores,  commercial  products,  50 
preparation  and  solution  of  the  sample, 
carbonates,     insoluble    residue,     sul- 
phates,  sulphides,   soluble   salts,   or- 
ganic matter,  50-51 
properties,  barium  sulphate,  50,  58 

barium  chromate,  58 
separations,  general  considerations,  51 
from  alkalies  and  magnesium  by  the 
oxalate  and  sulphate  methods,  53,  54 
from  calcium  and  strontium,  54,  55 
from  previous  groups,  53 
solubilities,  barium  compounds,  50,  58 
traces,  detection  of  by  flame  and  spectrum, 

50 
Barium  acetate  or  chloride  test  for  chromate, 

132 
chloride  in  hydrochloric  acid,  510 

-potassium  chromate  method  for  sulphur 

determination,  403 
test  for  bromate,  78 
test  for  selenium,  359 
chromate,  determination  of  chromium  as, 

136 

property  of,  58 
solubility  of,  58 

-thiosulphate  method  for  sulphur,  404 
hydroxide  method  for  separating  magne- 
sium from  alkalies,  346 
sulphate,  apparatus  for  filtering  of,  398 
decomposition  for   sulphur  determina- 
tion, 394 
in  blanc  fixe,  632 
in  lithopone,  630 

precipitation  of  sulphur  as,  395,  396 
properties  and  solubility  of,  58 
Base  box,  definition  (note),  428 
Barnitt,  formulae  for  solutions,  525 
Barton,  methods  for  titanium  in  steel,  441 
Barton  and  Scott,  chapter  on  titanium,  432 
Barytes,    analysis   of,   determining    barium 
carbonate,   barium   sulphate,   iron   and 
aluminum  oxides,  lime,  magnesia,  silica, 
soluble  SOs,  etc.,  60 
water  test  for  magnesium,  253 
Basic  acetate  method  for  precipitating  alu- 
minum and  iron,  260 

Basic  alumina  in  aluminum  salts,  determina- 
tion of,  13 
"Basic  hydrochloric  acid"  in  bichloride  of 

*     tin,  424 
Basic  nitrate,  precipitation  of  bismuth  as,  66 


Baubigny's    method,    modified,    for    deter- 
mining halogens,  130 

Baudisch's  cupferron  method  for  iron,  214 
Baudoin's  test  for  sesame  oil,  66 
Bauxite,  analysis  of,  determining  soluble  and 
total  alumina,   soluble  and  total  iron, 
insoluble  residue,  silica,  titanium  oxide, 
14-15 

arsenic  determination  in,  44 
Bead  test  for  titanium,  432 
Bearing  metal,  determining  bismuth  in,  63 
Bechi's  test  for  cottonseed  oil,  592 
Becker  chain  balance  (Fig.  553),  323 
Bekk's   method    for   determination    of    the 

halogens,  130 
Belt  dressings,  601 

Bennett's  method  for  determining  arsenic,  40 
Benzidine  acetate  test  for  gold,  193 

hydrochloric  acid  method  for  determining 

sulphates,  405 

sulphate  method  for  sulphates  in  water,  551 
Benze's  method  for  determining  cerium  in 

Welsbach  mantles,  116 
Benzoic  acid  standard  for  acidimetry,  504 
Berg,  P.  von,  iodine  titration  of  cadmium 

sulphide,  87 

Beryllium.     See  Glucinum,  189 
Berzelius  process  for  determining  tungsten, 

454 

Betts,  nitrometer  method,  307 
Bichloride  of  tin,  Acker  process  for  analysis 

of,  425 

hot  water  precipitation  of  tin  in,  424 
sulphide  method  for  tin  in,  426 
Bidtel's  method  for  valuation  of  fluorspar, 1 86 
Bishop,  fuming  sulphuric  acid  table,  795 
Bishop  and  Allen,  method  for  determining 

sulphur  in  ores,  396 

Bismuthate  method  for  determining  man- 
ganese, 263 
in  steel,  226 
in  water,  550 
Bismuth,   detection   of,   general  procedure, 

reducing  agents,  blowpipe  test,  62 
estimation,  general  procedures: 
gravimetric,     determination     as     basic 

chloride,  65 

as  metal  by  cyanide  reduction,  68 
as  metal  by  electrolysis,  68 
as  oxide,  Bi2O3,  66 
as  sulphide,  Bi2S3,  67 
volumetric,  bismuth  iodide  colorimetric 

method,  70 

cinchonine   potassium   iodide   colori- 
metric method,  69 

permanganate  titration  of  oxalate,  68 
estimation,  special  procedures: 
in  alloys  and  metals,  Britannia  metal,667 
in  metallic  copper,  168 
in  metallic  lead,  248 
in  Rose's  metal,  663 
in  Wood's  metal,  664 


866 


INDEX 


Bismuth,  industrial  application  of  methods, 

62 

occurrence,  62 

preparation  and  solution  of  the  sample, 
alloys,  lead  bullion,  refined  lead, 
ores,  62,  63 

properties,  bismuth,  basic  nitrate,  66 
oxy-chloride,  65 
sulphide,  67 

separations,   aluminum,   chromium,   iron, 
cobalt,  manganese,  nickel,  zinc,  mag- 
nesium, alkaline  earths,  alkalies,  64 
from  arsenic,  antimony,  tin,  molybde- 
num, selenium,  tellurium,  64 
from  cadmium  and  copper,  65 
from  lead  and  mercury,  64 
solubility,  metal  and  salts,  62,  65,  66,  67 
traces,  determination  of,  69,  70 
Black  oils,  60 1 
Blair,  bismuthate  method  for  determination 

of  manganese,  263 

colorimetric  method  for  carbon  determina- 
tion in  steel,  108 

Blanc  fixe  and  barytes,  analysis  of,  711 
Blangey's  method  for  chloric  acid,  128 
Blast-furnace  gas,  analysis  of,  711 
Blattner  and  Brassuer,  chlorine  in  chlorates 

and  perchlorates,  1 29 
method  for  reduction  of  chlorates,  128 
Blay    and    Burkhard,    graduated    weighing 

burette  (Fig.  83),  508 
Bleaching  powder,  evaluation  of,  130 
Blister  copper,  electrolytic  determination  of 

copper  in,  158 

Blood,  carbon  monoxide  determination  by 
means  of,  729 

in,  93 

"Bloom"  in  oils,  591 
Blowpipe  test  for  bismuth,  62 

test  for  cadmium,  84 
Blue  lead,  sublimed,  analysis  of,  638 
Blue  vitriol,  copper  determination  in,  174 
Boiling,  prolonged,  effect  on  aluminum  hy- 
droxide precipitate,  8 
effect  on  glucinum  separation  from  alu- 
minum, 191 

point  chart,  sulphuric  acid  of  varying  con- 
centration, 502 
Borax  bead,  boron  test,  71 

evaluation  of,  76 
Boric  acid,  evaluation  of,  77 

method  for  determining  ammonia  (ref- 
erences), 554 

Boron,  detection  of,  borax  bead  test,  proper- 
ties, flame  test,  turmeric  test,  7; 
estimation,  general  procedures: 

gravimetric,  lime  fixation  method,  74 

method  of  Gooch  and  Jones  (note),  75 
volumetric  determination,  76 
estimation,  special  procedures: 
determination  as  boric  acid  in  butter,  73 
in  canned  goods,  74 


Boron,  estimation,  determination,  in  meat, 

73. 

in  milk,  73 

in  silicates,  enamels,  etc.,  72 

in  mineral  water,  72 
industrial  application  of  methods,  71 
occurrence,  ores,  alloys,  sundry  products, 

7i 

preparation  and  solution  of  the  sample, 
boric  acid,  boric  oxide,  boracite,  boro- 
calcite,   boronatrocalcite,   borax,   cal- 
cium borate,  enamels,  silicates,  etc.,  72 
carbonates,   butter,   meat   and   canned 

goods,  73 
mineral  water,  72 

solubility  of  boron,  boric  acid,  borax,  72 
traces,  detection  of,  by  Robin's  test,  77 
Bosworth  and  Gooch,  method  for  silver  de- 
termination, 384 
Bowman  and  Scott,  ferrous  sulphate  method 

for  nitric  acid,  515 
Bradbury  and  Owen,  alkali  carbonates  and 

hydrates  present  together,  531 
Brass  and  bronze,  analysis  of  determining 
arsenic,  copper,  iron,  lead,  antimony, 
tin  and  zinc,  667-669 
determination  of  vanadium  in,  478 
method  of  National  Brass  and  Copper 

Tube  Co.,  lead  and  copper  in,  1 75 
Breyer,  chapter  on  methods  of  analysis  of 

zinc,  447 
manganese  determination  in  spiegel  iron, 

268 

separation  of  zinc  as  sulphide,  485 
Briggs  and  Scott,  modified  Orsat  apparatus 

(Fig.  131),  723 

Brimstone,  analysis  of,  determining  moisture, 
ash,  arsenic,  chlorine,  and  available  sul- 
phur in,  415 

Brines,  preparation  of  for  alkali  determina- 
tion, 344 

Briquettes,    cement,    details   for   and   illus- 
tration of  (Fig.  98),  649 
Britannia   metal,    analysis   of,    determining 
arsenic,    bismuth,    copper,    iron,    lead, 
antimony,  and  tin,  666,  667 
British  thermal  unit  (B.t.u.)  calculation  of, 

681 

determination  of  heat  value  of  coal,  678 

determination  of  in  illuminating  gas,  713 

Bromate  method  for  determining  antimony, 

25 
Bromates,  detection  of,  78 

determination  of  by  arsenous  reduction,  82 
Bromine,   detection   of,    tests   with   carbon 
disulphide,  carbon  tetrachloride,  barium 
chloride,  magenta  test,  silver  nitrate,  78 
estimation  general  procedures: 
gravimetric,  determination  as  silver  bro- 
mide, 80 

volumetric,  free  bromine  by  potassium 
iodide  method,  81 


SUBJECT   INDEX 


867 


Bromine,    estimation,    volumetric,    chlorine 
method  for  soluble  bromides,  81 
silver  thiocyanale  method  of  Volhard, 

81 
estimation,  special  procedures: 

crude  potassium  bromide,  analysis  of, 

82 
impurities  in  commercial  bromine,  chlorine 

in,  83 

industrial  application,  79 
occurrence,  79 
preparation  and  solution  of  the  sample, 

organic  matter,  salts,  etc.,  79 
properties,  79 

separations  from  chlorine  and  iodine,  80 
heavy  metals,  cyanides,  and  silver,  79 
solubility  of  the  element  and  its  salts,  79 
traces,  determination  of,  81 
Bromine-ammonia    method    for    separating 

manganese  from  zinc,  480 
precipitating  manganese  dioxide  with,  261 
Bromine  number  in  oil  analysis,  586 
Browne's  heating  tests  for  Chinese  wood  oil, 

614 
Browning-Drushel,  separation  of  magnesium 

from  the  alkalies,  347 
Browning-Flint,    method    for    determining 

tellurium,  365 
Browning's  Introduction  to  Rarer  Elements 

(reference),  114 
Browning's  test  for  fluorine,  177 

test  for  silica,  367 
Buckwheat  coal,  determination  of  B.t.u.  in, 

example  data,  682 
Bunsen  pump  (Fig.  in),  688 
Bureau  of  Standards  method  for  carbon  in 

steel,  224 

manganese  in  steel,  228 
phosphorus  in  steel,  229 
silicon  in  steel,  232 
sulphur  in  steel,  230 

Burettes,  standard,  for  acidimetry  and  alka- 
limetry, 505 
Burges'    nitroso-beta-naphthol    method    for 

cobalt,  143 

Burkhard  and  Blay,  weighing  burette,  508 
Burning  oils.     See  Oils,  567 
Butter,  boric  acid  determination  in,  73 
method  of  analysis.     See  Oils,  599 

Cadmium,  detection  of,  general  procedure, 

84 

spectrum  of  cadmium,  blowpipe  test,  84 
estimation,  general  procedure: 

gravimetric,  determination  as  cadmium 

sulphate,  86 

as  cadmium  sulphide,  491 
as  metallic  cadmium  by  electrolysis, 

86,  491 
volumetric,  iodine  titration  of  cadmium 

sulphide,  87 
estimation,  special  procedures: 


Cadmium,     estimation,     determination    in 

alloys  and  metals: 
in  metallic  lead,  250 
in  spelter,  491 
in  Wood's  metal,  664 
industrial  application,  84 
occurrence,  84 

preparation  and  solution  of  the  sample, 
alloys,  carbonates,  ores,  sulphides,  in 
presence  of  lead,  84,  85 
separation  from  members  of  the  ammonium 
sulphide  group,  alkaline  earths  and 
the  alkalies,  85 

from  arsenic,  antimony  and  tin  in  pres- 
ence and  in  absence  of  copper,  85 
from  copper  in  alloys,  665 
from  bismuth  and  lead,  85 
from  mercury,  86 
from  silica, -85 
Cadmium  chloride  and  sulphate  reagents  for 

sulphur  determination,  399 
metal  in  alloys,  Appendix 
sulphate,  determination  of,  86 
sulphide,  gravimetric  determination  of  cad- 
mium as,  491 
volumetric  determination  of  cadmium 

as,  87 
Caesium,  detection  of,  342 

separation  from  lithium  and  sodium,  347 
Cahen-Little-Morgan,  arsenic  determination 

in  organic  matter,  32 
Caillet,  elaidin  test  for  oils,  582 
Cain  and  Witmer,  method  for  vanadium  in 

steel,  471 
Calcium,  detection  of,  general  procedure,  88 

flame  test,  spectrum,  88 
estimation,  general  procedures: 
gravimetric,  oxalate  method,  91 

other  methods,  92 
volumetric,   permanganate   titration  of 

the  oxalate,  92 
estimation,  special  procedures: 

determination    of    in    composite    white 

paints,  634 

in  green  paint  pigments,  640 
in  orange  and  yellow  paint  pigments. 

639 

in  Portland  cement  as  CaO  (lime),  651 
in  sand,  374 
in  water,  548 

in  water  as  calcium  sulphate,  561 
industrial  application  of  methods,  88 
occurrence,  ores,  minerals,  etc.,  88 
preparation  and  solution  of  the  sample 
cements,  dolomites,  limestone,  mag- 
nesite,    gypsum,    plaster    of     Paris, 
silicates,  sulphates,  sulphides,  pyrites, 
salts,  89 

separation  from  aluminum,  iron,  copper, 
cobalt,  nickel,  manganese,  zinc  and 
members  of  the  hydrogen  sulphide 
group,  89 


INDEX 


Calcium,  separation  from  alkalies,  barium, 

strontium,  magnesium,  PaOa,  90 
from  silica,  89 
solubilities,  88 
traces,  detection  of,  88 
Calcium    carbonate,    apparatus    for    deter- 
mining in  cement  mixture,  657 
rapid  method  for  determining  in  cement, 

656 
fluoride,  decomposition  of,  1 79 

method  for  fluorine,  180 
Calorific  power  of  illuminating  gas,  713 

of  fuel,  678 
Calorimeter,  Atwater  bomb  (Fig.  105),  for 

coal,  B.t.u.  det.,  679 
Junker's  for  gas  (Figs.  124,  125,  126),  713, 

7i4 

standardization  of  the  Atwater,  683 
Camoin's  test  for  sesame  oil,  595 
Candle  power  of  illuminating  gas,  712 
Canned  goods,  arsenic  determination  in,  45 

tin  determination  in,  430 
Caoutchouc  in  lubricating  oil,  578 
Capometer,  691 

Carbide  of  silicon,  decomposition  of,  371 
Carbon,  detection  of  carbon  dioxide  in  gas,  93 
carbonates,  93 
carbonic  acid  in  water,  93 
carbon  monoxide  in  blood,  93 
estimation,  general  procedures: 
gravimetric,    dry   combustion   method, 

weighing  CO2,  95 
wet  oxidation  process,  weighing  CC>2, 

102 
volumetric,  barium  hydroxide  method, 

titration  of  carbonate  formed,  107 
measurement  of  volume  of  COz  formed 

(ref.),  107 

estimation,  special  procedures: 
in  black  pigments,  640 
in  coal  as  "fixed  carbon,"  678 
in  iron  and  steel,  99,  100,  224,  225 

colorimetric  method,  108 
graphitic  carbon,  99 
organic  substances,  101,  102 
occurrence,  94 
preparation  of  sample,   alloys,   iron  and 

steel,  94 
separation   from   iron    and    steel,    cupric 

potassium  chloride  method,  94 
residue    test   of   lubricating   oils,    Gray's 

method,  579 
Carbonates  in  ores,  51,  85,  93,  94,  187,  211, 

304 

determination  of  in  presence  of  other  com- 
bined acids,  412 

Carbon  bisulphide.    See  Carbon  Bisulphide. 
Carbon  dioxide  combined  as  carbonate: 

estimation,  general  procedures  for  de- 
termination, 103 

gravimetric  determination  in  carbon- 
ates, 103 


Carbon    dioxide,    estimation,    gravimetric 

loss  of  weight  method,  106 
volumetric,  measuring  the  gas  evolved, 

105 

estimation,  special  procedures: 
in  ammoniacal  gas  liquors,  298 
in  baking  powder,  available  COz,  106 

residual  CC>2,  105 
in  cement,  74 

in  composite  white  paint,  634 
in  corroded  white  lead,  625 
in  blanc  fixe,  633 
in  gypsum,  632 
in  zinc  oxide,  627 
free  in  gaseous  mixtures,  292,  698,  700, 

704,  718 
Carbon  disulphide,  bromine  detection  with, 

.  78 

iodine  determination  with,  206 
purification  of  (see  apparatus  for,  Fig. 

7),  67 
monoxide  in  blood,  detection  of,  93 

in  gaseous  mixtures,  determination  of, 

669 

in  illuminating  gas,  determination  of,  704 
tetrachloride,  bromine  test  with,  78 
tubes,   for  colorimetric   determination  of 

carbon  in  steel  (Fig.  25),  109 
Carbonic  acid  free  in  water,  553 

indicators,  708 
Carborundum,  silicon  carbide,  decomposition 

of  for  silica  det.,  371 
Carius  method  for  halogens  in  organic  matter, 

121 
Carnot's  method,  modified,  for  determining 

gold,  197 

Cement,  analysis  and  testing  of,  642 
apparatus  for  testing,  Fairbank's  testing 

machine  (Fig.  100),  648 
gang  mold  (Fig.  99),  647 
Gilmore  needles  (Fig.  95),  645 
Le  Chatelier's  specific  gravity  apparatus 

(Fig.  93),  643 

Riehl6  automatic   cement   testing  ma- 
chine (Fig.  101),  649* 
Vicat  needle  (Fig.  94),  644 
calcium  in,  89 
carbon  dioxide  in,  94 
mixture,  calcium,  carbonate,  rapid  method 

for  determining,  656 

normal  consistency,  determination  of,  644 
physical  testing,  642 
Portland  cement,  analysis  of,  650 
determination  of  alkalies,  alumina,  iron, 
insoluble  residue,  lime,  loss  on  ig- 
nition,   magnesia,    silica,    sulphur, 

550-553 

rapid  method  of  analysis,  553 
setting  time,  645 

soundness  or  consistency  of  volume,  646 
specific  gravity,  643 
tensile  strength,  647 


SUBJECT   INDEX 


869 


Cement,  rock,  analysis  of    (limestone,  lime, 

Rosendale  cement,  etc.),  658 
Cerium,  detection  of,  spectroscopic  test,  112 
estimation,  gravimetric  methods,  115 

volumetric  method,  116 
estimation  in  Welsbach  mantles,  116 
industrial  application,  113 
occurrence  and  properties,  112,  113 
preparation  of  the  sample,  acid  extraction, 

114 

fusion  method,  114 
separation  of  the  rare  earths  from  iron, 

aluminum,  thorium,  114 
from  calcium  and  magnesium,  115 
of  the  rare  earths  from  one  another,  115, 

117 

Chamber  burette  (Fig.  79),  505 
Chancel's  method  for  determining  aluminum, 

9 
Character  of_copper  deposits  by  electrolysis, 

161 
Characteristics  of  some  animal  and  vegetable 

oils,  604,  605 

of  some  fatty  acids  from  oils,  603 
of  waxes,  606 

Chemical  tests  of  water,  536 
Chili  saltpeter.     See  Nitrate  of  Soda  under 

Nitrogen,  303 
Chimney  flue  gases,  7.08 
China  clay  paint  pigment,  631 
Chinese  blue,  analysis  of,  638 
Chinese  wood  oil,  analysis  of,  determining 
acid  number,  iodine  number,  saponifica- 
tion  number,  specific  gravity,  unsapon- 
ifiable  matter,  refractive  index,  heating 
and  Jelly  tests,  613-615 
Chlorate,  test  for,  119 
determination  of,  128 

in  presence  of  perchlorates,  129 
removal  of,  in  sulphur  determination,  395 
Chloric  acid.     See  Chlorate. 
Chloride,  detection  of,  118 
Chlorides,  determination  of.     See  Chlorine. 

method,  for  determining  silver,  376 
Chlorine,  detection  of  free,  118 

combined   chlorine,   chloride   by   silver 

nitrate  test,  118 
test  in  presence  of  bromide  and  iodide, 

118 
test  in  presence  of  cyanate  and  cyanide, 

thiocyanate,  118 

test  for  free  hydrochloric  acid,  118 
test  for  chlorate,  chlorite,  hypochlorite, 

perchlorate,  119 
estimation  of  combined  chlorine  as  chloride, 

general  methods: 
gravimetric  method  as  silver  chloride, 

124 
volumetric    methods,    silver    chromate 

method,  in  neutral  solution,  126 
silver    thiocyanate    method    in    acid 
solution,  125 


Chlorine,  estimation  of  combined  and  free 

chlorine,  special  cases: 
determination  combined  chlorine  in  pres- 
ence of  bromine  and  iodine  (com- 
bined), 130 

in  presence  of  other  acids,  412 
in  brimstone,  415 

in  cement  copper  and  copper  ores,  1 74 
in  water,  541,  554 
in  zinc  oxide,  627 
determination  of  free  chlorine,  127 
in  hydrochloric  acid,  509 
in  nitric  acid,  515 

industrial  application  of  methods,  119 
occurrence,  119 

preparation  and  solution  of  the  sample, 

ores,  cinders,  rocks,  water  soluble  and 

insoluble  chlorides,  silver  chloride,  1 20 

organic  matter,  decomposition  by  Carius 

method,  121 

decomposition  by  lime  method,  122 
decomposition  by  sodium  peroxide 

method,  122 
separation  from  iodine,  123 

together  with  bromine  from  iodine,  1 24 
halides  from  the  heavy  metals,  123 
halides  from  one  another,  123 
halides    from    silver    and    from    silver 

cyanide,  123 

solubility  of  chlorine  and  its  salts,  119 
traces,  detection  of,  118 

determination.     See  Estimation,  Special 

Cases. 

free,  liberation  of  bromine  with,  81 
method  for  decomposing  alloys,  666 
water,  decomposition  of  hydrobromic  acid 

in  nitric  acid,  296 
Chloroplatinate    method    for    determining 

potassium,  349 
Hicks'  modification,  350 
Chlorosulphonic  acid,  analysis  of,  526 
Chromate,  detection  of  barium  with,  50 
method  for  determining  barium  as  BaCrO4, 

volumetric  method  for  determining  barium, 

59 

method  for  determining  chlorine,  126 
method  for  determining  lead,  236 
Chromic  acid,  determination  of,  in  presence 

of  vanadic  acid,  472 
removal  of  from  nitric  acid,  296 
hydroxide,  precipitation  of,  135 
Chromium,  detection  of,  tests  with  barium 
acetate,  ether,  lead  acetate,  mercurous 
nitrate,    hydrogen    peroxide,    reducing 
agents,  diphenyl  carbazide,  132 
distinction  between  chromic  and  chromous 

salts,  132 

estimation,  general  procedures: 
gravimetric,    determination   as   barium 

chromate,  136 
as  the  oxide,  Cr2O3,  135 


870 


INDEX 


Chromium,  estimation,  volumetric,   ferrous 
sulphate      and       permanganate 
method,  137 
iodide  method,  137 
estimation,  special  procedures: 
determination  in  green  paint  pigments, 

640 
in  orange  and  yellow  paint  pigments, 

639 

in  presence  of  vanadium,  473 
industrial  application  of  methods  for,  132 
occurrence,  132 

preparation  and  solution  of  the  sample, 
refractory  materials,  materials  high  in 
silica,  chrome  iron  ores,  133 
iron  and  steel,  134 
separations,  from  alumina  and  iron,  134, 

J3S 

solubility  of  the  metal,  133 
traces,  detection,  132 

estimation,  138 
Chromium  salts,  comparison  with  vanadium 

salts,  463 
Cinchonine    potassium    iodide    method    Tor 

determining  bismuth,  69 
Cinders,  chlorine  in,  1 20 
Citric  acid,  analysis  of,  530 

reagent  for  calcium  determination,  90 
Clark  and  Baker,  chapter  on  tin,  419-430 
Clark's  modification  of  Mohr's  method  for 
-  antimony,  27 
method  for  separation  of  antimony  from 

tin,  22 

Classen,  deposition  of  gold,  195 
and  Henz  method  for  determining  tin,  430 
and  Reiss  method  for  determining  anti- 
mony, 24 
Cleveland  cup  for  fire  test  of  lubricating  oils, 

577 
Coal,  methods  of  analysis,  672 

ash,  determination  of,  674 

Atwater  bomb  calorimeter  (Fig.  105),  689 

buckwheat  coal,  typical  analysis  of,  682 

calculation  of  B.t.u.,  681 

calorific  value,  determination  of,  678 

calorimeter,  standardization  of,  683 

composition  of,  709 

fixed  carbon,  determination  of,  678 

fusibility  of  coal  ash,  684 

Hoskins'  electric  furnace  (Fig.  107),  684 

moisture  determination  in  coal,  674 

preparation  of  the  sample,  672 

references,  685 

sampling  coal,  672 

quartering  (Fig.  103),  673 

turbidimetric  sulphur  table,  676,  677 

volatile  combustible  matter,  determination 
of,  674 

volatile  sulphur,  determination  of,  675 
Cobalt,  detection  of,  general  procedure,  140 
ammonium  sulphocyanate  test  for,  140 
dicyandiamidine  sulphate  test  for,  140 


Cobalt,  potassium  nitrite,  potassium  sulpho- 
cyanate tests,  140 
estimation,  general  procedures: 
gravimetric,  deposition  of  the  metal  by 

electrolysis,  144 

nitroso-beta-naphthol  method,  143 
potassium  nitrite  method,  143 
estimation,  special  procedures: 
determination  in  cobalt  oxide,  145 
in  copper  (metallic),  146 
in  enamels,  147 
in  ferro-cobalt,  146 
in  lead  (metallic),  146 
in  metallic  cobalt,  146 
in  metallic  nickel,  146 
in  ores,  147 
in  steel,  148 

preparation  and  solution  of  the  sample, 
metallic  cobalt,  nickel,  and    cobalt  al- 
loys, cobalt  oxides,  ores  containing 
cobalt,  141 
separation   of   ammonium   sulphide   from 

the  hydrogen  sulphide  group,  142 
ammonium  sulphide  group  from  alka- 
line earths  and  alkalies,  142 
cobalt  and  nickel  from  manganese,  142 
cobalt  from  nickel  and  from  zinc,  142 
Cold  test  for  lubricating  oils,  576 
Color  in  butter,  detection  of,  600 
Color  comparitor  or  camera  for  det.  carbon 

in  steel  (Fig.  26),  109 
Color,  organic,  in  red  and  brown  pigments, 

635 

Color  test  in  turpentine,  617 
Color  test  of  water,  534 
Colorimeter  (Figs.  43,  69,  70),  245,  440,  442 
Colorimetric  determination  of  aluminum,  14 
of  ammonia,  299,  537 
of  bismuth,  70 
of  carbon,  108 
of  chromium,  138 
of  copper,  165,  166,  167 
of  fluorine,  183 
of  gold,  197 
of  iron,  222,  223 
of  lead,  243 
of  manganese,  267 
of  titanium,  439,  441,  444 
Columbium,  detection  of,  455 
estimation,  procedure,  457 
occurrence,  455 
separation    from    antimony,    silica,    tin, 

tungsten,  457 
isolation  of  columbium  and   tantalum 

oxides,  456 

Combination    methods,    silver    determina- 
tion, 383 
Combined  sulphuric  acid  in  aluminum  salts, 

12 

in  cement,  .65  2 

in  sulphates.     See  chapter  on  Sulphur, 
in  soluble  sulphates,  403 


SUBJECT   INDEX 


871 


Combustion  furnace  for  carbon  determina- 
tion, 96 

hinged  type  (Fig.  320),  174 
for  assaying,  748 
method    for  ^carbon    determination,    96, 

225 

Constant  temperature  bath,  160 
Constants  of  various  oils,  616 
Container  for  gas  sample  (Fig.  112),  689 
Conversion  factors,  Baume  to  specific  grav- 
ity, 819 
formulas,  804 
Engler,  Redwood,  and  Saybolt  times — 

comparison,  607 
temperature,  Centigrade  to  Fahrenheit, 

818 
weights  and  measures  customary  and 

metric  systems,  820 

Cooper  Hewitt  mercury  light  (Fig.  44),  247 
Copper,    detection    of,   general    procedure, 
hydrogen  sulphide  test,  flame  test,  re- 
duction tests,  149 
estimation,  general  procedures: 

gravimetric,  copper  oxide  method,  162 
cuprous  sulphocyanate  method,  153 
electrolytic  methods,  preliminary  re- 
marks, 155 
rapid  methods,  157 
slow  methods,  158 
electrolysis,  effect  of  impurities  on, 

161 

precautions  and  notes  on    pro- 
cedure, 1 6 1 

removal  of  deposit,  162 
hydrogen  reduction  method,  1 73 
volumetric  methods,  potassium  cyanide 

procedure,  164 

potassium  iodide  method,  163 
estimation,  special  procedures: 

determination  of  copper  in  alloys  and 

metals,  brass  and  bronze,  668 
in  Britannia  metal,  667 
in  lead,  metallic,  250 
in     manganese     phosphorus    bronze, 

670 

in  refined  copper,  173 
in  Rose's  metal,  663 
in  type  metal,  660 
in  Wood's  metal,  665 
determination  in  water,  557 
impurities  in  blister  and  refined  copper: 
arsenic,  33 

bismuth  and  iron,  168 
antimony,   arsenic,    selenium,   and   tel- 
lurium, 170 

cobalt,  lead,  nickel  and  zinc,  169 
oxygen  and  sulphur,  172 
phosphorus,  173 
chlorine  in  cement  copper  and  Copper 

ores,  174 

industrial  application  of  methods,  149 
occurrence,  149 


Copper,  preparation  and  solution  of  the 
sample,  alloys,  cast  iron,  steel,  matte, 
slag,  iron  ores,  and  iron  ore  briquettes 
and  metals,  sulphide  ores,  copper 
glance,  copper  pyrites,  and  iron  py- 
rites, 150-153 
separations,  deposition  by  a  more  positive 

metal,  154 

precipitation  as  copper  sulphocyanate,  153 
removal    of    members    of     subsequent 

groups,  153  ^ 
removal  of  arsenic,  antimony,  bismuth, 

lead,  silver,  tin,  154 
removal  of  cadmium,  155,  665 
solubility  of  the  metal,  150 
traces  of,  ammonia  method,  167 
hydrogen  sulphide  method,  167 
ferrocyanide  method,  166 
potassium  ethyl  xanthate  method,  165 
Copper  pyrites,  150 

sulphate  for  determining  hydrocyanic  acid, 

no 
standard  solutions  (see  also  "  reagents "), 

163,  165,  166 

Corrosion,  acid  waters,  calculation  of,  563 
Cottonseed  oil,  test  for  (see  Oils),  592 
Craig's  method,  modified,  for  basic  alumina 

or  free  acid  in  aluminum  salts,  1 2 
Crawford-Lenher    colorimetric    method    for 

titanium,  444 
Crook's  select  methods  of  analysis  (reference), 

116 

Cupferron  method  for  iron,  214 
Cupric-potassium-chloride  reagent,  prepara- 
tion of,  95 

Cupro-vanadium,  476 
Cuprous    chlorine,    ammoniacal    and    acid, 

preparation  for  gas  analysis,  734 
-sulphocyanate    method    for    determining 

copper,  153,  162 

Cyanide,  determination  of,  no,  in 
Cyanide  process  for  tin  ores,  420 
Cyanide,  silver  determination  as,  377 
volumetric  determination  of  silver,  383 

Dely  weighing  tube  (Fig.  81),  506 
Deniges  and  Chelle  bromine  test,  78 
Deniges'    cyanide   method   for   determining 

silver,  383 

Derby,  chapter  on  assaying,  739 
chapter  on  gold,  192 
chapter  on  silver,  375 
and  Scott,  chapter  on  copper,  149 
Deshey's  method  for  manganese  in  steel,  227 
Detection.     See    under    name    of    element 

sought. 
Devarda  apparatus  for  determining  nitrates 

(Fig.  51),  301 
Devarda's  method,  modified,  determination 

of  nitrates  by,  300 

Dichromate  of  potassium  method  for  iron,  216 
titration  in  determining  chromium,  138 


872 


INDEX 


Dicyandiamidine  sulphate  test  for  cobalt,  140 
Dietz   and   Margosches   method   for   deter- 
mining iodine,  205 
Dimethyl  glyoxime  method  for  nickel,  287 

test  for  nickel,  283 
Dioxide    of    manganese,    separation    of    by 

means  of  bromine,  261 
Diphenyl-endo-anilo-hydro-triazole    (nitron) 

method  for  nitrates,  296,  299 
Diphenylamine  test  for  nitrates,  292 
Diphenyl     carbazide     test    for     chromium 

(chromate),  132 

Distillation  of  arsenious  chloride,  35 
method  for  separating  selenium  and  tel- 
lurium, 361 
test  for  oils,  569 

Dittrich,  small  amounts  of  chromium,  138 
Dividing  pipette  (Figs.  30  and  42),  160,  233 
Doerflinger  and  Scott,  chapter  on  chlorine, 

118 

Dolomites,  89,  94 
Dole,  field  assay  of  water,  565 
Dowsett's  factory  test  for  gold,  198 
Drying  oils,  list  of,  602 
Drying  test  of  oils,  597 
Du  Font's  nitrometer,  306,  307 
Dupre's  method  for  iodine,  modified,  207 
Dust,  determination  of  in  gas,  712 

Edgar's  method  of  reduction  of  vanadium 

with  sulphur  dioxide,  282 
volumetric  determination  of  vanadium,  ar- 
senic or  antimony,  in  presence  of 
one  another,  472 
of   vanadium   and   molybdenum,    in 

presence  of  one  another,  471 
of  vanadium  and  chromium  acids,  in 

presence  of  one  another,  473 
Edible  fats  (see  Oils),  599 
Elaidin  test  for  oils,  582 
Electric   Heating   Apparatus   Co.,   furnace, 

hinged  design,  174 

Electrolyte,  tesi  for  copper  in,  after  elec- 
trolysis, 161 

Electrolytic  determination  of  antimony,  24 
bismuth,  68 
cadmium,  86 
cobalt,  144 
copper,  155 
gold,  194 
lead,  238 
mercury,  272 
nickel,  289 
platinum,  329 
silver,  377 
tin,  430 
zinc,  479 
Elliott  apparatus  for  gas  analysis  (Fig.  121), 

700 

Enamel,  cobalt  determination  in,  147 
Engler's  method,  distillation  test  of  oil,  569 
viscosimeter,  572 


Engler  and  Haase  on  flash  test  of  oil,  567 

Erbium,  112,  113 

Errors,  causes  of  in  silica  determination,  368 

in  determining  the  alkaline  earths,  51 
Eschka's  method  for  sulphur  in  coal,  393 
Etching  test  for  fluorine  (Fig.  33),  176 
Ether,  chromium  detection  by,  132 
Evaluation  of  bauxite,  15 

of  fluorspar,  186 

Evaporation  test  of  lubricating  oils,  575 
Evolution  apparatus  for  sulphur  determina- 
tion (Fig.  64),  599 

method  for  antimony,  28 

method  for  sulphur,  398 
Exit  gases,  sulphur  dioxide  in,  722 

Factors,  conversion,  804,  818-820.     See  also 

"  Tables  "  in  index. 

Fairbanks  cement  testing  machine,  648 
Fairbanks  and   Gooch  method  for  molyb- 
denum, 280 

Fats  (see  under  Oils),  599 
Fatty  acids,  table  of,  603 
Fatty  oils,  test  for  in  lubricating  oils, 

578 
Ferguson's  colorimetric  method  for  bismuth, 

69 

electrolytic  method  for  copper,  159,  173  • 
tables  of  properties,  see  Part  III. 
Ferric    chloride    method    for    determining 
fluorine,  183 

for  tin,  429 
reagent  for  tin,  430 
iron  in  aluminum  salt,  12 
iron,  determination  with  stannous  chloride, 

221 

oxide,  determination  of  iron  as,  213 
oxide,  in  zinc  oxide,  629 
salts,  decomposition  of  iodides  with,  205 
salt,  titanium  determination  with,  437,  438 
Ferro-carbon  titanium,  determination  of  ti- 
tanium in,  gravimetric  method,  436 
determination  of  titanium  in,  volumetric 

method,  438 

determination  of  titanium  in  steel,  441 
Ferrocyanide   solution,    standardization    of, 

480,  482 

method  for  determination  of  copper,  166 
for  lead,  238 
for  zinc,  480-487 
Ferrosilicons,  371 
Ferrous  iron  in  aluminum  salt,  12 
reduction  of  chlorates,  128 

of  chromates,  132 
test  for  platinum,  325 
test  for  palladium,  333 
salts  for  reduction,  chromium  determina- 
tion, 137 
sulphate   method   for   determining   nitric 

acid,  515 
preparation  of  reagents,  517,  518,  519 


SUBJECT   INDEX 


873 


Ferrous  sulphate,  procedure  for  determining 

persulphates,  406 
test  for  nitrates,  292 
Ferro-tungsten  alloys,  451 
typical  analysis  of,  449 
Ferro-vanadium,  det.  vanadium  in,  474 

method  by  American  Vanadium  Co.,  474 
Fertilizers,  mixed,  343 
organic  compounds,  344 
potash  salts,  343 
Field  assay  of  water,  565 
Fineness  in  cement  testing,  642 
Finn's  method  of  basicity  of  white  lead,  626 
Fire  test  of  lubricating  oils,  577 
Fixed  carbon  in  coal,  678 
Fixed  oils,  fats  and  waxes  (see  Oils,  Fats,  and 

Waxes),  566 

Fixed  oils  and  resins  in  varnish,  618 
Flame,  coloration  of,  by  barium,  50 
boron,  79 
calcium,  88 
copper,  149 
potassium,    sodium,    caesium,    lithium, 

and  rubidium,  341,  342 
strontium,  387 

temperature  of,  see  table,  780 
Flash  test  or  point  of  burning  oils,  567 
of  lubricating  oils,  576 
varnish,  618 

Fleming's  gas  absorption  bulb,  98 
Fleming  method  for  carbon  in  steel,  96 
Flint  and  Browning's  method  for  determining 

tellurium,  365 
Flue  gases,  708 

Fluorides,  effect  on  aluminum  precipitation,  8 
Fluoride  of  potassium  reagent,  1 2 
Fluorides,  silica  determination  in  presence 

of,  370 

Fluoride  of  sodium,  evaluation  of,  determin- 
ing sodium  fluoride,   sodium  sulphate, 
sodium   thiosulphate,   sodium   chloride, 
silica,  volatile  matter,  water,  187 
Fluorine,  detection  of,  etching,  black  filter 

and  hanging  drop  tests,  176,  177 
estimation,  gravimetric,  calcium  fluoride 

method,  180 

lead  chloro  fluoride  method,  181 
volumetric  methods,  colorimetric  meth- 
od of  Steiger,  183 
ferric  chloride  method,  183 
silicon  tetrafluoride  method,  Offerman's, 

182 

occurrence  of,  178 

preparation  of  the  sample,  calcium  fluoride, 
hydrofluoric  acid,  organic  substances, 
silicious  ores  and  slags,  soluble  fluor- 
ides, fluorspar,  178,  179 
separation,  from  boric,  hydrochloric,  phos- 
phoric acids,  1 80 
from  silica,  179 
solubility  of  salts,  178 
standard  solutions,  184 
traces,  determination  of,  188 


Fluorspar,  valuation  of,  determining  cal- 
cium carbonate,  calcium  fluoride  and 
silica,  179,  1 86 

Fluosilicic  acid,  precipitation  of  barium 
with,  50 

Foaming  and  priming  in  water,  563 

Foods,  arsenic  in,  45 

Formic  acid  in  acetic  acid,  527 
test  for  iridium,  330 
test  for  palladium,  333 
test  for  platinum,  325 
test  for  rhodium,  336 

Formulae  for  diluting  or  strengthening  acids, 

525 

fluorine  determination,  Merwin's,  186 
heat  value  of  coal,  68 1 

of  gas,  715 

iodine  value  for  SOz,  Reich  test,  722 
lime  and  soda  value  in  water  analysis,  561 
reduction  of  volume  of  gas  to  standard 

volume,  721 

Free  acid  in  aluminum  salts,  12-13 
in  presence  of  iron  salts,  532 
test  in  oils,  596 

French,  chapter  on  water  analysis,  533 
Fresenius,  separation  of  magnesium  and  the 

alkalies  (ref).,  346 
method  for  separating  barium,   calcium, 

and  strontium,  55 
method  for  determining  iodine,  206 
and  Popp,  boric  acid  in  meat,  73 
Friction  test  of  lubricating  oils,  580 
Friedrich's  spiral  gas  washing  bottle   (Fig. 

116),  693 
Fuel  gases,  711 

Fuming  sulphuric  acid  equivalents  (table),  526 
Furfurol  in  acetic  acid,  527,  528 
Fusibility  of  coal,  684 
Fusion  method  for  decomposition  of  rare 

earth  ores,  114 
for  ores  with  selenium  and  tellurium, 

360     • 

for  potassium  bisulphate,  4 
for  sodium  carbonate,  4 
for  sulphur  ores,  393 
for  titanium  ores,  434 
for  tungsten  minerals,  449 
of  ores  with  sodium  hydroxide,  20 
with  sodium  and  potassium  carbonate,  212 

Gang  mold  for  cement  (Fig.  99),  647 
Gardner  and  Schaeffer,  chapter  on  analysis 

of  paints,  609-641 
Gas,  analysis,  687 
apparatus,     absorption    bulbs,    pipettes, 

tubes,  693 

measurement  of  large  quantities  of  gas: 
anemometer,  capometer,  orifice  meter, 
Pitot    tube,  rotameter,    Thomas 
electric  meter,  wet  meter,  689,  692 
measurement  of  small  quantities  of  gas: 
Hempel's  gas  burette,  separatory  fun- 
nel and  graduate,  692 


874 


INDEX 


Gas,   apparatus,  analytical,  Elliott's  appa- 
ratus, 700 
Hempel's,  701 
Orsat's,  697 
Orsat  modified  by  Briggs  and  Scott, 

723 
sampling  tubes,  pump,  containers,  687- 

689 
application  and  interpretation  of  results, 

708 
examination  of  gases,  detection  of,  tables 

of,  694-696 

gases  absorbed  by  silver  nitrate,  695 
by  sulphuric  acid,  694 
by  potassium  hydroxide,  695 
unabsorbed,  696 

acetylene,  det.  oxygen,  hydrogen,  me- 
thane, nitrogen,  sulphur-containing 
gases,  phosphoric,  727 
air,  moisture,  carbon  dioxide,  bacteria, 

carbon  monoxide,  ozone,  729 
chimney  and  flue  gases,  carbon  dioxide, 
indicators,  temperature  determina- 
tion of,  708,  709 
electrolytic  gas,  chlorine  and  other  gases, 

727 

illuminating  gas,  703 
ammonia  in,  717 
calorific  value  of,  713 
candle-power  of,  712 
illuminants  and  oxygen  in,  704 
carbon  dioxide  in,  718 
methane  and  hydrogen  in,  Hempel's 
and  Hinman's  methods,  704,  705 
naphthalene  in,  718 
nitrogen  in,  706 
specific  gravity  of,  718 
sulphur   and   sulphuretted   hydrogen 

m,  716,  717 
tar  in,  720 

mine  gases,  carbon  dioxide  in,  726 
moisture  in  gases,  731 
nitrogen  in  gases,  nitrometer  method,  732 
producers,  fuel  blast  furnace  gases,  722 

dust  determination  in,  712 
sulphuric  acid  gases,  burner  gases,  720 
nitrogen  oxide  in,  726 
sulphur  dioxide  in  exit  gases,  722 

in  inlet  gases,  723 

general  procedures  with  special  apparatus: 
Elliott,  determination  of  carbon   mon- 
oxide, carbon  dioxide,  oxygen,  700, 
701 
Hempel,  determination    of    oxygen    by 

hydrogen  combustion,  703 
by  phosphorus  method,  702 
by  pyrogallate  of  potassium,  703 
illuminating  gas,  703 
Junker's  calorimeter,  713 
Orsat,  determination    of    carbon    mon- 
oxide, carbon  dioxide,  hydrocarbons, 
oxygen,  697,  699 


Gas,  Orsat  apparatus,  modified    by   Briggs 
and     Scott    for    determining    sulphur 
dioxide  in  inlet  gases,  723 
tables,  736-738 

Gasoline  test  for  lubricating  oils,  579 
Gay-Lussac  apparatus  (Fig.  59),  for  silver 

determination,  381 
method  for  determining  silver,  379 
Geissler  absorption  bulb  for  carbon  dioxide 

determination,  96 
Gerhardt  absorption  bulb  for  carbon  dioxide 

determination,  96 

German  silver,  analysis  of,  determining  cop- 
per, lead,  arsenic,  antimony,  and  tin, 
iron,  nickel,  zinc,  669 
Gibb's  method  for  determining  manganese, 

262 
Gill,  chapter  on  fixed  oils,  [fats  and  waxes, 

566-608 

chapter  on  analysis  of  gas,  687-738 
carbon  monoxide  in  atmospheric  air,  729 
on  use  of  sodium  pyrogallate   (note   i), 

oxygen  in  gas,  702 
Gilmore's  needles  (Fig.  95),  645 
Glucinum,  detection  of,  189 

estimation,  gravimetric  method,  190 
occurrence,  189 

separation  from  aluminum,  chromium,  iron, 
manganese,  zirconium,  and  yttrium,  i  QO 
Glycerol,  boric  acid  titration  in,  76,  77 
Gold  detection  of  in  alloys,  192 
benzidine  acetate  test,  193 
phenylhydrazine  acetate  test,  193 
test  for  in  minerals,  192 
estimation,  general  procedures: 
gravimetric,  electrolytic  method,  104 
procedures  of  Cassell,  Moir,  Prister, 

197 

wet  assay  of  minerals,  194 
volumetric  methods: 

colorimetric  method,  197 
iodide  method,  196 
Lenher's  method,  195 
permanganate  method,  195 
preparation  of  proof  gold,  198 
solubility,  198 

Gooch  method  for  determining  lithium,  353 
for  determining  titanium,  modified,  435 
and  Blake's  method  for  determining  bro- 

mates,  82 
and  Bosworth's  method  for    determining 

silver,  384 
and  Ensiger,  separation  of  bromine  from 

iodine,  80 
and  Fairbanks'  method  for  molybdenum, 

280 

and- Jones,  method  for  boron,  75 
Graphite,  carbon  determination  in,  no 
determination  of,  in  crude  mineral,  no 
in  iron  and  steel,  determination  of,  99 
Graphitic  silicon  in  aluminum,  determination 
of,  17 


SUBJECT   INDEX 


875 


Gravimetric   methods.     See   under  element 

in  question. 
Gray's  method,  carbon  residue  test  in  oil,  579 

distillation  flask  (Fig.  91),  579 
Greef  s  method  for  determining  fluorine,  183 
Gregory,  test  for  silver,  375 
Groger,    decomposition    of    chromic     oxide 

(note),  134 

chromium  determination  (note),  137 
Gumming  test  in  lubricating  oils,  578 
Gutbier  and  Hiiller,  method  for  zirconium, 

496 
Gutzeit    apparatus,    arsenic     determination 

(Fig.  6),  46 
method  for  determining  arsenic,  modified, 

46 
Gryory's  method  for  determining  antimony, 

25 
Gypsum,  89 

Hale,  chapter  on  methods  for  analysis  of  coal, 

672 

soap  test  for  hardness  in  water,  560 
starch,  preparation  of,  556 
water  analysis,  565 
Halogens,  separation  and  determination  in 

presence  of  one  another,  130 
Halpen's  test  for  cottonseed  oil,  592 
Handy 's  volumetric  method  for  magnesium, 

256 

Hanging  drop  test  for  fluorine,  177 
Hanus's  method  for  iodine  number  of  oils,  584 
Hardened  oils  (see  Oils,  Fats,  Waxes),  601 
Hard,  lead,  antimony  in,  25 
decomposition  of,  21,  25 
Hardness,  determination  of,  in  water,  557 
Heath,    permanent    copper    standard    solu- 
tion (ref.),  167 

Heath's  solenoid,  rapid  deposition  of  copper 
by,  157 

Heat  passing  up  chimney,  calculation  of,  709 
Heating  test  of  paint  vehicles  (Chinese  wood 

oil),  614 

Helium  in  the  atmosphere,  292 
Hempel  apparatus,  701 
gas  burette  (Fig.  122),  692 
method  for  determining  methane  and  hy- 
drogen, 705  _ 
apparatus    description    (Figs.    122,    123), 

701-703 

Henz  and  Classen  method  for  tin,  430 
Herig  automatic  device  for  burette,  505 
Herting,  volumetric  method  for  tungsten,  454 
Hesse's  method  for  carbon  dioxide  in  at- 
mospheric air  (Fig.  132),  728 
Hexabromide  test  for  linseed  oil,  593 
Hickman,  chapter  on  platinum  and  platinum 

group,  324 
Hicks,  chapter  on  potassium,  sodium,  and 

other  alkalies,  341 

chloroplatinate  method  for  potassium,  350 
Hildebrand  on  Portland  cement  analysis,  652 


Hillebrand,  alkalies  (ref.),  355 

on  silica  determination  (ref.),  372 
Hinman's  method  for  determining  methane 

and  hydrogen,  704 
and  Jenkins,  sulphur  apparatus  (Fig.  127), 

716  m 

volumetric  method  for  sulphur,  404 
Hintz  and  Weber  on  sulphur  precipitation, 

395 

Holde,  caoutchouc  in  lubricating  oil,  578 
Holloway-Eschka    process    for    determining 

mercury,  273 

Hommel's  process  for  separating  molybde- 
num and  tungsten,  452 
Hooper's  method  for  treatment  of  spiesses, 

slags,  mattes,  etc.,  20 
Hoskins'  electric  furnace  (Fig.  107),  684 
Hot  water  precipitation  of  tin,  424 
Howard-Harrison,  fusion  of  sulphide  ores,  20 
Hiibl's  method  for  iodine  number  in  oils,  585 
Hiiller  and  Gutbier  method  for  zirconium, 

496 
Hydrazine  sulphate,  decomposition  of  nitrous 

acid,  296 

reduction  of  chromic  acid,  296 
Hydriodic  acid,  removal  of  from  nitric  acid, 

296 
Hydrobromic  acid,  removal  of  from  nitric 

acid,  296 
Hydrocarbons  in  gas  analysis,  699 

in  illuminating  gas,  704 
Hydrochloric  acid,  detection  of  free,  118 
estimation,  gravimetric  methods  for,  124 

volumetric  methods,  125,  509 
in  presence  of  chloric  and  perchloric  acids, 

129 

impurities  in,  arsenic,  31,  44,  510 
barium  chloride  in,  510 
chlorine,  free,  in,  509 
nitric  acid  and  nitrates  in,  509,  513 
silica  and  total  solids  in,  510 
sulphuric  acid  and  sulphates  in,  509 
preparation  of  arsenic-free  acid  (Fig.  5),  43 
reduction  of  selenic  and  telluric  acids,  365 
in  acetic  acid,  529 
in  ammoniacal  liquors,  298 
basic  or  free  in  bichloride  of  tin,  424 
test  for  iron,  210 
test  for  lead,  233 
test  for  mercury,  270 
test  for  selenium,  359 
test  for  tellurium,  359 
Hydrocyanic  acid,  volumetric  determination, 

no 
Hydrofluoric  acid,  analysis  of,  total  acidity, 

5ii 
gravimetric    estimation,    preparation    of 

sample  for,  179 
hydrofluosilicic  acid  in,  511 
sulphuric  acid  in,  511 
sulphurous  acid  in,  511 
decomposition  of  rare  earth  ores  with,  114 


876 


INDEX 


Hydrofluosalicic  acid  in  hydrofluoric  acid,  5 1 1 
Hydrogen  chloride  gas,  generation  of  (note), 

10 

Hydrogen  combustion  method  for  det.  oxy- 
gen, 703 

determination  in  gas,  704,  705 

in  the  atmosphere,  292 

generator,  734 

reduction  method  for  copper,  173 

reduction  of  rhodium  salts,  336 

reduction  of  tin  ores,  421 
Hydrogen  peroxide,  chromium  detection  by, 

method  for  iodine,  207 

method  for  titanium,  439 

method  for  detecting  vanadium,  463 

test  for  thorium,  416,  418 

-phosphoric  acid  method  for  decompos- 
ing iodides,  207 

Hydrogen  sulphide,  evolution  of  in  sulphur 
• —    det.,  401 
f^stimation  of,  407 

in  ammoniacal  liquors,  299 

in  gas,  717 

in  water,  555 

group,  separation  of,  142,  254,  344 

precipitation  of  molybdenum,  279 

reduction  of  chromates,  132 

reduction  of  ferric  solutions,  215 

test  for  iridium,  330 

test  for  lead,  233 

test  for  mercury,  270 

test  for  nickel,  283 

test  for  palladium,  333 

test  for  platinum,  324 

test  for  rhodium,  336 

test  for  ruthenium,  334 

test  for  selenium,  359 

test  for  tellurium,  359 

test  for  vanadium,  463 

test  for  copper,  149 

Hydrolysis  of  aluminum  salt  with  ammonia,  7 
with  thiosulphate,  9 
method  for  tin,  422 

Hydrometer  for  specific  gravity  of  oils,  569 
Hydroxide  of  aluminum,  precipitation,  7,  9 
effect  of  boiling,  8 
of  bismuth,  precipitation  of,  66 
hydroxylamine  hydrochloride,  551 
Hypochlorite,  test  for,  119 
det.  of,  127 
in  presence  of  Cl,  127 
Hypochlorous  acid,  detection  of,  119 

determination  of,  127 
Hypophosphorous  acid,  test  for,  310 

Ignition  loss  in  asbestine,  china  clay,  silica, 

silex,  631 

in  gypsum,  plaster  of  Paris,  632 
in  barytes  and  blanc  fixe,  632 
Illuminants  in  gas  analysis,  704 
Illuminating  gas,  analysis  of,  703,  712 


Impurities.     See  complete  analysis  of  sub- 
stances in  question. 
Indicators,  499 
Indirect  method  for  determining  sodium  and 

potassium,  352 

Inlet  gases,  sulphur  dioxide  in,  723 
Insecticides,  water-soluble  arsenic  in,  32 
Insoluble  matter  in  asbestine,  china  clay, 

silica,  silex,  631 
in  composite  white  paint,  633 
in  orange  and  yellow  pigments,  639 
residue  in  Portland  cement,  653 
in  sodium  fluoride,  188 
in  sodium  nitrate,  303 
in  zinc  oxide,  628 
barium  sulphate  in,  51,  56 
Interpretation  of  results  in  gas  analysis,  708 
in  mineral  analysis  of  water,  562 
in  sanitary  analysis  of  water,  543 
lodate,  determination  of,  208 

and  periodate  in  a  mixture,  208 
locate  of  potassium,  decomposition  of  iodide 

with,  205 
Iodide  of  potassium,  reduction  of  ferric  solu- 

t\ons  with,  216 

Iodide  method  for  antimony,  26 
method  for  arsenic,  39 
for  chromium  determination,  137 
for  gold  determination,  196 
for  metabi  sulphites,   sulphites,   sulphu- 
rous acid,  thiosulphates,  no 
for  selenium  and  tellurium,  365 
for  determining  tin,  426 
Iodine,  detection  of  free,  combined,  iodate, 

200 

estimation,  general  procedures: 
gravimetric  as  palladous  iodide,  203 

as  silver  iodide,  203 
volumetric  determination   of  hydriodic 

acid  and  soluble  iodides,  203 
liberation    of    iodine    with     chlorine 

(Mohr-Dupre"),  207 
of  ferric  salts,  205 
of  hydrogen  peroxide  and  phosphoric 

acid,  207 

of  iodate  of  potassium,  205 
of   nitrous    acid,  Fresenius    method, 

206 

Volhard's  method,  207 
estimation,  special  procedures: 

in  nitric  acid,  determination  of,  514 
occurrence,  200 

preparation  of  the  sample  for  estimation 
of  iodine  in  iodides,  iodates,  commer- 
cial   iodine,    minerals,    organic    sub- 
stances, phosphates,  water,  201 
separation  from  heavy  metals,  from  bro- 
mine and  chlorine,  202,  203 
solubility  of  the  element  and  its  salts,  200 
Iodine  jelly  test  of  paint  vehicles,  614 
number  (Hiibl),  in  oil  analysis,  583,  613 
standard  solution  of  (see  Reagents),  28 


SUBJECT   INDEX 


877 


Iridium,  detection  of,  330 

estimation,    gravimetric   methods   by   ig- 
nition of: 

ammonium  iridium  chloride,  331 
reduction  with  zinc,  331 
obtaining  as  residue,  332 
preparation  of  the  sample  for  analysis,  330 
properties  of,  330 
separation  from  platinum,  331 
Iron,  detection  of,  tests  with  hydrochloric 
acid,  ferrocyanide,  salicylic  acid,  sodium 
peroxide,  sulphocyanate,  210 
distinction    between    ferrous    and    ferric 

salts,  210 
estimation,  general  procedures: 

gravimetric,     determination     as     ferric 

oxide,  Fe2O3,  213 
cupferron  method,  214 
volumetric     methods,    oxidation    pro- 
cedure!^: 

preliminary  reduction  with  hydrogen 
sulphide,  metal,  potassium  iodide, 
sulphurous  acid,  test  lead,  zinc,  215, 
216 

potassium  dichromate  method,  216 
potassium  permanganate  method,  218 
reduction    procedure    with   stannous 

chloride,  221 
estimation,  special  procedures: 

determination  in  alloys  and  metals: 
in  brass  and  bronze,  660 
in  Britannia  metal,  667 
in  copper,  168 
in  German  silver,  669 
in  lead,  252 

in  manganese  phosphorus  bronze,  670 
in  Rose's  metal,  664 
in  spelter,  490 
in  type  metal,  660 
determination  in  bauxite,  15 
.  in  paint  pigments  (iron  oxides),  629, 

633,  637,  640 
in  phosphates,  320,  322 
in  Portland  cement,  651 
in  sand,  374 
in  sodium  nitrate,  303 
in  spent  oxide,  415 
in  titaniferous  ores,  446 
in  water,  as  ferrous  and  ferric  iron,  547 
determination  of  in  presence  of  vana- 
dium, 469,  472 

industrial  application  of  methods,  210 
occurrence,  ores  and  minerals,  carbonates, 

oxides,  sulphides,  210,  211 
preparation  and  solution  of  the  sample, 

iron  and  steel,  212 

ores,  soluble  salts,  silicates,  etc.,  211,  212 
separation.     See  element  from  which  sep- 
aration is  desired. 

solubilities,  general  considerations,  211 
traces,  salicylic  acid  method,  223 
sulphocyanate  method,  222 


Iron  and  steel  analysis,  decomposition  of,  for 

determining  iron,  212 
determination  of  aluminum  in,  16 
arsenic  in,  33 

carbon  in,  combined,  colorimetric  de- 
termination, 108,  224 
graphitic,  227 
-     total,  95-101,  225 
chromium  in,  134 
cobalt  in,  148 
manganese  in,  bismuthate  method  for, 

228,  263 

Deshey's  method,  227,  268 
persulphate  method,  227,  267 
Volhard's  method,  266 
determination  in  spiegel  iron,  268 
molybdenum  in,  276,  278 
nickel  in,  285 

phosphorus  in,  229,  316-318 
silicon  in,  231,  371 
rapid  foundry  method  of  determina- 
tion, 232 

sulphur  in,  gravimetric,  230 
volumetric,  229,  398-402 
titanium  in,  441 
tungsten  in,  448,  450 
vanadium  in,  464,  471,  475 
specifications  for  elements  in  steel: 
carbon,  228 
manganese,  228 
phosphorus,  229 
silicon,  232 
sulphur,  231 

Iron  ores  and  iron-ore  briquettes,  copper  de- 
termination in,  152 

ore  briquettes,  reduction  for  sulphur  de- 
termination, 400 
separation  from  chromium,  134 
sulphide,  available  H2S  in,  401,  407 
Irrigating  waters,  564 

Jannasch    method    for    separation    of    the 

halogens,  202 

metallic  test  for  palladium,  333 
for  platinum,  325 
for  rhodium,  336 
for  iodine  (ref.),  123 
precipitation  of  bismuth  hydroxide,  67 
Jenkins'    apparatus   for   specific  gravity  of 

gas  (Fig.  129),  719 
and  Hinman  gas-sulphur  apparatus  (Fig. 

127),  716 

Jolly's  method  for  traces  of  thorium,  418 
Jones  reductor  apparatus  (Fig.  40),  220 

method    for    iron    determination,    216, 

219 
method  for  molybdenum  determination, 

281 
method  for  phosphorus  determination, 

3i7 
Junker's  calorimeter  (Figs.  124,  125,  126), 


878 


INDEX 


Kehrmann's    separation    of    tungsten    from 
arsenic  and  phosphorus,  452 

Keller's  method  for  separating  selenium  and 
tellurium,  361 

Kelly,  traces  of  antimony,  29 

Kempf's  oxalic  acid  method  for  determina- 
tion of  persulphates,  406 

Kjeldahl  digestion  for  nitrogen  determina- 
tion, 294 

Kneeland,  decomposition  of  ores  and  slags, 
178 

Knorr's  persulphate  method  for  determining 

manganese  in  water,  550 
apparatus,   modified,   for   carbon   dioxide 

determination,  104 
method  for  purification  of  silver,  385 

Krypton  in  the  atmosphere,  292 

Lacmoid  indicator,  preparation  of,  608 

uses  of,  500 

Landrum,  cobalt  in  cobalt  oxide,  145 
cobalt  in  enamels,  147 
method  for  cobalt  in  enamels,  147 
Lanthanum,  112,  113 
Lard,  cottonseed  oil  in,  600 

water  in,  600 
Lawrence  Smith  (J.),  method  for  alkalies  in 

silicates,  355 

Lead,  detection  of,  tests  with  hydrochloric 
acid,  hydrogen  sulphide,  potassium  di- 
chromate  and  potassium  chromate,  233 
estimation,  general  procedures: 

gravimetric    method,    determining    as 

chromate,  PbCrC>4,  236 
as  molybdate,  PbMoO4,  237 
as  peroxide,  PbC>2,  by  electrolysis,  238 
as  sulphate,  PbSO4,  236 
volumetric  methods,  ferrocyanide  titra- 

tion,  238 

molybdate  method  of  Alexander,  239 
estimation,  special  procedures: 
determination  in   alloys  and  metals  in 

brass  and  bronze,  668 
in  Britannia  metal,  667 
in  copper,  169 

in  manganese  phosphorus  bronze,  670 
in  Rose's  metal,  663 
in  soft  solders,  662 
in  spelter  (electrolytic  and  lead  acid 

methods),  489 
in  type  metal,  660 
in  Wood's  metal,  664 
determination  in  paint  pigments,  chrome 

green  and  yellow,  639,  640 
in  corroded  white  lead   (volumetric 

and  gravimetric),  625 
in  metallic  lead,  626 
in  red  lead  and  orange  mineral,  635 
in  sublimed  blue  lead,  638 
in  sublimed  white  lead,  623 
in  yellow  basic  lead  chromate,  639 
in  zinc  lead  and  leaded  zinc,  627 


Lead,  estimation,    determination    in    small 

quantities  (see  Traces  in  Water),  557 
impurities  in  metallic  lead: 
antimony  in  hard  lead,  25 
bismuth  in  lead  bullion,  63 
complete  analysis  of  pig  lead,  determin- 
ing bismuth,  silver,  arsenic,  anti- 
mony,   tin,    iron,    cobalt,    nickel, 
manganese,  zinc,  248-252 
industrial  application  of  methods,  233 
occurrence,  minerals,  ores,  alloys,  etc.,  233 
preparation  and  solution  of  the  samples — 

minerals,  ores,  alloys,  etc.,  234 
separations,  isolation  of  lead  as  sulphate, 

235 
extraction  of  the  impure  sulphate  by 

ammonium  acetate,  235,  241 
separation  from  barium,  235 
solubilities  of  metallic  lead  and  its  salts, 

233 

traces,  determination  of: 
gravimetric  from  large  amounts  of  sub- 
stances: 

a.  acetate  extraction,  241 

b.  occlusion  by  precipitate  of  another 

metal,  242 

c.  Seeker-Clayton  method,  modified, 

243 

volumetric,  colorimetric  method,  243 
Lead  acetate  method  for  precipitating  vana- 
dium, 468 

test  for  chromate,  132 
test  paper,  43 

Lead-arsenate,  arsenic  determination  in,  32 
bullion,  bismuth  determination  in,  63 
carbonate  in  sublimed  blue  lead,  638 
chloro-fluoride  method  for  fluorine  deter- 
mination, 181 
molybdate  method  for  determining  lead, 

237 
method  for  determining  molybdenum, 

278 
oxide,  electrolytic  method,  628 

method  for  manganese  in  steel,  227 
peroxide  in  red  lead,  635 
sulphate,   decomposition   of,   for   sulphur 

determination,  394 
in  sublimed  blue  lead,  638 
sulphide  in  sublimed  blue  lead,  638 
sulphite  in  sublimed  blue  lead,  638 
Le   Blanc   and   Eckardt's   ferrous   sulphate 

method  for  persulphates,  406 
Le   Chatelier's    specific  gravity  apparatus, 

643 
Lenher's  method  for  gold,  196 

-Crawford  thymol  method  for  titanium,  444 
and  Trogg,   precautions  on  silica  deter- 
mination, 373 
Lennsen's   iodide    method  for  tin,    Baker's 

modification,  426 
Lewkowitsch  on  oil  tests,  591 
Liebermann-Storch's  test  for  rosin  oil,  595 


SUBJECT   INDEX 


879 


Liebig's  absorption  bulb,  95 

method  for  determining  hydrocyanic  acid 

and  cyanides,  in 
Liddell  on  dust  in  gas,  712 

"Metallurgists'  Handbook"  (ref.),  385 
Lime,  effect  of  in  silica  dehydration,  372 
method  for  halogens  in  organic  matter, 

122 

in  sand,  374 

-value  in  water  analysis,  650 
in  silicate  of  soda,  374 
and   limestone   determination   in   cement 

analysis,  651,  658 
water  test  for  magnesium,  253 
Limestone,  lime,  cement  rock,  analysis  of,  658 
Lindo-Gladding's  method  for  potassium,  351 
Linseed  oil  (see  Oils,  Fats  and  Waxes),  593. 
Lithium,  detection  of,  342 

estimation,  general  procedures: 
as  lithium  chloride,  353 
as  lithium  sulphate,  353 
Gooch's  method,  353 
Rammelsberg's  method,  354 
spectroscopic  method,  354 
sodium  and  potassium  determination  in 

presence  of  one  another,  355 
Lithopone,  analysis  of,  630 
Litmus  indicator,  uses  of,  500 
Little-Cahen-Morgan,  det.  arsenic  in  organic 

matter,  32 
Loss  of  weight  method  for  carbonates,  106 

on  ignition  in  Portland  cement,  652 
Low,  electrolytic  method  for  cobalt,  144 
method  for  decomposing  antimony  ores, 


Lower  oxides  in  nitric  acid,  514 
in  oleum  and  mixed  acids,  523 

Lubricating    oils     (see    under    Oils,    Fats, 
Waxes),  572 

Lunge-Marchlewski  method  for  carbon,  ref.), 

107 
-Ray  pipette  for  weighing  of  liquids,  506 

Luteol  indicator,  425 


Mackey's  apparatus  for  spontaneous  com- 
bustion-oils, 596 

Magenta  test  for  bromine,  78,  82 
Magnesia,  effect  on  silica  dehydration,  372 
Magnesium,  detection  of,  253 

estimation,  methods  for  determining,  gen- 
eral: 
gravimetric,    as    magnesium   pyrophos- 

phate,  255 

volumetric,  titration  of  ammonium  mag- 
nesium phosphate,  256 
estimation,  special  methods: 
determination  in  gypsum,  632 
in  sand,  374 
in  silicate  of  soda,  374 
in  sodium  nitrate,  304 
in  water,  549,  560 


Magnesium,  estimation,  in  composite  white 

paint,  634 

in  green  pigments,  640 
in  orange  and  yellow  pigments,  639 
in  Portland  cement,  651 
with  sodium  and  potassium  in  presence 

of  one  another,  estimation  of,  352 
occurrence,  253 
preparation  and  solution  of  the  sample — 

ores,  253 
separation   from    the   hydrogen   sulphide 

group,  Cu,  Pb,  Cd,  As,  etc.,  254 
from  iron,  aluminum,  manganese,  and 

zinc,  254 

from  the  alkaline  earths,  53,  254 
solubility,  253 
Magnesium  ammonium  phosphate  method 

for  phosphorus,  315 
determination  in  water,  549 
chloride  in  water,  559 
metallic,  test  for  platinum,  325 
pyroarsenate  method  for  arsenic,  37 
pyrophosphate  method  for  phosphorus,  315 
sulphate,  arsenic  in,  45 
Maletesta  and  De  Nola,  silver  determination, 

376 
Manganese,  detection  of,  general  procedure 

and  bead  test,  257 

in  soils,  minerals,  vegetables,  etc.,  257 
estimation,  general  methods: 
gravimetric,   as  manganese,   pyrophos- 
phate, 262 

volumetric,  bismuthate  method,  263 
lead  oxide  method,  268 
persulphate  method,  267 
Volhard's  method,  268 
estimation,  special  procedures: 

determination  in  iron  and  steel,  227, 228 
in  metallic  lead,  252 
in  phosphorus  bronze,  670 
in  spiegel  iron,  268 
in  water,  550 

preparation  and  solution  of  the  sample, 
alloys,  ferro-aluminum,  ferro-chro- 
mium,  ferro-titanium,  manganese, 
bronze,  molybdenum  and  tungsten 
alloys,  silicon  alloys;  iron  and  steel; 
ores,  iron  ores,  sulphides,  slags,  258 
separation  from  H2S  group,  alkaline  earths 

and  alkalies,  nickel  and  cobalt,  260 
from  iron  and  alumina  by  basic  acetate 

method,  260 
by  precipitation  of  manganese  as  dioxide, 

MnO2,  261 

solubility  of  the  metal  and  its  oxides,  258 
Manganese  dioxide  in  zinc  oxide,  629 
Manganese  oxide  in  paint  pigments,  629 
-phosphorus     bronze,     analysis     of     (see 

Alloys),  670 

Mannitol,  boric  acid  titration  in,  76,  77 
Marsh,  electrolysis  of  nickel,  289 
Martin,  on  absorption  apparatus  for  C02,  98 


880 


INDEX 


Matte,  copper,  solution  of,  151 

Mattes,  decomposition  of,  20 

Maumene  test  for  oils,  582 

McDonnell  and  Roark  arsenic  separation,  33 

McDowell,  method  for  hydrocyanic  acid,  no 

Meade,  chapter  on  cements,  642-658 

Meat,  arsenic  in,  45 

boron  in,  73 
Meiklejohn,  properties  of  compounds,  table 

XVII,  801-803 

Mellor,  calcium  oxalate,  decomposition  of,  91 
on  precipitation  of  tungsten,  454 
traces  of  lead,  244 
Melting  temperature  of  elements,  table  of, 

780 

Mene,  ferric  chloride  method  for  tin,  429 
Mennick,  chloric  and  perchloric  acids,  129 
Mercuric  cyanide  test  for  palladium,  332 
oxide    method    for    separating    magnesia 

from  the  alkalies,  346 
Mercurous  nitrate  method  for  precipitating 

molybdenum,  278 

method  for  precipitating  tungsten,  454 
method  for  precipitating  vanadium,  467 
test  for  chroma te,  132 

Mercury  chloride  paper,  arsenic  determina- 
tion, 41 

Mercury,  cleaning  of,  735 
detection  of,  270 

estimation,  methods  of  procedure: 
gravimetric,  electrolytic  method,  272 
Hallo way-Eschka  method,  273 
sulphide,  precipitation,  272 
volumetric,  by  Seamen's  process,  274 
occurrence,  270 
preparation  and  solution  of  the  sample, 

ores,  270,  271 

purification  of  the  reagent,  735 
separation  from  members  of  subsequent 

groups,  271 
from  As,  Sb,  Sn,  Pb,  Bi,  Cu,  Cd,  Se,  Te, 

271 

from  organic  substances,  271 
solubility,  270 
Merwin  color  screens,  342 

and  Steigers'  method  for  fluorine,  183 
Metabisulphite,    gravimetric    determination 

of,  409 

volumetric  iodine  method  for,  410 
determination  in  presence  of  carbonates, 
chlorides,   sulphates,  sulphites,   thio- 
sulphates,  412 
Metallic  aluminum  and  its  alloys,  5 

silicon  and  iron  in,  17 
cobalt,  cobalt  in,  141,  146 
copper,  metallic,  152 
determination  of  gold,  silver,  lead,  bis- 
muth, arsenic,  antimony,  selenium, 
tellurium,  iron,  zinc,  nickel,  cobalt, 
oxygen,  sulphur,  phosphorus,  chlo- 
rine in,  167-174 
gold,  preparation  of  proof,  198 


Metallic   iron    (and   steel).     See  index  for 

iron  and  steel  analysis, 
technical  determinations  of  carbon,  man- 
ganese,   phosphorus,    silicon,    sul- 
phur in,  223-232 

chromium,  cobalt,  nickel,  titanium, 
tungsten,  vanadium.  See  Iron  and 
Steel  Analysis. 

lead,    determination    of    silver,    bismuth, 
copper,  cadmium,  arsenic,  antimony, 
tin,  iron,  cobalt,  nickel,  manganese, 
zinc  in,  248-252 
nickel,  cobalt  in,  146 
platinum,  328 

silver,  preparation  of  pure,  384 
zinc  in  zinc  dust,  487 

impurities,  lead,  iron,'cadmium  in  spelter, 

480-492 

Metallurgist,  96 
Metals.     See  Metallic. 
Metaphosphoric  acid,  test  for,  310 
Meter,    wet   meter,    rotameter,    capometer, 
Thomas   electric   meter,   orifice   meter, 
anemometer,  689-692 
Methane,  determination  of,  704,  705 
Methyl  borate,  distillation  of  boron  as,  74 
Methyl  orange  indicator,  26,  301,  499,  500 

red  indicator,  uses  of,  499 
Metzel  and  Vortman,  method  for  antimony, 

23 
Meyer's  apparatus  for  zinc  determination 

(Figs.  72,  73,  74),  488 
Microchemical  examination  of  crystals  for 

tantalic  and  columbic  acids,  455 
Microscopical  test  of  lubricating  oils,  580 
Milk,  boron  in,  73 
Mine  gases,  carbon  dioxide  in,  726 
Mineral  analysis  of  water,  545 

residue  in  water,  555 

Minerals,  decomposition  of,  for  determina- 
tion of  lead,  234 
detection  of  tungsten  in,  448 
Mineral  salts  in  burning  oils,  571 
Minerals,  tests  for  gold  in,  192 

See  list  under  dominating  elements  con- 
tained in,  Part  I 

Mispickel,    preparation   for   arsenic    deter- 
mination, 33 
Mixtures,  sodium  and  potassium  carbonates 

and  hydrates,  531 
Mohr's  alkalimeter,  106 

method  (modified)  for  antimony,  27 
for  arsenic,  39 
for  chlorine,  126 
for  iodine,  207 
Moir's  method  for  gold,  197 
Moisture  in  air,  292,  502,  728,  736 
in  arsenic,  commercial,  47 
in  bauxite,  15 
in  brimstone,  415 
in  butter  and  fats,  599,  600 
in  coal,  674 


SUBJECT  INDEX 


881 


Moisture  in  gases,  731 
in  nitrate  of  soda,  303 
in  oils  (burning),  571,  600 
in  paints  and  paint  pigments,  611,  630, 

631,'  632,  634,  637,  638,  639,  640 
in  phosphate  rock,  310 
in  silicate  of  soda,  374 
in  silicates,  369 
in  sodium  fluoride,  188 
in  zinc  pulp,  478 
Molybdate  method  for  lead,  gravimetric,  237 

volumetric,  239 

Molybdenite,  comparison  with  graphite,  275 
Molybdenum,  detection,  general  procedure, 

275 

tests  with  sodium  thiosulphate,  sulphur 
dioxide,   disodium  phosphate,   sul- 
phuric acid,  275 
estimation,  general  procedures: 

gravimetric,  lead  molybdate  method,  278 
mercurous  nitrate,  precipitation  by, 

278 

molybdenum  sulphide  method,  279 
volumetric,  iodometric  reduction  meth- 
od, 280 
zinc  reduction  with  Jones'  reductor, 

281 
determination  in  presence  of  vanadium, 

282,  471 
occurrence,  275 
preparation  and  solution  of  the  sample, 

ores,  276 

iron  and  steel,  276 
separation  from  iron,  276 
from  alkalies,  alkaline  earths,  bismuth, 
cadmium,    copper,    lead,    arsenic, 
titanium,  vanadium,  tungsten,  phos- 
phoric acid,  277 
solubilities,  276 

Monazite,  decomposition  of,  416 
Morgan-Cahen-Little,  arsenic  det.  in  organic 

matter,  32 

Morphine  test  for  titanium,  432 
Mortar,   standard  sand,  water,  percentage 
for  (table),  645 


Naphthalene  in  gas,  718 

Naphthylamine  acetate  reagent,  538 

National    Brass    and    Copper    Tube    Co., 
method  for  brass  analysis,  174 

National  Lead  Co.,  method  (modified),  for 
metallic  lead  analysis,  248 

Natural  cement,  U.  S.  Gov.,  specifications 
for  fineness,  642 

Neon  in  the  atmosphere,  292 

Nephelometric  method  for  silver,  384 

Nessler  jars  for  colorimetric  titanium  deter- 
mination, 442 

Nessler 's  method  for  ammonia,  537 
test  for  ammonia,  291 

Newton,  method  for  titanium,  437 


New  York  State  Board  of  Health  tester  for 

oil,  567 
Nickel,    detection    of,    hydrogen    sulphide 

test  283 
dimethylglyoxime     and    alpha    benzildi- 

oxime  tests,  283 
estimation,  general  procedures: 

gravimetric,  alpha  benzildioxime  method, 

286 

dimethylglyoxime  method,  287 
electrolytic  method,  289 
volumetric  method  of  Parr  and  Lindgren, 

290 

estimation,     special    procedures,    nickel- 
plating  solutions,  290 
determination  in  alloys,  German  silver, 

669 

in  copper,  169,  170 
in  German  silver,  669 
in  metallic  lead,  252 
preparation  and  solution  of  the  sample, 

general  procedure  for  ores,  284 
metallic  nickel  and  its  alloys,  284 
separation  from  alkalies,  alkaline  earths, 
and  members  of  the  hydrogen  sul- 
phide group,  285 
from  aluminum,  chromium,  cobalt,  iron, 

manganese,  zinc,  285,  286 
solubilities,  284 
Nickel-plating    solution,    determination    of 

nickel  in,  290 

Niobium.     See  Columbium,  448 
Nitrate,  standard  solution  of,  540 
of  soda,  analysis  of,  moisture,  insoluble 
matter,    sodium   sulphate,    iron   and 
aluminum    oxides,    lime,    magnesia, 
sodium  chloride,  carbon  dioxide,  303 
Nitrates,  removal  of,  in  sulphur  determin- 
ation, 395 

Nitric  acid,  complete  analysis  of,  512-515 
determination  of  acidity,  chlorine,  hydro- 
chloric acid,  iodine,  nitrous  acid,  sul- 
phuric acid,  512-515 
arsenic  in,  44 

by  ferrous  sulphate  method,  515 
in  arsenic  acid,  ferrous  sulphate  method, 

5i9 

in  hydrochloric  acid,  509 
in  commercial  nitric  acid,  514 
in  mixed  acid,  ferrous  sulphate  method, 

295 

in  oleum,  nitrometer  method,  309 
in    phosphoric    acid,    ferrous    sulphate 

method,  519 
in    sulphuric    acid,    [ferrous     sulphate 

method,  517 

N/io    reagent    for    phosphate    deter- 
mination, 316 
Nitrite,  permanganate  method  for,  521,  523 

in  water,  538 

Nitrogen,  detection  of,  combined  as: 
ammonia,  tests  for,  291 


882 


INDEX 


Nitrogen,  ammonia,  Nessler's  test,  291 
nitric  acid,  copper  test  for,  292 
diphenylamine  test  for,  292 
ferrous  sulphate  test  for,  291 
phenolsulphonic  acid  test  for,  292 
nitrous  acid,  acetic  acid  test  for,  292, 

permanganate  test  for,  292 
organic  nitrogen,  291 
estimation,    free,    combined,    and    total 

nitrogen,  292 

combined  nitrogen,  methods  for: 
ammonia,  gravimetric  determination 

of,  296 

combined  and  free,  volumetric  de- 
termination, 297,  536,  537 
traces,  299,  536,  537 
ammoniacal  liquor,   analysis  of,   de- 
termining carbon  dioxide,  hydro- 
chloric acid,  hydrogen  sulphide, 
sulphuric  acid,  ammonia,  298,  299 
nitrate  of  soda,  303 
nitrates,  Devarda  method  modified, 

300 

as  nitrate  in  water,  539 
as  nitric  acid,  gravimetric  method  as 

nitron  nitrate,  299 
volumetric,  300 
complete  analysis  of   (see  subject 

above),  512 
as  nitrite  in  water,  538 
as  organic  nitrogen  in  water,  537 
nitrogen  in  green  pigments,  640 
in  organic  matter,   nitrates  being 

absent,  294 
in  organic  matter  hi  presence  of 

nitrates,  295 
in  soil  extracts,  304 
free  nitrogen.     See  Gas  Analysis,  706 
per  cent  of,  in  air,  292 
tetroxide  in  gas,  726 
occurrence,  292 
preparation   of    the   sample,    ammonium 

salts  and  mixtures,  295 
nitrates  in  soils,  nitric  acids  and  mixed 

acids,  295 

organic  substances  in  presence  or  ab- 
sence of  nitrates,  294,  295 
separations,  ammonia,  isolation  of,  295 
nitric  acid,  isolation  of,  296 

removal  of  impurities,  nitrous,  chro- 
mic,    hydrobromic,     hydroiodic 
acids,  296 
solubilities,  293 
special  methods,   nitrometer  method  for 

nitrates  and  nitrites,  305 
nitrometer  of  Dupont,  306 

nitric  acid  in  oleum,  309 
Nitron  nitrate  method  for  nitric  acid,  296,  299 
Nitrometer,  305,  306 

gas  analysis,  Fig.  136,  732 
Nitroso-beta-naphthol,  precipitation  of  co- 
balt with,  143 


Nitrous  acid,  decomposing  of  iodides  with,  206 
permanganate  method  for,  520 
and  lower  oxides  in   nitric  acid,  514, 

521 

in  oleum  and  mixed  acids,  524 
gas,  generation  of,  80,  123 
removal  of,  from  nitric  acid,  296 
oxide  in  gas,  726 
Non-drying  oils,  list  of,  602 
Normal  consistency  of   cement,  method   of 
determination,  644 

Occurrence.     See  under  element  in  question. 

Odor  test  of  water,  535 

Overman's  method  for  fluorine,  182 

Oils,  fats,  waxes,  examination  of  unknown 

oil,  566 

detection  of  oils  in  paint  vehicles,  612 
classified    list,    characteristics,    and    con- 
stants of  oils  ^tables),  603-606,  616 
examination  of: 

animal  and  vegetable  oils,  580 
general  test  for,  590 
acetyl  value,  591 
antifluorescence,  test  for,  591 
bromine  number,  586 
elaidin  test,  582 
iodine  number,  583 
Hanus's  method,  584 
Hiibl's  method,  585 
in  oxidized  oils,  586 
Maumene  test,- 582 
refractive  index,  581 
saponification  value,  587 
unsaponifiable     oils,   detection    of, 

588 

Valenta  test  for,  681 
special  tests  for  certain  oils,  591 
cottonseed  oil,  Becki's  test  for,  592 

Halpen's  test  for,  592 
drying  on  glass,  598 
free  acid  in,  596 
linseed   oil,   hexabromide   test  for, 

593 

peanut  oil,  Renard's  test  for,  594 
rapeseed  oil,  Bech's  test  for,  595 
rosin   oil,   Liebermann-Storch    test 

for,  595 
sesame  oil,  Baudoin's  or  Camoin's 

test,  595 
spontaneous  combustion    test, 

Mackey's  apparatus,  596 
titer  test,  598 
fats,  edible,  599 

butter,  examination  of,  599 
lard,  600 

hardened  oils,  601 

miscellaneous  oils  and  lubricants,  601 
paint  oils  (see  under  Paints  and  Paint  Pig- 
ments), 612 

Chinese  wood  oil,  tung  oil  (see  subject 
under  Paints),  613-615 


SUBJECT   INDEX 


883 


Oils,  paint,  acid  number,  heating  test,  iodine 
jelly  test,  iodine  number,  refrac- 
tive index,  saponification  number, 
•  unsaponifiable     matter,    specific 
gravity,  standards  of,  613-615 
turpentine  (see  subject  under  Paints), 

617,  618 

color,  distillation,  polimerization,  re- 
fractive  index,   specific  gravity, 
standards  of,  617,  618 
varnish  (see  subject),  618-620 
petroleum  products,  567 
burning  oils,  567 

acidity,  detection  of,  571 
color  of,  572 
distillation  test,  569 
fire  test,  568 
flash  test,  567 
mineral  salts  in,  571 
specific  gravity'of,  569 
sulphuric  acid  test,  571 
sulphur  determination  in,  570 
water  in,  571 
lubricating  oils,  572 

carbon  residue  test  for  in,  579 

caoutchouc,  test  for  in,  578 

•evaporation  test  of,  575 

fatty  oils,  test  for  in,  578 

fire  test  of,  577 

flash  test  of,  576 

friction  test-of,  580 

gasoline  test  of,  579 

gumming  test  of,  578 

microscopical  test  of,  580 

soap,  detection  of  in,  578 

specific      gravity      of,      hydrometer 

method,  569 

Westphal  balance  method,  569 
viscosity,  572 

absolute  method,  575 
Engler's  viscosimeter,  572 
Saybolt  viscosimeter,  573 
Universal  viscosimeter,  573 
Oil  in  black  pigments,  640 
Oils,  reagents  used  in,  607 

tables   of   characteristics   and   constants, 

fatty  acids,  603 
mineral  oils,  properties  of,  601 
vegetable  and  animal  oils,  604,  605 
waxes,  601,  606 
viscosity  conversion  tables,  607 

Saybolt,  Engler,  and  Redwood  times, 

607 
Oleum,  complete  analysis  of,  522 

acidity,  lower    oxides,    nitric    acid,    sul- 
phuric anhydride  in,  522-524 
table  of  equivalents,  526 
Olsen,  chapter  on  analysis  of  alloys,  659-671 

test  for  fluorine,  177 
Optical  pyrometer  (Fig.  107),  684 
Ores.     See    under   Preparation  of   Samples 
of  Various  Elements. 


Orifice  meter,  692 

Organic  matter,  arsenic  determination  in,  32, 

45 
decomposition  of  for  determination  of 

antimony  in,  21 
for  determining  barium,  51 
boron,  73 
bromine,  79 

chlorine  and  the  halogens,  121-122 
Carius  method  for  halogens  in,  121 
lime  method  for  halogens  in,  122 
sodium  peroxide  method  for  hal- 
ogens in,  122 
fluorine,  178 
iodine,  201 
determination    of    carbon    in    organic 

matter,  101-103 
nitrogen,  293 

phosphorus  in  baking  powder,  313 
potassium  in  soils,  fertilizers,  plants, 

343,  344 

organic  matter  in  water,  541,  543 
Orsat  apparatus  (Fig.   120),  modified  (Fig. 

131),  697,  723 
Osmium,  detection  of,  337 

estimation,  gravimetric  methods  for,  338 
occurrence,  337 

preparation  and  solution  of  the  sample,  338 
properties,  337 

Owen-Bradbury  method  for  alkali  carbonates 
and  hydrates  in  presence  of  each  other, 

53i 

Owens,  chapter  on  Rare  Earths,  112 
on  Thorium,  416, 
on  Zirconium,  494 
Oxalate  method  separation  of  alkaline  earths 

from  the  alkalies  and  magnesium,  53 
Oxalates  of  the  rare  earths,  outline  for  sep- 
aration of,  117 

Oxalic  acid  method  fo:  persulphates,  406 
Oxidation  methods  for  determining  iron,  215 
in  platinum  salts,  325 
test  for  vanadium,  463 
Oxide,  estimation  of  elements  as.     See  index 
of  following  elements:    Aluminum,  bis- 
muth, chromium,  cobalt,  copper,  iron, 
lead,  manganese,  molybdenum,  nickel, 
silicon,  sulphur,  tin,  titanium,  tungsten, 
columbium    and    tantalum,     uranium, 
vanadium,  zinc,  zirconium. 
Oxides  of  cobalt,  141,  145 
copper,  151,  162 
iron,  210,  211 
thorium,  417 
titanium,  433 
tungsten,  449 
uranium,  459 
vanadium,  465 
zirconium,  495,  496 
Oxidized  oils,  iodine  number  of,  586 
Oxygen  consumed  in  water  (organic  matter 
in),  54i 


884 


INDEX 


Oxygen  cylinders,    illustrating    method    of 

connecting,  680 
determination  of,  in  air,  absorption  with 

phosphorus,  702 
potassium  pyrogallate,  703 
sodium  pyrogallate  (note),  702 
in  copper,  172 

in  gas,  292,  698,  700,  702,  703,  704 
dissolved  in  water,  556 
explosion  with  hydrogen,  703 

Paints  and  Paint  Vehicles,  analysis  of  (see 

Outline  in  Table  of  Contents),  609 
pigments,  classification  of,  621 
black  pigments,  analysis  of,  640 
blue  pigments,  analysis  of,  637 

Prussian  blue,  Chinese  blue,  Antwerp 

blue,  638 

sublimed  blue  lead,  638 
ultramarine  blue,  637 
green  pigments,  analysis  of,  639 

chrome  green,  639 
red  and  brown  pigments,  634 
iron  oxides,  637 
red  lead,  orange  mineral,  634 
vermilion,  636 

yellow  and  orange  pigments,  chrome  yel- 
low, American  vermilion,  basic  lead 
chromate,  639 
white  pigments,  622 
baiytes  and  blanc  fixe,  632 
composite  white  paint,  633 
corroded  white  lead,  625 
lithopone,  630 
silica,   silex,   China     clay,   asbestine, 

631 

sublimed  white  lead,  632 
whiting,  Paris  white,  632 
zinc  lead  and  leaded  zinc,  626 
zinc  oxide,  627 
vehicles,  610 

liquid,  percentage  of,  610 
separation  of  components,  611 
resinates,  detection  of,  612 
oils,  detection  of,  iodine  number,  612 
Chinese  wood  oil,  or  tung  oil  (see  under 

Oils,  Fats,  Waxes),  613-615 
constants  for  various  oils,  615,  616 
turpentine,  examination  of  (see  details 
under  subject  turpentine),  617,  618 
varnish,  examination  of  (see  details  under 

subject,  Varnish),  618-620 
other  materials,  620 
Palladium,  detection  of,  332 

estimation,  gravimetric  methods,  333 

properties  of,  332 

Kparatipo  from  gold  and  silver,  333 

from  iridium  and  platinum,  333 
Fallacious  chloride  reagent,  735 

iodide,  method  for  determining  iodine,  203 
Palmer  and  Allen  modified  Gutzeit  method 
for  arsenic,  40 


Paris  white,  paint  pigment,  632 

Parr  and  Lindgren's  method  for  nickel,  290 

Parrodi-Mascazzini  electrolytic  method  for 
antimony,  modified,  24 

Parsons  and  Barnes'  method  for  glucinum, 
190 

Pat  for  determining  setting  time  and  sound- 
ness in  cement,  646 

Pats  showing  sound  and    unsound    cement, 
after  steaming,  646 

Patterson,  determination  of  manganese,  262 

Peanut  oil  (see  under'Oils,  Fats,  Waxes),  594 

Pechard's    process    for    separating    molyb- 
denum from  tungsten,  453 

Pelouze,  traces  of  lead,  243 

Perchlorate,  detection  of,  119 
determination  of,  128 
method  for  determining  potassium,  351 

Perchloric  acid,  determination  of,  128 

of  in  presence  of  hydrochloric  acid  and 
chloric  acid,  129 

Periodates,  determination  of,  208 

and  iodates,  determination  of  in  a  mixture, 
208 

Permanent   standards   for   ammonia   deter- 
mination in  water,  539 

Permanganate  N/io  reagent,"  219 
test  for  nitrite,  292 
titration  of,  antimony,  28 
barium,  59 
bismuth,  68 
calcium,  92,  549 
chromium,  137 
gold,  195 

iron,  17,  18,  218,  322,  490,  547,  651 
manganese,  228,  264,  266,  550 
molybdenum,  281,  282 
nitrous  oxides,  514,  520,  523 
phosphorus,  229,  317 
titanium,  437 
uranium,  461 
vanadium,  469-471,  475 
water  for  oxygen  consumed,  541 

Persulphate  of  ammonium  method  for  man- 
ganese, 267 

Persulphates,  ferrous  sulphate  method  for 

determining,  406 
oxalic  acid  method  for  determining,  406 

Petroleum  products   (see  under  Oils,  Fats, 
Waxes),  567 

Phenolphthalein  indicator,  12 
preparation  of,  12,  608 
uses  of,  499,  500 

Phenolsulphonic  acid  method  for  nitrates  in 

water,  539 
reagent,  539 

Phenylhydrazine  method  for  aluminum  in 
presence  of  iron  in  titaniferous  ores,  446 
acetate  test  for  gold,  193 

Phloroglucid  method  for  furfurol  in  acetic 
acid,  528 

Phosphate  baking  powder,  313 


SUBJECT   INDEX 


885 


Phosphate,  effect  on   alkaline  earth  deter- 
minations, 51 

Phosphate  rock,  decomposition  of,  312 
Phosphates  in  water,  548 
and  phosphoric  acid,  arsenic  in,  44 
typical  analyses  of,  311 
Phosphor-bronze,  analysis  of,  670 
Phosphoric  acid,  effect  on  aluminum  deter- 
mination, 8 
in  phosphate  rock,  320 

removal  of  from  aluminum  solutions,  6 
Phosphorus,  detection  of  hypophosphorous 

acid,  310 

meta  phosphoric  acid,  310 
ortho  phosphoric  acid,  310 
phosphorus  acid,  310 
pyro  phosphoric  acid,  310 
estimation,  methods  of  procedure,  general, 

3n 

gravimetric,  direct  precipitation  of  am- 
monium magnesium  phosphate,  315 
as  magnesium  pyrophosphate,  315 
as  phosphomolybdate,  314 
volumetric  methods,  alkali  titration  of 

phosphomolybdate,  316 
permanganate    titration    of    reduced 

phosphate,  317 

estimation,  special  methods,  determination 
of  in  iron  and  steel,  229 

in  manganese,  phosphorus,  bronze, 

670 

occurrence,  311 

preparation  of  the  sample,  iron  ores,  phos- 
phate rock,  minerals,  titanium-bearing 
ores,  iron  and  steel,  soluble  phosphates, 
baking  powder,  313 
separation   of  phosphorus  as   ammonium 

phosphomolybdate,  313 
Phosphorous  acid,  test  for,  310 
Phosphorous  method  for  det.  oxygen  in  gas, 

702 
pentoxide   absorption   bulb   for   moisture 

in  gases  (Fig.  134),  731 
Physical  tests  of  water,  534 

testing  of  cement,  642 
Pierce  method  for  selenium,  364 
Pig  iron,  arsenic  in,  33 
Pigments  of  paint  (see  under  Paint  and  Paint 

Pigments),  621 
Pipettes  for  gas  analysis,  693 
Pisani's  method  for  silver,  384 
Pitman  on  Du  Pont  nitrometer  (ref.),  306 
Pitot  tube  (Fig.  113),  690 
Plaster  of  Paris,  89 
Platinum,  detection,  general  characteristics 

of  element,  324 

tests    with    ammonium    chloride,    ferrous 
sulphate,  formic  acid,  hydrogen  sul- 
phide, metals,  oxalic  acid,  potassium 
chloride,  and  iodide,  etc.,  324 
estimation,  general  procedures: 
gravimetric  method,  by  electrolysis,  329 


Platinum,   estimation,  gravimetric  method: 
weighing  as  metallic  platinum,  328 
weighing  as  a  salt,  329 
occurrence,  325 
preparation  and  solution  of  the  sample, 

ores,  326 

platinum  scrap,  326 

small  amounts  of  platinum  in  presence 
of  large  amounts  of  iron,  magnesia, 
etc.,  326 

properties  of,  324 
separation  from  gold,  327 
from  indium,  327 
from  osmium,  328 
from  palladium,  327 
from  rhodium,  328 
from  ruthenium,  328 
solubility  of  the  element,  325 
special  methods,  platinum  ores,  329 

assay  methods  for  platinum  ores,  340 
substances  examined  for  platinum,  325 
Platinum  metal  group,  330 
Polymerization  in  analysis  of  turpentine,  617 
Polymerized  oils  and  resins,  separation  of,  619 
Portland  cement,  analysis  of,  650-653 
rapid  method  of  analysis,  653 
U.  S.  Gov.  specifications  for  fineness,  642 
Potassium,  detection  of,  341 
estimation,  general  procedures: 

gravimetric,  chlor-platinate  method,  349 

modified,  350 
indirect  method,  352 
Lindo- Gladding  method,  351 
perchlorate  method,  351 
special  methods,  alkali  determination  in 
silicates,  J.  Lawrence  Smith  method, 

lithium,    potassium    and    sodium    in 
presence  of  one  another,  355 

magnesium,  potassium  and  sodium  in 

presence  of,  352 
preparation  of  the  sample,  fertilizers,  soils, 

plant  ash,  saline  residues,  soluble  salts, 

rocks  and  insoluble  mineral  products, 

343,  344 
separation  from  the  hydrogen  sulphide  and 

ammonium  sulphide  groups,  344 
from  aluminum,  chromium,  iron,  barium, 
calcium,  strontium,  phosphoric  and 
sulphuric  acids,  etc.,  in  one  oper- 
ation, 346 

from  aluminum,  chromium,  iron,  tita- 
nium, uranium,  phosphoric  acid,  345 
from  barium,  calcium,  strontium,  345 
from  boric  acid,  346 
from  magnesium,  ammonium  phosphate 

method,  347 

barium  hydroxide  method,  346 
mercuric  oxide  method,  346 
from  sulphates,  345 
alkali  metals  from  one  another,  347 
potassium  from  sodium,  347 


886 


INDEX 


Potassium,  separation,  potassium  and  sodium 

from  lithium,  347 
potassium,  rubidium,  and  caesium  from 

lithium  and  sodium,  347 
Potassium  antimonyl  tartrate  standard  solu- 
tion, 29 

bromate  solution  N/io,  25 
method  for  antimony,  25 
bromide,  crude,  analysis  of,  82 
and  sodium  carbonates  and  hydrates,  in 
presence  of  one  another,  determina- 
tion of,  531 
acid  sulphate   (bisulphate),   fusion  with, 

212,  284 

fusion  of  monazite,  416 
carbonate,  fusion  with,  212 
chloride  test  for  platinum,  324 

test  for  iridium,  325 
cyanide  method  for  copper,  164 
dichromate  method  for  iron,  216 
ethyl  xanthate  method  for  small  amounts 

of  copper,  165 

ferricyanide  test  for  ferrous  iron,  210 
ferrocyanide  reagent,  480,  482,  484 

test  for  ferric  iron,  210 
fluoride  method  for  alumina  in  aluminum 

salts,  12 
reagent,  12 

hydroxide,  test  for  iron,  210 
test  for  rhodium,  336 
test  for  ruthenium,  334 
iodide  method  for  bismuth,  870 
for  chromium,  137 
for  copper,  163 
for  selenium,  364 
test  for  palladium,  332 
for  platinum,  324 
for  tellurium,  364 
nitrite  method  for  cobalt,  143 
standard  solution,  300 
test  for  cobalt,  140 
for  palladium,  333 
for  rhodium,  336 

permanganate.     See  Permanganate, 
method  for  phosphorus,  317 
N/io  solution,  317 

reagent  oxygen  consumed  in  water,  541 
pyrogallate,  det.  oxygen  with,  703 

reagent  for  gas  analysis,  735 
sodium  and  magnesium,  determination  of 

in  presence  of  one  another,  352 
sulphate,  estimation  of  potassium  as,  349 
sulphocyanate,  test  for  cobalt,  140 

for  iron,  210 
Praseodymium,  112,  113 

isolation  of,  115 

Precipitation  apparatus  for  sulphur  deter- 
mination (Fig.  61,  62),  397 
Preliminary  tests  for  alkaline  earths,  52 
Preparation  and  solution  of  the  sample.     See 

chapter  on  element  in  question. 
Preservatives  in  butter,  600 


Pringsheim's  method  for  halogens  in  organic 

matter,  122 

Prister's  method  for  gold,  197 
Producer  and  fuel  gases,  711 
Proof  gold,  preparation  of,  198 
Properties  of  compounds,  Part  III  table,  803 
of  elements  and  compounds.     See  chapter 

of  element  in  question. 
Prussian  blue,  638 
Pulp,  zinc,  moisture  in,  478 
Pumps,  suction,  688 
Pyrites  ores,  89,  150,  234,  258 
Pyrogallate  of  potassium,  reagent,  735 
Pyrophosphoric  acid,  test  for,  310 

Qualitative  tests,  tables  of,  825-855 
Quartering  coal  (Fig.  103),  673 

Radioactivity  of  thorium,  416 
Rammelsberg  method  for  determining  lith- 
ium, 354 
Rapeseed  oil,  595 
Rapid    methods    for    copper     (electrolytic 

determination),  157 
Rare  earths,  detection  of,  112 
estimation,  gravimetric,  115 
occurrence  of,  113 
preparation  of  the  sample,  114 
separation,  chart  for,  117 

from  iron,  aluminum,  thorium,  114 
from  other  elements,  115 
Rarer  elements  of  the  allied  platinum  metals, 

330 

Raschig's  method  for  sulphur,  405 
Rathke,  loss  of  selenium  (note),  360 
Reactions,  tables  of,  834-855 
Reagents: 

acid  mixture  for  silica  determination  in 

aluminum,  16 
alcohol  for  oil  analysis,  607 
alizarine  S  for  aluminum  determination,  14 
alkaline  potassium  permanganate  for  det. 

of  albuminoid  ammonia,  537 
tartrate  solution,  lead  det.,  244 
alpha-benzil-dioxime,  nickel  det.,  300 
ammonium  acetate,  lead  extraction,  242 
ammonium  chloride  solution  for  -det.  of 

ammonia  in  water,  536 
citrate  solution,  lead  det.,  244 
molybdate  solution,  vol.  det.  of  lead,  239 
det.  of  phosphorus,  313 

of  phosphorus  in  water,  548 
oxalate  solution,   oxygen  consumed  in 

water  analysis,  541 
persulphate  for  manganese  det.,  550 
sulphocyanate  sol.,  colorimetric  method 

for  iron,  222,  490 
amino-nitrosophenyl-hydroxylamine      sol. 

for  det.  iron,  214 
antimonyl    chloride,    standard    antimony 

solution,  25 
standard  solution,  41 


SUBJECT   INDEX 


887 


Reagents,  arsenite,  N/io  solution,  28,  204 
arsenous  acid  solution,  det.  manganese,  268 
Baudisch's  reagent  for  det.  iron,  214 
benzidine  hydrochloride  for  det.  sulphates, 

4p5,  55.1 
benzoic    acid    standard,    acidimetry    and 

alkalimetry,  504 

bismuth   standard   solution   for  det.   bis- 
muth, 69,  70 
bismuthate  of  sodium  for  det.  manganese, 

263 

bromine-potassium-bromide  sol.  for  oxidiz- 
ing sulphides,  396 
bromine,  607 
cadmium  chloride  sol.  evolution  method  for 

sulphur,  299 
calcium  chloride  sol.  for  det.  hardness  in 

water,  558 

carbon  dioxide,  preparation  of,  24 
caustic  standard  solution,  acidimetry  and 

alkalimetry,  504 
chlorine  water  standard  solution  for  det. 

bromine,  81 

chromic  acid  for  det.  SO-2  in  gas,  723 
citric  acid,  solution  for  calcium  det.,  90 
cinchonine  potassium  iodide,  colorimetric 

det.  of  bismuth,  69,  70 
color  solution  for  det.  traces  of  lead,  244 
color  solution  permanent  standard  for  det. 

nitrites  in  water,  439 
for  det.  fluorine,  184 
copper  standard  solution,  copper  analysis, 

163,  165,  166 
copper   sulphate   standard   solution,   det. 

hydrocyanic  acid,  no 
cupferron  reagent  for  det.  iron,  214 
cupric  potassium  chloride  for  separation 

of  carbon  from  steel,  95 
cuprous  chloride,  acid,  for  det.  CO  in  gas, 

724 

ammoniacal  for  det.  CO  in  gas,  734 
Devarda  alloy  for  reduction  of  nitrates,  300 
dichromate  of  potassium  N/io  and  N/5 

solutions  for  iron  det.,  216 
dimethylglyoxime  reagent  for  nickel  det., 

287 

diphenylcarbazide  for  chromium  det.,  132 
reducing  mixture  for   sulphates,  evolu- 
tion method,  400 
ferric  ammonium  sulphate,  for  titanium 

m  det,  438 

ferric  chloride  solution  for  det.  tin,  430 
chloride  solution  for  det.  tin,  430 
indicator  for  det.  chromates,  125 
for  Volhard's  method  for  silver,  378 
nitrate  solution  for  zinc  analysis,  482 
ferricyanide    of    potassium    indicator    for 

iron  titration   217 

ferrocyanide  of  potassium  standard  solu- 
tion, zinc  analysis,  480,  482,  484 
ferrous  ammonium  sulphate  for  iron  in 

water,  547 


Reagents,  ferrous  sulphate  for  nitric  acid 

test,  291 

N/io  sol.,  for  det.  barium,  59 
reagent  for  manganese  det.,  263 

for  det.  nitric  acid,  516 
fluorine,  standard  solution  for  fluorine  det., 

184 

fuming  sulphuric  acid,  734 
gas  analysis  reagents,  list  of,  734 
glacial  acetic  acid,  see  Oils,  Fats,  Waxes. 

Reagents,  607 
glycerol,  det.  boric  acid,  77 
hydrochloric  acid,  preparation  of  arsenic, 

free,  43 

for  oil  analysis  N/2,  608 
standard  solution,  504 
hydrogen  peroxide  for  titanium  det.,  440 
for  gas  analysis,  734 
for  water  analysis,  550 
iodate  N/io  solution  for  det.  iodine,  206 
iodide  sol.  for  det.  oxygen  in  water,  556 
iodine  N/io  reagent,  28 
for  oil  analysis,  608 
solution  for  det.  tin,  427 
iron  standard  solution  for  standardization 
of  stannous  chloride  reagent,  221, 

222 

for  col.  method  of  iron  in  spelter,  490, 

491 

iron  in  water,  547 
lead  acetate  for  molybdenum  det.,  278 

reagent  for  oil  analysis,  608 
acid  solution,  zinc  analysis,  490 
standard  solution  for  col.  det.  of  lead,  244 
magnesia  mixture  for  det.  of  phosphorus, 

3JS 

manganous  sulphate  solution  for  det.  dis- 
solved oxygen  in  water,  556 

mannitol,  boric  acid  det.,  77 

mercury  for  gas  burettes,  723,  735 

methyl  orange  indicator,  26,  301 
red  indicator,  301 

naphthylamine  acetate  solution  for  det. 
nitrites  in  water,  538  ^ 

Nessler's  solution,  ammonia  det.  in  water, 
536 

nitrate  standard  solution,  540 

nitric  acid,  pure,  125 

nitric  acid,  N/io  solution,  316 

nitrosulphonic    acid    for    elaidin   test  of 
oils,  608 

nitrous  acid  solution  for  decomposing  io- 
dides, 206 

oils,  fats,  and  waxes,  list  of  reagents  for 
examination  of,  607 

permanganate    solution    for    manganese 

det.,  263,  269 

N/io  solution  for  det.  of  iron,  219 
solution  for  det.  of  oxygen  consumed  in 
water,  541 

peroxide  solution  for  det.  titanium,  442 

phenolphthalein  indicator,  12,  608 


888 


INDEX 


Reagents,  phenolsulphonic  acid  for  det.  of 

nitrates  in  water,  539 
phosphate  standard  solution  for'phosphates 

in  water,  548 
potassium  antimonyl  tartrate  solution  for 

det.  antimony,  29 

bromate  N/io  solution  antimony  det.,  25 
chromate  indicator,  541 
cyanide  solution  for  copper  det.,  164 
dichromate  reagent  for  iron  det.,  216 
ethyl  xanthate  for  det.  copper,  165 
ferricyanide  indicator  for  iron  det.,  217 
ferrocyanide  for  det.  copper,  166 

for  zinc  det.,  482 
fluoride  for  free  acid  in  aluminum  salts, 

12 

hydrate  for  oil  analysis,  608 
iodide  for  det.  bismuth,  70 
nitrate  standard,  300 
permanganate  N/io  sol.,  317 
proof  gold,  preparation  of,  198 
pyrogallate  of  potassium  for  oxygen  det. 

in  gas,  735 
reducing  agents,  62,  128,  132,  149,  215, 

325,  358,  359 
salicylic  acid    reagent  for  traces  of  iron 

det.,  223 

salt  solution  for  chlorine  det.  in  water,  541 
silver  nitrate,  N/io  solution,  125,  126 

solution  for  det.  chlorine  in  water,  541 
preparation  of  the  pure  metal,  384 

standard  solution,  378 
soap  standard  solution  for  det.  hardness 

in  water,  558 

sodium  arsenite.  See  Arsenous  Acid, 
bismuthate  for  det.  manganese,  263 
carbonate  standard  solution  for  CO2  det. 

in  water,  553 

preparation  of  pure  salt,  501 
hydroxide,  N/io  solution,  316 

for  Devarda  method,  301 
or  potassium  hydroxide  reagents,  water 

analysis,  540 
metabisulphite,  method  of   production, 

247 

nitrite  solution,  nitrite  det.  in  water,  538 
hydroxide,  det.  nitrates  in  water,  540 
thiosulphate  N/ioo  solution,  water  an- 
alysis, 556 

for  pot.  iodide  method  for  copper,  163 
N/io  solution,  204,  608,  635 
stannous  chloride  solution  for  det.  ferric 

iron,  217,  221 

starch  solution,  205,  399,  556,  608,  635 
sulphanilic  acid  solution  for  det.  nitrites  in 

water,  538 
sulphocyanate  for  colorimetric  det.  of  iron, 

222,  490 
sulphuric  acid  standard  solution,  502 

for  ammonia  det.,  300 
tartrate,    alkaline    solution    of,    for    det. 
traces  of  lead,  244 


Reagents,     tannin     indicator,     Alexander's 

molybdate  method  for  lead,  239 
thiocyanate  of  ammonium  or  potassium 

N/io  solution,  125 
thiosulphate  of  sodium  for  det.  of  copper, 

163 

N/io  solution,  204 
tin,  standard  solution  of,  427 
titanium,  standard  solution  of,  for  fluorine 

det.,  184 

for  titanium  det.,  440,  442 
thymol  solution  for  titanium  det.,  445 
Wagner's  solution,  calcium  det.,  90 
Red  lead  method  for  manganese,  268 
Reduction  of  iron  compounds,  method  for,2i5 
Redwood,  viscosity  of  oils  (note),  573 
Refractive  index,  animal  and  vegetable  oils, 

581 

Chinese  wood  oil,  613 
turpentine,  617 
Refractory     materials,     decomposition     for 

chromium  determination,  133 
Reich  method  for  SO2  in  gas,  apparatus  for 

(Fig.  130),  721 

Renard's  test  for  peanut  oil,  594 
Residue,  total  solid,  in  water,  542 
Resinates  in  paint  vehicles,  611 
Resins  and  polymerized  oils,  separation  of, 

619 
Rhodium,  detection  of,  336 

estimation,  gravimetric  methods,  337 
preparation  of  the  sample,  336 
properties  of,  336 
separation  from  platinum,  336 

from  iridium  and  ruthenium,  337 
Richard's  jet  pump  (Fig.  109),  688 
Rickett's  overflow  pipette,  380 
Riehle   automatic   cement-testing   machine, 

(Fig.  101),  648 

Riffle,  sampling  of  copper,  159 
Roark  and  McDonnell,  arsenic  separation,  33 
Robert's  analysis  for  copper  and  lead,  175 
Robin's  test  for  boron,  77 
Roscoe's  lead  acetate  method  for  vanadium, 

468 

Rose's  method  for  determining  bismuth,  68 
mercurous  nitrate  method  for  vanadium, 

467 

metal,  analysis  of  (see  Alloys),  663 
selenium  loss  by  heat,  360 
Rosenbladt  and  Gooch,  method  for  boron,  74 
Rosendale  cement,  analysis  of,  658 
Rosin   oil    (see    subject    under   Oils,    Fats, 

Waxes),  595 

Rotameter  (Fig.  114),  691 
Rowell's  method  for  antimony,  25 
Rubber  goods,  antimony  in,  21 
Rubidium,  detection  of,  342 
preparation  of  the  sample,  344 
separations,  .347 

Rudorff's  apparatus  for  carbon  dioxide  in 
gas  (Fig.  128),  719 


SUBJECT   INDEX 


889 


RudorfPs  method  for  carbon  dioxide  in  gas, 

718 
Ruthenium,  detection  of,  334 

estimation,  gravimetric  methods,  335 
preparation  of  the  sample,  334 
properties  of,  336 

separation  from  platinum,   iridium,   and 
rhodium,  335 

Salas,  tin  presence  of  in  silver  determination, 

382 
Salicylic  acid  method  for  small  amounts  of 

iron,  223 
test  for  iron,  210 
Saline   residues,    preparation   of,   for   alkali 

det,  344 

Salt,  standard  solution  of,  541 
Sampling  apparatus  for  gas,  see  chapter  on 

Gas,  687 
Sand,  analysis  of,  374 

silica  in,  374 
Sanger,    method    for    traces    of    antimony, 

modified,  28 

Sanitary  analysis  of  water,  534 
Saponification  number  in  analysis  of  oil,  587, 

613 
Savell,  chapter  on  cobalt,  140 

on  nickel,  283 
Saybolt  viscosimeter,  573 
Saybolt  to  Engler  times  conversion  table,  607 

to  Redwood  times  conversion  table,  607 
Scale  in  water,  563 
Scandium,  112,  113 
Schaeffer  and  Gardner  chapter  on  Analysis 

of  Paints,  609 
Scheibler    and    Dietrich    determination    of, 

carbon  (reference),  107 
Schmatolla  titration  of  aluminum  salts  (ref .), 

n 
Schmitz,   method   for  antimony  in  rubber 

goods,  21 

for  magnesium  determination,  255 
Schroetter's  alkalimeter,  106 
Scott,  apparatus,  hydrogen  sulphide  genera- 
tor, 38 

evolution,   for  sulphur  determina- 
tion in  steel,  399 
(and  Briggs),  modified  Orsat  for  SC>2 

gas  determination,  723 
chapters  by.     See  Table  of  Contents, 

ix-xxviii. 
methods,  fluoride  method  for  free  acid 

in  aluminum  salts,  12 
lead,  determination  of  traces  by  ace- 
tate extraction,  241 
(and    Bowman),    nitric    acid,    deter- 
mination of,  with  ferrous  sul- 
phate, 515 
sulphur,  combustion  method  for,  402 

modified  evolution  method,  398 
Seamen's  volumetric  method  for  determin- 
ing mercury,  274 


Seeker- Clay  ton  method,  modified,  for  det. 

traces  of  lead,  243 
Selenium,  detection  of,  358 
estimation,  gravimetric  methods: 
reduction  with  potassium  iodide,  364 
by  reduction  with  SO2,  362 
volumetric  method,  365 
occurrence,  359 

preparation  and  solution  of  the  sample,  360 
separation  of  selenium  and  tellurium  from 
iron,  zinc  and  other  members  of  the 
group,  and  from  the  alkalies  and  al- 
kaline earths,  360 
from  copper,  cadmium,  bismuth,  silver, 

and  gold,  361 
from  tellurium  by  Keller's  method  and 

by  distillation  method,  361 
and  tellurium,  determination  of  in  copper, 

170,  171 

apparatus  for  separating  (Fig.  57),  362 
solubilities,  360 
Semi-drying  oils,  list  of,  602 
Separations.     See  under  name  of  element  to 

be  isolated. 
Separatory  funnel  and  graduate  (Fig.  130), 

692 

Sesame  oil  (see  under  Oils,  Fats,  Waxes),  595 
Setting  time  for  cement,  645 
Shields'  formula,  711 

Shimer's   combustion   apparatus  for  deter- 
mining carbon,  100 
Shimer  method  of  analysis  of  cement  rocks, 

658 

Silica  in  iron  and  steel,  371 
in  hydrochloric  acid,  510 
in  paint  pigments,  631 
in  Portland  cement,  650 
in  sand,  374 
in  sodium  fluoride,  188 
in  titaniferous  ores,  446 
in  ultramarine  blue,  637 
in  water,  546 

removal  of,  in  sulphur  determination,  395 
Silicates,    alkalies   in,    J.    Lawrence    Smith 

method,  355 

decomposition  of  for  fluorine  determina- 
tion, 178 

of  for  iron  determination,  212 
list  of,  acid-soluble  and  acid-insoluble,  369 
materials  high  in,  decomposition  for  chro- 
mium determination,  133 
Silicate  of  soda,  analysis  of,  373 
Silicon,  detection  of,  367 
errors,  causes  of,  368 
estimation,     method     of     determination, 

general  procedure,  372 
special  procedures: 

determination  in  metallic  aluminum, 

16 
combined  silicon  in  iron  and  steel, 

231,  232 
graphitic  silicon  in  aluminum,  17 


890 


INDEX 


Silicon,  occurrence,  367 
preparation  and  solution  of  the  sample, 

general  considerations,  368 
decomposition  of  silicates  with  acids,  369 
fusion  methods  for  silicates  not  decom- 
posed by  acids,  370 

methods  for  decomposition  of  carbide 
and  carborundum,  ferro-silicon,  iron 
and    steel    for    silicon,    slags    and 
roasted  ores,  sulphides  and  pyrites, 
chromium,  molybdenum  and  tung- 
sten steels,  371 
Silver,  detection  of,  375 
estimation,  general  procedures: 
gravimetric,  by  electrolytic  deposition, 

377 

as  silver  chloride,  376 
as  silver  cyanide,  377 
volumetric,  combination  methods: 
Denige"'s  cyanide  method,  383 
Gay-Lussac  method,  379 
miscellaneous  methods,  384 
nephelometric  method,  384 
Volhard's  method  with  thiocyanate, 

378 
special  procedure  for  determining  silver 

in  lead,  248 
occurrence,  376 
preparation  of  pure  silver,  384 
solubility,  376 

Silver  arsenate,  determining  of  in  arsenic,  40 
bromide,  precipitation  of,  80 
chloride,  precipitation  of,  124 
cyanide,  determination  of  silver  as,  377 
chrpmate  method  for  chlorine,  126 
iodide  method  for  iodine,  203 
nitrate  detection  of  bromine,  78 
method  for  chlorine,  1 24 

for  strontium,  390 
standard  solution  of,  541 
N/io  solution,  125,  126 
volumetric  method  for  alkalies,  357 
paper  for  traces  of  antimony,  29 
test  for  chlorine,  118 
thiocyanate  method  for  bromine,  81 

-ferric  alum  method  for  chlorine,  125 
Simpson's  process  for  opening  up  titaniferous 

minerals,  456 
Slag  (matte),  decomposition  of  for  copper 

determination,  151 
and  silicious  ores,  decomposition  of  for 

fluorine  determination,  178 
decomposition   of    for   manganese   deter- 
mination^ 258 
v    decomposition  of  for  silica  determination, 

37i 

Sling  psychrometer,  728 
Slow  method  for  copper  (electrolytic  det), 

158 

Smith,  E.  F.,  electro  analysis  of  platinum,  329 
Smoke  in  chimney  gases,  711 
Snake  weighing  tube,  507 


Soap,  detection  of  in  lubricating  oil,  578 
Soda,  value  for  in  water  analysis,  560 
Sodium,  detection  of,  341 

estimation,  general  procedures: 
difference  method,  349 
indirect  method.  352 
sodium  chloride,  determination  as,  349 

sulphate,  determination  of,  348 
potassium  and  lithium  in  presence  of  one 

another,  determination  of,  355 
potassium  and  magnesium,  in  presence 
of  one  another,  determination  of, 
352 
estimation,  special  procedures: 

sodium  and  potassium  in  water,  551 
preparation  and  solution  of  the  sample,  343 
separation   from   potassium,   lithium,    ru- 
bidium and  caesium,  344 
Sodium  carbonate,  fusion  test  of  silicates,  367 
fusion  with,  212 
in  sodium  fluoride,  187 
or  bicarbonate,  fusion  of  silicates,  370 
determination  in  presence  of  acids  of 

sulphur,  413 

preparation  of  the  pure  salt,  501 
chloride,  arsenic  in,  45 

effect  of  in  silica  determination,  372 

estimation  of  sodium  as,  348 

det.  of  in  presence  of  sulphur  acid  salts, 

4i3 

in  silicate  of  soda,  374 

fluoride,  analysis  of,  187 

in  sodium  fluoride,  188 

in  sodium  nitrate,  303 

hydroxide  fusion  of  ores,  20 

of  tin  ores,  421 
test  for  platinum,  325 
N/io    reagent   for    phosphorus    deter- 
mination, 316 

metabisulphite,  alkali  titration  of,  41 1 
determination  in  presence  of  carbonates, 
chlorides,  sulphates,  sulphites,  thio- 
sulphates,  413 

nitrite  standard  solution,  538 
oxide,  determination  in  silicate  of  soda,  373 

in  ultramarine  blue,  637 
peroxide  fusion  for  chrome  iron  ores,  133 
method  for  halogens  in  organic  matter, 

122 
peroxide    method    for    decomposition    of 

organic  matter,  122 
fusion  of  tin  ores,  421 
test  for  iron,  210 
potassium  and  the  other  alkalies,  chapter 

on,  341 

and  potassium  in  water,  551 
pyroantimonate,  test  of  sodium  as,  341 
pyrogallate,  oxygen  det.  with  (note),  702 
sulphate,  estimation  of  sodium  as,  348 
in  sodium  fluoride,  187 
in  sodium  nitrate,  303 
test  for  strontium,  387 


SUBJECT   INDEX 


891 


Sodium  sulphide,  available  H2S  in,  407 
sulphite,  acid  titration  of,  412 

determination   of   in   presence   of   car- 
bonates, chlorides,  metabisulphites, 
sulphates  and  thiosulphates,  412 
thiosulphate,  detection  of  aluminum  with, 

determination  of  aluminum  with,  9 
determination   of,   in  presence   of   car- 
bonates, chlorides,  metabisulphites, 
sulphates  and  sulphites,  412 
standard  solution  for  copper  determina- 
tion, 163 

N/io  solution  of,  204,  634 
test  for  molybdenum,  275 
Softening  of  water,  563 
Soils,  nitrogen  in,  304 
Solder,  antimony  in,  25 
Solenoid  apparatus,  electrolysis  of  copper,  157 
method  of  Heath  for  det.  copper,  157 
soft,  analysis  of  arsenic,  iron,  lead,  tin  and 

zinc,  66 1,  663 

Solids,  metals  in  acetic  acid,  529 
non-volatile  in  nitric  acid,  515 
Solubilities,  elements,  their  oxides  and  salts, 
given  under  Estimation.     See  chapters. 
Soluble  salts  in'lithopone,  631 
Soundness  or  constancy  of  volume  of  cement, 

646 

Specific  gravity  chart  for  sulphuric  acid,  502 
of  cement,  643 
of  gas,  718 
of  oils: 

animal  and  vegetable,  oils,  580 
burning  oils,  569 
Chinese  wood  oil,  613 
lubricating  oil,  569,  575 
turpentine,  617 
Specifications  for  elements  in  steel,  carbon, 

225 

manganese,  228 
phosphorus,  229 
silicon,  232 
sulphur,  231 

Spectroscopic  method  for  determining  lithi- 
um, 353 

detection  of  rare  earths,  112 
Spectrum,   detection   of  barium  by  means 

of,  50 

of  cadmium,  84 
of  caesium,  342 
of  calcium,  88 
of  lithium,  342 
of  potassium,  342 
of  rubidium,  342 
of  sodium,  341 
of  strontium,  387 
of  thallium,  416 
of  zirconium,  494 
Speisses,  decomposition  of,  20 
Spelter,    impurities,  determination    of   cad- 
mium, iron,  lead,  489,   492 


Spent  oxide,  evaluation  of,  414 
Spiegel  iron,  manganese  determination  in,  268 
Spontaneous  combustion  test  of  oils,  596 
Stains,  standard  stains  for  arsenic,  41 
Standard  reagents.     See  Reagents. 
Standards  for  Chinese  wood  oil,  615 
linseed  oil,  616 
turpentine,  618 
Stannic  acid  method  for  tin  in  bichloride  by 

hot  water  precipitation,  421 
Stannous    chloride,    action    on    hydrochlor- 

platinic  acid,  325 
apparatus  (Fig.  41),  221 
method  for  iron,  221 
reduction  of  ferric  solution,  217 
test  for  mercury,  270 

Starch  solution,  preparation  of,  205,  399,  556 
Stas  overflow  pipette,  380 
Stead's  method  for  separation  of  arsenic,  33 
Steel,  elements  det.  in.     See  Iron  and  Steel 

Analysis. 

Steels  with  chromium,  molybdenum,  tung- 
sten and  vanadium,  decomposition  of 
for  silica  det.,  371 

Steiger's  method  for  determining  fluorine,  183 
Stolba,  Franz,  volumetric  method  for  cerium, 

116 
Stromayer  and  Rose,  separation  of  barium 

from  calcium  and  strontium,  54 
Strontium,  detection  of,  general  procedure, 
flame  test,  sodium  sulphate  test,  spec- 
trum, 387 

estimation,  general  procedures: 
gravimeric,  as  carbonate,  389 
as  oxide,  389 
as  sulphate,  389 

volumetric,  alkalimetric  method,  389 
chloride  titration  with  AgNOs,  390 
occurrence,  ores  and  minerals,  387 
preparation  and  solution  of  the  sample,  388 
separation  from  alkalies  and  magnesium, 

388 

from  barium,  388 
from  calcium,  55,  388 
solubilities,  388 
Subcarbonate   of  bismuth,   precipitation  of 

bismuth  as,  66 

Suction  ventilator  (Fig.  103),  673 
Sulphanilic  acid  reagent,  538 
Sulphate  method  for  determining  lead,  236 
Sulphate    method    for    separating    alkaline 
earths  from  the  alkalies  and  magnesium, 

for  determining  lead,  236 
Sulphates  in  gypsum,  632 
soluble  in  blanc  fixe,  633 
in  sublimed  white  lead,  624 
in  water,  551 
Sulphates  and  sulphides  in  presence  of  one 

another,  determination  of,  409 
determination   of,    in   presence   of   other 
sulphur  acids,  412 


892 


INDEX 


Sulphide,  detection  of,  391 
determination  of  tin  as,  423,  426 
in  composite  white  paint,  634 
ores,  evaluation  of  by  combustion  method, 

402 

solubility,  393 
Sulphide  and  sulphate  det.  on  in  presence  of 

each  other,  409 
Sulphide  and  sulphohydrate  in  presence  of 

one  another,  determination  of,  408 
Sulphide  ores,  decomposition  of,  19,  31,  51, 

89,  150,  211,  234,  393,  258,  371,  396 
Sulphites,  iodine  titration  of,  410 
detection  of,  391 

in  presence  of  other  sulphur  acids,   de- 
termination of,  412 
solubility,  393 

sulphurous  acid  test  for  vanadium,  463 
Sulphocyanate  method  for  determining  cop- 
per, 162 

for  small  amounts  of  iron,  222 
Sulphocyanic  acid,  sulphur  in,  409 
Sulphohydrate  in  presence  of  sulphide,  det. 

of,  408 
Sulphur,  detection  of,  element,  391 

sulphides,    sulphites,    sulphates,    thio- 

sulphates,  391 

estimation,  general  procedures: 
gravimetric,  as  barium  sulphate  precip- 
itated from  hot  solutions,  395 
as  barium  sulphate  precipitated  from 
cold  solutions,  large  volume,  396 
combustion  method  for  sulphide  ores, 

402 
gravimetric  and  volumetric,   evolution 

method,  398 
evolution  method  for  S  in  iron  and 

steel,  400 

iron  ore  briquettes,  sodium  sul- 
phide, 401 

volumetric  methods,  titration  with  ba- 
rium chloride,   and  potassium  di- 
chromate  (Wiedenstein's  method), 
403 
barium   chromate-iodine-thiosulphate 

method  of  Hineman,  404 
benzidine  hydrochloride  method,  405 
estimation,  special  procedures: 
available,  in  brimstone,  415 
determination  of  sulphur  in  coal,  393, 675 
free  sulphur  in  a  mixture,  414 
in  copper,  172 
in  gas,  716 
in  iron  and  steel,  229 
in  materials  high  in  sulphide  sulphur, 

determining  available  H2S,  407 
in  oils,  burning  oils,  570 
in  rocks,  silicates,  insoluble  sulphates, 

393 

in  Portland  cement,  652 
in  sublimed  blue  lead,  638 
in  thiocyanic  acid  and  its  salts,  409 


Sulphur,  in  ultramarine  blue,  637 
volatile,  in  coal,  675 
in  spent  oxide,  415 
residual,  in  spent  oxide,  415 
Sulphur  dioxide  test  for  molybdenum,  275 
in  zinc  lead  and  leaded  zinc,  626 
method  for  determining  selenium,  363 

tellurium,  364 

reduction  of  vanadium  to  VzO*,  469 
test  for  titanium,  432 
Sulphuric  acid,  arsenic  determination  in,  81, 

44 
arsenous  acid  in,  31 

combined,  in  silicate  of  soda,  374 
gases,  720  ^ 

Sulphuric  acid  in  aluminum  salts,  12 
in  ammoniacal  liquor,  299 
in  acetic  acid,  527 
in  hydrochloric  acid,  509 
in  hydrofluoric  acid,  511 
in  nitric  acid,  513 
in  oleum  and  mixed  acids,  523 
(anhydride)  in  oleum  and  mixed  acids, 

523 
in  paint  pigments,  624,  628,  632,  633, 

634,  638,  639,  640 
in    standard    solution,    preparation    of, 

502,  503 

for  Devarda^s  alloy,  300 
strength   for   equilibrium   with   atmos- 
pheric moisture,  502 
test  for  selenium,  358 
test  for  oils,  571 

Sulphurous  acid,  free  or  combined,  in  sul- 
phites, acid  sulphites,  metabisulphites, 
and  thiosulphates,  determination  of, 
gravimetric,  409 

free  or  combined  in  sulphites,  acid  sul- 
phites, metabisulphites  and  thio- 
sulphates, volumetric  method  with 
iodine,  410 

free  or  combined  in  sulphites,  acid  sul- 
phites, metabisulphates,  and   thio- 
sulphates,  acidimetric   and   alkali- 
metric  methods,  411 
in  acetic  acid,  529 
in  hydrofluoric  acid,  511 
reduction  of  ferric  solution,  216 

of  chlorate,  128 

Sutton,  permanganate  titration  of  calcium 
oxalate,  92 

Tables,  Acids: 

acetic  acid  (Oudemans')  Table  XII,  795 
melting-points  of  (Rudorff)  Table 

XIII,  796 
hydrochloric  acid  (Ferguson),  Table  V, 

782,  783 

(Lunge  and  Marchlewski),  784 
constant  boiling-points  of,  784 
nitric  acid  (Ferguson),  Table  VII,  785, 
786 


SUBJECT   INDEX 


893 


Tables,  nitric  acid  (Lunge  and  Rey),  Table 

VIII,  787,  788 
phosphoric    acid    (Hager),    Table    IX, 

789 
sulphuric  acid   (Ferguson  and  Talbot) 

Table  X,  790-793 
(Bishop),  Table  XI,  794 
approximate  boiling-points,  791 
fuming,  795 

charts  of  sp.gr.  and  b.p.,  502 
alkalies: 

aqua  ammonia  (Ferguson),  Table  XIV, 

797 

coefficient  of  expansion,  797 
sodium  hydroxide  (Lunge),  Table  XV, 

798 

atomic  weights,  international,  Table  I,  779 
Baume  degrees  and  specific  gravity  com- 
parison, Table  XX,  819 
Centigrade  and  Fahrenheit  degrees,  com- 
parison, Table  XIX,  818 
compounds,  inorganic,  useful  data  (Meikle- 

john),  Table  XVII,  801-803 
conversion     factors    (Scott    and    Clark), 

Table  XVIII,  804-817 
electromotive    arrangement    of    elements, 

Table  IV,  781 

Engler,  Redwood,  and  Saybolt  times,  com- 
parison table,  607 
fatty  acids,  characteristics  of,  603 
fluorine   chart,    apparent   per   cent   TiO2 

and  grams  F.,  185 
gases,  aqueous  vapor  in  air,  736 

chimney  or  flue,  table  of  calculation,  710 

detection  of,  property  tables,  694 

efficiency  and  loss  chart,  738 

specific  heat  of,  736 

sulphur  dioxide,  iodine  values  for,  in 

Reich  method,  721,  722 
table  of  constants,  822,  823 
hardness  in  water,  559 
indicators  and  their  uses,  499 

Thomson's  table,  500 
melting-points  of  the  elements,  Table  II, 

780 

oil,  characteristics  of,  604 
permanent  standards,  ammonia  in  water, 

538 
rare  earth  elements,  112 

oxalates,  separations,  117 
specifications  for  elements  in  steel: 
carbon  in  steel,  225 
manganese  in  steel,  228 
phosphorus  in  steel,  229 
silicon  in  steel,  232 
sulphur  in  steel,  231 
temperature,  standards  of  measurement, 

780 

from  color  of  heated  metal,  781 
of  flames,  780 
constants,  781 
turbidimeter  sulphur  table,  676,  677 


Tables,  vapor  tension  of  water  in  mm.  Hg  at 

—  2  to  36°  C.  (Regnault,  Broch  and 

Weibe),  Table  XVI,  800 

water,  outline  of  procedure  for  analysis,  545 

standards  of  purity  table  of  Illinois  State 

Geological  Survey,  544 
waxes,  characteristics  of,  606 
weights    and    measures,    comparison    of 
metric  with  customary    units,  Table 
XXI,  820 
Talbot's    method    for    separating    tungsten 

from  tin  and  antimony,  452 
Tantaliferous  minerals,  455 

opening  up  of,  456 
Tantalum,  detection  of,  455 

estimation,  method  for  determining,  557 
occurrence,  ores  and  minerals,  455 
preparation  and  solution  of  the  sample,  456 

tantaliferous  minerals,  456 
separation,  isolation  of  tantalum  oxide,  456 
removal  of  antimony  and  tin,  tungsten 

and  silica,  457 
solubilities,  456 

Tartaric  acid,  oxidation  of,  in  titanium  de- 
termination, 436 
Tellurium,  detection,  general  procedure,  358 

special  tests,  359 
estimation,  363 

gravimetric,   determination  as  dioxide, 

265 

reduction  with  sulphur  dioxide,  364 
volumetric  method,  365 
occurrence,  359 

preparation  and  solution  of  the  sample,  360 
separations  (see  Selenium),  360 
solubilities,  360 
and  selenium,  determination  of,  in  copper, 

171 
apparatus  for    separation  of  (Fig.  57), 

362 
Tellurium  dioxide,  determining  tellurium  as, 

365 
Temperature  determination  of  flue  gas,  709 

estimation  of  by  color  of  heated  metal,  781 
Temperatures  of  flames,  780 
Tensile  strength  of  cement,  test,  for,  647 
Terminal  case  (Fig.  27),  electrolytic  deter- 
mination of  copper,  155 
Test  lead  method  for  reducing  ferric  salts, 

215,  217 

Thallium  protoxide  test  for  platinum,  325 
Thiocyanate  method  for  determining  iron, 

222 

(Volhard)  for  silver,  378 
Thiocyanic  acid,  sulphur  in,  409 
Thiosulphate  in  presence  of  sulphide  and 

sulphohydrate,  det.  of,  408 
Thiosulphate  of  sodium,  N/io  solution  of,  204 
determination  of  in  presence  of  sulphide 

and  sulphohydrate,  408 
Thiosulphates,  detection  of,  391 
gravimetric  method  for,  409 


894 


INDEX 


Thiosulphates,  reagent  for  iodine  number  in 

oils,  584 
solubility,  393 

volumetric  iodine  method  for,  410 
Thomas  electric  gas  meter,  691 
Thomson,  boric  acid  in  milk,  73 

method  for  iron,  222 
Thomson's  table  of  indicators,  500 
Thorite,  decomposition  of,  416 
Thorium,  detection  of,  416 

estimation,  gravimetric  method,  417 

minute  amounts  of,  418 
preparation  and  solution  of  the  sample, 
oxides,   phosphates   (monazite,  etc.), 
silicates,  416 
separations,  417 

Thresh's  method  for  bismuth,  70 
Thymol  method  for  titanium,  444 
Tin,  detection  of,  419 

estimation,  general  procedures: 
gravimetric,  by  electrolytic  method,  430 
by  hydrolysis  and  ignition  to  oxide, 

422^ 

as  sulphide,  422 
volumetric,  iodine  method  of  Lenssen, 

modified  by  Baker,  426 
estimations,  special  procedures: 
determination  of  in  alloys,  brass  and 

bronze,  667 

in  Britannia  metal,  667 
in  metallic  lead,  250 
in  soft  solder,  662 
in  type  metal,  660 
in  Wood's  metal,  664 
determination  in  bichloride  of  tin,  421 
in  canned  food  products,  430 
in  water,  557 
preparation  of  the  sample,  opening  up  tin 

ores,  419 

cyanide  process,  420 
hydrogen  reduction,  421 
sodium  carbonate  methods,  421 
hydroxide  method,  421 
peroxide  method,  421 
separation,  general  procedure,  421 
from  aluminum,  antimony,  422 

in  water,  557 

from  antimony  in  alloys,  660,  667 
from  arsenic,  35 
from  arsenic  in  alloys,  667 
from  copper,  lead,  421 
from  phosphorus,  tungstic  acid,  442 
standard  solution  of,  427 
Time  required  in  gas  analysis,  707 
Titaniferous  ores,  analysis  of,  determination 
of    titanium,    aluminum,    iron,    silica, 
phosphorus,  445,  447 
slags,  decomposition  of,  434 
Titanium   Alloy   Manufacturing   Company, 

methods  of,  436,  441-444,  445 
Titanium,  detection  of,  432 
estimation,  general  procedures: 


Titanium,  estimation,  gravimetric,    Gooch- 

Thornton  method,  modified,  435 
ferro-carbon  titanium,  436 
volumetric,  by  reduction  and  direct  ti- 

tration  with  ferric  salt,  438 
by  zinc  reduction,  addition  of  excess 
ferric  salt  and  titration  with  per- 
manganate, 437 
hydrogen  peroxide  colorimetric  meth- 

.  od,  439 
estimation,  special  procedures: 

titanium  in  steel,  colorimetric  method, 

441 

in  steel  treated  with  ferro-carbon,  441 
hydrochloric  acid-insoluble  titanium,  443 

-soluble  titanium,  442 
occurrence,  ores  and  minerals,  432 
preparation  and  solution  of  the  sample, 
alloys,    element,    ores,    oxides,    salts, 
steel,  titaniferous  slags,  433-434 
separation  from  alkaline  earths,  434 
from  aluminum,  iron,  copper,  434,  435 
from    bivalent    metals,    cobalt,    nickel, 

manganese,  zinc,  435 
Titer  test  for  oils,  598 

standard  solution  of,  445 
Titration  of  acids  and  alkalies,  508 
Traces.     See  under  estimation  of  element 

in  question, 
aluminum,  detection  of  with  alizarine  S, 

14 

determination  of  with  alizarine  S,  14 
ammonia,  299,  536 
antimony,  detection  of,  18 

determination  of,  28 
arsenic,  detection  of,  30 

determination  of  in  acids,  sulphuric, 
hydrochloric,  nitric,  phosphoric,  in 
alumina  and  iron  ores,  phosphates, 
salts,  baking  powder,  canned  goods, 
meat,  etc.,  40-46 
barium,  detection  by  flame  and  spectrum, 

50 

beryllium.     See  Glucinum. 
bismuth,  colorimetric  procedures  for  esti- 
mation of,  69,  70 
boron,  tests  for,  71 
cadmium,  detection  by  spectrum,  84 
calcium,  detection  by  flame  and  spectrum, 

88 

carbon,  colorimetric  estimation  of,  108 
cerium,  and  the  other  rare  earths,  detec- 
tion, 112 

colorimetric  method  for  cerium,  116 
chlorine,  detection  of,  118 
chromium,  detection  of,  132 

determination  of,  138 
cobalt,  detection,  140 
determination  by  nitroso-beta-naphthol, 

143 

columbium.     See  Tantalum, 
copper,  detection,  149 


SUBJECT   INDEX 


895 


Traces,    copper,     determination    in    small 

amounts,  165-167 
in  water,  557 
fluorine,  detection  of,  176,  177 

estimation  of,  188 
glucinum,  detection  of,  189 
gold,  detection  of,  192 

determination  of  small  amounts,  196 
iodine,  detection,  200 
iron,  detection  of,  210 

determination  of  small  amounts,  222 
lead,  detection  of,  233,  557 
determination   of   small   amounts,   gravi- 
metric, 241 
colorimetric,  243 
lithium,  detection  of,  342 
magnesium,  detection  of,  253 
manganese,  detection  of,  257 

determination  of  small  amounts,  267 
mercury,  detection  of,  270 
molybdenum,  detection  of,  275 
nickel,  detection  of,  283 

determination  of  small  amounts,  286,  287 
nitrogen,  ammonia,  Nessler's  test  for,  291 
determination.      See    Ammonia    under 

Traces, 
nitric  acid,  detection,  291 

determination  of  small  amounts,  515 
nitrous  acid,  test  for,  291 

estimation  of,  520 
phosphorus,  detection  of,  310 
platinum,  detection  of,  324 
platinum  metals,  detection  of  iridium,  330 
osmium,  327 
palladium,  332 
rhodium,  336 
ruthenium,  334 
potassium,  detection  of,  341 
rubidium,  detection  of,  342 
selenium,  detection  of,  358 
sodium,  detection  of,  341 
tellurium,  detection  of,  359 
silicon,  detection  of,  367 
silver,  detection  of,  375 

determination  of  small  amounts,  384 
strontium,  detection  of,  387 
sulphur,  combined  and  free,  detection  of, 

3Qi 

determination  of  small  amounts,  evo 

lution  method,  398 
thorium,  detection  of,  416 

determination  of  minute  amounts,  418 
tin,  detection  of,  419,  557 

determination  of,  in  canned  food  prod- 
ucts, 430 

tantalum  and  columbium,  detection  of,  455 
titanium,  detection  of,  432 

colorimetric  method,  439,  441,  444 
tungsten,  detection  of,  448 
uranium,  detection  of,  458 
vanadium,  detection  of,  463 

determination  of  small  amounts,  471, 475 


Traces,  zinc,  detection  of,  477,  557 

determination  of  small  amounts,  487 
zirconium,  detection,  494 
Tread  well  and  Hall,  205,  206 

method  for  iodine,  206 
Trisulphide  of  antimony,  determination  of 

antimony  as,  23 

arsenic,  determination  of  arsenic  as,  36 
Trogg   and    Lenher,    precautions    on    silica 

determination,  373 
True  silica,  estimation  of,  372 
Tung  oil,  analysis  of,  613 
Tungsten,  detection  of  in  alloys  and  steel, 

448 

in  minerals,  448 
estimation,  gravimetric: 

mercurous  tungstate  method,  454 
tungstic  acid,  precipitation  of,  453 
volumetric  method,  454 
estimation,  special  procedures: 

tungsten  bronzes,  451 
occurrence,  ores  and  minerals,  449 
powder,  typical  analysis  of,  449 
preparation  and  solution  of  the  sample,  449 
alloys,    steel    minerals,    ferrotungsten, 

tungsten  bronzes,  449-451 
separation  from  antimony,  tin,  452 
from  arsenic  and  phosphorus,  452 
from  iron,  titanium,  vanadium,  452,  453 
from  molybdenum  by  HommelPs  and 

Pechard's  methods,  452,  453 
from  silica,  tin,  451 
solubilities  of  acids  and  oxides,  449 
steel  and  alloys,  tungsten  in,  450 
technical  uses  of,  449 
Tungstic  acid,  det.  of  tungsten  as,  454 
Turbidity  tests  of  water,  534 
Turbidimetric  sulphur  table,  676,  677 
Turmeric  test  for  bismuth,  71 
Turpentine,   analysis    of,    determination   of 
color,  specific  gravity,  refractive  index; 
distillation,    polymerization,    standards 
of,  617,  618 
Type  metal,  analysis  of  (see  Alloys),  659 

Ultramarine  blue,  analysis  of,  637 
Universal  viscosimeter,  573 
Unsaponifiable  matter  in  oil,  identification 
.   of,  589 

in  Chinese  wood  oil,  613 
oils,  detection  and  determination  of,  588 
Uranium,  detection  of,  458 
uranous  and  uranyl  salts,  458 
estimation,  gravimetric  method  as  oxide, 

U308,  461 

volumetric  method,  461 
occurrence,  458 
preparation  and  solution  of  the  sample, 

ores,  459 

separation  from  H2S  group  elements,  cop- 
per, bismuth,  lead,  arsenic,  antimony, 
459 


896 


INDEX 


Uranium,  separation  from  iron  and  metals 
having  water  insoluble  carbonates, 

459 

from  vanadium,  459,  460 
solubilities,  459 

uranous  salts,  detection  of,  458 
uranyl  salts,  detection  of,  458 
uses,  458  ^ 

Uranium  oxide,  purity  test  of,  461 
Urbasch's  hydrogen  sulphide  generator,  37 
U.  S.  Bureau  of  Standards  Circular,  35 

references  on  melting-points,  62,  84,  88, 
118,  200,  210,  253,  270,  391,  448 

Valuation  of  aluminum  ores,  4 

of  fluorspar,  179,  186 

Vanadium,  detection,  test  with  ammonium 
sulphide,  hydrogen  sulphide,  hydrogen 
peroxide,  reducing  agents,  463 
comparsion  of  chromium  and  vanadium 

salts,  463 

test  for  in  steel,  464 
estimation,  general  procedures: 
gravimetric,  lead  acetate  method,  468 

mercurous  nitrate  method,  467 
volumetric,   H2S   or   SO2   reduction   to 
V2O4,  and  titration  with  KMnO4, 469 
zinc  reduction  to  V2O2  and  titration 

with  KMnO4,  470 
estimation,  special  methods: 

determination  of  vanadium  in  presence 

of  antimony  or  arsenic,  472 
in  presence  of  chromic  acid,  473 
in  presence  of  iron,  472 
in  presence  of  molybdenum,  471 
in  cupro-vanadium,  brasses  and 

bronzes,  476 
in  ferro-vanadium,  476 
in  steel  in  presence    or    absence  of 

chromium,  471,  475 
in  vanadium  ores,  475 
industrial  application,  464 
occurrence,  minerals  and  ores,  464 
preparation  and  solution  of  the  sample: 
decomposition  of  alloys,  iron  and  steel, 

466 
ores,  general  procedure,   ores  high  in 

silica,  ores  low  in  silica,  465 
separation    from    arsenic,    molybdenum, 

phosphoric  acid,  466 
chromium,  467 

solubilities,  element,  oxides  and  salts,  465 
Valenta  test  for  oil,  581 

of  animal  and  vegetable  oils,  581 
Vamari-Mitscherlich-Devarda    method    for 

nitrogen  in  soils,  304 
Vanier  absorption  bulb,  96 
Vanino  and  Treubert,  reduction  of  bismuth 

salt,  68 
Van   Nostrand   Chem.   Annual,   Olsen,     88 

93,  119,  210,  253,  270 
Vapor  tension  of  sulphuric  acid,  502 


Varnish,  analysis  of,  determination  of  acid 
number,  ash,  fixed  oils  and  resins,  flash 
point,  separation  of  polymerized  oils  and 
resins,  618-620 

Varrentrapp  and  Will  bulbs  (Fig.  117),  693 
Vegetable  oils  (see  Oils,  Fats,  Waxes),  580 
or  animal  oils,  test  for,  590 
detection  of  manganese  in,  257 
Vehicles,  paint  analysis,  610 
liquid  percentage  of,  610 
separation  of  components,  611 
Vermilion,  analysis  of,  635 
Vicat  needle  for  testing  cement,  644 
Virgili,  arsenic  determination,  37 
Viscosity  in  oils,  determination  of,  572 
Viscosimeters  for  determining  viscosity  in 

oils,  572,  573 
Vogel's  modification  of  Pisani's  method  for 

silver,  384 
Volatile  combustible  matter  in  coal,  apparatus 

for,  (104),  674 
method  for  det.  in  coal,  674 
matter  in  sodium  fluoride,  188 
Volatiles  in  paint,  distillation  of,  611 

sulphur  in  coal,  675 
Volhard's  method  for  determining  bromine, 

81 

chlorine,  125 
iodine,  207 
manganese,  266 
silver,  378 
Volumetric  methods.     See  under  element  in 

question. 

Vortmann  and  Metzel  method  for  determin- 
ing antimony,  23 

Wagner's  solution,  90 

Warrington,  traces  of  lead,  243 

Warwick  and  Kyle  on  oxalate  method  for 

bismuth,  68 
Water  analysis,  general  considerations,  533 


mineral  analysis,  545 
abstract  of  general  sch 

545 


erne  of  analysis, 


acidity,  determination  of,  553 
alkalinity,  determination  of,  552 
alumina,  determination  of,  546 
ammonia,  determination  of,  555 
calcium,  determination  of,  548 
calcium  sulphate,  determination  of,  561 
carbonic  acid,  determination  of,  553 
chlorine,  determination  of,  554 
corrosion,  acid  waters,  determination 

of,  563 

field  assay,  565  ^ 
foaming  and  priming,  563 
hardness  in,  558 
hydrogen  sulphide  in,  555 
interpretation  of  analysis,  562 
iron,  determination  of,  547 
irrigating  waters,  564 
lime  value  of,  561 


SUBJECT   INDEX 


897 


Water,  magnesium  in,  449 

chloride,  560 
manganese-bismuthate  method  of  de- 

.termining,  550 

Knorre's  persulphate  method,  550 
mineral  residue  in  water,  555 
nitrates,  determination  of,  554 
oil,  determination  of,  556 
oxygen  dissolved,  determination  of, 

phosphates,  determination  of,  548  _ 
residue,  total  mineral,  determination 

of,  555 

scale,  determination  of,  563 
silica,  determination  of,  546 
soda,  value  for,  561 
sodium  and  potassium,  determination 

of,  55i 

softening  of,  563 
sulphates,   determination^  as  barium 

sulphate,  by  benzidine  method, 

551 

traces  of  impurities,  copper,  lead,  tin 

and  zinc,  557 
sanitary  analysis,  534 

ammonia,  albuminoid  in,  537 
free,  determination  of,  536 
chemical  tests,  536  ^ 
chlorine  determination  in,  (present  as 

chloride),  541 
color  test,  534 

interpretation  of  analysis,  543 
nitrogen  as  nitrate,  539 
as  nitrite,  538 
organic,  537 
odor  test,  535 
oxygen  consumed,  541 
physical  tests,  534 
residue,  total  solids  in,  542 
turbidity  test,  534 
in  burning  oils,  571 
in  paint  vehicles,  611 
iodide  or  iodine  in,  201 
percentage    required    in    standard    sand 

mortar  (table),  645 
vapor  in  air,  736 
Waxes,  601 
Weber  and  Hintz  on  sulphur  precipitation, 

395 
Weighing  tubes  for  acids  (Figs.  80,  81,  82,  83), 

506-508 

Weiss,  separating  zinc  as  sulphide,  485 
Welch-Weber  method  for  detecting  tin,  419 
Weller's  determination  of  antimony,  27 
Welsbach  mantles,  cerium  determination  in, 

116 

Westphal  balance  for  determining  specific 
gravity  apparatus  (Fig.  87),  569 
specific  gravity  of  oils,  method  for,  569 
Wet  combustion  process  for  carbon  deter- 
mination, 102 
gold  assay  of  minerals,  194 


Wet  meter,  690 

tests  for  copper,  149 
Whitby's  method  for  silver  detection  and 

estimation,  376 
White  lead,  corroded,  analysis  of,  625 

sublimed,  analysis  of,  622  _ 
Whiting  paint  pigment,  analysis  of,  632 
Whitmer  and  Cain's  method  for  vanadium 

in  steel,  471 
Wiborg's   method   for   determining   carbon 

(reference),  107 
Wildenstein's  volumetric  method  for  sulphur, 

403 
Wilkie's  colorimetric  method,  for  traces  of 

lead,  243 
Winkler,  titration  of  ammonia  in  boric  acid, 

294 
Winkler's  spiral   absorption  apparatus  for 

gas  (Fig.  1 1 8),  693 
Winterstein  and  Herzfeld,  iodine  liberation 

with  peroxide,  207 
Witherite,  analysis  of ,  60 

commercial  valuation  of,  60 
Wolffs  absorpton  tube  (Fig.  118),  693 
Wood's  metal,  analysis  of  (see  Alloys),  664 
Wurster's  method  for  ozone,  .,697 

Xenon  in  the  atmospheric  air,  292 
Ytterbium,  112,  113 

Zinc,  detection  of,  477 
estimation,  general  procedure,  477 
gravimetric  determination  by  electroly 

sis,  479 

as  the  oxide,  ZnO,  479 
as  the  sulphate,  ZnSO4,  479 
volumetric  methods,  ferrocyanide  titra« 
tion: 

(a)  in  acid  solution,  480,  483 

(b]  in  alkaline  solution,  481 
estimation,  special  procedures: 

determination  in  alloys,  in  brass  and 

bronze,  669 
in  German  silver,  669 
in  manganese  phosphorus  bronze,  670 
in  copper  (metallic),  169 
in  lead  (metallic),  252 
in  Rose's  metal,  664 
in  soft  solder,  663 
determination  in  composite  white  paintr 

634 

In  orange  and  yellow  pigments,  639 
in  white  lead  (sublimed),  623 
determination    in    material    containing 

cadmium,  482 
in  presence  of  carbonaceous  matter, 

482 

in  presence  of  metallics,  482 
in  material  containing  insoluble  zinc, 

485. 
determination  in  ores,  copper-bearing,  481 


898 


INDEX 


Zinc,  estimation  in  water,  557,  558 

in  zinc  dust,  487 

moisture  determination  in  pulp,  478 
preparation  of  the  sample,  478 
separation   from   antimony,   arsenic,   bis- 
muth, cadmium,  copper,  and  lead,  478 
from  aluminum,  iron,  manganese,  cobalt 

and  nickel,  478-480 
from  iron,  665 

sulphide  precipitation  of  zinc,  483-485 
spelter,  determination  of  impurities  in,  489 
cadmium   in,  electrolytic  and  sulphide 

methods,  491 
iron  in,  hydrogen  sulphide  and  colori- 

metric  methods,  490 
lead    in,    electrolytic    and    lead    acid 

methods,  489,  490 
"traces,"  determination  of  small  amounts 

of  zinc,  487 
Zinc  metal,  preparation  of  pure,  for  arsenic 

determination,  42 
metallic,  testfor  iridium,  330 
for  palladium,  333 
for  platinum,  325 
for  rhodium,  336 
for  ruthenium,  334 
for  titanium,  432 
for  vanadium,  463 

Zinc    arsenite,    determination    of    arsenic, 
soluble  and  insoluble,  in,  32 


Zinc  lead  and  leaded  zinc,  analysis  of,  626 
oxide,  determination  of  zinc  as,  479 
impurities  in,  492,  627 
in  the  commercial  product,  630 
reduction  method  for  determining  iridium, 

33i 

of  chlorates,  128 
of  iron  salts,  216 
of  phosphomolybdate  for  phosphorus 

determination,  317 
of  vanadium  salts,  470 
references  to  literature  concerning  methods 

492,  493  ^ 

sulphate  in  zinc  lead  and  leaded  zinc,  627 
in  lithopone,  630 
weighing  zinc  as,  479 
sulphide  in  lithopone,  630 
Zirconium,  detection  of,  494 
estimation,    gravimetric   precipitating   as 
hydroxide,  496 

as  oxide  in  presence  of  iron  oxide, 

496 

as  phosphate,  496 
occurrence,  494 

preparation  and  solution  of  the  sample, 
materials  high  in  silica,  494 

mineral  oxides,  495 
separation    from    cerium    and    the    iron 

groups,  495 
from  iron,  titanium,  and  thorium,  495 


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W.  A.     Portland  Cement  Industry 8vo,  3  oo 

Brown,    Wm.     N.      Dipping,    Burnishing,     Lacquering    and    Bronzing 

Brass  Ware   i2mo,  *i  50 

—  Handbook    on    Japanning i2mo,  *a  oo 

Brown,  Wm.  N.     The  Art  of  Enamelling  on  Metal i2mo,  *2  oo 

—  House    Decorating    and    Painting i2ino,  *2  oo 

—  History  of  Decorative  Art i2mo  *o  50 

—  Workshop   Wrinkles    Svo,  *i  oo 

Browne,  C.  L.    Fitting  and  Erecting  of  Engines Svo,  *i  50 

Browne,  R.  E.     Water  Meters i6mo,  o  75 

Bruce,  E.  M.     Detection  of  Common  Food  Adulterants i2mo,  i  40 

Brunner,  R.     Manufacture  of  Lubricants,  Shoe  Polishes  and  Leather 

Dressings    Svo,  3  50 

Buel,  R.  H.     Safety  Valves iGmo,  o  75 

Bunkley,  J.  W.     Military  and  Naval  Recognition  Book i6mo,  i  oc 

Burley,  G.  W.     Lathes.     Their  Construction  and  Operation i2mo,  2  oo 

—  Machine  and  Fitting  Shop  Practice.     2  vols i2mo,  each,  2  oo 

—  Testing  of  Machine  Tools i2mo,  2  oo 

Burnside,    W.      Bridge    Foundations i2mo,  *2  oo 


NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 


Curstail,  F.  W.    Energy  Diagram  for  Gas.     With  Text 8vo,  150 

-  Diagram.     Sold  separately *i  oo 

Burt,  W.  A.    Key  to  the  Solar  Compass i6mo,  leather,  2  50 

Buskett,   E.   W.     Fire   Assaying i2mo,  *i  25 

Butler,   H.  J      Motor  Bodies   and   Chassis 8vo,  *s  oo 

Byers,  H.  G.,  and  Knight,  H.  G.    Notes  on  Qualitative  Analysis 8vo, 

^A't'o.1  Edition  in  Preparation.) 

Cain,  W.    Brief  Course  ir»  the  Calculus i2mo,  *i  75 

Elastic    Arches    i6mo,  o  75 

Maximum    Stresses    i6mo,  o  75 

Practical    Designing    Retaining    of    Walls i6mo,  o  75 

— —  Theory    of    Steel-concrete    Arches   and    of    Vaulted     Structures. 

i6mo,  o  75 

Theory   of    Voussoir   Arches i6mo,  o  75 

Symbolic    Algebra    i6mo,  o  75 

Calvert,    G.    T.     The   Manufacture    of    Sulphate    of    Ammonia    and 

Crude  Ammonia   i2mo,  4  oo 

Camm,    S.^    Aeroplane    Construction i2mo,  3  oo 

Carhart,   H.   S.     Thermo   Electromotive   Force   in   Electric    Cells, 

(In  I'ress.) 

Carey,  A.  E.,  and  Oliver,  f.  W.     Tidal  Lands 8vo,  5  oo 

Carpenter,   F.   D.     Geographical   Surveying i6mo, 

Carpenter,  R.  C.,  and  Diederichs,  H.    Internal  Combustion  Engines. 8vo,  5  50 

Carter,  H.  A.     Ramie  (Rhea),  China  Grass i2mo,  *3  oo 

Carter,  H.  R.     Modern  Flax,  Hemp,  and  Jute  Spinning 8vo,  *s  50 

—  Bleaching,  Dyeing  and  Finishing  of  Fabrics 8vo,  *i  25 

Ckry,  E.  R.     Solution  of  Railroad  Problems  with  the  Slide  Rule. .  i6mo,  *i  oo 

Casler,  M.  D.    Simplified  Reinforced  Concrete  Mathematics i2mo,  *i  oo 

Cathcart,  W.  L.     Machine  Design.     Part  I.  Fastenings 8vo,  *3  oo 

Cathcart,  W.  L.,  and  Chaff ee,  J.  I.     Elements  of  Graphic  Statics .  .  .8vo,  *3  oo 

— —  Short  Course  in  Graphics i2mo,  i  50 

Caven,  R.  M.,  and  Lander,  G.  D.    Systematic  Inorganic  Chemistry.  i2mo,  2  25 

Chalkley,  A.  P.    Diesel  Engines 8vo,  *4  oo 

Chalmers,  T.  W.     The  Production  and  Treatment  of  Vegetable  Oils, 

4to,  7  50 

Chambers'    Mathematical    Tables 8vo,  2  50 

Chambers,  G.  F.     Astronomy i6mo,  *i  50 

Chappel,    E.      Five    Figure    Mathematical    Tables 8vo,  2  50 

Charnock,    Mechanical    Technology 8vo,  3  50 

Charpentier,    P.     Timber 8vo,  *6  oo 

Chatley,  H.    Principles  and  Designs  of  Aeroplanes i6mo,  o  75 

—  How  to  Use  Water  Power t i2mo,  *i  50 

—  Gyrostatic   Balancing    8vo,  *i  25 

Child,  C.  D.     Electric  Arc 8vo,  *2  oo 

Christian,  M.    Disinfection  and  Disinfectants i2mo,  2  50 

Christie,  W.  W.     Boiler-waters,  Scale,  Corrosion,  Foaming 8vo,  *3  oo 

Chimney  Design  and  Theory 8vo,  *3  oo 

—  Furnace    Draft    i6mo,  o  75 

-  Water:  Its  Purification  and  Use  in  the  Industries 8vo,  *2  oo 

Church's    Laboratory   Guide 8vo,  2  50 

Clapham,  J.  H.     Woolen  and  Worsted  Industries 8vo,  2  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG         7 

Clapperton,   G'.     Practical   Papermaking 8vo    (Reprinting.) 

Clark,  A.  G.     Motor  Car  Engineering. 

•  Vol.   I.     Construction *4  oo 

Vol.  II.     Design    8vo,  *3  50 

Clark,  C.  H.     Marine  Gas  Engines.     New  Edition 2  oo 

Clarke,  J.  W.,  and  Scott,  W.    Plumbing  Practice. 

Vol.      I.     Lead  Working  and  Plumbers'  Materials 8vo,  *4  oo 

Vol.    II.    Sanitary  Plumbing  and  Fittings (In  Press.) 

Vol.  III.     Practical  Lead  Working  on  Roofs (In  Press.) 

Clarkson,  R.  P.     Elementary  Electrical  Engineering  (In  Press.) 

Clerk,  D.,  and  Idell,  F.  E.    Theory  of  the  Gas  Engine .i6mo,  o  75 

Clevenger,  S.  R.     Treatise  on  the  Method  of  Government  Surveying. 

i6mo,   morocco,  2  50 

Clouth,  F.     Rubber,  Gutta-Percha,  and  Balata 8vo,  *6  oo 

Cochran,  J.    Concrete  and  Reinforced  Concrete  Specifications 8vo,  *2  50 

-  Treatise  on  Cement  Specifications 8vo,  *i  oo 

Cocking,  W.  C.     Calculations  for  Steel-Frame  Structures i2mo,  *2  50 

Coffin,  J.  H.  C.    Navigation  and  Nautical  Astronomy i2mo,  3  oo 

Colburn,  Z.,  and  Thurston,  R.  H.     Steam  Boiler  Explosions.  ..  .i6mo,  o  75 

Cole,   R.   S*     Treatise  on   Photographic   Optics i2mo,  2  oo 

Coles-Finch,  W.     Water,  Its  Origin  and  Use 8vo,  *s  oo 

Collins,  C.  D.    Drafting  Room  Methods,  Standards  and  Forms Svo,  2  oo 

Collins,  S.  Hoare.     Plant  Products  and  Chemical  Fertilizers Svo,  3  oo 

Collis,  A.  G.     High  and  Low  Tension  Switch-Gear  Design Svo,  *3  50 

—  Switchgear    ; i2mo,  o  50 

Colver,    E.   D.    S.     High    Explosives ! Svo,  12  50 

Comstock,  D.  F.,  and  Troland,  L.  T.     The  Nature  of  Electricity  and 

Matter    Svo,  2  50 

Coombs,  H.  A.     Gear  Teeth ." i6mo,  o  75 

Cooper,  W.  R.    Primary  Batteries Svo,  *6  oo 

Copperthwaite,  W.  C.     Tunnel  Shields 4to,  *g  oo 

Corfield,  W.  H.     Dwelling  Houses i6mo,  o  75 

—  Water  and   Water-Supply i6mo,  o  75 

Cornwall,  H.  B.     Manual  of  Blow-pipe  Analysis Svo.  *2  50 

Cowee,  G.  A.    Practical  Safety  Methods  and  Devices Svo,  4  oo 

Cowell,  W.  B.     Pure  Air,  Ozone,  and  Water i2mo,  *2  50 

Craig,  J.  W.,  and  Woodward,  W.  P.     Questions  and  Answers  Abo*t 

Electrical  Apparatus i2mo,  leather,  i  50 

Craig,  T.     Motion  of  a  Solid  in  a  Fuel i6mo,  o  75 

—  Wave    and    Vortex    Motion i6mo,  o  75 

Crehore,  A.  C.     Mystery  of  Matter  and  Energy Svo,  i  oo 

— ,  New  Theory  of  the  Atom (In   Press.) 

Crocker,  F.  B.,  and  Arendt,  M.    Electric  Motors Svo,  *2  50 

Crocker,  F.  B.,  and  Wheeler,  S.  S.  The  Management  of  Electrical  Ma- 
chinery   i2mo,  *i  oo 

Crosby,  E.  U.,  Fiske,  H.  A.,  and  Forster,  H.  W.  Handbook  of  Fire 

Protection i2mo,  4  oo 

Cross,  C.  F.,  Bevan,  E.  J.,  and  Sindall,  R.  W.  Wood  Pulp  and  Its 
Uses  Svo  (Rtprinttng.) 

Crosskey,   L.    R.     Elementary    Perspective Svo,  150 


8          D.  VAN  NOSTRAXD  CO.'S  SHORT  TITLE  CATALOG 

Crosskey,  L.  R.,  and  Thaw,  J.     Advanced  Perspective 8vo,  2  oo 

Culley,  J.  L.     Theory  of  Arches i6mo,  o  75 

Gushing,  H.  C.,  Jr.,  and  Harrison,  N.    Central  Station  Management. .,  *a  oo 


Dadourian,  H.  M.    Analytical  Mechanics i2mo,  *3  oo 

— Graphic  Statics    8vo,  o  75 

Danby,  A.    Natural  Rock  Asphalts  and  Bitumens .8vo,  *2  50 

Darling,  E.  R.     Inorganic  Chemical  Synonyms nmo,  i  oo 

Davenport,  C.     The   Book 8vo,  2  oo 

Davey,  N.    The  Gas  Turbine 8vo,  *4  oo 

Davies,  F.  H.     Electric  Power  and  Traction 8vo,  *2  oo 

— —  Foundations   and   Machinery   Fixing i6mo,  i  oo 

Deerr,   N.     Sugar   Cane 8vo,  10  oo 

De  la  Coux,  H.    The  Industrial  Uses  of  Water 8vo,  5  oo 

Del  Mar,  W.  A.    Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.    Deep-level  Mines  of  the  Rand 4to,  *io  oo 

De  Roos,  J.  D.  C.     Linkages i6mo,  o  75 

Derr,  W.  L.    Block  Signal  Operation Oblong  i2mo,  *i  50 

Desaint,  A.    Three  Hundred  Shades  and  How  to  Mix  Them 8vo,  *g  oo 

De  Varona,  A.     Sewer  Gases i6mo,  o  75 

Devey,  R.  G.    Mill  and  Factory  Wiring i2mo,  i  oo 

Dichmann,  Carl.     Basic   Open  Hearth   Steel   Process i2mo,  4  oo 

Dieterich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins.  ..  .8vo,  *3  50 

Dilworth,  E.  C.    Steel  Railway  Bridges 4to.  :;:4  oo 

Dinger,  Lieut.  H.  C.    Care  and  Operation  of  Naval  Machinery. ..  i2mo,  *s  oo 
Dixon,  D.  B.     Machinist's  and  Steam  Engineer's  Practical  Calculator. 

i6mo,  morocco,  i  25 

Dommett,  W.  E,     Motor  Car  Mechanism i2mo,  *2  oo 

Dorr,  B.  F.    The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  morocco,  2  oo 

Draper,  C.  H.     Heat  and  the  Principles  of  Thermo-Dynamics.  .i2mo,  2  25 

Draper,  E.  G.     Navigating  the  Ship i2mo,  2  oo 

Dubbel,  H.    High  Power  Gas  Engines 8vo,  *5  oo 

Dumesny,  P.,  and  Noyer,  J.    Wood  Products,  Distillates,  and  Extracts. 

8vo,  *5  oo 
Duncan,  W.  G.,  and  Penman,  D.  The  Electrical  Equipment  of  Collieries. 

8vo,  *5  oo 

Dunkley,  W.  G.  Design  of  Machine  Elements.  Two  volumes.  .8vo,each,  2  oo 

Dunstan,  A.  E.,  and  Thole,  F.  B.  T.     Textbook  of  Practical.  Chemistry. 

i2mo,  *i  40 

Durham,  H.  W.     Saws 8 vo,  2  50 

Duthie,  A.  L.     Decorative  Glass  Processes 8vo,  2  50 

Dwight,  H.  B.     Transmission  Line  Formulas 8vo,  *2  oo 

Dyke,  A.  L.     Dyke's  Automobile  and  Gasoline  Engine   Encyclopedia, 

8vo,  5  oo 

Dyson,  S.  S.     A  Manual  of  Chemical  Plant.     12  parts.  ..  .4to,  paper,  7  50 

Dyson,  S.  S.,  and  Clarkson,  S.  S.     Chemical  Works 8vo,  *g  oo 

Eccles,  W.  H.     Wireless  Telegraphy  and  Telephony iamo,  *8  80 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  9 

Eck,  J.     Light,   Radiation  and  Illumination 8vo,  250 

Eddy,  L.  C.     Laboratory  Manual  of  Alternating  Currents i2mo,  o  50 

Edelman,  P.  Inventions  and  Patents 121110,  *i  50 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments 8vo,  500 

Edler,    R.     Switches    and    Switchgear 8vo,  400 

Eissler,  M.     The  Metallurgy  of  Gold 8vo,  9  oo 

The  Metallurgy  of  Silver 8vo,  4  oo 

—  The  Metallurgy   of   Argentiferous    Lead 8vo,  6  25 

A  Handbook  on  Modern  Explosives 8vo,  5  oo 

Ekin,  T.  C.    Water  Pipe  and  Sewage  Discharge  Diagrams folio,  *3  oo 

Electric  Light  Carbons,  Manufacture  of 8vo,  i  oo 

Eliot,  C.  W.,  and  Storer,  F.  H.     Compendious  Manual  of  Qualitative 

Chemical  Analysis i2mo,  *i  25 

Ellis,  C.     Hydrogenation  of  Oils 8vo,  7  50 

—  Ultraviolet   Light,  Its   Applications   in   Chemical   Arts i2mo, 

(In  Press} 

and  Meigs,  J.  V.     Gasolene  and  Other  Motor  Fuels..  (In  Press.} 

Ellis,  G.     Modern  Technical  Drawing 8vo,  *2  oo 

Ennis,  Wm.  D.     Linseed  Oil  and  Other  Seed  Oils 8vo,  5  oo 

. Applied    Thermodynamics 8vo,  5  oo 

—  Flying  Machines  To-day I2mo,  *i  50 

-  Vapors  for  Heat  Engines I2mo,  *i  oo 

Errnen,  W.  F.  A.     Materials  Used  in  Sizing 8vo,  *2  oo 

Erwin,  M.    The  Universe  and  the  Atom i2mo    (Reprinting.} 

Ewing,  A.  J.     Magnetic  Induction  in  Iron 8vo,  500 

Fairchild,  J.  F.     Graphical  Compass  Conversion  Chart  and  Tables...  o  50 

Fairie,  J.     Notes  on  Lead  Ores i2mo,  *o  50 

—  Notes  on  Pottery  Clays i2mo,  *2  oo 

Fairley,  W.,  and  Andre,  Geo.  J.     Ventilation  of  Coal  Mines.  ..  .i6mo,  o  75 

Fairweather,  W.  C.    Foreign  and  Colonial  Patent  Laws 8vo,  *3  oo 

Falk,   K.   G.     Chemical    Reactions:    Their   Theory   and   Mechanism. 

(In  Press.} 

Fanning,  J.  T.     Hydraulic  and  Water-supply  Engineering 8vo,  *5  oc 

Farnsworth,  P.  V.     Shop  Mathematics i2mo   (In  Press.} 

Fay,  I.  W.     The  Coal-tar  Dyes 8vo,  5  oa 

Fernbach,  R.  L.     Glue  and  Gelatine , 8vo,  *3  oo 

Findlay,  A.    The  Treasures  of  Coal  Tar i2mo,  2  oo 

Firth,  J.  B.    Practical  Physical  Chemistry i2mo,  i  25 

Fischer,  E.     The  Preparation  of  Organic  Compounds i2mo,  i  50 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing.  .  .8vo,  4  oo 

Fleischmann,  W.     The  Book  of  the  Dairy 8vo,  4  50 

Fleming,  J.  A.     The  Alternate-current  Transformer.     Two  Volumes.  8 vo. 

Vol.    I.     The  Induction  of  Electric  Currents *6  50 

Vol,  II.     The  Utilization  of  Induced  Currents 6  50 

—  Propagation   of   Electric   Currents 8vo,  3  50 

—  A  Handbook  for  the  Electrical  Laboratory  and  Testing  Room.     Two 

Volumes 8vo,  each,  *6  50 

Fleury,  P.     Preparation  and  Uses  of  White  Zinc  Paints 8vo,  3  oo 

Flynn,  P.  J.     Flow  of  Water i2mo,  o  75 

—  Hydraulic    Tables    i6mo,  o  75 


10        D.  V-.  N  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Foster,  H.  A.     Electrical  Engineers'  Pocket-book.      (Seventh  Edition.) 

i2mo,  leather,  5  oo 

—  Engineering  Valuation  of  Public  Utilities  and  Factories 8vo,  *3  oo 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings i2mo,  *i  50 

—  The  Solution  of  Alternating  Current  Problems 8vo  (In  Press.) 

Fox,    W.    G.     Transition    Curves i6rno,      o  75 

Fox,  W.,  and  Thomas,  C.  W.     Practical  Course  in  Mechanical  Draw- 
ing   i2mo,  i  25 

Foye,  J.  C.     Chemical  Problems i6mo,  o  75 

—  Handbook    of    Mineralogy i6mo,  o  75 

Francis,  J.  B.     Lowell  Hydraulic  Experiments 4to,  15  oo 

Franzen,  H.     Exercises  in  Gas  Analysis izmo,  *i  oo 

Fraser,   E.   S.,  and  Jones,  R.   B.     Motor  Vehicles   and  Their  Motors, 

&vo,  fabrikoid,  2  oo 

Freudemacher,  P.  W.     Electric   Mining  Installations i2mo,  i  oo 

Friend,  J.  N.     The  Chemistry  of  Linseed  Oil tamo,  i  oo 

Fritsch,  J.     Manufacture  of  Chemical  Manures. 8vo,  5  oo 

Frye,  A.  I.     Civil  Engineers'  Pocket-book i2mo,  leather,  *5  oo 

Fuller,  G.  W.     Investigations  into  the  Purification  of  the  Ohio  River. 

4to,  *io  oo 

Furnell,  J.    Paints,  Colors,  Oils,  and  Varnishes 8vo. 

Gant,  L.  W.     Elements  of  Electric  Traction 8vo,  *2  50 

Garcia,  A.  J.  R.  V.     Spanish-English  Railway  Terms 8vo,  3  oo 

Gardner,  H.  A.     Paint  Researches,  and  Their  Practical  Applications, 

8vo,  :;:5  oo 
Garforth,  W.  E.     Rules  for  Recovering  Coal  Mines  after  Explosions  and 

Fires i2mo,  leather,  i  50 

Garrard,  C.  C.    Electric  Switch  and  Controlling  Gear 8vo,  *6  oo 

Gaudard,    J.      Foundations i6mo,  o  75 

Gear,  H.  B.,  and  Williams,  P.  F.     Electric  Central  Station  Distribution 

Systems    8vo,  *3  50 

Geerligs,  H.  Cj  P.     Cane  Sugar  and  Its  Manufacture 8vo,  *6  oo 

Chemical  Control  in  Cane  Sugar  Factories 4to,  5  oo 

Geikie,  J.     Structural  and  Field  Geology 8vo,  4  50 

—  Mountains.     Their  Growth,  Origin  and  Decay 8vo,  4  50 

-  The  Antiquity  of  Man  in  Europe 8vo,  *s  oo 

Georgi,  F.,  and  Schubert,  A.     Sheet  Metal  Working 8vo,  3  50 

Gerhard,  W.  P.     Sanitation,  Watersupply  and  Sewage  Disposal  of  Country 

HoUSeS I2H10,  *2    00 

Gas   Lighting i6mo,  o  75 

—  Household   Wastes    i6mo,  o  75 

-  House    Drainage    i6mo,  o  75 

—  Sanitary  Drainage  of  Buildings i6mo,  o  75 

Gerhardi,    C.    W.    H.      Electricity    Meters 8vo,  *7  20 

Geschwind,  L.     Manufacture  of  Alum  and  Sulphates 8vo,  5  oo 

Gibbings,  A.  H.     Oil  Fuel   Equipment   for  Locomotives.     8vo. 

(Reprinting.') 

Gibbs,  W.  E.     Lighting  by  Acetylene I2mo,  *i  50 


D.  VAN  NOSTRAMD  CO.'S  SHORT  TITLE  CATALOG  n 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  6  oo 

—  Water  Hammer  in  Hydraulic  Pipe  Lines i2mo,  2  50 

Gibson,  A.  H.,  and  Ritchie,  E.  G.    Circular  Arc  Bow  Girder 4to,  *s  50 

Gilbreth,  F.  B.     Motion  Study i2mo,  *2  oo 

—  Primer  of  Scientific  Management i2mo,  *i  oo 

Gillmore,  Gen.  Q.  A.    Roads,  Streets,  and  Pavements i2mo,  i  25 

Godfrey,  E.     Tables  for  Structural  Engineers i6mo,  leather,  *2  50 

Golding,  H.  A.     The  Theta-Phi  Diagram zamo,  *2  oo 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor.  .".'.. 8vo,  ^3  oo 

Goodchild,   W.     Precious    Stones 8vo,  2  50 

Goodell,    J.    M.      The    Location,    Construction    and    Maintenance    of 

Roads    8vo,  2  oo 

Goodeve,  T.  M.     Textbook  on  the   Steam-engine xarno,  2  50 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  4  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine i2mo,  i  oo 

—  Calculus    •. . . .  i6mo,  o  75 

—  High  Masonry  Dams i6mo,  o  75 

Gould,  E.  S.    Practical  Hydrostatics  and  Hydrostatic  Formulas.  .i6mo,  o  75 

Gratacap,  L.  P.     A  Popular  Guide  to  Minerals 8vo,  *2  oo 

Gray,  H.  H.    Gas-Works  Products 8vo   (In  Prrss.) 

Gray,  J.     Electrical  Influence  Machines 12010,  2  oo 

—  Marine    Boiler   Design i2mo    (Reprinting.} 

Greenhill,  G.     Dynamics  of  Mechanical  Flight 8vo,  *2  50 

Greenwood,  H.   C.     The   Industrial   Gases 8vo    (/;;    Press.} 

Gregorius,    R.      Mineral    Waxes i2mo,  3  oo 

Grierson,  R.     Some  Modern  Methods  of  Ventilation 8vo,  *3  oo 

Griffiths,  A.  B.     A  Treatise  on  Manures i2mo    (Reprinting.} 

Gross,  E.     Hops 8vo,  *5  oo 

Grossman,  J.     Ammonia  and  Its  Compounds 121110,  i  50 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases   or  Electricity. 

8vo,  2  50 

Grover,  F.     Modern  Gas  and   Oil   Engines 8vo,  *s  oo 

Gruner,   A.     Power-loom   Weaving 8vo,  *s  50 

Grunsky,  C.  E.     Topographic  Stadia  Surveying i6mo,  2  oo 

Guldner,  H.     Internal  Combustion  Engines (In   Press.} 

Gunther,  C.   0.     Integration 8vo,  i  50 

Gurden,  R.  L.     Traverse  Tables. folio,  half  morocco,  *7  50 

Guy,  A.  E.     Experiments  on  the  Flexure  of  Beams 8vo,  *i  25 

Haenig,   A.     Emery   and   Emery   Industry 8vo,  *2  50 

Hainbach,   R.     Pottery    Decoration i2mo,  3  50 

Hale,    A.   J.     The   Manufacture    of   Chemicals    by    Electrolysis.     8vo, 

(In  Press  ) 

Hale,   W.  J.     Calculations   of   General    Chemistry i2mo,  i  50 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles i2mo,  *2  oo 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  50 

Hall,  W.  S.    Elements  of  the  Differential  and  Integral  Calculus.  ..  .8vo,  2  75 

—  Descriptive  Geometry 8vo  volume  and  a   4to  atlas,  4  oo 

Haller,  G.  F.,  and  Cunningham,  E.  T.     The  Tesla  Coil i2mo,  *i  25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

— The   Use    of   the   Slide   Rules i6mo,  o  75 

Worm   and   Spiral   Gearing i6mc,  o  75 


12        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics 8vo,  i  50 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics i2mo,  *i  50 

Haring,  H.     Engineering  Law. 

Vol.  I.     Law  of  Contract 8vo,  *4  oo 

Harper,  J.  H.     Hydraulic  Tables  on  the  Flow  of  Water i6mo,  *2  oo 

Harris,  S.  M.    Practical  Topographical  Surveying (In  Press.} 

Harrow,  B.    Eminent  Chemists  of  Our  Times:  Their  Lives  and  Work. 

(In  Press.) 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hatt,  J.  A.  H.     The  Colorist square  i2mo,  *i  50 

Hausbrand,  E.    Drying  by  Means  of  Air  and  Steam i2mo,  2  50 

—  Evaporating,  Condensing  and  Cooling  Apparatus 8vo,  6  oo 

Hausmann,  E.     Telegraph  Engineering 8vo,  *3  oo 

Hausner,  A.    Manufacture  of  Preserved  Foods  and  Sweetmeats.  ..  .8vo,  3  50 
Hawkesworth,  J.     Graphical  Handbook  for  Reinforced  Concrete  Design. 

4to,  2  oo 

Hay,  A.    Continuous  Current  Engineering 8vo,  *2  50 

Hayes,  H.  V.    Public  Utilities,  Their  Cost  New  and  Depreciation. .  .8vo,  *2  oo 

—  Public  Utilities,  Their  Fair  Present  Value  and  Return 8vo,  *2  oo 

Heath,  F.  H.    Chemistry  of  Photography 8vo.  (In  Press.) 

Heather,  H.  J.  S.     Electrical   Engineering 8vo,  4  50 

Heaviside,  0.     Electromagnetic  Theory.     Vols.  I  and  II....8vo,  each, 

(Reprinting.) 

Vol.    Ill 8vo     (Reprinting.)' 

Heck,  R.  C.  H.     The  Steam  Engine  and  the  Turbine 8vo,  4  50 

Steam-Engine  and  Other  Steam  Motors.    Two  Volumes. 

Vof.  I.     Thermodynamics  and  the  Mechanics 8vo,  4  50 

7el.  II.     Form,   Construction,   and   Working 8vo,  550 

Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Heermann,  P.     Dyers*  Materials 1 21110,  3  oo 

Hellot,  Macquer  and  D'Apligny.  Art  of  Dyeing  Wool,  Silk  and  Cotton.  8vo,  *2  oo 
Hering,  C.,  and  Getman,  F.  H.     Standard  Tables  of  Electro-Chemical 

Equivalents    i2mo,  *2  oo 

Bering,  D.  W.     Essentials  of  Physics  for  College  Students 8vo,  2  25 

Herington,  C.  F.     Powdered  Coal  as  Fuel 8vo,  3  oo 

Herrmann,  G.    The  Graphical  Statics  of  Mechanism .i2mo,  2  oo 

Herzfeld,  J.     Testing   of  Yarns   and   Textile    Fabrics 8vo. 

(New  Edition  in  Preparation.) 

Hildenbrand,    B.    W.      Cable-Making i6mo,  075 

Hilditch,  T.  P.     A  Concise  History  of  Chemistry 12010,  *i  50 

Hill,  M.  J.  M.     The  Theory  of  Proportion 8vo,  *2  50 

Hillhouse,  P.  A.     Ship  Stability  and  Trim 8vo,  4  50 

Hiroi,  I.     Plate  Girder  Construction i6mo,  o  75 

— 'Statically-Indeterminate  Stresses i2mo,  2  50 

Hirshfeld,  C.  F.    Engineering  Thermodynamics i6mo,  o  75 

Hoar,  A.     The  Submarine  Torpedo  Boat i2mo,  *2  oo 

Hobart,  H.  M.    Heavy  Electrical  Engineering 8vo,  *4  50 

—  Design    of    Static    Transformers i2mo,  2  50 

Electricity 8vo,  *2  oo 

—  Electric  Trains 8vo,  *2  50 

Electric  Propulsion  of  Ships 8vo,  *2  50 


13 

Hobart,  J.  F.    Hard  Soldering,  Soft  Soldering  and  Brazing I2mo,  i  25 

Hobbs,  W.  R.  P.    The  Arithmetic  of  Electrical  Measurements i2mo,  o  75 

Hoff,  J.  N.     Paint  and  Varnish  Facts  and  Formulas i2mo,  i  50 

Hole,  W.     The  Distribution  of  Gas 8vo,  *8  50 

Hopkins,  N.  M.     Model  Engines  and  Small  Boats i2mo,  i  25 

—  The    Outlook    for    Research    and    Invention i2mo.  2  oo 

Hopkinson,  J.,  Shoolbred,  J.  N.,  and  Day,  R.  E.    Dynamic  Electricity. 

i6mo.  o  75; 

Horner,  J.     Practical  Ironf ounding 8vo,  *2  oo 

—  Gear  Cutting,  in  Theory  and   Practice 8vo    (Reprinting.) 

Houghton,  C.  E.     The  Elements  of  Mechanics  of  Materials i2mo,  2  50 

Houstoun,  R.  A.    Studies  in  Light  Production lamo,  2  oo 

Hovendesn,  F.    Practical  Mathematics  for  Young  Engineers i2mo,  *i  50 

Howe,  G.    Mathematics  for  the  Practical  Man i2mo,  i  50 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthenware. 

8vo,  paper,  *o  50 

Hoyt,  W.  E.     Chemistry  by  Experimentation 8vo,  *o  70 

Hubbartf,    E.     The    Utilization   of   Wood-waste .8vo,  *2  50 

Hiibner,  J.   Bleaching  and  Dyeing  of  Vegetable  and  Fibrous  Materials. 

8vo   (Reprinting.). 

Hudson,  0.  F.    Iron  and  Steel 8vo,  *  ^ 

Humphreys,  A.  C.  The  Business  Features  of  Engineering  Practice .  8vo,  2  50 

Hunter,  A.    Bridge  Work 8vo.  (In  Press:) 

Hurst,  G.  H.     Handbook  of  the  Theory  of  Color 8vo,  *s  50- 

—  Dictionary  of  Chemicals  and  Raw  Products 8vo,  *5  oa 

—  Lubricating  Oils,  Fats  and  Greases 8vo,  *s  oo 

Soaps 8vo,  *6  oo 

Hurst,  G.  H.,  and  Simmons,  W.  H.    Textile  Soaps  and  Oils 8vo,  3  50 

Hurst,  H.  E.,  and  Lattey,  R.  T.     Text-book  of  Physics 8vo,  *3  oo 

Also  published  in  three  parts. 

Part      I.    Dynamics  and  Heat i  50 

Part    IL     Sound   and   Light i  50 

Part  III.    Magnetism  and  Electricity *i  50 

Hutchinson,  R.  W.,  Jr.    Long  Distance  Electric  Power  Transmission. 

i2mo,  *3  oo 

Hutchinson,  R.  W.,  Jr.,  and  Thomas,  W.  A.    Electricity  in  Mining.  i2mo, 

(In  Press.) 

Hyde,  E.  W.     Skew  Arches i6mo.  o  75 

Hyde,  F.  S.    Solvents,  Oils,  Gums,  Waxes ,,,,,, 8<vo,  *2  oo 

Induction  Coils    i6mo.  o  75 

Ingham,  A.  E.    Gearing.    A  practical  treatise 8vo,  *2  50 

Ingle,  H.     Manual  of  Agricultural   Chemistry 8vo    (In  Press.) 

Inness,  C.  H.    Problems  in  Machine  Design i2mo,  *s  oo 

—  Centrifugal  Pumps i2mo,  *3  oo 

-  The  Pan f , i2mo,  *4  oo 

Jacob,  A.,  and  Gould,  E.  S.    On  the  Designing  and  Construction  of 

Storage   Reservoirs    i6mo.  o  75 

Jacobs,  F.  B.    Cam  Design  and  Manufacture (  In  Press.) 


I4       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

James,  F.  D.     Controllers  for  Electric  Motors 8vo.  q  oo 

Jehl,  F.     Manufacture  of  Carbons 8vo.  5  oo 

Jennings,  A.  S.     Commercial  Paints  and  Painting 8vo.  2  so 

Jennison,  F.  H.    The  Manufacture  of  Lake  Pigments.  .8vo  (In  Press.) 

Jepson,  G.    Cams  and  the  Principles  of  their  Construction 8vo,  *i  50 

—  Mechanical  Drawing 8vo  (In  Preparation.) 

Jervis-Smith,   F.  J.     Dynamometers 8vo.  4  oo 

Jockin,  W.    Arithmetic  of  the  Gold  and  Silversmith i2mo,  *i  oo 

Johnson,  C.  H.,  and  Earle,  R.  P.     Practical  Tests  for  the  Electrical 

Laboratory  (  In  Press.) 

Johnson,  J.  H.     Arc  Lamps  and  Accessory  Apparatus lamo,  o  75 

Johnson,  T.  M.     Ship  Wiring  and  Fitting i2mo    (Reprinting.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.     Elements  of  Agricultural  Chemistry 

and  Geology i2mo,  2  60 

Joly,  J.     Radioactivity  and  Geology i2mo   (Reprinting.) 

Jones,  H.  C.    Electrical  Nature  of  Matter  and  Radioactivity i2mo,  *2  oo 

Nature   of  Solution 8vo,  *3  50 

"i New  Era  in  Chemistry , i2mo,  *2  oo 

Jones,  J.  H.    Tinplate  Industry 8vo,  *3  oo 

Jones,  M.  W.    Testing  Raw  Materials  Used  in  Paint i2mo,  *2  50 

Jordan,  L.  C.    Practical  Railway  Spiral i2mo,  leather,  *i  50 

Jiiptner,  H.  F.  V.     Siderclogy:  The  Science  of  Iron 8vo,  *s  oo 

Kapp,   G.     Alternate    Current    Machinery i6mo,  075 

Kapper,  F.     Overhead  Transmission  Lines 4to,  "4  oo 

Keim,  A.  W.    Prevention  of  Dampness  in  Buildings 8vo,  *2  50 

Keller,  S.  S.,  and  Knox,  W.  E.    Analytical  Geometry  and  Calculus...  2  oo 
Kemble,  W.  T.,  and  Underbill,  C.  R.     The  Periodic  Law  and  the  Hydrogen 

Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F.    Handbook  of  Rocks 8vo,  *i  50 

Kennedy,  A.  B.  W.,  and  Thurston,  R.  H.     Kinematics  of  Machinery. 

i6mo,  o  75 
Kennedy,  A.  B.  W.,  Unwin,  W.  C.,  and  Idell,  F.  E.     Compressed  Air. 

i6mo,  o  75 

Kennedy,  R.     Flying  Machines:  Practice  and  Design i2mo,  2  50 

—  Principles  of  Aeroplane  Construction 8vo,  *a  oo 

Kent.  W.     Strength   of   Materials i6mo,  075 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis.  .8vo    (In  Press.) 

—  Electrometallurgy    8vo,  2  50 

Electro-Thermal   Methods   of  Iron   and   Steel   Production 8vo,  *3  oo 

Kinzbrunner,  C.     Continuous  Current  Armatures 8vo,  i  50 

-  Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kinzer,  H.,  and  Walter,  K.    Theory  and  Practice  of  Damask  Weaving, 

8vo,  4  oo 
Kirkaldy,    A..    W.,    and    Evans,    A.    D.      History    and    Economics    of 


Transport  8vo, 


3  oo 


Kirkbride,  J.     Engraving  for  Illustration 8vo,    *i  oo 

Kirschke,  A.     Gas  and  Oil  Engines i2mo,    *i  50 


D    VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  15 

Klein,  J.  F.     Design  of  a  High-speed  Steam-engine 8vo,  *5  oo 

—  Physical  Significance  of  Entropy 8vo,  *i  50 

Klingenberg,  G.     Large   Electric   Power   Stations 4to,  *5  oo 

Knight,  R.-Adm.  A.  M.     Modern  Seamanship 8vo,  *6  50 

—  Pocket   Edition lamo,   f abrikoid,  3  oo 

Knott,  C.  G.,  and  Mackay,  J.  S.     Practical  Mathematics 8vo,  2  50 

Knox,  J.     Physico-Chemical  Calculations i2mo,  i  50 

—  Fixation  of  Atmospheric  Nitrogen.  . . i2mo,  i  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

Hydroelectric  Developments  and  Engineering 4to,  *5  oo 

Roller,   T.     The   Utilization   of   Waste   Products 8vo,  *5  oo 

—  Cosmetics    8vo,  *2  50 

Koppe,  S.  W.     Glycerine i2mo,  *s  50 

Kozmin,    P.    A.     Flour    Milling 8vo,  7  50 

Krauch,    C.      Chemical    Reagents 8vo,  7  oo 

Kremann,  R.     Application  of  the  Physico-Chemical  Theory  to  Tech- 
nical Process  and  Manufacturing  Methods 8vo,  300 

Kretchmar,  K.     Yarn  and  Warp   Sizing 8vo,  *s  oo 

Laff argue,  A.     Attack  in  Trench  Warfare i6mo,  o  50 

Lallier,  E.  V.    Elementary  Manual  of  the  Steam  Engine i2mo,  *2  oo 

Lambert,  T.     Lead  and  Its  Compounds 8vo,  *3  50 

—  Bone    Products    and    Manures 8vo,  *3  50 

Lamborn,  L.  L.     Cottonseed  Products 8vo,  4  oo 

—  Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 

Lamprecht,  R.    Recovery  Work  After  Pit  Fires 8vo,  5  oo 

Lanchester,  F.  W.    Aerial  Flight.     Two  Volumes.     8vo. 

Vol.  I.     Aerodynamics *6  oo 

Vol.    II.     Aerodonetics *6  oo 

Lanchester,  F.  W.    The  Flying  Machine 8vo,  *3  oo 

—  Industrial   Engineering:    Present  and   Post- War   Outlook.  .  .i2mo,  i  oo 

Lange,  K.  R.    By-Products  of  Coal-Gas  Manufacture lamo,  2  50 

La   Rue,  B.  F.     Swing  Bridges i6mo,  o  75 

Lassar-Cohn,  Dr.     Modern   Scientific    Chemistry i2mo,  2  25 

Latimer,  L.  H.,  Field,  C.  J.,  and  Howell,  J.  W.    Incandescent  Electric 

Lighting    i6mo,  o  75 

Latta,  M.  N.     Handbook  of  American  Gas-Engineering  Practice.  .8vo,  5  oo 

—  American  Producer  Gas  Practice 4to,  *6  oo 

Laws,  B.  C.     Stability  and  Equilibrium  of  Floating  Bodies 8yo,  4  50 

Lawson,    W.    R.      British    Railways.      A    Financial    and    Commercial 

Survey 8vo,  200 

Leask,  A.  R.     Refrigerating  Machinery i2mo    (Reprinting.} 

Lecky,  S.  T.  S.    "Wrinkles"  in  Practical  Navigation 8vo,  10  oo 

Pocket   Edition i2mo,  5  oo 

—  Danger   Angle    i6mo,  2  50 

Le  Doux,  M.     Ice-Making  Machines i6mo,  o  75 

Leeds,  C.  C.     Mechanical  Drawing  for  Trade  Schools oblong  4to,  2  25 

—  Mechanical   Drawing  for  High   and   Vocational   Schools 4to,  i  50 

—  Principles    of    Engineering    Drawing 8vo    (In    'Press.) 

Lef evre,    L.     Architectural   Pottery 4to,  7  oo 

Lehner,  S.    Ink  Manufacture 8vo,  2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture 8vo,  *i  50 

Letts,  E.  A.     Fundamental  Problems  in  Chemistry 8vo,  *2  oo 

Le   Van,  W.  B.     Steam-Engine   Indicator i6mo,  o  75 


j6        D.  VAN   XOSTRAXD  t^O.'S  SHORT    "1TLE  CATALOG 

Lewes,  V.  B.    Liquid  and  Gaseous  Fuels Svo,      3  oo 

—  Carbonization   of    Coal 8vo,       5  oo 

Lewis  Automatic  Machine  Rifle ;   Operation  of , i6mo, 

Licks,  H.  E.     Recreations  in  Mathematics i2mo,       i  50 

Lieber,  B.  F.     Lieber's  Five  Letter  American  Telegraphic  Code  .8vo,  :;:i5  co 
Spanish    Edition    8vo,  -15  oo 

—  French    Edition    8vo,  ::  15  oo 

Terminal  Index 8vo,  *2  50 

-  Lieber's  Appendix folio,  *is  oo 

—  Handy  Tables 4*0,  *2  50 

Bankers  and  Stockbrokers'  Code  and  Merchants  and  Shippers' 

Blank  Tables 8vo,  *i$  oo 

—  100,000,000  Combination  Code 8vo,  *io  oo 

Livermore,  V.  P.,  and  Williams,  J.     How  to  Become  a  Competent  Motor- 
man  i2mo,  *i  oo 

Livingstone,   R.     Design   and    Construction   of    Commutators 8vo,  450 

Mechanical  Design  and  Construction  of  Generators 8vo,  4  50 

Lloyd,  S.  L.     Fertilizer  Materials i2mo,  2  oo 

Lockwood,  T.  D.    Electricity.  Magnetism,  and  Electro-telegraph   . . .  .8vo,  2  50 

—  Electrical  Measurement  and  the  Galvanometer 12010,  o  75 

Lodge,  O.  J.  Elementary  Mechanics i2mo,  i  50 

Loewenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps 5  oo 

Lomax,  J.  W.     Cotton  Spinning i2mo,  i  50 

Lord,  R.  T.     Decorative  and  Fancy  Fabrics Svo,  "3  50 

Loring,  A.  E.    A  Handbook  of  the  Electromagnetic  Telegraph. .  .i6mo,  o  75 

Lowy,  A.     Organic  Type  Formulas o  10 

Lubschez,  B.  J.    Perspective i2mo,  *i  50 

Lucke,  C.  E.     Gas  Engine  Design Svo,  *;>.  oo 

—  Power  Plants:   Design,  Efficiency,  and  Power  Costs.     2  vols. 

(In  Preparation.) 
Luckiesh,   M.     Color   and    Its    Application Svo,      350 

—  Light  and  Shade  and  Their  Applications Svo,      3  oo 

—  Visual    Illusions (In    Preparation.) 

Lunge,  G.    Coal-tar  and  Ammonia.     Three  Volumes Svo,  "25  oo 

—  Technical  Gas  Analysis Svo,    *4  50 

—  Manufacture  of  Sulphuric  Acid  and  Alkali.     Four  Volumes.  . .  .8vo, 

Vol.    I.     Sulphuric  Acid.     In  three  parts (Reprinting.) 

Vol.  I.     Supplement    Svo    ( tttprinlinu.) 

Vol.  II.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda.    In  two 

parts (In    Press.) 

Vol.  III.    Ammonia  Soda (In  Press. ) 

Vol.  IV.     Electrolytic  Methods (In  Press.) 

—  Technical  Chemists'  Handbook 121110,   leather,    *4  oo 

Technical   Methods  of  Chemical   Analysis. 

Vol.   I.      In  two  parts Svo,  *is  oo 

Vol.  II.     In  two  parts Svo,  *i8  oo 

Vol.   III.     In   two   parts .Svo,  *i8  oo 

The  set    (3  vols.)    complete *5o  oo 

Luquer,  L.  M.     Minerals  in  Rock  Sections ..  ..Svo,     *i  5» 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  17 

MacBride,  J.  D.     A  Handbook  of  Practical  Shipbuilding, 

i2mo,  fabrikoid,  2  oo 

Macewen,  H.  A.    Food  Inspection 8vo,  *2  50 

Mackenzie, 'N.  F.     Notes  on  Irrigation  Works 8vo,  *2  50 

Mackie,  J.     How  to  Make  a  Woolen  Mill  Pay 8vo,  *2  oo 

Maguire,  Wm.  R.     Domestic  Sanitary  Drainage  and  Plumbing  ....  8vo,  4  oo 

Malcolm,  H.  W.     Submarine  Telegraph  Cable 9  oo 

Malinovzsky,    A.      Analysis    of    Ceramic    Materials    and    Methods    of 

Calculation  (In  Press.) 

Mallet,  A.    Compound  Engines i6mo, 

Mansfield,    A.    N.     Electro-magnets i6mo,  o  75 

Marks,  E.  C.  R.    Construction  of  Cranes  and  Lifting  Machinery.  i2mo,  *2  75 

—  Manufacture  of  Iron  and  Steel  Tubes i2mo,  2  50 

—  Mechanical  Engineering  Materials i2mo,  *i  50 

Marks,  G.  C.     Hydraulic  Power  Engineering 8vo,  4  50 

Marlow,  T.  G.     Drying  Machinery  and  Practice. ..  .8vo   (Reprinting.) 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete 8vo,  *2  50 

Reinforced  Concrete  Compression  Member  Diagram.     Mounted  on 

Cloth  Boards *i .  50 

Marsh,  C.  F.,  and  Dunn,  W.     Manual  of  Reinforced  Concrete  and  Con- 
crete  Block   Construction i6mo,   cloth,  2  oo 

Marshall,  W.  J.f  and  Sankey,  H.  R.     Gas  Engines 8vo,  2  oo 

Martin,   G.     Triumphs  and  Wonders  of   Modern  Chemistry 8vo,  *3  oo 

—  Modern   Chemistry   and   Its    Wonders 8vo,  *3  oo 

Martin,  N.     Properties  and  Design  of  Reinforced  Concrete 8vo,  i  50 

Martin,  W.   D.     Hints  to   Engineers 12010,  2  oo 

Massie,  W.  W.,  and  Underbill,  C.  R.    Wireless  Telegraphy  and  Telephony. 

i2mo,  *i  oo 

Mathot,  R.  E.     Internal  Combustion  Engines 8vo,  5  oo 

Maurice,  W.     Electric  Blasting  Apparatus  and  Explosives 8vo,  *3  50 

Shot  Firer's  Guide 8vo,  *i  50- 

Maxwell,  F.     Sulphitation  in  White  Sugar  Manufacture i2mo,  4  oo 

Maxwell,  J.  C.     Matter  and  Motion i6mo,  o  75 

Maxwell,  W.  H.,  and  Brown,  J.  T.    Encyclopedia  of  Municipal  and  Sani- 
tary Engineering 4to,  *io  oo 

Mayer,  A.  M.    Lecture  Notes  on  Physics 8vo,  2  oo 

McCracken,  E.  M.,  and  Sampson,  C.  H.     Course  in  Pattern  Making. 

(In  Press.) 

McCullough,  E.     Practical  Surveying i2mo,  2  50 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 

McGibbon.  W.  C.    Indicator  Diagrams  for  Marine  Engineers 8vo,  -3  50 

—  Marine  Engineers*  Drawing  Book oblong  4to,  *2  50 

McGibbon,  W.  C.     Marine  Engineers  Pocketbook i2mo,  *4  50 

Mclntosh,   J.    G.      Technology    of    Sugar 8vo,  *6  oo 

—  Industrial    Alcohol     8vo,  *3  50 

—  Manufacture  of  Varnishes  and  Kindred  Industries.     Three  Volumes. 

8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling 7  oo 

Vol.  II.    Varnish  Materials  and  Oil  Varnish  Making.  (Reprinting.) 

Vol.  III.     Spirit  Varnishes  and  Materials (Reprinting.) 

McKay,  C.   W.     Fundamental   Principles   of  the  Telephone  Business. 

8vo.    (In  Press.) 


l8        D.  VAN  NOSTRAXD  CO.'S  SHORT  TITLE  CATALOG 

McKillop,  M.,  and  McKillop,  A.  D.     Efficiency  Methods i2mo,  i  50 

McKnight,  J.  D.,  and  Brown,  A.  W.     Marine  Multitubular  Boilers....  *a  50 

McMaster,  J.   B.     Bridge  and  Tunnel  Centres i6mo,  o  75 

McMechen,  F.  L.     Tests  for  Ores,  Minerals  and  Metals i2mo,  *i  co 

McNair,  Jas.   B.     Citrus   By-Products (In    Press.) 

Heade,  A.     Modern   Gas   Works   Practice 8vo,  *8  50 

Melick,  C.  W.     Dairy  Laboratory  Guide i2mo,  *i  25 

•^Mentor."     Self-Instruction  for  Students  in  Gas  Supply.     lamo. 

Elementary    2  50 

Advanced 2  50 

Self-Instruction    for   Students    in    Gas    Engineering.      121110. 

Elementary    2  oo 

Advanced   2  oo 

Merivale,  J.  H.     Notes  and  Formulae  for  Mining  Students i2mo,  i  oo 

Merritt,  Wm.  H.     Field  Testing  for  Gold  and  Silver i6mo,  leather,  2  oo 

Mertens.     Tactics  and  Technique  of  River  Crossings 8vo,  2  50 

Mierzinski,  S.     Waterproofing  of  Fabrics 8vo,  2  50 

Miessner,  B.  F.     Radio  Dynamics i2mo,  *2  oo 

Miller,  G.  A.     Determinants i6mo, 

Miller,  W.  J.     Introduction  to  Historical  Geology i2mo,  2  25 

Milroy,  M.  E.  W.     Home  Lace-making i2mo,  *i  oo 

Mills,  C.  N.    Elementary  Mechanics  for  Engineers 8vo,  *i  oo 

Mitchell,  C.  A.     Mineral  and  Aerated  Waters 8vo,  *3  oo 

Mitchell,  C.  A.,  and  Prideaux,  R.  M.     Fibres  Used  in  Textile  and  Allied 

Industries 8vo,  3  50 

Mitchell,  C.  F.,  and  G.  A.     Building  Construction  and  Drawing.     i2mo. 

Elementary   Course 2  oo 

Advanced   Course    3  oo 

Monckton,   C.    C.    F.     Radiotelegraphy 8vo,  200 

Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish,  Spanish- 
English  Technical  Terms 641110,  leather,  *i  oo 

Montgomery,  J.  H.     Electric  Wiring  Specifications i6mo,  *i  oo 

Moore,  E.  C.  S.    New  Tables  for  the  Complete  Solution  of  Ganguillet  and 

Kutter's   Formula    8vo,  *6  oo 

Moore,  Harold.     Liquid  Fuel  for  Internal  Combustion  Engines ...  8vo,  5  oo 
Morecroft,  J.  H.,  and  Hehre,  F.  W.     Short  Course  in  Electrical  Testing. 

8vo,  i  75 

Morgan,  A.  P.     Wireless  Telegraph  Apparatus  for  Amateurs i2mo,  *i  50 

Morrell,  R.   S.,  and  Waele,  A.  E.     Rubber,  Resins,   Paints  and  Var- 
nishes     8vo    (In    Press. ) 

Moses,  A.  J.     The  Characters  of  Crystals 8vo,  *2  oo 

--and  Parsons,  C.   L.     Elements  of   Mineralogy 8vo,  *3  50 

Mosr,  S.  A.     Elements  of  Gas  Engine   Design i6mo,  o  75 

•The    Lay-out    of   Corliss    Valve    Gears i6mo,  075 

Mulford,  A.  C.     Boundaries  and  Landmarks i2mo,  *i  oo 

Mulford,  A.   C.     Boundaries  and   Landmarks i2mo,  i  oo 

Munby,  A.  E.     Chemistry  and  Physics  of  Building  Materials.  ..  .8vo,  a  50 

Murphy,  J.  G.    Practical  Mining i6mo,  i  oo 

Murray,  B.  M.     Chemical  Reagents 8vo   (    /;/  l>n-ss  > 

Murray,   J.    A.     Soils   and    Manures 8vc,  2  oo 

Nasmith,  J.     The  Student's  Cotton  Spinning. 8vo,  4  50 

—    Recent   Cotton   Mill   Construction i2mo,  300 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  19 

Neave,  G.  B.,  and  Heilbron,  I.  M.     Identification  of  Organic  Compounds. 

tamo,  i  50 

Neilson,  R.  M.    Aeroplane  Patents 8vo,  *2  oo 

Nerz,    F.      Searchlights 8vo    (Reprinting.) 

Newbigin,  M.  I.,  and  Flett,  J.  S.     James  Geikie,  the  Man  and  the 

Geologist 8vo,  3  50 

Newbiging,  T.     Handbook  for  Gas  Engineers  and  Managers 8vo,  7  50 

Newell,  F.  H.,  and  Drayer,  C.  E.    Engineering  as  a  Career,  .i2mo,  cloth,  *i  oo 

Nicol,  G.     Ship  Construction  and  Calculations 8vo,  *io  oo 

Nipher,  F.  E.     Theory  of  Magnetic  Measurements i2mo,  i  oo 

Nisbet,  H.     Grammar  of  Textile  Design 8vo,  7  50 

Nolan,    H.      The    Telescope i6mo,  o  75 

Norie,  J.  W.    Epitome  of  Navigation  (2  Vols.) octavo,  15  oo 

—  A  Complete  Set  of  Nautical  Tables  with  Explanations  of  Their 

Use octavo,  6  50 

North,  H.  B.    Laboratory  Experiments  in  General  Chemistry 1210.0,  *J  oo 

O'Connor,  H.     The   Gas  Engineer's   Pocketbook i2mo,   leather,  400 

Ohm,  G.  S.,  and  Lockwood,  T.  D.     Galvanic  Circuit i6mo,  o  75 

Olsen,  J.  C.     Text-book  of  Quantitative  Chemical  Analysis 8vo,  400 

Ormsby,   M.   T.   M.     Surveying lamo,  2  oo 

Oudin,  M.  A.     Standard  Polyphase  Apparatus  and  Systems 8vo,  *3  oo 

Pakes,  W.  C.  C.,  and  Nankivell,  A.  T.     The  Science  of  Hygiene  .  .8vo,  *i  75 

Palaz,   A.     Industrial    Photometry 8vo,  4  oo 

Palmer,  A.  R.     Electrical   Experiments i2mo,  075 

—  Magnetic  Measurements  and  Experiments i2mo,  o  75 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parker,  P.   A.  M.     The   Control    of   Water 8vo,  600 

Parr,  G.  D.  A.     Electrical  Engineering  Measuring  Instruments.  ..  .8vo,  *s  50 
Parry,  E.  J.     Chemistry  of  Essential  Oils  and  Artificial  Perfumes. 

Vol.1.     Monographs    on    Essential    Oils 900 

Vol.  II.     Constituents  of   Essential   Oils,  Analysis 7  oo 

—  Foods  and  Drugs.     Two  Volumes. 

Vol.     I.     The    Analysis    of    Food    and    Drugs 8vo,  950 

Vol.11.     The   Sale  of  Food  and   Drugs  Acts 8vo,  3  50 

—  and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *5  oo 

Parry,  L.     Notes  on  Alloys 8vo,  *3  50 

—  Metalliferous  Wastes    8vo,  *2  50 

—  Analysis  of  Ashes  and  Alloys 8vo,  *2  50 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  50 

Parshall,  K.  F.,  and  Eobart,  H.  M.     Electric  Railway  Engineering. 4to,  7  50 

Parsons,  J.   L.     Land  Drainage 8vo,  *i  50 

Parsons,  S.  J.  Malleable  Cast  Iron 8vo    (Reprinting.) 

Partington,  J.  R.     Higher  Mathematics  for  Chemical  Students.  .  lamo,  2  50 

—  Textbook  of  Thermodynamics. 8vo,  *4  oo 

—  The    Alkali    Industry 8vo,  3  oo 

Patchell,  W.  H.     Electric  Power  in  Mines 8vo,  *4  oo 

:?.r.  er^-n.  G.  W.  L.    Winng;  Ca^ulat'ons i2mo,  *2  50 

S]p"trJ"  M>r<e  S'V^allins  Installations i2mo,  *i   50 

Patterror,  D,     The  CoJor  Printing  of  Carpet  Yarns 8vo,  *3  50 

—  Color    Mr.tfhirscr    in    Textiles 8vo,  *3  50 

Textile   Color   Mixing 8vo,  *3  50 


20       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare  Pipes.  .8vo,  *2  oo 

Transmission  of  Heat  through  Cold-storage  Insulation i2mo,  *i  oo 

Payne,    D.    W.      Iron    Founders'    Manual 8vo,  4  oo 

Peddle,  R.  A.    Engineering  and  Metallurgical  Books i2mo,  *i  50 

Peirce,  B.     System  of  Analytic  Mechanics 4to,  10  oo 

Linear   Associative   Algebra 4to,  2  50 

Perkin,  F.  M.,  and  Jaggers,  E.  M.     Elementary  Chemistry izmo,  i  oo 

Perrin,  J.     Atoms 8vo,  *2  50 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution 8vo,  *3  50 

Petit,  G.     White  Lead  and  Zinc  White  Paints.    3vo,  *2  oo 

Petit,  R.     How  to  Build  an  Aeroplane 8vo,  i  50 

Pettit,    Lieut.   J.    S.     Graphic  Processes i6mo,  075 

Philbrick,   P.   H.     Beams   and   Girders i6mo, 

Phin,  J.     Seven  Follies  of  Science i2mo,  *i  50 

Pickworth,  C.  N.    Logarithms  for  Beginners 12010,  boards,  i  oo 

—  The  Slide  Rule i2mo,  i  50 

Pilcher,  R.  B.     The  Profession  of  Chemistry i2mo    (In   Press.) 

Pilcher,  R.  B.,  and  Butler- Jones,  F.    What  Industry  Owes  to  Chemical 

Science. i2mo,  i  50 

Plattner's  Manual  of  Blow-pipe  Analysis.    Eighth  Edition,  revised.  8vt,  4  oo 

Plympton,  G.  W.     The  Aneroid  Barometer i6mo,  o  75 

How   to   Become   an    Engineer „ i6mo,  075 

Van   Nostrand's   Table   Book i6me,  o  75 

Pochet,  M.  L.     Steam  Injectors x6mo,  o  75 

Pocket  Logarithms  to  Four  Places i6mo,  o  75 

i6mo,  leather,  i  oo 

Polleyn,  F.     Dressings  and  Finishings  for  Textile  Fabrics 8vo,  *3  50 

Pope,  F.  G.    Organic  Chemistry i2mo,  2  50 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph 8vo,  i  50 

Popplewell,  W.  C.     Prevention   of  Smoke 8vo,  *3  50 

—  Strength  of  Materials Svo,  *2  50 

Porritt,  B.  D.     The  Chemistry   of   Rubber i2mo,  i  oo 

Porter,  J.  R.    Helicopter  Flying  Machine . .   ismo,  i  50 

Potts,  H.  E.     Chemistry  of  the  Rubber  Industry Svo,  2  50 

Practical  Compounding  of  Oils,  Tallows  and  Grease 8vo,  *3  50 

Pratt,  A.  E.    The  Iron  Industry Svo  (In  Press.} 

— <  The  Steel  Industry Svo    (In  Press.) 

Pratt,  Jas.  A.    Elementary  Machine  Shop  Practice (In  Press.) 

Pratt,  K.    Boiler  Draught iimo,  *i  25 

Prelini,  C.    Earth  and  Rock  Excavation Svo,  *3  oo 

—  Graphical  Determination  of  Earth  Slopes Svo,  *2  oo 

Tunneling.    New  Edition Svo,  *3  oo 

Dredging.    A  Practical  Treatise Svo,  *3  oo 

Prescott,  A.  B.,  and  Johnson,  0.  C.  Qualitative  Chemical  Analysis.  .8vo,  4  oo 
Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative  Chemistry. 

Prideaux,  E.  B.  R.    Problems  in  Physical  Chemistry Svo,  *2  oo 

-  The  Theory  and  Use  of  Indicators Svo,  5  oo 

Prince,  G.  T.    Flow  of  Water i2mo,  *2  oo 

Pull,  E.     Modern  Steam  Boilers Svo,  5  oo 

Pullen,  W.  W.  F.     Application  of  Graphic  Methods  to  the  Design  of 

12010,  *i  50 

Strictures    i2rao,  3  oo 

Injectors:    Theory,  Construction   and   Working i2mo,  *2  oo 

-  Indicator  Diagrams svo,  3  o-> 

-  Engine  Testing Svo, 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  21 

Purday,  E.  F.  P.     The  Diesel  Engine  Design Svo   (In  Press.) 

Putsch,  A.     Gas  and  Coal-dust  Firing 8vo,  *2  50 

Rafter,  G.  W.    Mechanics  of  Ventilation i6mo,  o  75 

—  Potable  Water   i6mo,  o  75 

—  Treatment    of    Septic    Sewage i6mo,  v  o  75 

—  and  Baker,  M.  N.    Sewage  Disposal  in  the  United  States.  ..  .4to,  6  oo 

Raikes,  H.  P.     Sewage  Disposal  Works 8vo,  *4  oo 

Randau,   P.     Enamels  and   Enamelling 8vo,  *$  oo 

Rankine,  W.  J.  M.,  and  Bamber,  E.  F.    A  Mechanical  Text-book.  .8vo,  4  oo 

—  Civil  Engineering  8vo.  7  50 

—  Machinery   and    Millwork 8vo,  6  oo 

—  The  Steam-engine  and  Other  Prime  Movers 8vo,  6  oo 

Rankine,  W.  J.  M.,  and  Bamber,  E.  F.     A  Mechanical  Text-book 8vo,  3  50 

Raphael,  F.  C.     Localization  of  Faults  in  Electric  Light  and  Power  Mains. 

8vo,  3  50 

Rasch,    E.     Electric    Arc    Phenomena 8vo,  2  oo 

Rathbone,  R.  L.  B.     Simple  Jewellery 8vo,  2  50 

Rausenberger,  F.     The  Theory  of  the  Recoil  Guns 8vo,  *5  oo 

Rautenstrauch,  W»  Notes  on  the  Elements  of  Machine  Design.  8 vo,  boards,  *  i  50 
Rautenstrauch,  W.,  and  Williams,  J.  T.     Machine  Drafting  and  Empirical 
Design. 

Part   I.  Machine    Drafting 8vo,  i  50 

Part  II.  Empirical  Design (In  Preparation.) 

Raymond,  E.  B.     Alternating  Current  Engineering i2mo,  *2  50 

Rayner,  H.     Silk  Throwing  and  Waste  Silk  Spinning :  .  .8vo, 

^Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap  and  Drysaltery  Trades, 

Svo,  *5  oo 

Recipes  for  Flint  Glass  Making i2mo,  *s  oo 

Redfern,  J.  B.,  and  Savin,  J.     Bells,  Telephones i6mo,  o  75 

Redgrove,   H.   S.     Experimental  Mensuration i2ino,  i  50 

Reed,  S.    Turbines  Applied  to  Marine  Propulsion *5  oo 

Reed's  Engineers'  Handbook f Svo,  *g  oo 

—  Key  to  the  Nineteenth  Edition  of  Reed's  Engineers'  Handbook.  .8vo,  4  oo 

—  Useful  Hints  to  Sea-going  Engineers i2mo,  3  oo 

Reid,  E.  E.    Introduction  to  Research  in  Organic  Chemistry.  (In  Press.} 
Reinhardt,  C.  W.     Lettering  for  Draftsmen,  Engineers,  and  Students. 

oblong  4to,  boards,  i  oo 
Reinhardt,  C.  W.   The  Technic  of  Mechanical  Drafting, 

oblong,  4to,  boards,  *i  oo 

Reiser,  F.     Hardening  and  Tempering  of  Steel i2mo,  2  50 

Reiser,  TJ.     Faults  in  the  Manufacture  of  Woolen  Goods Svo,  2  50 

—  Spinning  and  Weaving  Calculations Svo,  *5  oo 

Renwick,  W.  G.     Marble  and   Marble  Working.  ..  .8vo    (Reprinting.'} 

Reuleaux,    F.      The    Constructor 4to,  4  oo 

Rey,  Jean.     The  Range  of  Electric  Searchlight  Projectors Svo, 

(Reprinting.} 

Reynolds,  0.,  and  Idell,  F.  E.    Triple  Expansion  Engines i6mo,  o  75 

Rhead,  G.  F.     Simple  Structural  Woodwork i2mo,  *i  25 

Rhead,  G.  W.     British  Pottery  Marks Svo,  3  50 

Rhodes,  H.  J.     Art  of  Lithography Svo,  5  oo 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining  the  Differ- 
ential of  Functions i2mo,  o  50 


22        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Richards,  W.  A.    Forging  of  Iron  and  Steel i2mo,  2  co 

Richards,  W.  A.,  and  North,  H.  B.    Manual  of  Cement  Testing. .  .  .  12010,  *i  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity i2mo,  *2  oo 

Rideal,   E.    K.      Industrial    Electrometallurgy 8vo,  300 

—  The  Rare  Earths  and  Metals 8vo    (In  Press.) 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *5  cc 

—  The    Carbohydrates 8vo    (In    Press.) 

Riesenberg,  F.    The  Men  on  Deck 12010,  3  oo 

—  Standard  Seamanship  for  the  Merchant  Marine.  i2mo  (In  Press.) 

Rimmer,  E.  J.    Boiler  Explosions,  Collapses  and  Mishaps 8vo,  *i  75 

Rings,  F.     Reinforced  Concrete  in  Theory  and  Practice i2mo,  *4  50 

Reinforced  Concrete  Bridges 4to,  *5  oo 

Ripper,  W.     Course  of  Instruction  in  Machine  Drawing folio,  *6  oo 

Roberts,  F.  C.    Figure  of  the  Earth i6mo,  o  75 

Roberts,  J.,  Jr.     Laboratory  Work  in  JJlectrical  Engineering 8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers 8vo,  2  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels.  .i6mo,  o  75 
Railroad    Economics    i6mo,  o  75 

—  Wrought  Iron  Bridge  Members i6mo,  o  75 

Robson,  J.  H.     Machine  Drawing  and  Sketching 8vo,  *2  oo 

Roebling,  J.  A.    Long  and  Short  Span  Railway  Bridges folio,  25  oo 

Rogers,  A.     A  Laboratory  Guide  of  Industrial  Chemistry 8vo,  2  oo 

• Elements    of    Industrial    Chemistry 12010,  *3  oo 

Manual  of  industrial  Chemistry 8vo,  *5  oo 

Rogers,  F.     Magnetism  of  Iron  Vessels i6mo,  o  75 

Rohland,  P.     Colloidal  and  Crystalloidal  State  of  Matter i2mo, 

(Reprinting.) 

Rollinson,  C.     Alphabets Oblong,  i2mo,  *i  oo 

Rose,  J.     The  Pattern-makers'  Assistant 8vo,  2  50 

• Key  to  Engines  and  Engine-running 12010,  2  50 

Rose,  T.  K.     The  Precious  Metals 8vo,  2  50 

Rosenhain,    Vf.      Glass    Manufacture , 8vo,  5  oo 

—  Physical  Metallurgy,  An  Introduction  to , 8vo,  4  oo 

Roth,    W.    A.     Physical    Chemistry 8vo,  *2  oo 

Rowan,  F.  J.    Practical  Physics  of  the  Modern  Steam-boiler 8vo,  *3  oo 

—  and  Idellj  F.  E.     Boiler  Incrustation  and  Corrosion i6mo,  o  75 

Roxburgh,   W.     General    Foundry   Practice 8vo,  2  50 

Ruhmer,    E.      Wireless    Telephony 8vo,  4  50 

Russell,  A.     Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Rust,  A.     Practical  Tables  for  Navigators  and  Aviators 8vo,  3  50 

Rutley,   F.     Elements   of   Mineralogy i2mo,  150 

Sandeman,  E.  A.    Notes  on  the  Manufacture  of  Earthenware.  ..i2mo,  3  50 

Sanford,  P.  G.     Nitro-explosives 8vo,  *4  oo 

Saunders,   C.   H.     Handbook   of   Practical    Mechanics i6mo,  i  50 

leather,  2  oo 

Sayers,  H.  M.     Brakes  for  Tram  Cars 8vo,  *r  25 

Schaefer,   C.   T.     Motor   Truck   Design 8vo,  250 

Scheele,  C.  W.     Chemical  Essays fl  v.-»,  *2  50 

Scheithauer,  W.     Shale  Oils  and  Tars 8vo,  '4  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG       23 

Scherer,  \R.     Casein , .8vo,  3  50 

Schidrowitz,  P.    Rubber,  Its  Production  and  Industrial  Uses 8vo,  *6  oo 

Schindler,  K.     Iron   and   Steel   Construction   Works lamo,  *2  oo 

Schmall,  C.  N.    First  Course  in  Analytic  Geometry,  Plane  and  Solid. 

i2mo,  half  leather,  *i  75 

—  and  Shack,  S.  M.     Elements  of  Plane  Geometry i2mo,  i  25 

Schwarz,  E.  H.  L.     Causal  Geology 8vo,  *s  oo 

Schmeer,  L.     Flow   of   Water 8vo,  150 

Schweizer,  V.    Distillations  of  Resins 8vo,  5  oo 

Scott,  A.  H.     Reinforced  Concrete  in  Practice lamo,  2  oo 

Scott,   W.   W.     Qualitative   Analysis.     A   Laboratory  Manual.     New 

Edition    3  oo 

—  Standard   Methods    of   Chemical    Analysis 8vo,  *6  oo 

Scribner,  J.  M.    Engineers'  and  Mechanics'  Companion.  .i6mo,  leather,  i  50 
Scudder,    H.      Electrical    Conductivity    and    lonization    Constants    of 

Organic  Compounds 8vo,  *3  oo 

Seamanship,   Lectures   on i2mo,  2  oo 

Searle,  A.  B.    Modern  Brickmaking 8vo  (In  Press.) 

—  Cement,    Concrete    and    Bricks .8vo,  3  oo 

Searle,     G.    M.      "Sumners'     Method."      Condensed     and     Improved. 

i6mo,  o  75 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo,  10  oo 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.     Pocket-book  of  Marine  Engi- 
neering  i6mo,  leather,  5  oo 

Seeligmann,  T.,  Torrilhon,  G.  L.,  and  Falconnet,  H.    India  Rubber  and 

Gutta   Percha    8vo,  6  oo 

Seidell,  A.     Solubilities  of  Inorganic  and  Organic  Substances. ..  .8vo,  7  50 

Sellew,  W.  H.     Steel   Rails 4to,  *io  oo 

—  Railway  Maintenance   Engineering i2mo,  3  'oo 

Senter,  G.     Outlines  of  Physical  Chemistry i2mo,  *2  50 

—  Text-book  of  Inorganic  Chemistry i2mo,  *3  oo 

Sever,  G.  F.     Electric  Engineering  Experiments 8vo,  boards,  *i  oo 

Sever,  G.  F.,  and  Townsend,  F.    Laboratory  and  Factory  Tests  in  Elec- 
trical Engineering 8vo,  *2  50 

Sewall,  C.  H.    Wireless  Telegraphy 8vo,  *2  oo 

—  Lessons  in  Telegraphy tamo,  *i  oo 

Sexton,  A.  H,    Fuel  and  Refractory  Materials i2mo  (Reprinting.) 

—  Chemistry  of  the  Materials  of  Engineering i?.mo,  *s  oo 

Alloys  (Non-Ferrous)    8vo,  3  50 

Sexton,  A.  H.,  and  Primrose,  J.  S.  G.  The  Metallurgy  of  Iron  and  Steel. 

8vo,  *6  50 

Seymour,   A.     Modern   Printing   Inks 8vo,  3  oo 

Shaw,  Henry  S.  H.     Mechanical  Integrators i6mo,  o  75 

Shaw,  S.     History  of  the  Staffordshire  Potteries 8vo,  2  50 

—  Chemistry  of  Compounds  Used  in  Porcelain  Manuf acture . . .  .  8vo,  *6  oo 
Shaw,   T.   R.     Driving    of    Machine    Tools i2mo,  *2  oo 

—  Precision    Grinding    Machines i^mo,  5  oo 

Shaw,   W.   N.     Forecasting   Weather 8vo    (Reprinting.) 

Sheldon,   S.,   and   Hausmann,   E.     Dynamo   Electric   Machinery,   A.C. 

and  D.C 8vo    (In  Press.) 

(Electric  Traction  and  Transmission  Engineering i2mo,  2  50 

Physical  Laboratory  Experiments,  for  Engineering  Students.  .8vo,  *i  25 


24       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Sherriff,  F.  F.    Oil  Merchants'  Manual  and  Oil  Trade  Ready  Reckoner, 

Svo,  3  50 

Shields,  J.  E.     Notes  on  Engineering  Construction 12010,  i  50 

Shreve,  S.  H.     Strength  of  Bridges  and  Roofs Svo,  3  50 

Shunk,  W.  F.    The  Field  Engineer i2mo,  fabrikoid,  2  50 

Silverman,  A.,  and  Harvey,  A.  W.     Laboratory  Directions  and  Study 

Questions  in  Inorganic   Chemistry 4to,  loose   leaf,  2  oo 

Simmons,  W.  H.     Fats,  Waxes  and  Essential  Oils.. Svo    (In  Press.} 
Simmons,  W.  H.,  and  Appleton,  H.  A.    Handbook  of  Soap  Manufacture, 

3/0,  *.|  oo 

Simmons,  W.  H.,  and  Mitchell,  C.  A.     Edible  Fats  and  Oils Svo,  *3  50 

Simpson,  G.    The  Naval  Constructor i2mo,  fabrikoid,  *s  oo 

Simpson,  W.    Foundations Svo.   (In  Press.) 

Sinclair,  A.    Development  of  the  Locomotive  Engine. .  .8vo,  half  leather,  5  oo 

Sindall,  R.  W.    Manufacture  of  Paper Svo   (Reprinting.) 

Sindall,  R.  W.,  and  Bacon,  W.  N.    The  Testing  of  Wood  Pulp.  . .  .Svo, 

(Reprinting.) 

—  Wood  and  Cellulose Svo   ( In  Press.) 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations izmo,  *2  oo 

Smallwood,  J.  C.    Mechanical  Laboratory  Methods.  ..  .i2mo,  fabrikoid,  3  oo 

Smith,  C.  A.  M.     Handbook  of  Testing,  MATERIALS 8vo,  *2  50 

Smith,  C.  A.  M.,  and  Warren,  A.  G.     New  Steam  Tables Svo,  *i  25 

Smith,  C.  F.    Practical  Alternating  Currents  acd  Testing Svo,  *3  50 

Practical   Testing   of   Dynamos   and    Motors Svo,  *3  co 

Smith,  F.  E.     Handbook  of  General  Instruction  for  Mechanics .  .  .  i2mo,  i  50 

Smith,  G.  C.     Trinitrotoluenes  and  Mono-  and  Dinitrotoluenes,  Their 

Manufacture  and   Properties i2mo,  2  oo 

Smith,  H.  G.    Minerals  and  the  Microscope i2mo,  2  oo 

Smith,  J.  C.     Manufacture  of  Paint Svo,  *5  oo 

Smith,  R.  H.     Principles  of  Machine  Work i2mo, 

—  Advanced  Machine  Work i2mo,  *3  oo 

Smith,   W.     Chemistry   of   Hat    Manufacturing i2mo,  *3  50 

Snell,  F.  D.     Calorimetric  Analysis i2mo    (In   Press.) 

Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings i6mo,  o  75 

Soddy,  F.     Radioactivity Svo    (Reprinting.) 

Solomon,  M.     Electric  Lamps Svo,  2  oo 

Somerscales,  A.  N.     Mechanics  for  Marine  Engineers 121110,  2  50 

Mechanical  and  Marine  Engineering  Science Svo,  *s  oo 

Sothern,  J.  W.     The  Marine  Steam  Turbine Svo,  *i2  50 

-  Verbal  Notes  and  Sketches  for  Marine  Engineers Svo,  *iz  50 

—  Marine  Engine  Indicator  Cards Svo,  4  50 

Sothern,   J.   W.,   and    Sothern,    R. .  M.     Simple   Problems   in   Marine 

Engineering  Design  i2mo,  3  oo 

Souster,  E.  G.  W.  Design  of  Factory  and  Industrial  Buildings. .  .Svo,  4  oo 

Southcombe,  J.  E.  Chemistry  of  the  Oil  Industries Svo,  3  50 

Soxhlet,  D.  H.  Dyeing  and  Staining  Marble Svo,  2  50 

Spangenburg,  L.  Fatigue  of  Metals i6mo,  o  75 

Specht,  G.  J.,  Hardy,  A.  S.,  McMaster,  J.  B.,  and  Walling.  Topographical 

Surveying  i5mo,  o  75 

Spencer,  A.  S.  Design  of  Steel-Framed  Sheds Svo,  *3  50 

Spiegel,  L.  Chemical  Constitution  and  Physiological  Action.  ...  i2mo,  i  25 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG        25 

Sprague,  .  E.   H.     Hydraulics  ...................................  i  zmo,      2  co 

—  Elements   of   Graphic    Statics  ...............................  8vo,      2  co 


—  —  Stability   of   Masonry  .....................................  lamo,  2  oo 

—  Elementary  Mathematics  for  Engineers  ....................  i2mo,  2  oo 

—  Stability    of    Arches  ......................................  i?.mo,  2  oo 

-  Strength  of  Structural  Elements  .......................  ...  12010,  2  oo 

—  Moving  Loads  by  Influence  Lines  and  Other  Methods  ......  i2.mo,  2  oo 

Stahl,  A.  W.     Transmission  of  Power  .........................  i6mo, 

Stahl,  A.  W.,  and  Woods,  A.  T.     Elementary  Mechanism  .......  121110,  *2  oo 

Standage,    H.    C.      Leatherworker9*    Manual  .....................  Svo,  *3  50 

—  Sealing  Waxes,  Wafers,  and   Other  Adhesives  ..............  Svo,  *2  50 

—  Agglutinants  of  All  Kinds  for  All  Purposes  ...............  12010,  3  50 

Stanley,  H.    Practical  Applied  Physics  ...................  (In  Press.) 

Stansbie,  J.  H.     Iron  and  Steel  .................................  Svo,  2  50 

Steadman,  F.  M.     Unit  Photography  ..........................  i2mo,  *2  oo 

Stecher,  G.  E.     Cork.     Its  Origin  and  Industrial  Uses  ..........  i2mo,  i  oo 

Steinheil,  A.,  and   Voit,  E.     Applied  Optics,     Vols.  I.  and  II.     Svo, 

Each,  5  oo 

—  Two    Volumes    .........................  .  .........  .........  Set,  9  oo 

Steinman,  D.  B.     Suspension  Bridges  and  Cantilevers.     (Science  Series 

No.  127.)    ..................................................  o  75 

—  Melan's   Steel   Arches  and   Suspension  Bridges  ..............  Svo,  *3  oo 

Stevens,  A.  B.     Arithmetric  of  Pharmacy  ......................  i2mo,  i  50 

Stevens,  E.  J.     Field  Telephones  and  Telegraphs  ...................  i  20 

Stevens,  H.  P.     Paper  Mill  Chemist  ............................  i6mo,  4  oo 

Stevens,  J.  S.     Theory  of  Measurements  ......................  i2mo,  *i  25 

Stevenson,  J.  L.    Blast-Furnace  Calculations  ............  i2mo,  leather,  2  50 

Stewart,  G.    Modern  Steam  Traps  ...........................     i2mo,  *i  75 

Stiles,  A.     Tables  for  Field  Engineers  .........................  i2mo,  i  oo 

Stodola,  A.     Steam  Turbines  ....................................  Svo,  5  oo 

Stone,  E.  W.     Elements  of  Radiotelegraphy  ..........  i2mo,  fabrikoid,  2  50 

Stone,  H.     The   Timbers   of   Commerce  ........  ..................  Svo,  400 

Stopes,  M.    The  Study  of  Plant  Life  ............................  Svo,  2  oo 

Sudborough,  J.  J.,  and  James,  T.  C.   Practical  Organic  Chemistry  .  tamo,  2  50 

Suf  fling,  E.  R.     Treatise  on  the  Art   of  Glass   Painting  ........  Svo,  *3  50 

Sullivan,  T.  V.,  and  Underwood,  N.    Testing  and  Valuation  of  Build- 

ing and  Engineering  Materials  ....................  (In  Press.) 

Sutherland,  D.  A.    The  Petroleum  Industry  ..........  Svo   (In  Press.) 

Svenson,  C.  L.     Handbook  on  Piping  ............................  Svo,  4  oo 

—  Essentials  of  Drafting  .................  .....................  Svo,  i  75 

—  Mechanical  and  Machine  Drawing  and  Design  .......  (In  Press.) 

Swan,  K.     Patents,  Designs  and  Trade  Marks  ....................  Svo,  2  oo 

Swinburne,  J.,  Wordingham,  C.  H.,  and  Martin,  T.  C.     Electric  Currents. 

i6mo,  o  75 

Swoope,  C.  W.    Lessons  in  Practical  Electricity  ................  i2mo,  *2  oo 

Tailfer,  L.     Bleaching  Linen  and  Cotton  Yarn  and  Fabrics  ......  Svo,  7  oo 

Tate,  J.  S.    Surcharged  and  Different  Forms  of  Retaining-walls.  .i6mo,  o  75 

Taylor,  F.  N.     Small  Water  Supplies  ..........................  i2mo,  *2  50 

—  Masonry  in   Civil   Engineering  ..............................  Svo,  *2  50 

Taylor,  W.  T.    Electric  Cable  Transmission  and  Calculation.  (In  Press.) 

-  Calculation  of  Electric  Conductors  ...............  4to   (In  P,-css.) 

Templeton,  W.    Practical  Mechanic's  Workshop  Companion. 

i2mo,  morocco,  2  oo 

Tenney,  E.  H.     Test  Methods  for  Steam  Power  Plants  ........  i2mo,  3  oo 

Terry,  H.  L.     India  Rubber  and  its  Manufacture.  .Svo    (Reprinting.) 


26       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Thayer,  H.  R.     Structural  Design.     8vo. 

Vol.     I.     Elements  of  Structural  Design 350 

Vol.   II.     Design  of  Simple  Structures 450 

Vol.  III.    Design  of  Advanced  Structures (In  Preparation.) 

—  Foundations  and   Masonry (In   Preparation.) 

Thiess,  J.  B.,  and  Joy,  G.  A.     Toll  Telephone  Practice 8vo,  *3  50 

Thorn,  C.,  and  Jones,  W.  H.     Telegraphic  Connections.. .  .oblong,  i2mo,  i  50 

Thomas,  C.  W.     Paper-makers'  Handbook (In  Press.} 

Thomas,  J.  B.     Strength   of  Ships 8vo,  2  50 

Thomas,   Robt.   G.     Applied   Calculus ..12010,  300 

Thompson,  A.  B.     Oil  Fields  of  Russia 4to,  10  oo 

—  Oil   Field   Development 10  oo 

Thompson,   S.   P.     Dynamo   Electric   Machines i6mo,  o  75 

Thompson,  W.  P.     Handbook  of  Patent  Law  of  All  Countries i6mo,  i  50 


Thomson,*  G.  S.     Milk  and  Cream   Testing i2mo,     *2  25 

—  Modern  Sanitary  Engineering,  House  Drainage,  etc 8vo,     *3  oo 


Cotton    Waste     8vo,  ^  3  50 

—  Cotton  Spinning.     8vo. 

First   Year    *i  50 

Second   Year    "'3  50 

Third    Year    *2  50 

Thurso,  J.  W.     Modem  Turbine  Practice 8vo,  *4  oo 

Tidy,  C.  Meymott.     Treatment  of  Sewage i6mo,  o  75 

rilmans,  J.     Water  Purification  and  Sewage  Disposal 8vo,  2  50 


Titherley,  A.  W.    Laboratory  Course  of  Organic  Chemistry 8vo,  *2  oo 

Tizard,  H.  T.     Indicators (In  Press.} 

Toch,  M.    Chemistry  and  Technology  of  Paints 8vo,  4  50 

Materials  for  Permanent  Painting i2mo,  *2  oo 

Tod,  J.,   and   McGibbon,   W.  C.     Marine   Engineers'   Board   of  Trade 

Examinations    8vo,  *2  oo 

Todd,  J.,  and  Whall,  W.  B.     Practical  Seamanship 8vo,  12  oo 

Townsend,  F.    Alternating  Current  Engineering 8vo,  boards,  *o  75 

Townsend,  J.  S.     lonization  of  Gases  by  Collision 8vo,  *i  25 

Transactions  of  the  American  Institute  of  Chemical  Engineers,    8vo. 

Vol.  I.  to  XI.,  1908-1918 8vo,  each,  6  oo 

Traverse  Tables  i6mo,  o  75 

Treiber,  E.  Foundry  Machinery i2mo,  2  oo 

Trinks,  W.  Governors  and  Governing  of  Prime  Movers 8vo,  3  50 

Trinks,  W.,  and  Housum,  C.  Shaft  Governors i6mo,  o  75 

Trowbridge,  W.  P.  Turbine  Wheels i6mo,  o  75 

Tucker,  J.  H.  A  Manual  of  Sugar  Analysis 8vo,  3  50 

Turnbull,  Jr.,  J.,  and  Robinson,  S.  W.  A  Treatise  on  the  Compound 

Steam-engine  i6mo,  o  75 

Turner,  H.  Worsted  Spinners'  Handbook i2mo,  *3  oo 

Turrill,  S.  M.     Elementary  Course  in  Perspective I2mo,  *i  25 

Twyford,   H.   B.     Purchasing 8vo,  *3  oo 

—  Storing,  Its  Economic  Aspects  and  Proper  Methods 8vo,  3  50 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  27 

Underbill,  C.  R.    Solenoids,  Electromagnets  and  Electromagnetic  Wind- 
ings     i2mo,  3  oo 

Underwood,  N.,  and  Sullivan,   T.  V.     Chemistry  and   Technology  of 

Printing    Inks 8vo,  *3  oo 

Urquhart,  J.  W.     Electro-plating lamo,  2  oo 

Electrotyping I2mo,  2  oo 

Usborne,  P.  O.  G.     Design  of  Simple  Steel  Bridges 8vo,  *4  oo 

Vacher,  F.    Food  Inspector's  Handbook  i2mo, 


Year  Book  of  Mechanical  Engineering  Data (In  Press.) 


Van  Wagenen,  T.  F.     Manual  of  Hydraulic  Mining i6mo,  i  oo 

Vega,  Baron  Vqn.     Logarithmic  Tables 8vo,  2  50 

Vincent,  C.    Ammonia  and  its  Compounds.  Trans,  by  M.  J.  Salter.Syo,  *2  50 

Vincent,  C.     Ammonia  and  its  Compounds 8vo,  2  50 

Virgin,  R.  Z.     Coal  Mine  Management (In  Press.) 

Volk,  C.     Haulage  and  Winding  Appliances 8vo,  *4  oo 

Von  Georgievics,   G.     Chemical  Technology   of   Textile   Fibres ....  8vo, 

— Chemistry  of  Dyestuffs 8vo,     (New  Edition  in  Preparation.) 

Vose,  G.  L.     Graphic  Method  for  Solving  Certain  Questions  in  Arithmetic 

and  Algebra    i6mo,  o  75 

Vosmaer,  A.    Ozone 8vo,  *2  50 

Wabner,  R.    Ventilation  in  Mines 8vo,  5  oo 

v/admore,  T.  M.     Elementary  Chemical  Theory i2mo,  *i  50 

Wagner,   E.     Preserving   Fruits,    Vegetables,    and   Meat i2mo,  *2  50 

Wanner,  H.  E.,  and  Edwards,  H.  W.     Railway  Engineering  Estimates. 

(In  Press.) 

Wagner,  J.  B.     Seasoning  of  Wood 8vo,  3  oo 

Waldram,  P.  J.     Principles  of  Structural  Mechanics i2mo,  400 

Walker,  F.     Dynamo  Building i6mo,  o  75 

Walker,  J.     Organic  Chemistry  for  Students  of  Medicine 8vo,  4  oc 

Walker,  S.  F.     Steam  Boilers,  Engines  and  Turbines 8vo,  3  oo 

—  Refrigeration,  Heating  and  Ventilation  on  Shipboard i2mo,  *2  50 

— • —  Electricity  in  Mining 8vo,  *4  50 

—  Electric    Wiring    and    Fitting 8vo,  2  50 

Wallis-Tayler,  A.  J.     Bearings  and  Lubrication 8vo,  *i  50 

—  Aerial  or  Wire  Ropeways 8vo    (Reprinting.) 

—  Preservation  of  Wood 8vo,  4  oo 

—  Refrigeration,  Cold  Storage  and  Ice  Making 8vo,  5  50 

—  Sugar    Machinery - i2mo,  3  oo 

Walsh,  J.  J.    Chemistry  and  Physics  of  Mining  and  Mine  Ventilation, 

i2mo,  2  50 

Wanklyn,  J.  A.    Water  Analysis i2mo,  2  oo 

Wansbrough,  W.  D.    The  A  B  C  of  the  Differential  Calculus i2mo,  *2  50 

—  Slide  Valves i2mo,  *2  oo 

Waring,  Jr.,  G.  E.     Sanitary  Conditions i6mo,  o  75 

—  Sewerage  and  Land  Drainage *6  oo 

Modern  Methods  of  Sewage  Disposal i2mo,  2  oo 

How  to  Drain  a  House i2mo,  i  25 


28       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Warnes,  A.  R.    Coal  Tar  Distillation 8vo,  *s  o» 

Warren,  F.  D.    Handbook  on  Reinforced  Concrete i2mo,  ::  2  50. 

Watkins,  A.     Photography 8vo,  3  50 

Watson,  E.  P.    Small  Engines  and  Boilers i2mo,  i  25 

Watt,  A.     Electro-plating  and  Electro-refining  of  Metals 8vo,  5  oo 

—  Electro-metallurgy i2mo,  i  oo 

—  Paper-Making    ..8vo,  375 

Leather   Manufacture 8vo,  6  oo 

The  Art  of  Soap  Making 8vo,  4  oo 

Webb,  H.  L.  Guide  to  the  Testing  of  Insulated  Wires  and  Cables.  i2mo,  i  oo 

Wegmann,    Edward.      Conveyance    and    Distribution    of    Water    for 

Water  Supply 8vo,  5  oo 

Weisbach,  J.    A  Manual  of  Theoretical  Mechanics 8vo,  *6  oo 

Weisbach,  J.,  and  Herrmann,  G.     Mechanics  of  Air  Machinery.  ..  .8vo,  *3  75 

Wells,  M.   B.     Steel   Bridge   Designing 8vo,  :  2  50 

Wells,   Robt.     Ornamental   Confectionery i2mo,  3  oo 

Weston,  E.  B.    Loss  of  Head  Due  to  Friction  of  Water  in  Pipes.  .12010,  2  oo 

Wheatley,  0.     Ornamental  Cement  Work 8vo,  *2  25 

Whipple,  S.    An  Elementary  and  Practical  Treatise  on  Bridge  Building. 

8vo,  3  oo 

White,  C.  H.     Methods  of  Metallurgical  Analysis ..i2mo,  250 

White,  G.  F.     Qualitative  Chemical  Analysis i2mo,  140 

White,  G.  T.     Toothed  Gearing i2mo,  *2  oo 

White,  H.  J.     Oil  Tank  Steamers i2mo,  i  50 

Whitelaw,   John.     Surveying 8vo,  4  50 

Whittaker,  C.  M.     The  Application  of  the  Coal  Tar  Dyestuffs .  . .  8vo,  3  oo 

Widmer,  E.  J.     Military  Balloons 8vo,  3  oo 

Wilcox,  R.  M.     Cantilever  Bridges i6mo,  o  75 

Wilda,  H.     Steam  Turbines i2mo,  2  oo 

—  Cranes   and   Hoists i2mo,  2  oo 

Wilkinson,  H.  D.     Submarine  Cable   Laying  and   Repairing 8vo, 

(Reprinting.) 

Williamson,   J.     Surveying Svo,  *3  oo 

Williamson,  R.  S.     Practical  Tables  in  Meteorology  and  Hypsometry, 

4to,  2  50 
Wilson,  F.  J.,  and  Heilbron,  I.  M.     Chemical  Theory  and  Calculations. 

i2mo,  *i  25 

Wilson,  J.  F.     Essentials  of  Electrical  Engineering Svo,  2  50 

Wimperis,  H.  E.     Internal  Combustion  Engine : Svo,  ^3  oo 

—  Application  of  Power  to  Road  Transport i2mo,  *i  50 

—  Primer  of   Internal   Combustion    Engine i2mo,  i  50 

Winchell,  N.  H.,  and  A.  N.     Elements  of  Optical  Mineralogy Svo,  *3  50 

Winslow,  A.     Stadia   Surveying i6mo,  o  75 

Wisser,  Lieut.  J.  P.     Explosive  Materials i6mo, 

—Modern  Gun  Cotton i6mo,  o  75 

Wolff,  C.  E.     Modern  Locomotive  Practice Svo,  *4  20 

Wood,  De  V.     Luminiferous   Aether i6mo,  o  75 

Wood,  J.  K.     Chemistry  of  Dyeing i2mo,  i  oo 

Worden,  E.  C.     The  Nitrocellulose  Industry.     Two  Volumes Svo,  *io  oo 

Technology  of  Cellulose  Esters.     In  10  volumes.     Svo. 

Vol.  VIII.     Cellulose  Acetate.  .                                              *5  oo 


D,  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  29 

Wren,  H.     Organometallic  Compounds  of  Zinc  and  Magnesium.  .12.10.9,  i  oo 

Wright,  A.  C.     Analysis  of  Oils  and  Allied  Substances 8vo,  *$  50 

Wright,  A.  C.     Simple  Method  for  Testing  Painters'  Materials ...  8vo,  2  50 
Wright,  F.   W.     Design   of   a   Condensing   Plant.. i2mo    (Reprinting.) 

Wright,  H.  E.     Handy  Book  for  Brewers 8vo,  *6  oo 

Wright,  J.     Testing,  Fault  Finding,  etc.,  for  Wiremen i6mo,  o  50 

Wright,  T.  W.     Elements  of  Mechanics 8vo,  *2  50 

Wright,  T.  W.,  and  Hayf ord,  J.  F.    Adjustment  of  Observations . . .  8vo,  *3  oo 
Wynne,  W.  E.,  and  Sparagen,  W.     Handbook  of  Engineering  Mathe- 
matics     i2ino,  2  oo 

Yoder,  J.  H.,  and  Wharen,  G.  B.    Locomotive  Valves  and  Valve  Gears, 

8vo,  *s  oo 

Young,  J.  E.     Electrical  Testing  for  Telegraph  Engineers 8vo,  *4  oo 

Young,  R.   B.     The   Banket 8vo,  3  50 

Youngson.     Slide  Valve  and  Valve  Gears 8vo,  3  oo 

Zahner,  R.     Transmission  of:  Power i6mo, 

Zeuner,  A.     Technical  Thermodynamics.     Two  Volumes 8vo,  8  oo 

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Scott,  Y  . 

S43      Standard  methods  of  chem- 
1920     ical  analysis.   2d  ed..- 


